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Chairman's report 2000-2001
Editorial by Mavis Gill
Winter Programme of lectures 2000-2001
Field Trips 2000
Chairman's Report 2002
Winter Programme of lectures 2001-2002
Summer Field Trips 2001
MEMBERS OF THE COMMITTEE 2000-2002
Chairman: Gordon Wilkinson11 Woodside, Ponteland, Newcastle
upon Tyne, NE20 9JA Tel: 01661 824 699
Secretary: Frank Trowbridge 62 The Avenue, Stockton-on-Tees, Cleveland TS19 7EP Tel: 01642 582 786
Treasurer: Ian Johnson 'High Meadows', High Shincliffe, Durham, DH1 2PQ Tel: 0191 386 7455
Programme Secretary: Mike Simmons 9 Stonehaugh Way, Ponteland, Newcastle upon Tyne, NE20 9LX
Field Programme Secretary: Irene Lindsay 26 Kinderton Grove, Norton, Stockton-on-Tees, TS20 1QR Tel: 01642 552 553
Membership Secretary and Report Editor: Mavis Gill 17 High Mill Road, Hamsterley Mill, Rowlands Gill, NE39 1HE Tel: 01207 545 907
Social Secretary: Dorothy Dawson 149 Westbrooke Avenue, Hartlepool, Cleveland, TS25 5HZ
Webmaster: John Waring 12 Epping Close, Marske, Redcar, Cleveland, TS11 6DP
Minutes Secretary and GA Liaison: Joan Hardy 5 Westfield Court, High Barnes, Sunderland, SR4 8RB
Academic Liaison: Dr Gillian Foulger Department of Geological Sciences, University of Durham
Web site address: www.northeast-geolsoc.50megs.com
The turn of the Millennium sees the society in good shape. Our membership remains solid and finances are healthy. Our summer field trip programme arranged by Irene was once again very successful. In addition to a full programme of society events with our usual wide spread of interest, Gilsland, Roseberry Topping, Nidderdale and Tilberthwaite among others, the society arranged a weekend for the Geologists Association which brought visitors from all over the country and provided one new recruit - welcome Joy. This first venture on the national stage was greatly appreciated by the visitors and the GA, and was particularly enhanced by the help from Tony Johnson, Martin Bott and Trevor Bridges who each brought their own insights and knowledge to the event. The dinner was enlivened by the presence of our President, Sir Kingsley, who gave a brief talk afterwards on his own feelings for the area.
Our lecture programme started with Dinosaurs with the enthusiasm of Alistair
Bowden and the fascinating Natural History from Phil Manning. The joint
lecture with the Russell Society was given by Brian Young on the legacy of the
mining industry of the North East. A members night saw a talk on the
Pitus Trees of Dumblar Rigg and a look at the past through some slides of field
trips in earlier times. This year started in Skye with a lecture from
Paul Williams of the OU (how does he get weather like that for his slides?) and
then we moved a little south for the latest view on the Caledonian Orogeny from
Howard Armstrong. This was a real eye-opener and I don't know about you,
but I'm still thinking about it!! Tonight brings a long-standing friend
in Tony Johnson and the subject very close to home.
The society continues to be involved in the wider world of Geology. Chris Lowe is involved with Cleveland RIGS group and your chairman with the Northumberland RIGS group. John Waring, Brian Young and myself are now working on a review of the Type Sites of Northumberland which looks as if it will provide a generation of geologists with field trips.
The society's public presence has been greatly increased by the introduction of a web site through the efforts of John Waring. We can be found at www.northeast-geolsoc.50megs.com. Members with any pictures of society events should let John see them with a view for inclusion in the gallery. Thanks for all your efforts on this and other society activities, John.
We have introduced this year, through the efforts of Mavis Gill an annual report of activities which has been a great success, though hampered in its distribution by IT events of which the secretary will speak more.All in all another successful year and we look forward with confidence and anticipation to the warmer weather and more geology.
We record, with sadness, the death in April 2001 of Sir Kingsley Dunham
FRS, who was our Honorary President. His long life, active as a scholar
and researcher, and also in public affairs, is over. We shall not see him
sitting, shoulders bent, in the front row of the lecture theatre - was he
asleep? - only to hear him ask the speaker some probing question which
demonstrated only too well that his eyes may have been closed, but that his
mind had been very active. Gordon Wilkinson, on behalf of NEGS, attended his
funeral service at the Cathedral.
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I must begin with an apology: this report is greatly overdue. In the year 2000 the first North Eastern Geological Society annual report for the year 1999-2000 was produced in its current form. In many ways it was in response to a perceived need to inform members, especially those who are unable attend our events on a regular basis, of our activities and keep everyone in touch with the Society's proceedings. Most people welcomed its appearance and enjoyed reading it. But in the immortal words of the late Sir Harold Macmillan "events, dear chap, events" intervened, and the following annual report was never produced.
Nevertheless, all of our activities have been dutifully recorded with the intention of bringing them together in subsequent annual reports, and I have faithfully kept copies of all the notes, including those of others who have kindly contributed. They will be pleasantly surprised to see, with the appearance of this report, that their efforts were not in vain.
Last year the committee decided to produce a belated report amalgamating the activities of the two following years, since, due to the restrictions of the foot and mouth epidemic which seriously curtailed our field season in 2001, two separate reports could not be justified. Despite its overdue appearance, it is hoped that this report gives a balanced, though light-hearted, view of events, and will bring back some good memories for those who participated. I would point out that the views expressed in the contributions are the personal views of the authors, and the society would like to apologise to any lecturer or leader who feels that his views were incorrectly represented.
Finally, thanks are due to everyone who so willingly (sometimes with a modicum of persuasion) contributed. We also wish to extend our appreciation to the lecturers and field trip leaders who so generously gave of their time and services for our enjoyment.
I would like to acknowledge the help of Betty Allard, Ruth and Gerry Eastham, Ian Johnson, Ivan Thompson, Frank Trowbridge, John Waring, John Werbiski and Gordon Wilkinson in producing this report.
Mavis Gill, March 2004
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The winter programme of 2000-2001 got off to a lively start with a talk by Alistair Bowden on the Yorkshire Dinosaur Coast Project. Alistair is based at Scarborough Museum (in the famous 'Rotunda') and he kept us well entertained with descriptions of events such as Rockwatch fossil hunts, dinosaur weekends on Teesside and Earth Alert events. But before moving onto the lighter matters of entertaining the public en masse, he opened his talk with an extremely knowledgeable and well-balanced description of the geology of the Yorkshire coast, with some tongue-in-the-cheek references to political boundaries. He illustrated this part of his talk with some very well-chosen slides, including wonderful specimens from the museum, which set the scene for describing the events which followed. We were treated to an amusing and energetic account, with accompanying slides, of the projects which he and his colleagues organised, some of them quite daunting in prospect, such as 180 people turning up for a dinosaur picnic! Clearly, whilst education (though not in schools) is the prime aim of the project, the more serious aspect of conservation was discussed during question time afterwards.
In October Dr Phil Manning of York Museum followed with a similar topic to the previous meeting and gave a stimulating state of the art talk on Dinosaurs - their natural history. We were treated to an impressive display of technology, not only in computing power and animated excerpts from the TV series Walking with Dinosaurs, but also to a wealth of fascinating insights into filming techniques, how the series was made and the models animated. Having whet our appetite with ample footage of dinosaurs trampling the Mesozoic terrain, Dr Manning went on to give the audience technical explanations of a more serious kind! He gave an interesting account of the evolution of dinosaurs, and explained how their well-designed skeletons were honed to engineering perfection to cope with enormous bulk. For instance, skull bones were not fused, thus becoming efficient shock absorbers; sauropods were built along similar lines to suspension bridges; stegosaurs had bony plates laced with blood vessels which were used as giant heat exchange mechanisms for body temperature regulation. Other parts of the physiology, too, showed remarkable adaptation to size: the mechanics of jaw muscles were described in terms of triangulation forces achieving a powerful bite, and the heart evolved into a very efficient pump, eventually leading to the development of four chambers, found in their mammalian and avian descendants. The eventual demise of the dinosaurs was discussed in the context of sudden climatic change, though Dr Manning would not commit himself to specific meteorites and craters. But in the end, these remarkable creatures failed to survive the ensuing climatic change, not because of the cold, but because of their teeth! They simply could not adapt their dentition to pastures new!
November has traditionally become a month when our Society shares a meeting with the Northern Branch of the Russell Society, and an apt account of the impact of the mineral and coalmining industry upon the north-east was given by Brian Young, of the British Geological Survey. His talk, entitled Gone but not Forgotten - the aftermath of mining in north-east England, illustrated the great impact that mining had had upon the region since Roman times, not only bringing dramatic changes to the landscape, but having profoundly influenced almost every area of life in the region, from Weardale to Wearmouth. The essence of the talk was to underline the importance of the knowledge of the most up-to-date geology and mapping in order to deal with the abandonment of the mines. The more obvious problems such as subsidence were dealt with, but Mr Young brought the matter up to date by dealing with this in the context of climatic change, and the effect of heavy rainfall upon old workings. The appearance of a large hole in a field next to Newcastle Airport the previous week was of obvious topical interest! The pumping out of mine water and dealing with mining effluent was given the full treatment, and we heard of some encouraging examples of reed bed systems for cleansing effluent, but also of some disastrous ones where toxic waste still flows unabated. However, we must all be proud of Killhope Mine which now uses the river and old mine workings near Nenthead to obvious cultural and economic advantage! The talk moved on to outline the dangers of gas emissions from old mine workings. We were given several examples of how methane is piped out to safety from old mine workings, including the imaginative design at the Stadium of Light, but we were also told of the incipient dangers from stythe, a gas which is heavier than air, which is forced out by rising flood water within the mines, and can suffocate. Finally, we were given an interesting account of fault reactivation induced by mine abandonment, and some of the salutary experiences which residents of Houghton-le Spring suffered on their property, from creep currently occurring on the Newbottle Fault. After a most interesting and comprehensive lecture we were all convinced of the important role of the geologist in dealing with the aftermath of this region's industrial heritage.
As is customary at our December meeting before everyone gathers for a Christmas buffet and convivial chat in the common room, three members volunteered to present slides of recent activity of a geological nature.
Gordon Wilkinson, our Chairman, gave an erudite presentation on the Pitus Trees of Dumblar Rigg, following a visit to some fossil tree stumps in eastern Cumbria brought to his attention by a friend who has a small farm near Kingswater. Gordon showed some fascinating slides which he had taken of the stumps in the stream near his friend's farm and at another site in the upper Kingwater catchment area. The fascinating story of the pitus trees was first reported by J.B.W.Day in the Memoir of 1970. Ten stumps were found in growth position and varied between two and eight feet tall, and probably grew to a height of over forty feet. They were found in a micaceous flaggy seatearth about 14ft below the Desoglin Limestone of the Middle Border Group and it is clear that they grew up in forests or groves at altitudes low enough for them to be buried in a marginal environment of the Lower Carboniferous Sea.
Following this serious talk, Frank Trowbridge introduced a lighter tone to the evening by showing some slides from the collection of the late Ron Williams. Unfortunately the slides had not been labelled, but many of the longer standing members recognised many of the localities from the trips they had accompanied Ron on, dating back some twenty years! Great hilarity ensued as we struggled to recognise the youthful, slimmer versions of members of the audience, with full heads of hair, sometimes only recognisable by their anoracs and rucksacks which grew more worn over the years!
Finally, at very short notice, Mavis Gill showed a selection of slides reminding everyone of the wonderful weekend spent at Castlehead Field Centre earlier in the year. However, she hastened to add that this would not amount to a geological discourse. But the beautiful scenery and interesting rock formations of the south-eastern Lake District certainly paid testimony to the great weekend which Murray Mackay had organised for us. The short session finished with a few character shots around the interior and exterior of field centre itself, allowing the audience to imagine the former splendour of the now rather delapidated building.
In January we were treated to a very detailed talk by Professor Paul Williams on the Geology of Skye. It was a full and fascinating treatment of the origins of the geology of the island from earliest times to the wonderful landscape as we know it today. The unfolding story was accompanied by a glorious series of slides, showing Skye in perfect weather.
February's lecture was a stimulating and thought provoking lecture entitled The Caledonian Connection by Dr Howard Armstrong. Dr Armstrong delivered a discourse on a re-evaluation which attempts to reconcile many of the outstanding problems of the Caledonian Orogeny in Britain and that proposed for Newfoundland. Dr Armstrong described an orogenic model in which the progressive oblique collision of island arcs from the early Ordovician to mid-Silurian, can be reconstructed from a study of ophiolites in South Mayo, Tyrone and the Ballantrae Complex, which mark major suture zones. A consensus has emerged that the Caledonian Orogen in Britain resulted from microplate accretion and ultimately collision between the stable cratons of Laurentia, Avalonia and Baltica. The intervening period was characterised by the opening and closure of marginal basins and arc rifting events. The orogenic model proposes events during the Grampian Orogeny (the accretion to Laurentia of two arc terranes, the Midland Valley and Novantia with the suture lying along the line of the South Mayo-Highland Border ophiolites that were obducted onto the northern edge of the Midland Valley Terrane) and the accretion of Avalonia, transforming the Laurentian margin into a major zone of sinistral transpression. Until recently evidence of the accretion of Avalonia was poorly exposed in Britain, with difficulties in reconciling the terrane templates of Britain and Newfoundland resulting from the southern thrusting of the Southern Uplands over Novantia.
The last lecture of the winter programme in March, following a speedy AGM,
was a delightful talk given to us by Dr Tony Johnston, an old friend of the
Society. The title - The geology of the Durham Gorge - ensured that
we were on familiar ground, and as he admitted himself, it was a pleasure to
talk about his own back garden. In the last Quaternary glaciation the
River Wear formed a meander over a spur between two river valleys of the River
Browney and the Wear, and later cut down through the bedrock due to isostasy.
The Normans were drawn to Durham because of the geology of the site - the
peninsula was easily defended and consisted of the Low Main Post Sandstone
which proved to be an excellent building stone from which to build the
cathedral and castle. Dr Johnson began by showing us some pictures of St
Oswald's Well and St Cuthbert's Well, both used until this century, which were
replenished from underneath the sandstone. The cathedral is underlain by the
rich Hutton coal seam and Dr Johnson provided us with a lively and personal
view of the mining history of the peninsula, and showed some fascinating slides
of Elvet colliery, which mined the Hutton seam, dating back to the nineteenth
century. Indeed, the peninsula is riddled with old shafts, and we were given a
first-hand account of the detective work undertaken to locate a shaft before
commencing work on constructing St Mary's College. During these
investigations the Prebends Bridge Fault was located, which had previously gone
undetected, because the throw on the fault resulted in one coal seam coinciding
with another! Finally, we were brought up to date on geological events
when we were told about two mud slips which occurred earlier this year,
following the appearance of a new spring near to the East window of the
Cathedral. The Cathedral sits on top of a perched water table in its
sandstone foundations, and the bank behind the west end of the Cathedral near
the Fulling Mill became unstable due to excessive sixteenth century quarrying
of the sandstone. As a result, the south west tower of the Cathedral
needs structural attention
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THE SUMMER FIELD PROGRAMME 2000
Whitby to Saltwick Bay 8th April 2000 Leader: John Waring
The weather was overcast as we gathered at the bottom of the Khyber Pass Steps by the West Pier. We had come to look at the Whitby Mudstone Formation (Lower Jurassic) and the overlying Dogger and Saltwick Formations (Middle Jurassic) between Whitby and Saltwick Bay.
Whilst waiting for the tide to recede to a safe distance, we examined West Cliff, just past West Pier. The cliff section displayed different lithologies, beginning with a coarsening upward sequence of thinly banded sandstones and siltstones. These were crevasse splay deposits resulting from regular flooding events in a plain. Above this sequence lay grey shales passing into a poorly developed coal band, indicating marshland with occasional colonising plants. The Saltwick Formation comprised the top of the sequence, consisting of massive sandstone beds laid down in deltaic conditions, the result of prograding river channels.
We moved onto the beach by West Pier, and here observed evidence of massive channel sandstone cutting down into the crevasse splay deposits of the cliff section. The channel displayed multi-storeyed channel sandstone, as the land subsided due to the weight of the sediment, allowing one channel to be superimposed upon another, both laterally and vertically.
At this point we took the path up from the beach and climbed towards the old town, passing by another sequence of channel sandstones at close range. We speculated on the direction of the current bedding and the manner in which the channels were laid down. We crossed the River Esk, which followed the line of the Whitby fault out to sea. From this vantage point we had both east and west cliffs in view, and John remarked that we should note the contrast in succession of infill of the channels on either side of the fault. The fault had a down throw to the west of 12 metres and had been active in the mid-Jurassic, resulting in the low lying plain to the west being occupied by successive river channels.
After an interesting detour through the sights and smells of the old town, we passed over the bridge and found ourselves on the beach at the base of the east cliffs beneath the light house and coastguard station.
There was now a major change in depositional environment. As we proceeded towards the east pier we noted the thin but prominent layer of the Dogger Formation as it rose from the beach, a narrow band of tough, sideritic sandstone, the beds dipping gently eastwards. The Dogger Formation sits unconformably on the Alum Shale member beneath. We searched among the boulders on the beach, the product of an earlier cliff fall, and came across an up-ended boulder which revealed a layer of pebbles at its base, a conglomerate derived from the Lower Jurassic, proving that the Alum Shales were once aerially exposed and eroded.
We passed over the concrete breakwater underneath the east pier at Gravel Bight, where the cliff recesses, controlled by the strong vertical and horizontal jointing. A cave beneath lent itself for good examination, the tough Dogger Formation forming its roof. The Cement Shales, the highest part of the Whitby Formation, formed the walls of the cave, with its striking white, calcarious nodules. The main Alum Shales were on the floor of the cave, and members of the group found fragments of wood and evidence of the bivalve Dacryomya ovum. The cliffs rose above the Dogger Formation, exposing the Saltwick Formation, though there was no further evidence of the massive channel sandstone, just horizontal flood plain and crevasse splay deposits. John pointed out the Ellerbeck Formation above, a massive sandstone of marine bedding.
As we progressed eastwards, ironstone nodules began to appear in the Alum Shales. Once more the massive sandstone channel cut into the Dogger Formation, which John interpreted as a point bar deposit on the inside of a river bend. We examined some boulders on the beach which had fallen from the cliff, and they clearly contained carbonaceous material, remnants of flotsam which had been ripped off in high energy flood conditions and moved downstream, only to be caught up in the point bar deposits. Another rock fall a little further on also had bits of wood preserved within it, and John thought that these may have belonged to the Whitby Plant Beds.
At this point a shallow syncline brought the Dogger Formation to beach level once more, and it reappeared in the cliff a little further on, with the grey Cement Shales of the Whitby Mudstone Formation underneath. We took a closer look at the a tough, sideritic sandstone of the Dogger Formation, and at its base a conglomeritic layer with pebbles. Examples of this rock had fallen onto the beach, giving us a better opportunity to examine the pebbles, which turned out to be of quartz.
We had now reached Long Bight, and there was much to see, so the consensus was to arrange ourselves over a conveniently placed rock fall and have our lunch, meanwhile examining a dense layer of U-shaped tubes which descended from the Dogger Formation into the grey Cement Shales. The group speculated on their origin for quite a time, and some were of the opinion that the tubes were flat since the burrows would already have been lithified and hard to penetrate. As the rest of us tucked into our sandwiches, Donald's curiosity got the better of him, and he began to explore the rock fall near to the cliff, discarding his tuna and cheese sandwiches for better things. Despite his proximity to the cliff, he rooted around boulders from a rock fall, looking for further traces of the Whitby Plant Bed which John had assured us could be found here. Suddenly he called us all over, and there on top of one of the rocks was the unmistakable three-toed footprint of a dinosaur! It was possible to see how its claws had raked the silt as the animal ran, and before long, having got our eye in, we found other footprints. Soon everyone left their sandwiches behind to join in the excitement. No sooner had we made this discovery, than we fell upon a dark, stained layer with rootlets in another rock nearby - the famous Whitby Plant Beds that we had been looking for in the first place!
Reluctantly we pressed on, crossing the bay, first over the Cement Shales and then the Main Alum Shales, frequently bending over to admire the many belemnites and ammonites (Hildoceras). We rounded the headland into Rail Hole Bight, still in the Main Alum Shales exposed on the shore, and abundant in belemnites. We noted that the approximate east-west strike was parallel to the cliff face. The characteristic jointing due to de-watering was now well exposed at low tide. We continued past another headland, still traversing the Alum Shales, into Jump Down Bite.
Half-way across Jump Down Bite we encountered a double row of nodules crossing the beach in a NW-SE direction and rising up into the cliff in the southernmost corner of the bay. John said that this was known as the Ovatum Band, and is a useful horizon of sideritic nodules marking the boundary between the Alum Shale Member and the underlying Bituminous Shales, the highest member of Mulgrave Shale Member. These shales are harder and darker, signifying a change to deeper, anoxic conditions. They are laminated and there are examples of flattened, pyritised ammonites and iron nodules.
We traversed the beach, across all of the Mulgrave Shale Member, and the familiar cliffs had now receded. Before us lay a headland cut out of a wave-cut platform now exposed at low tide, and covered in barnacles. This was the Top Jet Dogger, an impure limestone reef, criss-crossed by rectangular jointing, and characterised by striking discoidal concretions of up to six feet across and about eighteen inches high, known locally as millstones. They were in sharp contrast to the mudstones and sandstones that we had passed through previously. As the tide was still receding, we were unable to look for the jet workings at the base of the formation, which are only visible at very low tide.
We had now reached Saltwick Bay and the end of our excursion, and we made our way back up the beach to a path leading to the cliff top. To our right, behind the beach, we could see the remains of the large-scale quarrying in the alum shale which flourished from the sixteenth to the nineteenth centuries, now just a vast extent of overgrown heaps of red, burnt shale. As we ascended the path to the top of the cliff, John pointed out traces of boulder clay now covered by grass, the remains of a large, pre-glacial channel.
The sun was now shining as we walked back along the cliff top to Whitby, several of us looking forward to a tempting portion of fish and chips to round off the day.
Roseberry Topping and the Cleveland Dyke 21st May 2000 Leaders: Ruth and Gerry Eastham
This walk commenced and finished at the public car park at the base of Roseberry Topping. Initially following the path through the oak wood, magnificently carpeted with bluebells, to Cliffe Rigg Quarry, the long route of about 6 miles went on to the Great Ayton Cairns above Gribdale Terrace before returning via Great Ayton Moor and Roseberry Topping. A shorter route was available that took in most of the features and allowed more time in the Kings Head for those unable to tackle the long route. The walk was planned around the local geology but also covered the many ways in which the landscape has been exploited over the years.
The central feature throughout this walk was Roseberry Topping, an erosional outlier from the main North York Moors plateau, which appears greater than its 320m height above sea level (215m above the car park). It is capped by the Saltwick Formation and the bench-like features on the scarp slopes are formed by the harder Middle Lias formations.
The whole group walked through Cliffe Rigg Quarry, from which a considerable quantity of Cleveland Dyke has been extracted, and examined the areas of contact metamorphism that remain as sheer walls and pinnacles. The medium grained, porphyritic andesite is one of the swarm of dykes, injected about 59 ma ago, associated with the Tertiary Igneous Complex of Mull. It was worked extensively and much of Leeds was paved with setts from this quarry from 1868 onwards. The line of the dyke was clearly visible from Cliff Rigg and it was possible to look down on to the adjacent Langbaurgh Quarry, so called because it was presumed to be a "long barrow" before the nature of dykes was understood.
Following a stiff walk up the road to Gribdale Terrace the Iron Age Great Ayton Cairns (Scheduled Ancient Monument 873) were eventually located. The main site is about 60 m2, bounded by twin stony earth banks that are separated by a ditch. Finds from the trenching carried out in the 1953 and 1961 are housed in the Dorman Museum, Middlesbrough. Other cairns and associated hut circles can be found in the area.
The party walked along the edge of Great Ayton Moor to the back of Roseberry Topping where it was possible to see the locations from which Alum has been extracted (only 1 ton alum produced from 50 tons of shale), jet has been mined, sandstone has been quarried and ironstone extracted. Ironstone was discovered in the area about 1851, shortly after it had been found on the Eston Hills, but it was not worked here until early in the 20th Century. The partial collapse of Roseberry Topping in 1912 has been attributed, but never proved, to result from the workings in the Main Ironstone Seam under the SE corner of the hill.
Towards the end of the trip members with a reasonable head for heights were able to scramble up the flank of Roseberry Topping to the Thinnfeldia Leaf Bed, a channel fill deposit and the oldest known plant bed in the Middle Jurassic. This is exposed at the base of the Northern face that is formed of Saltwick Formation cross-bedded sandstones and it rests directly on alum shale. It contains examples of Tree Ferns (Nilssonia, Ptilophyllum and Thinnfeldia), Cycad (Zamites) and Horsetail (Equisetites).
Handouts from this walk are still available from the leaders should members wish to follow the route themselves.
Gerry Eastham 9th November 2003
Nidderdale 11th June 2000 Leader: George Crow
(It is with great regret that we record, with sadness, the death of George Crow early this year (2004). He was a staunch member of N.E.G.S. for many years.)
This was relatively off the beaten track for many NEGS members, but the usual enthusiastic crowd gathered at Lofthouse, not far from Pately Bridge to examine the limestones of the late Dinantian and a glimpse of the Millstone Grit group of the overlying Namurian at its northernmost extent in the Central Pennines. Here, the sequence of sandstones and mudstones are much thinner than further south. The Millstone Grit lies unconformably on the limestones, and towards the end of the day we were able to observe, how, further south, the Millstone Grit cut progressively into the limestone, which followed a Yoredale sequence. Here, however, as with the Millstone Grits, though with no association, the sandstones and mudstones beds in the sequence are thinner than further south.
Our first locality took us to a picturesque footbridge just north of the village over the River Nidd whose foundations are formed from the Middle Limestone. We walked up the river following the Middle Limestone, where we were able to examine a shale bed towards the top of the limestone in a small cliff containing small brachiopods and crinoids. Above it the massive Five Yard Limestone outcropped, and we could see cherty beds in the upper part. As people sorted through the pebbles in the river bed, someone found a brachiopod with chert on the back, evidently fallen from the Five Yard Limestone. We proceeded further up the river to a picturesque waterfall over the Five Yard Limestone. We noticed a fallen block with dark chert band with choncoidal fractures. Further up the stream we examined the Three Yard limestone in the bed for traces of green, traces of glauconite, and soon we were successful in mission. At this point we entered the wood where we could see exposures of the lowest beds of the Grassington Grits, a very course, yellow stained rock with many quartz grains.
From here we retraced our steps back to the cars, and made our way to the next fascinating location on the River Nidd at Limley where the base of the Middle Limestone rests on mudstone in the river bed. Here we observed a steep dip in the limestones since we were close to the Limley Anticline. But most spectacular of all, about a hundred yards upstream, the River Nidd simply disappears into a depression in the pebbles in the river bed, known as the Manchester Holes. George led us along the pebbley stream bed to a nearby cave in the cliff where, clinging on to each for safety, we could hear the roar of the water in the extensive underground passages of the Middle Limestone. Close by in the dark limestone we came across a bed of Gigantoproductus in life position, which everyone gets excited because they never fail to impress, such is their size. Across the dry stream bed, Gordon found some standing water by a 2m high cliff, probably trapped. Nearby were some poor quality corals and specimens of Dibunophyllum in pebbles in the river bed.
We rejoined the cars and quickly found a picnic spot by the roadside, whence we could study the landslip on Thrope Edge whilst enjoying our sandwiches. Afterwards, we proceeded to the main car park near the dam belonging to Scar House Reservoir for the final energetic burst of our excursion. We walked past the dam, a major engineering project completed in 1936, and up the hillside to the south of the reservoir. We were now into the Namurian sequence. We found calcareous sandstone beds with fossil traces, probably the Colsterdale Marine Beds, and we spent a considerable amount of time looking for the nodular, ochre-coloured limestone which has weathered. Finally, having precariously negotiated Scar House Gill bed further up the hillside, past dark outcrops of mudstone, finally clambering up a steep bank of shale, probably the Nidderdale Shales. Near the top of the hill we came across a further outcrop of calcareous sandstone. Here we spent more time looking for, and finally convincing ourselves that, the thin band of grey, shaley, poor quality coal, was indeed the Woogill Coal. As we reached the brow of the hill we passed into the very coarse Red Scar Grit. We made our way towards the edge of the cliff overlooking Nidderdale, with a fine view across the valley, our trek was made hazardous by the deep clefts underfoot, hidden by thick vegetation. This is due to cambering effects of rotating blocks of sandstone. Finally we rejoined the steep path to Scar House car park.
NEGS field weekend to Castlehead Field Centre, Grange over Sands 8-9 July 2000 Leader: Murray Mitchell.
Castlehead Field Centre was by now a familiar place to many of us, (especially the webmaster who spent 5 years there during the 1950's) when it was a boarding school!! We luxuriated in the lofty quarters of the main building, complete with Edwardian fittings and quaint balcony, and the impressive dining room with its splendid cornice. After dinner on the first evening Murray gave a brief background to the geology we were going to cover during our week-end. Of particluar significance to our weekend would be the Dinantian limestones of the Carboniferous, and their relationship with the ancient platform of the Lower Paleozoic as the seas gradually advanced across it. Also of significance was the closure of the Iapetus Ocean and the Caledonian plate tectonics, which led to NW faulting, which reactivated later during the Hercynian Orogeny.
The first day's excursion to Yewbarrow allowed us not only to examine the basement sequence of the Carboniferous limestones, but also, as a result of faulting, allowed us to see the relatively deep-water muds of the Bannisdale Slates of the late Silurian. We encountered the main N trending fault at the start of our walk near Catcrag quarry, and this involved a steep scramble into some undergrowth. Although the Bannisdale slates were not visible, the curve of the boundary of the fault was evident along the scarp of the Dalton Beds limestone, baked by the friction of the movement, and visible in the side of the mini cliff. Behind lay the old contour of the shore-line, a mesolithic cliff, when sea levels were higher. Beyond were the salt marshes and marine alluvium.
We walked along the road for a very short distance and then turned north into a beautiful path and onto the Red House Limestone. There was a limestone kiln which in the past had been used neutralise the acid soil of the glacial drift. The Red Hill Oolite is pale grey, without shale partings and open textured, quite pellety in appearance. As such it is host to haematite deposits, formed from circulating low temperature but highly saline fluids. The iron leeched out further up and formed ironstone replacement in parts, forming cone shapes bodies, or sops.
We reached Holywell, and signs of further faulting with evidence of slickensides, where the Red Hill Limestones had faulted out against the Martin Limestone, with an associated quartz vein. We compared the Red Hill Oolite with the fine grained Martin Limestone, which had been deposited much more slowly.
The path now took us in a NW direction, into an ancient woodland complete with anthills and a line of badger sets. We walked along an ancient peatway ditch path, probably more than 300 years old. Shortly we came across the Bannisdale Slates on the sky line, thrown up by the N trending fault we were shortly to cross. We changed direction, now walking SW towards Slate Hill, following a river valley which exploited part of the radial drainage imposed on the Lake District dome in late post-glacial times. We could see the ice-smoothed oval-shaped rocks of the Bannisdale Slates, with its finely graded beds from the rhythmites as the Iapetus Ocean closed.
After a quick lunch, we then took another very pretty path, and past St Paul's church where we were unexpectedly entertained by the village ladies dressed in traditional dress offering us all sorts of goodies. We had stumbled across their village fete! We reluctantly pressed on into more ancient woodland to examine an exposure of the Middle Dalton Beds. Here there were shale partings and a line of springs, and further on a well. As we continued through the wood, with its gnarled trees, we moved onto the Lower Dalton Beds, and below us the paler Red Hill Oolite. The Lower Dalton beds have an important fossil sequence of darker limestone, containing crinoids and brachiopods. We now began to climb a hill where the Upper Dalton Beds formed a scarp as we once more crossed the fault and had a welcome tea break overlooking Nether Hall Farm. There is a spring on the fault line fed by water from the Whitbarrow scarp.
We continued in a westerly direction over the lumpy surface of the Bannisdale slates towards Beck Head and stopped in a field at one point to discuss possible reasons for the missing Martin Limestone at the base of the Carboniferous sequence: was it that as the shore line invaded the uneven surface of the Bannisdale Slates the limestone only filled the hollows, or was it that a fault raised the Martin Limestone and the Red Hill Oolite in the Carboniferous sequence causing them to be eroded away before the Lower Dalton beds were laid? The former scenario is likely, since erosion is a much slower process.
We finished the day much admiring the beautiful gardens of the houses in Beck Head and returned to Castlehead for the usual sumptuous spread laid out in the dining room.
The next morning we assembled at Austwick , ready to tackle the geology of Crummockdale. We set out north from Austwick Town Head almost immediately crossing the North Craven Fault. This is a hinge fault on the southern edge of the Askrigg Block. The Craven Fault was active in Carboniferous times, acting as a hinge and causing the basin to sink and dip gently north east.
We headed north-west through a gate and walked across a field to a low cliff exposure. The base of the cliff is the Kilnsey Limestone, at the base of the Carboniferous. It is a pebbly conglomerate, laid down in a high energy environment from rivers which swept the Lower Paleozoic plain upon which it was laid unconformably. The spring at the base of the of the cliff indicates that the basement underneath is impervious. The basal Kilnsey limestone is dark, and contains reworked debris from the paleo land surface, including quartz pebbles. We spent some time inspecting the cliff and found many items of interest, including corals and brachiopods.
To the north of us lay Nappa Scar, and we gently ascended the path up to the top, where we came upon a spectacular limestone pavement at Norber, dotted with large blocks of sandstone erratics. They are known as the Norber Erratics and present quite a dramatic sight. Many of the giant blocks rest upon tiny pillars of limestone underneath, causing one to marvel at such a fine balance. However, nature's spectacle has enabled geologists to work out the rate of dissolution of the limestone from the time the erratics were plucked by ice during the Quaternary from the Austwick Formation a couple of miles away and dumped on top of the limestone pavement.
Next came the tricky part of the excursion, which was nearly jeopardised due to the presence of a large bull in a field full of cows. We were intending to visit the famous unconformity at Nappa Scar, and not only did this involve walking through the field which the bull presently held domain over, but negotiating a fence culminating in an undignified scramble onto the narrow ledge underneath an overhang in the cliff at Nappa Scar. Finally, after some serious debate (including the bull's pedigree) everyone was persuaded to take a courageous stance and make it as far as the ledge.
As we teetered on the edge of the undercut, nearly bent double to examine the unconformity in rather poor light, we nevertheless marvelled at the remarkable geology, a rare glimpse of an onlap of Carboniferous conglomerate (Norber Formation) on Ordovician calcareous mudstone. Below us we could see a line of springs above the base of the paleo cliff indicating where ground water flow had been diverted over the impermeable Ordovician basement. We carefully extricated ourselves from our uncomfortable perch on the ledge and climbed down, taking the easy route through a field to the top of the paleo cliff at Norber Brow, to admire a feature which has remained virually unchanged since Carboniferous times.
Finally we headed north towards the Crummack Anticline, crossing the Dam House Bridge volcanics on the way (not connected with the Borrowdale Volcanic Group). Looking north west into the plunge of the Studrigg-Studfold Syncline we could see steeply dipping sandstone beds with large joint planes, part of the Austwick Formation, and the source of the erratics which we had encountered earlier on. Thick bedded turbidites formed the northern limb of the syncline, and we walked a little further until the valley of the anticline came fully into view, with its steeply dipping beds. We ventured no further as time was running out, and we had our various journeys to make back home. However, we lingered long enough to take in the breathtaking view which lay before us. There is something awe-inspiring about anticlines when seen on such a large scale.
Nenthead - mine waste water disposal 30th July 2000 Leader: Charlotte Nuttall
Although this was an area familiar to most of us, a large and enthusiastic group of us arrived promptly for what turned out to be a most informative and positive visit in terms of solving some of the problems of the mining discharges left behind after two centuries of mining. The mineralisation of the orefield, due to the underlying granite intrusion of the Alston Block infiltrated by hydrothermal fluids gave rise to rich metalliferous ores leading to intense lead and later zinc mining activity. Even though mining has not taken place in Nenthead for nearly a century, the legacy of metalliferous discharges left behind both from the tailings materials situated along the banks of the River Nent and the waters of the river itself swollen by discharges from six mines have rendered the river toxic to some species of fish, as well as depriving them of food sources due to the pollution.
We started the day by walking upstream to the Grassfield Area level where the red-brown untreated waters flowed from a still well-contructed stone entrance to an adit which connected with Nentsberry Haggs Mine. The brown staining is due to the high levels of iron ochre, which causes loss of the metallophyte flora. Having taken in this depressing scene, we descended partway down the path again to begin the story of the remedial work which is taking place. First of all we were joined by Scott Doherty and his dog Monty from the local environment agency who explained how Cumbria County Council had diverted the river and capped the spoil heaps which had been reworked for zinc as late as the second world war, creating metal rich tailings dams, in order to limit the pollution. Earlier, the council had re-planted the area with mountain ash and bird cherry trees in the hopes of securing the heaps, but although the trees were planted in a plug of soil, their roots soon sprouted out into the surrounding toxic soil full of heavy metals which soon killed the trees.
Charlotte then introduced us to the technicalities of her research work, the anoxic limestone drain (ALD), a cheap and passive method which she is using to reduce the levels of zinc in the River Nent. In the untreated water zinc is well above environmentally recommended standards, and significant discharges from Rampgill and Dowgang mines are a major problem, allowing zinc-tolerant thick green algae to flourish in the summer. Charlotte showed us where the culvert containing the drain had been constructed and explained how its worked. Limestone blocks have been placed in the culvert, and the river water is diverted through the limestone. The naturally slightly acidic water from atmospheric carbon dioxide dissolved to form carbonic acid reacts with the limestone, producing calcite and reducing the acidity of the water. However, if there is no replenishment of atmospheric carbon dioxide, the acidity decreases until equilibrium is reached. As the minewaters are also high in sulphates, which in the presence of zinc also attacks the calcite creating bicarbonate, hydroxide and zinc ions, the acidity of the water is further reduced. This causes the zinc to precipitate out as smithsonite, thus reducing the amount of dissolved zinc. A very clever solution! After three months, the level of zinc in solution was reduced by over 20%.
We descended downstream to the centre of Nenthead where Dowgang Hush joins the River Nent. Here, near the outflow from Rampgill Horse Level Charlotte showed the bright green luxuriant growth of fronds of algae in the stream bed, which in turn chokes other organic matter in the stream. Effluent from a nearby chicken farm also encourages the growth.
After lunch, we paid a visit to the Visitor Centre in Nenthead, and explored the extensive surface reconstruction work on the dry stone walls which had been carried out on the outbuildings associated with the mine workings from Smallcleugh Mine. We then entered a small section of the underground workings, begun in the 1700s, and hewn out of the Great Limestone by pick and shovel,and marvelled at the beautifully constructed dry stone walls which lined the main horse level. Later the mine was taken over by the London Lead Company in 1815 and the extended. This historic monument has now been opened to the public at Carrs Horse Level. As we proceeded underground to a depth of 50 feet the angle of the north-south galena vein in the rock could clearly by seen, and the walls were stained yellow with jarrowsite. Further on, on the wall above our heads, movement on the a fault by the vein gave rise to the distinctive streaks of slickensides. Finally the short route through the underground workings took us up a stepladder into the Great Limestone and along a tunnel which is all that remains of the galena vein which opens out at the waterfall . At this point the iron flats or ankerite which surrounds the vein are further evident from the hot mineralising fluids which circulated through the joints in the Great Limestone, and replacing the surrounding limestone. We came out of the mine into dayalight once more and climbed down to the stream bed which cut through the rock. We had to peer through the ugly stantions which supported a staircase to the mine exit above, to see what remained of the Chaetetes coral layer which marks the base of the Great Limestone. It is unfortunate, to say the least, that what passes as visitor-friendly accessible development defaces and devalues both a site of special geological interest and cheapens the remains of our tough industrial heritage.
On that note, we made our way back to the cars, having had, on the whole, a most interesting and positive day.
THE ALSTON BLOCK
GRANITE. A FIELD WEEKEND FOR THE GEOLOGISTS ASSOCIATION August 2000
(in conjunction with the North Eastern Geological Society)
Visitors gathered at St. Aidan's College, Durham University, on the evening of Friday 4th August and after a meal and a good night's rest gathered in the lecture room on Saturday morning.
Gordon Wilkinson, Chair of the North Eastern Geological Society, welcomed visitors saying that the warm, sunny weather they had brought with them was not necessarily typical of the north! Dr Tony Johnson gave a general introduction to the postulation of the Alston Block Granite by Sir Kingsley Dunham, from field observations of the mineral zonation in the North Pennines. He included some colourful insights into the ensuing drilling process. The surprise discovery of an erosion surface on the granite inferred that the granite was of Caledonian origin rather than Hercynian, as had previously been thought. Professor Martin Bott gave the geophysical background to the discovery of the granite, describing his work with David Masson Smith using gravity measuring instruments now only to be found in museums! The low gravity areas they found fitted remarkably well with the fluorite/barite zonation maps, thus adding geophysical evidence in support of the granite hypothesis.
The group set off for Rookhope, in Weardale, to visit to the Core Store in the Boltsburn Mine Offices. Here Dr Johnson explained in greater detail the nature of the core and showed some of the machinery used in its study. Afterwards, the guests were able to spend some time examining the core, and the morning session concluded with a visit to the nearby site of the borehole, now sealed.
After lunch Trevor Bridges, of the Russell Society, took the group to the Pike Law, an exposed site in the North Pennines, pointing out that this was the first time he could remember being able to remove his fleece! The aim of the visit was to demonstrate the sharp boundary between the fluorite and barite mineralisation zones, which had allowed Sir Kingsley Dunham to show the zonation on a map and thus postulate the presence of the granite. The group explored one of the many hushes in the area and discussed its origin in the context of early mining practices. So far the gangue mineral had been fluorite, but shortly, as we made our way towards Flushiemere Beck, we moved into the barite zone. We retraced our steps, and some interested members of the party examined the fauna in the outcrops of the Great Limestone en route. Finally, we visited a favourite hush of Trevor's, to the west of the previous one, and looked at minerals showing secondary mineralisation.
We were fortunate enough to be joined at dinner by Professor Martin Bott and Sir Kingsley Dunham, who, although resident in a nursing home, was able to be present. Sir Kingsley was delighted to find Dr Harold Reading, one of his early research students, among the guests, and their dinner was enlivened by tales of times gone by. After dinner, Sir Kingsley welcomed the GA to Durham for, he thought, the third time, although he was not sure whether they had sneaked in on one occasion whilst he was away in the south during his stint with the Geological Survey! He spoke about his memories of the granite and Boltsburn Mine, stating that his secret hope would be that in different economic circumstances it might become viable again. He then introduced professor Martin Bott, who gave an in-depth review of the gravimetric studies and his current work on the isostatic level changes due to the lower density of the granite include his current thinking.
On Sunday morning, still in glorious weather, the party visited Harehope Quarry at Frosterley to view the Great Limestone and the famous Frosterley Band of coralliferous limestone, used as decorative building stone in many locations, including Durham Cathedral. The coral dibunophyllum bipartum could be seen both in situ and in many fractured pieces in the quarry bottom. In addition, productids were found and several examples of Zoophycos, much to the pleasure of the party. The group lunched at the quarry and was joined by Brian Young, the regional geologist, and his wife who were initially separated from the rest by barbed wire! Having studied the Weardale granite from every aspect, members of the group concluded their week-end by a visit to Middlehope Burn near Westgate, to look at the Carboniferous Yoredale Cyclothems which lie above the granite. The group was led by Mavis Gill and Donald Vaughan (from NEGS) and followed the sequence of waterfalls up Middlehope Burn, a most delightful locality, and famed for its flora (it has been designated a botanical SSSI). The rocks in the stream bed and along the banks were examined, and the repetitive sequence of limestone followed by sandstone noted, each sequence being known as a cyclothem, resulting from repeated marine transgressions and alternate deltaic conditions during Brigantian times. The afternoon ended in contrasting mode, and once again under the influence of the mineralisation of Weardale granite, as the group explored the extensive mine workings of Slitt Vein and the impressive industrial monument, now designated an SSSI, of West Rigg Opencut mine.
Visit to Gilsland Gorge, 20th August 2000. Leader: Gordon Wilkinson
We met at the Gilsland Spa Hotel and descended to the bottom of the gorge, where a few brave souls tried the spa water. We are pleased to report that they were still with us at the end of the trip and are alive to tell the tale! We stood on the bridge overlooking the River Irthing whilst Gordon introduced us to the local geology. The gorge forms part of the Upper Border Group in the Lower Carboniferous. The area is transitional between the predominantly marine lithology to the west near Bewcastle and the generally non-marine of the Scremerston Coal Group around Kielder. In this area cyclic variation produces frequent massive sandstones separated by shales and thin, detrital limestones. Thin coals together with seatearths also occur. The precipitous gorge, situated at the west end of the Ninety Fathom/Stubblick fault system, follows a group of five NW-SE trending faults in a horst and graben arrangement. As we contemplated the fast flowing river beneath us, we noted its peaty brown colour, and the strong smell of sulphur. The Crammel Linn Sandstone formed the bed of the river, which overlay the Miller Hill Limestone.
Passing along the along the spectacular gorge, we noted that the bank opposite was sandstone, dipping gently north east, with the Green Grove Sandstone overlying it in the cliff face. At a major bend din the river the sandstone began to break up, and we noticed limestone clasts in the stream bed. We were now in the vicinity of one of the five sub parallel faults which coalesce to the south east to form the Blenkinsop Fault. Presently in the cliff, we noticed the Miller Hill Limestone to the north, and the Popping Stone Sandstone to the south. This inferred a fault, but the boundary between the two was obscured by trees and other vegetation. Repeated exposures of the succession were evidence of further faulting. We walked as far as the eponymous Popping Stone, a large rounded block of sandstone forming the nose of the river bend. It is large, prominent, and multi-lobed, whose shape and name have given rise to various lurid suggestions. The more agile members of the group clambered onto it, though it was fiendishly slippery, and the fast flowing river formed menacing eddies as it rounded the bend towards the waterfall. We retraced our steps and left the gorge behind, following a delightful woodland walk back to the cars.
We relocated to the moors for lunch, and then undertook the second part of the day's programme. We walked across the moor to a steep bank formed from glacial till, which had repeatedly slumped down, making access to the river difficult. We walked a little further along to the waterfall where there was an exposure of the Crammel Linn Sandstone, and in the bank opposite the Green Grove and Collering sandstones could clearly be seen. The Blenkinsop Fault system had given rise to the beautiful 40ft Crammel Linn waterfall. We noted that there had been significant erosion of the waterfall back from the fault line.
Making our way back to the cars we moved further upstream to the north bank
near Forster's Hill. Here, in the banks of a small tributary of the
Irthing we were able to find traces of the Throssburnfoot Coal just underneath
the Spy Rigg Sandstone. Moving a short distance downstream we observed
two tholeiitic dykes which caused some local baking and cleavage of the
shales. Looking across the river we could observe the well developed Spy
Rigg Sandstone affected by a series of small faults.
We returned to the cars and thanked Gordon for a most interesting trip in an area unfamiliar to most of us.
The mineralisation at Tilberthwaite 1st Oct 2000 Leader: Brian Young
This was a joint meeting with Leeds Geological Society held in the Lake District, though not many NEGS members attended. The walk would take us up the Tilberthwaite Gill onto Birk Fell, which separated us from the Langdale Valley. We were located in the southern part of the Borrowdale Volcanic Group (BVG), with complex mineralisation and underpinned by the Eskdale Granite and Ennerdale Granophyre. The minerals were deposited by high temperature fluids circulating through the veins and fractures of the rocks as a result of the BVG and the emplacement of the granites.
Although the copper mineralisation of Tilberthwaite had never been studied in detail, it bears many similarities to the Coniston area, once the centre of a major copper producing area, nearby to the south west. In common with Coniston, smaller amounts of lead, zinc and other minerals are also found, which formed later.
The aim of the field trip was to introduce us to the varying conditions in which the minerals were formed, leading to contrasting assemblages.
As we made our way up the hillside past Tilberthwaite Gill towards Birk Fell Hawse, we passed a slate quarry which disfigured the hillside, and adits driven in for galena and sphalerite, evidence of the later carbonate mineralisation. The copper-bearing north vein of Tilberthwaite appeared as a gash up the valley and hillside, with its associated spoil heaps. Pyrite was ubiquitous, appearing as yellow smears on the rock.
As in Copper Mines Valley, we found evidence of unusual assemblages of quartz with magnetite, which has replaced the haematite. This assemblage is usually associated with an active volcanic setting, thus posing the question of the age of the veins, and whether they are related to volcanic emplacement. Brian told us that recent work carried out by Dave Milward and himself in old mine workings under Levers Water proved that cleavage in the wall rock was refracted into the vein and back in the wall rock, proving that the veins were emplaced before regional cleavage. Here the veins contain brecciated wall rock with sulphides in the small veins. There are few secondary copper minerals, mainly sulphides from below the oxidised zone.
We examined the workings of Helen's Mine, where we found some copper minerals, and significant amounts of black sphalerite, and an alteration reaction between the sulphides of copper with chalcopyrite.
We scrambled up to the ridge of Birk Fell, and were rewarded with a
panoramaic view to the north and west, ranging from the Langdale Pikes to
Scafell in the distance. Having spent some time taking in the view, Brian
pointed out that the mineral assemblage here is different. Quartz is the
first mineral in the veins, followed by specular haematite converted to
magnetite. However, parts of the vein showed evidence of white quartz
with curved specular haematite, thus in the early phase of
mineralisation. Where the vein was exposed it was observed that the
cleavage was the same as at Coniston, and there was quartz to be seen in
ptigmatic folding. Copper mineralisation followed, with bismuth and arsenic
compounds, though still dated as pre-cleavage. Further down the hill we
came across examples of bornite, a brown/bronze coloured mineral, rich in
copper. It has an unstable surface and easily tarnishes to a mixture of
reds and blues. Bornite is associated with a zone of secondary
enrichment: the weathering copper reacts with the ground water and goes into
solution, and reacts with other sulphides, replacing the chalcopyrite by
bornite. If carbonates are present, azurite and malachite result. We
could see that the chalcopyrite and bornite were at high levels, proving that
there was a zone of enrichment here.
It had been a most enlightening day amidst spectacular scenery in the heart of the Lake District, and as we walked down the hill back to the cars, we examined the old mine workings of Helen's Mine with a greater understanding of the processes behind the formation of the minerals.
The year 2001 - 2002 was a tumultuous one for the society. The year had scarcely begun when we heard of the death of our President, Sir Kingsley Dunham. His patrician figure on the front row at lectures, with the inevitable penetrating question to keep our speakers on their toes, will be missed.
We were aware that our field trip season was going to be restricted by virtue of the Foot and Mouth epidemic and the coast became our refuge. Thanks to all who organised the trips and special thanks to Mavis for taking over Scremerston after your chairman's back went on strike again. In regard to field trips we must record our grateful thanks to Irene who has handed over the reins of field trip organisation to Jonathan Allinson. We will all have our own memories of favourite field trips, but my memories of Irene at work are of her mugging lecturers after the vote of thanks to get them to take us to see the places spoken of. Thanks a million Irene.
We have had another excellent season of stimulating lectures organised by Mike which looks like going out on a warm note tonight. All the lectures have had an excellent turnout - our number of attendees to total members is the envy of many of our neighbouring societies.
After the lecture there will be a buffet, unusually, not provided by Dorothy and Co. However we thank Dorothy looking after the inner man for the rest of the year and Christine, Irene and Frank for proving excellent substitutes. It's all that watching Ready, Steady, Cook whilst his knee got better!!
My thanks go to the members of the committee who have all put in a lot of work once again to keep the wheels turning through a tough year. Let us hope for good field trips this summer and another successful year.
Our winter season began with our September talk by Professor Roger Searle entitled "How do the plates grow? Imaging the ocean floor". We commence with slides of the now familiar world maps which show the topography and age of the sea floor. These demonstrate the volcanoes that rim the Pacific Ocean, the ocean ridges and the plate boundaries. This led to a brief introduction to the theory of plate tectonics, with its mid-ocean ridges and subduction zones. A picture of a black smoker, which derives its energy from an adjacent hot magma chamber, led to a more detailed consideration of what happens at a spreading ocean ridge. What is the sequence of events? To answer these questions, a much more detailed picture of the sea floor adjacent to the ridge is required. Professor Searle described the developments in under-sea surveying tools, of which sonar had been most important. In 1861 the US Hydrographic Survey had carried out a series of soundings of the Atlantic Ocean, and recognised the presence of the raised sea floor in the centre. In the 1960s, a century later, sonar soundings obtained by towing a sonar source and detectors (GLORIA) behind a ship, had mapped the sea bed to a 10km definition, and had clearly defined the central ridge. And a towing magnetometer across the ridge produced a pattern of parallel stripes, where black and white are used to illustrate polarity of the magnetism. This was explained by the spreading ridge, when newly extruded basalt took up the magnetic direction at the time of formation, with approximately equal widths on either side of the central fissure. By linking the stripe pattern with periodic changes in the Earth's magnetic field, the age of the ocean floor could be obtained. This showed that the oldest extant ocean floor is of Jurassic age - any older material has been subducted.
In 1991, a more detailed survey was possible, using a submerged sonar source/receiver (TOBI) towed about 100m above the sea bed. These results, allied to improvements in computer data processing, produced detailed maps and 3-D images, now to a definition of 100m. Another tool, the measurement of the sea surface topography by means of satellite radar, can also show the presence of the spreading ridge.
These sonar soundings established the structure of a spreading ridge with a median rift valley, with the ridge broken by numerous transform faults. On each side of the ridge are a series of fracture zones with fault scarps, approximately 2km apart. It is believed that the newly formed sea floor is under tension and begins to break apart soon after formation. When ocean ridges are joined, as in the Pacific Ocean, more complicated structures are present. In one example, a small area of plate had been rotated through some 90o. Finally we were shown some video pictures taken by Professor Searle and other research workers, from a Japanese manned submersible, equipped with a sampling arm and thermal probes. This had travelled from the almost flat abyssal plain into an area of pillow lavas. In reply to a question, Professor Searle said that the ultimate driving force for plate movement was mantle convection cells, but that once plates were moving, gravitational pull on subducted plates also had an effect.
In October Dougal Jenam talked to us on The evolution of flood basalts at volcanic rifted margins. Dr Jenam described work which he was carrying out on flood basalts of Ettendekke in the Namibian desert, which had erupted at the beginning of the Cretaceous onto massive aeolian sand dunes, preserving fine detail of their structure. The lack of vegetation allowed the arcuate shape of the barkan dunes to be observed, and fine details of the ridge and crest features with bifurcating ripples on the top set beds can be seen alongside the ropey texture of the lava. The basalts had erupted during the break up of Gondwanaland, which may have been a precursor to the mass extinction. A gas province has been discovered offshore, and the oil industry is interested in investigating the porosity of the sand dunes preserved under lava, to see whether they are oil or gas bearing. Dr Jenam talked about modelling the crystal packing density known as the R-value, or Randon Spherical Distribution Line, the spatial distance of the crystals one from one another. This technique had been borrowed from biological modelling. Most of us nearly followed him as he moved into the province of 3D modelling, and the distinction between ordered and clustered packing with respect to a rock's porosity. Clustering took place during fairly rapid cooling and crystal overgrowth, whereas random crystal growth gave rise to an ordered crystal framework yielding greater strength and lower porosity. Dr Jenam attempted to relate the packing value and hence jointing of the basalt not only to the rate of cooling but also to the speed of flow of the over sand. It was found that the collonades in the classic columnar joints had a touching framework which was frozen in situ. The aeolian sand preserved by the basalt also underwent physical compaction, and crystal overgrowth during the latter stages of compaction. In both these rock types, considerable local variation in packing density was observed within the same lava flow and in the sands interleaved between repeated lava flows. Finally, satellite images are used to survey the land and to reconstruct a three-dimensional geometrical image of the surface, so that the key features can be picked out and packing density applied.
Our joint meeting with the Russell Society in November brought a welcome visit with old connections. Dr Jonathan Larwood, whose father had helped steer NEGS through its early independent days came to talk to a well-attended audience on the conservation work of English Nature entitled The past is the key to the future. It was a fascinating view into what goes on behind the scenes, including some interesting insights into the politics. England has some of the most varied geology in the world for its small size, and, due to the pioneering work done by William Smith in the early eighteenth century, we have developed the science of recording the geology around us and understanding the processes. Dr Larwood posited four fundamental questions which guide the philosophy of English Nature: why are we conserving landscape, who are we doing it for, where and what do we conserve? It can be very quickly established that education and research are of paramount importance. We were given a short history of the last half century, dating back to the beginnings of geological conservation in 1947, the establishing of SSSIs, the developing of RIGGS (Regionally Interesting Geological and Geomorphological Sites) and the implications of the Countryside Act and the 'right to roam'. Dr Larwood described the rigorous process of documentation required in order to designate a site as an SSSI. Once a site has been designated there is the ongoing cost of managing the site, not just from the excesses of man who mines and tips all manner of things near to sensitive sites, but also from the awful power of wave action and other damaging climatic effects. Politics and policies play a large role in this aspect of conservation. Finally, Dr Larwood ended his talk by saying that uniformitarianism was the key to the work of English Nature, and that we should learn from the past, enjoy the present and use the discovery of dynamics to control future changes.
December once again gave the audience a flavour of the geological experiences of three members again volunteered to talk about their trips to foreign parts over the course of the last year for Members' Night.
Ivan Thompson treated us to a detailed geological explanation of the geology of New Zealand with the aid of overheads, accompanied by some terrific pictures designed to make even the most reluctant of members want to go, despite the hazards of long-haul flights. We were given a detailed explanation from the time it was a submerged part of the continental shelf of Gondwanaland. 100 million years ago it was uplifted, and 80 million years ago plate movement resulted in it becoming an island. Some 30 million years ago a new plate boundary developed, cutting right through the New Zealand sub-continent, and, amid a plethora of plate movement and volcanic activity modern New Zealand began to develop along both sides of the plate boundary. This runs along the Great Alpine Fault in South Island, continues undersea southwards, and along the Hihurangi and Kermadec trenches to the east of North Island. There is slipping movement but no subduction in South Island, and therefore little volcanic activity. Among the slides he showed us, we saw some of the deposits on the ancient greywacke base, including the sand dunes in Northland, Rangitoto volcano in Hauraki Bay, and the 'Pancake' formation on the west of South Island. Certainly a place to visit!
Frank Trowbridge and Mavis Gill both chose to talk about their visits (on separate occasions) to Iceland. In his talk Frank Trowbridge concentrated on the rifting Atlantic Ridge which crosses Iceland roughly north north east to south south west, and the effect that constant tectonic activity and vulcanicity has had upon the landscape. We saw some stunning views of the glacier landscape set in stark contrast with the black basalt flows, and the rugged saw-toothed ridges of the volcanoes where they had once erupted under ice. Iceland has some of the most spectacular waterfalls in Europe, which rival the Niagara Falls in sheer volume of water, and Frank showed us some superb slides of these. Iceland is never complete without mentioning its association with geysers - after all it gave the world their name - and Frank showed us a picture of an heroic attempt to snap Strokkur at its maximum height (from a distance)!
Mavis Gill concentrated on the changes to the landscape in Iceland during the thousand or so years of human habitation, since the Vikings settled there. Life is a constant struggle against the forces of nature in this land of fire and ice, and time and again its people have had to adapt and relocate in the face of insurmountable difficulties and subsistence agriculture on thin soil in a harsh climate. The talk included slides of volcanic flows which had dislocated precious agricultural land, including the famous Lakki fissure eruption of 1783, whose noxious gases poisoned much of the land. Nearly as catastrophic in recent times was the volcanic eruption under Vatnajokull in 1996 which caused part of the largest glacier in Europe to melt, adding millions of tons of outwash onto the coastal plain or sandur and adding 4 km to the coastline. The connecting coastal road was completely washed away, thus severely disrupting communications to the eastern part of the country. A new road has now been constructed, and Mavis showed a slide of the new bridge, a mile long, across the braided streams which still flow fast from the glacier. Despite the presence of vast glaciers and waterfalls, parts of Iceland qualify as a 'cold desert' in the shadow of the central volcanoes, and there was a beautiful slide depicting the volcano Breida mekur standing proud in a flat, black dusty desert of volcanic ash and tuff. Finally, not to be outdone by Frank, Mavis showed a slide of the geyser Strokkur, this time featuring the blue dome which rises just seconds before the geyser erupts. Surely there is more skill attached to obtaining this picture!
The January meeting provided us with a most interesting talk on Geological Mapping by Brian Young. Brian began by telling us to dispense with the notion that geological maps are factual! They are not, but are subjective interpretations based on scant evidence. Out in the field clues as to what lies underneath us is based on the odd rock outcrop, the rest being covered by 'gardening' (soil and drift) - as he put it to us! The most reliable maps are based on evidence from boreholes. The British Geological Survey has a huge archive of information, since all boreholes that are drilled must be notified by law. All information derived from road building schemes, bridges and building is put together, and it requires complex geometry to work out the accurate groupings of solid rocks. The smoother the line on the map, the fewer the data points and hence the greater the uncertainty of the interpretation. The chronological events which lead to lithostratigraphical record are a matter of subjective interpretation, and are likely to be refined as our knowledge of geological processes advances. The earliest maps describing the countryside were drawn by William Smith at the turn of the nineteenth century, and were the result of a huge amount of time and effort as he went around the country on horseback. Later on, Peach and Horne worked on mapping the Assynt area, and are reputedly supposed to have suffered nightmares whilst interpreting the geological history and the plate tectonics of the Moine Thrust! Geological maps are an essential part of the modern world, and are produced on many scales and represent many aspects of earth science, from mineral resources to gravity and magnetic anomalies. Thanks to satellite and marine surveying, whole continents and ocean floors are now mapped, contour lines being constructed to predict where seams and outcrops of rocks occur. Their uses range from modern engineering projects to mining and landfill purposes, not to mention water resources. At the end of the lecture, Brian Young invited everyone to come and look at some maps he had brought with him, including some very interesting historical ones.
In February everyone prepared themselves to hear Dr Stuart Jones talk to us on Alluvial Fans and Sediment Supply, but instead we were given a comprehensive treatise on river profiles and the effect that controls such as climate, sea-level and tectonic changes had upon local drainage. Particular examples were given of the drainage patterns in the Pyrenees and the Panonian Plain in Hungary, and how they were affected by tectonic events in the Miocene and Pleistocene. The history of these events has been reconstructed using a combined study of drainage and sedimentation patterns. Structural events such as mountain building have a fundamental influence on drainage patterns, and at times of active uplift rivers flow straight down the mountain range and into the basin. Where there is a more moderate uplift or subsidence, rivers flow axially and parallel to the mountain range. Dr Jones than gave a detailed account of river profiling, how rivers start life in an erosive, deeply incising, high energy phase as they flow down the sides of mountains. The river course gradually becomes shallower and moves towards an aggradation phase as more sediment is carried and deposited further down stream. Dr Jones went on to explain how this knowledge can be applied to build up the geomorphological history of a region. At a macro level the changes in drainage patterns can be examined to identify the younger streams as they cut through older, antecedent river beds. Further extensive analysis of the fluvio-deltaic deposits in drainage basins allows one to obtain a picture of the climate, the hydraulics and the origin of the sediments brought down by the rivers. At the end of his lecture, Dr Jones explained that the present day N-S drainage of the Pyrenees occurred during the last 5 million years due to the E-W lineament of thrusts and anticlines of the Alpine orogenic belt. Similarly, the history of the structural complexity of the Panonian Basin in Hungary was reconstructed using fluvio-deltaic record. The Carpathian Mountains, also an Alpine orogenic event, slowly uplifted during their first phase and later became more active, causing rivers to change from an axial flow pattern to a traverse one, with different sediment supply.
Following the AGM in March, Dr Eric Johnson gave a very well-illustrated talk on Hawaiian Volcanoes. The Earth's largest volcano, Mauna Loa, is found on Hawaii. The islands which comprise Hawaii are formed from the basalts which upwell from the hot spot formed by a mantle plume which lies beneath Hawaii. The hot spot lies more than 250 miles from the margin of the Pacific Plate and has been active since the late Cretaceous. It is gradually drifting south east underneath the plate, leaving a trail of volcanic islands and sea mounts in its wake. The present-day island of Hawaii is formed from five volcanic centres which have coalesced. Mauna Loa, 4,000m above sea-level rises a further 5,000m from the sea floor in the Pacific Ocean, making it taller than Mount Everest in real terms. Kilauea is the most active volcano and has a deep caldera with a 5,000m rim. Due to the doming of the shield volcano, rifting occurs, and folklore says that the volcano is controlled by the goddess Pele. Dr Johnson illustrated some of the main surface features of different types of lava, including pahoe-hoe lava with its smoothed and curved ripples, and aa-aa lava, where the lava crusts over and then breaks up due to further movement within the flow. On a larger scale, we saw braided flows as the basalt lava flowed across a plain with very little topography. We saw pictures of fault scarps within lava, lots of pictures of lava tubes exposed to the air, lava pillars formed from tree trunks carried along by the lava, fountaining lava from rifting, jets of lava flowing through tubes which empty into a boiling sea. Several members remarked later that these pictures were rather Turneresque or reminiscent of the early works of Denby! Some of the volcanoes are 'friendly' ones and allow tourists to stand close by and take wonderful pictures of active spatter cones throwing showers of molten lava into the air. Other eruptions have a more sinister effect upon the landscape and communications of the island. To close his lecture, Dr Johnson showed us pictures of cars and houses engulfed by lava, roads completely blocked by lava flows, and the stark outline of forests of bare trees, some still on fire, their foliage scorched by the heat from the lava which now formed the forest floor.
The Geology of the Wear Gorge 18 May 2001. Leader: Dr Tony Johnson
At the height of the Foot and Mouth Epidemic in May 2001 Dr Tony Johnson, who had lectured to us so enthusiastically about the geology and mining history of the Durham Peninsula only three months before, agreed to lead a field trip along the banks of the Wear Gorge. And we were not disappointed. As the day unfolded we began to understand the complex relationship of the Coal Measures and the fortuitous positioning of the Cathedral and Castle on them, where they are exposed on steep banks as the River Wear cut a deep incised meander forming a gorge between Elvet Bridge and Framwellgate Bridge. The day was made all the more interesting by Dr Johnson's evident interest in local history. The Cathedral dates back to the 10th century when monks from Lindisfarne, carrying the remains of St Cuthbert in the wake of a raid by the Danes on their own priory, were searching for a site to build a shrine to his memory. A wheel came off their cart whilst they were passing through the area, and whilst they were repairing it the monks came across a milkmaid milking a dun cow. She said that this place was called Dunholm, and realising that they had found the best defensive site in the north of England, the Saxons built a wooden church to St Cuthbert to protect his remains. But it was the Normans who built Durham Castle and replaced the church with the present Cathedral laying the foundation stone1093.
We began our walk at the Science Campus of Durham University, where Dr Johnson led us to the place where main drawing shaft section is of Old Elvet Colliery, opened in 1830, is now concealed. The Main Hutton Coal Seam lay 180 ft below us, and there were six shafts. The seam was first worked to the east, then to the west, and finally worked underneath Crossgate until 1908, when the small private colliery went into liquidation. Indeed, the gable end of the nearby house had suffered damage from subsidence as a result of the mine workings, but no compensation was ever paid. Whilst researching the history of the colliery Dr Johnson had talked to a lady whose family had worked in the colliery, and she told him that the miners brought the coal up to the surface and wheeled the waste back, hence leaving no tip in the vicinity. The main engine shaft was cut through the full succession of coal measures. A book of records was kept of the borings and sinkings, and eleven in all were carried out by Arthur Holmes in order to map the general succession.
We proceeded through St. Oswald's cemetery and stopped to examine some gravestones on the way. One was carved from granodiorite, whilst another, of origin unknown, was of a beautiful polished black limestone, and highly fossiliferous. We spent quite some time identifying the brachiopods, corals, and giant productids. Another gravestone, dating back to 1799, proved to be very interesting since it contained siliceous concretions in the form of black chert which had weathered out from the limestone. They still had a polished appearance, and stood proud of the limestone by 2 mm, proving that weathering attacked the limestone at the rate of 1 mm per century in these parts!
From the cemetery we followed a path to the gorge on the left side of the River Wear, and remarked on the steep drop to the river below as it swirled round the peninsula facing us. Though it is not such good building stone, the Low Main Sandstone, which forms the lip of the gorge, has been quarried producing the stone for the Cathedral, producing the flatter areas on either side of the river. The sloping, wooded sides of the gorge are the result of dumped material to support the cathedral foundations, especially at the western end, which we visited towards the end of our walk.
On our left was a steepening cliff of Low Main Sandstone, though not the result of quarrying because of our proximity to the Durham Main Fault which runs N-S, and has a downthrow to the east of 15 feet. Not far to the west was the Prebends Bridge fault. We followed the path south to St Oswald's Well, hollowed out in the base of Low Main Sandstone, with a coal seam and shales visible underneath. The spring, one of a series at the base of the sandstone, runs into a clay-lined basin with an iron bar in front, and provided water for the Parish of St Oswald's. One would hesitate to use it now, since there is evidence that the clay basin is encircled by lead.
We continued along the path, noting the line of springs on the right in the gorge beneath us, marking the base of the Low Main Sandstone. Shortly we came across a man-made gulley with a bridge made of boxed chain sandstone slabs which marks a drainage channel from the main pumping shaft of Elvet Colliery. Recently, the Dean and Chapter of the Cathedral, whose responsibility it is to preserve the banks of the gorge, minuted that smoke had been noticed coming from the shaft, and it has recently been capped.
Here the steep cliff on our left of Low Main Sandstone displays strong cross-bedding, but just past this point the slope of the cliff reduces, indicating the position of the Durham Main Fault, with the shales of the Brass Thill Seam now appearing, 15 feet further down in the sequence. The path bears right, and the Low Main Sandstone, now beneath us, has been quarried extensively below.
We are moving into a boggy area, a feature of the glacio-fluvial geology representing the buried valley of the River Browney. The path continues back on top of the Low Main Sandstone to a rubbly area, remnants of the slag from the coal used to power the steam engine boiler serving as a pumping station for the Hutton Coal. A low, circular wall can be seen, all that is left of the tower which was once the air shaft for Elvet Colliery workings, recently dismantled by the Coal Board since it had become a repository for rubbish.
We took a steep path into the gorge, where quarrying exposed the Low Main Coal, a shaley sequence with a thin coal seam. From here we were able to access the abutment of Prebends Bridge, all that remains of the original bridge which was washed away in a catastrophic flood in the 1770s. Newcastle and Hexham also suffered flooding at the same time. A new bridge was constructed since the bridge was used to carry water from Grey College to Cathedral Close, and the piers were constructed to point upstream, to prevent them acting as a dam by holding up logs which caused the first bridge to fail. Heavy cross-bedding in the Low Main Sandstone can be seen from the approach road to Prebends Bridge. Dr Johnson demonstrated the existence of the Prebends Bridge Fault when we walked about 30 yards to the north of the road to the bridge to look at the Low Main Coal seam, yet the same seam occurred lower down near the abutment to Prebends Bridge, giving a downthrow to the south of about 45 feet.
We crossed the river by Prebends Bridge to the Peninsula and walked along the path towards the Old Fulling Mill, where the west wall of the Cathedral sits on top of a good exposure of the Low Main Post Sandstone. A spring in the exposure reminds us that the sandstone acts as an aquifer, carrying water from the old buried valley about half a mile to the north. The bright orange staining in the sandstone reminds us that iron is present, possibly attributable to the Brass Thill coal seam beneath. We noted that the sandstone displayed distinct dark and light rings known as 'Liesegang rings', due to the movement of water containing iron salts through the porous sandstone and depositing iron oxide about a nucleus. There are many examples of this stone throughout the Cathedral.
The Low Main Post sandstone was used to build the Cathedral, and is the main rock underlying the Cathedral. It outcrops around the gorge and was extensively quarried here. Large blocks of sandstone were cut to a standard design in the quarry, and used as building material, thus introducing prefabricated construction for the first time. But the proximity of the quarrying to the Cathedral has caused instability in the outer wall of the Galilee Chapel, and we examineded the stout buttresses ordered to be built by Bishop Langley to secure the walls more than two hundred years ago.
The west end of the Cathedral is still on the move slightly, and last year some trees were cut down in the wooded gorge below in an attempt to stabilise the ground. Unfortunately the spring coming from the Low Main Post Sandstone aquifer caused a mud slide, and the path ends abruptly at St Cuthbert's Well.
Following the path beneath the west wall we encountered the Galilee Well, where a well shaft was constructed from the Cathedral to draw the water seeping into it from the Low Main Sandstone. Exposures of the Low Main coal seam could be seen through the grating at the bottom of the well.
As we walked further along the west wall past the Galilee Chapel, Dr Johnson pointed out the old city walls and the prison, and the location of the drains underneath the monks' garderobe, the presence of which caused the monks to move their dormitory from the west to the east! We were further entertained by the story of the Prior who, in times of drought, employed the local maidens to carry water from the river to the brewery. They obviously put their domestic comforts first!
As we made our way up a steep flight of steps to Elvet Bridge and hence back to the University, we realised that we had been treated to a unique and personal account of the geology of the Durham Peninsula by Dr Johnson, who himself had made some important contributions to the body of knowledge of this outstanding geology.
Visit to the foreshore at Sandsend 9 June 2001. Leader: John Waring
John Waring provided the NEGS members who were able to attend this field trip with a fascinating day and it was ideal for family and friends. John began by introducing the background to the Lower and Middle Jurassic rocks which we about to see. During Toarcian times, the global rise in sea-level led to the deposition of finer grained mudstones, collectively known as the Whitby Mudstone Formation in the Cleveland Basin, in contrast to the shallower water sediments of the Staithes and Cleveland Formations. The Mulgrave Shale Member was deposited in oxygen depleted bottom waters. It consists of the Jet Rock, the overlying Top Jet Dogger, a tough calcareous mudstone, and the Bituminous Shales. Jet was mined from the Jet Rock, the Top Jet Dogger often being used as a natural roof. The Mulgrave Shale Member tends to be finely laminated, not having been disturbed by bottom living fauna as opposed to the succeeding Alum Shale Member.
A regional phase of uplift and erosion resulted in a non-sequence with the overlying shallow marine Dogger Formation resting unconformably, with a strong erosional base, on the Alum Shale member. Marine conditions ended with the deposition of the Saltwick Formation consisting of sediments from an advancing delta or coastal plain. The Saltwick Formation in the area to be examined consists of massive channel sandstones.
The day began with a walk along the old railway line to Sandsend Ness, about two miles of level walking for the return trip. Taking the steps up at the far end of the Sandsend beachside car park we reached the track which is halfway up the cliff. At the top of the steps, looking north, you could see two sections: Sandsend Ness in the distance and a taller section closer to. The Top Jet Dogger occurred at sea-level at Sandsend Ness, overlain by bituminous shales (Mulgrave Shale Member), with the Alum Shale Member at the top. The closer section of cliff displayed a section higher up in the sequence, starting with the bituminous shales at sea level, overlain by the Alum Shales and the Dogger. A grass-covered section of the Saltwick Formation topped the cliff section. The bituminous shales are very well jointed, weakening the cliff and contributing to its recession. As we walked north along the old railway line we noted that the sandstone of the old platform had been split by movement of the cliff.
We continued to walk north and our second locality consisted of several large blocks fallen beside the tThere were also some marine fossils.rack. The blocks displayed the pebbly, sideritic sandstone base of the Dogger, and it rests unconformably on the Alum Shale member. The disconformity is due to uplift at the end of the Toarcian, so that erosion occurred before the Dogger was deposited. It is not known whether this was sub-marine or sub-aerial erosion. The Peak Mudstone and Fox Cliff Siltstone between the Alum Shale Member and the Dogger are found in pockets all over North Yorkshire. In Rasvenscar they are found on one side of the Peak Fault and not at the other. Below this point the vegetation is heather.
Continuing north to a slope of Alum Shale on the left, we noted a smell of sulphur, and the concretion near the top of the exposure where we searched for fossils, including the bivalve Dactylioceras ovum (Nunculana ovum), belemnites and the ammonite Dactylioceras commune.
Again continuing north we reached a strange, "lunar landscape" overlooking the headland. This was the result of alum working from the late seventeenth to nineteenth centuries. Alum was used in tanning, and as a mordant in dyeing. It was exported to London after processing, in which the rock was roasted over brushwood for months to remove the pyrite by the production of sulphuric acid which reacted with aluminium to produce aluminium sulphate. This was then steeped in water and either urine (alkaline) or seaweed (potassium) to produce aluminium sulphate in solution. The liquid evaporated until alum salts crystallised out. The process had to be stopped before iron salts crystallised and the appropriate stage is reputed to have been determined by trying to float an egg in the liquid. Once the egg floated, it was time to pump off the liquid leaving the alum salts.
Further on in the distance to our left we could see a large quarry. Its walls displayed two massive structures: the alum shales at the base, overlain by a massive Saltwick Sandstone, separated by a well-bedded Dogger.
We continued walking along the valley until it was crossed by another valley. here, on the right, was another exposure of the Dogger and Saltwick members. However, we observed that the top of the Saltwick had become brecciated by weathering at the top, though the base remained massive.
At this point we turned round and retraced our steps, because our path had reached the entrance to the railway tunnel, now blocked off. Just before departing we looked in the stream on our left and found exposures of the Dogger, a fresh surface of which demonstrated that unweathered siderite is grey.
The next section of our walk depended on the tide as it was a walk along the
foreshore. We found many examples of well-preserved fossils in the
bituminous shales on the wave-cut platform. The shales formed in deep,
anoxic conditions, where there was very little bioturbation, so that very fine
laminae formed. The fossils are often replaced by iron pyrites. It
is reported that 10 gallons of oil could be produced from 1 tonne of this
shale. Dactilioceras commune, Harpoceras, and belemnites were all found
in large numbers. Pseuomyilides (a bivalve)was also found, the only
bottom fauna able to survive the anoxic conditions.
Afterwards, members of NEGS paid a visit to Whitby Museum.
Scremerston 9th September 2001 Leaders: Mavis Gill and Donald Vaughan
The tide was still receding at the start to the trip as we gathered on the beach just south of the main street at Spittal, having persuaded some of the early arrivals of the group to leave a couple of cars about 4 kilometres down the road at Cocklawburn Beach ready to ferry the exhausted drivers back to Spittal at the end of the day.
These rocks reflected the structure of the north of England in early Carboniferous times when the Paleozoic basement rocks underwent extensional activity and regional subsidence. This resulted in a number of blocks and basins, most notably the Northumberland Basin in which over 2,000 metres of sediment were deposited during the Dinantian. The Lower and Middle Limestone Groups which we were to see in the foreshore exposures along this stretch of the Northumberland coast were typical of the Yoredale facies which occur later in the upper strata of the Lower Carboniferous.
These rocks overlie the Scremerston Coal Group which we get a glimpse of at the beginning of the trip on the foreshore at Spittal, with thin coals, seat earths and carboniferous shales and sandstones. They are exposed beneath the Dun Limestone which marks the base of the Lower Limestone Group beneath the cliffs. It is the first of a series of coarsening up cycles.
Indeed, as we descended the steps to the beach at Spittal we spotted the strike of the Dun Limestone NNW across the beach and rising into the cliff at Huds Head. It is a crinoidal limestone with a striking band of the coral Siphonodendron junceum at its base. The lower part of the limestone is shaley, and as it rises into the cliff seat earth and a thin coal seam can be seen beneath it. The upper part assumes the brown hues of a dolomitised limestone and productid brachiopods are present in the shales above. The overlying sandstone forms Huds Head and consists of fine cross-stratified units at its base and coarsening upwards to crossbedded units deposited by migrating channels towards the top. In Redshin Cove a major distributary channel with cross-bedded sandstones could be seen in the cliff cutting down through the shales.
As we crossed the beach in Redshin Cove, the recently departed tide had left the green seaweed on the rocks very slippery indeed, and we made slow progress across the bay. Soon we came across another prominent northeast-southwest trending feature across the beach which turned out to be the Woodend Limestone, on top of a calcrete layer. The Woodend Limestone is famous for its corals and many can be seen in the growth position, most notably Siphondendron junceum. The characteristic polygons of the coral Lithostrotian were visible on the top surface. We lingered here and feasted off this festival of corals, before moving on up the coarsening upwards sequence. Soon we came across a dark band of shales and coals, the Woodend Coals, which are the reason for the erosion and slumping of the cliff behind, here reduced to a grassy slope. Pressing on south across Redshin Cove, we crossed sandstone layers before encountering a striking cementstone layer, very coarse arenaceous grains of quartz with calcite cement. This lay close to a distinctive algal band, characterised by spherical algal oncolites, some the size of golf balls, and we all busily collected what we could. This layer is overlain by a thick oily shale, with its characteristic aromatic smell, indicating that at the time they were lain the sediments were influenced by a nearby land mass. Finally in this bay, as we rapidly approached the massive sandstone headland, we crossed the Watchlaw Limestone, slightly reddish in colour and dolomitised, with a fossiliferous base.
We were now moving into the thick, crossbedded sequence of the Maidenkirk Sandstone, which formed a massive cliff. At this point most of the textbooks advise you to turn back, and indeed we found ourselves confronted with massive blocks of fallen sandstone which required some strenuous clambering over. Not to be daunted, we negotiated a narrow gap in the rocks, and pursued our journey south into Cuddy's Cove. We examined the reddish sandstone cliffs, and were able to identify the lenticular nature of the bed, with evidence of massive channels in places. There were also some highly contorted and irregular beds, forming ball and pillow structures in places. We studied this section for quite a while, pondering its origin, and decided that the sand was laid very rapidly, possibly during an earthquake, causing rapid dewatering due to liquefaction (after all, the Hercinian Orogeny was occurring at this time). Indeed, just round the corner in Cargie's Plantation, a series of small faults can be seen in the cliff. The sandstone is a distinctive red colour, which may be due to a heavy iron coating of the Old Red Sandstone origin.
We sat down for a welcome lunch at Cargie's Kiln, by the Oxford Limestone. This is a prominent feature and well-preserved relic (as well as a useful landmark) on the beach at Cuddy's Cove. By the late Dinantian the Tweed Basin had linked to the Northumberland Basin, and the Middle Limestone group brings with it more uniform conditions of deposition with well-developed Yoredale facies, resulting in thick and laterally continuous limestones.
The Oxford Limestone is the first of these limestone facies, and it is a useful marker horizon which is seen throughout Northumberland, owing to a striking band of algal nodules with red-brown haloes (known as "Girvanella" haloes) near its base. The limestone has shaley partings, probably the sign of impure conditions, and unlikely to support corals. However, crinoid stems abound.
We progressed south east along the beach and crossed a further six thin limestones, still part of a coarsening up process at each marine transgression, but becoming progressively coarser as if part of a prograding delta due to global sea-level changes. We also noted that the massive sandstones of the Lower Limestone group are now absent, another indicator of a changed environment. The limestones are laid in quiet, low energy conditions, and we saw rubbly bits weathered out, indicating feeding burrows where the sediments had been bioturbated. Corals were present in the limestones, and on top we saw the characteristic circular feeding traces, evidence of the organism Zoophycos. Above one limestone, there was an abrupt change to shales, very finely laminated and indicative of quiet conditions, probably the result of deposition by suspension. A layer of bright orange ironstone nodules lined up with the laminations, probably formed diagenetically soon after burial. Towards the top of the shales, fine elongated streaks of silty sand between the shales could be seen, some displaying cross-lamination, probably produced by migration ripples. Quite abruptly, this shaley sequence gave way to sandstone, obviously deposited rapidly, because there was no clear stratification. It contained a striking layer of ball and pillow structures at the top, the result of downward pressure forcing water upwards through the structure, leading to the characteristic structures of dewatering. Higher up in the succession we spent some considerable time examining different features in some detail during the coarse of several coarsening-upward cycles. We drew conclusions about the conditions which would have led up to the low angle hummocky cross-stratification, the presence of swales and ripples, and the surface of one sandstone showing a wonderful pattern of interfering ripples. Towards the top of the sequence there were burrow holes of diplocraterion and horizontal U-shaped Rhizocorallium. Some lighter bands of silts and sands, topped by a coal seam, were seen with roots visible underneath. This gave a picture of a prograding shoreline, at times with evidence of strong currents and storm activity reworking sediments, and at other times calm conditions, where finer mud deposits were draped over current ripples, probably by deposition.
As we rounded the headland towards Saltpan Rocks and approached the Eelwell Limestone, a massive 8m thick, we could now admire structures on a more massive scale, including faulting, folding and thrusting, probably as a result of tectonic activity in the Stephanian due to the closure of the seaway to the south of Britain. This may have led to the reactivation of faults against the Cheviot massive. In a small embayment we noted two linear fault zones on the shore at right angles to the strike of the Eelwell Limestone, extensional in nature. Nearby we studied an overthrust fault with a normal fault, trying to work out the sequence of events within the beds, only the upper beds being affected. Next we admired the famous west-facing overturned assymetrical fold in the Eelwell Limestone, noting the smaller drag folds inside the outer limb, the calcite fibres showing signs of slickensides on the flexure surfaces. There were conjugate shear joints along the axis of the fold. As we walked round the the eastern limb of the fold, we observed yellow, vuggy dolomitised limestone. The Eelwell Limestone is rich in corals and other fauna, and we came across examples of Syringopora, Lithostrotion and gigantoproductoids. Behind the overturned fold and towards the cliff members of our group spread out along the spectactular Eelwell fold, comprising a south-west plunging syncline and two anticlines, giving a characteristic whaleback appearance. We relaxed here, looking at examples of Lithostrotion which had weathered out following rapid sand deposition. We also found many specimens of spiriferids.
We moved on to the final sequence of the day, the Acre Limestone, and its underlying Acre Coal seam which appears in a coarsening-upwards sequence in the cliff. This is a sulphur rich coal, overlain by a thick layer of shales . A very clear reverse fault is seen here, with a displacement of a metre, which ramps up through the bedding. The seat earth, with rootlets, upon which we were standing, repeated in the cliff in front of us. Gouge could clearly be seen in the drag of the fault, and higher up in the shales, climbing ripples could clearly be made out. Above the shales the Acre Limestone is dolomitised and vuggy. The cliff sequence gets sandier towards the top.
We walked along the shore, across the seat earth with brown iron nodules, across the Acre Coal cropping out on the shore, and onto the Acre Limestone, a paler limestone, with large collapsed crinoids and scattered with small algal lenses, a good marker for this limestone. As we made our way back onto the road at Cocklawburn Beach at the end of a very full day on the beach, those who were still alert noticed the brown, dolomitised and vuggy appearance of the Acre Limestone in the cliff. We wished Gordon Wilkinson, who originally planned to lead this trip, but who was bravely enduring a session under the surgeon's knife due to a back injury, a speedy recovery.