During Toarcian times, a global rise in sea-level led to the deposition of finer grained mudstones, collectively known as the Whitby Mudstone Formation (WMF), 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 Mbr. tends to be finely laminated not having been disturbed by bottom living fauna as opposed to the succeeding Alum Shale Mbr (AlShMem).
A regional phase of uplift & erosion resulted in a non-sequence with the overlying shallow marine Dogger Formation (DF) resting unconformably, with a strong erosional base, on the Alum Shale Mbr. Marine conditions ended with the deposition of the Saltwick Formation consisting of sediments from an advancing delta or coastal plain. The Saltwick Formation (SF) in the area to be examined consists of massive channel sandstones.
The first part of the itinerary will be a traverse northwards along the cliff top. Evidence of landslips, coastal erosion and extensive quarrying of the AlShMem. will be seen. Lithology and fossil content of the ASM and DF will be examined. The strong erosional base of the DF will also be seen. We will then walk along the foreshore towards Sandsend Ness to examine the lithology and fossil content of the Bituminous Shales and underlying Jet Rock.
After lunch, a visit will be made to Whitby Museum in Pannet Park. It contains a collection of ammonite type specimens which is unique. Other exhibits include liassic fish, marine reptiles, plant fossils, and exhibits of local rocks (including Permo-Triassic from Cleveland Potash) and glacial erratics found in North Yorkshire.
The museum also includes sections on Natural History, Archaeology and local history.