Sunday, 16 February 2020

LIPAROCERAS IN SEPTARIAN NODULE

552 kilometres (343 miles) to the north of the Kimmeridge Clay exposures is the town of Robin Hoods Bay on the Yorkshire Coast. Beautiful examples of septarian nodules, many associated with ammonites and other fossilized material.

These photos show a delightful example of a lovely Liparoceras sp. from Robin Hoods Bay with some interesting septarian veins radiating away from the ammonite. The awesome Harry Tabiner gets full credit (and my unending respect) for the find, preparation and photo of this lovely Lower Jurassic, Lower Lias specimen.

Robin Hoods Bay is a small fishing village and a bay located in the North York Moors National Park, 5 miles (8 km) south of Whitby and 15 miles (24 km) north of Scarborough on the coast of North Yorkshire, England. Bay Town, its local name, is in the ancient chapelry of Fylingdales in the wapentake of Whitby Strand.

Around Robin Hood’s Bay, well-developed platforms cut across outcrops of Liassic shales. The cliffs are primarily till resting on the Lias. Cliff falls at this location are common. The cliffs are about 50 m in height in the northern part of the bay where they are cut by two steep-sided valleys, Mill Beck and Stoupe Beck. Here the Lower Lias forms most of the slope, with near-vertical lower cliffs comprised entirely of Lower Lias rocks.

The rocks in the lower cliffs are dark grey marine shales from the Redcar Mudstone Formation. The Lias Group at Robin Hood’s Bay is represented, in ascending order, by the Redcar Mudstone Formation, Staithes Sandstone Formation, Cleveland Ironstone Formation and Whitby Mudstone Formation and contains stratotypes for several zones and horizons.

Most fossils are found either from the foreshore exposures during scouring conditions or in rocks, boulders and nodules. They can also be found after cliff falls. To search for septarian nodules, head north for several miles along the coast from Robin Hoods Bay.

Be mindful of the tides as this location should only be attempted on a retreating tide. Minerals can be found in both the large Septarian nodules and partially replacing the many fossilized tree limbs and roots found in the sandstone blocks from higher up in the cliffs. This site can be dangerous and is not appropriate for children.

To look for fossils, search through the rocks and concretions along the foreshore. Ammonites can often be found this way, but you will need the right tools and good eye protection.

Fossils loose on the foreshore are rare. You generally need to work for finds at this location. A few good storms help with collecting here. Robin Hood’s Bay yields little during the summer months. The best time to collect is after the winter storms.

The north side of the bay is rich in ammonite remains and these can mostly be found after cliff falls. The ammonites (Platypleuroceras, Tropidoceras, Acanthopleuroceras and Androgynoceras) can be found, along with the large bivalve, Pinna. Within the calcareous shales, exposed in the low tide reefs at the centre of the bay, you can find the ammonites, Arnioceras and Caenisites.

Robin Hoods Bay Directions from the good folk at UK Fossils Network:

At Robin Hood’s Bay village, you can park in either the small car park at the top of the hill or the second larger one just a short walk away.

  • From here, the best end to visit is the north side. You will find a footpath at the top of the hill, to the left of the main street leading to the beach. This winds around and passes a picnic area.
  • You can also visit the south and middle part of the bay. To do this, go down into the main street at the bottom of the hill and follow round to the right. You will see some steps, which follow the sea defence and lead to the shore.
  • Paleo-coordinates: 54.43442°N, 0.53079°W
Photos: The deeply awesome Harry Tabiner gets full credit (and my unending respect) for the find, preparation and photo of this lovely Liparoceras sp. in a septarian nodule, Lower Jurassic, Lower Lias specimen.

Reference: Humberside Geologist No. 14, Humberside Geologist Online, The geology of East Yorkshire coast.http://www.hullgeolsoc.co.uk/hg146t.htm
Reference: UK Fossils Network: https://ukfossils.co.uk/2007/03/18/robin-hoods-bay/ This website provides a wealth of information and is very well done. Highly recommend checking them out!
Reference: https://www.mindat.org/loc-267536.html