Yorkshire Philosophical Society

Event Information

Rocks, Fossils and Ice Ages at Flamborough

A walk from Danes Dyke to Sewerby

Wednesday 10th May 2023 10.30 AM

£5 per person(to be collected on the day)

Paul Hildreth of Yorkshire Geological Society will lead us in a circular walk along the shore between Danes Dyke and Sewerby (c. 2km) returning along the cliff top path. Total distance 3.5km.

Meet at Danes Dyke Car Park (TA 216692) at 10.30am. Car Parking fees payable at ticket machine. There is also a small café and WC facilities.

Access to shore from Danes Dyke is via a path leading down a ravine cut into glacial deposits.

There will be opportunities to study a complex of Quaternary glacial and periglacial deposits at Danes Dyke and the buried cliff at Sewerby which defines the start of Holderness and represents a pre-Devensian sea cliff with older (Ipswichian) deposits at its foot.

Between Danes Dyke and Sewerby, the cliffs and wave-cut platform are in Upper Cretaceous chalk of the Flamborough Formation. We will traverse approximately 70 metres of flint-free chalk working our way up the succession through the biozones of Marsupites testudinarius and Sphenoceramus lingua and, with luck and a keen eye, find the index fossils.

Halfway to Sewerby we will begin to find an increasing number of sponge fossils until we reach the Flamborough Sponge Bed, famous for its well-preserved, varied and 3-dimensional specimens.

Egress from the beach at Sewerby is via a set of concrete steps. If needed, there are facilities available at Sewerby Hall before we return to Danes Dyke Car Park along the cliff top path.

A copy of this flyer in Word csn be downloaded by clicking here Danes Dyke flyer

To book, please send the completed details as below by email to ypsgeology@gmail.com   (preferred)

Or return the booking form below to the Lodge

YPS terms and conditions apply. See the website https://www.ypsyork.org/groups/social-group/yps-activities-booking-terms-conditions-2/  or ask at the Lodge

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Participant’s Report

The trip was arranged by the YPS Geology Group as a contribution to ’Yorkshire Geology Month’ (May each year) run by the Yorkshire Geological Society. It was led by Paul Hildreth of YPSGG and General Secretary of YGS.

A group of 16, mainly Yorkshire Philosophical Society members, gathered at Danes Dyke and walked to the foreshore. It was a beautiful sunny day with sparkling sea and distant views from Bridlington south to Holderness. Looking back towards the valley we could see the beds of sediment deposited from 20,000 years ago by retreating ice. They included a bed of coarse material from tundra conditions as well as finer glacial lake deposits. All had been deposited in the deep valley of Danes Dyke cut into the chalk before the last glaciation. Some material had subsequently been eroded-out by the stream.

West along the foreshore we managed to see index fossils from some beds in the chalk. They included Marsupites testudinarius, a free swimming Crinoid and Sphenoceramus lingua, a large bivalve. The largest we found was about 300mm long. There were also sponges seen as iron-stains in chalk boulders. Unfortunately, only one of the group found any sponge specimens in-situ in the famous Flamborough Sponge Beds at Sewerby Rocks, part of the wave-cut platform.

Along the top of the chalk cliff, the bed of coarse material from tundra conditions continues with Skipsea Till, a thick clay deposited from the ice sheet. There are Calcrete blocks on the foreshore from the coarse bed just under the Till. The Till and Calcrete include dark erratics from either North Yorkshire or Northumberland and, where they have been eroded out, lie along the beach.

A few hundred metres west of Sewerby steps we saw the Sewerby Buried Cliff about 12m high. Geologically this is the end of Flamborough Head, the point on the coast where the chalk terminates and the glacial till of Holderness starts. The chalk cliff was the eastern seashore for this part of the coast about 120,000 years ago when the sea was about 2m above present levels. It has been buried under the glacial till of Holderness and follows an inland line in an arc to Hessle and continues south into Lincolnshire. At the cliff section we saw 120,000 year old sand and rubble deposits at the base of the cliff which are similar to those found in recent deposits in the area today.

The return walk was on the cliff-top then through the woods of Danes Dyke with their spring flowers and fresh green leaves. The mixed group had differing knowledge of the chalk, however everyone felt they had learned something and enjoyed the weather and the views.

David Taylor, YGS member

Photo below: the group at Danes Dyke by Peter Wheatcroft