Pleistocene fossils

Due to the extensive deposits of River Terrace and other gravels in Cambridgeshire, there have been some amazing discoveries of fossils from both cold and warm periods of the Pleistocene ‘Ice Age’. Many (such as mammoth tusks) date from the last glaciation (the ‘Devensian’) when the region experienced tundra conditions but others (such as hippo skulls) date from the earlier warm phase (the ‘Ipswichian’). Others date from even earlier glaciations or warm periods.

Our local museums have excellent displays on the Pleistocene Ice Age, its geology, environments and fauna, with some impressive fossils – many of which have been found locally.

Ice Age display, Sedgwick Museum – mammoth tusks now in the Sedgwick

Fossils in the Gravel – at the Sedgwick Museum

Glaciations

The last ice sheet to cover Cambridgeshire was thought to have occurred in the Anglian Stage glaciation which ended about 425,000 years ago. There are widespread deposits of Glacial Till and Glacial (Lake, River and other) Gravels from this glaciation in the county, particularly covering the higher land to the west and south of the Fens. The Lowestoft deposits are from this time.

It has now also been shown that there was a glaciation that reached as far as Cambridgeshire about 160 million years ago, in the Wolstonian Stage, The glaciation advance, to the maximum glacial limit Skertchly Line complex in Fenland, occurred during the Late Wolstonian Substage, MIS 6. 

Papers on evidence for the Late Wolstonian Glaciation including the Tottenhill ice advance into the Fenland:

Late Middle Pleistocene temperate and associated events in lowland England – ScienceDirect

Late Middle Pleistocene glaciation in East Anglia, England

River Valley Sands and Gravels

Many studies have been carried out on the extensive deposits of the current and former river valleys of the region. These deposits are mostly sands and gravels carried by more powerful rivers than those that remain today. As a river system evolves it creates a series of ‘terraces’ at progressively lower levels as it cuts down  into the underlying bedrock (and into older Quaternary material in some places). These broadly defined terraces have been mapped by the British Geological Survey and are shown on geology maps as Terrace 1 (the youngest), Terrace 2 (older) etc (in Cambridgeshire, up to 4 terraces are shown for each river).

The ages of the terraces are shown by the types of fossils found within them and by dating techniques such as pollen analysis. As reworking of older material can occur, some terraces cannot be separated deifinitely and some patches of sands and gravels can be very difficult to date.

In addition to the overlapping of some terraces, each terrace itself consists of a complex collection of deposits of varying composition and ages, some of which can be recognised as occuring in a range of locations along a valley. The picture is further complicated by the presence of deposits  brought, not by rivers but by glaciers. In the Cam Valley this includes gravels, cobbles and finer material of the Lowestoft Formation, dating from the Anglian glaciation.  Dr Steve Boreham has carried out many studies on the deposits within the broader valley of the River Cam and has identified a number of ‘members’ within each terrace.

The Geology of the Middle Cam Valley, Cambridgeshire, UK  Boreham, S.; Leszczynska, K. Quaternary 2019, 2, 24.

The Geology of the Wicken Vision Area, lower Cam valley, Cambridgeshire, UK. Boreham, S. Geosci. 2013, 92, 47–59

Holocene, Weichselian Late-glacial earlier Pleistocene deposits of the upper Cam valley at the Hinxton Genome Campus, Cambridgeshire, UK  Boreham, S. Rolfe, C.J. Geosci. 2009, 88, 117–125

The Quaternary history of the Wash fluvial network, UK. Boreham, S. White, T.S. Bridgland, D.R. Howard, A.J. White, M.J. Proc. Geol. Assoc. 2010, 121, 393–409