Beneath our feet in Welton, Melton and Wauldby:

an introduction to the geology

by Terry Rockett

The Jurassic Period.

Some 150 million years ago, during the Jurassic Period, the land that underlies this area was at the bottom of a deep sea, the surface of which was some 100 metres higher than present sea level. This sea was between 30°N and 40°N - the same latitude as the coast of North Africa today. Living in this ancient sea were ammonites, belemnites, corals, bivalves, ichthyosaurs, plesiosaurs and many other life forms. Life on the land included cycads, ferns, conifers, insects (including wasps), early birds and mammals, and a number of large reptiles, including dinosaurs. In other parts of the world major events were happening. Africa and North America started to separate initiating the Atlantic Ocean and the mountain building that would produce the Rockies and the Andes.

Locally, in the late Jurassic, sediments brought to the sea by rivers sank to the sea bed and built up into a layer of clay some 50m thick. In 1958 15m of these clays were exposed in the lower Melton Bottoms quarry. At least fourteen different species of fossils have been found in these clays, including ammonites and oysters.

The Cretaceous Period.

The Jurassic Period was followed by the Cretaceous Period (creta is Latin for chalk). Many of the early rocks of this period do not exist in this area.

By some 80 million years ago plate tectonics moved this area to about 40°N - a modern-day Mediterranean latitude. A warm, clear sea up to 600m deep existed. It teemed with life such as ichthyosaurs, plesiosaurs, ammonites, belemnites, gastropods, sea urchins and sponges. However the most abundant life forms were microscopic planktonic algae which, when they died, left a calcium carbonate skeleton called a coccolith. Millions of these rained down to the sea floor forming a thick ooze, later to ' dry out ' and become chalk. Up to 90% of chalk is made up of tiny calcite crystals from these coccoliths. (Similar algae today live in some clear tropical waters at depths between 50 - 200m.) Flints are found in some of the Chalk, made of silica derived from sponges, diatoms and other sources.

On land there was a rapid development and spread of flowering plants. Trees such as planes, sycamore, oak, walnut and willow grew along with ferns and conifers. There was specialisation of reptiles on land, in the sea and in the air. Mammals reached the size of cats and lived on plants, insects and other creatures. The first snakes appeared and vast numbers of different insects, including bees, evolved. Elsewhere the Atlantic continued to widen as South America and South Africa separated.

In Melton Bottom Quarry the earliest Cretaceous rock is called Carstone. This thin layer is made up of pebbles and sand. It is relatively poor in fossils.

Lying on the Carstone is an unusual layer of Red Chalk about 2m thick. It is very fossiliferous and has yielded at least 25 different fossil species. The red colouring is due to traces of iron.

Above this are layers of the more usual 'white' chalk, over 25m thick in the main quarry. In Thomas Sheppard's book ' Geological Rambles in the East Riding of Yorkshire ' (published in 1904) there is a photograph of Melton Bottoms Chalk Pit showing it to be about 8m high and 15m wide.

In recent years the working face of the quarry has been up to 800m wide - quite a contrast!

Within the Chalk is a distinct layer named the 'Black Band'. Fossils are fairly abundant below the Black Band, virtually absent within the Black Band and new fossil types develop above it. The Black Band marks a period during which the extinction of many life forms occurred. This is still being studied by geologists, but initial indications are that this was caused by an influx of oxygen-depleted waters spreading over the sea bed, completely changing the environment and wiping out the existing life, which could not cope with the new conditions. The Black Band or an equivalent signature can be found throughout the world in Cretaceous rocks of the same age as the Melton Quarry.

At the end of the Cretaceous occurred another extinction - a major world-wide one which resulted in the end of many life forms, most notably the non-avian dinosaurs. The blamed culprit is a meteorite which hit the Earth near the Yucatan Peninsula, in the Caribbean. Other factors also probably played a part.

The Quaternary Period

The time we live in is called the Quaternary Period by geologists. It started about 2 million years ago. It is often referred to as the Pleistocene Epoch, except for the last 10,000 years which are referred to as the Holocene Epoch.

At the start of the Quaternary Period Britain had reached its present geographical position. The Earth started a period of intense cold - the Pleistocene “Ice Age”. Ice sheets spread from the poles and, at their peak, covered 30% of the land surface (compared with 10% today).This was not a period of unrelieved Arctic conditions - there were numerous short, warm periods (interglacials and interstadials) when temperatures were as warm as, or warmer than, the present. The ice spread during the cold periods and regressed when it was warm. At some time in Britain all the land north of a line from the Scilly Isles to the mouth of the Thames has been covered by ice.

Some 60,000 to 70,000 years ago there was a small ice sheet in Scotland. At this time the local coastline ran from approximately Hessle Railway Station through Harland Way, Cottingham, through Driffield and ended at Sewerby on Flamborough Head.  Ice moved from Scotland, the Pennines and the Northumberland and Durham coasts. This met with ice which had crossed the exposed North Sea basin from Scandinavia (global sea level was 120m lower than today).  As they move ice sheets erode the land and carry the material with them - this is called 'till'. They also bulldoze frozen material along their front. The ice reached the old East Yorkshire coastline and moved westwards into the Humber Gap as far as Long Plantation on the eastern boundary of Welton Parish some 20,000 years ago.

The last glaciation in East Yorkshire (Image by T Marsters)

At this time the climate changed once again and started to warm up. The ice started to melt and left a bulldozed ridge of material (a terminal moraine) stretching across the Humber from Red Cliff to South Ferriby and Horkstow in Lincolnshire. As the area to the east was still covered by ice sheet, melt waters had to flow westwards beyond the moraine. A vast lake, known to geologists as Lake Humber, was created which flooded the land as far as the Vale of York and the Trent and Ancholme Valleys. The eastern section of the M62 crosses the bed of this ancient lake.

By about 14,000 to 15,000 years ago the ice had retreated far enough for the lake to drain eastwards through the ridge of moraine and flow towards the North Sea, creating the present course of the River Humber. As the ice melted it left behind many millions of tonnes of material it had eroded and carried - Till or “Boulder Clay”. The deposition of some of this formed the Plain of Holderness. These tills are subject to rapid erosion - at least 1.6Km of coastline has been lost since Roman times. The beaches along the coast and Humber are covered with a range of rocks and fossils carried there from other areas by the ice that are now being washed out of the tills.

Welton Dale

A major landscape feature of the parish is Welton Dale - a dry valley. There are many similar dry valleys along the western edge of the Wolds. Chalk is a porous rock so why did water not sink into the chalk as it does today? The answer is that these valleys formed in a periglacial phase when the chalk was frozen to depth and was impermeable. Surface flow of melted ice and snow cut the valleys. There are some glacial meltwater channels in the eastern Wolds.

Conclusion

The ice from the “Ice Age” still exists in Norway, Iceland, Greenland, etc., the “Ice Age” probably ended in this area about 14,000 years ago. Though the generally accepted date for the start of the present interglacial is 10,000 years ago. As yet there is no single explanation for the onset of Ice Ages and the ice could return.

There is a lot of evidence about the past to be seen by the observant viewer. It is possible to find fossils and rocks on the beach between Brickyard Lane and Red Cliff. If you feel so inclined, have a walk around the Parish along some of the footpaths and see if you can find some evidence of this area's ancient past.

Safety note - no one should enter a working or worked out quarry without permission and supervision - they are fraught with danger.

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copyright Hull Geological Society 2020