THE FOSSIL RECORD OF EAST YORKSHIRE

Good afternoon gentlemen,

At the end of July a letter arrived at my home with a prominent red square stamp at the top of the envelope stating "if undelivered please return to Humberside Police, Queens Gardens, Hull", my wife usually collects the mail off the door mat and immediately demanded to know — "what had I been up to?" I tried to think — had I inadvertently gone through a traffic light at red and been photographed by one of those numerous cameras pointing menacingly from the top of a traffic light? Or had I committed some other misdemeanour? However on opening the letter with some misgiving, all was well: I had received a note from Sally Leighton, the Chief Constable's secretary confirming today's rotary club meeting.

Perhaps I should first introduce myself and say, I am not a professional speaker (which I have to admit I am not very good at) so I thought an early warning might prevent any boo's later. Nor am I a professional geologist or palaeontologist but I will own up to being an amateur who has always had a keen interest in fossils from an early age. In fact I now consider myself as a geriatric fossil collector well past my sell by date. I first became interested in belemnites (said to be thunderbolts by locals) and Gryphaeas (Jurassic oysters) stated to be Devils Toe Nails during the late 1920s and early thirties — my favourite grounds were along the Hessle and Ferriby foreshores (easy to reach by bicycle) and in those. I was greatly mystified by these finds so I decided to learn more. I soon found out that they were in fact - fossils of marine life over one hundred million years old. My interest continued until the outbreak of the 1939/46 war when I was called up for active service in the army for 6 1/2 years and at that stage I rapidly became more interested in self preservation than fossil preservation.

After the war my early priorities were finding a job, a wife, a home etc. In the early fifties I again resumed collecting fossils in my spare time, at first from the Jurassic sandstones exposed in. The pits at South Cave and S. Newbald and later from the Jurassic shales and rocks of the Staithes, Robin Hoods Bay and Whitby areas of the Northeast Yorkshire coast. Fossils were easy to find in these highly fossiliferous stratas and in due course I amassed a large collection of ammonites, belemnites, bivalves, brachiopods and numerous other species, but I encountered difficulties due to the lack of successive exposures in some inland quarries and coastal sections in building up a continuous stratigraphical succession of Jurassic rocks and fossils, although I did manage to construct continuity of some species which are depicted on these panels.

My interest then became more focussed on the late Cretaceous chalk which overlies unconformably over most of the Jurassic stratas apart from thin layers here and there of lower Cretaceous deposits in East Yorkshire - with thicker beds of clays and red chalk at the type section of Speeton on the east coast. In those days there were many small and medium sized pits apart from the extremely large commercial quarries exposing very thick sections of chalk up to 50 metres in depth. Additionally, the magnificent permanent chalk cliffs in the Flambro, Bempton Bridlington area were all accessible providing a huge location for research. I began to realise that beneath my feet lay a vast and ancient chalk sea bed ranging in age from about 100 million to 70 million years ago. This huge platform of chalk dipping out under the north sea stretched from the Flambro area with a broad spread through east Yorkshire, Lincolnshire and Norfolk and was laid down in a separate basin to that of southern England. In some respects with very different deposits (which is another story but not today).

This sea bed accumulated very slowly, probably in warm shallow waters similar to the Bahama banks type deposits which are being laid down off the coast of Florida at the present time. Most of the chalk as we know it today is composed of about 80% tiny calcite crystals derived from the disintegration of complex ring like structures known as coccoliths, secreted by a family of highly specialised unicellular green algae. The remainder is made up of microfossils including foraminiferas, plankton skeletons, ostracods, bryozoa, ground up bivalves, tests of echinoids and spines, starfish ossicles and crinoids. This whole mixture of calcitic material would be winnowed by currents and turbulence, settling on the sea bed in the form of a vast chalky ooze which slowly compacted into a more solid deposit, reaching rock building proportions which we know as chalk. Some complete examples of the marine life which existed at that time were preserved intact in the seabed and we are able to find their fossilised remains at various levels in the chalk today (some examples are exhibited here) and can be used to identify specific horizons in the chalk succession.

If you imagine the chalk layers of varying thickness interspaced with thin marl bands, bedding planes and in some parts, flint bands, it is possible to identify the different beds by the fossils they contain, once you know the biostratigraphy, in other words the fossil succession, which I will refer to later.

The chalk sea of the northern province which I have already mentioned, spread out from eastern England, across the north sea, into northern Germany and extended into some parts of Russia, its chalky ooze deposits eventually becoming bed rock, over a great period of geological time some parts of the sea bed were uplifted and became the land we see on the surface at the present time (the Yorkshire Wolds).

Careful collecting of in situ macro & microfossils in succession has shown that it is possible to correlate these fossils very closely with those found in the chalk quarries of the Hanover, Lagardorf and Misburg/Hover districts of N. W. Germany with those of eastern England, Similar species also occur on the Russian platform.

The chalk exposures on land in the north of England (north of the Humber) are about 542 metres (1776 ft) thick on the coast confirmed by drilling during the creation of natural gas chambers at Atwick near Hornsea, thickening eastwards into the north sea gas fields up to 800 metres.

The Yorkshire Wolds form a broad crescent shaped exposure which sweeps inland from Bempton cliffs, Flambro Head and Sewerby buried cliff. The original chalk coast before the ice age started at Sewerby cliff where an abrupt junction of chalk and boulder clay can be seen. This chalk cliff virtually follows the route of the Bridlington to Driffield road and down to Beverley, Willerby, Anlaby, and Hessle where near to the railway station the buried cliff was exposed when the new road to the M62 was cut.

The whole of the plain of Holderness is made up of boulder clays with numerous deposits of sands and gravels, left behind by successive ice ages, and resting on planed down chalk. The chalk of the Yorkshire Wolds is continuous across the Humber and into Lincolnshire. (Describe problems with Humber Bridge and Ennerdale Link). Early workers on the geology of the Yorkshire Chalk, subdivided from west to east, the exposures into Lower Cenomanian Chalk, a grey gritty chalk without flint, Middle Chalk which is mostly flinty and interspaced with many types of flints, including, burrow, nodular, lenticular and tabular, the latter forming vast sheets in some areas, which can be used to identify different horizons in the succession. Also present are numerous bands of clay rich marls, some containing volcanic ash. Marl bands occur throughout the chalk succession. The Upper Chalk is flintless and mostly occurs along the coast from high stacks Flambro Head to Sewerby steps and in a few inland quarries. These simple divisions are not now in use as more formal formations and numerous subdivisions has been established.

The very basal part of the chalk is brick red with some variations. And rests upon sandy and clay deposits of early cretaceous age. These beds are best exposed in the old Melton Quarry, South Ferriby Quarry, and at Speeton.

Over the last 45 years or so I have been privileged in being allowed access to many chalk quarries in East Yorkshire where I have been able to measure and log sections and at the same time collect and locate specimen fossils to specific horizons. I have also measured and logged the chalk exposed in the cliffs from Flambro Head down to Sewerby, (a distance of 6 1/2 k.m.). The total thickness here is 165 metres. Overall it has been possible to link together over 450 metres of chalk stratas in stratigraphic succession with key fossil ranges which can be related to specific marl bands, flint bands, burrow horizons and hard beds.

You may have been wondering where the title of this talk "the fossil record of east Yorkshire" proposed by my neighbour Don Atkinson fits into the geological mish mash so far; this has been necessary to provide a background to the fossil succession in the Upper Cretaceous period in East Yorkshire.

Throughout the upper Chalk era numerous extinctions in marine life occurred and many new species appeared. Their fossil remains occur in bands and in some instances in thick beds, with occasional isolated individuals between these levels.

In the Jurassic period ammonites were very common and the numerous species could be utilised to zone successive stratas. However in the northern Cretaceous Chalk ammonites are rare, found in only the lower and highest beds and therefore not of much use for working out the stratigraphy.

Bivalves;- play an important role in zoning the chalk succession and the evolutionary development, the number of species and the limited ranges of some species of the large inoceramid bivalves provide important stratigraphic markers they are common at most horizons in the chalk.

Echinoids (sea urchins) are also of limited use as some species are confined to specific levels. The evolutionary trends in the ambulacra grooves of the test provide recognition of levels in at least six of the zonal horizons. (see panel)

Brachiopods (lamp shells) are very common in most of the stages of the succession and again show variations in evolution but at the present time only one species is utilised for zonal identification. (see panel)

Belemnites (see panel). ? Related to present day cuttlefish (like bullets) squid like creatures living in the hollow end (alveolus) with small tentacles. They are not common in the white chalk. Several species occur in the Lower Cenomanian chalk, re-appearing towards the top of the flinty chalk, continuing to occur up to the highest beds in Yorkshire. Very common in the red chalk and clays below the base of the white chalk, also in higher beds of the chalk of Norfolk.

Belemnites collected on a bed by bed basis from the top of the flinty chalk at high stacks Flambro through to Danes Dyke near Sewerby (a thickness of 105 metres) show an increase in the depth of the alveolus from 4 mm to 17 mm (plus 13.5 mm. With a depositional age span of about 4.7 million years for these beds, — statistical work on about 100 specimens indicates the depth of the alveolus increases by 1mm per 348,000 years. The rate of deposition is approximately 1 metre of chalk per 44, 700 Years. These findings compare extremely well with the belemnites and deposits seen in the huge chalk quarries at Misburg and Lagerdorf N.W. Germany.

Crinoids Marsupites and Uintacrinus form important marker zones and the influx of these species which are confined to specific succeeding horizons are used as zonal markers both in England and Germany. Many other macrofossils occur but are not normally used to name fossil zones.

Microfossils nannofloras, are found in great abundance throughout the chalk succession and are of great value to prospecting companies, particularly in the oil industry with drilling rigs based in the north sea. Foraminiferas, ostrocods and coccoliths show evolutionary tendencies and have frequent extinction rates which can be used with much advantage, proving to be a useful tool as a means of identifying specific levels not only in the chalk but in other stratas as well. Drill cores can be brought to the surface from great depths below the sea for microfossil analysis by rig based geologists. Much research is being undertaken at the present time in this field as it is not always possible to pick up macrofossils in drilling rig cores.

Once the succession and identification of both macro and microfossils and their evolutionary trends are acquired and recorded it is possible to read the signs in some stratas like a book and assemble them in stratigraphic succession. This means of identification only applies to mainly sedimentary rocks.

The lowest exposures of upper Cretaceous chalk start at Melton Bottoms, rising through Welton Wood, Enthorpe Railway Cutting, Willerby, Little Weighton and Middleton-on-the-Wolds, with higher inland sections seen at Langtoft, Bainton, Beverley, Ruston Parva and Nafferton Grange, also including the magnificent coastal sequences in the Bridlington - Flambro area.

Apart from the vast fossil record contained within these huge thicknesses of Chalk sea bed, perhaps we should also remember the commercial advantages of this valuable mineral, such as cement making, paint, plasters, fillers, toothpaste, and many other uses including paper, lime for agricultural purposes and road building material. The Chalk of the Yorkshire Wolds acts as a huge aquifer, storing much of the water which we use in the Hull area every day.

Sadly many of the inland quarries are being filled in-along with it, some of the geological history and the many fossil faunas will disappear and not be available for future generations to study.

In the short time available to me 20 to 25 minutes I have only been able to give you the briefest glimpse of the fossil record and the geological events which started over 100 million years ago with the laying down of the chalk bed in an ancient sea.

As you probably already know - the dinosaurs became extinct at the end of the Cretaceous period, and it has been suggested they were killed off due to the impact of a giant meteorite or comet striking the earth and blotting out the sunlight for many months. A friend of mine had a different theory — stating they died of boredom looking at the chalk. I sincerely hope that none of you have suffered a similar fate listening to me today.

Thank you very much.

[Scanned and edited 26/8/2010. MH]

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