Humberside Geologist no 8
published 1991
The 102nd. Summer Programme was very successful, with a good variety of field meetings which were well attended. It is at these meetings that the real spirit of our Society flourishes. They are always very informal and spontaneous. We can never be sure what we are going to find and we can all share in the excitement when somebody comes across something unusual.
This year there were two visits to the Rifle Butts S.S.S.I., the first visit opened the Summer Programme on April 1st. These visits were to tidy up the quarry face and remove any loose rock and cut back plants which are obscuring the exposure.
At the second visit, in October, we noticed that there had been some vandalism at the site, there were broken plant pots on the rock face and nearby nesting boxes had been taken down. Some members of the Society expressed their worries about the rate of erosion at the site. It was suggested that our regular cleaning might be accelerating the erosion, and if we were to leave the loose material alone in the autumn it might help to protect the face from the winter's frosts. So the autumn clean was not as vigorous as in previous years.
After Rifle Butts, members took the opportunity to visit the temporary exposures along the route of the new Market Weighton by-pass at the bottom of Arras Hill. Although the work on the road was nearly complete and the exposures were now mostly covered up, members were able to collect some fossils which were scattered over the site. Dr. Judith Bryce found part of a Dactylioceras ammonite in an iron rich nodule, from just below the Red Chalk, enabling us to date the top of the Jurassic beds beneath the Albian unconformity.
Sketch of the peat bed at Skipsea (Vertical scale exaggerated).
Ron Harrison led a Boulder Committee meeting to Atwick in April. Thirteen members attended this meeting and they recorded 20 different erratic rocks and fossils on the beach and in the cliffs. The Society also looked at 'rafts' of soft white chalk and red and pale brown clays, exposed in the cliff. These rafts of rock were scraped out of the floor of the North Sea by glaciers during the Ice Age, when the North Sea was dry. The Chalk rafts are of Upper Campanian or Maastrichtian age (latest Cretaceous) and are younger than the Chalk of the Yorkshire Wolds. The clays have yielded foraminifera of Tertiary Age.
The afternoon was spent at Skipsea and the party, as well as recording 22 different erratics, studied the Peat Bed. The peat and the underlying clay and silt were deposited in the old Skipsea Mere. The peat contains tree trunks and acorns and hazel nuts were found. Members also considered the problems of coastal erosion in the area - war-time tank traps, which would have originally been close to the base of the cliff, are now about 30 metres away from the present cliff.
In May, Sheila Rogers led a joint meeting of the Open University Geological Society and the Hull Geological Society. The First stop was at Goathland, to examine the type section of the Eller Beck Beds beside the track of the North Yorkshire Moors Railway. Though the exposures were somewhat overgrown and slippery after recent rains, members were able to study the succession and find some plant remains. Lunch time was spent beside the river at Egton Bridge, where an exposure of the Cleveland Dyke can be seen. The dyke baked Liassic shales at the contact and specimens of Dactylioceras and "Inoceramus dubius" were found in the baked shales. These same species were found later in the afternoon at Port Mulgrave, where the meeting finished.
The long distance meeting for the year was a minibus trip to the Sedgewick Geological Trail, near Dent, led by Terry Rockett. Here members tried their skills at logging and measuring dip directions (and found that the dip angles printed in the trail guide were incorrect!).
The trail is a stream section on Langton Common, where Carboniferous limestone is downthrown by the Dent Fault against an older conglomerate, which unconformably overlies Silurian flagstones. Fossil brachiopods and corals can be seen in the limestone and graptolites were found in the flagstones.
In July, a few members of our Society attended the Yorkshire Geological Society field meeting in Lincolnshire. Three quarries were visited, all working the Quaternary gravels which overlie the lower Jurassic clays; these clays are very fossiliferous. (The Society's July meeting at Cayton Bay is reported in a separate article, which follows.)
The field meeting at Filey :- Claire Heyes, Gillian Hughes and Mavis May in the foreground, Ron Harrison is behind them.
In September 13 members of our Society joined 21 members of the Leeds Geological Association for a joint field meeting, led by Felix Whitham. Members examined the Middle Jurassic succession, with the help of an excellent handout provided by Felix. A lot of time was spent collecting fossil echinoids from the clayey beds at the top of the Malton Oolite, and examining the beautifully preserved burrow structures in the limestone blocks on Filey Brigg.
Also in September the Society visited Middlegate Quarry at South Ferriby. The Society had not been to the Chalk pit for a couple of years and members were amazed to see how much it had been enlarged, and how tidy it was kept. The visit was after some very hot weather and the Chalk was obscured by dust, so the party spent much of the time examining the Red Chalk, Carstone and upper Jurassic clays, which were easily accessible and very fossiliferous. Members found derived ammonites of Early Jurassic age in the Carstone and a reptilian vertebra (later provisionally identified as Crocodile) was found by Stephen Potts.
The afternoon was spent on the Foreshore at South Ferriby. Here varve-like silts deposited by Lake Humber overlie glacial till deposits. These Quaternary beds overlie Cenomanian (Mid Cretaceous) Chalk; the distinctive Grey Bed being exposed on the beach. A specimen of Actinocamax primus was found in the Grey Bed.
There was also a walk around the Old Town of Hull, led by Ron Harrison. This was the third year that we have followed the same route, and we seem to take longer each time; probably because we always manage to find something new to look at and talk about. As well as studying the building stones and decorative stones used for shop fronts, this time we looked more closely at man-made metamorphic rocks. As well as looking at bricks and pan tiles, we found that glass, roofing lead, iron railings should also be included in that category!
Mike Horne.
P.S.
Following our visit to Rifle Butts, members became increasingly worried about the state of the site. The 1990-1991 winter was the most severe one for several years, certainly since the site was enlarged by the Nature Conservancy Council.
The Chalk at the site is quite folded and crushed and is overlain by chalky soil. The heavy frosts and snow have shattered parts of the Red Chalk and the White Chalk has been badly attacked by the frost. Also there has been some downhill movement of the soil and loose white chalk (solifluction?), and the netting over the older part of the exposure is bulging under the weight of the slipped material.
We face a dilemma: do we continue to clean the face, exposing it to erosion and weathering or do we allow it to weather naturally, thus protecting it better, but obscuring the site to scientists? The Society has already decided not to clean it so vigorously in the autumn, to protect it better from the winter when presumably there will be fewer scientific visits. But we cannot protect it from water penetration from above, something will have to be done to improve the drainage. Also the very unconsolidated nature of the chalk and soil makes the site unstable; the new exposure created at the base of the slope has upset the equilibrium and perhaps some landscaping to alter the slope or some reinforcement at the base of the slope is needed.
The Society is in contact with the Warden of the Nature Reserve and the N.C.C., and it is hoped that a remedy can be found.
We plan to publish the handouts and logs from some of these field meetings in future editions of Humberside Geologist.
MH April 1991
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