Hull Geological Society
Geological Survey of North Cave Wetlands
Geological survey 30th November and 20th December
2003.
By Barrie Heaton, Colin Clark, Mike Horne,
Stephen Whitaker, Stuart Jones, Terry Rocket, Tina and Tony Hibbert.
Explorer Sheet 291 1:25000 Map Ref SE 885330
The pits are at the eastern edge of the south eastern
area of the Vale of York. The surface of the Vale is mainly glacial deposits
covered by a thin veneer of alluvium due to flooding down to historic times.
The pits are some 7 km north of the River Humber and
close to the north west boundary of the village of North Cave. The land to the
north, west and south is flat and low lying (only 1 or 2 metres OD to the
south). The pits are at 7 metres OD. Immediately to the east the land rises to
over 30 metres OD in less than 0.5 km. This slope is part of a narrow
north-south ridge of Jurassic rocks, which run parallel to the nearby western
scarp slope of the Cretaceous Yorkshire Wolds.
Site description - 100 acres of former gravel pits beside
Dryham Lane, North Cave. Working stopped about 2000. Now owned by Yorkshire
Wildlife Trust and being developed as a Wetlands area for birds. The site was
designated a RIGS in December 2003.
Brief geology - Brown clay/shales and dark blue/grey
clays/shales probably of lowest Jurassic age and perhaps latest Triassic covered
by Quaternary gravels.
Preliminary report (raw data):
Site 0 - SE 88595 32880 - brown shale and brown siltstone
with fish scales, in situ at the edge of the lake, >50 cm. Grey limestone in
situ 30 cm below the water level, containing 1-2 mm diameter fish scales and
deformation features. Auger hole went down about 90 cm through grey clays
(brownish, then pale grey, then getting darker) before hitting rock. A second
auger hole to the west went through similar sequence, flooded at the bottom and
hit rock.
Site 1 - SE 88616 22897 - trench in brown and grey shaley
clays. The trench base comprised a laminated mudstone from the water level to 65
inches above. The colour of the mudstone varied dark brown at water-level,
through pale grey 8 in above, distorted in the trench sides, pale grey
interleaved with brown up to 17 in. Above this height up to 40 in the colour was
a lighter dark brown, and the top 15 in was light brown with a pale grey band in
which light coloured stone pieces (6-8 in wide by 1.5 in thickness) were
embedded. These pieces contain fossil bivalves, but there could no confidence
that these were in situ.
Site 2 - SE 88597 32971 - trench containing back fill
over grey and brown clay [Sample] Dark grey mudstone from water level to 30 in
height, succeeded by random white thin layered stone interleaved with clay to a
height of 40 in. This was capped by red-brown sand coarsening downward and
increasingly grey with a thickness of 6 in. This was covered with pebbles mixed
with chalk and grey mudstone to a total height of 60 ins above water-level.
Site 3 - SE 88588 33037 - trench - 10 ins grey shaley
clay above the waterline covered by brown pebbly clay thought to be back fill.
Between sites 1 and 3 there are many pieces of 'White
Lias' (?) platy white limestone and a shelly limestone. This was not seen in
situ but was thought to be local. The fossils seen in the white limestone
include Liostrea hissingeri,
Protocardia and
Pleuromya; indicative of a Rhaetic
age.
Site 4 - SE 88492 33235 - Northern end of gravel face and
adjacent island.
Measured section (from top).
> 40 cm dark brown sandy subsoil.
65 cm brown, orange and grey silty sands.
10 cm chalky gravel.
55 cm light brown and pale grey sands with thin
chalky gravel layers. Some cross bedding in places.
140 cm chalky gravel - containing rounded-flattened
chalk pebbles up to 3cm diameter, (ca. 10%) pale grey shattered flints and
some erratics such as Gryphaea and brown sandstone. Specimens of Gryphaea
and a belemnite from the Chalk collected from the gravel on the island.
ca. 100 cm brown clay, 10 cm grey at base.
Notes -
Grid references by GPS - accuracy plus or minus 6m.
Sites 0 to 3 are in the south-east corner of Lake 5. Site
4 is in the middle of the eastern face of the new lake:- the site sampled is at
the northern end of the gravel face, the 'island' is 5 m out into the lake from
here and will be covered when the water rises and the 'ramp' is at the
south-western end of the gravel section.
Water level in the lakes was about 80-90 cm lower than
usual. Heights shown on the site plan are relative: add 4.9m to get height OD.
Gravels get deeper and thicker to the west; also chalk is
replaced by 'sandstone' in the gravels to the west.
The Gryphaea
fossils collected or seen loose on the site - some were very water worn and
others were very fresh - indicating a distance source perhaps derived from tills
and a nearer source probably derived from the nearby Lias.
Sediment analysis -
Sample one [= WET11] (> 63um) -
brown silty sand. 80% small quartz grains, half clear and glassy and half
frosted and yellow coated. Not as well sorted as some other samples. Some
Inoceramus needles, carnelian and chlorite. Derived Chalk foraminifera including
Hedbergellids and
Heterohelix.
Sample three (>63um) - very similar to sample five.
Sample five (>63um) - mostly quartz - subangular to
rounded: half clear and glassy and half frosted. Quite well sorted. Some
carnelian, grey bits. green bits, chalk bits, ?limonitic ?ooliths and
Inoceramus needles. Some derived
Chalk planktonic foraminifers including Hedbergellids and
Heterohelix. Some modern plant
material.
Sample 8 - Platy or layered weathered shale with calcite
inclusions. Devoid of micro-fossils, but contains carbonised vegetation in form
of small leaf-like and root-like strands.
Conclusions: -
The shales and clays may be of Rhaetic or Early Liassic
age, but we found no microfossil or macrofossil evidence.
The sands and gravels contain derived Lower Jurassic
fossils and Upper Cretaceous fossils and microfossils. They may be associated
with the Devensian Lake Humber.
The source of the jet and loose
Gryphaea oysters is probably the gravels. We did not see the shell limestone
and plate white limestone in situ -
they probably have been brought on to the site from other nearby localities.
Acknowledgement - We thank Stephen Martin for allowing
access to the site and for providing information about the site.
References:
Gaunt G D, B N Fletcher and C J Wood, 1992. The geology
of the country around Kingston upon Hull and Brigg. British Geological Survey.
HMSO London. ix + 172pp.
Swift A & D M Martill (eds) 1999. Fossils of the Penarth
Group. The palaeontological Association - field guide to fossils no. 9. 312pp.
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