BCS Earth Sciences Workshop: July 14-15, 2001
The field trip day had the objective of examining the sedimentary sequence exposed near Edale, Derbyshire. Starting at Windy Knoll, we examined the upper surface of the limestones, with the well-known elaterite deposit and the breccia-filled fissures. The next location was the face of Mam Tor: a turbidic sandstone sequence with numerous plant remains caught up in the flows. Strata exposed along Grindsbook Clough allowed examination of Namurian rocks from the Mam Tor Sandstone to the Kinderscout Grit. These sediments were recognised as representing a variety of depositional environments. Channelling is present in the sequence, and a fine channel complex was examined below the scarp face of Nether Tor. Since there were no evidences of any long periods of time, the whole sequence was interpreted within a catastrophist setting. This involved rapid uplift and erosion of metamorphosed rocks in Scotland and mega-scale transportation of erosion products southwards.
The first presentation of the seminar day concerned polystrate lycopod trees in a variety of Carboniferous deposits. Most of these were in open-cast coal mines, but there was also a detailed look at the Fossil Grove in Victoria Park, Glasgow. This led to a wide-ranging discussion of the depositional environments associated with these trees, the “floating forest” model developed by Joachim Scheven in Germany, and the case against conventional “peat bog” models of coal formation.
David Tyler gave a field trip report of the Carboniferous limestones of Anglesey. This sequence provides some very striking examples of karstic surfaces: sea stacks, collapse structures and particularly pot holes. These evidences were discussed by reference to a recent paper on karstic features in the rock record that appeared in EN Tech J. Reference was also made to the relationship between the Anglesey limestones and others in N. Wales.
Richard Johnston introduced several topics for discussion with a view to future research. The questions arose from trying to relate the Biblical and geological evidences, particularly as regards a) the apparently late appearance of "higher" plants and animals, b) timescales, and c) the location of Noah's Ark. Richard was particularly concerned with two questions:
- How applicable is the European Geological Column to parts of the world that were above sea level after the Precambrian?
- Why does there appear to be a correlation between lithology and fossil type? The assignment of particular lithologies and their associated fossil contents to particular geological periods is a well established convenience. It is suggested that there is therefore a need to assess the relationship between rock types and the fossils they contain, and to correlate these combinations with specific environmental conditions and general contexts which gave rise to them. This would make explicit any systematic (but spurious) correlation that may exist between certain "geological periods" and the nature of the formative environment.
Paul Garner reported on a field trip he had to the Precambrian sediments of Charnwood Forest, Leicestershire. This led to a discussion of Late Precambrian environments and the significance of the unique Ediacaran fauna.