FIELD MEETING – OGMORE BY SEA Oxford Geology Group have been over the bridge and into Cymru this Saturday (25th October 2014). Christine Whittingham led the group on a trip to the stunning coastline at Ogmore, South Wales. A good mix of members made up the field party from professional geologists to amateur enthusiasts. The group was fortunate to have both of the vice-presidents along to provide their usual share of classical witticism. While welsh OGG chairman provided a selection of welsh cakes to add to the cultural value. Heavily jointed carboniferous limestone is the oldest unit at this locality, showing an impressive selection of solitary corals, such as this photo of Caninia. Others weathering proud from the rock gave a clear 3 dimensional view of the horn like structure. Marine regression then exposed the limestone to form a series of small hills. Laterally discontinuous, the carboniferous limestone was cut by triassic conglomerates. Deposited during episodes of heavy rain in an otherwise arid landscape, large (up to 1-2m) clasts of the carboniferous limestone, are held in a red sandy matrix. Walking up section the carboniferous gives way to jurassic marginal facies, in an unconformity representing some 150+ million years! The group saw that these marginal rocks incorporated clasts of carboniferous limestone in another conglomerate, before moving into deeper environments of the Jurassic proper. With stomachs rumbling the group powered up a rise to a pub lunch, with the chicken curry being a solid choice. Refuelled, the afternoon treated the field party to the incredible succession of repeating limestone and shale units of the Blue lias. Forming towering and impressively layered series of cliffs, of particular interest was the large fault at the eastern end of the beach. Here a large offset places the units seen in the morning back up alongside the blue lias succession! The fault shows a large amount of deformation with higher units folded due to fault dragging and some of the deeper units showing ductile deformation. A spectacular end to a day that was blessed with weather booked to the minute! Interested in taking part in the next field meeting? For more information on the trip to see the oldest rocks Warwickshire has to offer including volcanics emplaced into Cambrian and Ordivician country rocks, check out the Oxford Geology Group website at: ogg.uk/#!field-meetings/c181p
Posted on: Sun, 26 Oct 2014 15:42:42 +0000
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