Strand-line pebbles in the mid-hastings beds and the geology of the London uplands. Old red sandstone, new red sandstone and other pebbles. Conclusion

Abstract

London area sources contributed small proportions of red-stained siliceous pebbles to the various Ashdown, Lower Tunbridge Wells and Cuckfield conglomerates of mid-Sussex. Affinities are revealed with Old Red Sandstone sediments and pebbles in Old Red Sandstone conglomerates. Cataclastic rocks, suggesting a zone of Caledonian fracture, might be local. The New Red Sandstone is represented by multicycle pebbles from the Bunter. Lower Palaeozoic (?) and pre-Cambrian pebbles, though possibly derived directly from small inliers (especially the former), probably represent recycled Old Red and New Red materials. During the top Ashdown/top Cuckfield interval denudation apparently widened the Old Red and Kimeridge(-Oxfordian?) outcrops chiefly by reduction in their transgressive Lower Carboniferous and Portlandian covers. East Kent-North Sea sources supplied the Ashdown and Wadhurst pebble beds of eastern Sussex with unstained quartzose pebbles (Coal Measures?/Lower Palaeozoic?/pre-Cambrian?). Scarcity of Lower Carboniferous cherts and red-stained Devonian materials is explained by widespread Westphalian overstep and/or overthrust; that of New Red by Jurassic overstep. Outcrops of transgressive Portlandian, retreating south-west of the coalfield, were overstepped by Wealden after Ashdown times.