Penllergaer Railway Cutting
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Geology & landscape
Geological Feature: Floodplain · Geological Period: Carboniferous
Landscape processes: Fluvial
Description
Description The best exposure of the late Westphalian D (Carboniferous) Grovesend Beds in South Wales. This interval of strata is of interest since it represents a period of relative calm between the Leonian (middle Westphalian D) pulse of tectonics and the major Stephanian phase of uplift (Asturian) which caused Carboniferous sedimentation to cease finally in Britain. The Penllergaer section well illustrates this period of relative quiescence, being dominated by floodplain shales, with period incursions of lake deposits containing numerous ‘estheriid’ crustaceans. This is in marked contrast to the much higher energy fluvial environments represented by most of the other Pennant Measures sequences, which are dominated by sandstones. An important site for understanding the development of the South Wales coal-basin.