THE SILKSTONE ROCK (WESTPHALIAN-A) FROM THE EAST PENNINES, ENGLAND - IMPLICATIONS FOR SAND BODY GENESIS

The Silkstone Rock (Westphalian A, Langsettian) is a major multistorey channel sandstone formed in a delta plain environment with minimal marine influence. It occupies up to three interseam intervals in the east Pennine coalfield, England, and exceeds 50 m in thickness and 15 km in width at its maximum development, which is larger than many Westphalian channel sand bodies. The high ash content of coal adjacent to the channel belt indicates that regional peat accumulation took place contemporaneously with the existence of the channel system. The major channel system fed a number of minor channels during different interseam intervals, and conducted sediment and water into nearby delta plain lakes, via lacustrine delta and crevasse splay systems. These minor channels: which show a range of fills, are sub-parallel and show lateral offset stacking, suggesting that differential compaction was an important control on their location. The major channel belt acted as a long-lived distributary system that flowed towards the east, away from the overall basin depocentre, with its position being controlled mainly by deltaic processes.