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 ma rine influence. It occupies up to three interseam intervals in the eas t Pennine coalfield, England, and exceeds 50 m in thickness and 15 km in width at its maximum development, which is larger than many Westpha lian channel sand bodies. The high ash content of coal adjacent to the channel belt indicates that regional peat accumulation took place con temporaneously with the existence of the channel system. The major cha nnel system fed a number of minor channels during different interseam intervals, and conducted sediment and water into nearby delta plain la kes, via lacustrine delta and crevasse splay systems. These minor chan nels: which show a range of fills, are sub-parallel and show lateral o ffset stacking, suggesting that differential compaction was an importa nt control on their location. The major channel belt acted as a long-l ived distributary system that flowed towards the east, away from the o verall basin depocentre, with its position being controlled mainly by deltaic processes.