topset bed
Quick Summary
Topset beds are nearly level layers of sediment deposited on the top of a delta. These layers are part of the larger deltaic stratigraphic sequence, which also includes foreset and bottomset beds. Grove K. Gilbert first described this sequence in his 1890 report on Lake Bonneville, observing that topset beds are deposited in various sub-environments of the subaerial delta plain. These beds are almost horizontal and are found at the highest elevations within the delta's depositional structure.123
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