| A Sand Source: Offshore Point Platten - Gray fluvial Pleistocene Prairie Formation sediments overlain by transgressive sands. Pre-existing Pleistocene sediments eroded and served as a source of shoreline sand, allowing the formation of protective beaches. B Mechanism: Nearshore Goose Point - Holocene marsh deposit overlain by transgressive beach sand. Once a back beach protected marsh, it was overwashed by a retreating beach during a storm event. This retreat mechanism allows the maintenance of a beach in a subsiding environment, which in turn protects the interior marshes. C Result: Inland within the Bayou Lacombe incised valley - Coarse basal valley sub-stratum grades up into a thick black marsh deposit. The inland marshes flourished relatively uninterrupted behind the line of beaches to the south. | 
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