Figure 11.  Schematic representations of estuary and shelf development through Holocene sea-level rise (transgression) in the northern Gulf of Mexico. Late Wisconsinan sea level is at shelf break. During this time, rivers incise the exposed shelf, and shelf-margin deltas are being deposited. As rapid sea-level rise floods the shelf relatively thin shelf-phase deltas are deposited and abandoned as sea level continues to rise. Sea-level slows (including stillstand and fluctuations) as it nears present levels, the abandoned shelf-phase deltas are reworked to form shoals, incised valleys are flooded to form estuaries with bayhead deltas, and longshore currents move sand to form modern barrier systems.

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