SEDIMENTATION IN A MEANDERING ESTUARY1

Authors


  • 1

    Contribution No. 78 of the Marine Institute of the University of Georgia, Sapelo Island, Ga. (U.S.A.).

  • Marine Institute and Department of Geology of the University of Georgia, Sapelo Island and Athens, Ga. (U.S.A.)

SUMMARY

Sand is being deposited in a meandering estuary separating Sapelo and Blackbeard Islands, Georgia, in the channel of the estuary and on two point bars associated with meanders. Sand is being eroded by the meandering channel from slightly lithified Pleistocene and unconsolidated Holocene strandline deposits, and is being redeposited by the ebb tidal currents. The estuary-channel deposits are coarse grained and their grain-size decreases down ebb current from the source outcrops. The point bars are elongated in the direction of the ebb current, and increase in grain-size from their crests downward as they grade into the channel deposits. Festoon cross-bedding and ripple marks on the point bars record the ebb direction, while elongate plant fragments are preferentially oriented normal to the bar elongation (current). Horizontally stratified muds and muddy sands are being deposited behind the bars, and contain a rich fauna (primarily annelids, arthropods, and molluscs). However, the fauna is represented in the deposits more by burrows and disturbed stratification than by preserved organisms. The sands of the bars and channel are biologically less productive, but the bioclastic content of the sediment is high.

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