Abstract: Holocene Epoch Alluvial-Deltaic-Coastal Sedimentary-Facies Patterns in Graben Embayments in Southern Greece

John C. Kraft, George Rapp, Jr., Stanley E. Aschenbrenner

A large number of borings has been made into sediments on alluvial-deltaic coastal plains forming at the head of deep marine graben structures in Peloponnesus, southern Greece. Sedimentation at the heads of the grabens accompanied rise in sea level from its low stand during the Wurm glaciation. Radiocarbon dates enable proper correlation of the resultant sedimentary environmental lithosomes in time and space. In all places relatively rapid sea-level rise in early-middle Holocene time led to a marine transgression over alluvial-deltaic sediments in the embayments. Shallow-marine sands and muds, including many marine Mollusca, Foraminifera, and Ostracoda, were encountered. As relative sea-level rise slowed down 6,000 to 3,000 B.P., sediments eroding from adjacent highlands began to infi l the embayments. Alluvial-deltaic flood plains, coastal swamps, and sandy barriers built seaward and upward. Resultant sedimentary environments migrated up to 5 km seaward. Sedimentary sequences up to 90 m thick have been encountered, showing an initial marine transgression, stillstand, and the present regressive sequence. Sedimentary environmental lithosomes are strongly controlled by the tectonic configuration of the embayments. Sediment types are highly varied, depending on the nature of the rocks being eroded in the upland areas. Some of the embayments are over 1 km deep and the potential for long-term sediment infill could lead to major stratigraphic units formed in a graben setting. Preliminary studies suggest that marine sedimentation also was occurring in larger grabens during t e Pliocene Epoch.

AAPG Search and Discovery Article #90961©1978 AAPG Annual Convention and Exhibition, Oklahoma City, Oklahoma