Submarine Canyon, Slope, and Shelf Sedimentation in an Upper Eocene-Oligocene Progradational System (Limnos Island, North Aegean Sea, Greece)

Nicolas Roussos

The only well-exposed outcrops of a post-Alpine late Eocene-Oligocene basin in the north Aegean Sea are at Limnos Island. These mostly consist of typical slope deposits overlain by remnants of shallow marine shelf and continental (braided-river) deposits.

Three main slope lithofacies are distinguished. Canyon deposits consist of thick-bedded, massive, and pebbly sandstones (facies B), conglomerates (facies A), pebbly mudstone where the matrix shows flow (facies F), rock falls (nummulitic limestones), and zones of slump folds in sandstones (facies F). Channelized facies of massive sandstones, classical turbidites, and thin interbeds of sandstone and mudstone (facies E--probably overbank or levee deposits) are associated with canyon deposits. Pelagic and hemipelagic slope deposits consist of mudstone (facies G) and thin-bedded sandstone (facies D) with occasional small to medium-scale slump folds. These mud-rich slope deposits are incised by several channels filled with conglomerates, thick massive sandstones with well-developed dish str ctures, and turbidites interbedded with thin layers of mudstone (facies C). This unit composes a typical thinning and fining-upward sequence.

Some thickening-upward sequences may represent local crevasse-splay or fan deposits, but the limited outcrops do not allow positive identification. Microfauna and trace fossils indicate an inner to outer shelf and bathyal environment.

Different types of casts, flame structures, imbricated cobbles of both submarine and continental conglomerates, and slumps show a general northward or northeastward downslope sediment flow direction. Overall the Limnos Island upper Eocene-Oligocene exposures represent a typical slope depositional system that prograded toward the north or northeast.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.