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Research School of Geological and Geophysical Sciences, Birkbeck College & University College, Gower Street, London WC1E 6BT, UK
The Middle to Upper Oligocene Thari Formation sediments in central and southern Rhodes, Greece were deposited adjacent to an active thrust front. They consist of clast-supported massive to horizontally stratified conglomerates, massive matrix-supported conglomerates interbedded with ophiolitic sandstone, and silty mudstone forming lenticular, discontinuous beds with common erosional contacts. Debris flow, stream channel, sheet flood deposits and the high gravel to sand ratios (90: 10), suggest deposition by processes within a gravel-dominated braided alluvial system. Facies relationships demonstrate a clear proximal (NW) to distal (SE) variation across an alluvial fan. Provenance relationships based on 2400 clast counts show that the main constituents of the conglomerates in the north west area are rounded to well rounded pebbles and cobbles derived from an ophiolite sequence (80%) and include harzburgite, dunite, gabbro, serpentinite, and dolerite whilst the other major components, pelagic limestone and chert (20%), have an increasing importance to the south west of the area. These relationships suggest that the Thari Formation formed part of a flexural foreland basin-fill that developed adjacent to a deformed ophiolite stack eroded after early Paleocene to mid-Oligocene convergent tectonics.
