The Palaeogene Yamak sand-rich submarine-fan complex, Haymana Basin, Turkey

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The Haymana Basin is a constituent trough of the Central Anatolian Basin, which was the site of rapid subsidence and accompanying flysch sedimentation during the late Cretaceous and early Tertiary, following closure of the Vardar Ocean and collapse of the carbonate platform forming its southern border. The Eocene Yamak Formation (maximum thickness, 1210 m) abruptly succeeds fine-grained sediments of the Bahçecik Formation, interpreted as a basin-plain facies. Lutite interbeds from the Yamak yield a bathyal marine microfauna and the Formation is characterised by a high proportion of thick medium to coarse sandstones and pebble-to cobble-rudites of turbidite and mass-flow origin, arranged in thick packets of moderate lateral extent. Many of these sand bodies are channelised, with thinning- and fining-upward sequences in which thick amalgamated sandstones and rudites are prominent. Most of the subordinate thickening- and coarsening-upward sequences are erosively succeeded by channelised bodies. These features indicate that the coarse Yamak sediments were deposited in a sand-rich submarine-fan complex in which the channelised mid-fan was the dominant depositional regime. The lateral and vertical relationships of Yamak facies associations indicate that the individual fans were relatively small, elongate and strongly channelised. They show little evidence of lateral migration or coalescence, but apparently result from superposition of successive low-sinuosity channels with only occasional development of channel-mouth “lobes” (in the sense of Mutti and Ricci-Lucchi, 1972, 1975). Facies distributions and palaeocurrent evidence show that sediment was generally conveyed to south and southeast through the Yamak fan system. However, following a prolonged phase of quiescence on the fan and formation of an extensive blanket of purple muds, the uppermost Yamak is marked by northwards progradation of a new channelised fan system.