CYCLICITY IN THE MIDDLE EOCENE YAMAK TURBIDITE COMPLEX OF THE HAYMANABASIN, CENTRAL ANATOLIA, TURKEY

The Haymana basin in central Anatolia (Turkey) formed on a Late Cretac eous to Middle Eocene fore-are accretionary wedge. A sequential model is proposed for the 1-km-thick Lutetian Yamak turbidite complex (YTC) which is the youngest paleotectonic unit of the basin. The YTC represe nts a prograding submarine fan subdivided into three depositional sequ ences (DS), each several hundred meters thick. Each depositional seque nce consists of a turbidite system (TS), with sandstone and conglomera tic sandstone beds alternating with mudstones, overlain by basin plain mudstones. In each turbidite system, the sandstone and mudstone seque ntial organization allows the distinction of smaller subdivisions, nam ely, basic sequences (BS) and basic units (BU), with each basic sequen ce being composed of several basic units. This subdivision, associated with a two-dimensional geometric reconstruction of the YTC, leads to a better understanding of the evolution in time and space of the subma rine fan system. Lower to middle fan depositional lobes, and upper fan and slope channels, are represented. As a whole, the YTC progressed f rom a sand-poor to a sand-rich system. Depositional sequences (DS) of the YTC may correspond to third-order sea-level cycles of tectonic ori gin. Accordingly, fourth- and fifth-order cycles might be proposed for the BS and BU, respectively. However, partly because of the limited e xtent of exposures, the allocyclic origin of these finer subdivisions remains problematic.