Formation of Holocene sedimentary laminae in the Black Sea and the role of the benthic flocculent layer

Holocene Black Sea sediments recovered in 1988 and 1993 from box cores and gravity cores were analyzed geochemically, microscopically, and with backscattered electron imagery (BSEI) in order to determine the temporal, geochemical, and sedimentological relationships between the benthic flocculent layer (often referred to as the fluff layer) and the formation of underlying laminated unit I sediments. Existence of a permanent benthic fluff layer in the Black Sea basin is suggested, acting as a geochemical transition layer within which all sedimentary particles are hydraulically sorted and particles subject to dissolution or organic remineralization are altered prior to accumulation We propose that particle residence time within the benthic fluff layer is a key factor in determining sedimentary microfabric and geochemical composition of laminated unit I sediments. We present a schematic model depicting the above relationships and use it to propose a paleoflux scenario for laminae formation in the unit II sapropel.