Upper Maeotian-Lower Pontian "Transitional Strata" in the Taman Peninsula: stratigraphic position and paleogeographic interpretation

Abstract

Three sections (Taman, Popov Kamen, and Zheleznyi Rog) of the Upper Maeotian-Lower Pontian sediments of the Taman Peninsula (Eastern Paratethys) have been studied. The sequences represent continuous successions of the Maeotian and Pontian sediments. The transitional Upper Maeotian-Lower Pontian relatively deep-water sediments were formed at the time when Eastern Paratethys was connected with other marine basins. The facies are represented by thin clay layers interbedded with laminated diatomites and contain unusual diatom and nannofossil associations. The small size of coccoliths and the absence of zonal markers indicate that the influx of marine waters took place in the stressed conditions of a restricted basin. Diatom assemblages are more diverse and include the open-marine species Azpeitia aff. komurae and Thalassiosira maruyamica and marine endemics Actinocyclus aff. paradoxus, Rhizosolenia bezrukovii, Hemiaulus sp., Nitzschia miocenica of the tropical Nitzschia miocenica Zone and -the index species of next Thalassiosira convexa Zone appear in these part of the sections. Three stages of the Mediterranean marine invasion are distinguished; during the first one the connection between basins was rather permanent, for the two others its character became pulsing and not stable. The possible duration of the invasion is estimated from 6.4 to 6.1 Ma and belongs to the Early Messinian -to pre-evaporate deposits and lower part of lower evaporate deposits.

Middle-Upper Miocene stratigraphy of the Taman Peninsula, Eastern Paratethys

“…Rog section contains relatively deep-water sediments, whereas Taman and P. Kamen sections are composed of relatively shallow-water deposits. The composition and correlation of the sections was taken from [56], Fig. 3 with a supplement [18,22].…”

“…This assemblage also contains Coccolithus pelagicus, Discoaster sp., Lithostromation perdurum, Reticulofenestra sp., Rhabdosphaera sp., Syracosphaera pulchra, Syracosphaera sp., and Thoracosphaera sp. [56].…”

“…This permits the straightforward correlation of some regional zones with the units of the Mediterranean scale and with the oceanic diatom zonal scale as was shown for the Maeotian-Pontian Transitional strata [55,56]. The modern state of the art in studies of this group in the Eastern Paratethys can be defined as the stage of material accumulation.…”

“…Both the absence of zonal species and the very small size of coccoliths point to the restricted or out-of-strait connection with a marine basin of normal salinity. Together with typical marine diatoms [56] [31], and Biddulphia elegantula known from the Sarmatian [30]. Among dinocysts an extremely numerous oligo-dominant euryhaline assemblage consisting of Batiacasphaera and Operculodinium species together with Lingulodinium machaerophorum, occurs and continues into the lower part of the overlying Lower Pontian sediments.…”

“…The deposits from the Upper Maeotian to the lower part of the Lower Pontian are composed of thick clayey beds interbedded with laminated diatomite strata, over 60 m thick, that were named "Transitional strata" [56] (Fig. 4).…”