Early Visean paleogeography of northern Siberia: New evidence of rift to drift transition along the eastern margin of Siberia.

In the Late Devonian-Early Carboniferous the eastern part of Siberia was affected by multi-stage rifting, which led to formation of a Late Paleozoic-Mesozoic passive margin. Four sections of the Lower Visean strata were studied in the northern part of the Kharaulakh Ridge, along the Lena River and Bykov Channel (north-east of Siberia). The studied sedimentary succession comprises two lithologically contrasting units: coarse-grained turbidites and hemipelagic cherts. Deposition occurred in a marine basin bounded by steep slopes, which is a key geomorphological feature facilitating deposition of coarse-grained turbidites. Within the studied sandy turbidites, several different zones of submarine sand-rich fans have been recognized. Integrated sedimentological and petrographical analyses allow us to interpret that the nearby uplifts composed of Proterozoic-Middle Paleozoic rocks were the main provenance areas for the Visean clastic rocks. Those uplifts were formed as a result of the latest stages of rifting in the study region that occurred in the earliest Visean, following termination of much of the tectonic activity during the Tournaisian. A similar rock association has been described previously from the central and southern part of the eastern margin of Siberia suggesting that the rift to drift transition occurred approximately at the same time across East Siberia and is of Early Visean age. [ABSTRACT FROM AUTHOR]