The Mastakh Section of the Tyung River – a New Type of Jurassic Marine Rocks in the Vilyui Syneclise

Abstract

The largest in the Jurassic, The Early Toarcian transgression in the eastern Siberian platform and its folded framing (Arctic superbasin regime, thalassocratic factor) was accompanied by extensive inversion of the arch of the Yakut buried uplift and the conjugate Tompo block to the east, as well as by the formation of volcanites of the Pliensbachian–Aalenian Kobyuma Suite (Pacific superbasin regime, geocratic factor). At the same time (the Danlap phase of tectonic activity) in the zone of junction of the Siberian platform and the Verkhoyansk fold–and–thrust belt (the Lena branch of the Priverkhoyansk foredeep), a key Early Toarcian clay horizon of the Vilyui syneclise was locally accumulating on a relatively steep paleo–slope. The horizon is lacking in the section of the Aldan branch of the foredeep, and near the northwestern boundary of the Vilyui syneclise (Tyung River basin) the Suntar Suite is found to transgressively overlie the carbonate base of the Upper Cambrian. The stratigraphic unconformity on the Tyung River is proved by new paleontological finds. The lack of Hettangian–Pliensbachian rocks and the fact that the Upper Cambrian carbonate base is transgressively overlain by the Upper Lias deposits permits establishing a new «Mastakh» type of the section of Jurassic marine rocks in the Vilyui syneclise.