PRIVERKHOYANSK FORELAND BASIN (EASTERN SIBERIA): INTERACTION BETWEEN FOLD-THRUST BELT TECTONICS AND SEDIMENTARY SUPPLY

The study area is located on the eastern margin of the Siberian Craton, in the northern part of the Priverkhoyansk foreland basin near the front of the Verkhoyansk fold-and-thrust belt (FTB). Folding in the Verkhoyansk FTB is a result of late Mesozoic collision between the Siberian craton and the Kolyma-Omolon superterrain.

The main phase of Verkhoyansk FTB uplift occurred from Valanginian to Late Cretaceous, causing development of the foreland basin with a nonmarine sedimentation. Several thousand meters of sediments accumulated in nonmarine environments from the Valanginian to Aptian (Albian?) during the filling in of the Priverkhoyansk foreland basin. We subdivided this fluvial succession by categorizing rocks into two systems tracts, a low-accommodation systems tract characterized by amalgamated channel belts and a high-accommodation systems tract characterized by channel belts dispersed within fine-grained floodplain deposits. These systems tracts are considered to record variations between low rates of accommodation vs. sediment supply (low-accommodation) and high rates of accommodation vs. sediment supply (high accommodation). Variability in the amounts of available fluvial accommodation space was connected with decreases and increases of basin’s subsidence rate. This rate obviously connected with pulses of thrusting in the adjacent FTB. Provenance studies (sandstone petrographic studies, chemical and U/Pb detrital zircon data) show two main source areas for the Cretaceous clastic rocks, which include components derived mainly from the cratonward side of basin and, partly, from the FTB. Clastics were transported by a wide river system comparable with modern Lena River. Amount of clastic supply form both provenance areas varied significantly during filling in of the foreland basin.