--> Abstract: Structure and Late Mesozoic – Early Cenozoic Evolution of the Verkhoyansk and Olenek fold belts (Laptev Sea shore) Junction Z, by Andrei Prokopiev; #90177 (2013)

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Structure and Late Mesozoic – Early Cenozoic Evolution of the Verkhoyansk and Olenek fold belts (Laptev Sea shore) Junction Z

Andrei Prokopiev

The Olenek fold belt (FB) and the adjacent Lena-Anabar depression located along the northern margin of the Siberian platform, have a NW trend and are filled in with Permian and Mesozoic rocks. From drilling data, underlying rocks range in age from Carboniferous to Mesoproterozoic. The surface structure is simple with predominance of 10-15 km wide folds. Large thrusts are rare, cleavage is absent. According to gravimetric modeling and interpretation of seismic profiles, two detachment surfaces bounding the duplex structure have been identified. They are the floor thrust at the base of the Mesoproterozoic succession and a roof thrust confined to ductile beds at the base of the Upper Paleozoic terrigenous complex. The main tectonic event is related to Mesozoic compressive deformation. Its beginning is inferred by transformation from marine to continental sedimentation that occurred in the Early Cretaceous. Apatite fission track (AFT) data points to events that occurred in Aptian-Albian and Maastrichtian-Paleocene. The latter is better expressed and we interpret it as the main deformation with correspondent uplift and erosion. The Olenek FB is likely represent a deformed foredeep of a major orogenic belt located in the north, in the Laptev Sea area. Post-Paleocene evolution is related to some fracturing and normal faulting. The Verkhoyansk FB has a N trend and contains rocks ranging in age from Jurassic to Mesoproterozoic. A set of Cenozoic mainly N-trending grabens occurs in the northern part of the Verkhoyansk FB. Cretaceous orogeny mainly formed modern structural style of the Verkhoyansk FB and the Priverkhoyansk foreland basin where occurrence of a buried thrust front with triangle zones is assumed. Several stages of Cretaceous compressional deformation are established. The first evidence for orogenic event in the Verkhoyansk FB came from the abrupt transition from marine to fluvial sedimentation that occurred in Early Valanginian. Several thousand meters of sediments accumulated in nonmarine environments from the Valanginian to Aptian (Albian?) during the filling in of the Priverkhoyansk foreland basin. However, AFT data shows that at least 2-3 km of sediments were eroded. Formation of the first two generations of D1 and D2 folds and major displacements are related to the main compression and uplift event inferred from AFT data as Albian to Santonian. In the northern Verkhoyansk FB N-trending folds are deformed by NW-trending folds and cleavage. The strike of the latter structures is the same as in the Olenek FB. AFT data points to younger events that occurred in the Campanian–Paleocene. These relationships show that structures of the Olenek FB overprint those of the Verkhoyansk FB. A post-compressional extension event led to the formation of normal faults and grabens filled in with Cenozoic sediments. The study was partly supported by TGS-NEOPEC Geophysical Company and RFBR grants 13-05-00700 and 12-05-33018.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013