Lower Carboniferous Submarine Fan Deposits, Lena River Delta (North-East Siberian Craton)

Ershova, Victoria ¹; Khudoley, Andrei K. ¹; Prokopiev, Andrei V. ²
(1)department Dynamical & historical geology, Saint Petersburg State University, Saint-Petersburg, Russian Federation. (2) Diamond and Precious Metal Geology Institute, Siberian Branch, Russian Academy of Sciences, Yakutsk, Russian Federation.

Study area is located on the northeast margin of the Siberia Craton. Succession of the Lower Carboniferous (Visean) deposits overlies Tournaisian limestones with stratigraphic gap at the base. Visean deposits of study area are mainly represented by chert beds up to 50 m thick. Only in several localities sandy and conglomeratic turbidities successions up to 250 m thick are observed. Detailed study of coarse-grained turbidities was done in the Krestiakh Cape. Studied section can be subdivided into three units. Unit 1 and Unit 2 are represented by poorly sorted graded beds. Sandstones of Unit 2 mostly consist of sandstones and siltstones and more fine-grained while graded beds of Unit 1 usually contain small pebble conglomerates at the base.

Unit 1 is interpreted as gravity mass flow, deposited rapidly from suspension by high-density turbidity currents, while turbidities of Unit 2 were deposited in the distal part of submarine fan. Thickness of Unit 1 ad Unit 2 is up to 200 m.

Unit 3 is the coarsest part of succession up to 45 m thick. The lower part is represented by very coarse to medium-grained sandstones with lenses of conglomerates. These sandstone beds are interpreted as sand-rich feeder channels migrating over the surface of the fan. The upper part of Unit 3 consists of grain-supported conglomerates up to 15 m thick. This unit can be explained as filling of submarine canyon.

The formation of sand-rich submarine fans is usually related to tectonic activity. The main rifting event occurred in the eastern part of Siberia Craton at the end of Devonian (Franian-Famenian). Probably deposition of Visean sandy-turbidities corresponded to latest stage of Middle Paleozoic rifting of Siberia Craton. The rift-dominated phase resulted in uplifted shoulders, steep topography and intense sediment input. The northern part of Siberia shelf was incised by several submarine valleys during Visean. Fluvial systems associated with this sandy-rich submarine fan probably characterized by relatively steep slope gradients. Coastal plain was likely narrow and located close to mountains. Study area is seemed to be a local uplift related to short episode of tectonic activity.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.