TY - JOUR

T1 - Carbonate Sedimentology of the Upper Riphean (Neoproterozoic) Uk Formation, Southern Urals

AU - Dub, S. A.

AU - Grazhdankin, D. V.

N1 - Funding Information: This work was supported by the Russian Foundation for Basic Research, project no. 18-05-00062. Publisher Copyright: © 2021, Pleiades Publishing, Inc.

PY - 2021/11

Y1 - 2021/11

N2 - Lithological characteristics and results of the lithofacies analysis of carbonate deposits in the most complete section of the Upper Uk Subformation of the Riphean stratotype (northern part of the Bashkir Anticlinorium, southern Urals) are presented. The subformation is divided into the following members or sequences (from the bottom to top): Yuryuzan, Medved I, Manaysu, and Medved II. The subformation bottom occurs at the base of a huge stromatolite buildup. The Yuryuzan member is characterized by the thin-columnar branching stromatolites Patomella. The Medved I and Medved II members are represented mainly by bioherms consisting of the columnar-branching stromatolites Linella, interbiohermal rocks, and local packets of layered granular limestones found only in the lower member). The Manaysu member comprises layered (mainly cyclic) deposits with abundant molar tooth (MT) structures. The growth of the Yuryuzan member stromatolites occurred most likely in the upper subtidal-peritidal zone within the inner carbonate ramp under the influence of siliciclastic-bearing currents. Stromatolite buildups in Medved I and Medved II members were formed as a part of wide facies belts below the normal wave base (inner/middle ramp boundary) but within the photic zone. Layered limestones in the Medved I member are periodic storm current deposits. Environments of the inner ramp and upper middle ramp dominated during the deposition of Manaysu sediments with signatures of the influence of normal and storm waves. The sequence including the upper part of the Lower Uk Subformation, as well as the Yuryuzan and Medved I members of the Upper Uk Subformation, reflects a progressive deepening of the basin. The later slowdown in the rate of sea level rise (or fall) fostered the change in facies and the formation of the shallow-water Manaysu member. Subsequently, the transgressive trend appeared again, resulting in the formation of Medved II member. The upper boundary of the Uk Formation corresponds to a major break in the geological record associated with global glaciation.

AB - Lithological characteristics and results of the lithofacies analysis of carbonate deposits in the most complete section of the Upper Uk Subformation of the Riphean stratotype (northern part of the Bashkir Anticlinorium, southern Urals) are presented. The subformation is divided into the following members or sequences (from the bottom to top): Yuryuzan, Medved I, Manaysu, and Medved II. The subformation bottom occurs at the base of a huge stromatolite buildup. The Yuryuzan member is characterized by the thin-columnar branching stromatolites Patomella. The Medved I and Medved II members are represented mainly by bioherms consisting of the columnar-branching stromatolites Linella, interbiohermal rocks, and local packets of layered granular limestones found only in the lower member). The Manaysu member comprises layered (mainly cyclic) deposits with abundant molar tooth (MT) structures. The growth of the Yuryuzan member stromatolites occurred most likely in the upper subtidal-peritidal zone within the inner carbonate ramp under the influence of siliciclastic-bearing currents. Stromatolite buildups in Medved I and Medved II members were formed as a part of wide facies belts below the normal wave base (inner/middle ramp boundary) but within the photic zone. Layered limestones in the Medved I member are periodic storm current deposits. Environments of the inner ramp and upper middle ramp dominated during the deposition of Manaysu sediments with signatures of the influence of normal and storm waves. The sequence including the upper part of the Lower Uk Subformation, as well as the Yuryuzan and Medved I members of the Upper Uk Subformation, reflects a progressive deepening of the basin. The later slowdown in the rate of sea level rise (or fall) fostered the change in facies and the formation of the shallow-water Manaysu member. Subsequently, the transgressive trend appeared again, resulting in the formation of Medved II member. The upper boundary of the Uk Formation corresponds to a major break in the geological record associated with global glaciation.

KW - Bashkir Anticlinorium

KW - carbonate ramp

KW - facies

KW - MT structures

KW - stromatolites

KW - tempestites

KW - Upper Riphean

UR - http://www.scopus.com/inward/record.url?scp=85119107180&partnerID=8YFLogxK

UR - https://www.elibrary.ru/item.asp?id=47526152

U2 - 10.1134/S0024490221060031

DO - 10.1134/S0024490221060031

M3 - Article

AN - SCOPUS:85119107180

VL - 56

SP - 487

EP - 508

JO - Lithology and Mineral Resources

JF - Lithology and Mineral Resources

SN - 0024-4902

IS - 6

M1 - 2

ER -