Sequence organization and growth patterns of late Mesoproterozoic stromatolite reefs: an example from the Burovaya Formation, Turukhansk Uplift, Siberia

The latest Mesoproterozoic Burovaya Formation is a 600-1000 rn thick stroma tolite/mud dominated carbonate unit demarcated by an erosional unconformity into two subformations containing stromatolite reefs of variable size and geometry. The lower subformation consists of two distinct stratigraphic seq uences. The lower sequence records shelf to ramp evolution and includes sma ll-scale stromatolite reefs developed within an upper subtidal shelf settin gs at the transgressive systems tract and overlying mud-dominated highstand deposits accumulated in lower subtidal to peritidal environments. The seco nd sequence of muddy and fine-grained sediments makes up a lowstand systems tract and documents a progressive structural and environmental differentia tion of the Burovaya platform. The upper subformation records a third strat igraphic sequence. containing transgressive and highstand systems tracts re presented by reef-bearing and reef-cap facies complexes. The recf-bearing c omplex characteristic of the transgressive and the bulk of the highstand sy stems tracts contains a giant (20-25 km wide, 10 + km long, up to 550 in th ick) stromatolite reef and surrounding deep-water carbonate mudstones conta ining sporadic slump block deposits. The reef was located on the distally s teepened part of the ramp and contains distinct internal facies organizatio n defined by particular stromatolite microstructure and morphology and prev ailing environments. Late highstand development of the Burovaya platform wa s marked by the termination of reef accretion, infilling of basinal relief by shallow-water carbonate and shale sediments of the cap complex, and subs equent subaerial exposure. The history of the Burovaya reef is indicative o f the interplay between reef growth potential and platform geometry defined by regional tectonic and sea-level dynamics. (C) 2001 Elsevier Science B.V . All rights reserved.