Deformation and provenance of Mesozoic strata in eastern Taimyr, Arctic Russia

The Taimyr region is dominated by a NE-SW trending compressional belt that has traditionally been divided into 3 NE-SW trending terranes bounded by SE vergent thrusts. The southern terrane represents the deformed Ordovician through mid-Carboniferous shallow marine, carbonate-dominated shelf succession of Siberia, overlain by a package of late Carboniferous through Early Triassic shallow-marine and continental siliciclastic rocks eroded from the developing Uralian collision belt to the north and west. The central terrane also has Siberian affinities and contains the Paleozoic continental slope sediments; these are underlain by a Neoproterozoic arc complex that was accreted to the Siberian margin at the end of Precambrian time. The northern terrane contains Precambrian-Early Paleozoic metasediments that have affinities with Baltica. It is the collision of the northern terrane with the central/southern terrane that represents the Uralian deformation event (sensu stricto) in Taimyr, and the presence of numerous collisional granites of Permo-Carboniferous age in north-central Taimyr provides evidence of this event. However, structures formed coincident with the Late Paleozoic event are less easy to demonstrate and in southern Taimyr the main folding episode is demonstrably latest Triassic.

Throughout all of northern/central Taimyr and most of southern Taimyr, patches of undeformed, poorly consolidated Jurassic and Cretaceous sediments rest unconformably on deformed older rocks. Mineralogical data from northern Taimyr indicate that these post-orogenic strata have very local provenance, and thermochronometric data provide valuable information about their pre-depositional history. Only in the southeasternmost part of Taimyr adjacent to the Laptev Sea are Jurassic (and possibly Cretaceous) rocks folded and well consolidated. The cause of this later deformation, and its relationship to earlier deformation phases, remains to be fully resolved.

A NW-SE traverse along the Chernokhrebetnaya River (Black Ridge River) and its tributaries in southeast Taimyr was undertaken in 2010. This traverse exposes a relatively complete section of Paleozoic through Mesozoic strata repeated on the limbs of two large-scale anticlines. The northern fold core exposes a Devonian-Carboniferous carbonate platform succession overlain by a Permian-Triassic clastic succession. The southern fold core exposes a Permian to Jurassic clastic succession. Comparison of the style, intensity and timing of deformation affecting the two anticlines provides information on the relationship between the latest Triassic and post-Jurassic deformation phases in southeast Taimyr.