LITHOSTRATIGRAPHIC MATCHES OF MESO- AND NEOPROTEROZOIC STRATA BETWEEN SE SIBERIA AND SW LAURENTIA

Joint Russian-American geological expeditions found a long sequence of distinct lithostratigraphic matches of correlative Meso- and Neoproterozoic strata in the Death Valley, California, region and the Sette-Daban Range of SE Siberia. The regions plot within 200 km of each other on a Proterozoic paleocontinental reconstruction that connects the E margin of the Siberian craton to the SW margin of Laurentia (Sears and Price, 2003). The Crystal Spring and Beck Spring formations of the Death Valley region closely match the Aimchan, Kerpyl, and Lakhanda groups of Siberia. The Crystal Spring and Aimchan both rest on profound angular unconformities that truncate intrusives as young as 1.38 Ga. The basal Crystal Spring and basal Aimchan Group (Talyn Formation) comprise trough cross-bedded sandstone and pebble conglomerate that grade upward to red shale, overlain by pink and yellow dolomite with similar stromatolites (middle Crystal Spring and Svetlyi formations). In both regions the dolomite is sharply overlain by a decimeter-thick marker quartz-dolomite pebble conglomerate, followed by red shale and coarse, trough-crossbedded sandstone (upper Crystal Spring and Bik formations). Next, both regions have a section of yellow, blocky dolomite and grey-green and yellow shale (uppermost Crystal Spring and Muskel formations). In both regions the overlying unit is a distinctive dark-grey to black dolomite with very similar textural features (Beck Spring and Malgin and Tsipanda formations, and Lakhanda Group). Both have finely-laminated cyanobacterial mats, 3-5 m bioherms, roll-up structures, thick intraformational breccias, conophyton stromatolites, pisolites, and variegated shale-to-dolomite cycles. The lithostratigraphic matches suggest that the two regions formed part of a single intracratonic depositional system between 1.3 and 1.0 Ga. The continuity of the platform broke up during deposition of the Neoproterozoic Uy Group (Siberia) and Kingston Peak Formation (Death Valley), both of which accumulated in rift settings with mafic activity. Both sections are overlain by very similar latest Neoproterozoic to early Paleozoic miogeoclinal prisms, compatible with subsidence of conjugate rifted continental margins. Detrital zircon analysis of samples from matching horizons is in progress.