“Sedimentology and Provenance of Late Cretaceous and Cenozoic Sedimentary Basins: Southern and Western Mongolia.” 

Jobe Traywick

The Hangay Dome of central Mongolia is a complicated and poorly understood major intracontinental feature. The timing, rate, and extent of uplift of the Hangay Dome remain key questions within the geologic community. The use of stable-isotope paleoaltimetry can provide baseline for constraining timing of the surface uplift of the Hangay Dome. Stable-isotope analysis requires the sampling of appropriate rock facies and establishing the local, regional, and tectonic framework for sampling sites. In order to provide a geologic framework of basins where samples were taken for isotopic analysis, sedimentological and provenance analysis of nonmarine sandstones from intermontane basins flanking the Hangay Dome was conducted.  Late Cretaceous and Cenozoic strata were observed and sampled from the Naran Bulog Formation and Begger Noor Basin in south-southwestern Mongolia. Sedimentological analysis suggests deposition occurred in multiple depositional systems during the Late Cretaceous and Cenozoic at each field site, including: fluvio-related eolian systems, alluvial fan/proximal braided stream systems, sandy bed-load systems, low-energy fluvial plain systems, oxygenated lacustrine systems, and meandering fluvial systems. Provenance analysis suggested that localized topographic variations played a dominant role in the sources of sediments and basin types formed at each field area during the Late Cretaceous and Cenozoic. It is believed that Late Cretacious and Cenozoic deposition of uplifted continental basement sourced sediment took place in proximal, possibly strike-slip style, basins located at each field area; this is based on sandstone provenance and lack of evidence supporting extensional basin formation at the field sites.