A multi-disciplined field-based study of sedimentary basin evolution along seismically active transpressional fault systems in the Mongolian Altai
thesisposted on 15.12.2014, 10:39 by James Peter. Howard
This PhD project documents processes controlling the generation, evolution and preservation of intracontinental transpressional basins, one of the least understood major basin types. Field data were collected in three actively deforming transpressional basins along the eastern margin of the Mongolian Altai. The Mongolian Altai is an active intracontinental mountain range comprising discrete ranges, uplifted by outward-directed thrust and oblique-slip faults linked to regionally extensive, dextral strike-slip faults. Between ranges numerous transpressional basins exist in various stages of their evolution. Thus the Mongolian Altai is an excellent natural laboratory for studying the origin and development of intraplate transpressional basins.;Analysis of Landsat TM imagery allows the identification of five interlinked sediment accumulation sites which control modern sediment transport, deposition and storage within the Altai region. At present, small sediment volumes exit the Mongolian Altai and the most significant sediment sinks are range flanking transpressional basins such as the Dzereg, Dariv and Shargyn basins. In these basins, strata are uplifted, deformed and exposed by active faulting and folding in internal zones and along internal zones and long basin margins. Mesozoic strata are confined to an elongate trough coincident with Cenozoic basins, suggesting Cenozoic basins are reactivated older depocentres. The upward fining and asymmetric thickness distribution of Mesozoic strata, and the presence of interpreted Mesozoic normal faults, suggest that the basins formed during Mesozoic extension or transtension.;Transpressional reactivation of the Altai began in the Oligocene, presumably in response to the distant Indo-Eurasian collision. Cenozoic strata coarsen upward and are dominated by alluvial sediment shed from adjacent ranges. Compartmentalised uplift and erosion of basin sediments and synchronous downslope sedimentation characterise the transpressional phase of basin evolution. Transpressional basins have variable bounding fault geometries and a low preservation potential.