Tectonic and sediment supply control of deep rift lake turbidite systems: Lake Baikal, Russia

Tectonically influenced half-graben morphology controls the amount and type of sediment supply and consequent type of late Quaternary turbidite system s developed in the active rift basins of Lake Baikal, Russia. Steep border fault slopes (footwall) on the northwest sides of half-graben basins provid e a limited supply of coarser grained clastic material to multiple small fa n deltas. These multiple sediment sources in turn laterally feed small (<10 km diameter) unchannelized sublacustrine sand-rich aprons that are deposit ed at the slope base on the lake poor Gradual slopes of the southeastern ra mp margins (hanging wall) of the lake basins, conversely, feed finer graine d sediment from larger drainages into two different types of channelized tu rbidite sublacustrine fan systems: (1) small (5-20 km) laterally fed sand-r ich fans sourced by local rivers, often originating from glaciated valleys; and (2) large (>65 km) axially fed elongate mud-rich fans sourced by regio nal exterior drainage of the Selenga River that supplies large quantities o f silt. Basin plain turbidites in the center of the linear basins and axial channels that are controlled by rift-parallel faults are fed from, and int erfinger with, aprons and fans. The predictability of the turbidite systems in Lake Baikal provides the best example yet studied of how tectonics and sediment supply interact to control the development of a wide variety of co eval turbidite systems on a single basin floor.