Print this pageControl of Late Quaternary Turbidite System Architecture in Lake Baikal
NELSON, C. HANS, KIM D. KLITGORD, MARC DEBATIST, EVGENY B. KARABANOV, and STEVEN M. COLMAN
Quaternary turbidite system architecture in Lake Baikal is controlled by tectonically influenced half-graben topography and bathymetry that affect the amount and type of sediment supply and consequent geometry of turbidite systems. Small footwall drainage areas of the steep western border fault provide a limited supply of coarse clastic material to numerous fan deltas on the footwall. These deltas laterally feed small (<10 km diameter) sublacustrine sand-rich apron wedges stacked against the base of the border fault. Gradual slopes of the eastern ramp and axial margins of the lake basins feed sand from larger drainages into laterally fed small (5-20 km diameter) sand-rich fans whose architecture is characterized by proximal channel-levee complexes and distal stacked lobes. Rivers from major external drainages transport sediment across rift segment boundaries to axially feed large (65 km) elongate silt-rich fans. The thickest turbidite sequences pond in linear basin plains and interfinger with aprons on the border fault margin or fans on the ramp and axial margins. The most sand-prone facies of the 1) basin plain are associated with apron fringes, distal fan lobes and fault-controlled axial channels and 2) basin-floor turbidite systems are associated with the aggradational stacked aprons along border faults, fan channel-levee complexes and progradational or retrogradational distal fan lobes. The architecture of lobe progradation and general turbidite system growth are controlled by climate change of glacial periods rather than by base-level change of water levels. The upper turbidite system sequence of apparent Quaternary age onlaps complex older architecture of the ramp margin, but continues the older architecture of stacked aprons on the border-fault margin.