Sedimentary dynamics on isolated highs in Lake Baikal: evidence from detailed high-resolution geophysical data and sediment cores

摘要

High- and very-high-resolution seismic data, side-scan sonar mosaics and piston cores from three isolated highs in Lake Baikal (Vydrino Shoulder, Posolsky Bank, Continent Ridge) have allowed to document in unprecedented detail the depositional, re-depositional and tectonic processes and to characterise the overal sedimentary environment on such isolated highs. Our data show that Vydrino Shoulder actually represents a turbidity- or underflow-sourced slope fan, with a distinct channel-levee morphology, and affected by tectonics and stratigraphic unconformities. Sediment cores contain up to 90% of terrigenous material. Posolsky Bank is a major tilted fault block, clearly affected by tectonic activity, by stratigraphic unconformities and by mass wasting along its margins. Sedimentation on its crest is undisturbed, but average sedimentation rates are high due to the influence of the nearby Selenga River. Continent Ridge is also affected by active faulting, stratigraphic unconformities and by mass-wasting along its flanks. The area receives only 30% of terrigenous input. There are no signs of sediment reworking due to bottom-currents. Our study thus shows that in comparison with other environments in Lake Baikal, the isolated highs probably hold the best potential to contain a high-quality, continuous, undisturbed and undiluted sedimentary record suitable for paleoclimate research.