SEDIMENTATION AND SUBSIDENCE PATTERNS IN THE CENTRAL AND NORTH BASINSOF LAKE-BAIKAL FROM SEISMIC STRATIGRAPHY

Comparison of sedimentation patterns, basement subsidence, and faultin g histories in the north and central basins of Lake Baikal aids in dev eloping an interbasinal seismic stratigraphy that reveals the early sy nrift evolution of the central portion of the Baikal rift, a major con tinental rift system. Although there is evidence that the central and northern rift basins evolved at approximately the same time, their sed imentation histories are markedly different. Primary sediment sources for the initial rift phase were from the east flank of the rift; two m ajor deltas developed adjacent to the central basin: the Selenga delta at the south end and the Barguzin delta at the north end, The Barguzi n River system, located at the accommodation zone between the central and north basins, also fed into the southern part of the north basin a nd facilitated the stratigraphic linkage of the two basins. A shift in the regional tectonic environment in the mid Pliocene(?) created a se cond rift phase distinguished by more rapid subsidence and sediment ac cumulation in the north basin and by increased subsidence and extensiv e faulting in the central basin. The Barguzin delta ceased formation a nd parts of the old delta system were isolated within the north basin and on Academic Ridge. These isolated deltaic deposits provide a model for the development of hydrocarbon plays within ancient rift systems. In this second tectonic phase, the dominant sediment fill in the deep er and more rapidly subsiding north basin shifted from the flexural (e astern) margin to axial transport from the Upper Angara River at the n orth end of the basin.