Structure and evolution of the underwater Akademichesky Ridge (Lake Baikal)

The Academichesky Ridge is an underwater segment of the interbasinal uplift that separates the younger North-Baikal basin, underlain with 42-44 km thi ck crust, and the older Central-Baikal basin (crust thickness 35 km). Studi es of the ridge may provide a clue for the structure and evolution of the B aikal Rift and for the history of paleoclimates. The ridge includes a north western (uplifted) and a southeastern (subsided) blocks. High-resolution si ngle-channel continuous seismic profiling of the northwestern block imaged two major units of its sedimentary cover, a Lower-Middle Miocene (A) and an Upper Miocene-Pliocene-Quaternary (B) sequences, separated by angular and azimuthal unconformity. The paleogeographic scenario of the ridge evolution based on these data sug gests that till the Middle Miocene it had been a land uplift bounding the C entral-Baikal basin. Later on, it became destroyed from aside and from abov e, but isolated isles of land persisted nearly as long as the late Pleistoc ene.