Late Quaternary geology of the Tunka rift basin (Lake Baikal region), Siberia, Russia

The objective of this research is to obtain a better understanding of the evolution of the Tunka rift basin, part of the Baikal rift zone, and how it relates to the overall geologic history of the region, particular for the Quaternary period. The tectonically active Baikal rift zone began forming over 50 million years ago and continues today. In the Tunka basin, during the Oligocene and Middle Pliocene, relatively weak tectonic disturbances took place and thick accumulations of organic-rich sands, silts, and clays were deposited in lacustrine–marshy subtropical environments. Tectonism increased between the Miocene and Pliocene and thick units of coarse alluvium and floodplain sediments were deposited. During the Late Pliocene–Quaternary, tectonism formed basins that are now filled with a variety of coarse clastic materials. Early and Middle Pleistocene sediments are poorly exposed, covered by widespread Late Pleistocene deposits. Three Late Pleistocene sedimentary facies dominate: boulder–pebble gravels (proluvial, glacial fluvial, and alluvial sediments), alluvial sand, and loess-like sediments with associated slope deposits altered by post-depositional wind erosion. The relationship between these complexes, including radiocarbon and other chronological data and fauna and flora remains, indicates that they began forming c. 70 000 yr ago. Paleosols, glacial deposits and cryogenic material indicate that at times the climate was cool or cold. During the early Late Pleistocene renewed tectonism took place causing increased deposition of coarse sediments. The middle Late Pleistocene deposits consist mostly of sandy, floodplain alluvium. By the end of the Late Pleistocene–Holocene, alluviation was reduced and replaced by a high degree of erosion and aeolian depositio

The early Upper Palaeolithic of the Tunka rift valley, Lake Baikal region, Siberia

This paper presents recent results of geological and archaeological research at Late Pleistocene sites in the Tunka rift valley (Lake Baikal region, southern Siberia), including new radiocarbon dating of the Palaeolithic layers at Bol'shoi Zangisan, Slavin Yar and Tuyana. The sites range in age from ?26 to 45 ka 14C BP and represent the earliest evidence of human habitation in the area. Numerous faunal remains have also been identified in the archaeological horizons from which palaeoenvironmental conditions can be reconstructed. These data also provide important new information about the age, context, and development of an early microlithic industry in the Tunka-Pribaikal'e region during the late Karginskii interstadial, attributed to Marine Isotope Stage 3 (MIS3). Although further research is needed to verify the reconstructed site age models, archaeological evidence recovered at Tuyana and Bol'shoi Zangisan represent among the oldest known occurrences of microcore-microblade technology in North Asi

State-to-State Rate Constants for the O(³<i>P</i>)H₂(<i>v</i>) System: Quasiclassical Trajectory Calculations

The rate constants of elementary processes in the atom–diatom system O(3P)+H2(v), including the processes of vibrational relaxation and dissociation, were studied using the quasiclassical trajectory method. All calculations were carried out along the ground potential energy surface (PES) 3A″ that was approximated by a neural network. Approximation data were obtained using ab initio quantum chemistry methods at the extended multi-configuration quasi-degenerate second-order perturbation theory XMCQDPT2 in a basis set limit. The calculated cross-sections of the reaction channels are in good agreement with the literature data. A complete set of state-to-state rate constants was obtained for the metathesis reaction, the dissociation and relaxation of the H2 molecule upon collision with an O atom. According to these data, Arrhenius approximations over a wide temperature range were obtained for the thermal rate constants of considered processes. Data obtained on the dissociation constants and VT relaxation of vibrationally excited H2 molecules can be used in constructing kinetic models describing the oxidation of hydrogen at high temperatures or highly nonequilibrium conditions