Early Cretaceous Topography of the Transbaikalian Rift System

A quantitative model of the Early Cretaceous topography of the Transbaikalia Rift System has been obtained using the paleotopographic method. It is shown that in the Neocomian the system was an upland bordered by alluvial and lake plains of South-Aldan, Baikal region, Upper-Amur, and East-Mongolian piedmont troughs in the north, northwest, and northeast. The highest absolute marks, 2,000–2,500 m, Cell into a band that crosses the upland between 52° and 56°N and which was the main watershed between northeastern and southwestern drains. Comparison of the Early Cretaceous topography with the modern one shows that most of morphostructures of the modern upland topography correspond to that of the Early Cretaceous, but their quantitative characteristics are not commensurate. Flabbiness of tectonic movements in the post-Early Cretaceous resulted in general levelling of topography and lowering the greatest part of the upland by some hundreds of meters. At the same time, in the band that is adjacent to the boundary and within Mongolia, the upland, vice versa, was elevated by 500 to 1,000 m. This elevation seemed to be the reason that the southwestern drainage stopped and joined the Pacific and Arctic Oceans.