Structure,evolution and origin of Late Mesozoic extensional basins in the China-Mongolia border region

A broad extensional basin system developed in the China-Mongolia border region in Late Juras-sic-Early Cretaceous times,and was internally built up by a number of subbasins of various scales.The basin system experienced two stages of structural development.The first stage was characterized by wide occurrence of isolated small subbasins ,while the second stage was a period when the subbasins began to coalesce laterally.The linked subbasins gradually evolved into relatively large subbasins ,serving as main de-positional and subsidence centers of the basin system and exhibiting a ribbon-like shape in map view.In contrast,the subbasins in the stress shadow became inactive and dead as a result strain localization on the linked through-going basin-bounding faults.It is considered that the formation of the Late Mesozoic basin system bore upon extension in the shallow level of the crust,which arose dynamically from gravitational collapse of the crust beneath the China-Mongolia border region that had been overthickened by the pre-ceding compression.Some problems are accordingly raised that need further investigations in the future rele-vant studies.