Abstract:

Cretaceous marine strata are well exposed in Gamba, southern Tibet, and the study of which may provide abundant information about the evolution of TibetTethyan ocean before the collision between Indian and Asian plates. This research carried out a detailed study on the Cretaceous fossil carbonate microfacies of Gamba. Twelve types of microfacies (MF1MF12) and seven types of biofacies had been recognized. On the basis of these, the research made a preliminary discussion on the environmental evolution of TibetanTethys during Cretaceous, which could be concluded as follows: a transgression took place during the BarremianAptian; in the early of Albian, Gamba area was generally in a regressive environment; from the Late Albian to Cenomanian the seawater had a deepening trend; there was a big transgression which took place during the Turonian and lasted to SantonianConiacian; the seawater became shallow rapidly during the Maastrichtian.

Key words: TibetanTethys, Cretaceous, foraminifera, carbonate microfacies, sedimentary environment