Sequence stratigraphy of the Cretaceous strata in the Tethyan Himalayas

The Cretaceous period is believed to be an important stage in the evolution of the Neo-Tethys. The sediments rested on during this period recorded the early evolution of the Neo-Tethys. The detailed outcrop sequence stratigraphic analysis has been made for the Cretaceous strata in the southern and northern subzones of the Tethyan Himalayan zone on the basis of the examination of the representative sections in combination with the pre-existing data. The following sequences have been distinguished:twenty-four third-order sequences, five sequence sets (subsecond-order sequences), two second-order (mesosequences) for the southern subzone, and twenty-two third-order sequences, five sequence sets (subsecond-order sequences) and two second-order (mesosequences) for the northern subzone. In the Tethyan Himalayas, the Early Cretaceous strata display an overall transgressive retrogradational sequence, representing a spreading phase of the Tethyan oceanic crust, whereas the Late Cretaceous strata display an overall regressive progradational sequence, representing a steadily collapse of the Tethyan oceanic basin and long-period falling of sea level, and thus should be assigned to the products created during the subduction phases of the Tethyan oceanic crust. Collectively, the well-defined transgressive-regressive cycles of the Cretaceous strata recorded the transition from the spreading to the decrease of the Tethyan Ocean. These evidences are in general agreement with the coeval global sea-level changes.