Paleomagnetism of Cretaceous red beds from Tadzhikistan and Cenozoic deformation due to India-Eurasia collision

Abstract

We have carried out structural and paleomagnetic studies in the Tadzhik depression in order to evaluate the main features of the Alpine tectonics of this area. About 340 cores from 43 sites of Lower Cretaceous red beds were sampled from four different localities in the basin and adjacent ranges. A well-defined component of magnetization (A) of normal polarity with high unblocking temperatures up to 650–670°C was isolated from all the sites. Another component of magnetization (B) with unblocking temperatures between 650 and 680°C was isolated from only fifteen sites; this component is bipolar. The fold test is positive for both components. We believe that component A was acquired during the Cretaceous long interval of normal polarity. Comparison with Eurasian reference data shows significant counterclockwise rotation of a locality close to the Pamir wedge ( R = 51 ± 5°) and another counterclockwise rotation from the inner part of the basin ( R = 15 ± 5°). No significant rotations are observed at the two other localities on the periphery of the Tadzhik basin.