The India–Asia collision in north Pakistan: Insight from the U–Pb detrital zircon provenance of Cenozoic foreland basin

Abstract

The northernmost exposures of sub-Himalayan Cenozoic strata in the Hazara–Kashmir syntaxial region of north Pakistan comprises the Paleocene–Eocene marine strata in the lower part and Oligocene–Miocene nonmarine strata in the upper part. This study provides the detrital zircon U–Pb geochronology of the Cenozoic strata in this area. The strong resemblance of U–Pb age spectra of Paleocene Hangu, Lockhart and Patala formations with those of Himalayan strata indicate an Indian plate provenance. The first appearance of <100 Ma detrital zircon U–Pb ages within the lower most part of the Early Eocene Margalla Hill Limestone indicates a shift from an Indian to Asian provenance. Geologic mapping shows the existence of a disconformity between the lower and upper most part of the Patala Formation, which is interpreted to have been formed by the migration of a flexural forebulge through this region. We consider the upper most part of the Patala Formation to have been deposited within the distal foredeep of the foreland basin. The Indian to Asian provenance shift and the presence of a possible foreland basin forebulge provide strong evidence that India–Asia collision was underway in northern Pakistan at ca. 56–55 Ma.