Exploring the tectonostratigraphy of the Pakistan Himalaya with new detrital zircon geochronology and neodymium isotope data from the Kaghan Valley

Abstract

In the central Himalaya, the Greater and Lesser Himalayan tectonostratigraphic zones can be distinguished from each other by combining detrital zircon U-Pb ages and whole-rock Nd isotopic data. In the Hazara-Kashmir syntaxis of northern Pakistan, rock units in the Kaghan valley have been variously assigned to the Tethyan, Greater, and Lesser Himalayan zones. To determine which tectonostratigraphic zones are represented, we sampled across the Batal thrust in the northern Kaghan valley because this structure is identified in some research as the Main Central thrust. Samples from the footwall yield Paleo- to Mesoproterozoic maximum depositional ages (∼1.8–1.1 Ga) and an average ε_Nd(0) value of −14.3. Samples from the hanging wall yield Neoproterozoic maximum depositional ages (∼1000–600 Ma) and ε_Nd(0) values of −17.3. The contrasting detrital zircon ages show that the Batal thrust in the Kaghan valley is a major structural division. However, these data lack the characteristic detrital zircon age spectra and ε_Nd(0) values of Greater and Lesser Himalayan rocks north and south of the Main Central thrust in the central Himalaya, respectively. Therefore, either the Batal thrust is not the Main Central thrust, or the Main Central thrust in the Kaghan valley cuts a different structural level and carries rock units not seen outside the Hazara-Kashmir syntaxis.