Linking Structural Restoration and Thermochronology to Decode the Deformation and Exhumation History in the Western Kohat Fold and Thrust Belt, Pakistan

This research focuses on the northwestern segment of the Himalayan foreland belt in Pakistan, the Kohat Fold and Thrust Belt (KFTB), where the style and sequence of deformation since the Miocene differ significantly from the rest of the Himalayas (Robinson et al., 2023; Ghani et al., 2018). Sequentially restored balanced cross-sections, integrated with apatite (U-Th-Sm)/He (AHe) thermochronology, are employed to jointly interpret the deformation history and exhumation pattern in the study region. The preliminary results show that the resetting age of AHe is late Miocene-Pliocene and Pleistocene in the northern and central KFTB respectively, while they are partially reset in the Khisor Ranges the western part of the Range front. In the Surghar Ranges (the central part of the Range front) the ages appear as reset in early Miocene time which is older than the previously reported AHe age (Ghani et al., 2021).

These patterns suggest out-of-sequence deformation and high exhumation in the northern and northwestern KFTB. The variation in low-temperature thermochronological ages along strike in the central KFTB is likely due to salt-tectonics activity in the eastern Kohat and limited toward the western KFTB. The age constraints in the Range front (from Salt Ranges to Khisor Ranges) suggest shallow burial in the east and west and deep burial in the northern segment of the range front (along the Surghar Thrust).

The ongoing apatite fission track thermochronology will provide additional constraints on the spatio-temporal evolution of the region