This study reports the detrital zircon U–Pb ages of the post collisional Chitarwatta Formation, exposed along the western margin of the Indian plate at the Sulaiman fold–thrust belt (SFB), Pakistan. The Chitarwatta Formation overlies the shallow marine carbonate sequence of the Kirthar Formation and represents an Oligocene–Miocene transitional marine sequence. The sequence consists of sandstone, siltstone, and mudstone. The sandstone consists predominantly (79–82%) of quartz grains. The framework grains are sub-angular to sub-rounded and show recycled orogenic provenance. The detrital zircon U–Pb age data show the dominant population between 390 Ma and ~1100 Ma, which is ~70% of the total population. In addition to this, a significant percentage of the younger detrital ages exist between ~40 Ma and ~120 Ma. This younger age cluster indicates the northern sources, including the Kohistan–Ladakh arc (KLA) and Karakoram block (KB), whereas the provenance for the 390–1100 Ma detrital zircon is likely the Higher Himalaya (HH), with contribution from Tethyan Himalaya (TH). This post-collisional scenario suggests that the Chitarwatta Formation received detritus from the northern sources through a drainage system, named as the Indus drainage system. A comparison with the coeval units in the north (Murree Formation, Dagshai Formation, and Dumre Formation) suggests that the sediments may have been delivered through the same drainage system that shares similar detritus. Relying on the contribution of the HH detritus, we propose that the HH uplifted during the Oligocene–Miocene along the Main Central Thrust (MCT) and provided detritus to the foreland basin.

Constraining the collision timing of India and Asia requires reliable information from the coeval geological record along the ~2400 km long collisional margin. This study provides insights into the India–Asia collision at the westernmost margin of the Indian Plate using combined U-Pb geochronological data and sandstone petrography. The study area is situated in the vicinity of Fort Munro, Pakistan, along the western margin of the Indian Plate, and consists of the Paleocene Dunghan Formation and Eocene Ghazij Formation. The U-Pb ages of detrital zircons from the Dunghan Formation are mainly clustered between ~453 and 1100 Ma with a second minor cluster between ~1600 and 2600 Ma. These ages suggest that the major source contributing to the Dunghan Formation was likely derived from basement rocks and the cover sequence exposed mainly in Tethyan Himalaya (TH), Lesser Himalaya (LH), and Higher Himalayan (HH). Petrographic results suggest that the quartz-rich samples from the Dunghan Formation are mineralogically mature and have likely experienced log-distance transportation, which is possible in the case of an already established and well-developed river system delivering the sediments from the Craton Interior provenance. Samples of the overlying Ghazij Formation show a major detrital zircon age clustered at ~272–600 Ma in the lower part of the formation, comparable to the TH. In the middle part, the major cluster is at ~400–1100 Ma, and a minor cluster at ~1600–2600 Ma similar to the age patterns of TH, LH, and HH. However, in the uppermost part of the Ghazij Formation, ages of <100 Ma are recorded along with 110–166 Ma, ~400–1100 Ma, and ~1600–2600 Ma clusters. The <100 Ma ages were mainly attributed to the northern source, which was the Kohistan-Ladakh arc (KLA). The ~110–166 Ma ages are possibly associated with the TH volcanic rocks, ophiolitic source, and Karakoram block (KB). The Paleozoic to Archean-aged zircons in the Ghazij Formation represent an Indian source. This contrasting provenance shift from India to Asia is also reflected in the sandstone petrography, where the sample KZ-09 is plotted in a dissected arc field. By combining the U-Pb ages of the detrital zircons with sandstone petrography, we attribute this provenance change to the Asia–India collision that caused the provenance shift from the southern (Indian Craton) provenance to the northern (KLA and KB) provenance. In view of the upper age limit of the Ghazij Formation, we suggest the onset of Asian–Indian collision along its western part occurred at ca. 50–48 Ma, which is younger than the collision ages reported from central and northwestern segments of the Indian plate margin with 70–59 Ma and 56 Ma, respectively.

This study reports on the detrital zircon provenance of the sandstones of Early Paleocene Ranikot Formation exposed in the Fort Munro section, Sulaiman fold-thrust belt, Pakistan. This marks the Cretaceous-Tertiary boundary sequence. The detrital zircon U-Pb ages reported are mainly clustered around ~460–1100 Ma, ~1600–1900 Ma and ~2300–2600 Ma. The age cluster ~460–1100 Ma is mainly matched well with the Tethyan Himalaya. However, the age clusters ~1600–1900 Ma and ~2300–2600 Ma matched fairly with the lesser Himalayas and Higher Himalayas. In addition, the sandstone petrography suggests the craton interior provenance. The two younger Cretaceous zircon ages may be derived from the Tethyan Himalaya volcanic rocks as supported by a high (>0.3) Th/U ratio. Furthermore, the absence of the ophiolitic component ~115–178 Ma suggests that the western ophiolite may be emplaced at the same time as Ranikot Formation deposited or later. Moreover, the absence of the Eurasian (zircon with ages <100 Ma) in the Ranikot Formation excludes the possibility of the early collision along the western margin, as reported in earlier studies.