The India-Asia collision along the western Indian Plate margin remains debated, with contrasting models for the first arrival of Asian-derived detritus in the region. The Sulaiman Fold–Thrust Belt (SFB) in southwestern Pakistan preserves a crucial record of this transition, with the Paleocene to Eocene stratigraphic succession providing insights into sediment provenance shifts. To constrain the collision timing, we analyzed detrital zircon for U-Pb-Hf geochronology, supplemented by petrography and zircon Th/U geochemistry, from Cenozoic sequences exposed in the Mughalkot section, SFB. Detrital zircon age distributions from the Paleocene Dunghan Formation are dominated by ∼500–1100 Ma, ∼1400–2000 Ma, and ∼ 2400–2600 Ma grains, indicating a primary sediment source from the Indian Plate. A similar detrital zircon age pattern in the early to middle Eocene Ghazij Formation suggests continued derivation from the Indian craton. However, a pronounced provenance shift is observed in the lowermost Baska Formation (middle Eocene), marked by the arrival of Late Cretaceous–Paleocene (<100 Ma) detrital zircons, which possess Th/U ratios (>0.3) indicative of an igneous origin. Juvenile Hf signatures of the younger detrital zircons further support their derivation from the Kohistan-Ladakh Arc, which is located between the Indian and the Asian plates in North Pakistan. The arrival of this detritus signals the onset of the India-Asia collision, constrained by the maximum depositional age to post–51 Ma. When compared to northern and central segments of the Himalayan orogen, this suggests a diachronous collision with its later onset in the westernmost region. These findings contribute to the broader framework of India-Asia convergence, supporting models that invoke regional variability in collision timing and foreland basin evolution.
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