West-East Variability in Lower Siwalik Detrital-Zircon Provenance: Implications for Sediment Connectivity in the Himalayan Foreland Basin

This study presents the first detrital-zircon U–Pb age dataset from the Lower Siwalik equivalent (Uzdha Pasha Formation) in the western Sulaiman Fold Belt and compares it with published records from other parts of the Himalayan foreland basin. Three sandstone samples yield 197 concordant ages. The spectra are multimodal and dominated by Neoproterozoic to early Paleozoic ages (~1000–400 Ma), with subordinate older populations and a minor Mesozoic–Cenozoic component (<145 Ma). Probability–density comparisons in DZstats show the strongest correspondence between the Uzdha Pasha Formation and the Murree Formation (cross-correlation = 0.60, similarity = 0.91, likeness = 0.71). Bootstrap resampling yields 95% intervals of 0.710–0.812 for cross-correlation, 0.868–0.920 for similarity, and 0.647–0.726 for likeness. Bootstrap analyses show that the preference for the Murree Formation strengthens with increasing sample size. However, KS and Kuiper tests distinguish the Uzdha Pasha spectrum from all comparison datasets, indicating differences in age-population proportions and distribution shape. Multidimensional scaling further documents variable relationships among the studied and reference datasets. Although the age distributions are compatible with contributions from several Himalayan source regions, overlapping age signatures, variable zircon fertility, sediment recycling, and hydraulic sorting prevent unique estimation of source proportions from U–Pb ages alone. Consistent with this limitation, a four-source mixture model provides a poor fit (R2 = 0.26). The minor young zircon population is compatible with sediment connectivity to distal Eurasian or Trans-Himalayan arc-bearing sources, but direct axial transport, recycling of older foreland deposits, reworking of intermediate sedimentary units, and transient drainage capture remain viable alternatives. The dataset therefore provides a new western constraint on along-strike variability in Lower Siwalik provenance and is consistent with previously proposed spatially heterogeneous models of Himalayan foreland-basin development.