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Plateau (Fig. 2). Here, the surface expression is that of a buried mountain front. A typical traverse may start from the axis of the Soan syncline across the Khairi-Murat Range. Along this traverse, autochthonous flat strata along the axis of the Soan syncline are tilted increasingly northward above a south-dipping passive backthrust (JaswalABSTRACT Surface geology and seismic reflection profiles reveal the geometry of a triangle zone in the Himalayan foreland of Pakistan. Surface expression of the triangle zone is the Soan syncline (monocline), the northern foreland-dipping steep limb of which is located above a bedding-parallel backthrust in the Tertiary molasse strata. The hinterland-dipping Khairi-Murat thrust is located on the proximal end of the triangle zone. The steep Dhurnal backthrust becomes shallower to the south and dies out at a depth of about 2 to 4 km. At this depth, it merges with a north-dipping blind thrust that propagates upsection as a ramp from a layer of Eocambrian evaporites at a depth of about 8 km and forms a flat along a pelitic horizon in Miocene molasse strata. The two faults bound a blind, tapered wedge of allochthonous strata (core wedge) inserted below the backthrust. Coherent and discoherent reflections above and below the Dhurnal backthrust show the undeformed planar and deformed (pop-ups) geometry of the footwall and hanging wall outside and inside the wedge.We interpret the three-dimensional geometry of the triangle zone in terms of a core wedge having flat-ramp-flat geometry and internal as well as external pop-ups. The presence of blind faults of smaller lateral extent (about 10 km) and shortening (about 2 km) indicates the occurrence of more than one hydrocarbon trap in the triangle zone.Published magnetostratigraphy limits the formation of the triangle zone between 2.1 to 1.9 Ma. On the basis of cross-section balancing, we calculate horizontal contraction of 4.5 km and rock uplift of about 2.8 km along the core wedge. The shortening and rock uplift rates amount to about 22 mm/yr and about 14 ± 2 mm/yr, respectively. The presence of hydrocarbons (the Dhurnal oil field) in such young structural traps in the Salt Range has important bearings for the exploration of oil and gas in the Himalayan foreland.

We carried U‐Pb‐Hf geochronology of the clastic sequence covering upper Mesozoic‐Cenozoic period. The upper Mesozoic sequence is overlain unconformably by the Cenozoic strata, marking regional K‐T boundary, which is mapped as angular unconformity. This angular relationship may strongly indicate a compressional orogenic event that occurred during the Late Cretaceous. Late Cretaceous Kohistan‐Karakoram collision and ophiolite emplacement may account for the development of this compression along the northern Indian margin. The U‐Pb‐Hf isotopic analyses of the upper Mesozoic and lower Cenozoic sequence (Hangu Formation and Lower Patala Formation) are similar to the Tethyan and Lesser Himalayan signatures, which indicate the Indian‐plate provenance. The two younger Cretaceous grains recorded in the Hangu Formation might be derived from the Indian‐plate volcanic rocks and/or Tethyan Himalayan volcanic rocks. The absence of ophiolitic age component in the precollision sequence may indicate that these ophiolites are not exposed until final India‐Eurasia collision. The major shift in provenance is recorded in the upper part of the Patala Formation, where the presence of disconformity and the appearance of <100 Ma detrital zircons indicate the contribution of Eurasian source (i.e., Kohistan‐Ladakh arc; KLA), which is further supported by the ɛHf(t) signatures. Upsection, the contribution from Eurasian source increased in the Early Middle Eocene Kuldana Formation. Therefore, we suggest that the provenance mixing close to Paleocene‐Eocene boundary indicates that the India‐Eurasia collision in the north Pakistan occurred at ∼56–55 Ma and subsequent exhumation increased the contribution of the northern (Eurasian) provenance in the upsection.