Lower Paleogene Tectonostratigraphy of Balochistan: Evidence for Time-Transgressive Late Paleocene-Early Eocene Uplift

Abstract

Analysis of lithofacies, paleoflow directions, and sandstone petrography of upper Paleocene-lower Eocene paralic and continental sediments exposed along the transpressional suture zone of the western margin of the Indian plate indicate that the process of deformation and uplift of the carbonate shelf in this area had started by late Paleocene time. This tectonic uplift and deformation is documented by: (1) an overall shallowing upward synorogenic sequence of sediments, (2) proximal conglomerate facies (consisting of lower Paleocene and Mesozoic clasts) dominating in the western part of the study area and distal facies of sandstone and shale dominating in the eastern part of the study area, (3) the existence of an unconformity of late Paleocene-early Eocene age in the Quetta and Kalat regions, (4) paleocurrent directions in deltaic and fluvial deposits indicating southeastward flowing sediment dispersal paths during late Paleocene-early Eocene time, which is opposite to that found in the late Cretaceous, suggesting a reversal in the depositional slope of the Cretaceous shelf, and (5) petrographic study of sandstones indicating a collision suture/fold thrust belt provenance. This episode of uplift and deformation could be the result of India-Arabian transpression with associated ophiolite obduction or, more likely, to represent the local response to initial India-Asia contact. The unroofing pattern and uplift geometry of the western Indian shelf suggests that this tectonism first started in the southern part of the study area (Kalat-Khuzdar area) during the late Paleocene-early Eocene and proceeded northward in a time-transgressive fashion

Tectonic Implications of Detrital Zircon Ages From Lesser Himalayan Mesozoic‐Cenozoic Strata, Pakistan

“…Few samples are also collected from the roadside along the mapped traverse other than Chhangla Gali section (Figures a and ). The Cretaceous‐Miocene sequence in Pakistan was generally studied by traditional petrographic method for deciphering the provenance interpretation and depositional settings (Bossart & Ottiger, ; Critelli & Garzanti, ; Khan & Clyde, ). In this study, we first time carried detrital zircon U‐Pb‐Hf isotopic analyses for Mesozoic sequence in addition to the Paleogene sequence.…”

Structural setting and evolution of the Afghan orogenic segment – a review

“…The collision began at about 55 Ma in the SE corner of Afghanistan (Khan & Clyde 2013) and the northward movement of the Indian subcontinent continues until today, as indicated by the high seismic activity of the whole region.…”

“…The Khost-Waziristan ophiolites can be grouped together, with the Muslim Bagh and Bela ophiolites forming the axial Balochistan ophiolite belt of eastern Afghanistan and Pakistan (Gnos et al 1997;Robinson et al 2000;Khan & Clyde 2013) (Fig. 2).…”

“…In the case of the northern Khost ophiolite, it is likely that the sediments were supplied by the Kabul Block (Montenat 2009). Khan & Clyde (2013) suggested that the initial India-Asia collision started south of Quetta at about the Paleocene-Eocene boundary (c. 55 Ma), and proceeded northwards along a transpressional margin in late Early Eocene time (c. 52 Ma) to the northern collision sutures of the Main Mantle thrust and the Indus-Yarlung suture in the western Himalaya (Fig. 2).…”

“…The emergence of the axial belt in the course of the initial oblique collision of the Cimmerian Afghan promontory and the Indian Plate in Paleocene times divided the collisional zone into two sedimentary basins: the Katawaz (or Balochistan) Basin to the west and the Indus Basin to the east (Khan & Clyde 2013) (Fig. 2).…”