@article{GhaniZeilingerSobeletal.2018, author = {Ghani, Humaad and Zeilinger, Gerold and Sobel, Edward and Heidarzadeh, Ghasem}, title = {Structural variation within the Himalayan fold and thrust belt}, series = {Journal of structural geology}, volume = {116}, journal = {Journal of structural geology}, publisher = {Elsevier Science Publishers Ltd.}, address = {Oxford}, issn = {0191-8141}, doi = {10.1016/j.jsg.2018.07.022}, pages = {34 -- 46}, year = {2018}, abstract = {The Kohat and Potwar fold thrust belts (KP-FTB) in Pakistan exhibit structural variations over 250 km along strike within the Himalayan fold and thrust system. Our 3D deformation model shows that Kohat surface structures evolved above an active roof thrust in Eocene evaporites. The ramp-forming duplexes in the Kohat were stacked and passively transported toward the foreland above new ramps, resulting in up to 5 km of thickening between the two decollements. Ramps from the Kohat extend into the Potwar as thrust tips of fault propagation folds. The basement slope changes from flat (beta < 1 degrees) below the northern part to north-dipping (beta > 1 degrees) below the southern part, corresponding to the change in structural style and complexity of the KP-FTB. The Kalabagh Fault Zone, linking the two belts, is interpreted as a zone of complex dextral strike-slip rotational faulting. Salt expulsed from the hanging walls of normal faults and under synclines in the Kalabagh Fault Zone moved toward the footwall of normal faults, accumulated in the cores of anticlines, and formed lobe structures at the deformation front. The fundamental reasons for the variable structural styles are changes in decollement strength, basement slope, preexisting normal faulting, presence of a secondary decollement and spatially-variable salt mobility and accumulation.}, language = {en} } @misc{GhaniSobelZeilingeretal.2021, author = {Ghani, Humaad and Sobel, Edward and Zeilinger, Gerold and Glodny, Johannes and Zapata, Sebastian and Irum, Irum}, title = {Palaeozoic and Pliocene tectonic evolution of the Salt Range constrained by low-temperature thermochronology}, series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {3}, issn = {1866-8372}, doi = {10.25932/publishup-56256}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-562567}, pages = {15}, year = {2021}, abstract = {The Salt Range in Pakistan exposes Precambrian to Pleistocene strata outcropping along the Salt Range Thrust (SRT). To better understand the in-situ Cambrian and Pliocene tectonic evolution of the Pakistan Subhimalaya, we have conducted low-temperature thermochronological analysis using apatite (U-Th-Sm)/He and fission track dating. We combine cooling ages from different samples located along the thrust front of the SRT into a thermal model that shows two major cooling events associated with rifting and regional erosion in the Late Palaeozoic and SRT activity since the Pliocene. Our results suggest that the SRT maintained a long-term average shortening rate of similar to 5-6 mm/yr and a high exhumation rate above the SRT ramp since similar to 4 Ma.}, language = {en} } @article{GhaniSobelZeilingeretal.2020, author = {Ghani, Humaad and Sobel, Edward and Zeilinger, Gerold and Glodny, Johannes and Zapata, Sebastian and Irum, Irum}, title = {Palaeozoic and Pliocene tectonic evolution of the Salt Range constrained by low-temperature thermochronology}, series = {Terra nova}, volume = {33}, journal = {Terra nova}, number = {3}, publisher = {Wiley}, address = {Hoboken}, issn = {0954-4879}, doi = {10.1111/ter.12515}, pages = {293 -- 305}, year = {2020}, abstract = {The Salt Range in Pakistan exposes Precambrian to Pleistocene strata outcropping along the Salt Range Thrust (SRT). To better understand the in-situ Cambrian and Pliocene tectonic evolution of the Pakistan Subhimalaya, we have conducted low-temperature thermochronological analysis using apatite (U-Th-Sm)/He and fission track dating. We combine cooling ages from different samples located along the thrust front of the SRT into a thermal model that shows two major cooling events associated with rifting and regional erosion in the Late Palaeozoic and SRT activity since the Pliocene. Our results suggest that the SRT maintained a long-term average shortening rate of similar to 5-6 mm/yr and a high exhumation rate above the SRT ramp since similar to 4 Ma.}, language = {en} } @article{GhaniSobelZeilingeretal.2021, author = {Ghani, Humaad and Sobel, Edward and Zeilinger, Gerold and Glodny, Johannes and Irum, Irum and Sajid, Muhammad}, title = {Spatio-temporal structural evolution of the Kohat fold and thrust belt of Pakistan}, series = {Journal of structural geology}, volume = {145}, journal = {Journal of structural geology}, publisher = {Elsevier}, address = {Amsterdam [u.a.]}, issn = {0191-8141}, doi = {10.1016/j.jsg.2021.104310}, pages = {16}, year = {2021}, abstract = {The Kohat fold and thrust belt in Pakistan shows a significantly different structural style due to the structural evolution on the double d{\´e}collement compared to the rest of the Subhimalaya. In order to better understand the spatio-temporal structural evolution of the Kohat fold and thrust belt, we combine balanced cross sections with apatite (U?Th-Sm)/He (AHe) and apatite fission track (AFT) dating. The AHe and AFT ages appear to be totally reset, allowing us to date exhumation above structural ramps. The results suggest that deformation began on the frontal Surghar thrust at-15 Ma, predating or coeval with the development of the Main Boundary thrust at-12 Ma. Deformation propagated southward from the Main Boundary thrust on double de?collements between 10 Ma and 2 Ma, resulting in a disharmonic structural style inside the Kohat fold and thrust belt. Thermal modeling of the thermochronologic data suggest that samples inside Kohat fold and thrust belt experienced cooling due to formation of the duplexes; this deformation facilitated tectonic thickening of the wedge and erosion of the Miocene to Pliocene foreland strata. The spatial distribution of AHe and AFT ages in combination with the structural forward model suggest that, in the Kohat fold and thrust belt, the wedge deformed in-sequence as a supercritical wedge (-15-12 Ma), then readjusted by out-sequence deformation (-12-0 Ma) within the Kohat fold and thrust belt into a sub-critical wedge.}, language = {en} } @phdthesis{Ghani2019, author = {Ghani, Humaad}, title = {Structural evolution of the Kohat and Potwar fold and thrust belts of Pakistan}, doi = {10.25932/publishup-44077}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-440775}, school = {Universit{\"a}t Potsdam}, pages = {viii, 121}, year = {2019}, abstract = {Fold and thrust belts are characteristic features of collisional orogen that grow laterally through time by deforming the upper crust in response to stresses caused by convergence. The deformation propagation in the upper crust is accommodated by shortening along major folds and thrusts. The formation of these structures is influenced by the mechanical strength of d{\´e}collements, basement architecture, presence of preexisting structures and taper of the wedge. These factors control not only the sequence of deformation but also cause differences in the structural style. The Himalayan fold and thrust belt exhibits significant differences in the structural style from east to west. The external zone of the Himalayan fold and thrust belt, also called the Subhimalaya, has been extensively studied to understand the temporal development and differences in the structural style in Bhutan, Nepal and India; however, the Subhimalaya in Pakistan remains poorly studied. The Kohat and Potwar fold and thrust belts (herein called Kohat and Potwar) represent the Subhimalaya in Pakistan. The Main Boundary Thrust (MBT) marks the northern boundary of both Kohat and Potwar, showing that these belts are genetically linked to foreland-vergent deformation within the Himalayan orogen, despite the pronounced contrast in structural style. This contrast becomes more pronounced toward south, where the active strike-slip Kalabagh Fault Zone links with the Kohat and Potwar range fronts, known as the Surghar Range and the Salt Range, respectively. The Surghar and Salt Ranges developed above the Surghar Thrust (SGT) and Main Frontal Thrust (MFT). In order to understand the structural style and spatiotemporal development of the major structures in Kohat and Potwar, I have used structural modeling and low temperature thermochronolgy methods in this study. The structural modeling is based on construction of balanced cross-sections by integrating surface geology, seismic reflection profiles and well data. In order to constrain the timing and magnitude of exhumation, I used apatite (U-Th-Sm)/He (AHe) and apatite fission track (AFT) dating. The results obtained from both methods are combined to document the Paleozoic to Recent history of Kohat and Potwar. The results of this research suggest two major events in the deformation history. The first major deformation event is related to Late Paleozoic rifting associated with the development of the Neo-Tethys Ocean. The second major deformation event is related to the Late Miocene to Pliocene development of the Himalayan fold and thrust belt in the Kohat and Potwar. The Late Paleozoic rifting is deciphered by inverse thermal modelling of detrital AFT and AHe ages from the Salt Range. The process of rifting in this area created normal faulting that resulted in the exhumation/erosion of Early to Middle Paleozoic strata, forming a major unconformity between Cambrian and Permian strata that is exposed today in the Salt Range. The normal faults formed in Late Paleozoic time played an important role in localizing the Miocene-Pliocene deformation in this area. The combination of structural reconstructions and thermochronologic data suggest that deformation initiated at 15±2 Ma on the SGT ramp in the southern part of Kohat. The early movement on the SGT accreted the foreland into the Kohat deforming wedge, forming the range front. The development of the MBT at 12±2 Ma formed the northern boundary of Kohat and Potwar. Deformation propagated south of the MBT in the Kohat on double d{\´e}collements and in the Potwar on a single basal d{\´e}collement. The double d{\´e}collement in the Kohat adopted an active roof-thrust deformation style that resulted in the disharmonic structural style in the upper and lower parts of the stratigraphic section. Incremental shortening resulted in the development of duplexes in the subsurface between two d{\´e}collements and imbrication above the roof thrust. Tectonic thickening caused by duplexes resulted in cooling and exhumation above the roof thrust by removal of a thick sequence of molasse strata. The structural modelling shows that the ramps on which duplexes formed in Kohat continue as tip lines of fault propagation folds in the Potwar. The absence of a double d{\´e}collement in the Potwar resulted in the preservation of a thick sequence of molasse strata there. The temporal data suggest that deformation propagated in-sequence from ~ 8 to 3 Ma in the northern part of Kohat and Potwar; however, internal deformation in the Kohat was more intense, probably required for maintaining a critical taper after a significant load was removed above the upper d{\´e}collement. In the southern part of Potwar, a steeper basement slope (β≥3°) and the presence of salt at the base of the stratigraphic section allowed for the complete preservation of the stratigraphic wedge, showcased by very little internal deformation. Activation of the MFT at ~4 Ma allowed the Salt Range to become the range front of the Potwar. The removal of a large amount of molasse strata above the MFT ramp enhanced the role of salt in shaping the structural style of the Salt Range and Kalabagh Fault Zone. Salt accumulation and migration resulted in the formation of normal faults in both areas. Salt migration in the Kalabagh fault zone has triggered out-of-sequence movement on ramps in the Kohat. The amount of shortening calculated between the MBT and the SGT in Kohat is 75±5 km and between the MBT and the MFT in Potwar is 65±5 km. A comparable amount of shortening is accommodated in the Kohat and Potwar despite their different widths: 70 km Kohat and 150 km Potwar. In summary, this research suggests that deformation switched between different structures during the last ~15 Ma through different modes of fault propagation, resulting in different structural styles and the out-of-sequence development of Kohat and Potwar.}, language = {en} }