Potwar Plateau Research Articles

Sandstone Petrology and Provenance of the Siwalik Group (Northwestern Pakistan and Western-Southeastern Nepal)

ABSTRACT The Siwalik Group consists of a Neogene sedimentary succession 5-8 km thick, deposited as the Himalayan foreland basin developed following collision between the Indian and Eurasian continents. It consists of fluvial deposits composed of shale, siltstone, and sandstone in the lower part and thick sandstone and conglomerate in the upper part. This paper presents new petrologic data on the sandstone composition of two coeval petrofacies of Siwalik Group in two areas: the Potwar Plateau of northwestern Pakistan, and the Surai Khola and Bakiya Khola localities of western and southeastern Nepal. In both regions, detrital modes reflect a collisional-orogen provenance. Petrologic parameters indicate derivation from mid-crustal rocks and overlying sedimentary strata ascribed to different tectonostratigraphic units of the High Himalaya and Tibetan zone. The Siwalik sandstones of the Potwar Plateau (NW Pakistan) are composed of low- to medium-grade metamorphic and sedimentary detritus, and subordinately, of ophiolitic and volcanic detritus. Abundant metamorphic detritus consists of phyllite, fine-grained schist lithics, and coarse-grained gneiss derived from the High and/or Lesser Himalaya. Sedimentary detritus is represented by abundant limestone, radiolarian chert, siltstone, shale, very fine-grained quartzarenite, and other sandstone grains. The siliciclastic grains probably were eroded from older terrigenous sequences, belonging to the Tethys Himalayan and Lesser Himalayan zones, uplifted during the India-Eurasia collision. Ophiolitic, volcanic lithic grains and radiolarian chert reflect a provenance from the Indus suture and Tran -Himalayan belt. The sandstones of western and southeastern Nepal (Surai Khola and Bakiya Khola sections) have higher quartz and lower feldspar contents than those of northwestern Pakistan and contain sedimentaclastic (western Nepal) and metamorphiclastic sandstones (southeastern Nepal). Comparison of the data presented here with previous work on pre- and post-Siwalik sandstones of the Himalaya Range and of the remnant-ocean basins along both sides of the Indian Peninsula (also derived from the Himalayan suture belt) suggests abundant quartzolithic detritus from the Eocene to the present. Varying proportions of lithic populations in time are related to rapid uplift of the Himalayas and intense unroofing of sedimentary, metasedimentary and deeper terranes.

Changing mechanical response during continental collision: Active examples from the foreland thrust belts of Pakistan

We have used data from teleseismic, seismic reflection and field geologic studies, along with both geomechanical and gravity modeling to contrast the tectonics of four active orogenic wedges in Pakistan: the Kashmir Himalaya, the Salt Range-Potwar Plateau foldbelt, the Sulaiman Range and the Makran accretionary wedge.In Makran, oceanic crust is still being subducted, and a thick pile of sediments is being accreted and underplated. Undercompaction and excess pore pressures can explain the narrow cross-sectional taper and frontal aseismicity of this wedge. Beneath the Sulaiman wedge, continental crust is just starting to be underthrust. Indirect evidence suggests that fine-grained carbonate rocks found in abundance deep in the stratigraphic section may be deforming ductilely at the base of the Sulaiman wedge and provide a zone of ductile detachment. The collision has proceeded to a much more mature stage in the Salt Range-Potwar Plateau foldbelt and the Kashmir Himalaya. Isostatic response to underthrusting of continental crust has kept the sedimentary pile quite thin in both of these wedges, so in that respect the two foldbelts are similar. However, thick Eocambrian salt beneath the Salt Range and Potwar Plateau permits that foldbelt to be much wider in map view, with a thinner cross-sectional taper and a mixture of thrust vergence directions. A major normal fault in basement causes the Salt Range to rise in front of the mildly deformed molasse basin of the southern Potwar Plateau.Much of the diversity among these mountain belts can be understood in terms of differences in the maturity of the collision process in each area, the resulting thickness of the sedimentary pile encountered at the deformation front, and the presence or absence of large contrasts in strength between the various layers of the stratigraphic section and basement relief.

Ancient river systems in the Himalayan foredeep, Chinji Village area, northern Pakistan

The Miocene Chinji and Nagri Formations (Siwalik Group) of northern Pakistan record ancient fluvial environments in the Himalayan foredeep basin. Excellent exposures on the Potwar Plateau (Chinji Village area) allowed detailed documentation of the geometry and stacking of sediment bodies that comprise these strata, and of variation of large-scale bedding geometry, grainsize, sedimentary structures and paleocurrent orientations within such bodies. Major sandstone bodies are tens of meters thick and are continuous along strike for many kilometers. They are composed internally of interconnected channel belt deposits, each of which contain several storeys (channel bar and fill deposits). Individual storeys, defined by inclined bedsets dipping down to a major basal erosion surface at up to 11°, are only 5 to 15 m thick within the Chinji Formation but can be up to 30 m thick within the Nagri Formation. Bedsets within storeys reflect sediment accreted during individual flood events. Along-strike variation of bedsets within storeys and the stacking patterns of storeys within channel belt deposits reflect changes in the channel bed through time due to the growth of bars, migration of channels, and channel cutoff. Generally, braided channel patterns are indicated by the relatively large number of storeys within individual channel belt deposits exposed perpendicular to paleoflow, abundant evidence for channel bar superposition due to channel switching, local evidence for mid-channel bars, dominance of coarse-grained channel fills, and low paleocurrent variations. Paleochannel reconstructions from storeys exposed within the Chinji Formation indicate that individual channel segments generally had widths of 80–200 m, maximum depths of 4–13 m, wavelengths of 1.6–2 km and discharges of 400–800 m 3/s. Full channel belt widths (1–2 km) estimated from exposures perpendicular to paleoflow, and evidence for 2–3 coeval channels within channel belts, indicate full channel discharges of 1500–2000 m 3/s. Larger channel segments reconstructed from the Nagri Formation had widths of 200–400 m, maximum depths of 15–30 m, wavelengths of 3–5 km, and discharges of 3000–5000 m 3/s. As Nagri Formation channel systems were also clearly braided, full channel dimensions and discharge estimates are probably at least a factor of two greater than for individual channel segments (i.e. order of 10,000 m 3/s). Strata between major sandstone bodies are dominated by lobate and wedge-shaped bodies (crevasse splay and levee deposits), minor channel-form bodies (deposits of minor floodplain channels), laminated mudstone bodies (lake deposits) and paleosols. These strata are arranged into meters to 10 m thick stratified sequences that were rapidly deposited, bounded by well developed paleosols recording periods when deposition rates were low. The thickness and grainsize of such paleosol bounded sequences are not directly related to the proximity of a major channel deposit along strike. Instead, such sequences within overbank deposits appear to reflect local progradation of splays and levees into low areas on the floodplain.

Evolution of miocene fluvial systems in the himalayan foredeep through a two kilometer-thick succession in northern Pakistan

Sedimentological variations through a kilometer-thick coarsening-upward succession in the Miocene Himalayan foredeep basin (fluvial Chinji and Nagri Formations of the Siwalik Group) are documented in the Chinji Village area on the Potwar Plateau of northern Pakistan. From the Chinji Formation upwards into the Nagri Formation: (1) the proportion of major sandstone bodies increase relative to mudstone-dominated beds; (2) average thickness and mean grainsize of channel deposits increase; (3) sediment aggradation rates increase; (4) there is a reported change in sediment providence; (5) paleocurrents are generally to the southeast and vary little upsection; and (6) paleosols are more distinct lower in the section where there is also more evidence of ponding of water on the floodplain. Smaller-scale (100 m thick) cyclic variations in the proportion of major channel sandstone bodies also occur in both formations. In the modern Himalayan Basin, sediment dispersal away from the mountain belt is associated with: (1) major rivers that flow along the basin axis; (2) large rivers that drain substantial areas of the mountain belt and deposit low relief sediment fans extending hundreds of kilometers into the basin; and (3) smaller rivers in fan and interfan areas that drain local areas and carry finer sediment loads. Sediment variations through the Chinji-Nagri Formation boundary can be related to a shifting of depositional environments within such fan and interfan areas. Major basin-axial rivers are not exposed in this area. It appears that kilometer-thick upsection variations in these deposits record the progradation of the sediment fan formed by a large river system (river discharge on the order of 10 4 m 3/s) over the floodplain of a smaller river system (river discharge on the order of 10 3 m 3/s). Large-scale vertical sediment variations over hundreds of meters to kilometers appear to reflect changes in the basin subsidence and the rate of sediment input to the basin over time scales on the order of 10 5–10 6 years. Upsection variations can not easily be related to climatic change or eustatic variations in sea level. The most likely explanation for upsection changes is tectonism. Deposition rates and shifting positions of river systems within the basin responded more quickly to changes in basin subsidence rate, whereas increases in the proportion of sandstone bodies and increases in floodplain slopes lagged behind. Deposit variations in the Siwalik Group clearly record variations between different-scale river systems delivering sediment to the basin as well as the overall basin evolution.

Lithostratigraphy and vertebrate biostratigraphy of the early Miocene Himalayan Foreland, Zinda Pir Dome, Pakistan

Deposits in the Sulaiman foothills and Zinda Pir Dome in west-central Pakistan provide new insight into the critical early Miocene record of Himalayan Foreland sedimentation and paleobiology. The Chitarwata Formation, which underlies the Vihowa Formation in the Sulaiman foothills predates the Siwalik deposits on the Potwar Plateau of north-central Pakistan and provides a record of mammals spanning the interval between the early Miocene Bugti fauna and middle Miocene to Pleistocene Siwalik faunas. Siwalik deposits on the Potwar Plateau are no older than middle Miocene; they represent fluvial environments. In contrast, the Chitarwata and Lower Vihowa Formations in the Zinda Pir Dome represent coastal-delta plain and fluvial environments, respectively. Biostratigraphic information from the Chitarwata Formation, coupled with paleomagnetic data (reported by Friedman et al., 1992) from coincident strata, suggest that coastal environments persisted in the area of the Sulaiman foothills until about 18.6 Ma when they were replaced by fluvial environments, probably representing the ancestral Indus River system. Apparently, during the early Miocene when sediments of the Chitarwata Formation were accumulating on the western portion of the Himalayan Foreland Basin much of the area of the Potwar Plateau to the north was being eroded. The overlying Vihowa Formation, along with the relatively contemporaneous Kamlial Formation on the Potwar Plateau, represent the appearance of widespread terrestrial sedimentation in the Himalayan Foreland Basin.

The magnetostratigraphy of the Chitarwata and lower Vihowa formations of the Dera Ghazi Khan area, Pakistan

Three sections of the Chitarwata and lower Vihowa formations were sampled along the Dalana River on the southeastern flank of the Zinda Pir Dome in the southern Sulaiman Range near Dera Ghazi Khan, Pakistan. Together they provide nearly 800 m of a continuous sedimentary record of the Miocene derived from the uplifted Himalayan highlands. Previous studies have examined the Middle and Upper Miocene sediments, the Siwalik Group, of the Potwar Plateau to the north. However, detailed investigations of earlier periods are impossible in that area due to the absence of Oligocene and Lower Miocene sediments caused by continued overthrusting associated with the Himalayan orogeny. Fortunately, the Sulaiman basin to the south, which was further removed from the tectonic activity, provides a record of the Early Miocene in the form of the Chitarwata Formation. The Dalana A, B, and C sections (DGA, DGB, and DGC) were examined and sampled for this study. A magnetostratigraphic analysis was carried out to correlate and date the Chitarwata and Vihowa formations exposed in this area. The samples were subjected to step-wise demagnetization to resolve the primary and secondary remanent magnetization components. Thermal demagnetization trajectories indicate that the majority of samples have sufficient internal consistency that their calculated polarities are reliable. Likewise, the majority of the 126 measured sites showed statistically significant agreement between the three measured samples per site. However, the bimodal data set does not pass the reversal test and so is deemed unsuitable for tectonic interpretations. The individual sections were initially correlated using lithologic and stratigraphic methods, and the relationship was reinforced by the magnetostratigraphy. The composite DG section was tentatively correlated with the standard magnetic polarity time scale placing the disconformable base of the Chitarwata in the DGA section at just older than 22 Ma, the Chitarwata/Vihowa contact at 18.6 Ma, and the top of the Vihowa in the DGC section at about 16 Ma. The assignment of these dates to the Chitarwata will aid in future biostratigraphic and lithostratigraphic correlation of Early Miocene sediments, effectively extending the well-established Siwalik faunal sequence back by four million years.

Abnormally High Formation Pressures, Potwar Plateau, Pakistan

Abnormally High Formation Pressures, Potwar Plateau, Pakistan

Loess of Central Asia

Loess deposits are widespread within the piedmont and intramontane depressions of Central Asia. They cover piedmont plains, river terraces, ridge slopes and watersheds. Loess is a significant component in the piedmonts of Tien Shan, eastern Fergana depression, the Afgan-Tajik depression, piedmonts of Kopetdag, Badchyz and Karabil Hills north of Parapamiz, in the Kashmir valley, on the Potwar Plateau and in the Peshawar Basin.

Contemporary tectonics of the Himalayan frontal fault system: folds, blind thrusts and the 1905 Kangra earthquake

The Sub-Himalayan fold-thrust belt consists of deformed late Cenozoic and older deposits south of the Main Boundary thrust (MBT). In Pakistan, east of the Indus River, the Sub-Himalaya comprises the Potwar Plateau and the Salt Range, which is thrust southward over the Jhelum River floodplain along the Salt Range thrust. Although an estimated 9–14 mm a −1 shortening has been taken up on the Salt Range thrust during the last 2 Ma, the range-front scarp does not show signs of recent faulting. Shortening may be shifting southward to the Lilla overpressured anticline, which rises from the Jhelum floodplain as a fault-propagation fold. Farther east, shortening is partitioned among several anticlines underlain by foreland- and hinterland-dipping blind thrusts. Southeast of the main deformation zone, the Pabbi Hills overpressured anticline is best explained as a fault-propagation fold. Throughout the Potwar Plateau and Salt Range, thrusts and folds rise from a basal décollement horizon in Eocambrian evaporites. The Pakistani part of the décollement horizon could generate large earthquakes only if these evaporites die out northward at seismogenic depths. In India and Nepal, the Sub-Himalaya is narrower, reflecting the absence of evaporites and a steeper slope of the basement towards the hinterland. The southern boundary of the Sub-Himalaya is the Himalayan Front fault, discontinuous because part of the shortening is expressed at the surface by folding. Broad, alluvial synclinal valleys (dun valleys) are bounded on the south by rising barrier anticlines of Siwalik molasse. The 1905 Kangra earthquake (M8) produced uplift on the Mohand anticline and the Dehra Dun Valley, suggesting that this earthquake occurred on a décollement horizon above basement, downdip from the fold. If so, the Kangra event is the largest known earthquake on a blind thrust expressed at the surface as a fold.

Thrust kinematics in the Kohat Plateau, Trans Indus Range, Pakistan

The Kohat Plateau consists of a heavily deformed and structurally elevated thrust sheet. Pop-ups, broad synclines and narrow fault- and evaporite-cored anticlines record high-level translation of a large thrust mass along Eocene evaporites. A lower detachment level is also inferred, located at the base of the Mesozoic-Palaeozoic section. This lower detachment is common to both the Kohat and the adjacent Potwar Plateaux whereas the upper level is restricted to the Kohat. Beneath the Kohat, a blind imbricate stack of pre-Tertiary rocks is developed. Above their roof thrust, the foreland basin-fill of Kohat records greater internal deformation compared to that of the adjacent Potwar Plateau. In contrast, the Potwar thrust belt displays a greater amount of overthrusting on its basal surface, this displacement emerging in the Salt Range. Total shortening across the two plateaux is comparable, but is accommodated in an areally smaller thrust belt with a higher structural relief in the Kohat as compared to the Potwar structural province. The resultant geographical offset of the thrust front is denoted by the Hukni-Kalabagh lateral ramp. The differences in the thrust kinematics are tentatively suggested to be caused by the mechanical response of the orogenic wedge to different imposed geometries of the wedge laterally within the basin. The Kohat Plateau appears to have a lower basal dip than does the western Potwar, and thus shows greater internal deformation.

Stratigraphy and Depositional Environments of the Paleogene of the Potwar Plateau, Northern Pakistan

Stratigraphy and Depositional Environments of the Paleogene of the Potwar Plateau, Northern Pakistan

Paleomagnetic Isochrons, Unsteadiness, and Non-Uniformity of Sedimentation in Miocene Fluvial Strata of the Siwalik Group, Northern Pakistan

In complement with stratigraphic and sedimentologic studies, the time resolution provided by magnetic polarity stratigraphy is a powerful tool that can be used to identify, assess, and quantify both temporal variability (unsteadiness) in sediment accumulation over a particular stratigraphic sequence and spatial variability (non-uniformity) in sedimentation across a depositional system. Chronostratigraphic variability is documented and evaluated in the Miocene channel and floodplain sediments of the Chinji Formation, part of the extensive Siwalik foreland sequence located on the Potwar Plateau of northern Pakistan. Magnetic polarity stratigraphies have been developed in multiple vertical sections correlated along strike, allowing for paleomagnetic isochrons to be traced throughout the sequence and providing a chronologic framework in which to identify unsteadiness and non-uniformity in patterns of sediment accumulation. Analysis of variability over different time scales is accomplished by constructing simu...

The Siwaliks of Pakistan: Time and Faunas in a Miocene Terrestrial Setting

Magnetostratigraphy provides unparalleled chronologic precision for long terrestrial sedimentary records. The Siwaliks of the Potwar Plateau, northern Pakistan, present perhaps the best example of a sequence of well dated faunal horizons spanning most of the Neogene in a single terrestrial biogeographic province. Temporal control on fossil localities tied to multiple paleomagnetic sections is ca. 0.1 m.y., less given special conditions of short magnetozone duration or superpositional relationships. New correlations are presented for two long sections in the lower Siwaliks showing the power and the limitations of mag-netostratigraphic correlation within the Siwalik depositional setting. Correlation of Potwar fossil localities to those of an East African section, also dated paleomagnetically, are established with fossil localities from those two biogeographic provinces shown to be coeval on a scale of $$10^{5}$$ yr. The composite biostratigraphy rendered by the thick, well exposed, well dated Potwar Siwalik...

Structural Interpretation of Seismic Reflection Data from Eastern Salt Range and Potwar Plateau, Pakistan

Approximately 1,6000 km of seismic reflection profiles from the eastern Salt Range and Potwar Plateau (SR/PP) of Pakistan is integrated with available magnetostratigraphic, surface geologic, and well data to classify structural styles, determine the timing of deformation, and estimate the amount of telescoping of the sedimentary cover. The eastern SR/PP are similar to other fold-and-thrust belts underlain by evaporites in that (1) it is part of a zone of overthrusting that extends considerably farther over the Himalayan foreland than adjacent areas not underlain by evaporites, (2) the overall thrust wedge has a narrow cross-sectional taper, (3) structures verge toward the hinterland as well as toward the foreland, and (4) fold trends are long and continuous, consisting of tight salt-cored anticlines separated by broad synclines. Disharmonic folding of the sedimentary section relative to the underlying basement is due to effective decoupling along the intervening salt layer. Subsurface mapping atop a strongly reflective sequence of Cambrian to Eocene strata reveals that many surface folds are cored by both foreland- and hinterland-dipping blind thrusts, and some are fault propagation folds. In some cases, intersecting thrusts result in local triangle zones; other surface folds have a pop-up geometry. The dip of the basement toward the inner part of the fold-and-thrust belt is more gentle in the eastern SR/PP (1°-1.5°) than the central SR/PP (2°-3°). Mechanical considerations demonstrate that, unlike the relatively undeformed central SR/PP, a broad deformational zone has developed in the eastern SR/PP to provide a surface topographic slope necessary to maintain a critical taper of the thrust wedge. Cross section balancing indicates that approximately 24 km of shortening has occurred across the foreland in the eastern SR/PP since 5.5 Ma, approximately 18 km in the last 2.5 m.y. The shortening rate of 7 mm/year for the latter time interval is roughly 15% of the 40 to 50-mm/year convergence rate between the Indian and Eurasian plates.

A new large species of Sivapithecus from the Siwaliks of Pakistan

A new species of Sivapithecus, S. parvada, is described on the basis of a large sample of dental-gnathic and postcranial remains from a single locality (Sethi Nagri, ca. 8·8 My old) in the Siwalik sequence of the Potwar Plateau, Pakistan. Its most striking feature is its very large size compared to other Siwalik Sivapithecus species. It also differs in mandibular dental proportions, having very large premolars and M 3 relative to M 1 and M 2. The temporal position of S. parvada is analyzed in the context of other Siwalik hominoid samples and Siwalik mammal faunas generally. A brief review of Siwalik hominoid taxonomy and a new diagnosis of the genus Sivapithecus are also presented. The holotype of Gigantopithecus giganteus, whether an M 2 or an M 3, accords better with the mandible of G. “bilaspurensis” than with any Sivapithecus species, and the synonymy of these two taxa is upheld.

Mechanics of the Salt Range‐Potwar Plateau, Pakistan: A fold‐and‐thrust belt underlain by evaporites

The Salt Range and Potwar Plateau are part of the active foreland fold‐and‐thrust belt of the Himalaya in northern Pakistan. In this region the distance from the Main Boundary Thrust (MBT) to the front of the fold‐and‐thrust belt is very wide (100–150 km) because a thick evaporite sequence forms the zone of décollement. Recent studies have combined seismic reflection profiles, petroleum exploration wells, Bouguer gravity anomalies, and surface geology to construct cross sections in the eastern, central, and western Salt Range‐Potwar Plateau areas. In this study the sections are compared with a model that considers the mechanics of a fold‐and‐thrust belt to be analogous to that of a wedge of snow or soil pushed in front of a bulldozer (Chapple, 1978; Davis et al., 1983; Dahlen et al., 1984; Dahlen, 1984). Models which include the effects of evaporites at the base (Chapple, 1978; Davis and Engelder, 1985) suggest that these thrust belts will have (1) narrow (< 1°) cross‐sectional tapers, (2) larger widths than areas not underlain by evaporites, (3) symmetrical structures, and (4) changes in deformational style at the edge of the evaporite basin. The section across the eastern Potwar Plateau most closely resembles this latter model, having (1) a taper of 0.8° ± 0.1°, (2) a width of 100–150 km, (3) thrust faults that verge both to the north and south, and (4) structures rotated 30° counterclockwise with respect to the Salt Range. From the observed taper and pore fluid pressures of the eastern Potwar Plateau, estimates of the values for the yield strength of the evaporites (τo) and the coefficient of internal friction of the overlying wedge (μ) are calculated as τo = 1.33–1.50 MPa and μ = 0.95–1.04, which are then applied to the other cross sections. In the central and western sections a basement uplift, the Sargodha High, interferes with the front of the fold‐and‐thrust belt. This feature causes the ramping of the Salt Range Thrust and produces a relatively steep basement slope (2°–4°) beneath the Potwar Plateau. This dip, in the presence of the weak evaporite décollement, is sufficient to provide critical taper; no topographic slope is necessary, and the thrust wedge of the southern Potwar Plateau is pushed over the décollement without significant internal deformation. The northern Potwar Plateau is strongly folded and faulted, yet the topographic slope remains flat. Although the deformation suggests that evaporites are not present there, the observed taper in the northern Potwar Plateau is best fitted by the model with evaporites at the décollement. Combining this with published paleomagnetic and geologic constraints, a model for the evolution of the northern Potwar Plateau suggests that the area deformed as a steeply tapered (3.5°–5.5°) thrust wedge until approximately 2 million years ago, when the southward propagating décollement encountered the evaporites. Between 2 Ma and the present, the northern Potwar Plateau has been pushed along the salt décollement without deformation, and erosion has reduced its original steep topographic slope to a nearly level surface.

Development of the Himalayan frontal thrust zone: Salt Range, Pakistan

Research Article| January 01, 1988 Development of the Himalayan frontal thrust zone: Salt Range, Pakistan Dan M. Baker; Dan M. Baker 1Department of Geology, Oregon State University, Corvallis, Oregon 97331 Search for other works by this author on: GSW Google Scholar Robert J. Lillie; Robert J. Lillie 1Department of Geology, Oregon State University, Corvallis, Oregon 97331 Search for other works by this author on: GSW Google Scholar Robert S. Yeats; Robert S. Yeats 1Department of Geology, Oregon State University, Corvallis, Oregon 97331 Search for other works by this author on: GSW Google Scholar Gary D. Johnson; Gary D. Johnson 2Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire 03755 Search for other works by this author on: GSW Google Scholar Mohammad Yousuf; Mohammad Yousuf 3Oil and Gas Development Corporation, 13-N, Markaz F/7, Islamabad, Pakistan Search for other works by this author on: GSW Google Scholar Agha Sher Hamid Zamin Agha Sher Hamid Zamin 3Oil and Gas Development Corporation, 13-N, Markaz F/7, Islamabad, Pakistan Search for other works by this author on: GSW Google Scholar Geology (1988) 16 (1): 3–7. https://doi.org/10.1130/0091-7613(1988)016<0003:DOTHFT>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Dan M. Baker, Robert J. Lillie, Robert S. Yeats, Gary D. Johnson, Mohammad Yousuf, Agha Sher Hamid Zamin; Development of the Himalayan frontal thrust zone: Salt Range, Pakistan. Geology 1988;; 16 (1): 3–7. doi: https://doi.org/10.1130/0091-7613(1988)016<0003:DOTHFT>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The Salt Range is the active frontal thrust zone of the Himalaya in Pakistan. Seismic reflection data show that a 1 km offset of the basement acted as a buttress that caused the central Salt Range-Potwar Plateau thrust sheet to ramp to the surface, exposing Mesozoic and Paleozoic strata. The frontal part of the thrust sheet was folded passively as it overrode the subthrust surface on a ductile layer of Eocambrian salt. Lack of internal deformation of the rear part of the thrust sheet is due to decoupling of sediments from the basement along this salt layer. Early to middle Pliocene (~4.5 Ma) conglomerate deposition in the southern Potwar Plateau, previously interpreted in terms of compressional deformation, may instead document uplift related to basement normal faulting. Stratigraphic evidence, paleomagnetic dating of unconformities, and sediment-accumulation rates suggest that the thrust sheet began to override the basement offset from 2.1 to 1.6 Ma. Cross-section balancing demonstrates at least 20 to 23 km of shortening across the ramp. The rate of Himalayan convergence that can be attributed to underthrusting of Indian basement beneath sediments in the Pakistan foreland is therefore at least 9-14 mm/yr, about 20%-35% of the total plate convergence rate. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Palaeomagnetic constraints on formation of the Mianwali reentrant, Trans-Indus and western Salt Range, Pakistan

Successions of Lower to lower Middle Cambrian, Upper Permian to Upper Triassic and Lower Tertiary carbonates and arenites have been sampled in five sections, representative of the three main segments of the Mianwali reentrant in the (Trans-Indus) Salt Range (northern Pakistan), i.e.: the southern Khisor Range, the northern Surghar Range and the western Salt Range. Comparison of primary and secondary magnetization directions with the Indian APWP demonstrates the secondary origin of the Mianwali reentrant and shows a pattern of rotations which varies in sense and magnitude along the reentrant with the main structural trends. Data from the Trans-Indus and western Salt Range and published Early Cambrian, Early Permian and Late Tertiary palaeomagnetic results from the southern Salt Range and the Potwar Plateau show that the Hazara Arc underwent a 20–45° counterclockwise rotation relative to the Indian Shield. A contrasting clockwise rotation over about 45° has recently been established for thrust sheets in the opposing eastern limb of the Western Himalayan Syntaxis, i.e. for the Panjal Nappe [1] and the Riasi thrust sheet [2]. These palaeomagnetically established rotations conform with the about 75° azimuthal change in structural trend along the Syntaxis, and support Crawford's [3] suggestion that the Salt Range was originally in line with the northwestern Himalaya. The Salt Range front prograded and moved southwards as part of the Hazara Arc thrust sheet, detached from basement along the evaporitic Salt Range Formation. The Mianwali reentrant originated through obstruction of the southwards advancing thrust sheet by moulding around basement topography of the northwest oriented Sarghoda Ridge.

Earliest traces of man in the Potwar Plateau, Pakistan: a report of the British Archaeological Mission to Pakistan

Earliest traces of man in the Potwar Plateau, Pakistan: a report of the British Archaeological Mission to Pakistan

Geology of Petroleum in Kohat-Potwar Depression, Pakistan

The 36,000-km2 Kohat-Potwar depression in northern Pakistan has more than 5,000 m of marine deposition (Precambrian to Eocene, with a major break during Ordovician to Carboniferous). More than 10,000 m of Miocene to Pleistocene alluvial sediments overlies the marine sequence. The tectonic depression formed as a result of continent-to-continent collision at the northwestern margin of the Indian plate. Although the region has been under active petroleum exploration since the mid-nineteenth century, it has been tested by only 60 exploratory wells. Ten oil fields have been discovered; original recoverable reserves total 200 million bbl, of which 112 million bbl has been produced. The region has several attractive features for petroleum generation and accumulation i cluding source-reservoir-trap assemblages and thermal maturity regimes. Total ultimately recoverable hydrocarbon resource of the area is estimated at 2.4 billion bbl of oil equivalent. Many unexplored surface and subsurface prospects and stratigraphic leads are known. Parts of the region, particularly the Bannu depression and Kohat salt zone, can be regarded as frontier areas; based on the exposed geology and available seismic information, we believe these areas are promising. Recent discoveries of Dakhni field (1983) and Dhurnal field (1984), which were the first discoveries in the northern part of the platform zone of the Potwar plateau, and production from Paleozoic horizons have added new dimension to petroleum prospects of the area. The region needs careful reevaluation of available information, exploratory drilling on selected targets, and detailed exploration in its western part.