Sulaiman Fold Belt Research Articles

Sedimentological and sequence stratigraphic analysis of Late Eocene Kirthar Formation, Central Indus Basin, Pakistan, Eastern Tethys

Rakhi Nala (Gorge) section of Eastern Sulaiman Range, Pakistan hosts world-class geological sections from the Cretaceous to the Recent. Here, Late Eocene Kirthar Formation is having a conformable lower contact with the greenish grey massive shale of the Baska Member of the Ghazij Formation. The rusty beds of the Oligocene Chitarwatta Formation are overlying the Kirthar Formation. To understand the detailed microfacies and depositional setting, detailed fieldwork was carried out in the Kirthar Formation in the outer Sulaiman Foldbelt. The late Eocene Kirthar Formation includes Habib Rahi Limestone, Domanda Shale, Pirkoh Limestone, and Drazinda Shale. Domanda Shale Member was deposited in transgression before Habib Rahi Limestone Member was deposited. It was followed up by the deposition of the second member Pirkoh Limestone and Marl Member. Habib Rahi Limestone, Pirkoh Limestone, and Marl Member have catch-up-to-keep-up deposition with rise and fall of sea level. Some facies of Drazinda and Domanda Shales represent a restricted setting supported by the presence of gypsum, while deep sea facies were also identified. This study will provide a guide for evaluating sedimentological concepts and understanding complex facies in highly oil and gas-prone stratigraphic sequences especially in the Eastern Tethys Region.

Seismic data, cross-section balancing, and hydrocarbon prospectivity of the western Sulaiman fold belt, northwest Pakistan

Over the past few decades, hydrocarbon exploration has considerably improved our understanding of foreland deformation. This study used the interpretation of seismic reflection profiles and cross-section balancing techniques to understand the passive-roof duplex geometry of foreland structures in the Western Sulaiman Fold Belt (SFB), Pakistan. Seismic reflection profiles were interpreted to show the presence of hinterland-vergent fault-propagation and fault-bend folds as prospects over a detachment located at a depth of ∼6 km in the pelitic Triassic succession. Cross-section balancing showed intraplate deformation in the hanging-wall flat of the frontal duplex. Clear seismic reflectors above 3 s two-way travel time (TWT), estimates of stratigraphic and tectonic thicknesses with field geology and isopach mapping were used to locate the décollement in the pelitic Permo-Triassic strata at a depth of ∼11 km and interpret stacked duplexes at the mountain front. The foreland deformation of the western SFB was compared with that of the central/eastern SFB. The comparison shows the presence of discovered gas fields, with intraplate deformation of the duplex in the western, and pop-ups in the roof-sequence in eastern SFB depicting the complexity of deformation for the assessment of hydrocarbon prospectivity in the fold belt. The 33 km deformed balanced cross-section was restored to ∼71 km, with 38 km (54%) shortening in the foreland. Approximately 12 km (17%) of shortening was passively accommodated by the hinterland-vergent out-of-sequence passive backthrust in the frontal horse. This description of foreland deformation using the example of the SFB adds to our understanding of the structures of the mountain front that are recognized as zones of prolific hydrocarbon prospects.

Assessment of the probability of success and risking in hydrocarbon exploration: A case study from Zindapir Anticline, Sulaiman Foldbelt, Indus Basin, Pakistan

Role of the statistical calculation is very important in petroleum exploration business. It is used to calculate the associated risk and determines the chances of geological success prior to drilling of an exploratory well in mapped prospect area. This manuscript is focusing on the geological modelling of Zindapir Anticline, Sulaiman Fold Belt, Indus basin, Pakistan using mainly based on the concept of probability developed by Coordinating Committee for Coastal and Offshore Geoscience Program (CCOP) in East and Southeast Asia in 2000. Study area comprises of Zindapir Anticline with two abandoned wells Well X-1 and Zindapir-1 which were drilled and declared as dry holes. Detailed geological modelling indicates that Zindapir structure is still virgin to flow hydrocarbons, and there are ample chances of compartments, which were developed as result of transpressional movement at the periphery of the structure. Interpreted seismic line also supports the presence of different compartments in structure. These compartments may host hydrocarbon, generated and migrated either from Bharti Syncline and Sulaiman Foredeep or generated by indigenous source rocks possibly deposited in the south of Zindapir-1 and Well X-1. Presence of trap, hydrocarbon charge and reservoir in Zindapir structure indicates there is better probability of success for hydrocarbons, and good chances for the development of traps because of transpressional movement. Traps may contain the hydrocarbon, possibly generated from Bharti Syncline in west and Sulaiman Foredeep in east whereas southern part of Zindapir Anticline was not considered, and northern part of Zindapir Anticline was mapped with very open grid size. Present seismic data is limited which is the major reason that due to poor probability of effective trap it is recommended to acquire additional seismic data for further detailed picture structure of Zindapir Anticline. An equation for the calculation of geological chances success for new development well is also proposed in this manuscript.

Rock Physics Modeling and Reservoir Characterization to Estimate Hydrocarbon Zone of Cretaceous and Paleocene Strata and Subsurface Stratigraphic Correlation of Sulaiman Fold Belt to Sulaiman Depression

Rock Physics Modeling and Reservoir Characterization to Estimate Hydrocarbon Zone of Cretaceous and Paleocene Strata and Subsurface Stratigraphic Correlation of Sulaiman Fold Belt to Sulaiman Depression

Geology of Northern Sulaiman Foldbelt, Shirani and Waziristan Regions (South Punjab, Balochistan and Khyber Pakhtunkhwa): New Tomistominae (Miocene False Gharial) from Sakhi Sarwar Area of Dera Ghazi Khan (South Punjab), Pakistan

Northern Koh Sulaiman foldbelt, Shirani, North and South Waziristan (South Punjab, Balochistan and Khyber Pakhtunkhwa) comprised mostly PermoTriassic to Recent sediments with subordinate igneous and metamorphic rocks. These sedimentary strata folded and faulted by geodynamic and tectonic forces occurred during Late Cretaceous to Recent revealed through anticlinal and synclinal foldings and active faultings. The Northern Koh Sulaiman foldbelt, Shirani, North and South Waziristan areas host many economic minerals like copper and chromite, construction stones, marble limestones, gypsum and cement resources, uranium and other radioactive mineral resources, low-quality iron, phosphate and muddy coal, high-quality gemstones, petroleum potential and excellent water resources and many other rocks and minerals. High-quality window and faden quartz crystals deposited in fractures and fissures as vugs and veins deposited by high-temperature hypothermal solution created by the tectonic compression process. The area has economic chromite and magnesite deposits. The Northern Koh Sulaiman foldbelt, Shirani, North and South Waziristan areas have large cement raw materials/resources (limestones, gypsum and shale/clays available mostly on same sites) which vitally need to install many cement industries in these areas because the ideal central location and now only one cement industry (Dera Ghazi Khan cement industry) is in operation. The Northern Koh Sulaiman foldbelt, Shirani, North and South Waziristan consists of excellent surface water resources which need the construction of smaller and medium-sized dams on different rud kohi/streams/rivers for the development of the area. Sakhi Sarwar area of Dera Ghazi Khan (South Punjab) yielded fossil of new Tomistominae (False Gharial) Gavialidae and further its surroundings recently yielded fossils of famous vertebrates like reptiles (dinosaurs, crocodiles, pterosaur and snake), birds and mammals, and tracks/trackways of Late Cretaceous archosaurs like Sauropaonia, Ornithopaonia and Pteropaonia.

Mapping topographic, geophysical and gravimetry data of Pakistana contribution to geological understanding of Sulaiman Fold Belt and Muslim Bagh Ophiolite Complex

Mapping topographic, geophysical and gravimetry data of Pakistana contribution to geological understanding of Sulaiman Fold Belt and Muslim Bagh Ophiolite Complex

Geochemical attributes of Pliocene Dhok Pathan Formation, Eastern Sulaiman Fold and Thrust Belt, Pakistan: implications for provenance, paleoenvironmental, and tectonic settings

Geochemical attributes of Pliocene Dhok Pathan Formation, Eastern Sulaiman Fold and Thrust Belt, Pakistan: implications for provenance, paleoenvironmental, and tectonic settings

Neotectonics of Zindapir Anticline and Sulaiman Fold and Thrust Belt: Inferences from SRTM DEM

The current study deals with the significance of surface dynamics (SDs) and its relationship to tectonics and active erosion in Zindapir Anticline (ZPA) and neighboring Sulaiman Fold and Thrust Belt (SFTB) which is a direct result of transform plate movement between Indo-Pak continent and Eurasia. The Shuttle Radar Topographic Mission Digital Elevation Model SRTM DEM with 30 m resolution was employed to compute SDs; Isobase (IBL), drainage density (DD), relative relief (RR) and vertical dissection (VD) thematic maps for the study area. The results obtained show that the DD, RR, VD and IBL have higher values in north west, central segments and south west of the SFTB, whereas the Zindapir anticline represents dextral movement on its east side while sinistral sense of movement is observed on its western edge. High values of RR and VD correspond to highly incised topography with great surface roughness. The enhanced values of IBL and DD in the northwest, south west and central SFTB correspond to uplifted active topography segments and can trigger medium level earthquakes in this region. The conjugate movement of ZPA is an indication of its neotectonic nature and recent uplift is causing surface deformation which needs to be understood in the context of SFTB development as a result of India-Eurasia transform movement

Neotectonics of Zindapir Anticline and Sulaiman Fold and Thrust Belt: Inferences from SRTM DEM

The current study deals with the significance of surface dynamics (SDs) and its relationship to tectonics and active erosion in Zindapir Anticline (ZPA) and neighboring Sulaiman Fold and Thrust Belt (SFTB) which is a direct result of transform plate movement between Indo-Pak continent and Eurasia. The Shuttle Radar Topographic Mission Digital Elevation Model SRTM DEM with 30 m resolution was employed to compute SDs; Isobase (IBL), drainage density (DD), relative relief (RR) and vertical dissection (VD) thematic maps for the study area. The results obtained show that the DD, RR, VD and IBL have higher values in north west, central segments and south west of the SFTB, whereas the Zindapir anticline represents dextral movement on its east side while sinistral sense of movement is observed on its western edge. High values of RR and VD correspond to highly incised topography with great surface roughness. The enhanced values of IBL and DD in the northwest, south west and central SFTB correspond to uplifted active topography segments and can trigger medium level earthquakes in this region. The conjugate movement of ZPA is an indication of its neotectonic nature and recent uplift is causing surface deformation which needs to be understood in the context of SFTB development as a result of India-Eurasia transform movement

Structural interpretation of frontal folds and hydrocarbon exploration, western sulaiman fold belt, Pakistan

Abstract Seismic reflection profiles and borehole data combined with geological mapping was used to analyze foreland structures with 3-D structural variation, estimates of shortening, and kinematic evolution of western Sulaiman fold belt (SFB), Pakistan. The western SFB is interpreted with passive-roof duplex geometry. The floor thrust (decollement) is interpreted in Triassic strata rather than its inference in Precambrian-Cambrian evaporites. Whereas, the roof thrust (upper detachment) of hinterland vergence is located in Eocene Ghazij shale. Based on seismic data, the folds in the frontal duplex are interpreted as fault-propagation and fault-bend type. They are located over curved and staircase geometry of blind back thrusts. The folds-and-thrusts of EW trend show right-hand en-echelon stepping along NW-SE oriented mountain front due to drag along the western margin of the fold belt. The blind thrusts cut across the hanging-wall flat of the duplex horse with roots in base Triassic at depth of ~4–4.5 km 3D surfaces of reservoir strata show three areas of closed elliptical contours as potential prospects over blind thrusts, with maximum structural relief of ~2200 m. Shortening of 2100 (22%) and 9950 m (47%) is calculated along with thrusts in the frontal duplex with the interpretation of out-of-sequence structures. Passive roof duplex structures between foreland and hinterland vergent back-thrusts are reported from mountain belts around the world. We have identified out-of-sequence deformation in the frontal duplex with stacked structures. Identification of these features adds to our understanding of the development of mountain fronts in the context of Anderson's theory of faulting with the presence of a conjugate set of faults and foreland propagation of mountain fronts with secondary out-of-sequence deformation. Subsurface seismic data appears to be critical in their recognition for analysis of active foreland deformation and assessment of hydrocarbon plays in the fold belts.

Geometry and development of Zindapir Anticlinorium, Sulaiman Range, Pakistan

Surface geological (field and Landsat images) and subsurface geophysical (seismic reflection and borehole) data were analyzed for geometry and development of N-S oriented frontal Zindapir anticlinorium in the Sulaiman Range, Pakistan. The anticlinorium with its four segments of structural relief (salients), north to south as Dhodak, Rodho, Affiband, and Zindapir, extends over about 130 km with east-vergence of the fold axis, of general NS trend, highly oblique to the plate convergence vector. Based on seismic and well data correlation, sedimentary strata are interpreted with an east to west increase in thickness over the basement, along the western passive margin of the Indian plate. The basement is modelled to have NS trend with gentle ~2.5° westward dip. NS well correlation along the fold axis and seismic reflection interpretation depict structural relief of 2–4 km along different salient's. Based on seismic reflection profiles, shallow-rooted pop-ups in Tertiary and Cretaceous strata are interpreted, contrary to their earlier interpretation as thick-skinned structures. The core of the anticlinorium is occupied with duplication of Jurassic and older (Triassic) strata, of flat-ramp-flat geometry, as a fault-bend fold, and an anticlinal stack, due to variable shortening from edges to the centre (across strike) of the anticline. It is interpreted to develop along lateral ramps, oblique to the direction of tectonic transport, along the eastern edge of the Sulaiman fold belt (SFB). Shortening along the Zindapir anticlinorium reflects a fraction of 37 mm/yr convergence along thrust faults of flat-and-ramp geometry. The Zindapir anticlinorium serves an example for better understanding of oblique mountain fronts, active tectonics, and hydrocarbon exploration in the region.

Heavy metals contamination in soil and food and their evaluation for risk assessment in the Zhob and Loralai valleys, Baluchistan province, Pakistan

This study determined the heavy metals (HM) contamination in soil and food of Zhob and Loralai valleys of Sulaiman fold belt, Baluchistan province, Pakistan. For this purpose, soil and food (food crops and fruits) samples were collected and analyzed for the HM using atomic absorption spectrometry (Perkin Elmer, AAS-PEA-700). Among HM, the iron (Fe) showed highest concentration in soil and food, followed by manganese (Mn), nickel (Ni) and chromium (Cr), while lowest for cadmium (Cd). Results revealed multifold higher contamination factor (CF), pollution load index (PLI) and ecological risk index (ERI) values for soil in the Zhob valley as compared to Loralai valley. Plant enrichment factor (PEF) for Cr, Ni, Fe and Cu were 18.3, 13.6, 12.7 and 11.4. Elevated PEF values led to higher plant bioaccumulation factor (PBF) and resulted in the potential health risk. The HM contaminations were evaluated for daily intake of metal (DIM) and hazard quotient (HQ). Results showed that HQ values >1 for Cd and Ni to the exposed population through food consumption in the Zhob valley. Higher risk in the Zhob valley was due to higher contamination that could be attributed to denudation of ophiolites.

Application of integrated clustering and petrophysical-microscopic methods for facies determination of Campanian–Maastrichtian and Danian–Thanetian reservoirs: Constraints for tectonostratigraphic influences on sedimentation across the NW Indian Plate margin

This paper focuses on reservoirs study in tectonostratigraphic perspective using soft computing multivariate statistical technique of clustering analysis (CA) to delineate electrofacies (EF) for rock typing. The EF knowledge was combined with petrophysics, rock fabric number (rfn) and application of microscopic studies comprising thin sections (TS), scanning electron microscopy (SEM), back scattered electron (BSE) and energy dispersive X-Ray spectroscopy (EDS) on fauna acquired from novel drill cuttings of selected wells. The methods were implemented on data of eight exploratory wells from eastern Sulaiman sedimentary basin (Pakistan) to investigate tectonostratigraphic influences and reservoir characteristics of the Campanian–Maastrichtian, and Danian–Thanetian reservoirs. The Danian-Thanetian (Upper and Lower Ranikot Formations) demonstrate good reservoir rocks in the Sulaiman Fold Belt (SFB) and the northern part of the Zindapir (ZA), however, in the Sulaiman Depression (SD), the Danian-Thanetian reservoirs are shale-rich bearing poor reservoir potential based on EF log correlation. The presence of glauconite (Gl) in the Paleocene Ranikot intervals suggests transgressive (TST) or early highstand system tract (HST) for this particular formation. This evidence is further supported by the occurrence of planktonic foraminifera (Pl), the abundance of which is indicative of late TSTs and early stage HSTs. The presence of Pl in the Campanian Parh Limestone indicates an open sea environment. The clay minerals (kaolinite, chlorite, montmorillonite) occurrence in Maastrichtian Pab Sandstone suggest the detrimental effect on reservoir quality, hindering permeability and fluid flow, proposing this particular formation as a tight reservoir. The kaolinite clay type in the Lower Ranikot Sands in the northern part of ZA characterize continental to near-shore sediments, indicative of fluviatile environment. The Maastrichtian Mughal Kot Formation in the SFB indicates arkosic sandstone (feldspar-rich) with some micaceous content and montmorillonite.The findings from the EF correlation of different wells demonstrate that the reservoir rocks in the SD to the southeast are more shale rich in comparison to those encountered in the SFB in the northeast and northwest. The rfn suggests class 1 type rock fabric (grain dominant) for the Cretaceous Parh Limestone. Due to incomplete logging data, it was not possible to derive rfn for Paleocene formations. The results validate the reservoir heterogeneities on microscopic and small-scale using drill cuttings and well logs.Geologically, active tectonics during the Cretaceous and Paleocene, local sea level fluctuations, diagenesis, clay mineralogy and paleo-topography have strongly affected the lateral variation of facies of Campanian–Maastrichtian, and Danian–Thanetian reservoirs. Moreover, regional active tectonics (Himalayan Orogeny) spanning the Cretaceous and Paleogene Periods also played a major role in crafting the reservoir architecture of various rock units. The results demonstrate the Campanian–Maastrichtian and Danian–Thanetian reservoirs as promising exploratory targets in the SFB. The comparison of the achieved outcomes showed a close agreement with the lateral facies variation in Cretaceous (Campanian–Maastrichtian) and Paleocene (Danian–Thanetian) across the study area.

Potentially harmful elements contamination in water and sediment: Evaluation for risk assessment and provenance in the northern Sulaiman fold belt, Baluchistan, Pakistan

This study was aimed to investigate the potentially harmful elements (PHE) contamination and provenance in water and sediments of Zhob and Loralai valleys, northern Sulaiman fold belt (SFB), Baluchistan province, Pakistan. For this purpose, groundwater (springs, dug wells, bore wells and tube wells), surface water (Zhob River, Loralai River and tributaries) and sediments samples were collected and analyzed for physicochemical parameters including PHE. The concentrations of PHE including iron (Fe2+), nickel (Ni2+), lead (Pb2+), cobalt (Co2+), chromium (Cr3+) and cadmium (Cd2+) surpassed the world health organization (WHO) drinking water guidelines in 71%, 76%, 71%, 57%, 67% and 45% of samples in Zhob valley, respectively. Determined PHE concentrations in drinking water were evaluated for the potential risk assessment through average daily intake (ADI) and hazard quotient (HQ). Among PHE, the highest mean (0.12 mg/kg-day) ADI values were noted for Fe2+ and HQ for Cr3+ (1.95), surpassed the safe threshold limit in Zhob valley. Highest contamination factor (CF) values were found for Fe2+, Mn2+, Ni2+, Cu2+, Co2+, Cr3+ and Cd2+ in Zhob valley, while Zn and Pb in Loralai valley. Statistical analysis such as inter-metals correlation, one-way ANOVA and principal component analysis (PCA) showed that major sources of PHE contamination are geogenic.

Possible origin of inert gases in hydrocarbon reservoir pools of the Zindapir Anticlinorium and its surroundings in the Middle Indus Basin, Pakistan

The natural gas in several gas fields in Pakistan is associated with varying percentages of inert gases (e.g., CO2, N2, and H2S). The heating capacity of such natural gas is measured in British thermal units (BTU) in Pakistan and is based on the combustion of the natural gases. The study area of this work belongs to the Middle Indus Basin, which also covers some parts of the Sulaiman Foldbelt and the Punjab Platform. Petroleum wells drilled in the study area contain inert gases (mostly CO2 and N2) in varying percentages, which decreases the BTU value of sweet gases and the economic value of the gas reserves.Attempts were made to analyze the varying compositions of inert gases (mostly CO2 and N2) along the deep-seated basement faults in the Zindapir Anticlinorium, eastern Sulaiman Foldbelt, but no specific relation could be established. Similarly, geothermal gradient zones were identified and the distribution of inert gases in these zones was studied, but even so, no well-established relation could be tracked. However, variations in the amounts of inert gases in the Chiltan Limestone of the Rodho Structure and the Afiband Structure point to the generation of in situ inert gases because both wells were drilled on the same anticlinorium and share the same geology, and possibly, the same source rock. Post-accumulation changes probably play an important role in the generation of in situ inert gases in varying concentrations. H2S is also present in some parts of the Indus Basin. Therefore, a brief discussion about the possible origin of the H2S is also included in this paper.

Structural and Stratigraphical Interpretation of Seismic Profiles along Safed Koh Trend (Eastern Part of Sulaiman Fold Belt), Pakistan

Safed-koh Trend is located in D.G.Khan district, Punjab province, Pakistan. It is a north south trending fold belt that lies in Eastern Part of Sulaiman Fold Belt. Seismic data correlation is done with the help of well data, Formations' tops, Synthetics and general stratigraphy of the area. The Structural and Stratigraphical interpretation shows subsurface variations. Depth model shows Dhodak, Rodho, Afiband and Zindapir anticlines, the four culminations of Safed-Koh Trend without marking the faults. Dhodak is a northern lower most culmination. Zindapir is the most uplifted one and broader structure comparatively that lies at southern edge. 3D subsurface Time & Depth models of Rubbly Limestone, Dunghan Formation, Pab Sandstone, Lower Goru Formation and Chiltan Limestone map Dhodak anticlinal structure with reverse faults at its flanks. Dunghan, Ranikot, Pab and Chiltan Formations in this area have already proved to be good quality reservoirs for gas. Pab Sandstone and sands of Lower Goru Formation of Cretaceous and Chilton Limestone of Jurassic age could also be the important reservoirs in unexplored area. Rock Physics analysis of Chilton Formation confirms the hydrocarbon potential.

Study of a Stratigraphic Trap of Paleocene/Late Cretaceous Age with the Help of Seismic Data in Sulaiman Foredeep and Kirthar Foredeep Area (Central & Southern Indus Basin, Pakistan)

The Research work comprises area of Punjab Platform, Sulaiman Foredeep and Eastern Part of Sulaiman Fold Belt (from east to west), which is further extended to Zamzama and Dadu area of Lower Indus Basin. Seismic data interpretation suggests a presence of a stratigraphic trap of Paleocene/Late Cretaceous age. It can act as a stratigraphic trap of reservoir quality for hydrocarbons. This feature is marked and discussed on various seismic sections. Sometimes it is difficult to locate this feature due to effect of folding, resulting from later compressions associated with a collision of Indian Plate. This structure could be explored for a hydrocarbon prospect in future. Such stratigraphic traps were not explored in the past.

Study of an Uplift of Sargodha High by Stratigraphical and Structural Interpretation of an East-West Seismic Profile in Central Indus Basin, Pakistan

Research Area comprises of Punjab Monocline, Sulaiman Foredeep and Eastern Part of Sulaiman Fold Belt (from east to west) in Central Indus Basin, Pakistan. Sargodha High is located in northeast of a Seismic Profile AB. Time and Depth models show the subsurface crustal variations near Sargodha High, which separates Upper Indus Basin from Central Indus Basin. The deposition of Pre-Cambrian sediments is uniform in area and Paleozoic sediments (Permian & Cambrian) are thinning in west. Mesozoic sediments (Cretaceous, Jurassic & Triassic) and younger sediments (Paleocene) are not deposited in this part suggesting an uplift of Sargodha High during Paleozoic time. An uneven distribution of Paleozoic rocks shows some thickness in east but erosion, thinning and almost truncation in west indicate their depocenter in east. This also represents a time of uplift of Sargodha High that shifts depocenter westward. Seismic data show a thick Mesozoic deposition in west, which onlaps on the Permo-Triassic unconformity suggesting an area of non-deposition. The gradual uplift of Sargodha high continues, which tilts the Mesozoic strata forming wedge shape geometry.

Provenance of Cenozoic sedimentary rocks from the Sulaiman fold and thrust belt, Pakistan: implications for the palaeogeography of the Indus drainage system

Abstract: The provenance of middle Eocene to early Miocene sedimentary rocks cropping out in the Sulaiman fold and thrust belt has been determined examining the mineralogy, bulk-rock major and trace elements, and Nd–Sr isotopes. The older (50–30 Ma) deposits are characterized by a mixed orogenic provenance with a major contribution from the Karakorum and the Tethyan belt ( c . 80%). As the 50–30 Ma deposits have a provenance distinct from that of coeval Subathu, Khojak and Ghazij shallow marine formations of India and Pakistan, we propose that they were deposited as a distinct delta system that once fed the Palaeo-Indus fan. We document a major change in provenance that occurred before the early–late Oligocene transition at c . 30 Ma. This change in provenance is marked by the appearance of chlorite and monazite and a shift toward more radiogenic Nd–Sr isotopic compositions. We interpret this change as the result of the exhumation and erosion of the proto-Higher Himalaya. The 30–15 Ma sampled rocks are characterized by a major contribution from the Tethyan belt and the Higher Himalayan Crystallines (70–90%) and a subordinate contribution (10–30%) from the Karakorum, Ophiolitic Suture and Trans-Himalaya. As the εNd(0) values of our 30–15 Ma samples are similar to those of the Palaeo-Indus fan deposits, we suggest that the 30–15 Ma sedimentary rocks of the Sulaiman fold and thrust belt were the fluvial onshore record of the Indus fan. Other coeval deposits of India and Pakistan recorded similar increasing exhumation of the Higher Himalaya range, so that we postulate that these sedimentary rocks all derived from the Palaeo-Indus drainage basin. This would suggest that the modern Indus drainage basin is no younger than 30 Ma.

Étude magnétostratigraphique préliminaire sur l'âge du bassin de Rudgai-Sibi (Nord-Est du Balouchistan, Pakistan) et ses implications tectoniques

A first magnetostratigraphic study was carried out in Neogene fluvial formations of the Rudgai (Sibi) basin in the Sulaiman Fold Belt. In order to date these units more precisely and to understand the tectonic implications for the formation of this basin, a total of 59 samples were analysed in the laboratory. The results show that a unique correlation is possible between the observed magnetic polarity stratigraphy and the magnetic polarity stratigraphy scale. This allows us to place the sequence between 16.5 and 14.8 Ma and to show that the molassic sediments are well diachronic between the Rudgai (Sibi) basin (16.5 Ma) the basins of the Potwar Plateau (10.1 Ma).