Abstract During the Late Neoproterozoic to Early Mesozoic the Indian Plate was part of Pangaea, the Palaeo supercontinent, with the African Plate to the west, as interpreted by various authors. At the same time, the Indian Plate was juxtaposed with the Central Iranian Plate, which separated it from the Arabian Plate in the vicinity of present-day Oman, c. 800 Ma ago. Between 612 and 200 Ma (Late Neoproterozoic to the end of the Triassic) these plates remained firmly attached. The changing configuration of the plates from 200 Ma to the present are provided in this paper. The Neoproterozoic–Cambrian rocks are recorded along the eastern border of Pakistan with India, extending into the Indian Territory and comprising part of the Neoproterozoic–Cambrian basin (Lower Indus Basin). The southern part of the Lower Indus Basin, from the Thar Platform in the east, deepens westwards towards Karachi (embayment) and the Kachhi Foredeep, where the Neoproterozoic–Cambrian succession is likely to be deep-seated. However, c. 5 km uplift of the Kirthar Fold Belt (KFB) across the Western Boundary Thrust (WBT) and the subsequent erosion have exposed the Middle Jurassic Chiltan Limestone, particularly in the central region of the KFB (Landsat images and domal structures with Jurassic outcrops are described in this paper) The limestone rests over older strata, with a possible presence of that of Neoproterozoic–Cambrian age, which is interpreted to be at drillable depth.

Abstract A study of the southern Kirthar fold belt in Pakistan was undertaken to elucidate the hinterland structure and hydrocarbon prospectivity. Interpretation of structure and stratigraphy is difficult because of suboptimal seismic data, a lack of hinterland well data, and a transition from shelfal to basinal stratigraphy. An interpretation of two cross sections was made using outcrop and seismic data and well data from foreland discoveries. The Institut Français du Pétrole Thrustpack ® software was used to validate the structural model and provide data on the maturity of the source rock. The Kirthar fold belt is dominated by open and symmetrical folds that are driven by inversion of basement-involved Jurassic extensional faults. Thrusts have been interpreted with two detachments, thrusts with a shallow detachment in the Eocene mudstones and thrusts with a deeper detachment in the Lower Cretaceous source rock interval that involve the reservoir during deformation. The major mountain-building episode is interpreted as late Pliocene–Pleistocene, but there is evidence for earlier inversion dating from the late Paleocene associated with the emplacement of the Bela ophiolite and constrained by maturity data obtained from outcrop. Early inversion and uplift impacts the burial curve and, thus, the prospectivity of the area.

Abstract The southern Kirthar Fold Belt (KFB) and the contiguous Middle Indus Basin (MIB) constitute a major oil and gas province on the southern Pakistan foreland. In the Middle Indus Basin, gas is reservoired in Early Cretaceous marginal marine sandstones sealed by Paleocene shales. Reservoir quality of the Early Cretaceous sediments deteriorates towards the fold belt, but recent discoveries of gas in Upper Cretaceous sandstones sealed by Paleocene shales have highlighted its potential. To understand better the petroleum systems of this region and provide a potential correlation scheme for comparison with other areas of the country, a sequence stratigraphic interpretation was carried out on the Jurassic to Recent sediments of the KFB and MIB. On the basis of outcrop and well data, 23 depositional sequences have been identified: five in the Jurassic units, 10 in the Cretaceous units and eight in the Tertiary units. Sequence boundaries have been defined according to the Exxon method of identifying unconformities and their correlative conformities. However, equal importance has been given to identifying the potentially more chronostratigraphically significant maximum flooding surfaces between these sequence boundaries so as to define accurately the component systems tracts of each sequence. The depositional systems are described in terms of their relationship to the existing lithostratigraphic framework and interpreted in terms of sedimentary responses to external (eustatic) or local (tectonic) events. Notwithstanding the presence of a eustatic signature on some sequences, the majority appear to be tectonically driven and can be related to plate margin events affecting the NW margin of the Indo-Pakistan Plate during its rift-drift-collision history.

Abstract In 1997 Lasmo Oil Pakistan Ltd (Lasmo) gained a significant position in the offshore Indus Basin with the award of the Indus A and B Blocks. The main hydrocarbon play comprises Miocene shelf-delta sands interbedded with intraformational shale seals and sourced by gas-prone offshore equivalents. Approximately 12000 km of seismic data have been interpreted in the detailed evaluation of these blocks. However, only four wells have tested the preferred play type and no core or rock data were available to provide further insights into facies or age dating. Log data from two key wells in the offshore Indus area record the initial infilling of the basin by shale-dominated basinal or outer shelf sediments, followed by stacked thin-bedded sandstone-shale sequences of a shelf-delta nature. A zone of progradational sequences marks the transition between the two, but no other workable stratigraphic divisions were apparent. Regional seismic correlation established the diachronous nature of the prograding shelf package and this was matched by distinct bands of seismic progrades. A series of simple palaeogeographies of the prograding shelf margin were developed showing initial sediment input from the north and rapid progradation towards the south and west. The Oligo-Miocene basin fill of the offshore Indus Basin appears to be a 'one-step' fill process of a significant depocentre created between the Karachi Platform and the Murray Ridge. Canyons are a very distinct feature on seismic profiles and two main phases of development are apparent. The earlier phase is interpreted to be of Early Miocene age. Downcutting at this time rarely exceeded 400 m. The second phase of canyon development occurred during Plio-Pleistocene time, and these younger canyons often dominate the shallow section, with multiple phases of downcutting sometimes exceeding 1000 m. Where drilled, canyons of both ages have been found to be shale prone. These drilled canyons are interpreted to be on the palaeo-slope where erosion and sediment by-pass occurred during the active phase, and were subsequently filled by fine-grained deposits after abandonment. The two phases of canyoning are considered to relate to phases of tectonic activity in the collision zone between the western margin of the Indo-Pakistan plate and the Eurasian plate.