Structural evolution of the frontal fold–thrust belt, NW Himalayas from sequential restoration of balanced cross-sections and its hydrocarbon potential
Premanand Mishra, Dilip K. Mukhopadhyay, 2012. "Structural evolution of the frontal fold–thrust belt, NW Himalayas from sequential restoration of balanced cross-sections and its hydrocarbon potential", Geology and Hydrocarbon Potential of Neoproterozoic–Cambrian Basins in Asia, G. M. Bhat, J. Craig, J. W. Thurow, B. Thusu, A. Cozzi
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Two sedimentary lithotectonic zones are traditionally recognized in the northwestern Himalayan frontal fold–thrust belt in the Nahan salient: the Lesser Himalaya Zone (LHZ) and the Sub-Himalaya Zone (SHZ). The LHZ is made up of a sequence of Proterozoic to Early Cambrian rocks and the SHZ is made up of Cenozoic rock sequences, which were deposited subsequent to the India–Asia collision. Serial balanced cross-sections show that the structural geometries become increasingly complex from independent ramp anticlines near the foreland through imbricate fan/duplex to stacked-up horses towards the hinterland. Sequential restoration suggests a structural evolution in which a foreland propagating, in-sequence thrusting event was followed by out-of-sequence thrusting in an approximately break-back style. During the out-of-sequence movement, some of the ramps formed during in-sequence thrusting were repeatedly reactivated, leading to very complex structural geometries, particularly in the LHZ. In such a complexly deformed terrain, a rigorous structural modelling approach, combined with a robust geochemical and geochronological database, should be used to carry out calibrated petroleum system modelling, and thus reduce exploration risk.
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This volume provides a comprehensive overview of the geology and hydrocarbon potential of the major Neoproterozoic–Cambrian basins of Asia from Oman, across the Middle East and the Indian Subcontinent, to China and SE Siberia, along with new research on the region. Many of these areas (e.g., Oman, Bikaner–Nagaur Basin in India, South China and SE Siberia) host prolific Neoproterozoic–Cambrian petroleum systems with giant to supergiant fields. Three key elements: (1) tectonic stability, (2) relatively late phase of hydrocarbon generation and (3) presence of an effective evaporite seal, seem to be critical for the development of effective Neoproterozoic–Cambrian petroleum systems. These key elements appear of less consequence for the development of ‘unconventional’ hydrocarbons, and the future prospectivity in many of these basins may lie in the exploration for, and production of, shale gas and shale oil directly from the thermally mature, organic-rich source rocks.