Crystalline klippen over the Lesser Himalayan Metasedimentary Sequence (LHMS) zone in the NW Himalaya have specific syn- and post-emplacement histories. These tectonics also provide a means to understand the driving factors responsible for the exhumation of the rocks of crystalline klippen during the Himalayan Orogeny. New meso- and microscale structural analyses, and thermochronological studies across the LHMS zone, Ramgarh Thrust (RT) sheet and Almora klippe in the eastern Kumaun region, NW Himalaya, indicate that the RT sheet and Almora klippe were a part of the Higher Himalayan Crystalline (HHC) of the Indian Plate which underwent at least one episode of pre-Himalayan deformation and polyepisodic Himalayan deformation in ductile and brittle–ductile regimes. The deformation temperature pattern within the Almora klippe records a normal thermal profile from its base to top but an inverted thermal profile from the base of Almora klippe down towards the LHMS zone. New fission-track data collected across the RT sheet and Almora klippe along Chalthi–Champawat–Pithoragarh traverse in the east Kumaun region document the exhumation of both units since Eocene times. Zircon fission-track (ZFT) ages from the Almora klippe range between 28.7 ± 2.4 and 17.6 ± 1.1 Ma, and from the RT sheet between 29.8 ± 1.6 and 22.6 ± 1.9 Ma; and the apatite fission-track (AFT) ages from the Almora klippe range between 15.1 ± 1.7 and 3.4 ± 0.5 Ma, and from the RT sheet between 8.7 ± 1.2 and 4.6 ± 0.6 Ma. The age pattern and diverse patterns of the exhumation rates reflect a clear tectonic signal in the RT sheet and the Almora klippe which acknowledge that the Cenozoic tectonics influenced the exhumation pattern in the Himalaya.
Hydrocarbon exploration and production are going on in Barmer basin (Rajasthan, India) formore than a decade. The potential source rocks are of Paleocene – Eocene age, and Mesozoicsiltstones form the reservoirs. The western and central portions of the Rajasthan basin arecharacterised by extensive lignite formations, which can be promising for artificialtransformation to oil and gas. We study the source rock properties, depositional environmentsand hydrocarbon generation potential of the Paleogene lignitic shales of the Giral lignite mineand the Cretaceous Sarnu siltstones for their source and reservoir rock potentiality. The totalorganic carbon content (TOC) of the Giral samples range between 0.76-49.83 wt% and thethermal maturity, as reflected by the pyrolysis Tmax, lies between 412-468 ℃. Sarnoo siltstones,on the other hand, have a very low TOC ranging from 0.02-0.08 wt% and a Tmax of 320-608 °C.The higher TOC and a lower oxygen index (OI) of Giral lignites and shaly lignites indicate theprevalence of a reducing depositional environment. Bulk organic geochemical parametersinvolving kerogen pyrolysis and thermal degradation kinetics indicate a more promisinghydrocarbon generation potential in the lignite than shales, which, however exhibits higherthermal maturity of organic matter. Giral lignites as well as shales show dominantly Type-III heterogeneous kerogen, which is sourced from terrestrial organic matter. This is also corroborated by a broader distribution of activation energy derived from the thermal decomposition of the kerogen. The kerogen transformation ratio (KTR) and the hydrocarbon generation rate GR) suggest a considerably earlier and quicker kerogen transformation. Samples from the Sarnoo area offer no significant information on the source rock characteristics, due to their lean organic nature. However, lignites and shaly lignites of the Giral mine are identified as excellent candidates for their suitability towards easy conversion into hydrocarbonproducts through artificial techniques.
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