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[HCG21-P05] Reconstruction of paleoclimate and environmental fluctuations by paleosol study in the intermontane collision basin of the Indus Molasse, Ladakh Himalaya, India.
Keywords:Molasse, Himalaya, Miocene, Orogenic belt
Ladakh, in northwestern India, the Paleogene – Neogene sediments known as the Indus Group, formed just before the final uplift of the Himalayas, are distributed (Fuchs, 1979; Gansser, 1977). This region is currently intermontane basin located between the southern High Himalaya and Tethys Himalaya belts and the Ladakh Batholith, which is an igneous arc at the southern margin of the Asian continent, forming part of the long basin along the Indus-Tsangpo Suture Zone (ITSZ) (Allegre et al., 1984). The deposition spans from the Eocene to the Late Miocene (Searle et al., 1989; Henderson et al., 2010), potentially recording long-term environmental changes caused by the collision of the Asian and Indian continents in the Western Himalayas.
This study aims the reconstruct of environmental changes, particularly climate fluctuations, from the Oligocene to the Miocene, based on the examination of paleosols within the Indus Group developed along the Zanskar River and Manali Leh Highway in the Ladakh region. The lower part of the Indus Group consists predominantly of continental sediments formed in fluvial continental environments, excluding the lowermost marine strata. Subtropical to semi-arid red soils such as Oxisols and Alfisols developed around river areas, indicating tropical monsoon climate conditions with low precipitation, low groundwater levels, and long dry periods. The uppermost Indus Group (Late Miocene?) contains lacustrine facies and fluvial conglomerates with alluvial fan deposits, where Alfisols and Inceptisols developed around river areas. The presence of gleying suggests higher precipitation and groundwater levels, indicating deposition under conditions of strong seasonality (subtropical monsoon climate with high precipitation).
This indicates that during the Paleogene period, the region was situated by a subtropical monsoon climate with low precipitation, whereas in the Miocene period, precipitation increased. Therefore, it is suggested that the Himalayas to the south had significantly lower altitudes or that the region was a broadly open basin to the west, allowing the intrusion of moist monsoon rainfall.
References
[1] Fuchs, G. 1979. On the geology of western Ladakh. Jahrbuch Geologischer undesanstalt, A122, 513-540.
[2] Gansser, A. 1977. The great suture zone between Himalaya and Tibet, a preliminary account, in Himalaya. Sciences de la Terre, Colloque International Du CNRS Paris, 268, 181–191.
[3] Allégre, C.J.et al., 1984. Structure and evolution of the Himalayan-Tibet orogenic belt. Nature, 307, 17-22.
[4] Searle, M.P., Pickering, K.T., and Cooper, D.J.W., 1989, Restoration and evolution of the intermontane Indus molasse basin, Ladakh Himalaya, India. Tectonophysics, 174, 301-314.
[5] Henderson, A.L., Najman, Y., Parrish, R., Fadel, R., Barford, D., Garzanti, E. and Ando, S. 2010. The geology of the Cenozoic Indus Basin sedimentary rocks; palaeoenvironmental interpretation of sedimentation from the western Himalaya during the early phases of India–Eurasia collision. Tectonics, 29, 1-35.
This study aims the reconstruct of environmental changes, particularly climate fluctuations, from the Oligocene to the Miocene, based on the examination of paleosols within the Indus Group developed along the Zanskar River and Manali Leh Highway in the Ladakh region. The lower part of the Indus Group consists predominantly of continental sediments formed in fluvial continental environments, excluding the lowermost marine strata. Subtropical to semi-arid red soils such as Oxisols and Alfisols developed around river areas, indicating tropical monsoon climate conditions with low precipitation, low groundwater levels, and long dry periods. The uppermost Indus Group (Late Miocene?) contains lacustrine facies and fluvial conglomerates with alluvial fan deposits, where Alfisols and Inceptisols developed around river areas. The presence of gleying suggests higher precipitation and groundwater levels, indicating deposition under conditions of strong seasonality (subtropical monsoon climate with high precipitation).
This indicates that during the Paleogene period, the region was situated by a subtropical monsoon climate with low precipitation, whereas in the Miocene period, precipitation increased. Therefore, it is suggested that the Himalayas to the south had significantly lower altitudes or that the region was a broadly open basin to the west, allowing the intrusion of moist monsoon rainfall.
References
[1] Fuchs, G. 1979. On the geology of western Ladakh. Jahrbuch Geologischer undesanstalt, A122, 513-540.
[2] Gansser, A. 1977. The great suture zone between Himalaya and Tibet, a preliminary account, in Himalaya. Sciences de la Terre, Colloque International Du CNRS Paris, 268, 181–191.
[3] Allégre, C.J.et al., 1984. Structure and evolution of the Himalayan-Tibet orogenic belt. Nature, 307, 17-22.
[4] Searle, M.P., Pickering, K.T., and Cooper, D.J.W., 1989, Restoration and evolution of the intermontane Indus molasse basin, Ladakh Himalaya, India. Tectonophysics, 174, 301-314.
[5] Henderson, A.L., Najman, Y., Parrish, R., Fadel, R., Barford, D., Garzanti, E. and Ando, S. 2010. The geology of the Cenozoic Indus Basin sedimentary rocks; palaeoenvironmental interpretation of sedimentation from the western Himalaya during the early phases of India–Eurasia collision. Tectonics, 29, 1-35.