Emergence and evolution of Himalaya: reconstructing history in the light of recent studies

Abstract

India collided with mainland Asia at 65 Ma. The pressure rose to 9-11 kbar in the collision zone. As the Indian lithosphere bent down and its upper crust buckled up as an upwarp in the period 35-45 Ma, the southern margin of Asia became the water-divide of the Himalayan rivers. A variety of Eurasian fauna migrated to the Indian landmass. The southern margin of the Himalayan province synchronously sagged to give rise to the foreland basin that was linked with the Indian sea. In this Paleocene foreland basin 48-49 Ma ago, the whales from one of the species of the immigrant terrestrial mammals evolved. The sea retreated from the Himalayan province by the early Miocene, even as the crust broke up along faults 20-22 million years ago. The basement rocks, which had attained high-grade metamorphism at 600-800°C and 6-10 kbar, were thrust up to give rise to what later became the Himādri or Great Himalaya. Differential melting of the high-grade metamorphic rocks of the Himadri extensively produced 21 ± 1 Maold granites. Rivers carried detritus generated by the denudation of the fast emerging Himalaya and deposited it in the foreland basin which turned fluvial around 23 Ma. Another fluvial foreland basin, the Siwalik, was formed at ~18 Ma in front of the rapidly rising orogen and was filled by river-borne sediments at the rate of 20-30 cm year-1 in the early stage and at 50-55 cm year-1 later when the Himadri was uplifted and briskly exhumed in the Late Miocene (9-7.5 Ma). The Himadri then became high enough to cause disruption of wind circulation, culminating in the onset of monsoon. The climate change that followed caused migration of a variety of quadrupeds from Africa and Eurasia, bringing about considerable faunal turnovers in the Siwalik life. Spasmodic uplift of the outer ranges of the Lesser Himalaya and tectonic convulsion in the Siwalik domain at 1.6 Ma resulted in widespread landslides with debris flows and emplacement of the Upper Siwalik Boulder Conglomerate. Strong tectonic movements at 0.8 Ma caused the partitioning of the foreland basin into the rising Siwalik Hills and the subsiding IndoGangetic Plains, and also the initiation of glaciation in the uplifted domain of the Great Himalaya. After the end of the Pleistocene ice age around 0.2 Ma, there was oscillation of dry-cold and wet-warm climates. This climatic vicissitude is recorded in the sediments of the lakes that had formed because of reactivation of faults crossing rivers and streams. Activeness of faults, continuing uplift and current seismicity imply ongoing strain-buildup in the Himalayan domain.

Genomics of the origin and evolution of Citrus

“…1c, d), a period coincident with an extensive weakening of monsoons and a pronounced climate transition from wet to drier conditions 17 . In southeast Asia, this marked climate alteration caused major changes in biota, including the migration of mammals 18 and rapid radiation of various plant lineages 19,20 . Australian citrus species form a distinct clade that was proposed to be nested with citrons 12 , although distinct generic names (Eremocitrus and Microcitrus) were assigned in botanical classifications by Swingle 1, 5 .…”

Hydrogeological typologies of the Indo-Gangetic basin alluvial aquifer, South Asia

“…The basin is a foredeep depression, which has formed in front of the Himalaya as a result of the orogenic uplift and loading, and contains two main basin systems: the Indus basin in the west which deepens longitudinally away from the Himalaya towards the coast; and the Ganges basin in the central and eastern part of the foredeep which deepens transverse to the Himalaya towards the Bay of Bengal (Valdiya 2002;Singh 2007; Fig. 3).…”

“…It can arise from a combination of natural processes and is exacerbated in some areas by centuries of irrigation. The IGB basin has not been subject to widespread marine transgression (Schroder 1993;Valdiya 2002;Goodbred 2003) and the salinity in the Indus basin and Upper Ganges is almost entirely due to terrestrial processes. Only in the coastal regions of the Bengal Basin and Pakistan is there evidence of historical and current marine influence (Schroder 1993;BGS and DPHE 2001).…”

Diversification of the cold-adapted butterfly genus Oeneis related to Holarctic biogeography and climatic niche shifts

“…2), contemporary to the uplift of the Himalayas and adjacent ranges (Valdiya, 2002;De Grave et al, 2007). The uplift promoted the speciation of mountain birds (Fjeldsa et al, 2012;Drovetski et al, 2013), plants (Xu et al, 2010), but also cold-adapted butterflies (Kodandaramaiah and Wahlberg, 2009;Leneveu et al, 2009).…”