Evolution of the Himalayan foreland basin, NW India

Abstract

This paper provides new information on the evolution of the Himalayan foreland basin in the underreported region of the Kangra and Subathu sub-basins, NW India. Comparisons are made with the better documented co -eval sediments of Nepal and Pakistan to build up a broader picture of basin development. In the Subathu sub-basin, shallow marine sediments of the Palaeocene^lower Lutetian Subathu Formation are unconformably overlain by the continental alluvial Dagshai and Kasauli Formations and Siwalik Group.The start of continental deposition is now dated at younger than 31 Ma from detrital zircon ¢ssion track data, thereby de¢ning the duration of this major unconformity, which runs basin-wide along strike. Final exhumation of these basin sediments, as thrusting propagated into the basin, occurred by 5 Ma constrained from detrital apatite ¢ssion track data. In the Kangra sub-basin, the Subathu Formation is not exposed and the pre-Siwalik sediments consist of the Dharamsala Group, interpreted as the deposits of transverse-draining rivers. In this area, there is no evidence of westerly axial drainage as documented for coeval facies in Nepal. Similar to data reported along strike, facies analysis indicates that the sediments in NW India represent the ¢lled/over¢lled stages of the classic foreland basin evolutionary model, and the under¢lled stage is not represented anywhere along the length of the basin studied to date.

Chemical fluxes from time series sampling of the Irrawaddy and Salween Rivers, Myanmar

“…The sediments of the upper Irrawaddy basin include volcanics from a Cretaceous arc and sediments shed during the collision (Stephenson and Marshall, 1984;Maury et al, 2004;Najman et al, 2004;Szulc et al, 2006;Allen et al, 2008) as well as subduction related intrusive igneous rocks post-collision (Darbyshire and Swainbank, 1988 K a t h a -G a n g a w & T a g a u n g -M y i t k y i n a b e l t s Cretaceous age by the Kaladan Fault. The Indo-Burman hills accreted as forearc flysh above the Sunda Arc subduction zone (Allen et al, 2008).…”

Lithology, Monsoon and Sea-Surface Current Control on Provenance, Dispersal and Deposition of Sediments over the Andaman Continental Shelf

“…The Irrawaddy River flows, in its upper reaches, through the Gangdese batholith, metamorphic rocks and ophiolites of FIGURE 3 | The lithology map of the drainages of the Irrawaddy, the Salween and the Tanintharyi River basins falling in the Tibet, China, and the Myanmar, modified after (Awasthi et al, 2014;Chapman et al, 2015). possible eastern continuation of the Indus Tsangpo Suture Zone, the volcanics from a Cretaceous arc and sediments produced during the collision (Stephenson and Marshall, 1984;Maury et al, 2004;Najman et al, 2004;Szulc et al, 2006;Allen et al, 2008), associated post-collision intrusive igneous rocks (Darbyshire and Swainbank, 1988) and basic/ultrabasic rocks of the eastern syntaxis of the Himalaya. In the middle reaches, the Irrawaddy drains the Mogok Metamorphic Belt containing schists, gneisses, marble, migmatites, and calc-alkaline plutonics (Figure 3; Chapman et al, 2015).…”

The youngest marine deposits preserved in southern Tibet and disappearance of the Tethyan Ocean

“…The Subathu Formation dated at 44 Ma (Bhatia and Bhargava, 2006), can be correlated with the Bhainskati Formation of central Nepal. It represents the youngest preserved marine sediments in the Himalaya foreland basin, and is unconformably overlain by alluvial sediments of the Dagshai and Kasauli formations (dated at 31 Ma) (Najman et al, 2004;Najman, 2006;Bera et al, 2008). Unlike the massive limestones of the Kohat and Patala formations, the Subathu Formation consists of variegated shales, bioclastic limestone intercalations and fine grained sandstone beds (Singh, 1978).…”

“…In the Lesser Himalaya, Oligocene to Miocene continental sediments overlie Middle Eocene marine strata above a major regional unconformity, indicating a significant hiatus, which marks the change from marine conditions in the Himalayan foreland (Najman et al, 2004). Balakot is a frontier area on the northern Indian margin in the Kashmir syntaxis.…”