Cretaceous- Paleocene)

A beautiful nature-the Himalaya

Upendra BARAL P.hD.

Key Laboratory of Continental Collision and Plateau Uplift

Institute of Tibetan Plateau Research, Chinese Academy of Sciences WHEN?? Where??

Indian plate Asian plate India-Eurasia initial collision India-Gondwana breakup and collision with Asia

India drifting towards Eurasia

separation of India from Antarctica– Australia along the Southeast Indian Ridge

Initial breakup of Eastern Gondwana from Western Gondwana Importance of Collision study

• India-Asia collision is most spectacular geological event that formed the vast and high Tibetan Plateau • This event affects Tibet as well as central and southeast Asia • The initial collision is importance for the study of continental lithospheric deformation, environmental changes, paleoaltitue reconstruction • The collision is ongoing process, initiated by “soft collision” and remained constant as “hard collision” that leads to the loading of an accretionary prism onto a passive continental margin and formed the foreland basin Important Proxies to constrain the collision age

• Faunal/ Fauna migration • Study of Magmatic rocks (e.g., Eclogite) exposed within the suture zone • Provenance analysis (geochronology Magmatic records from the THS- during the early stage of collision • Linear exposure of granitic rocks in Himalayan belt: Olig-Miocene Leucogranite and Middle Eocene granites • Eocene granites were derived from partial melting of the thickened lower crust- • Earliest stage of magmatism formed during the collision and subduction of Neo-Tethyan slab break-off • The Neo-Tethyan slab break-off was almost synchronous along the entire IYSZ during middle Eocene (ca. 45 Ma) Research progress regarding the India-Asia collision age • Tectono-sedimentary responses to the Initial collision • Deformation of the northern THS in the early collision stage • Island arc formation, and accretionary complex and trench strata emplaced on the northern margin of Indian plate. • Increase the flexure load and formation of the first peripheral foreland basin • Development of a peripheral foreland basin system • Formation is related to the collision • Argument that Miocene is the first basin formed due to collision while in Tibet Ding and team marked the basin closer to IYSZ developed between 65 Ma and 60 Ma • Cessation of marine sedimentation • Transition from marine to terrestrial facies ( an indicator of India-Asia collision in late 19s) • E.g., Balakot Fm ( 55 Ma and 50 Ma) is the oldest terrestrial foreland basin deposit • In Tibet, this transition is recorded in the early Eocnene The deposition of marine sediments would not have ended immediately after the onset of collision, the age of these strata only reflects an upper bound of the collision time, limiting the application of this approach • Paleolatitudes of Greater Indian (GI) and the TH Sangdalin Formation (Southern Tibet)

The Sangdalin Formation (Paleocene-early Eocene), contains typical foredeep deposit and in Saga area the environmental change took place between 65 Ma and 63 Ma which suggest the collision age ca. 65 Ma ( Ding et al 2005) or ca. 60 Ma (Wu et al 2014). Paleolatitudes of Greater Indian (GI) and the TH

• GI is the region to the north of the Indian plate, including under-thrusted Indian lithosphere and crustal shortening in the Himalaya mountain belt • The paleomagnetic study in Tibet have shown the age of Zhongshan Formation as 71 Ma and 65 Ma and Zhongpu Fm between 63 Ma and 55 Ma. • Recent development is that the Cretaceous paleomagnetic results from the Lhasa and TH block indicated the existence of ca.2675 km GIB between THS and Indian Craton. Paleolatitude of southern margin of Asia • Numerous paleomagnetic study in Cretaceous to Eocene lavas and sedimentary strata from the Lhasa block and have shown a large variation in collision age between 65 Ma and 43 Ma. • This variation is due to the compacted sediments, the incomplete field characterization of lavas, re- magnetized rocks and improper statistical methods • The Lhasa block was located at between ca. 16°N and 22°N during Cretaceous to Paleogene (Lippert et al 2014) and the collision age is 52 Ma ( youngest age) • Most recent geochronology and paleomagnetic study from upper Cretaceous volcanic rocks in western Lhasa have shown the southern margin of Asia probably had a quasi-linear orientation trending ~310° prior to collision and the collision was between 65 Ma and 60 Ma (Yi et al 2011) Comparison of different timings for the collision between India and Asia as well as events across the THS resulting from the application of different methods Time and Location of Contact between Indian and Eurasian Plates

Initial contact between Indian and Asian plates The initial contact between Indian and Asian plate took in Northwestern section (e.g. Beck et al., 1995) In a central part of the IYSZ between ca. 65 Ma and 63 Ma and then spread both eastward and westward (e.g. Bin Zhu et al., 2005; Cai et al., 2011; Ding et al., 2005) Controversy regarding the India-Eurasia collision ~51 Ma (Bin Zhu et al., 2005; Bouilhol et al., 2013; Ding et al., 2005) ~65 Ma and 60 Ma (DeCelles et al., 2014; Ding et al., 2005; Wu et al., 2014) ~65 Ma and 62 Ma (Ding et al., 2017) - Central Himalaya ~55-56 Ma (Ding et al., 2016) –Western Himalaya ~30-25 Ma (Aitchison et al., 2007; Aitchison et al., 2000; Aitchison and Davis, 2001). THE HIMALAYAS and FORELAND BASINS • Sub Himalaya- Siwalik • Coarsening upward ~5 km thick fluvial sediments • Differentiated into Lower, Middle and Upper • Middle Miocene to Early Pleistocene. • Lesser Himalaya • Metasedimentary sequences and associated younger sedimentary rocks with overriding crystalline nappes and klippen • Lower Lesser Himalaya (Proterozoic) / Upper Lesser Himalaya (Paleozoic-Cenozoic) • Higher Himalaya • High-grade crystalline rocks including (gneisses, schists and migmatites). • This zone is tectonically still active due to the activity of MCT. • Granitic intrusions in several places /with high grade rocks • Tethys Himalaya • Comprises Fossiliferous sedimentary • Cambrian to Lower Cretaceous DETRITAL ZIRCON AGES FOR HIMALAYAN UNITS

• Lower Lesser Himalaya: 1.7-2.0 Ga and 2.4-2.8 Ga

• Higher Himalaya: 800-1200 Ma, 1.6-1.9 Ga and 540-750 Ma

• Tethys and Lower Lesser Himalaya : 480–570 Ma, 750– 1200 Ma, and • 2430–2560 Ma. (Gehrels et al., 2011 and references therein) Provenance Analysis

SOURCE

TRANSPORT/BARRIER

BASIN 23 Ma Depositional Depositional Gap

Marine Alluvial 42 Ma 22 Ma ( DeCelles et al., 2004) Cretaceous-Early Miocene Strata • Dumri Formation ( Miocene)

• Alternating beds of greenish grey to reddish brown, fine- to medium –grained sandstones and mudstone intercalated with marl bands is type lithology.

• Bhainskati Formation ( Eocene)

• About 150 m thick shallow marine to brackish water deposits. Limestone with some lenses of fossiliferous limestone intercalated with red- purple pencil cleavage shale.

• Amile Formation ( Cretaceous- Paleocene)

• 230 m thick at the type locality. Green to grey colored calcareous sandstone with some shale. Limestone beds yield several types of marine fossils

(DeCelles et al., 2004) Cretaceous-Early Miocene Strata

(Baral et al., 2018) Cretaceous-Early Miocene Strata

• Dumri Formation (Miocene) the ƐHf (t) value from DZ grains of 1600-1800 Ma age are prominently negative indicate the change of source region.

• In Bhainskati Formation (Eocene) and Dumri Formation (Miocene) the DZ grains have both positive and negative

ƐHf (t) values suggest the orogenic source.

• Dominant positive ƐHf (t) values in Amile Formation Indicate that the source is Juvenile crust.

(Baral et al., 2019) Neogene Foreland Basin (Siwalik)

Thick Bedded, well sorted clast supported conglomerate

Thick-beeded medium to coarse grained sandstone “ Salt and pepper” texture”

Variegated mudstone with fine grained sandstone and siltstone

(DeCelles et al., 2004)

(Baral et al., 2017) Neogene Foreland Basin (Siwalik)

Thick Bedded, well sorted clast supported conglomerate

Absence of these Cenozoic zircons in western Nepal, and presence in eastern Nepal foreland basin, implies that the leucogranite in the eastern Himalaya were much more Thick-beeded medium to eroded rather than in western Himalaya. coarse grained sandstone “ Salt and pepper” texture” The Cenozoic grains in the eastern Nepal shows the possibility of the source from the Gangdese arc

However, since ~10 Ma ago the input of the Lesser Himalayan sediments was relatively higher in the Siwalik Group.

Variegated mudstone with fine grained sandstone and siltstone

(Baral et al., 2015a, b, 2017a, b) Eastern Himalayan Cenozoic Foreland Basin

Paleocene-Eocene Yinkiong Group of rocks associated with the Abor Volcanics Lower Yinkiong Formation: Late Paleocene to Early Eocene Geku Formation, deposited in a distal foredeep foreland basin system in the northern Indian passive margin. Upper Yinkiong Formation: Early to Mid-Eocene (Dalbuing Formation) deposited in a foredeep depozone foreland basin system. Eastern Himalayan Cenozoic Foreland Basin

• Absence of Younger detritus Early to Mid Eocene Strata (Upper Yinkiong Formation) • Younger detritus (mid to upper Cretaceous) were probably source from the Asian affinity • Mid cretaceous granitic body are wide spread in Tethyan Himalaya

India-Asia collision in Siang valley NE India, took place during or before early Eocene. Baral et al., 2018 Western Himalayan Cenozoic Foreland Basin

Murree Fm– Sub Himalayan foreland basin, cyclic sequence of shale, and mudstone with some siltstone and sandstone Early Miocene

Kuldana Fm – Consists of shale, ,limestone, marl, sandstone and siltstone Unconformably overlain the Muree Fm. Early Eocene (53-43)

Margalla Hill Lst and Chorgalli Fm– Consists of nodular Lst, with thin arenaceous shale bed. Early Eocene (55-53)

Patala Fm- Consists of brown shale and minor sandstone, siltstone and dark gray Lst. Disconformable contact with Margalla Lst (~2m Conglomerate bed). Late Paleocene (57-55) Western Himalayan Cenozoic Foreland Basin

Absence of Asian Affinity detritus – Indian affinity provenance for the Patala Formation, and erosional surface present in this Formation was formed during ca.~56-55 Ma

First presence of Cretaceous-Eocene detritus at Early Eocene Sequence ( Chorgalli Fm and Margalla Hill Lst)- minimum age constrain on the India-Asia collision Ding et al., 2018 Collision patterns and suturing processes

During the oceanic lithosphere subduction and complete subducted, in either side of the plate experience intense deformation, indicate the initiation of collision. The shift in provenance and the change of depositional environments in the foreland basin could be a result of the collision between the Indian and Asian plates.

The India-Asia collision took place during or before early Eocene (i.e., ~56-50 Ma) in eastern Himalaya ~65-60 Ma in central and ~55-52 Ma in western Himalaya

India-Asia collision first took place in central Himalaya and laterally migrated towards an east-west direction.

Thanks for your attention

https://www.researchgate.net/profile/Upendra_Baral2 [email protected] , [email protected] Structures (Major and minor)

Robinson et al., 2006