A review of the geologic history of the Himalayan-Tibetan orogen suggests that at least 1400 km of north-south shortening has been absorbed by the orogen since the onset of the Indo-Asian collision at about 70 Ma. Significant crustal shortening, which leads to eventual construction of the Cenozoic Tibetan plateau, began more or less synchronously in the Eocene (50–40 Ma) in the Tethyan Himalaya in the south, and in the Kunlun Shan and the Qilian Shan some 1000–1400 km in the north. The Paleozoic and Mesozoic tectonic histories in the Himalayan-Tibetan orogen exerted a strong control over the Cenozoic strain history and strain distribution. The presence of widespread Triassic flysch complex in the Songpan-Ganzi-Hoh Xil and the Qiangtang terranes can be spatially correlated with Cenozoic volcanism and thrusting in central Tibet. The marked difference in seismic properties of the crust and the upper mantle between southern and central Tibet is a manifestation of both Mesozoic and Cenozoic tectonics. The form...

Geologic Evolution of the Himalayan-Tibetan Orogen

http://www2.ess.ucla.edu/~yin/05-Publications/papers/091-Yin-2006-ESR.pdf

Cenozoic tectonic evolution of the Himalayan orogen as constrained by along-strike variation of structural geometry, exhumation history, and foreland sedimentation

The Himalaya and Tibet provide an unparalleled opportunity to examine the complex ways in which continents respond to collisional orogenesis. This paper is an attempt to synthesize the known geology of this orogenic system, with special attention paid to the tectonic evolution of the Himalaya and southernmost Tibet since India-Eurasia collision at ca. 50 Ma. Two alternative perspectives are developed. The first is largely historical. It includes brief (and necessarily subjective) reviews of the tectonic stratigraphy, the structural geology, and metamorphic geology of the Himalaya. The second focuses on the processes that dictate the behavior of the orogenic system today. It is argued that these processes have not changed substantially over the Miocene–Holocene interval, which suggests that the orogen has achieved a quasi–steady state. This condition implies a rough balance between plate-tectonic processes that lead to the accumulation of energy in the orogen and many other processes (e.g., erosion of the Himalayan front and the lateral flow of the middle and lower crust of Tibet) that lead to the dissipation of energy. The tectonics of the Himalaya and Tibet are thus intimately related; the Himalaya might have evolved very differently had the Tibetan Plateau never have formed.

Tectonics of the Himalaya and southern Tibet from two perspectives

/pdf/phanerozoic-polar-wander-palaeogeography-and-dynamics-3fc5flnbf0.pdf

Phanerozoic polar wander, palaeogeography and dynamics

The origin and pre-Cenozoic evolution of the Tibetan Plateau

During the Anisian (?Bithynian to Pelsonian) a large carbonate bank, up to 400 m thick, (the Camorelli Limestone) developed in the Lombardian Alps. Many stratigraphic sections were measured in this unit and three basic microfacies were detected, often arranged in sequence from bottom to top: intrabioclastic packstone, bindstone, and bioclastic packstone rich in Foraminifera. The biofacies is dominated by blue-green algae (Spongiostromata and Porostromata) and microproblematicTubiphytes. Benthic Foraminifera are subordinate even if they become locally the main bioclastic component. Dasycladacean algae are rare. These rather undifferentiated microfacies strongly contrast with time-equivalent mound microfacies, as previously pointed out for mounds versus large carbonate bank in the Illyrian. These features can be connected with substratum competition, not fully suitable for sponges in shallower environment at this stage of the Triassic recovering after the Late Permian crisis.

The anisian (middle triassic) carbonate bank of Camorelli (Lombardy, Southern Alps)

A sedimentary sequence overlying a granite pluton near Ishkarwaz (upper Yarkhun valley, Chitral, Pakistan; Karakorum Microplate) contains abundant, but poorly preserved, acritarchs probably referable to the late early Arenig-early late Arenig interval. The palynological assemblages of Karakorum show a marked similarity to the cold water Peri-Gondwana assemblages; i.e. to those of Li Jun's Arbusculidium-Coryphidium-Striatotheca‘Mediterranean’ Bioprovince. Biogeographical and geological comparisons suggest that, before the accretion of Cimmerian microplates to the Eurasian continent, the Karakorum Microplate was located along the northern margin of Gondwana in a latitude intermediate between the Mediterranean region and South China (Yangtze Platform).

Palynological dating (Arenig) of the sedimentary sequence overlying the Ishkarwaz Granite (upper Yarkhun valley, Chitral, Pakistan)

Chitral (Pakistan), geologically, includes the eastern termination of the Hindu Kush and its transition to the Karakorum. The position of the boundary is not precisely defined, and may be located provisionally at the Chitral Fault, or at the Tirich Mir Fault. Four main tectonostratigraphic units are identified. From SE to NW they are:1) Lun Shales (shales and slates with Devonian calcareous intercalations) and Devonian to Permian carbonates. 2) Metabasites , consisting of amphibolites and green tuffs, locally associated with carbonates. 3) Atark Group , mostly metacarbonates in which Permian, Triassic and Cretaceous intervals have been detected. 4) Wakhan Slates , a very thick terrigenous succession of dark colour, partly of Paleozoic age. Huge granitoid bodies have been intruded into this unit. This 4-fold subdivision is here proposed for the first time. A terrigenous-calcareous succession of Permian age has been measured and sampled in the Atark Group at Rosh Gol. Seven lithostratigraphic units have been identified. Six of them contain fossils, mostly fusulinids, allowing identification of Yahtashian, Bolorian, Kubergandian and Late Murgabian or Midian. The most significant species of fusulinids are illustrated; these have close affinities to the Central Pamir.

Permian stratigraphy and fusulinids from rosh gol (chitral, e hindu kush)

https://academiccommons.columbia.edu/doi/10.7916/D85Q55KD/download

Towards a better definition of the Middle Triassic magnetostratigraphy and biostratigraphy in the Tethyan realm

The Elikah River section in the Alborz Mountains (North Iran) is a fossiliferous, continuous, marine section spanning the Permian–Triassic (P–T) boundary interval. Sixty-eight taxa of brachiopods, foraminifers and algae have been collected bed-by-bed from the topmost 36 m of the Nesen Formation and the basal 2 m of the Elikah Formation, across the P–T boundary that is located in the basal metre of the latter formation. Forty-six of these taxa from 62 samples have been considered for statistical analyses to unravel the pattern of extinction. First, their range extensions have been determined, which should be added to the highest stratigraphic occurrence of each taxon to identify the extinction level within a certain confidence interval (95%). Then the pattern of the extinction has been analysed, plotting the stratigraphic abundance versus last occurrence below the extinction horizon. The resulting pattern is of a sudden extinction occurring 30 cm below the biostratigraphically defined base of the Triassic. The confidence interval (95%) for the mass extinction is 30 cm thick. As predicted by the ‘Signor–Lipps effect’, brachiopod last occurrences underestimate the time of extinction, as their abundance is below 15%. Therefore, also in North Iran located at equatorial palaeolatitudes along the southern shore of the Palaeotethys Ocean, the pattern of the latest Permian mass extinction is abrupt as observed in South China, in peri-Gondwana and in the Southern Alps. One of the most plausible mechanisms of the latest Permian sudden mass extinction could have been the emissions of tholeiitic magmas (Siberian Traps), which could have caused greenhouse gases emission into the atmosphere and thus global warming and ozone depletion, triggering the crisis (Svensen et al. 2008). Copyright © 2010 John Wiley & Sons, Ltd.

Maurizio Gaetani

Papers

The anisian (middle triassic) carbonate bank of Camorelli (Lombardy, Southern Alps)

Palynological dating (Arenig) of the sedimentary sequence overlying the Ishkarwaz Granite (upper Yarkhun valley, Chitral, Pakistan)

Permian stratigraphy and fusulinids from rosh gol (chitral, e hindu kush)

Towards a better definition of the Middle Triassic magnetostratigraphy and biostratigraphy in the Tethyan realm

The latest Permian mass extinction in the Alborz Mountains (North Iran)