Geological evolution of the tethys belt from the atlantic to the pamirs since the LIAS

Seismic tomography models of the three-dimensional upper mantle velocity structure of the Mediterranean-Carpathian region provide a better understanding of the lithospheric processes governing its geodynamical evolution. Slab detachment, in particular lateral migration of this process along the plate boundary, is a key element in the lithospheric dynamics of the region during the last 20 to 30 million years. It strongly affects arc and trench migration, and causes along-strike variations in vertical motions, stress fields, and magmatism. In a terminal-stage subduction zone, involving collision and suturing, slab detachment is the natural last stage in the gravitational settling of subducted lithosphere.

http://www.mantleplumes.org/WebDocuments/Wortel2000.pdf

Subduction and Slab Detachment in the Mediterranean-Carpathian Region

Tectonics of the zagros orogenic belt of iran - new data and interpretations

Geology of the USSR : a plate-tectonic synthesis

The motion of the Indian plate is determined in an absolute frame of reference and compared with the position of the southern margin of Eurasia deduced from palaeomagnetic data in Tibet. The 2,600±900 km of continental crust shortening observed is shown to have occurred in three different episodes: subduction of continental crust, intracontinental thrusting and internal deformation, and lateral extrusion. The detailed chronology of the collision and plate reorganizations in the Indian and Pacific oceans supports the hypothesis that slab-pull is a dominant driving mechanism of plate tectonics.

India–Eurasia collision chronology has implications for crustal shortening and driving mechanism of plates

Presentation de 9 cartes paleogeographiques au 1/20000000000eme s'etendant de l'Atlantique au Pamir pour la periode du Lias a l'Actuel

Paleomagnetic implications on the evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic

The latitude of the Lhasa block (Xizang, South Tibet) during the late Cretaceous–early Tertiary is of prime importance for understanding the collision of India and Eurasia and the mechanism of the formation of the Qinghai–Xizang plateau. During the first field expedition of the French–Chinese collaboration, several geological formations have been sampled in southern Tibet between Lhasa (29.40° N; 91.09° E) and Dingri (28.35° N; 86.38° E). We present here the first results obtained for middle Cretaceous to Palaeocene red beds from the Lhasa block, north of the Yarlung–Zang Bo suture zone, recognized as the main suture between the Indian and the Eurasian plates. They indicate a palaeolatitude of the Lhasa block of 20° N during the late Cretaceous while India was situated 30° S.

Position of the Lhasa block, South Tibet, during the late Cretaceous

Summary. A palaeomagnetic study of Middle to late Cretaceous redbeds from Linzhou basin (Lhasa block), north of the Yarlung Zangbo suture zone, gives a stable palaeomagnetic direction of magnetization with a positive fold-test: six sites, 57 samples, D= 333°, I= 38°, k= 78, α95= 8°, pole 64°N, 348°E. We discuss the problem of a possible remagnetization but consider that this direction of magnetization gives a good approximation for the palaeolatitude of the Lhasa block during Middle to late Cretaceous time. Results from more recent Tibetan formations are also presented: late Cretaceous to Palaeocene sediments and volcanics give a lower palaeolatitude of 10° N and but more recent andesites have emplaced about 30°N, close to the present-day latitude. An interpretation is proposed whereby the Lhasa block, which was a part of Asia in the early Cretaceous, has undergone first a southward motion accompanied by an anticlockwise rotation and then, after the Palaeocene, a northward motion under the constraint of the colliding India.

/pdf/palaeomagnetic-data-about-southern-tibet-xizang-i-the-1u8yvawz5i.pdf

M. Westphal

Papers

Geological evolution of the tethys belt from the atlantic to the pamirs since the LIAS

Presentation de 9 cartes paleogeographiques au 1/20000000000eme s'etendant de l'Atlantique au Pamir pour la periode du Lias a l'Actuel

Paleomagnetic implications on the evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic

Position of the Lhasa block, South Tibet, during the late Cretaceous

Palaeomagnetic data about southern Tibet (Xizang) — I. The Cretaceous formations of the Lhasa block