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The Structure of the 1985 Tibet Geotraverse, Lhasa to Golmud
Ist Teil von
Philosophical transactions of the Royal Society of London. Series A: Mathematical and physical sciences, 1988-12, Vol.327 (1594), p.307-333
Ort / Verlag
London: The Royal Society
Erscheinungsjahr
1988
Link zum Volltext
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
The structures of Tibet were generated during the accretion on to the Asian plate, firstly of the Qiangtang Terrane during
the Triassic, then the Lhasa Terrane during the Jurassic--Cretaceous and finally the Indian continent during the Palaeogene.
The southern Kunlun mountains show intense deformation associated with the accretion of deep water sediments on to an active
plate margin. The deformation was essentially by footwall propagation of thrusts, though there was pronounced out-of-sequence
thrusting with the deformation of basins above the main thrust zone, and the back steepening and backthrusting of earlier
structures. The Jinsha Suture probably represents the southern edge of this zone. The Banggong Suture between the Qiangtang
and Lhasa Terranes is characterized by pre-collisional ophiolite obduction for over 100 km to the south across the Lhasa Terrane,
plus local intense intracratonic deformation of parts of the Lhasa Terrane. However, for this collision there is now very
little evidence for intense deformation along the line of the suture and the Qiangtang Terrane itself remained only weakly
deformed throughout. Post--Middle Cretaceous, pre-Tertiary deformation of the Lhasa region produced upright- to north-verging
folds which decrease in intensity northwards. They may have been formed at the margin of the Gangdise batholith, or they may
have originated from early collisional phases along the line of the Indus--Zangbo Suture. However this deformation is approximately
synchronous with the more intense deformation of the Xigatse flysch on the accretionary prism and is therefore probably subduction-related,
predating collision. Tertiary deformation is relatively widespread across Tibet, producing SSE-directed thrusts across the
Fenghuo Shan region of the Qiangtang Terrane and across the northern part of the Lhasa Terrane. Several hundred kilometres
shortening can be estimated to have occurred during this deformation, probably reworking older Mesozoic structures. However
this shortening is insufficient to provide all of that estimated from palaeomagnetic work or from a study of displacement
rates of the Indian plate, and much of the displacement of India into Asia during the Tertiary must be taken up on strike-slip
faults in Tibet or on thrusts and strike-slip faults in central Asia north of the Tibetan Plateau. The Tertiary shortening
cannot account for all the thickening of the Tibetan crust.