Melanges: Their Nature, Origin, and Significance

Composition and origin of the Kanar Melange, southern Pakistan Available to Purchase
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Published:January 01, 1984
The Kanar Melange is an ophiolitic melange underlain by Cretaceous shelf-slope argillites and overlain by a thrust sheet of Cretaceous ophiolites. The melange consists of a chaotic mixture of millimeter to kilometer-size clasts embedded in a dominantly argillaceous matrix. The affinities of the clasts are continental (e.g., Mesozoic shelf carbonate rocks, clastic and sedimentary rocks, mafic-ultramafic and alkali-volcanic rock bearing conglomerates) and oceanic (serpentinite, gabbro, and basalt). The matrix is mildly deformed to strongly folded and foliated. The melange was emplaced during the Paleocene in a trough located on the western margin of the Indo-Pakistan subcontinent.
A two stage model for the origin of melange is proposed. It involves Paleocene oblique convergence between the western margin of the Indian Plate and the adjoining Neo-Tethys along a Cretaceous transform boundary. This resulted in the formation of a zone of tectonically mixed continental and oceanic rocks (proto-Kanar Melange) bounded by a trough (tectonic foredeep) on the continental margin. Debris from the mixed zone was shed into the trough, leading to the formation of the Kanar Melange. Tectonic mixing of contrasting rock types is considered an important step in the genesis of the Kanar Melange. However, the presence of sedimentary features in the matrix of the melange and its depositional relationship with the underlying Sembar Formation suggest that the emplacement of the melange may have been controlled by sedimentary processes. Oblique convergence culminated in the obduction of ophiolite nappes above the melange and regional-scale folding of the whole area. These events produced a tectonic overprint that obscured primary stratigraphic and structural relationships within the melange belt.
- Aptian
- Asia
- Cenozoic
- composition
- Cretaceous
- debris flows
- deformation
- folds
- foliation
- genesis
- Indian Peninsula
- Indian Plate
- Lower Cretaceous
- Maestrichtian
- mass movements
- melange
- Mesozoic
- Neotethys
- ophiolite
- Pakistan
- Paleocene
- Paleogene
- sedimentary structures
- Senonian
- structural analysis
- structural geology
- tectonics
- Tertiary
- Upper Cretaceous
- Shirinab Formation
- Sembar Formation
- southern Pakistan
- Kanar Melange
- Bela Ophiolite Belt
- Ornach-Nal-Chaman Fault System
- Kirthar-Sulaiman Mountains