After several surveys in the Western-Central sector of the North Karakoram terrane, the complex stratigraphic pattern of the Carboniferous successions begins to be unravelled. Based on the general structural and geologic reconstruction by Zanchi et al. (2001, this volume), several tectonic units have been identified, each with a peculiar stratigraphic setting. The Carboniferous successions crop out north of the Reshun Fault. To the south of this major lineament, the Carboniferous rocks have been eroded before the Reshun Conglomerate deposition or were not identified up to now. Carboniferous rocks have been recognised in at least six different tectonic units (Siru Gol Unit, Lasht Unit, Baroghil Unit, Chillinji Unit, Buattar Unit, and Karambar Unit). In the former five units the Carboniferous sediments comprise 50-180 m of greyish-blue marly slates overlaid by crinoidal limestones with poorly diagnostic fossil assemblages, whereas in the Karambar Unit a thicker and complex succession - already identified in 1996 (Angiolini et al., 1999) - has been mapped and measured in the 1999 expedition. In fact, in the Karambar Unit a more complete Paleozoic succession spanning in time from Devonian to Late Permian crops out around the Karambar Pass between the Chantar Glacier and the Afghan border. Here several sections have been measured from the Karambar Pass to the West showing sharp and conspicuous variation in lithology and thickness of the Carboniferous successions. Four main lithofacies have been identified in the Karambar Unit, bottom to top: (1) well bedded marly limestones with crinoids, corals brachiopods, and corals, interfingering with (2) massive encrinites, (3) yellowish clinostratified sandstones with hybrid limestones, locally overlaid upward by (4) massive limestones. Based on quantitative biostratigraphy of the brachiopods assemblages, three biozones have been detected, spanning the Early to Middle Carboniferous: - Biozone 1, comprising Gypospirifer sp., Anthracospirifer sp., Afghanospirifer sp., Brachythyris sp., Syringothyris sp., Dyctioclostinae gen. indet., Sajakella sp., Marginoproductus sp., Buxtonioides sp., Serpukhovian in age; - Biozone 2, comprising Choristites sp., Gypospirifer sp., Afghanospirifer sp., Spiriferinae gen. indet., Anthracospirifer sp., Brachythyris sp., Syringothyris sp., Dyctioclostinae gen. indet., Buxtonioides sp., Rhipidomella sp., Serpukhovian-Bashkirian in age; -Biozone 3, Syringothyris sp., Dowhatania sp., Dyctioclostinae gen. indet. Buxtonioides sp., Septacamera sp., Alispirifer sp., Densepustula sp., Bashkirian-Moscovian in age. Biozone 1 occurs in lithozone 1, whereas Biozone 2 and 3 have been correlated through lithozone 3. The Carboniferous successions are covered by shales and quartzitic sandstones of the Gircha Fm., bearing Asselian (Early Permian) brachiopod assemblages. In the Baroghil Unit, the Gircha quartzarenites overlie with a gentle angular unconformity the crinoidal limestones. Severe facies lateral variations suggest sedimentation in a strongly active syn-rift tectonic context, which may be linked to the beginning of rifting of the Karakoram block from Gondwana.

Angiolini, L., Gaetani, M., Olivini, G., Zanchi, A. (2001). Geology and stratigraphy of the carboniferous of Western-Central Karakoram. Intervento presentato a: XVI Himalayan, Karakorum, Tibet Workshop, Graz.

Geology and stratigraphy of the carboniferous of Western-Central Karakoram

ZANCHI, ANDREA MARCO
Ultimo
2001

Abstract

After several surveys in the Western-Central sector of the North Karakoram terrane, the complex stratigraphic pattern of the Carboniferous successions begins to be unravelled. Based on the general structural and geologic reconstruction by Zanchi et al. (2001, this volume), several tectonic units have been identified, each with a peculiar stratigraphic setting. The Carboniferous successions crop out north of the Reshun Fault. To the south of this major lineament, the Carboniferous rocks have been eroded before the Reshun Conglomerate deposition or were not identified up to now. Carboniferous rocks have been recognised in at least six different tectonic units (Siru Gol Unit, Lasht Unit, Baroghil Unit, Chillinji Unit, Buattar Unit, and Karambar Unit). In the former five units the Carboniferous sediments comprise 50-180 m of greyish-blue marly slates overlaid by crinoidal limestones with poorly diagnostic fossil assemblages, whereas in the Karambar Unit a thicker and complex succession - already identified in 1996 (Angiolini et al., 1999) - has been mapped and measured in the 1999 expedition. In fact, in the Karambar Unit a more complete Paleozoic succession spanning in time from Devonian to Late Permian crops out around the Karambar Pass between the Chantar Glacier and the Afghan border. Here several sections have been measured from the Karambar Pass to the West showing sharp and conspicuous variation in lithology and thickness of the Carboniferous successions. Four main lithofacies have been identified in the Karambar Unit, bottom to top: (1) well bedded marly limestones with crinoids, corals brachiopods, and corals, interfingering with (2) massive encrinites, (3) yellowish clinostratified sandstones with hybrid limestones, locally overlaid upward by (4) massive limestones. Based on quantitative biostratigraphy of the brachiopods assemblages, three biozones have been detected, spanning the Early to Middle Carboniferous: - Biozone 1, comprising Gypospirifer sp., Anthracospirifer sp., Afghanospirifer sp., Brachythyris sp., Syringothyris sp., Dyctioclostinae gen. indet., Sajakella sp., Marginoproductus sp., Buxtonioides sp., Serpukhovian in age; - Biozone 2, comprising Choristites sp., Gypospirifer sp., Afghanospirifer sp., Spiriferinae gen. indet., Anthracospirifer sp., Brachythyris sp., Syringothyris sp., Dyctioclostinae gen. indet., Buxtonioides sp., Rhipidomella sp., Serpukhovian-Bashkirian in age; -Biozone 3, Syringothyris sp., Dowhatania sp., Dyctioclostinae gen. indet. Buxtonioides sp., Septacamera sp., Alispirifer sp., Densepustula sp., Bashkirian-Moscovian in age. Biozone 1 occurs in lithozone 1, whereas Biozone 2 and 3 have been correlated through lithozone 3. The Carboniferous successions are covered by shales and quartzitic sandstones of the Gircha Fm., bearing Asselian (Early Permian) brachiopod assemblages. In the Baroghil Unit, the Gircha quartzarenites overlie with a gentle angular unconformity the crinoidal limestones. Severe facies lateral variations suggest sedimentation in a strongly active syn-rift tectonic context, which may be linked to the beginning of rifting of the Karakoram block from Gondwana.
No
abstract + slide
Earth-Surface Processes; Geology
English
XVI Himalayan, Karakorum, Tibet Workshop
Angiolini, L., Gaetani, M., Olivini, G., Zanchi, A. (2001). Geology and stratigraphy of the carboniferous of Western-Central Karakoram. Intervento presentato a: XVI Himalayan, Karakorum, Tibet Workshop, Graz.
Angiolini, L; Gaetani, M; Olivini, G; Zanchi, A
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/130251
Citazioni
  • Scopus 1
  • ???jsp.display-item.citation.isi??? ND
Social impact