Early Cretaceous volcaniclastic and quartzose sandstones from north central Nepal: composition,sedimentology and geotectonic significance |
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| Authors: | Sören B Dürr Martin R Gibling |
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| Institution: | (1) Geologisch-Paläontologisches Institut, Sigwartstrasse I0, D-72076 Tübingen, Germany;(2) Department of Earth Sciences, Dalhousie University, B3H 3J5 Halifax, Nova Scotia, Canada;(3) Present address: Mineralogisches Institut, Am Hubland D-97074, Würzburg, Germany |
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| Abstract: | Early Cretaceous sandstones and shales from the Thakkhola region (Chukh and Tangbe Formations) were deposited on the subsiding northern (Tethyan) margin of Gondwana; current directions indicate a source area to the south. Whereas the Berriasian Chukh Formation is dominated by quartz arenites, volcaniclastic sandstones and minor conglomerates dominate the Tangbe Formation of Valanginian to Aptian age. Upsection, the composition of the volcaniclastic components changes from mainly basaltic to dominantly dacitic/rhyolitic. Magmatism was preceded and accompanied by strong uplift in the source area of the Chukh and Tangbe clastics, resulting in the erosion of probably more than several hundred meters of pre-Cretaceous sedimentary, metamorphic and plutonic rocks. A geochemical whole rock analysis of basaltic pebble fragments shows their alkaline character and suggests a  within-plate geotectonic setting for the volcanic source. This volcanotectonic event is probably related to rifting between Australia and Greater India, where seafloor spreading began in late Valanginian/Hauterivian times. |
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| Keywords: | North central Nepal Geotectonics Volcaniclastic sandstones Quartzose sandstones |
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