Himalayan Geology, Vol. 41 (2), 2020, pp. 121-132, Printed in India
Paleo-depositional and sequence stratigraphic setting of the middle Jurassic Samana Suk Formation at Tarnawai Section, lesser Himalayas and its regional comparison
ABDUS SABOOR1,2, NASAR KHAN2,3*, MUHAMMAD HANIF4, IRFAN U. JAN4, SHAKEEL AHMAD2, WAQAR AHMAD5,6
1School of Earth Sciences and Resources, China University of Geosciences, Beijing, 100083, China
2Department of Geology, University of Peshawar, Peshawar, Pakistan
3Department of Geology, University of Malakand, Chakdara, 18800, Pakistan
4National Centre of Excellence in Geology, University of Peshawar, Peshawar, Pakistan
5Department of Geology, University of Swabi, Swabi, Pakistan
6Department of Earth and Atmospheric Sciences, University of Alberta, Alberta, Canada
*Email (Corresponding author): nasar_khan@uom.edu.pk
Abstract: The middle Jurassic sedimentary strata of Indus Basin shows relatively uniform lithology consisting predominantly of eastern Tethys carbonates. These fine to coarse grained carbonates (Samana Suk Formation) exposed in lesser Himalayas have been analyzed for its paleo-depositional settings and sequence stratigraphic framework. The sedimentary processes at the site led to generation of abundant peloids, ooids, intraclasts and mixed with skeletal allochems of bivalves, gastropods, echinoderms, brachiopods, ostracods and radiolarians. The resultant carbonate rock types have been grouped into six recurring microfacies of (i) planktonic lime mudstones; (ii) bioclastic-siliciclastic lime mudstones; (iii) peloidal-bioclastic wackestones; (iv) peloidal packstones; (v) peloidal-bioclastic-ooidal grainstones; and (vi) peloidal grainstones. The spatial distribution of the microfacies associations reflect a shift in paleoenvironments from platform interiors to outer platform settings. The platform is envisaged to have been covered by widespread peloidal sand flats and low relief banks. Changes in depositional patterns have been linked to sea level changes and revealed that sedimentation occurred as transgressive-regressive cycles during the Bathonian-Callovian. The section records three maximum flooding surfaces; one each in the lower, middle and upper portion, corresponding to eustatic sea level changes. Transgressive-regressive events have been put in a regional context and extended by correlation with other Gondwana sections like Jaisalmer and Kachchh basins of western India, Morondava Basin of Madagascar, Malivundo and Magindu formations of Tanzania, and Baidoa and Anóóle formations of southwestern Somalia. Regional comparison advocates extensive development of protected marine environments and associated grainstone bars with signals of eustatic sea level highs in semi-arid to humid climates.
Keywords: Samana Suk Formation, Tarnawai, Indian Plate, Tethys, Lesser Himalayas, Middle Jurassic.
