A Record of Rotaloid Foraminifera from the Upper Permian-Lower Triassic Rocks of Kashmir , India

The first record of Rotaloid foraminifera from the Upper Permian-Lower Triassic of Kashmir is significant as it provides an insight to understand organic evolution. The present study explicitly reveals that Rotaloid foraminifers’ first origination was in Upper Permian in Peri-Gondwana Tethys and later migrated to other provinces of the world.


INTRODUCTION
In the history of organic evolution, the end of Palaeozoic Era was marked by the conspicuous event of mass extinctions.Amongst foraminifera, as many as fourteen families became extinct (Loeblich and Tappan, 1964) during the Permian Period and many new families evolved in the Mesozoic.There is a gap in the record of foraminifera from latest Permian and earliest Triassic because of the absence of marine strata representing this time span due to global regression of epicontinental seas.The Permian-Triassic transition represents a critical period in foraminiferal evolutionary history as the end-Permian mass extinction with few survivals and recovery intervals resulted in a dramatic turnover in the taxonomic composition of calcareous benthic assemblages (Grooves and Altiner, 2005;Ma´rquez, 2005).(Nakazawa et al., 1975).At three kilometers north of Barus the Upper Permian strata attain a thickness of 125 meters (Nakazawa et al., 1975).The succession becomes increasingly calcareous in up-section and the succeeding Lower Triassic Khunamuh Formation consists of alternations of grey to black limestone intercalated with black shale layers.In the present paper we adopt the lithostratigraphic framework proposed by Nakazawa et al. (1975) subdividing the Zewan Formation into four (A-D) and the Khunamuh Formation into six (E-J) lithounits.Figure 2 summarizes the litho-and biostratigraphy of the Zewan Formation and lowermost part of the Khunamuh Formation.

MATERIAL AND METHODS
The study is based on the presence of foraminiferal assemblage reported by the authors in their present and earlier work (Kalia andSharma, 1985, Pande, 1989;Pande and Kalia, 1994)  Upper Permian and the Lower Triassic horizons of these two successions of Kashmir.The successions are stratigraphically well constrained by earlier palaeontological and sedimentological studies (Nakazawa et al., 1975;Sweet, 1970;Teichert et al., 1970;Furnish et al., 1973;Kalia and Pande,1989;Pande and Kalia, 1994;Korte et al., 2010) (Okimura and Ishii, 1981;Kalia and Sharma, 1985).Other characteristic Permian fauna reported by previous workers from the Zewan Formation (Nakazawa et al., 1975;Nakazawa and Kapoor, 1981)

Foraminiferal Record
Late Palaeozoic calcareous foraminiferal assemblages were dominated by the Order Fusulinida, including a variety of large and internally complex forms.Early Mesozoic assemblages, in It was thought that Permian lenticulines perhaps possessed a different wall structure and do not represent Lenticulina s str.(Brotzen, 1963).The species of Lenticulina occur vertically

Late
Palaeozoic and early Mesozoic sequences are reasonably well known for the record of calcareous foraminifers.This is limited to occurrences in the Upper Permian Wuchiapingian and Changhsingian stages through the Lower Triassic Induan and Olenekian stages and demonstrates changes in generic diversity within the orders Fusulinida, Miliolida, Lagenida and Involutinida (Grooves and Altiner, 2005).In Kashmir, uppermost Permian [Araksian (Dzhulfian)] and lowermost Triassic [Brahmanian (Induan)] shallow marine sediments are continuously well exposed at two localities in Vihi District, Srinagar, namely, Guryul ravine and a spur three kilometers north of Barus.The study of the Upper Permian foraminiferal assemblage from these sediments has shown the presence of rotaloid genera belonging to three families namely, Lenticulina Lamarck, Marginulina D'Orbigny, Vaginulinopsis Silvestri, Citharina D'Orbigny (Nodosariidae), Pyrulinoides Marie (Polymorphinidae) and Diplotremina Kristan-Tollman, Duostomina Kristan-Tollman (Discorbidae) in association with typical Permian forms.The presence of these genera in Zewan Formation extends their lower age limit to Upper Permian and suggests that Tethys remained the centre of origin and development for foraminifera well up to the close of the Permian.
throughout the Zewan Formation and are characterized by a slightly trochospiral coil with a tendency to uncoil or having uncoiled later portion, radiate aperture and calcareous, radial, finely perforate wall(Figs 3.8 to 3.13 and Figs 4.2 to 4.7, 4.9, 4.11).Although the specimens recovered from the Upper Permian of Kashmir are recrystallized to various degree, the wall structure has not been completely obliterated.The radial wall structure is quite clear in the thin sections of Lenticulina spp.shown in figures 3.18, and 3.19, although, in some of the segments recrystallization has caused slight thickening of fibers.Pande and Kalia (1994) described several genera of the family Vaginulinidae (Lenticulina, Marginulinopsis, Saracenaria, Astacolus, Marginulina and Vaginulinopsis) in thin-sections as well.Besides Lenticulina Lamarck other post-Palaeozoic nodosariid genera recorded from the Upper Permian of Kashmir include, Marginulina D'Orbigny, Vaginulinopsis Silvestri and Citharina D'Orbigny.The genera Vaginulinopsis and Citharina were known earlier only from Jurassic onwards.Vaginulinopsis spp. is recorded throughout the Zewan Formation (Fig 2) and Citharina is recorded from unit A3 and Member D at three kilometers north of Barus (Fig 2).
from the © CNCS, Mekelle University194 ISSN: 2220-184X . Specimens described here are deposited in Department of Geology, Ram Lal Anand College (University of Delhi).Specimens are numbered with code KSF and GR which stands for Kashmir Smaller Foraminifera and Guryul Ravine respectively.The foraminiferal assemblage obtained from closely sampled levels of the Zewan Formation in these two sections are characterized by the presence of typical Permian calc-microgranular forms, arenaceous forms and calcareous, perforate genera earlier recorded from Triassic or The present record of post-Palaeozoic genera from Zewan Formation namely Lenticulina Lamarck 1804, Marginulina D'Orbigny 1826, Vaginulinopsis Silvestri 1904, Citharina D'Orbigny 1839, Pyrulinoides Marie 1941, Diplotremina Kristan-Tollman 1960, Duostomina Kristan-Tollman 1960, in association with typical Permian foraminifera like Globivalvulina cyprica Reichel 1946, Lunucammina postcarbonica (Spandel) 1901, Lunucammina ovate (Lange) 1925, Nodosinella digitata Brady 1876, Tetrataxis conica Ehrenberg 1854, Glomospira simplex Harlton 1928, Ammobaculites texturata Cushman and Waters 1928, and Hemigordius calcarea Cushman and Waters 1928, brings down their lower age limit to the Upper Permian , are characterized mostly by morphologically simple miliolids and lagenids.Planktonic forms originated in Jurassic time, and Rotaloid, the dominant group of extant calcareous benthonic foraminifers, underwent their initial major expansion in Late Cretaceous time.The calcareous, perforate, radiate walled forms became prolific in Mesozoic in contrast to Palaeozoic foraminiferal assemblages characterized by calc-microgranular forms.The record of calcareous perforate forms from Permian was restricted to a few genera like, Nodosaria Lamarck 1812, Astacolus De Montfort 1808, and Frondicularia Defrance in D'Orbigny 1826, belonging to the family Nodosariidae.The earlier record of genus Lenticulina Lamarck was from Triassic onwards only.There have been but only two reports of the occurrence of lenticulines from Permian.Lenticulina (Astacolus) © CNCS, Mekelle University 195 ISSN: 2220-184X contrastoblonga Maklay 1960 (Maklay, 1964) was described from the Upper Permian of Russia and Lenticulina (Astacolus) initialis Crespin 1958 (Crespin, 1958) from NW Australia.Taxonomic position of Lenticulina (Astacolus) oblonga is questionable as it lacks a radiate aperture.The wall structure of Lenticulina (Astacolus) initialis Crespin was not commented upon sufficiently.