Journal of the Palaeontological Society of India ISSN 0522-9630 Volume 58(1), June 2013: 75-86 UPPER SIWALIK MAMMALIAN FAUNAS OF THE IILVIALAYAN FOOTHILLS A. C. NANDA WADIA INSTITUTE OF HIMALAYAN GEOLOGY, DEBRA DUN 248 001 E-mail: nandaac@rediffmail.com ABSTRACT The Tatrot and Pinjor faunas belonging to the Upper Siwalik Subgroup are well known from Pakistan, India and Nepal. The faunas along with proposed biostratigraphic interval-zones/range-zones/faunal-zones for the Upper Siwalik Subgroup of Potwar Plateau, Mangla-Samwal area and Pabbi Hills (all in Pakistan), Chandigarh-Jammu regions (India), and Surai Khola, Rato Khola and Kathmandu Valley (all in Nepal) are discussed. Despite the presence of a two-million year unconformity at the base of the Tatrot Formation, the type locality has yielded rich Tatrot Fauna. The Mangla-Samwal, Chandigarh-Jammu, Surai Khola and Rato Khola areas have yielded both Tatrot and Pinjor faunas, whereas Pabbi Hills and Lokhundol Formation of the Kathmandu Valley have yielded Pinjor Fauna. The Pinjor Fauna is well developed in the type locality of Chandigarh as compared to other localities in Pakistan, India and Nepal. In the last five decades, 54 characteristic taxa for the Pinjor Fauna are recorded from the Chandigarh region. In Pakistan, abundant magnetostratigraphic data are available and workers clubbed mammalian taxa and proposed biostratigraphic zones for the Middle and Upper Siwalik subgroups. However, the rich Tatrot and Pinjor faunas are known from the Chandigarh and Jammu regions, but magnetostratigraphic data are scanty. Two biostratigraphic interval-zones, Elephas planzfrons Interval-Zone (3.6-2.6Ma) and Equus sivalensis Interval-Zone (2.6-0.6 Ma), are recognized for the Indian Upper Siwalik. In Nepal, scanty Tatrot and Pinjor faunas are developed and the associated magnetostratigraphic dates do not tally with the recovered characteristic mammalian taxa. Thus, it is not possible to recognize the interval-zones in Nepal. Keywords: Upper Siwalik, Tatrot and Pinjor faunas, biostratigraphic zones, Himalayan foothills INTRODUCTION Southernmost foothills of the Himalaya are the youngest mountain range involved in the folding of the last mountain building phase of the Himalaya. These foothills are characterized by freshwater deposits and are referred to as the 'Siwalik Group'. The Siwalik succession is about 7 km thick, ranges in age from 18.3 Ma (Johnson et al., 1985) to 0.22 Ma (Ranga Rao et al., 1988), and extends between Indus River in the west and Brahamputra River in the east. The Siwalik Group is known for its very rich vertebrate, particularly mammalian, assemblage of fossils. It is divided into three subgroups, Lower, Middle and Upper. The subgroups are further divided into formations: Kamlial and Chinji (Lower Siwalik), Nagri and Dhok Pathan (Middle Siwalik), and Tatrot, Pinjor and Boulder Conglomerate (Upper Siwalik). The Siwalik Group is not uniformly fossiliferous and the fossils are confined to pockets. The Upper Siwalik fossils are known from Potwar Plateau, Pabbi Hills and Mangla- Samwal (all in Pakistan), Chandigarh and Jammu regions of India, and Irrawaddy Valley, Myanmar. The Upper Siwalik faunas of all the regions, except that of Irrawaddy valley, are discussed. In Myanmar, this freshwater succession is called Irrawaddy Group. The Tatrot and Pinjor formations of the Upper Siwalik are richly fossiliferous. The Boulder Conglomerate Formation, the youngest formation of the Siwalik Group, is devoid of fossils. The Tatrot and Pinj or formations are sandstone- mudstone units, whereas Boulder Conglomerate Formation is essentially a conglomeratic deposit. The Lower and Middle Siwalik subgroups are very rich in vertebrate fossils. Pilgrim (1913-1934) based the type localities of the various formations of the Lower and Middle Siwalik and Tatrot Formation of the Upper Siwalik in Potwar Plateau. However, he based the type area of the Pinjor Formation near Chandigarh, which lies about 400 km southeast of the type locality of the Tatrot Formation. Pilgrim (1932, 1938) was aware of the presence of Tatrot fossils from the type area of the Pinjor Formation, but exact location was not known to him Now, rich Tatrot Fauna is known from the Siwalik Hills and will be discussed later. The biostratigraphy of the Upper Siwalik, based on mammalian fossils, is discussed in brief. A location map depicting significant fossil localities of the Siwalik Group is provided ( Fig. 1). Upper Siwalik faunas of Pakistan Three prominent fossiliferous areas of Pakistan are Hasnot- Kotal Kund — Tatrot-Andar Kas, Mangla-Samwal and Pabbi Hills. Tatrot area, Potwar Plateau The Upper Siwalik sediments are exposed in the upper part of the Tatrot-Andar Kas and Kotal Kund sections. The American workers, including Barry et al. (1982), called these sections as Hasnot Composite Section. The Kotal Kund section lies 10 km south of Hasnot village. The Tatrot-Andar Kas section of Barry et al. (1982) combines two partial sections. The upper part of the section is exposed 4 km north of Hasnot and lower part at Andar Kas about 4 km east of Hasnot. Combined magnetostratigraphic and palaeontologic studies were carried out by Barry et al. (1982). According to these workers (p. 107), "The Tatrot part of the section has an unconformity below the uppermost 60 metres which, on the basis of magnetic polarity stratigraphy and faunal evidence, may represent of hiatus of more than 2 m.y." This missing part of the Tatrot-Andar Kas succession is marked in the Kotal Kund section. Colbert (1935) and Pilgrim (1939) in their respective faunal list mentioned several taxa from the Tatrot Formation. At that time, Tatrot Fauna was only known from the Potwar Plateau. The reported taxa include Anancus (= Pentalophodon) falconeri, Ste godon bombifrons, Sivachoerus giganteus,. Propotamochoerus hysudricus (= Dicoryphochoerus vagus), Hippopotamodon sivalense (= D. titanoides), Hippohyus sivalensis (= H. grandis),