Study of fossil wood from the upper Tertiary sediments (Siwalik) of Arunachal Pradesh, India and its implication in palaeoecological and phytogeographical interpretations

Magnetostratigraphy of the Neogene Siwalik Group in the far eastern Himalaya: Kameng section, Arunachal Pradesh, India

“…ChRM has been acquired before compaction, probably during early diagenetic processes, similar to other Siwalik magnetostratigraphic records (Tauxe and Kent, 1984;Appel et al, 1991;Gautam and Appel, 1994;Gautam and Rösler, 1999;Gautam and Fujiwara, 2000;Ojha et al, 2000Ojha et al, , 2009. We speculate that this early diagenetic formation and preservation of primary iron sulfides, which is not observed in other Siwalik records, is related to the more brackish environment described in the Siwaliks of the far eastern Himalayas of Arunachal Pradesh (Singh and Prakash, 1980;Singh and Tripathi, 1990;Mehrotra et al, 1999), similar to iron sulfide magnetization previously observed in such brackish depositional environments (Jelinowska et al, 1998;Vasiliev et al, 2004Vasiliev et al, , 2008. Joshi et al (2003) reported typical coastal plant megafossils and cuticular fragments in the upper part of the Kameng section, probably implying that the brackish influence remained even though this part of the section is constituted of coarse sandstone and conglomerate.…”

“…The transition from deltaic to fluvial environments is estimated to have occurred between the Middle and the Late Miocene (Kent and Dasgupta, 2004). Nonetheless, in contrast to the wellknown continental fluvial origin of the Siwalik rocks of the western and central Himalaya, the Neogene environment in Arunachal Pradesh displays a strong influence of brackish water or a near coastal setting, as evidenced by paleobotanical studies (Singh and Prakash, 1980;Singh and Tripathi, 1990;Mehrotra et al, 1999). Some workers have suggested that the Siwalik foreland basin of Arunachal Pradesh was not connected to the Siwalik basin of the western Himalaya (Rao, 1983;Sinha et al, 1982).…”

New lauraceous species from the Siwalik forest of Arunachal Pradesh, eastern Himalaya, and their palaeoclimatic and palaeogeographic implications

“…The modern analogues of fossil specimens described above form a natural association in the evergreen forests of India and South-East Asia and suggest that during Siwalik sedimentation forests developed under a tropical, warm, humid climate. This is consistent with the earlier interpretations based on megaplant fossil data (Mehrotra et al, 1999;Bera et al, 2004;Joshi et al, 2003;Joshi and Mehrotra, 2007;Bera, 2007, 2010;Bera and Khan, 2009;Srivastava and Mehrotra, 2009;Khan et al, 2008Khan et al, , 2009Khan et al, , 2011. However, at present, a tropical semievergreen forest cover is found in the area of investigation (Hazra et al, 1996).…”

Study of fossil wood from the Middle–Late Miocene sediments of Dhemaji and Lakhimpur districts of Assam, India and its palaeoecological and palaeophytogeographical implications

“…Except the last one which was described from the Tertiary of Ethiopia, all other species are known from various Tertiary exposures of India (Mehrotra et al 1999). After detailed comparison with the above species, it has been found that our fossil is identical to G. burmense and accordingly, has been kept under the same.…”

“…C. parainaequifolium (Prakash 1979a) is known from the Tertiary of Thailand, while C. tertiarum (Awasthi and Mehrotra 1997) is described from the Neogene of Tirap District, Arunachal Pradesh. In addition, Mehrotra et al (1999) described Cynometroxylon sp. cf.…”