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siwalik plant megafossil diversity in the Eastern Himalayas: A review

Plant Diversity 2023年第3期45卷 243-264页

作者： Mahasin Ali Khan Sumana Mahato Robert A.Spicer Teresa E.V.Spicer Ashif Ali Taposhi Hazra Subir Bera Palaeobotany and Palynology Laboratory Department of BotanySidho-Kanho-Birsha UniversityRanchi RoadPurulia 723104India CAS Key Laboratory of Tropical Forest Ecology Xishuangbanna Tropical Botanical GardenChinese Academy of SciencesMengla 666303PR China School of Environment Earth and Ecosystem SciencesThe Open UniversityMilton KeynesMK76AAUK Centre of Advanced Study Department of BotanyUniversity of Calcutta35B.C.RoadKolkata 700019India

The Eastern Himalayas are renowned for their high plant diversity.To understand how this modern botanical richness formed,it is critical to investigate past plant biodiversity preserved as fossils throughout the eastern Himalayan siwalik succession(middle Miocene-early Pleistocene).Here,we present a summary of plant diversity records that document Neogene floristic and climate changes.We do this by compiling published records of megafossil plant remains,because these offer better spatial and temporal resolution than do palynological records.Analyses of the siwalik floral assemblages based on the distribution of the nearest living relative taxa suggest that a tropical wet evergreen forest was growing in a warm humid monsoonal climate at the deposition time.This qualitative interpretation is also corroborated by published CLAMP(Climate Leaf Analysis Multivariate Program) analyses.Here,we also reconstruct the climate by applying a new common proxy WorldClim2 calibration.This allows the detection of subtle climate differences between floral assemblages free of artefacts introduced by using different methodologies and climate calibrations.An analysis of the siwalik floras indicates that there was a gradual change in floral composition.The lower siwalik assemblages provide evidence of a predominance of evergreen elements.An increase in deciduous elements in the floral composition is noticed towards the close of the middle siwalik and the beginning of the upper siwalik formation.This change reflects a climatic difference between Miocene and Plio-Pleistocene times.This review helps us to understand under what paleoenvironmental conditions plant diversity occurred and evolved in the eastern Himalayas throughout the Cenozoic.

关键词： Megafossils siwalik MiocenePleistocene Palaeovegetation Palaeoenvironment Eastern Himalayas

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Occurrence of Persea Mill. from the siwalik Forest of Darjeeling, Eastern Himalaya： Paleoclimatic and Paleogeographic Implications

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Journal of Earth Science 2016年第5期27卷 883-890页

作者： Mahasin Ali Khan Subir Bera Centre of Advanced Study Department of BotanyUniversity of CalcuttaKolkata-700019India Department of Botany Sidho-Kanho-Birsha UniversityPurulia 723104India

Fossil leaf remains of two new species of Persea Mill., belonging to the family Lauraceae collected from the lower part of the siwalik sediments（Gish Clay Formation of Sevok Group, Middle Miocene） of Darjeeling foothills of eastern Himalaya, are described. The new species are Persea miogamblei sp. nov. and Persea neovillosa sp. nov.. On the basis of leaf architecture（size, shape and venation pattern） fossil leaves described in this article closely resemble modern leaves of Persea gamblei（King ex Hook. f.） Kosterm. and Persea villosa（Roxb.） Kosterm.. The geographic distribution of the fossils and their modern counterparts are discussed and on that basis tropical evergreen vegetation with a warm and humid climate at the time of deposition of the siwalik sediments is suggested in contrast to the present day tropical deciduous vegetation in this area. The present finding also suggests probable migration of these lauraceous taxa to Southeast Asia.

关键词： Persea fossil leaves Middle Miocene siwalik paleoelimate Darjeeling.

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Evidence of the oldest extant vascular plant(horsetails)from the Indian Cenozoic

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植物多样性:英文版 2023年第5期45卷 569-589页

作者： Sampa Kundu Taposhi Hazra Tapan Chakraborty Subir Bera Mahasin Ali Khan Palaeobotany and Palynology Laboratory Department of BotanySidho-Kanho-Birsha UniversityRanchi RoadPurulia 723104India Geological Studies Unit Indian Statistical Institute203B.T.RoadKolkata 700108West BengalIndia Centre of Advanced Study Department of BotanyUniversity of Calcutta35B.C.RoadKolkata 700019India

Equisetum(Equisetaceae)has long been a focus of attention for botanists and palaeontologists because,given its extensive and well-documented fossil record,it is considered the oldest extant vascular plant and a key element in understanding vascular plant evolution.However,to date,no authentic fossil evidence of Equisetum has been found from the Indian Cenozoic.Here,we describe a new fossil species,namely,E.siwalikum sp.nov.,recovered from the middle siwalik(Late Miocene)sediments of Himachal Pradesh,western Himalaya.We identified fossil specimens based on morphological and epidermal characters.In addition,X-Ray diffraction(XRD)analysis was used to determine the mineral composition of compressed stems of Equisetum.The close affinity of our recovered siwalik fossils to Equisetum is supported by the presence of both macromorphological and epidermal characters.Because Equisetum generally grows in wet conditions around water reservoirs,our findings indicate that the fossil locality was humid and surrounded by swamp and lowland regions during deposition.Ample fossil evidence indicates that this sphenopsid once existed in the western Himalaya during the siwalik period.However,at present Equisetum is confined to a particular area of our fossil locality,probably a consequence of severe environmental changes coupled with competition from opportunistic angiosperms.Our discovery of Equisetum fossils in appreciable numbers from the siwalik sediments of the Himachal Himalayas is unique and constitutes the first reliable recognition of Equisetum from the Indian Cenozoic.

关键词： Equisetum Fossil stem and leaf sheaths Late Miocene Paleoecology siwalik Western India

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THRUST PACKAGES OF 1.68 Ga INDIAN SUPRA-CRUSTAL ROCKS IN THE MIOCENE siwalik BELT,CENTRAL NEPAL HIMALAYAS

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地学前缘 2000年第S1期7卷 64-66页

作者： Harutaka Sakai\+1,Yutaka Takigami\+2,B.N.Upreti\+3,D.P.Adhikary\+3[WT5,5”BX](1.Department of Earth Science,Kyushu University,Ropponmatsu,Fukuoka,810\|8560 Japan 2.Kanto Gakuen University,Ohta\|shi,Gunma,373\|8515 Japan 3.Department of Geology,Tri\|Chan

The siwalik Belt is a frontal fold\|thrust belt of the Himalayas and composed of thick sequence of foreland basin sediments derived from the Himalayas during the last 15 to 17 million years.From this Miocene belt in the central Nepal,we discovered exotic thrust packages of the Middle Proterozoic rocks,which has been regarded as the siwalik Group or post\|collisional sediments correlatable with the Subathu or Murree Formation in India.The thrust belt,called the Bagmati Belt,is narrowly distributed in the siwalik Belt,22km to the north of the Main Frontal Thrust (MFT or HFF) that is an active fault and considered to be the deformation front of the Himalayan orogen.The Main Boundary Thrust (MBT) which separates the siwalik Belt from the Lesser Himalayan Belt runs 7km to the north of the thrust packages.Within the belt,tectonic slices of 400m to 1km in thickness are repeated three to five times due to thrusts,sandwiching a thin slice of the siwalik beds.The thrust package consists of the pre\|siwalik sedimetary rocks and sills of dolerite,and named as the Bagmati Group.The thickness is only about 800m due to tectonic repition by thrust,although the group has been considered to be a continuous sequence attaining 2200m in thickness.We divided the Bagmati Group into three formations,each of which shows an upward\|coarsening and thickening sequence of 200 to 350m in thickness.All sequence is composed of red\|brown orthoquartzite,pink quartzite,micaceous shale and thin sandstone interbed and rhythmite,mottled hematite and hematitic pisolite.We interpret that the Bagmati Group was deposited in shallow lacustrine and desert environments.

关键词： thrust package the Bagmati Group the siwalik Belt Central Nepal Himalaya

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New Fossil Reptile Records from the siwalik of North India

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Open Journal of Geology 2016年第8期6卷 673-691页

作者： A. C. Nanda H. H. Schleich B. S. Kotlia Wadia Institute of Himalayan Geology Dehradun India Fuhlrott Museum & Research Institute Wuppertal Germany Centre of Advanced Study in Geology Kumaun University Nainital India

From the siwalik Group of Haryana and Himachal Pradesh, new fossil reptile records are described. The siwalik fauna from Haryana and Himachal is recorded from the pre-Pinjor and Pinjor beds (Upper siwalik Subgroup: Pliocene—Lower Pleistocene). The reptile fauna includes Crocodylus aff. palustris, Gavialis cf. gangeticus, Rhamphosuchus crassidens, Batagur sp., Geoclemys hamiltoni and Hardella thurjii. The findings are significant as fossil reptiles from the siwalik Group are scanty as compared to the richer mammalian fauna.

关键词： Fossils Reptile Pinjor Formation siwalik Pliocene-Pleistocene North India

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Size Analysis of the Late Pliocene-Early Pleistocene Upper siwalik Sediments, Northwestern Himalaya, India

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International Journal of Geosciences 2013年第8期4卷 1120-1130页

作者： Mahavir Singh A. R. Chaudhri Department of Geology Kurukshetra University Kurukshetra India

Size analysis of the Late Pliocene-Early Pleistocene Upper siwalik sediments comprising the Pinjor Formation in the type area and adjoining regions reveals that the sediments are bimodal to polymodal in nature, medium to fine grained and are moderately sorted. The inclusive graphic standard deviation and moment standard deviation values suggest the deposition of sediments in shallow to moderately deep fluvial agitated water. The log probability plots reveal that saltation mode is the dominant mode of transportation of detritus. The sediments are continental in character and are derived from crystalline, metamorphic and sedimentary rocks of the Himalaya exposed to the North of the type area Pinjor.

关键词： Texture siwalik Pinjor Himalaya

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Palaeosol of the siwalik Group as a 15 Ma Record of Palaeoclimate

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地学前缘 2009年第S1期16卷 241-241页

作者： Ram Ratan Singh Centre of Advanced Study in Geology Panjab University

Palaeosols are one of the architectural elements of sedimentation in the siwalik Foreland Basin holding a record of long term climate changes for the past 18 Ma.Systematic study of palaeosols,and associated non-pedogenic materials,along with their parent rock is important for understanding pedogenic processes and environments,which in turn gives insight into the interrelation between climate,topography and ecosystem.The fossil soils have a special value as they remains in the place of their formation

关键词： palaeosol siwalik palaeoclimate

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Clay Minerals as Climate Change Indicators—A Case Study

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American Journal of Climate Change 2012年第4期1卷 231-239页

作者： A. R. Chaudhri Mahavir Singh Department of Geology Kurukshetra University Kurukshetra India

The clay mineralogy of the Late Pliocene-Early Pleistocene Pinjor Formation of the type area, northwestern Himalaya, India has been investigated to understand the paleoclimatic conditions and paleotectonic regime prevailing in the frontal Himalayan terrain during 2.5 Ma to 1.7 Ma. The clay minerals were investigated by X-ray diffraction analysis and scanning electron microscope studies. Study of the oriented aggregates of 47 representative clay samples of the Pinjor Formation of the type area reveals that illite is the most dominant mineral followed by chlorite, kaolinite, vermiculite and mixed layer clay minerals. The distribution of the clay minerals in the three lithostratigraphic units of the Formation, namely the Kona Clay Member, the Tanda Bhagwanpur Wacke Member and the Chauki Nadah Pebbly Bed Member which are well exposed along the Berwala-Mandhna section, the Kona-Karaundanwala section and the Ghaggar River-Chauki Nadah section, is nearly uniform suggesting thereby the prevalence of similar sedimentation environments in the Himalayan foreland basin. The presence of illite and kaolinite suggests their derivation from crystalline rocks containing felspar and mica as also from pre-existing soils and sedimentary rocks. Further, the paleoclimatic conditions were moderate. Presence of chlorite suggests the weathering of intermediate and basic crystalline rocks and low grade metamorphic rocks in the positive areas. The presence of kaolinite in the Pinjor Formation is mainly attributed to the weathering and subsequent leaching of the mineral from granitic and basic rocks in the hinterland. Vermiculite has been mainly formed by weathering and transformation of biotite. Warm and humid climatic conditions prevailed for a major part during the deposition of the detritus which favored weathering and transformation of minerals. During the terminal phase of sedimentation there was renewed tectonic activity which had a significant impact on climate as precipitation and mechanical weathering rates increased substantially

关键词： Clay Minerals Climate Pinjor siwalik Himalaya India

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