Siwalik plant megafossil diversity in the Eastern Himalayas: A review

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.

喜马拉雅前陆盆地中新世—上新世 SIWALIK-CHURIA群轮藻化石及其古生物地理和古生态意义(英文)

印度、尼泊尔晚中新世—上新世 SIWAL IK- CHU RIA群轮藻化石组合与中国塔里木盆地及哈萨克斯坦东南部伊犁盆地轮藻组合极为接近。据此讨论了它们的古生物地理和古生态学特征。中新世—上新世轮藻植物繁盛的原因与当时季风活动引起的季节性洪水泛滥 ,在广大河漫滩地上形成有利于轮藻植物生长发育的局部湖泊环境有关。

Assessment of Hydrocarbon Prospectivity in Terai and Siwaliks, Exploration Block 2, Western Nepal

BasinMod 1D software with faulting module is used to model two synthetic wells taken from a geoseismic section in Exploration Block 2 in western Nepal to understand the burial and thermal history of exterior belt （Terai） and Siwalik fold and thrust belt. The study focuses the measured inputs of source and reservoir rocks of Surkhet Group consisting of Swat shale （2%）, TOC and Melpani sandstone porosity （10%）. The geohistory curves show rapid sedimentation and tectonic subsidence. The thermal history is constrained using a 20 ℃/km geothermal gradient for the exterior belt, whereas for the Siwalik fold and thrust belt, a two-step geothermal gradient is proposed using a 20 ℃/km for the upper 2,000 m and 23 ℃/km below this depth. The modeled values for maturity show that the Surkhet Group lies in the mid mature oil window in the exterior belt, but for the Siwalik fold and thrust belt, the hanging-wall Paleogene wedge is in the early mature stage, whereas the footwall Paleogene wedge is in the late mature stage. Oil generation for the Swat shales started at 6.3 Ma at 3,988 m depth with peak oil generation 2.4-1.3 Ma at 5,435-5,782 m depth in the exterior belt. However, the Siwalik fold and thrust belt modeling shows that the footwall Swat Formation has no oil generation capacity after the faulting episode, whereas it had been producing oil since about 8.5 Ma at 3,800 m with main phase ofoil generation at about 7 Ma at 4,600 m. The hanging-wall Swat Formation has been in the early mature stage of oil generation since faulting. The timing of structural trap formation window is set to 4.1-1.8 Ma based on geological evidence from the literature. The results show trap formation is more or less contemporaneous with hydrocarbon generation and expulsion and timing will be critical for assessments of the prospectivity.

Evolutional Characteristics of Debris Flow in the Siwalik Hills of Nepal

As a youngest Mountain of the world, Siwalik region of Nepal is facing several mass movements like landslide and debris flow in monsoon period every year. Debris flow is very common in the steep slope of weak and fragile sedimentary rocks. This paper used remote sensing data and GIS to evaluate evolutional characteristics of debris flow hazard in the Siwalik hill of Babai watershed based on the geological, topographical and hydrological factors. All together 101 debris flow polygons were made by using Google Earth and by field verification. Digital Elevation Model (DEM) was used to analyze debris flow distribution and topographical features. Lithostratigraphy was studied to evaluate geological characters and rainfall data was used to evaluate hydrological character. Average slope for debris flow evolution in Lower, Middle and Upper Siwalik is 34&#176, 50&#176 and 30&#176 respectively. The average 24 hours rainfall to occur debris flow is found 160.67 mm. The area and length of debris flow channel are significantly different in three geological formations. The temporal distribution of debris flow from 2001 to 2018 shows that the trend of debris flow generation is higher in Middle Siwalik rocks with slope greater than 30&#176. Three major sources of debris flows were evaluated namely slide induced debris flow, fall induced debris flow and erosion induced debris flow where the slide induced debris flow is predominant. This study can be better source to understand the general mechanism of debris flow generation to the policy makers for reducing the future impact of debris flow in the overall Siwalik zone of Nepal.

New Fossil Reptile Records from the Siwalik of North 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.

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

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.

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

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

Geomorphological responses of rivers to active tectonics along the Siwalik Hills,Midwestern Nepalese Himalaya

The Nepalese Himalaya is well known for ongoing collisional tectonics,witnessed by major historical and recent earthquakes.The Siwalik Hills in Midwestern Nepalese Himalaya are bounded by eastwest trending Main Frontal Thrust(MFT)to the south and the Main Boundary Thrust(MBT)to the north.The area is dissected by numerous southwest to south-flowing bedrock rivers.This study investigates geomorphic metrics of these rivers to unravel landscape evolution and active tectonics of the Siwalik Hills.Digital Elevation Model(DEM)analysis was conducted to extract structural lineaments and longitudinal river profile and their metrics(knickpoints,Normalized Steepness Index(ksn),concavity index,and chi integral)using steam powerlaw approaches.Most of the lineaments trend eastwest like MFT.River profiles exhibit convex to double-concave shapes with upstream-propagating tectonic knickpoints that separate upstream and downstream reaches,indicating different phases of river incision.The spatial distribution of ksn shows high values along with low concavity values at the eastern part of the study area,reflecting disequilibrium conditions that are likely responding to a high uplift rate.Chi integral distribution shows a variation in drainage divide migration between the eastern and western parts of the study area.This study suggests that the rivers in the Siwalik Hills are undergoing active incision likely related to the ongoing uplift and active deformation associated with the Himalayan tectonics.The above findings can bring fresh perspectives to comprehend the neotectonic deformation and lateral variability along the Siwalik Hills landscapes within the Himalaya.

Size Analysis of the Late Pliocene-Early Pleistocene Upper Siwalik Sediments, Northwestern Himalaya, 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.

Petrology and Petrographic Delineation of Kamlial Formation Sandstone Mong and Thorar Village, Northern Pakistan

The origin of sandstone in the Rawalpindi group is disputed because of the lesser Himalayas complicated geological structure and ongoing tectonic activity. The goal of the study is to learn more about the petrographic and geological aspects of the Siwalik molasses deposits, which are formations that belong to the same age group. The Early Miocene Kamlial Formation, the Middle to Late Miocene Chinji Formation, and the Late Miocene Nagri Formation are the stratigraphic units revealed in the project area. The texture of the sandstone found in the Rawalpindi Group and Siwalik is fine to medium-grained. The hue ranges from grey to greenish grey. The sandstone displays thin to medium-bedded layers and exhibits thin lamination throughout. The sandstone of the Kamlial Formation contains load casts, potholes, worm burrows, hematite layers, and filled and unfilled mud cracks in basic structures. Model petrographic research reveals that the Murree Formation primarily consists of light minerals like feldspar, quartzite, and felice, whereas the Kamlial Formation is composed of heavy minerals like garnet and tourmaline. Sandstone from the Rawalpindi group undergoes analysis to ascertain its provenance using the quartz feldspar lithic fragments ternary diagram technique. Each plot in the QFL diagram’s recycled orogeny provenance field is plotted.

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

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.

印度Haritalyangar地区晚中新世猪类化石新材料

描述了印度北部比拉斯布尔区喜马偕尔邦Haritalyangar地区中西瓦利克的猪类化石上、下颌及牙齿材料。Haritalyangar地区以晚中新世动物群、古人类和其他灵长类动物的多样性而闻名。研究材料为作者之一(ARS)在该地区多次野外季采集的猪类化石;猪类化石地点和最近报道的长鼻类化石地点(含古猿化石地点)均被绘制在地图上。这些化石地点广泛分布于Makkan Khad到Sir Khad区域内的“Lower Alternations”层和“Upper Alternations”层。猪类化石被鉴定为3个属:原河猪属Propotamochoerus(P.hysudricus)、河马齿河猪属Hippopotamodon(H.sivalense)和云南猪属Yunnanochoerus(Y.dangari)。Propotamochoerus hysudricus为中西瓦利克最常见的化石猪类,新发现的Yunnanochoerus dangari进一步证明这种古猪类化石仅在Haritalyangar地区有少量遗存。Haritalyangar地区新发现的猪类化石组成与巴基斯坦的Nagri动物群相近。基于猪类化石进行的Potwar高原年代地层学对比表明,Haritalyangar地区的“Lower Alternations”层的年龄范围为~10–9 Ma,与最新的磁极性地层学年代范围很接近。

Palaeogeography, palaeohydraulics and palaeoclimate of the Mio-Pliocene Siwalik Group, eastern India

South-southwestward palaeocurrent swerved to east-southeast and then broadly to southeast over the transition from alluvial fan to axial channel and then to the flood plain in the Mio-Pliocene foreland system within which the Siwalik Group depositd in Darjeel- ing-Jalpaiguri Districts, eastern India. Palaeocurrent pattern is found to be multi-modal on the fans, virtually unimodal on the axial channel zone and again multi-modal, more profoundly, on the flood plain. Coarse siliciclastic mass-flows were progressively eliminated and gave way to predominant bed-load transport downfan and the axial river, and then to suspensionload dominance in fine siliciclastics on the flood plain. Distal flood plain lacustrine sediment included most of the coals and the entire bulk of the dolomitic limestone. Further resolution in palaeogeography within the frame of aforementioned foursome facies associations is elicited in twenty-six distinctive facies altogether. Critical evaluation of chemical indices （CIA, CIW, ICV, PIA, as well as Rb/Sr ratio） for weathering and depleted （3180 values indicate a high precipitation rate. The contention is further corroborated by the high discharge rate calculated from cross-set thicknesses within the main channel deposits. Reconciliation of various relevant data sets collected or calculated from all known worksites along the entire 2000 km-Iong exposure belt of the Siwaliks along the Himalayan foothills reveal confluence of two tributaries, one from the west and the other from the east, close to the present study area before escaping onto the Indian plains. Channel parameters, channel-belt width and discharge thus attained maxima in the present study area. The precipitation rate and temperature increased eastward overall as a prelude to the modern trend in this regard. 13C enrichment indicates that the transition from C3 to C4 vegetation had already set in.

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

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.

Clay Minerals as Climate Change Indicators—A Case Study

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. Post 1.7 Ma there was a marked shift in temperature patterns and subsequent cooling of the landmass, which resulted in a decreased vegetation cover and a subsequent decrease in animal population thriving on it.

New Discovery of Hipparion theobaldi Skull from the Late Miocene of Padhri,District Jhelum,Punjab,Pakistan and Associated Mammalian Fossil Assemblage

A fossil-bearing locality near Padhri village,Dhok Pathan,55 km away from the tehsil Dina,Jhelum District,in the Potwar Plateau,Middle Siwaliks,Punjab,northern Pakistan,is significantly rich in mammalian fossils.This site has provided an abundant mammalian fossil fauna of Late Miocene age from the Dhok Pathan Formation(Fm.).The recovered material belongs to four families:Equidae(horses),Rhinocerotidae(rhinos),Bovidae(cows),and Suidae(pigs).We discovered a new skull of hipparionine Hipparion theobaldi from this locality along with 22 specimens from the associated assemblage of fossil mammals.The recovered material includes seven other species:the aceratheriine Chilotherium intermedium,boselaphines Tragoportax punjabicus,Selenoportax vexillarius,Pachyportax latidens,the antelope Gazella lydekkeri and suinine Propotamochoerus hysudricus.The specimens are isolated teeth,fragments of maxilla,mandibles and horn cores.The Dhok Pathan Fm.is generally composed of claystone,siltstone and sandstone beds and,based on the mammalian fauna,the Padhri fossil locality is dated as Late Miocene.Thi99 s formation was deposited in a subtropical paleoenvironment and the predominance of fossil bovids indicates extremely moist conditions with small but frequent standing water bodies.

亚洲土著类群硅藻鼠科的演化(英文)

硅藻鼠科是仅分布于亚洲的啮齿类类群,头骨具豪猪型咬肌结构,下颌则为松鼠型。该类群代表了一个从梳趾鼠类分化出的区域性支系,虽与豪猪次目相近,但并不是它的成员。最早的硅藻鼠化石记录发现于Baluchistan渐新世陆相地层中,稍晚的记录发现于南业晚渐新世。印度次大陆连续的地层为该科的演化历史提供了主要的化石依据。早中新世晚期至中中新世,硅藻科化石也发现了泰国、中国以及日本。其后的硅藻鼠种类少且鲜有化石记录。晚中新世早期在巴基斯坦有一个种,中国南部晚中新世也可能有一个种。尽管在最早的化石地点发现的标本较多,但其后的时段内除泰国李盆地外化石并不丰富,这指示了其特殊的生活习性或其生活区域化石保存的偏差。已知的化石记录并没有指示出该类群的多样性,也可能是缺少石化作用的结果。硅藻鼠类在水系外围区域延续生存与最近在老挝中部多岩石地带发现的现生Laonastes也是一个硅藻鼠的假设相一致。

查谟-克什米尔桑巴地区上西瓦立克亚群中的平额象化石（英文）

报道和描述了一件平额象左侧M3化石。新材料产自Nangal村附近火山灰层之下的泥岩层,该火山灰是出露于查谟-克什米尔桑巴地区Barakhetar上西瓦立克亚群Nagrota组中年龄为2.48 Ma的火山灰层的延伸。根据齿板数,臼齿长和宽,齿冠长、宽和高,釉质和齿质厚度,齿板长和宽,齿脊频率,冠高指数以及白垩质厚度等齿冠形态参数,暂时将之归为Elephas cf.E.planifrons。新材料的发现将该种的分布上限从2.6 Ma提高到2.48 Ma。

查谟-克什米尔地区查谟后西瓦立克沉积中的亚洲象化石

描述了一件象属( Elephas) 的右上臼齿化石。标本产自查谟紧靠上西瓦立克亚群巨砾岩组( Boulder Conglomerate Formation) 之上的砂质、粉砂质泥岩夹砾石层中,化石地点位于查谟市南10 km,Kharian 村北约500 m 处。根据齿板数、齿脊频率、釉质层厚度、冠高指数、绝对大小和齿长/齿高指数等牙齿形态参数,暂时将之归为 Elephas cf. E. maximus indicus。还简短讨论了象属的地理分布和地质时代。

巴基斯坦西瓦里克道克派珊组豕脊齿象属(长鼻目)新材料（英文）

褶齿豕脊齿象(Choerolophodon corrugatus)是豕脊齿象属在巴基斯坦西瓦里克群发现的唯一种。其首次发现是在西瓦里克亚群下部的卡米列组(中新世晚期),而后大量见于西瓦里克亚群中段的道克派珊组(中新世晚期至上新世早期)。本次报道的褶齿豕脊齿象新材料发现于道克派珊模式产地及其邻近区域。发现的材料包括象牙、下颌、上颌碎片以及一些乳前臼齿和臼齿。新材料与欧洲的Ch. pentelici的牙齿特征极其相似,但在头骨和下颌特征上有所区别。