Himalayan Foreland Basin Research Articles

Facies architecture and depositional evolution of Palaeocene–Eocene, Subathu Formation, Garhwal Himalaya, Uttarakhand, India

The Late Palaeocene–Middle Eocene marine sedimentary sequence of the Himalayan foreland basin, represented by the rocks of Subathu Formation, is enriched with the presence of foraminifera, bryozoa, corals, gastropods, bivalves and so on within both carbonate and clastic dominant lithologies. The carbonate and the shale consist mainly of larger benthic foraminifera (LBF) and the assemblage is composed of Nummulites and Assilina along with the other skeletal and non-skeletal components. The presence of a palaeosol at the base of Subathu indicates a gap in sedimentation. The lithological and biotic assemblages along with the bed form, bed geometry and primary sedimentary features helped us to establish four facies associations, A, B, C and D, and have been corroborated with the shoreline migration (transgression/regression) history. The facies association-A, representing the basal horizons of Subathu Formation, indicates the onset of transgression and deposition in lagoonal condition with carbonaceous shale and oolitic ironstone, followed by the facies association-B and -C deposited in shallow marine shoreface. The uppermost unit, i.e., the medium- to coarse-grained sandstone (facies association-D) of Subathu Formation, represents a fall in relative sea level (progradational stacking pattern), whereas the underlying contact between the facies association-B and -C is represented by an aggradational stacking pattern between the siltstone and the shale, but certainly without exposing the shelf. Petrographic studies based on characteristic features such as framework constituent, the percentage of matrix and grains, nature of cementing material, textural features and fossil content help to deduce a distinct change in depositional setting from an open marine (shelf) to shoal, a lagoon that gradually grades to foreshore/beach environment. The study reveals that the basin has gone through a transgressive (facies association-A and -B), regressive (facies association-C) as well as distinct forced regressive (facies association-D) phase of shoreline migration history.

Lithofacies analysis and economic mineral potential of a braided fluvial succession of NW Himalayan foreland basin Pakistan

This study has described detailed lithofacies analysis, clay mineralogy, and depositional setting, and highlighted economic mineral potential of late Miocene to Early Pliocene mid Siwalik Dhok Pathan Formation. The Siwalik fluvial sedimentary succession is 5300 m thick in the NW Himalayan foreland fold-and-thrust belt known as Surghar-Shingar Range (SSR). The middle Siwalik (Dhok Pathan Formation) typically represents cyclic alternation of massive sandstones, siltstones, mudstones, and claystones in repeated fining upward rhythm with varied thicknesses from 807 to 1540 m. Detailed sedimentological investigations resulted in the identification of seven distinct lithofacies (Gt, St, Sh, Ss, Sl, Fm, and Fl) which had been deposited by sand-dominated bed load braided fluvial system. The facies Sh is hosting detrital uraninite identified through a scanning electron microscope (SEM). X-Ray diffraction analyses revealed that kaolinite, smectite (montmorillonite and saponite), illite, vermiculite, and chlorite (clinochlore and chamosite) are the main clay mineral suits present in the formation. The morphology of clay mineral suits is indicative of weathering products or contribution from the source areas. The absence of glass shards and mineral analcimolite evidenced that these smectite group clay minerals were not derived from the devitrification of volcanic ashes. The sedimentological analysis, mineralogical composition, and paleo-flow directions revealed that these sediments had been deposited by NS fluvial system presently known as Indus River system in this area. The rare earth element concentrations of sandstone and heavy minerals laminations (black sand) show enrichment of uranium (662 ppm), thorium (1374 ppm), La (975 ppm), Ce (2831 ppm), Pr (193 ppm), Nd (746 ppm), Gd (98 ppm), and Dy (50.8 ppm), which specify good indicative economic mineral potential of the formation.

Spatial heterogeneity in the relationship between precipitation and carbon isotopic discrimination in C3 plants: Inferences from a global compilation

Abstract Understanding the causes of large variations in carbon isotopic composition of C3 plants (δ13CC3) is a key challenge for paleoenvironmental reconstruction. Several investigations have attempted to study the global patterns in the δ13CC3 values and their correlation with the precipitation variability. Sparse representation of dataset from low-latitude and equatorial regions in the existing global compilation hinders to understand the precipitation-δ13CC3 gradient at different latitudinal-bands. In the present study, available global compilation has been extended with the newly measured dataset, and the new compilation (ca. 1.5 times larger than previous dataset) comprises results from 720 sites across the world. All the δ13CC3 values have been converted to carbon isotopic discrimination between air and leaf (Δair-leaf). Mann-Whitney analysis indicates distinct region-specific distribution of the Δair-leaf values. The average Δair-leaf value in mid-latitude region of the Northern Hemisphere is ca. 2‰ lower than equatorial sites. Multiple linear models have been used to investigate relative influence of climatic (precipitation and temperature) and geographical factors (altitude and latitude) on the Δair-leaf values. This analysis shows that precipitation controls the Δair-leaf values in every latitudinal-bin though the effect of precipitation is negligible beyond 1500 mm. Furthermore, the Δair-leaf-precipitation gradient has a large spatial variability and the most prominent changes in the Δair-leaf values have been observed at arid regions in mid-latitudes of the Southern Hemisphere (maximum 1.3‰ 100 mm−1). Region-specific distribution of δ13C values of plant and Δair-leaf-precipitation gradient prompt to recalculate the relative abundance of C3–C4 plants in the Siwalik sections of the Himalayan foreland basin. Our results show that earlier investigations in the Siwaliks for the Middle-Late Miocene have underestimated the abundance of C4 plants by ca. 20%. The recalculation shows that C4 plants existed in these regions earlier (ca. 17 Ma) than the previously proposed timings.

The Himalayan Foreland Basin from collision onset to the present: a sedimentary–petrology perspective

Abstract This chapter summarizes the available stratigraphic, petrographical and mineralogical evidence from sediments and sedimentary rocks on the evolution of the Himalayan belt and its associated foreland basin. The use of compositional signatures of modern sediments to unravel provenance changes and palaeodrainage evolution through time is hampered by a poor match with detrital modes of ancient strata markedly affected by selective chemical dissolution of unstable minerals during diagenesis. Only semi-quantitative diagnoses can thus be attempted. Volcanic detritus derived from Transhimalayan arcs since India–Asia collision onset at c. 60 Ma was deposited onto the Indian lower plate throughout the Protohimalayan stage, with the exception of the Tansen region of Nepal that is characterized by quartz-arenites yielding orogen-derived zircon grains. During the Eohimalayan stage, begun in the late Eocene when most sedimentation ceased in the Tethys Himalayan domain, low-rank metasedimentary detritus was overwhelming in the central foreland basin, where a widespread unconformity developed spanning locally as much as 20 myr. Volcanic detritus from Transhimalayan arcs remained significant in northern Pakistan. Arrival of higher-rank metamorphic detritus since the earliest Miocene, and the successive occurrence of garnet, staurolite, kyanite and finally sillimanite, characterized the Neohimalayan stage, when repeated compositional changes in the foreland-basin succession document the stepwise propagation of crustal deformation across the Indian Plate margin and widening of the thrust belt with exhumation of progressively more external tectonic units. The correspondence in time between the activity of major thrusts and petrofacies changes indicates a promising approach to accurately reconstruct the geological evolution of the coupled orogen–basin system. Conversely, a poor conceptual framework and the general reliance on ad hoc mechanisms to explain phenomena unpredicted by simplified models represent major factors limiting the robustness of palaeotectonic interpretations. Improved knowledge requires taking into full account the dynamic role played by still poorly understood subduction processes – rather than exclusively the effect of passive loading – as well as the role played by the presence of inherited structures on the downgoing Indian Plate, which control both lateral variability of orogenic deformation and the location of depocentres in the foreland basin.

PROVENANCE OF KARAKUM DESERT SAND (TURKMENISTAN): LITHIC-RICH OROGENIC SIGNATURE OF CENTRAL ASIAN DUNE FIELDS

Major deserts do not necessarily consist of eolian dunes as quartz-rich as those of the Great Nafud, Rub’ al Khali, Sahara, and Mega-Kalahari sand seas accumulated in anorogenic settings of Arabia and Africa. The Karakum dune field of Turkmenistan is one of the several examples of central Asian deserts bound by recent or recently reactivated orogenic belts where eolian sand includes abundant sedimentary and subordinately metamorphic and volcanic lithic fragments. Feldspatho-litho-quartzose detrital modes and epidote-amphibole-garnet heavy-mineral suites of southern Karakum dune sand compare well with those in mountain branches of the Amu Darya, indicating provenance from the western Pamir mountains of Tajikistan in the east. Dunes closer to the Caspian Sea in the west contain additional carbonate or felsic volcanic grains which, together with decreasing heavy-mineral concentration and increasing ZTR indices, reveals local recycling of cover strata exposed in the Kopeh-Dagh and Balkhan zone. Our data suggest that the huge Amu Darya River, which in Plio-Pleistocene to historical times has repeatedly changed its course across Turkmenistan from westward toward the Caspian Sea to northward toward the Aral Sea, represents the major sediment source for the Karakum Desert. Together with the Taklamakan sand sea of the Tarim basin, the Ordos and adjacent deserts of northern China, and the Thal and Thar deserts of the western Himalayan foreland basin, the Karakum would thus represent another example of large dune field principally fed by one major fluvial feeder system.

Detrital zircon U–Pb geochronology of a Cenozoic foreland basin in Northeast India: Implications for zircon provenance during the collision of the Indian and Asian plates

AbstractGeochronology is useful for understanding provenance, and while it has been applied to the central and western Himalaya, very little data are available in the eastern Himalaya. This study presents detrital zircon U–Pb ages from the late Palaeocene–Eocene Yinkiong Group in NE India. The samples are from the late Palaeocene to early Eocene Lower Yinkiong Formation, and the Upper Yinkiong Formation deposited during the early to mid‐Eocene within the Himalayan foreland basin. The U–Pb ages of the detrital zircon within the Lower Yinkiong Formation are older than late Palaeozoic, with a cratonic and early Himalayan Thrust Belt affinity, whereas the Cenozoic grains in the Upper Yinkiong Formation indicate a Himalayan Thrust Belt source and possibly a granitic body within the Asian plate. The shift of the sources and the changes in the foreland basin system strongly suggest that the India–Asia collision in the Eastern Himalaya began before or immediately after the deposition of the Upper Yinkiong Formation, i.e., within the early Eocene (c. 56 to 50 Ma).

The tectonics and paleo-drainage of the easternmost Himalaya (Arunachal Pradesh, India) recorded in the Siwalik rocks of the foreland basin

The Siwalik sedimentary rocks of the Himalayan foreland basin preserve a record of Himalayan orogenesis, paleo-drainage evolution, and erosion. This study focuses on the still poorly studied easternmost Himalaya Siwalik record located directly downstream of the Namche Barwa syntaxis. We use luminescence, palaeomagnetism, magnetostratigraphy, and apatite fission-track dating to constrain the depositional ages of three Siwalik sequences: the Sibo outcrop (Upper Siwalik sediments at ca. 200–800 ka), the Remi section (Middle and Upper Siwalik rocks at >0.8–

Himalayan Paleogene Foreland Basin, its collision induced early volcanic history and failed rift initiation

The Himalayan Foreland Basin was formed over a failed rift zone that produced early Paleogene volcanism, which was synchronous to Indo-Asia collision. The rift zone was located over acutely flexed leading edge of the Indian continental crust. The volcanism preceded upliftment of the proto-Himalaya. The Jammu Himalaya is one of the few areas exposing the basal part of the foreland basin comprising a persistent horizon of volcani-sedimentary rhyolitic chert breccia at the base of the Subathu Formation, which unconformably overlies the Precambrian Jammu Limestone. Contemporaneous felsic ash beds occur in the Subathu-Kalka area in the Simla Hills at the base of the Subathu Formation unconformably overlying the Precambrian Simla Group. In Arunachal Pradesh, in the eastern-most Himalaya, early-mid Eocene foraminifera fauna bearing Yinkiong Formation overlies the Abor Volcanics. The age of the latter is disputed: whether it is early Permian or Eocene in age, or it exposes a mixture of both components. Recent U-Pb SHRIMP zircon geochronological study indicates Abor Volcanics being part of the Kerguelen mantle plume trail traversing Southern Tibet, Sylhet, Rajmahal, Bunbury and Kerguelen Plateau. Trace element geochemistry of the Abor Volcanics, the exposed volcanic rocks around Yinkiong and those exposed between Pangin and Rotung indicate rift signature. In the frontal belt, early Eocene shallow marine sediments locally associated with mafic volcanics occur tectonically at the base of the early Neogene foreland sequence. The latter is locally thrust at MBT by the early Permian meta-sediments tectonically intermixed with marine Eocene rocks. Early Eocene sediments and rift related mafic volcanics from Arunachal Pradesh possibly occur at the tectonic base of the Tertiary foreland basin sequence from northeastern Himalaya. The early Paleogene mafic volcanics from the Arunachal Pradesh and coeval acid volcanics occurring at the base of the Paleogene sequence in Jammu-Simla Himalaya might represent cogenetic bimodal volcanism.The Subathu Formation with its coal and carbonaceous sediments is lithologically similar to the coal and mud-rock bearing late Paleocene Patala Formation or the Hangu Formation and early Eocene Ghazij Formation from the adjacent Indus Foreland Basin, Pakistan, which overlie the Mesozoic-Paleocene carbonate flat. Although, the lithofacies and sedimentary tectonic setting of the Patala, Hangu and the Ghazij formations are similar to that of the Subathu Formation, the former units typically lack the presence of syn-sedimentary ash beds or any other volcanic rocks that are characteristically present at the base of the Subathu Formation. Mainly late Paleocene coal bearing Patala and the Hangu formations in Salt Range and North Potwar area, Pakistan, although located close to the Jammu sector of the Himalayan Foreland Basin is free of any volcanic activity. Salt Range and Potwar areas are possibly not parts of the foreland fold-and-thrust belt of the Himalaya, as postulated by some workers. Geodynamically Salt Range and Potwar basins belong to northern parts of the Indus Foreland Basin, because the depositional basin from Potwar extending into the adjacent Kohat area during the Paleocene and the Eocene time probably formed a collision zone between the India-Pakistan plate and a micro-continent prior to the collision of the former with Asia. The micro-continent possibly buffered intensity of collision, thereby, there was no tectono-magmatic activity along this belt as distinct from that of direct collision between India and Asia continent.

Paleocene orthophragminids from the Lakadong Limestone, Mawmluh Quarry section, Meghalaya (Shillong, NE India): implications for the regional geology and paleobiogeography

Abstract. The late Paleocene orthophragminids, hitherto poorly known from the Himalayan foreland basins, are studied from the Lakadong Limestone in Meghalaya, northeastern India, in order to establish a systematic, biostratigraphic, and paleobiogeographical framework for them in the eastern Tethys. In the Mawmluh Quarry section (MQS) on the Shillong Plateau, to the southeast of Tibet, orthophragminids are associated with typical Paleocene orbitoidiform taxa endemic to the Indian subcontinent, i.e., Lakadongia Matsumaru & Jauhri (= Setia Ferràndez-Cañadell) and Orbitosiphon Rao, and various species of alveolinids, miscellaneids, and rotaliids, characterizing the Shallow Benthic Zones (SBZ) 3 and 4. The orthophragminids belong to two lineages of the genus Orbitoclypeus Silvestri: O. schopeni (Checchia-Rispoli) and O. multiplicatus (Gümbel), both well known from the peri-Mediterranean region and Europe (western Tethys). The latter species is identified here for the first time from the eastern Tethys. Previous records of the genus Discocyclina Gümbel from the Lakadong Limestone actually correspond to misidentified Orbitoclypeus; this implies that the late Paleocene orthophragminid assemblages from Meghalaya and eastern Tethys were less diverse than in the western Tethys. The lineage of Orbitoclypeus schopeni in the lower part of the Lakadong Limestone (SBZ 3) is identified as O. schopeni cf. ramaraoi based on the morphometry of a few specimens, whereas in the upper part (SBZ 4) it corresponds to a transitional development stage between O. schopeni ramaraoi and O. schopeni neumannae (with average Dmean values ranging between 192 and 199 µm). The embryon diameters of O. multiplicatus, recorded only in SBZ 4, range between 300 and 319 µm on average, corresponding to transitional development stages of O. multiplicatus haymanaensis and O. multiplicatus multiplicatus. Our data, along with a review of previous Paleocene and Eocene records from India and Pakistan, suggest that Orbitoclypeus is the only orthophragminid in the Paleocene of the eastern Tethys, whereas Discocyclina first appears in early Eocene times, being mainly represented by endemic taxa confined to the Indian subcontinent. Facies change in the MQS from a marine to continental setting within SBZ 4 corresponds to the oldest record from the Indian plate in the Paleogene, which may be linked to the flexural uplift of the passive margin of the Indian plate, marking the onset of the collision of the Indian and Eurasian plates.

Petrography and provenance of the Early Miocene Murree Formation, Himalayan Foreland Basin, Muzaffarabad, Pakistan

Murree Formation lies in the core of Hazara Kashmir Syntaxis, Sub-Himalayas, Pakistan. In the Muzaffarabad area, the Murree Formation extends from Ghori to Nauseri. The Early Miocene Murree Formation is underlain unconformably by the Ypresian to Early Lutetian Kuldana Formation and is in a fault contact with the Permian Panjal Formation. The Murree Formation contains litharenite and feldspathic litharenite. All of the plots in the QtFL diagram fall in recycled orogen provenance field, whereas ternary diagram (QmFLt) also suggests transitional recycled to quartzose recycled orogenic provenance for the sandstone of Murree Formation. Orogenic recycling occurs in the Lesser and Higher Himalayas where stratified rocks are deformed, uplifted and eroded. The detritus was then deposited in the Himalayan Foreland Basin by river meandering system. The detritus of rock fragments strongly suggests mixed sources of the Murree Formation sandstones. The modal analysis data were plotted in a diamond diagram for the recognition of the sediment source and tectonic setting of the provenance. The frequency of the non-undulatory monocrystalline quartz (Qnu) is larger in the sandstone as compared to the frequency of the undulatory monocrystalline quartz (Qu) and polycrystalline quartz (Qp). The greater abundance of Qnu suggests plutonic provenance for these sandstones. The plot of Q/(F + L) against Qp/(F + L) reveals that during the deposition of Murree Formation, the climatic conditions were semi-arid to semi-humid. The XRD analyses of shale samples indicate quartz, carbonate and clays vary from 66–89%, 1–25% and 1–21%, respectively.

Timing and mechanism of the rise of the Shillong Plateau in the Himalayan foreland

Abstract The Shillong Plateau (northeastern India) constitutes the only significant topography in the Himalayan foreland. Knowledge of its surface uplift history is key to understanding topographic development and unraveling tectonic–climate–topographic coupling in the eastern Himalaya. We use the sedimentary record of the Himalayan foreland basin north of the Shillong Plateau to show that the paleo-Brahmaputra river was redirected north and west by the rising plateau at 5.2–4.9 Ma. We suggest that onset of plateau uplift is a result of increased fault-slip rates in response to stresses caused by the Indian lithosphere bending beneath the Himalaya.

Micromorphological studies of the complex early Oligocene Himalayan foreland palaeosols in relation to Asian monsoon climate

The Cenozoic Himalayan orogeny not only modified Asia's climate but also affected global climate. One of its significant outcomes is the inception of Asian monsoon climate. Though researchers have shown that changes in Himalaya and Tibetan Plateau elevations control its evolution, however reached no consensus on pre-Miocene timing of monsoon climate inception, perhaps due only limited studies in pre-Miocene Himalayan sediments. Another possibility is that we have restricted our studies in deducing a relationship between Himalayan tectonic upheavals and monsoon climate. However, priority should be to first explore any palaeomonsoon signatures since deposition of Himalayan Foreland Basin (HFB) sediments because some researchers have reported palaeomonsoon signatures during Eocene-Oligocene time. Here we report another such study from early Oligocene Dagshai palaeosols of Subathu sub-basin, India. Detailed morphological and micromorphological studies revealed abundant presence of matrix and intrusive pedofeatures in mature palaeosol profiles. Most striking evidence is the presence of FeMn oxide and carbonate pedofeatures together. The concretions present in the thick Bk horizons having diffuse boundaries show intermixing and/or alternation of calcite and iron oxides. Also occurrence of pedogenic carbonate nodules is not restricted in Bk horizon as is observed in present monsoon dominant regions and nodules are impure, dense and largely micritic, similar to those documented in Indo-Gangetic Holocene soils. Further, most common FeMn oxide nodules are typical, impregnative and associated with granostriated fabric which is indicative of soils formed under seasonal wet and dry cycles. Furthermore, occurrence of illuvial coatings and carbonate together in the B-horizon indicate prevalence of sufficient wet and dry cycles respectively. All these features indicate presence of seasonal climatic conditions and therefore monsoon conditions prevailed during early Oligocene time which is contrary to the most common known Late Miocene age of Indian Monsoon inception.

Petrotectonic setting of the provenance of Lower Siwalik sandstones of the Himalayan foreland basin, southeastern Kumaun Himalaya, India

AbstractDetailed petrography and modal analysis of 35 sandstone thin sections was carried out to determine petrotectonic setting of the provenance of the Lower Siwalik molasse of southeastern Kumaun Himalaya. The sandstones are fine‐ to coarse‐grained (0.14–0.63 mm), poorly‐ to moderately‐sorted and comprise lithic arenites, sublithic arenites and lithic greywackes. The sandstones invariably belong to the quartzolithic QtFL (Qt, total quartz; F, feldspar; L, lithic grains) and QmFLt (Qm, monocrystalline quartz; Lt, lithic grains plus polycrystalline quartz) petrofacies, and indicate their derivation from a quartzose‐ and transitional‐recycled orogen provenance under sub‐humid climatic conditions. The framework composition of the sandstones comprises abundant monocrystalline and polycrystalline quartz and low‐ to high‐grade metamorphic rock fragments, along with subordinate feldspar, characterized by low ratios of plagioclase to total feldspar, and accessory minerals. The framework composition and petrofacies characters of these texturally submature sandstones suggest their derivation mainly from the nearby located Great Himalaya terrane and subordinately from the Tethys and Lesser Himalayan terranes. A comparison of the data presented here with the previous similar data from Lower Siwalik of northwestern Pakistan, northwestern India, south‐central Kumaun, western Nepal and southeastern Nepal reveals that like the Lower Siwalik rivers in other sections, the Lower Siwalik rivers of the southeastern Kumaun too drained large parts of the Great Himalayan terrane and some parts of the Tethys and Lesser Himalayan terranes.

Morphotectonic analysis of alluvial fan dynamics: comparative study in spatio-temporal scale of Himalayan foothill, India

Alluvial fan is a depositional fluvial landform that is characterised by sediment flow and hydrological processes and is also controlled by tectonic activity. These extraordinary features have always attracted researchers since the past as they preserve the past records, but now, this study is focused on the formation meso-level fans with its spatio-temporal dynamic nature. These tributaries have formed secondary alluvial fans at their debouching points. The dynamics of the fans are controlled by the hydrological responses and tectonic base and also by the sedimentation processes. The origin of these tributaries and their respective fans are related to the last stage of Himalayan uplift. This is the region of Himalayan foreland basin which contains the main frontal thrust and makes the region tectonically very active. The region is drained by many large rivers and their numerous tributaries. The active tectonism, the configuration of the basin and also the deposition of the sediments carried by these rivers have formed alluvial fans where the channel debouches into the widened valley. In the present study, the meso-level alluvial fans formed by River Gish and the Rivers Neora and Murti have been studied. Both these fans are present in the piedmont region of the Himalayas, but they deliver different characteristics, and the nature of their deposition is also different. This is mainly because of the influence of the minor faults in the region which control the channel pattern and also have a great influence in the sediment delivery to the downstream section of the channels. Thus, in order to understand the influence of tectonics in the dynamics of these fans, some morphotectonic parameters have been taken into consideration. These include mountain front sinuosity index, valley floor width-to-depth ratio, and tectonic tilt. The calculated hypsometric integral also depicts that the two fans are at different stages of development.

Middle Miocene small mammals from the Siwalik Group of Northwestern India

The freshwater Siwalik deposits of the Himalayan foreland basin have long been known to yield prolific Miocene-Pleistocene mammalian fauna. Overwhelming of this data comes from the Siwalik sequence of Pakistan, where good palaeomagnetic control is available for various Siwalik lithounits. In contrast limited data on fossil mammals, more so on small mammals, is available from the Indian side of the Siwalik, where even most of the Siwalik formations lack palaeomagnetic and or radiometric calibration, despite the fact that several fossil yielding localities are known in India since long. In the present research work, small mammals discovered from a Lower Siwalik locality near Ramnagar town in Jammu province, Jammu and Kashmir State, India are reported and their age implication is discussed. The mammal fauna from the study area contains four species of rodents belonging to four subfamilies. These include Rhizomyinae represented by Kanisamys indicus, Ctenodactylinae by Sayimys sivalensis, Myomiminae by Myomimus sp. and Xerinae by Tamias urialis. The recovered biotas improve our knowledge on the rodent diversity of the Indian Lower Siwalik Subgroup and contribute to further constrain the age of the fossiliferous horizon between 13.6 and 13.2 Ma. The new fauna suggests a humid, forested palaeoecological setting.

Siwalik-age faunas from the Himalayan Foreland Basin of South Asia

The Himalayan foreland basin is characterised by three principal sedimentary successions. These are the Subathu Group (Palaeocene-Eocene), the Murree or Dharamsala Group (Oligocene-Miocene) and the Siwalik Group (Miocene-Pleistocene). The basin was linked in the east to the Bay of Bengal through the Bengal Basin and its western part was connected to the Arabian Sea through Rajasthan and Kachchh, Gujarat. The Himalayan foothills have long been known for yielding rich mammalian fossil occurrences and significant localities in the Indian Siwaliks include Kalagarh, Ramnagar, Haritalyangar, Chandigarh and Jammu regions. The Bugti Basin and Zinda Pir area of Sulaiman Range of Pakistan were also part of the foreland basin, as Lower and Middle Siwalik fossils are known from the Vihowa and Litra formations, respectively. The Marwat Formation of Bhittani and Marwat Ranges, Pakistan have also yielded Pinjor-age vertebrate fossils. The Middle and Upper Siwalik-age fossils are also known from the Irrawaddy Formation of Myanmar, where older Pegu beds have also yielded scanty Lower Siwalik-age fossils. This faunal succession in the Irrawaddy Valley may have geologically and biogeographically belonged to the Himalayan foreland basin in the past. Additional mammalian fossils having an affinity with the Lower and Middle Siwaliks are known from the Khari Nadi Formation of Kachchh. The Bokabil Formation of Tripura also yielded scanty Lower to Middle Siwalik fossils. A younger Siwalik late Miocene assemblage is known from Piram Island of Gujarat. These areas are also part of the foreland basin. Most recently, a late Miocene suid species was discovered and reported from near Baripada, Odisha. The paper discusses the respective faunal lists of the various successions mentioned above. Finally, the paper discusses the implications of the foreland faunas. The faunas of Lower and Middle Siwaliks of foreland basin have links with Europe, Turkey, Africa and Central Asia and throw light on the uplift of the Himalaya. The post-Siwalik faunas of central and Peninsular India and Indo-Gangetic Plains have also yielded remnant Siwalik taxa, including Stegodon insignis, Elephas hysudricus and Potamochoerus theobaldi. The Kurnool Cave Fauna and Recent Fauna of India have also generic resemblance with the foreland faunas.

Weathering in the Himalaya, an East-West Comparison: Indications from Major Elements and Clay Mineralogy

Studying past weathering regimes is important for a better understanding of the influence of climate on weathering, erosion, and runoff. The Himalayan foreland basin contains a record of tectonics and paleoclimate since Miocene times. Spanning the entire mountain range, the Mio-Pliocene detrital Siwalik Group allows studies to directly compare the western and eastern Himalaya within similar sedimentary settings. In this study, we use major elements and clay mineralogy to reconstruct the weathering regime along strike since Miocene times. We studied previously dated Dharamsala (pre-Siwalik) and Siwalik sections in the western (Joginder Nagar, Jawalamukhi, and Haripur Kolar) and eastern (Kameng) Himalaya in order to constrain variations in weathering regimes along strike. The compilation of the three sections in the west makes for one of the longest continuous sedimentary records in the Himalaya, spanning over 20 My. The K/Al ratio is used as a reliable weathering proxy and shows a trend toward more intense weathering over time in both the west and the east, but with sediments in the western Himalaya generally more weathered than those in the east, despite higher precipitation in the east. Clay minerals and major elements indicate similar lateral variations in weathering. More intense weathering in the west is linked to a more seasonal climate, permitting weathering of sediments during the dry season, whereas higher runoff in the east leads to more rapid erosion and sediment transport, inhibiting extensive weathering.

A new murid rodent assemblage from the Upper Siwaliks, Himachal Pradesh, India: Biostratigraphic, phylogenetic and palaeobiogeographic implications

In case of freshwater deposits that cannot be isotopically dated or that lack a continuous sequence for magnetostratigraphic study, rodent biochronology is an useful tool in making intra-regional biostratigraphic correlations and dating isolated Siwalik fossil localities within the Himalayan Foreland Basin. We here, report a new fossil locality exposed near the Village Devni Khadri situated close to the Markanda River Valley (District Sirmaur, Himachal Pradesh, India). This Upper Siwalik locality belonging to the Tatrot Formation contains a diverse fauna and flora including large mammals, birds, crocodiles, fishes, gastropods, bivalves, ostracods and charophytes beside dental remains of murid rodents Golunda kelleri, Mus flynni, Mus jacobsi and Abudhabia cf. A. kabulense. Based on the biostratigraphic ranges of these murid rodents from well dated Siwalik and Karewa localities, this richly fossiliferous locality has been placed here at ∼3Ma. The new age facilitates regional correlation and a revision of stratigraphic placement of rodent bearing Plio-Pleistocene Indian sites. A PAUP based cladistic analysis of fossil and extant Golunda and its relatives suggest the monophyly of the Golunda group, and a close relationship between African and Asian forms. Presence of common rodent elements in the fossil record of Africa and Asia points towards possible inter-continental dispersal in Pliocene time.

Lateral variations in vegetation in the Himalaya since the Miocene and implications for climate evolution

The Himalaya has a major influence on global and regional climate, in particular on the Asian monsoon system. The foreland basin of the Himalaya contains a record of tectonics and paleoclimate since the Miocene. Previous work on the evolution of vegetation and climate has focused on the central and western Himalaya, where a shift from C3 to C4 vegetation has been observed at ∼7 Ma and linked to increased seasonality, but the climatic evolution of the eastern part of the orogen is less well understood. In order to track vegetation as a marker of monsoon intensity and seasonality, we analyzed δ13C and δ18O values of soil carbonate and associated δ13C values of bulk organic carbon from previously dated sedimentary sections exposing the syn-orogenic detrital Dharamsala and Siwalik Groups in the west, and, for the first time, the Siwalik Group in the east of the Himalayan foreland basin. Sedimentary records span from 20 to 1 Myr in the west (Joginder Nagar, Jawalamukhi, and Haripur Kolar sections) and from 13 to 1 Myr in the east (Kameng section), respectively. The presence of soil carbonate in the west and its absence in the east is a first indication of long-term lateral climatic variation, as soil carbonate requires seasonally arid conditions to develop. δ13C values in soil carbonate show a shift from around −10‰ to −2‰ at ∼7 Ma in the west, which is confirmed by δ13C analyses on bulk organic carbon that show a shift from around −23‰ to −19‰ at the same time. Such a shift in isotopic values is likely to be associated with a change from C3 to C4 vegetation. In contrast, δ13C values of bulk organic carbon remain at ∼−23‰ in the east. Thus, our data show that the current east–west variation in climate was established at 7 Ma. We propose that the regional change towards a more seasonal climate in the west is linked to a decrease of the influence of the Westerlies, delivering less winter precipitation to the western Himalaya, while the east remained annually humid due to its proximity to the monsoonal moisture source.

Lithofacies characters and depositional processes of a Middle Miocene Lower Siwalik fluvial system of the Himalayan foreland basin, India

The Lower Siwalik sequence in south-eastern Uttarakhand state of India records fluvial sedimentation during middle Miocene in the Himalayan foreland basin. Three distinct lithofacies associations (‘A’, ‘B’ and ‘C’) have been identified, each one of which comprises one or more of the eight major lithofacies and points to specific sub-environments of fluvial depositional setting. The lithofacies association ‘A’ is sandstone dominated and suggests deposition mainly by 0.09–2.0m/s flowing traction currents in braided streams. The lithofacies association ‘B’ is sandstone–mudstone dominated and suggests deposition by 0.1–1.0m/s flowing traction currents as well as suspension fallout in meandering streams and adjoining overbank areas. The facies association ‘C’ is mudstone dominated, characteristically pedogenically altered and disassociated with any major channel sandstone body. It represents reworking of pre-deposited sediments by ephemeral sheet and shallow channelized flows in the upland interfluve regions. The palaeoflow pattern reveals regional radial outward sediment dispersal by a distributary fluvial system, indicating convex-up transverse surface profile. The dominance of fine- to medium-grained sand and general absence of coarser extrabasinal clasts suggests that this distributive fluvial system of meandering and braided streams was located in the middle-distal part of a megafan. The upland interfluve surface developed following the cessation of megafan surface aggradation due to incision of major river channels.