Evolution of the Paleogene Succession of the Western Himalayan Foreland Basin

Geoscience Frontiers 4 (2013) 199e212

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China University of Geosciences (Beijing) Geoscience Frontiers

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Research paper Evolution of the Paleogene succession of the western Himalayan foreland basin

B.P. Singh*

CAS in Geology, Banaras Hindu University, Varanasi-221005, India article info abstract

Article history: The Paleogene succession of the Himalayan foreland basin is immensely important as it preserves Received 19 July 2012 evidence of India-Asia collision and related records of the Himalayan orogenesis. In this paper, the Received in revised form depositional regime of the Paleogene succession of the Himalayan foreland basin and variations in 31 August 2012 composition of the hinterland at different stages of the basin developments are presented. The Accepted 24 September 2012 Paleogene succession of the western Himalayan foreland basin developed in two stages, i.e. syn- Available online 2 November 2012 collisional stage and post-collisional stage. At the onset, chert breccia containing fragments derived from the hanging walls of faults and reworked bauxite developed as a result of erosion of the forebulge. Keywords: Facies architecture The overlying early Eocene succession possibly deposited in a coastal system, where carbonates repre- Provenance sent barriers and shales represent lagoons. Up-section, the middle Eocene marl beds likely deposited on Basin evolution a tidal flat. The late Eocene/Oligocene basal Murree beds, containing tidal bundles, indicate that a mixed Paleogene or semi-diurnal tidal system deposited the sediments and the sedimentation took place in a tide- Himalayan foreland dominated estuary. In the higher-up, the succession likely deposited in a river-dominated estuary or Tectonics in meandering rivers. In the beginning of the basin evolution, the sediments were derived from the Precambrian basement or from the metasediments/volcanic rocks possessing terrains of the south. The early and middle Eocene (54.7e41.3 Ma) succession of the embryonic foreland possibly developed from the sediments derived from the Trans-Himalayan schists and phyllites and Indus ophiolite of the north during syn-collisional stage. The detrital minerals especially the lithic fragments and the heavy minerals suggest the provenance for the late Eocene/Oligocene sequences to be from the recycled orogenic belt of the Higher Himalaya, Tethyan Himalaya and the Indus-suture zone from the north during post-collisional stage. This is also supported by the paleocurrent measurements those suggest main flows directed towards southeast, south and east with minor variations. This implies that the river system stabilized later than 41 Ma and the Higher Himalaya attained sufficient height around this time. The chemical composition of the sandstones and mudstones occurring in the early foreland basin sequences are intermediate between the active and passive continental margins and/or same as the passive continental margins. The sedimentary succession of this basin has sustained a temperature of about 200 C and undergone a burial depth of about 6 km. Ó 2012, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved.

1. Introduction

Paleogene period has been a turning point in the history of the Indian Subcontinent with the suturing of the Indian plate with the Asian plate, commencement of mountain-building events and * Tel.: þ91 542 6701355; fax: þ91 542 2369239. evolution of Himalayan foreland basin. Before the India-Asia colli- E-mail address: [email protected]. sion, the Indian Subcontinent moved about 2500 km northward starting from early Cretaceous (Gaetani and Garzanti, 1991; Peer-review under responsibility of China University of Geosciences (Beijing). Chatterjee et al., 2012). Geophysical and geological observations suggest that, the collision occurred near the equator and foreland basin evolved in the Paleogene (Kent and Muttoni, 2008; Singh et al., 2009). In recent years, the timing of India-Asia collision and Production and hosting by Elsevier related orogenesis has become a controversial issue (e.g. Aitchison

1674-9871/$ e see front matter Ó 2012, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.gsf.2012.09.002 200 B.P. Singh / Geoscience Frontiers 4 (2013) 199e212 et al., 2007, 2011; Zhang et al., 2012). The start of the collision has on facies architecture are compiled and used for deciphering been inferred at w54 Ma based on sedimentary sequences in the depositional environments. The available data on paleocurrents, Zanskar area, close to the Indus-suture zone by Gaetani and detrital minerals, heavy minerals and geochemistry are further Garzanti (1991). However, Beck et al. (1995) inferred the initial used for interpreting composition of the hinterland and influences timing of collision between 66.0 and 55.5 Ma based on the strati- of tectonics and climate on the evolution of the foreland that also graphic evidence around the suture zone in Pakistan. The concept interprets the Himalayan orogeny. Also, some geological challenges of progressive suturing (diachroneity) between Indian and Asian are highlighted for future workers in the end of this review. plates was proposed by Klootwijk et al. (1992) with its start from the western part at w55þ Ma and end in the eastern part w40 Ma. 2. Facies architecture and depositional environments Later, DeCelles et al. (2004) recorded that the time lag between the diachroneity in the orogenesis from western part, which began The early Paleogene sequences form eight architectural w52 Ma, to the central part of the Himalaya is only 2 Ma supported elements commencing with a silicified breccia facies (Fig. 2A) by geological data from Paleogene sequences of the central Hima- containing angular clasts entirely composed of silicified limestone laya (Nepal). The time of the collision in the western Himalaya is fragments derived from the underlying basement. The chert breccia also inferred as 57 1 Ma based on radiometric dating of rocks has variable thicknesses along strike. Additionally, reworked from the collision zone (Leech et al., 2005) and the initiation of the bauxite also occurs in some areas above the basement, which western Himalayan foreland is interpreted in late Paleocene contains elliptical and circular pisolites encased in ferruginous/ (57.9e54.7 Ma) as a result of the India-Asia collision based on argillaceous matrix. The breccia is followed by a siltstone or silty- stratigraphic sequences of the Jammu area, North India (Singh, shale facies (Fig. 2A) that shows thin laminae and wavy bedding. 2003). The occurrence of Cr-spinel at zone P-8 foraminifera Also, angular quartz grains occur aligned along the lamina planes assemblage in the southern Tibet indicates the onset of India-Asia and the thin lamina contains relatively finer grains than the thick collision and the initiation of the foreland basin immediately south lamina. The siltstone/silty-shale is followed by the black shale, of the India-Asia suture zone at w50 Ma (Zhu et al., 2005). Further, which possesses two to three coal seams of about 1 m thickness. Najman et al. (2010) interpreted the timing of the India-Asia colli- The black shale is followed by the argillaceous limestone (Fig. 2A) sion w50 Ma based on geological, biostratigraphic and paleomag- that is impure and contains variety of foraminifers and bivalves. netic evidences from a part of Tibet. Additionally, Wang et al. (2011) The overlying succession is composed of a cyclic packages of also considered the timing of India-Asia collision before w50 Ma green/greenish-yellow shales and argillaceous limestones (Fig. 2A). inferred on the basis of Cr-spinel and zircon ages of sediments from The limestone contains elongated gravels of intraformational origin the southern Tibet those show a change of provenance from south and often there is internal organization within the gravels, i.e. finer to north at around this time. gravels followed by coarser and vice-versa. This intraformational The Paleogene sequences in the Outer northwestern Himalaya conglomerate limestone is capped by oyster-bearing limestone that form a broad rim in lateral continuity from Pakistan (Fig. 1) con- is full of oyster shells and the shells lie parallel to the bedding sisting of early Paleogene shale and limestone-dominated and late planes. In the higher-up the limestone proportion increases and Paleogene mudstone-sandstone-containing succession. The a more regular shale-limestone intercalation occurs. In this part, geological set-up of the Paleogene sequences of the western the oyster-bearing limestone also occurs independently (Fig. 2A). Himalayan foreland including Potwar plateau and Hazara area The oxygenated facies with marl and purple shale also, pos- (Pakistan) is shown in the Table 1. The established foraminiferal sessing vertebrate fossils occur above the limestone that is followed stratigraphy (e.g. Singh, 1970; Bhatia, 1985b; Bhatia and by sandstone (lithic arenite) with erosional base. Above this horizon, Bhargava, 2006) for Paleogene sequences of the western Hima- the chocolate coloured/brown mudstone possessing pedogenic laya suggest that late Paleoceneemiddle Eocene Subathu Forma- calcrete horizons occur intercalated with the sandstones those are tion is overlain by the late middle Eoceneeearly Miocene Murree/ cross-bedded, bedded and laminated (Fig. 2B). A thick sandstone Dharamsala Group or Dagshai-Kasauli formations (Table 1)in unit (about 50 m thick) is prominent in almost all the areas where lateral continuity. This age bracket is also supported by the palae- late Paleogene sequences are exposed (Fig. 2B). This sandstone unit omagnetic data from the Jammu area and Shimla hills (e.g. shows wavy bedding, lenticular bedding, thin mud flasers, tidal Klootwijk et al., 1986; Najman et al., 1994). However, a gap of about bundles with 12e28 dominant events and ripple cross-laminae. The 10 Ma is inferred based on radiometric dating of detrital mica and laminated and ripple cross-laminated sandstones are of lithic- fission-track dating of zircon by Najman et al. (1997, 2004) and Jain wacke variety and shows bimodal distribution of quartz grains. et al. (2009). In recent years, Najman et al. (1993), Critelli and Above this sandstone unit, 5e10 m thick sandstone is intercalated Garzanti (1994), Singh and Singh (1995a, 1995b), Garzanti et al. with the brown mudstone of 12e30 m thickness intercalated with (1996), Pivnik and Wells (1996), Najman et al. (1997, 2004), the laminated siltstone (Fig. 2C). The top part of the Paleogene Najman and Garzanti (2000), Singh and Andotra (2000), Singh sequence in the western Himalaya has more sandstone and a more et al. (2000, 2004, 2007, 2009, 2010), Bera et al. (2008, 2010), regular intercalation of the sandstone and mudstone (Fig. 2D). The Carter et al. (2010) and Ravikant et al. (2011) made significant mudstone is often brownish yellow and yellow coloured and bio- contributions on the Paleogene geology of the western Himalayan turbated, but the mature pedogenic features are not observed. foreland basin. The chert breccia likely deposited by short-lived, small streams In view of the fact that the Paleogene succession of the Hima- and the clasts were derived from the hanging walls of the faults layan foreland basin preserves records of the India-Asia collision locally developed in the basement. The variable thickness of the and related Himalayan orogenesis, study of these sequences is very chert breccia facies along strike suggests that it represents a growth significant. A good data base is now available on the provenance fault. The growth fault developed in the fold-thrust belt as a result and depositional environment of the Paleogene sequences of the of compressional tectonics. The flexural subsidence was slow as western sector of the Himalayan foreland basin, still many key a result of the hard and rigid nature of the Precambrian basement issues remains to be tackled. In this review, the Paleogene (e.g. Flemings and Jordan, 1989) and thus, a shallow basin was sequences are used to interpret early evolution of the Himalayan created above this basement. Singh (2003) has interpreted this foreland basin with a focus on the Jammu area, which finds a broad breccia facies as deposited in the fault depressions developed as correlation with the Shimla hills and Dharamsala area. Here, data a result of India-Asia collision in the late Paleocene. The bauxites B.P. Singh / Geoscience Frontiers 4 (2013) 199e212 201

Figure 1. A: Map of Indian subcontinent showing tectonic subdivisions of the Himalaya (modiﬁed after Kumar and Tandon, 1985); B: Map shows distribution of the Paleogene sequences and important locations in the western Himalayan foreland.

showing alignment of the pisolites along the lamina planes and burrowing organisms, suggest a slow rate of sedimentation, and containing sedimentary structures, and the quartzose sandstone reducing conditions are demonstrated by the occurrence of pyrite and associated ferruginous silty-shale were possibly deposited in nodules and the dinocyst assemblage such as Operculodinium and ephemeral streams. The reworked bauxite formed from erosion of Thalassiphora (e.g. Sarkar and Prasad, 1998). a bauxite precursor from the cratonward side and it can be inter- The argillaceous limestone showing a micritic texture was preted as a forebulge (Singh, 2003). The coal developed from a peat possibly deposited in the low-energy coastal environments. The swamp of high vegetative density under humid-marshy conditions conglomeratic limestone above the argillaceous limestone possibly maintained by groundwater; the vegetation was only partially formed due to landward migration of the barrier bar during decomposed in the reducing conditions. The ﬁnely laminated black transgression (Singh and Andotra, 2000). The clasts for the shale was deposited in calm water condition in a lake or inner part formation of the conglomeratic limestone were derived from the of a lagoon where reducing conditions prevailed (Singh and lime hardgrounds, developed in the shoreface zone (Singh, 2012). Andotra, 2000). Thin laminae in these shales, indicating a lack of The graded unit in the limestones was deposited along the mid- 202 B.P. Singh / Geoscience Frontiers 4 (2013) 199e212

Table 1 Correlation chart of Paleogene sequences of the western Himalayan foreland (modiﬁed after Singh and Andotra, 2000).

ramp zone and the alignment of the oyster shells along the bedding regime. Trace fossils of the Scolithos assemblage were developed in planes, coupled with the preservation of hummocks at some the littoral or sub-tidal zones (Singh, 2012). In combination, the locations, is the result of storm activity during sedimentation facies association containing limestone and green/greenish-yellow (Singh and Srivastava, 2011). The siltstones coeval with graded shales represent a coastal barrier and lagoon system and the lagoon limestone units that occur in a part of the Shimla hills containing was connected to the sea by storm cuts or tidal inlets. However, hummocky cross stratification (HCS) and symmetrical ripples, Bera et al. (2008) considered Subathu Formation of Shimla hills to suggest that they also were deposited above the wave-base influ- have deposited as shelf turbidites. enced by waves and storms. The overlying finely laminated and The overlying marl facies containing thick and thin lamina clay-rich green/greenish-yellow shale was possibly deposited in couplets (possible tidal bundles) were formed as a result of the tidal a lagoon. The microbiota occurring in this shale also suggests activities over the tidal flat. The desiccation cracks and the auto- shallow marine and coastal ecosystems. The majority of the benthic brecciation indicate sufficient exposure and pedogenesis in the foraminiferal assemblage present in the argillaceous limestone upper part of the marl facies. The purple shale, with high silt content indicates a sub-tidal bathymetry that falls in zone III of Boucot and fresh to brackish-water fauna, most likely has deposited in the (1981). Furthermore, experimental studies demonstrate that most supratidal zone. The increase in the silt content and the presence of of the larger foraminifera are transported to the coastal areas by the hematite suggest additional river influx from adjoining land under tides and waves from deeper parts of the sea depending upon their oxidizing conditions. Gypsum streaks in the purple shale suggest that shape and size (Yordanova and Hohenegger, 2007). Thus, the larger gypsum precipitated from the saline groundwater during an evapo- foraminifera occurring in the limestones and shales were intro- rative phase (Singh, 2010). Wells and Gingerich (1987) considered the duced in the sediments by the waves and tides in the coastal ossiferous shale facies as on-shore pedogenized clays representing B.P. Singh / Geoscience Frontiers 4 (2013) 199e212 203 slow sedimentation in the Kotli area (Pakistan) whereas Srivastava The basal Murree beds exhibit ESE flow direction (Fig. 3) that is and Kumar (1996) interpreted the ossiferous shale in the Jammu indicated by the cross-beds present in the medium-grained sand- area as silty-claystone deposited under fluvio-deltaic conditions. stones (lithic arenites). There are three bands of lithic sandstones in The lowermost part of the Murree sandstones exhibit well- association with intraformational conglomerates, mudstones and developed tidal bundles associated with flaser and wavy bedding many calcrete bands forming a total thickness of 35 m in the basal and ripple cross-laminated sandstones also possess tidal rhythmi- part. Later on, the sand supply became more and sandstone of tes. The sandstone beds exhibiting flaser, wavy beddings and tidal about 50 m thickness deposited in the channel (medium-grained bundles deposited in sub-tidal zone, climbing ripple cross- sandstone) and on the levee (fine-grained sandstone) in a cyclic laminated sandstone units showing tidal rhythmites deposited on pattern. In this sandstone member, the channel-deposited facies the levee crest of a tide-dominated estuary and siltstones deposited are cross-bedded and planar-bedded containing oppositely in an inter-tidal area (Singh, 2000). The 12e28 tidal events suggest directed cosets (in few cases) varying in thickness from 0.2 to 0.5 m. that these strata possibly developed in a mixed or a semi-diurnal At some places in the Jammu area, these cross-beds show S20E tidal system and the tidal amplitude was too weak to reach the and N10E directed paleocurrents. The southeast directed low angle depositional site at neap stage in the semi-diurnal system. (5e7) cross-beds, probably, formed from ebb-tide whereas The upper surfaces of the sandstones preserve asymmetrical overlying cross-beds with higher inclinations (10e15) formed as (bifurcated), straight-crested, undulatory and cuspate ripples of low a result of flood-tide in a tide-dominated estuary. ripple index (RI ¼ 4.0e8.0). The climbing ripples are covered by drape The fine-grained sandstones containing ripple cross-laminae as laminae in the ripple cross-laminated sets. Climbing ripples originate internal structure and cuspate ripples on surface exhibit reac- by a combination of vertical aggradation relative to ripple migration tivation surfaces and an NNE directed cross-laminae. The late and drape laminations result from continued fall out of sediments Paleogene sequences are comprised of several cycles consisting of from suspension after ripple migration ceases (Ashley et al., 1982). intraformational conglomerate, medium- and fine-grained sand- The climbing ripple sets occurring in the late Paleogene sequences of stone, siltstone, and mudstone in the lower part above the basal the Jammu area suggest high rate of net deposition and vertical succession. The paleocurrent directions are mainly SSE in the cross- aggradation as well as horizontal migration of the ripple crest. bedded sandstones and SE-NE in the ripple cross-laminated sand- The mudstones of the Lower Murree and Dagshai formations stones those show ripple sheet migration. were deposited during the slackwater period in the supratidal zone Furthermore, the late Paleogene sequences show sets of trough- on estuarine flood-plains. Pedogenic calcretes have developed shaped cross-beds in the middle part with cosets thickness varying either on the estuarine or fluvial flood-plains (Singh et al., 2009). from 0.50 to 0.75 m, and flow directions S20W and S15W. Fine- The Upper Murree sequences either have deposited in the river- grained flaggy sandstone (3.0 m thick) preserves starved and dominated estuaries or meandering rivers and similar is the case cuspate ripples of 4e6 cm sizes. The flow direction varies from SSE for the Kasauli Formation (e.g. Najman et al., 1993; Singh and Singh, to SSW in these along this horizon. Up-section, the coset thickness 1995a). The mudstones possibly have deposited during the slack- of the cross-beds varies from 0.5 to 1.0 m with sigmoidal tidal water period in the supratidal zone or on river flood-plains. Also, bundles showing SE-SW directed foresets. The cross-bedded basal part of the Dagshai Formation in the Shimla hills is thought to sandstones mainly reveal southerly flow and ripple-laminated have deposited under the marine influence by Bera et al. (2008). sandstones demonstrate SSE flow directions towards top of the Additionally, the surfaces of ripple-laminated sandstones in the sequence. The paleocurrent map (Fig. 3) indicates dominantly Murree Group are weakly bioturbated and mark the presence of southeast flow direction from the Rajouri Road section in the basal small Thalassinoides trace fossils. These sandstones showing late Paleogene sequences whereas SSE with some northerly modes bimodality of the grain size suggest a mixed environment where up-section. The SE and SW flow directions are prominent with river-derived sediments were redistributed and deposited under some northerly modes in the Murree sequences exposed along the tidal influence in the estuary. The siltstone unit is moderately to Kalakot-Jammu road section. Near Treyath village, the paleocurrent highly bioturbated at places and contains Chondrites, Planolites, directions are southwesterly and northeasterly in the basal part and Imbrichnus and Scolithos as important trace fossils, and these trace SW-SE up-section. North of Udhampur town, the late Paleogene fossils developed in secondary channels in the inter-tidal area sequences show northerly and southerly flow directions with (Sudan et al., 2002). Also, trace fossils of Scolithos assemblage easterly and westerly subordinate modes and southerly directions suggesting coastal sedimentation have been earlier reported by dominate. Additionally, in the east of Dharamsala town, the basal Singh (1978) from the Paleogene sequences of the Shimla hills. late Paleogene sequences show southerly and southeasterly paleocurrents (Fig. 3). In an earlier study, Raiverman et al. (1983) also 3. Paleocurrents indicated southerly paleocurrents from the Dharamsala area. In lateral continuity in the Shimla hills, southeasterly and easterly The Himalayan foreland basin developed on the Precambrian flow directions are recorded. Although some deviation, but basement in between the Himalayan orogen and the Indian craton, southerly flow again confirms paleocurrents earlier shown by and erosion of the Precambrian basement locally deposited chert Srivastava and Casshyap (1983). Therefore, paleocurrents from late breccia entirely composed of the underlying basement fragments. Paleogene sequences in different sub-basins indicate that the Black shale and limnic coal were deposited in swamps of a coastal channels flowed towards southeast, south and southwest with plain. The Subathu sediments deposited on a marine ramp created negative relief. Furthermore, the hinterland was towards north, due to the subsidence related changing littoral and sub-tidal northwest and northeast with positive relief that supplied the settings similar to the Persian Gulf. Miall (1995) has suggested sediments in the foreland basin. that oldest sediment of the peripheral foreland basins, indicating sediment starvation, is deepwater. Although no evidence of the 4. Detrital minerals and provenance deepwater sedimentation is present in the Paleogene sequences of the northwestern Himalaya, the evidence of sediment starvation is Provenance and sediments distribution paths are identified on present that is represented by the reworked carbonates in the the basis of light and heavy minerals including rock fragments in lower part and more regular carbonate intercalations in the higher- sedimentary rocks. In the Hazara Syntaxis (Pakistan), Bossart and up of the Subathu Formation. Ottiger (1989) included late Paleoceneemiddle Eocene Balakot 204 B.P. Singh / Geoscience Frontiers 4 (2013) 199e212

Formation in their Murree Supergroup and (Critelli and Garzanti, The bauxite in the basal part of the Subathu Formation is of 1994) performed detailed provenance study of them. According reworked origin and formed from a bauxite precursor that origi- to Critelli and Garzanti (1994), the quartzo-lithic composition of the nated when India was close to the equator. Singh (2003) considered Murree redbeds testiﬁes to a collision orogen provenance. this bauxite precursor as a forebulge at the initiation of the According to them, volcanic and carbonate rock fragments are Himalayan foreland and the present reworked bauxite deposited by abundant in the Lutetian sandstones. Minor quantities of chert and the erosion of the forebulge. Presumably, the foredeep was NS serpentine schist, indicating contribution from uplifted subduction trending and the forebulge was in the south-southeast. The basal complex sources, as well as siltstone, shale and limestone grains, Subathu sequences also contain siltstone/silty-shale possessing are invariably present (Critelli and Garzanti, 1994). Detrital modes wavy laminae and is very rich in angular to sub-angular quartz of sandstones and southwestward progradation of Tertiary clastic grains followed by muscovite that occur with their longer axis wedges both testify to provenance from the proto-Himalayan chain parallel to the laminae cemented with carbonate/ferruginous located to the north, and uplifted since the very ﬁrst stages of the cement. The heavy minerals present in the bauxite and the siltstone India/Asia continental collision at the end of the Paleocene (Critelli are staurolite, sillimanite, rutile and ilmenite and partly altered and Garzanti, 1994). ilmenite and magnetite. The heavy minerals in the basal detrital

Figure 2. A: Lithocolumn showing stratigraphic architecture of the Subathu Formation; B: Lithocolumn presenting facies architecture of the lower part of the Murree Group; C: Lithocolumn showing facies distribution and associated sedimentary structures of the middle part of the Murree Group; D: Lithocolumn showing architectural elements and individual facies of the upper part of the Murree Group. B.P. Singh / Geoscience Frontiers 4 (2013) 199e212 205

Figure 2. (Continued).

bauxite and siltstone suggest a metasedimentary and volcanic derived from the Higher Himalaya after its exhumation (Najman provenance from south and well-rounded rutile suggests its recy- et al., 2000). Also, Bera et al. (2008) and Jain et al. (2009) sug- cling from sediments/metasediments may be from the Aravalli gested derivation of sediments during the sedimentation of the Mountains. The quartzose composition of the siltstone is indicative Subathu Formation (late Paleoceneemiddle Eocene) from the of its maturity and recycling from a sedimentary/metasedimentary Himalaya based on Sm-Nd isotopic values and fission-track zircon source. The volcanic source for the precursor bauxite is confirmed ages respectively, while Ravikant et al. (2011) correlated the U-Pb based on trace elements and REE concentrations in the Jammu ages of the detrital zircon grains occurring in the Paleogene bauxite (Singh et al., 2005, 2009). In the overlying succession, Singh sequences as derived from the Tethyan Himalaya. The Tethyan et al. (2000) reported detrital illite, chlorite and sepiolite from the sedimentary succession, the chief provenance for the early Paleo- Paleogene mudrocks of the Jammu area (Jammu and Kashmir gene sequences, ranging in age from Proterozoic to Eocene State). Earlier, Bhattacharya (1970) and Raiverman and Suresh deposited on the Tethyan margin of India (Fuchs, 1982; Gaetani (1997) reported detrital illite and chlorite from the lower Tertiary et al., 1985; Gaetani and Garzanti, 1991). It (Tethyan succession) mudrocks of the Dharamsala area and the Shimla hills (Himachal contains limestone, sandstone, shale and subordinate volcanic Pradesh) in the lateral continuity. Detrital illite and chlorite are rocks. denudation product of metamorphic and magmatic rocks (Irion and The late Paleogene sandstones are composed of monocrystalline Zolmer, 1990). Therefore, the presence of detrital illite and chlorite quartz, feldspar, muscovite, biotite, chlorite, iron minerals and lithic in the Paleogene mudrocks of the western Himalayan foreland, fragments (Singh, 1996). In Q-F-L and Qm-F-Lt plots (after India suggests their derivation either from the Trans-Himalayan Dickinson et al., 1983), the Murree sandstones occupy recycled and schists, phyllites and granites or from the Higher Himalayan Crys- quartzose recycled orogenic provenance, respectively (Figs. 4 and tallines and the Indus-suture zone. However, Sm-Nd isotopic values 5). This is mainly because of their quartzo-lithic composition. The of the Paleogene sediments from the Himalayan foreland basin feldspars are orthoclase as well as plagioclases and rock fragments suggest erosion of mixed sources including the suture zone during are phyllite, quartzite, chert, siltstone, mudstone, lime-clasts and late Paleocene and middle Oligocene and younger sediments were volcanic-clasts. Significantly, few Murree sandstones contain 206 B.P. Singh / Geoscience Frontiers 4 (2013) 199e212

Figure 5. Qm-F-Lt diagram for the Murree Group of sandstones (after Dickinson et al., 1983; Singh, 1996). Qm represents monocrystalline quartz, F represents feldspar and Lt represents lithic fragments including polycrystalline quartz.

Figure 3. Outline map of the Paleogene sequences exhibits paleocurrent directions by arrows. Note dominant southerly and southeasterly flow directions. Paleogene sandstones, is characterized by a domal arrangement in Zanskar with the highest-grade rocks in the core and the lowest- grade along the margin (Staubli, 1989; Vance and Harris, 1999). It serpentinite rock fragments. The sedimentary rock fragments (Higher Himalaya) dominantly contains quartzite, carbonaceous constitute 28.5%e62.5%, metamorphic fragments 33.3%e71.4% and phyllite, crystalline limestone and felsic schist followed by por- igneous rock fragments less than 9.5% (Fig. 6). The significant aspect phyroblastic gneiss that shows alternating bands of quartz-feldspar of the rock fragments distribution is the decreasing trend of and biotite. Also, psammitic gneiss with quartzite, garnetiferous volcanic and metamorphic rock fragments towards the higher-up. mica schist, porphyroblastic gneiss and greyish brown gneiss The mudstones are also composed of detrital clay minerals within intercalated with kyanite bands occur associated with tourmaline- which scattered fine quartz grains occur. The metamorphic rock bearing granite and biotite granite (Thakur et al., 1990; Singh et al., fragments were derived from the metamorphic provenance such as 2004). the Higher Himalaya and the serpentinite as well as volcanic rock The abundance of volcanic rock fragments, chrome spinels, and fragments either came from the Indus-suture-zone or from the serpentine schist grains has been recorded in the upper Subathu Tethyan Himalaya in the Murree sandstones. Furthermore, the stratigraphic unit in the Shimla hills. Both rock fragment types and sedimentary rock fragments either were supplied by the prove- Cr-spinel composition attest to a northern ophiolitic source and do nance in the north or included in the sands during channel cutting not favour any contribution from the Deccan Traps (Najman and and their migration. The Higher Himalaya, the key source of the late Garzanti, 2000). In contrast to the Murree sandstones, the

Figure 6. Triangular plot shows composition of the Murree sandstones in terms of Figure 4. Q-F-L diagram for the Murree Group of sandstones (after Dickinson et al., lithic fragments. Lv represents volcanic rock fragments, Lm represents metamorphic 1983; Singh, 1996). Q represents quartz, F represents feldspar and L represents lithic rock fragments and Ls represents sedimentary rock fragments. Note the richness of fragments. these sandstones in metamorphic and sedimentary rock fragments. B.P. Singh / Geoscience Frontiers 4 (2013) 199e212 207

Dharamsala and Dagshai sandstones rarely contain volcanic rock the mudstone. Similar to the Murree sandstones of the Hazara area fragments. However, they are dominated by the mica-schist frag- (e.g. Critelli and Garzanti, 1994; Garzanti et al., 1996) and the ments over the sedimentary rock fragments. Further, they are Jammu area, the lithic particles and heavy minerals of the late richer in quartz than the Murree sandstones and monocrystalline Paleogene sandstones in Himachal Pradesh, India (e.g. Chaudhri, quartz dominates over the other constituents in them. Detrital 1975) indicate their derivation from northerly low- and medium- modes show that the Dagshai Formation was dominantly derived grade metamorphic provenance. The poor presence of volcanic from very low grade metamorphic rocks, with predominant met- rock fragments in the Dharamsala and Dagshai sandstones is either apelitic lithic grains, a significant component of sedimentary due to their absence in the source terrain or due to absence of the material, and rare volcanic and ophiolitic detritus (Najman and detritus from the Indus-suture zone in those sub-basins or their Garzanti, 2000). The Kasauli Formation was dominantly derived decomposition during transportation. Detritus composition of early from low grade metamorphic detritus with the dominance of Himalayan Foreland basin sediments from Pakistan to Nepal and phyllite, quartz-mica grains and garnets (Najman and Garzanti, Bangladesh is consistent with progressively later closer of Neo- 2000). Thus, the main Dagshai and Kasauli Formations were tethys along the suture, from latest Paleocene time in the west to derived from the proto-Himalayan chain similar to the present day Eocene time or even later in the east (Najman and Garzanti, 2000). Higher Himalaya. This suggests that the general paleoslope was southerly and Heavy minerals, zircon, tourmaline, garnet, epidote and stau- southeasterly when the late Paleogene sediments accumulated in rolite dominate in the late Paleogene sandstones. The rod-shaped the Himalayan Foreland, and the sediments were mainly derived zircon grains in a fine-size range are rounded to subrounded. The from the rising Himalaya in the north. tourmaline grains are mostly blue and pink having sub-angular to subrounded shapes. Brownish-red garnet with subrounded shape 5. Geochemistry and provenance occurs along with epidote. The staurolite is a marker mineral in the late Paleogene sequences of the Himalayan foreland from Pakistan Major and trace elements provide insight into broader compo- to Nepal and this was supplied from the staurolite-grade meta- sition of the rock types and they help in determining provenance, morphic rocks of the Higher Himalaya. In the heavy mineral plot of weathering, tectonic setting and diagenesis (Bhatia, 1983, 1985a,b; Nechaev and Isphording (1993), the heavy minerals of the Hima- Bhatia and Crook, 1986; Whitmore et al., 2004). layan foreland basin occupy the same field as mature passive The Paleogene sandstones and mudrocks have been studied for margin (Singh et al., 2004)(Fig. 7). This means that the heavy major and trace elements both in the Jammu area and the Shimla mineral suits of the mature passive margins and foreland basins are hills. The Murree sandstones are rich in SiO2 and Al2O3, where the same. w(SiO2) ranges from 78.34% to 82.71% and w(Al2O3) ranges from Thick (0.3e0.5 cm) silt/very fine sand laminae are intercalated 4.01% to 10.18%. The w(Fe2O3) ranges from 1.74% to 3.42% and with thin (0.05e0.2 cm) mud laminae in the ripple cross- w(TiO2) ranges from 0.07% to 0.50%. w(CaO) constituting the laminated siltstone also. The siltstones have a particle size range carbonate cement occurs between 2.0% and 4.13% and w(MgO) of 0.2e0.02 mm. Angular to sub-angular quartz grains of the silt- ranging from 0.22% to 0.99% is less than CaO (Singh, 1996). Occur- size range are interspersed within ferruginous matrix/cement in ring within the range of 0.92%e4.10%, w(K2O) is more than w(Na2O) with few exceptions. In w(Fe2O3 þ MgO) vs. w(TiO2) and w(Fe2O3 þ MgO) vs. w(Al2O3)/w(SiO2) plots (after Bhatia, 1983), the Murree sandstones occupy passive margin field with some deviation (Fig. 8). Further, they occupy an area between the active margin and the passive margin in the w(Fe2O3 þ MgO) vs. w(K2O)/w(Na2O) and the w(Fe2O3 þ MgO) vs. w(Al2O3)/w(CaO þ Na2O) (Singh, 1996) (Fig. 8). Titanium is resistant to weathering and is regarded as an oxide that suggests about the source of the sediments and parent material of the soils (Young and Nesbitt, 1998). The low concen- tration of w(TiO2) (0.07%e0.50%) in the Murree sandstones suggests that the source of the sandstones has been poor in Ti- bearing rocks such as basic and ultrabasic rocks. Similar to sandstones, the Paleogene mudrocks of the Jammu area are also rich in SiO2 and Al2O3, where w(SiO2) ranges from 56.24% to 70.19% and w(Al2O3) ranges from 9.37% to 14.28%. w(TiO2) is within the range of 0.10%e0.72%. w(Fe2O3) ranging from 0.67% to 5.90% is more than w(FeO) except black and greenish yellow shales of the Subathu Formation. Further, w(CaO) is more than w(MgO), and w(K2O) is more than w(Na2O) with few exceptions (e.g. Singh et al., 2000). Trace element Zr occurs in a range of 35 to 107 ppm, Rb ranges from 126 to 142 ppm, Ba ranges from 72 to 112 ppm and Sr ranges from 17 to 45 ppm. The other trace elements such as V, Cr, Co and Ni show their concentrations less than 30 ppm in the mudrocks of the Jammu area. In the Maturity Index (phyllosilicates vs. quartz þ feldspars) vs. lg(K2O/Na2O), Paleogene mudrocks of the Jammu area occupy a field between the phyllo- Figure 7. Triangular plot showing distribution of heavy minerals in the Himalayan tectic and phyllic of Bhatia (1985a)(Fig. 9). The position of the foreland basin (after Nechaev and Isphording, 1993; Singh et al., 2004). Note that heavy Paleogene mudrocks in between the phyllotectic (containing both minerals of mature passive margins and foreland basins occupy the same field. feldspars and clays in subequal percentages) and phyllic field MT ¼ Total content of epidote and garnet. GM ¼ Total content of tourmaline, staurolite, zircon, kyanite, sillimanite and zoisite. MF ¼ Total content of hornblende, pyroxene and (containing large amount of clays) is mainly because they are olivine. intermediate in terms of the presence of clays. The intermediate 208 B.P. Singh / Geoscience Frontiers 4 (2013) 199e212

Figure 8. Bivariate plots based on major oxides for the sandstones of the Murree Group (after Bhatia, 1983; Singh, 1996). Aeoceanic island arc, Becontinental island arc, CeActive continental margin, DePassive continental margin, FeForeland basin. percentage of clays suggests that the mudrocks are derived from a chemical composition that is intermediate between the active and metamorphic and sedimentary sources (Bhatia, 1985a; Singh et al., passive margin sediments. 2000). Also, the low contents of Cr, Co and Ni suggest that the Najman and Garzanti (2000) found high values of Ni and Cr in provenance has been dominated by the felsic rocks. Thus, it is the Subathu shales in comparison to Dagshai and Kasauli concluded that the foreland basin sediments are mainly derived mudstones and attributed this difference as the change in sources from felsic igneous, metamorphic and sedimentary rocks and show of them. According to them (Najman and Garzanti, 2000) higher nickel and chrome content in the Subathu Formation compared to the Dagshai and Kasauli Formations confirm that the maficto ultramafic input to the basin during Subathu sedimentation was reduced by Dagshai deposition. The abundance of Ni and Cr varies erratically within sediments suites derived from recent magmatic arc and recycled orogen rocks, but they show increasing trend with decreasing grain size in Tertiary rocks. This increase in abundance probably reflects adsorption of Ni and Cr by phyllosilicates such as chlorite (Whitmore et al., 2004; Garzanti et al., 2011). As the Sub- athu shales are rich in clays with finer particle sizes, abundance of Ni and Cr in them seems more likely as compared to Dagshai and Kasauli mudstones. It is immensely important to carry out geochemistry of the mudrocks of the Paleogene sequences of the Himalayan foreland basin in a systematic way in view of the erratic behaviour of the elements in a modern foreland basin (e.g. Whitmore et al., 2004) and their felsic-dominated provenance in the modern Himalayan foreland basins (e.g. Verma et al., 2012).

6. Basin evolution

Late Paleocene witnessed a major transgression on the Indian subcontinent (Mathur, 1983). The driving force for this transgression appears related to tectonics rather than the climate as late Figure 9. Maturity index vs. lg(K2O/Na2O) plot for the Paleogene mudrocks (after Bhatia, 1985a; Singh et al., 2000). AeTectic field, BePhyllotectic field, CePhyllic field, Paleocene was cooler than Eocene. At the initial stage of the fore- DeForeland basin. land basin development the basinal subsidence was shallow B.P. Singh / Geoscience Frontiers 4 (2013) 199e212 209 coupled with slow rate of sedimentation and sediment starvation. detrital zircon U-Pb, and fission-track dating show that provenance This may be related to hard and rigid rheology of the Precambrian of the Paleogene sedimentary rocks exposed in the Makran region basement occurring below the Subathu Formation (Singh, 2003). of southern Iran and the Katawaz basin of Pakistan is consistent The alignment of the pisolites in the bauxite suggests their depo- with a source from the nascent western Himalaya and associated sition under the influence of unidirectional current, may be in magmatic arc (Carter et al., 2010). Further the U-Pb ages of the ephemeral streams. The occurrence of small intensity wavy detrital zircon grains occurring in the Paleogene sequences of the bedding in the siltstone beds suggests that these deposited on western Himalayan foreland basin, India are suggested to have a wave-dominated coast. The overlying shales are thought to be derived from the Tethyan Himalaya (Ravikant et al., 2011). The U-Pb deposited in coastal lagoons and the limestone packages deposited zircon ages of the CretaceousePaleocene sedimentary rocks of on barriers by storm reworking of the earlier formed barriers (Singh Nepal suggests their derivation from the Archeaneearly Protero- and Andotra, 2000). The limestones containing intraclasts from zoic terrain and an abrupt influx of CambrianeOrdovician and precursor limestone hardgrounds also suggest sediment starvation middle to late Proterozoic zircons during Eocene indicates the and shallow subsidence of the basin (Singh, 2012). The purple onset of erosion of Tethyan rocks in the nascent Himalayan thrust calcareous shale containing fresh-water and brackish-water belt. An increase in the late Proterozoic zircons in fluvial lithar- vertebrates was deposited in an oxygenated environment with enites of the lower Miocene Dumri Formation of Nepal signals more influence of the river system at this stage (Wells and initial erosion of Higher Himalayan protoliths (DeCelles et al., Gingerich, 1987; Srivastava and Kumar, 1996; Bhatia, 2000; 2004). Further in central Himalaya (Nepal), definite evidence of Kumar, 2000; Blas et al., 2004). This implies that the progradation derivation of sediments from the Asian plate is recorded before began in the basin during latest middle Eocene (w41 Ma). Latest 50 Ma (Zhu et al., 2005; Wang et al., 2011) and in eastern Himalayan middle Eocene is also considered as the marine to continental foreland sequences (Bengal basin, Bangladesh), the detrital sedi- transition and sequence boundary in the western Himalayan fore- ments derived from the Himalayan orogen were recorded to be of land basin (Kumar et al., 2008; Singh et al., 2010). The latest middle younger than 38 Ma (Najman et al., 2008). These imply that the Eocene regression might be either forced by the tectonics and/or India-Asia collision took place before 50 Ma, subsequently proto- climate because this was the beginning of cooling and start of the Himalaya took its shape during early Eocene and the main Hima- nucleation of Antarctica ice sheet. The overlying arenaceous silici- layan chain was evolved during late Eocene/Oligocene supplying clastic deposits younger than latest middle Eocene (later than considerable amount of arenaceous sediments to the foreland 41 Ma) suggests that the sediment supply increased from the basin, and there appears some time lag between the initial Hima- hinterland coupled with more flexural subsidence and higher rate layan-derived sediments to the western Himalayan foreland basin of sedimentation in the depositional basin. The sandstone deposi- and the eastern Himalayan foreland basin (Fig. 10). tion event coincides with proto-MCT formation at about 35 Ma (e.g. Peripheral foreland basins are characterized by basin-wide Le Fort, 1996) or initial exhumation of the Higher Himalayan rocks unconformities at the sites of forebulges (Miall, 1995). If one w40 2 Ma in the western Himalaya (e.g. Thöni et al., 2012) considers the radiometric age data suggesting 10 Ma gap between (Fig. 10). the Subathu Formation and the Dagshai Formation by Najman et al. However, Bera et al. (2008) suggest derivation of sediments (1997, 2004) and Jain et al. (2009), then the site of unconformity can from the nascent Himalaya based on Sm-Nd isotopic values during be considered as a forebulge. This also suggests that the Subathu the sedimentation of the late Paleoceneemiddle Eocene Subathu sequences must have experienced up warping before the Dagshai Formation in India and Jain et al. (2009) argue that the initial sedimentation began. Also, the new basin must have developed in foreland basin sediments were derived both from the Asian plate the north slightly away from the Subathu basin. But in most of the and the Indian plate along the suture zone. Sediment petrography, areas, Subathu succession is directly overlain by the Dagshai or Murree sequences with or without erosional contacts. It is utmost important to date the Paleogene sequences of the Jammu area, which looks more continuous with less tectonic complications before arriving at definite conclusion on this regional unconformity. The late EoceneeOligocene succession with the presence of tidal bundles in the basal parts shows that they deposited in the tide-dominated estuaries followed by river-dominated estuaries. This implies that the coastal system became stable with the occurrence of perennial rivers during late Eocene and the hinterland got sufficient relief at this stage. Ren (1981) has inferred that the Tibetan Plateau was about 1.0 km high around 40 Ma and the uplift of the Tibetan Plateau to its present elevation is suggested to have taken place around 15 Ma (Spicer et al., 2003). Similarly, Raiverman (2006) has argued that central Himalayan chain started gaining gentle uplift after 50 Ma. The stabilization of the river system depositing arenaceous sediments around 35 Ma in the Himalayan foreland basin shows that the hinterland (Himalaya) started attaining height during this period and even Tibetan plateau was sufficiently high during this period of time (Fig. 10). The northern tip of India was in the subtropical climatic belt when the calcrete bearing sequences of the Lower Murree and Dagshai Formation formed (Singh et al., 2009). The brown mudstones, with Figure 10. Hypothetical cartoon exhibiting positions of various tectonic units and the moderate chemical index of alteration (CIA ¼ 70e82 in Singh and foreland during the Paleogene. A: Early Paleogene situation without much uplift in the hinterland; B: Late Paleogene situation with added uplift in the hinterland due to rising Lee, 2007), in the Murree and Dagshai sequences most likely of the Higher Himalaya. developed under the influence of moderate weathering governed 210 B.P. Singh / Geoscience Frontiers 4 (2013) 199e212 by subtropical climatic conditions. The wet subtropical climatic entire extent (in space and time) of the Paleogene succession of the condition was intervened by the dry subtropical climatic conditions Himalayan foreland basin can provide us geological evidences for reflected by the occurrence of moderately mature pedogenic cal- Eocene global warming and Oligocene cooling. Additionally, pale- cretes developed in the semiarid to arid climates. The individual osols occurring in the Paleogene sequences of a part of the western calcrete profiles might have developed within a time span of Himalayan foreland basin have been correlated with the northward 10e130 kyr (e.g. Candy et al., 2004). drift of India and related long-term climatic changes (Singh et al., The general domination of the southerly flow in the late 2007, 2009). On analogy, paleosols from other areas of the Paleogene sequences is the result of the southerly flowing river or Himalayan foreland basin can be investigated in detail and corre- system of rivers and thus, indicating a southerly paleoslope. The lated for long-term climatic shifts. subordinate northerly and northeasterly modes associated with the tidal bundles demonstrate their generation through tides from 7. Conclusions the sea that was south and southeast of the Himalayan chain. Chappell and Woodroffe (1997) have suggested that morpho- The Paleogene succession of the Himalayan foreland basin is dynamics of macrotidal estuaries in northern Australia are forced significant because it preserves the early history of the Himalayan by strong tidal flows through out the year and a fluvial flood water orogenesis besides, containing evidences for long-term climatic flow for a relatively shorter period during monsoon. Thus, the changes and hinterland/foreland tectonics. In the western Hima- sedimentation in the late Paleogene foreland basin was strongly layan foreland basin, the early Paleogene chert breccia and bauxite governed by the tides annually before the monsoon period. In view formed at the onset of the basin formation and the sediments were of the assertion that the Himalaya and the Tibetan plateau were derived either from the basement or from the metasediments/ high during Eocene, one can assume that the monsoon began weathered basalt occurring cratonward. The overlying early Eocene during Eocene on the Indian subcontinent even if that was weak. packages of shales and carbonates deposited on wave- and storm- Paleogene coals of the Jammu area are dominated by the vitri- dominated coasts and the siliciclastic detritus was supplied either fl 0 nite maceral and the average vitrinite re ectance (Rmax) comes to from the Trans-Himalayan metasediments or from the magmatic w1.7% (Singh and Singh, 1995b). Further, Illite Crystallinity Index of rocks present in the orogenic belt. At this stage, the source terrain the Paleogene mudrocks shows the range of values those are in was low-lying that was responsible for low and fine-grained (clay) transition between the highest-grade diagenetic and anchimeta- supply of the sediments and also, marked by the quiescence periods morphic zones (Najman et al., 2004). These values of the vitrinite in siliciclastics supply enabling the carbonates precipitation. The reflectance and illite crystallinity index suggest that the basin has carbonates containing larger foraminifera and trace fossils of the undergone a burial depth of about 6 km and sustained a diagenetic Skolithos assemblage developed during transgression on barrier temperature of about 200 C. bars and shales deposited in inner part of lagoons. These sequences The evidence of sedimentation during Paleogene period is also also show sediment starvation and reworking. The middle Eocene present in the Ganga Plain in northern India. Drilling data produced strata developed in a mixed or a semi-diurnal tidal system. In the by the Oil and Natural Gas Commission suggests presence of the late Paleogene sequences of the western Himalayan foreland, the late PaleoceneeEocene and younger succession below the recent paleocurrent directions were southerly and southeasterly in an Ganga alluvium (Raiverman et al., 1996). Paleogene terrigenous overall estuarine/riverine environment. Paleoslope reconstruction sediment accumulation was generally low in the Indian Ocean, with indicates the presence of continent in the north and ocean in the significant accumulation in only limited areas such as Madagascar south-southern part during the development of the western rise and southwest Indian continental margin, and turbidite sedi- Himalayan foreland. The occurrence of Cr-spinel in the sandstones mentation in the Bengal Fan started at around 12 Ma where silici- suggests that they have been derived from the Indus-suture zone clastic sediments derived from the Himalaya progressively and their quartzo-lithic nature suggests that they have been accumulated (Davis et al., 1995). Also, seismic mapping, thermo- derived from the recycled orogenic provenance of the Himalaya. chronological analyses of detrital mineral grains, heavy mineral and This is also reflected by the presence of staurolite and other heavy petrographic studies, and isotopic analyses of bulk rocks show that minerals, the U-Pb zircon ages and Sm-Nd isotopes. The chemical the Neogene rocks of the northern Bangladesh are predominantly compositions of foreland sandstones and mudstones are interme- Himalayan-derived, with a subordinate arc-derived input possibly diate between the active and passive continental margins and/or from the Paleogene Indo-Burman Ranges as well as the Trans- analogous to passive continental margins. The main Himalayan Himalaya (Najman et al., 2012). Before Miocene and start of the chain was uplifted at least w41 Ma ago that acted as a hinterland foreland basin in the late Paleocene, the Himalayan-derived sedi- and supplied the detritus to the foreland basin from the north. ments began depositing at least from early Eocene (w54 Ma) in the Since then the Himalayan chain is continuously supplying the Subathu basin, as coastal off-lap in the Murree/Dharamsala/Dag- sediments to the foreland basin which progressively shifted its shai-Kasauli basin, and Ganga plain with southerly shifting sedi- depocentre towards south with the progressively filling of the ment accumulation depocentre. basin. Chemical behaviour of the elements in a modern foreland basin of Australia is largely erratic and sediments are commonly derived Acknowledgements from a felsic-dominated provenance in the modern Himalayan foreland basins (Whitmore et al., 2004; Verma et al., 2012). My involvement in the study of the Paleogene sequences of the Therefore, geochemical characterisation of the Paleogene sedi- western Himalayan foreland basin is for nearly two decades and ments of the Himalayan foreland basin should be a point of focus in during this period, I got support from many of my students and future studies. Himalayan foreland basin sequences are marked by friends. I also acknowledge the help rendered by various organi- unconformities of shorter or longer durations (Pivnik and Wells, zations, especially Department of Science and Technology, New 1996). Thus, dating of the well-studied and undisturbed succes- Delhi for funding at least three research projects to me. Dr. B. Tessier sions of the Himalayan foreland basin in a systematic manner can is thanked for reading earlier version of a part of this manuscript be done for acquiring information about the timings and durations and suggesting modifications that improved it many-fold. I am of the regional unconformities. Furthermore, a systematic study thankful to Prof. M. Santosh for inviting me to submit this paper and including stable oxygen, carbon and strontium isotopes for the anonymous reviewers for suggesting fruitful modifications. B.P. Singh / Geoscience Frontiers 4 (2013) 199e212 211

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