The Palaeobofanist, 28·29: 389-401, 1981.

PALAEOGENE PALYNOSTRATIGRAPHY OF SIMLA HILLS

H. P. SINGH Birbal Sahni Institute of Palaeobotany, 53, University Road, Lucknow-226007,

ABSTRACT

The Palaeogene succession of Simla Hills consists of Subathu, and formations in ascending order of stratigraphy. The palynostratigraphical information developed from the marine sequence of Subathu sediments throws light on the dating potential of the assemblages and also on the distributional pattern of various palyno• morphs. Dependable palynological parameters in effecting correlation of various sections of the formation have been discussed. Reflections on the palynological spectra across the Subathu-Dagshai boundary and in the Kasauli Formation have been made. Key-words- Palynology, Subathu Formation, Dagshai Formation, Kasauli For• mation, Palaeogene (India).

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INTRODUCTION mates and environment of deposi• tion. 4. To explore the possibility of finding a is tomainreviewobjectinofdetailthe presentthe palyno•paper palynological datum line which may THElogical information developed from help in the correlation of different the Palaeogene rocks of , stratigraphical horizons. particularly from Simla Hills and also to 5. To establish reliable indices for the discuss the further scope of work in this delimitation and recognition of fine and adjoining areas. Systematic palyno• stratigraphical horizons. logical investigations of the Palaeogene 6. To select key/guide fossils with well succession in Simla Hills were started established ranges, both in space and by the author in 1971 in order to develop time. palynological information from these rocks 7. Finally to establish the correlative with the following objectives: value of the various biostratigraphical 1. To obtain palynofossils from various zones in the entire outcrop area. stratigraphical levels of the Palaeogene The above objectives of study were succession. selected as a sequel to the confused state 2. To resolve the age and stratigraphical of stratigraphy of the Palaeogene sediment~ position of the different formations in Simla Hills which consist of the' based primarily on the evidence pro• (i) Subathu Formation, (ii) Dagshai Forma• vided by palynological fossils. tion, and (iii) Kasauli Formation in ascend• 3. To find out the possible affinity of ing order of stratigraphy. The correlation of the palynological fossils which might these sediments has been a difficult task help in reconstruction of palaeoc1i- because of the absence or impoverished 3Sa 390 THE PALAEOBOTANIST

recovery of plant and animal fossils to• and distantly located sections between gether with their unsatisfactory record of Baroti and along the -Simla general distribution. The absence of Highway (Text-fig. 2). The most striking dependable lithomarkers, because of enor• feature of the present study has been that mous lateral variation of lithofacies on a the lithological boundaries, with a few ex• regional scale, particularly in the Subathu ceptions, coincide with the palynological Formation, has been another hurdle in boundaries in addition to the fairly sharp effecting precise correlation of various and easily distinguishable change in the com• stratigraphical horizons. Lastly the natural position of palynoflora from one cenozone order of superposition has been disturbed to another. The palynozones have been by the tectonic activity during the great delimited on the basis of first appearance, Himalayan uplift creating complexities to acme and decline of the various taxonomic the understanding of this stratal sequence. entities. Singh and Khanna (1978) and The selection of the Palaeogene suc• Khanna and Singh (1980) have worked cession, as the main target of geological out the palaeoecological significance of and palynological study, has been guided Pediasfrum and Subathua in the Subathu by the occurrence of oiliferous horizon in Formation. Besides comparing the Subathu the Subathu Formation. Rocks of similar assemblage with the known Indian and age are producing oil in the Potwar region extra-Indian comparable assemblages from of Pakistan. The present study of the the homotaxial rocks (Singh & Khanna, Subathu sediments has revealed beyond manuscript), environmental influence on doubt that they represent marginal facies the distribution of biofacies in the Subathu in the area of study and as such can be Formation based on the distribution of considered potentially important for the various species of microplanktons indicative generation of hydrocarbons (Singh et aI., of salinity, depth and distance from the 1973). shorelines has been worked out by Khanna The recovery of dinoflagellate-rich assem• and Singh (1981). Palynologically one major blages alongwith Some other palynomorphs transgression of the sea in the lower part complexes from the Subathu Formation in of the Subathu Formation followed by a the Kalka-Simla area paved a way for the westward regression in the upper part or establishment of palynological zonation of during the close of Subathu sedimentation the. Subathu Formation (Singh et al., 1979) has been postulated. at. Its type area, the Subathu town, Simla The Dagshai Formation conformably Hills. On the basis of quantitative and overlies the Subathu Formation and has qualitative analysis of the palynomorph been investigated palynologically above the assemblages, it has been possible to esta• passage bed level at 3 different localities, blish stratigraphical ranges of significant viz., Dagshai, Dharmpur and Kumarhatti. species which have wide geographical and The dinoflagellate rich assemblage of the restricted vertical distribution resulting in shallow marine Subathu Formation vanishes the establishment of 8 cenozones and 2 completely in the lower part of the Dagshai subzones. Now these zones can be reliably Formation and is replaced by a distinct used as a stratigraphical tool for dating coastal type spore pollen assemblage (Singh and correlation of the Subathu sedimentary & Khanna, 1980). This palynological Succession. Singh and khanna (1980) have evidence has been used in demarcating the also worked out the distributional pattern boundary between the calcareous Subathu of palynoflora within this formation and Formation and non-calcareous Dagshai have also related some palynological dis• Formation. The Dagshai assemblage, similarities in relation to the changing though impoverished qualitatively, is domi• environment of deposition. Khanna et al. nated by gymnospermous pollen grains Qn press) have established geological credibi• along with pteridophytic and fungal spores. lity of the various palynological zones when Palmidites and Couperipollis are also the they correlated 8 stratigraphically measured striking constituents of the assemblage.

TEXT-FIG. 1 - Shows a scheme of palynological zonation of the Subathu Formation in Simla Hills. The distribution of differeQt ceQozoQes has been plotted a~ainst the lithoIog. SINGH - PALAEOGENE PALYNOSTRATlGRAPHY OF SIMLA HILLS 391

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'):EXT-FIG. 1 392 THE PALAEOBOTANIST

In spite of the fact that the rock samples the three formations constitute a thick have been collected extensively from the sequence of Palaeogene sediments in Simla Dagshai Formation, recovery of palyno• Hills. Chaudhri (1968) put forward a morphs has been discouraging because of classification of the Palaeogene succession the prevalence of largely oxidizing environ• in the area proposing the following strati• ment of deposition with high redexon ~raphic order (after making some modifica• potential. As such attempts to establish a tIOns). palynological succession here have not been fruitful. However, rock samples from some AGE HIMALAYAN FOOT-HILLS stratigraphical levels of Dagshai Formation Lower Miocene to Kasauli Formation which are now being studied from the Upper Oligocene (fluvio-deltaic) Surla-Jalal Section ( area) have also confirmed the earlier observations that the Lower Oligocene Dagshai Formation assemblage is rich in bisaccate pol1en grains to Upper Eocene (coastal-transitional) together with the complete absence of Upper Eocene to Subathu Formation microplanktons. Upper Palaeocene (shallow marine) The Dagshai Formation conformably grades into the KasauliFormation. Most .••••••••••••... Unconformity ...... •. of the Kasauli samples collected at the Pre-Tertiary rocks boundary level proved barren. A few samples collected from Koti and Barog The Subathu Formation is mainly charac• yielded a poor and ill preserved assemblage terised by the predominance of calcareous being characterised by the virtual absence 01ive green (oily looking), pale-olive grey, of Inaperturopollenites and by the presence black and purple shales with subordinate of Polypodiaceasporites, colporate and lenticular bands of limestones, siltstones monocolpate pollen grains alongwith spongy and occasional sandstones. The latter two spicules. It is very likely that continued are . mostly restricted to the uppermost efforts to recover palynomorphs from ceratin portIOn of the Subathu Formation. The favourable lithologies like shales and silt• siltstones are generally green in colour. stones representing the Dagshai and Kasauli A white quartzite zone general1y marks formations may provide an opportunity at a the top of this formation. later date to establish palynological succes• The overlying Dagshai sediments are sion as has been done in the case of Subathu invariably non-calcareous and are charac• Formation. terised by having purple facies only. The purple facies have medium to fine grained LITHOSTRATIGRAPHICAL SUCCESSION sandstones, mottled shales/siltstones and claystones. The former two exhibit massive The term 'Subathu' was first used by development and often contain haematitic Medlicott (1864) for a conformable sequence nodules. of Palaeogene sediments exposed in the The Kasa uli Formation overlies the Simla Hills, after the town Subathu, situated Dagshai Formation conformably and is southwest of Simla. The original term distinguished by having massive but micace• included Subathu, Dagshai and Kasauli ous sandstones mostly of arenaceous nature stages. Later in 1879, the term 'Sirmur with minor intercalations of purple and Series' was given to the stratal sequence olive green shales. by Medlicott himself and the term' Subathu ' was restricted to its lowermost marine AREA OF INVESTlGATlONS sequence. The Subathu sediments occur along a The present palynostratigraphical review narrow discontinuous belt in the extra• of the Palaeogene sediments is confined peninsular region of the Indian subcontinent to a part of Simla Hills covering approxi• from Jammu in the west to the west of mately 288 sq km area between Lat. 30°50' Dehradun in the east. In Simla Hills, a?d. Long. 76°55' and 77°05' E falling they are conformably overlain by the wlthm the Survey of India Toposheet no. Dagshai sediments which, in turn, are 53F/1 and 53B/13. All the geological sec• overlain by the Kasauli succession. All tions examined, measured and described SINGH-PALAEOGENE PALYNOSTRATIGRAPHY OF SIMLA HILLS 393

are exposed along the Kalka-Simla Highway (in term of population percentage) of the between Baroti and Barog, viz., Koti, Jabli, assemblage. Mathur (1963, 1964, 1965) Dharmpur A, B, C, Dagshai and Kumar• and Salujha et al. (1969) reported the occur• hatti excepting the type locality of Subathu. rence of palynomorphs in the Subathu Exact locality, stratigraphic position and sediments and carried out preliminary lithological details of the samples have investigations. been recorded and published by Khanna The gross palynofloral features of the et at. (in press) and hence are not repeated Subathu Formation are characterised by the here. abundance of hystrichosphaerids together During the course of field study it was with other dinoflagellate cysts in the lower observed that the type locality, Subathu, part of the formation, whereas the upper exposes the best developed section of the part of the formation is characterised formation right from its base to top in by the trilete-rich spore assemblage or Kuthar Nala. In fact, this is the only abundance of members of the family section which exposes the base of the Thalassiphoraceae thriving in very shallow Subathu Formation and, therefore, has water and low saline conditions (Singh & been regarded as the standard section. Khanna, 1980). On the basis of further However, the contact of the Subathu detailed analysis of palynodata by Singh Formation with the underlying Simla Slates et al. (1978) seven cenozones and one is clearly unconformable. In an adjoining barren zone were established. Each ceno• section of the same area faulted contact zone, excepting the barren zone, is charac• between the Subathus and Simla Slates has terised by the abundance of a single genus been observed. The Subathus unconform• with its one or more species together ably overlie a variety of Pre-Tertiary rocks with the occurrence of a few restricted of different ages. Their upper contact with species which form distinct assemblage the overlying Dagshais has also been debat• zones. able. It is beyond the scope of this paper The salient features of the cenozones to discuss different views of the geologists. (Text-fig. 1) in ascending order of strati• However, I concur with Chaudhri (1968) graphy are enumerated below together with that no where the Subathus and the remarks on their relationship with different Dagshais show any discordance but the lithologies: former conformably grades into the latter. Similarly the Dagshais grades into the 1. Cyefonephelium spp. Cenozone Kasaulis and the discordance suggested by Krishnan (1956) has not been confirmed by This cenozone is about 15·75 m thick. Cbaudhri (1968). The lithology consists of alternations of shaly limestone, limestone, carbonaceous PALY OLOGICAL SUCCESSION shales or coal bands. The basal lime• stone member of the Subathu Section SUBATHU FORMATION shows an unconformable tectonic contact with the Simla Slates. The black shale Among tbe palynological constituents of facies form the upper contact of this the Subathu assemblage (43 genera & 106 cenozone. species), representatives of the Thallophytes This cenozone is characterized by the predominate. The class Dinophyceae re• presence and abundance of Cyclonephelium presented by a variety of dinoflagellates is eompaetum, C. exuberans, C. divarieatum predominantly distributed at various strati• and C. spinetum. The other important graphical levels. Sporadic occurrences of constituents of this cenozone belong to Pediastrum, a member of Chlorophyceae the following genera: Tenua, Triehodinium, has been noteworthy. The spores and Oligosphaeridium, C/eistosphaeridium, Hystri• pollen taxa representing pteridophytes, ehoko/poma and Homotryblium. The dis• gymnosperms and angiosperms are rather tribution of 3 species, viz., Achmosphaera poorly represented. The fungal spores and tridaety/ites, Impectosphaeridium rugosum bodies are very rare in distribution. In and T. koemmelbeini is restricted to this short the plant microremains of continental cenozone together with the virtual absenc •• origin constitute an average of 10 per cent of land derived elements, to> ~\0

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TEXT-FIG.2 _ Shows a scheme of palynostratigraphical correlation of the different sections of the Subathu Formation in Simla Hills. The distribution of different sections has been shown in the area map. SINGH - PALAEOGENE PALYNOSTRATIGRAPHY OF SIMLA HILLS 395

2. Barren Zone first time in this zone. This cenozone lacks the presence of any restricted species. The Barren Zone consists of 105 m thick black shale facies (Subathu Section) 6. Cordosphaeridium multispinosum Ceno• and is totally devoid of palynological zone fossils. This facies was deposited under foul environment which is not conducive A 30 m thick sequence of monotonous for the preservation of organisms. The shales varying from grey to olive green in black shale facies grades into the greenish colour (Subathu Section) is identified by grey shales marking the upper contact of the acme period of Cordosphaeridium multi• this zone. spinosum. The needle shales lying over the splintery shales of Hexagonifera spp. 3. Cleistosphaeridium spp. Cenozone Cenozone denote the lower limit of this cenozone. Though it is difficult to re• This cenozone is about 30 m thick cognize the upper contact because of the (Subathu Section) and consists of greenish absence of a lithomarker unit, the appre• grey, calcareous splintery shales which may ciable fall in the percentage of Cordospha• change to pale olive green shale facies in eridium multispinosum from 42 per cent to other sections. It is overlain by grey 2 per cent together with the marked increase splintery shales which register the abundance in the percentage of Subathua sahnii de• of Homotryblium. marcates palynological distinction between The abundant occurrence of Cleistosphae• the two. The other striking constituents ridium diversispinosum, C. disjunctum, Tenua of the assemblage are Cordosphaeridium kutharensis and T. simlaensis, the first jibrospinosum, C. exilimurum, Subathua appearance of Hystrichokolpoma indica, H. sahnii, Todisporites spp. Lygodiumsporites palaeocenica and Todisporites dagshaiensis barogensis and Thalassiphora velata along alongwith the restricted distribution of H. with some other forms. Species of res• indica and H. palaeocenica are Some of the tricted distribution have not been observed salient features of this cenozone. in this cenozone.

4. Homotryblium Cenozone 7. Subathua sahnii Cenozone

This cenozone is also approximately The principle lithounit of this cenozone 30 m thick having grey shales and is consists of arenaceous, pale olive green identified by the dominance of Homotry• shales with siltstone bands. The upper blium tenuispinosum and H. abbreviatum. limit of this cenozone is marked by a Besides the occurrence of some other signi• purple shale facies. The characteristic ficant dinoflagellate species, Hystrichosphae• species of this cenozone are Subathua sahnii, ridium tubiferum, H. daenei, H. simplicis• Cyclonephelium indicum and Cleistosphae• pinosum and H. asterium are restricted to ridium parvum. The latter mentioned this zone while H. aesterium, H. granulatum, species along with Heteraulacacysta ?leptalea Hexagonifera reticulata, H. vermiculata, H. and Thalassiphora pelagica are restricted sahii and Thalassiphora velata make their to this cenozone. Additionally the presence first appearance. of Oligosphaeridium complex, Cleistosphae• ridium diversispinosum, C. disjunctum, Homo• 5. Hexagonifera spp. Cenozone tryblium tenuispinosum, Hystrichosphaeri• dium granulatum, Hexagonifera chlamydata The lithounits of this cenozone consist along with some other species, which show of olive green, calcareous splintery shales a declining trend in percentage, seems to with alternations of limestone sands. The be a characteristic feature of this cenozone. salient features of this cenozone are the This cenozone has been considered to be dominant occurrence of Hexagonifera re• one of the most important zones in this ticulata, H. vermiculata, H. chlamydata study as its upper limit denotes a sharp and H. sahii. Two species, viz., Oligos• change in the environment of deposition. phaeridium dharmpurensis and Lycopodium• The dinoflagellate rich assemblage registers sporites singhii have been observed for the a crash fall and is replaced by a trilete-rich 396 THE PALAEOBOTANIST spore assemblage. The total absence of expressed diverse opinions in regard to the dinoflagellates has been used as a reliable age of the Subathus. However, the gap parameter in demarcating the top of of divergence was appreciably narrowed Subathu Formation. down by the works of D3.tta et al. (1955), Bhandari and Aggarwal (1966) and Chaudhri 8. Todisporites spp. Cenozone (1968) who believe that the Subathus range from Upper Palaeocene to Upper Eocene in The arenaceous pale olive green shales age. The Kakara Series, which is exposed with siltstone bands are intercahted with near the Kakara-Ch1pla villages, has been purple shales. Lenses of sandstone are shown to be Palaeocene in age on the quite common. The upper limit of the basis of stratigraphical as well as palae• Subathu Formltion is marked by the de• ontologic3.1 basis (Srikantia & Bhargava, velopment of quartzose s1ndstone. 1967). Palynologic3.1 studies of these sedi• This cenozone exhibits a mixed type of ments have not been done as yet which, assemblage. The samples collected from of course, are likely to ascertain the the basal part of this cenozone contain a proposed age. In short, the palynological few specimens of dinoflagellate cysts be• evidence supported by other related longing to the following forms: Homotry• studies confirm that the Subathus range blium tenuispinosum, Hexagonijera reticulata, from Upper Palaeocene to Upper Eocene Hystrichosphaeridium granulatum, Cordo• in age. On the basis of a detailed paly• sphaeridum multispinosum, Subathua sahnii nologic3.1 zon Ition scheme prepared by and Thalassiphora velata whereas its upper Singh et al. (1979), it ha'> been possible to part is rich in trilete spores (at some places date the different cenozones of the Subathu in gymnospermic pJllen grains) along with Formltion as follows: the complete absence of dinofh.gellates• 1. Upper Palaeocene-Lower Eocene so very characteristic of the brackish w~ter (represented by the base of Cyc!one• environment of deposition. Significant phelium spp. Cenozone to the top of species of this cenozone are: Todisporites Homotryblium spp. Cenozone). dagshaiensis, Lycopodiumsporites pattmo• 2. Middle Eocene (between the base of rensis, L. crossii, L. singhii, Interapuncti• Hexagonifera spp. Cenozone to the sporites intrapunctus, Lygodiumsporites bar• base of Todisporites spp. Cenozone. goensis, Podocarpidites marginatus, P. 3. Upper Eocene (the remaining Todis• kumarhattiensis, Cyathidites cooksonii, etc. porites spp. Cenozone). The mixed type assemblage of this ceno• zone indicates the onset of coastal transi• ENVIRONMENT OF DEPOSITION tional environment. In addition to the institution of above It is a well documented fact that the cenozones, two Subzones represented by Subathu sediments were deposited in a Pediastrum spp. Subzone and Hystricho• shallow linear epicontinental sea opening kolpoma Subzone have been formally de• north-westwards. Bhandari and Agarwal signated. Though their occurrence is purely (1966) postulated the presence of parallel local in the Jabli section, each one of them to subparallel ridges on the floor of the separately identifies a stratum of 30 m basin because of which isolated basinal thick. condition developed leading to different environment of depositions in different AGE parts of the basin. On the basis of fluctua• ting sea-land level changes, Chaudhri (1976) The age of the Subathu Form1tion has suggested two regressive and transgressive been discussed in detail by Khanna and phases of the sea during the Subathu Singh (in Press). Palynological basis have sedimentation cycle. Raiverman (1964) been the main theme of the work though opined that the environment of deposi• data from other disciplines, viz., the order of tion of Subathu Form3.tion varied from superposition and palaeontology have been marine to brackish water. Palynological taken into consideration. Pilgrim and West studies carried out by Singh and Khanna (1928), Cox (1931), Yokes (1937), Singh (1980) have demonstrated that the Subathu (1952), Mandwal (1959) and Pascoe (1964) sediments were deposited under the trans- SINGH - PALAEOGENE PALYNOSTRATIGRAPHY OF SIMLA HILLS 397

gressive phase of the sea followed by Of the six sections studied, viz., Koti, regression towards the close of Subathu Jabli, Dharmpur 'B', Dagsh'li, Kumarhatti sedimentation, contrary to the opinion and Subathu, the first five fall on the held by Chaudhri (1976). Palynologically, Kalka-Simla Highway and the last one observations of Raiverman (1964) have been lies at a distance in the northwest direction. confirmed as the rock sequence, encompassed As per 10c3.tion of these sections, Koti and between the Cyclonephelium spp. Cenozone Jabli represent the south-western margin, and Cordosphaeridium multispinosum spp. Dagsh'li and Kum::trhatti represent the Cenozone, represents true shallow marine north-eastern margin whereas Subathu and environment whereas the stratigraphical in• Dharmpur 'B' represent deeper and perhaps terval between the Subathua sahnii Cenozone the central part of the basin. Palynological till to the base of Todisporites spp. Cenozone composition of the marginal sections though conforms to brackish water environment. closely comparable exhibits variation mainly The upper horizon of Todisporites spp. on 3 counts: (i) minor variations reflected Cenozone is supposed to have been by the abundance of Some common long deposited under fresh water environment. ranging species, (ii) local development of These distinction have been made on the a particular morphotype, and (iii) occur• basis of field studies and wide occurrence rence of stratigraphically insignificant of such forms which inhabi t marine and morphotypes. Also the marginal assem• brackish water environment (Khanna & blages contain such forms which prefer Singh, 1981). The absence of microplank• to inhabit mesohaline and relatively shallow ton cysts and the presence of land derived water environment, viz., Cleistosphaeridium elements in the upper horizons of Subathu diversispinosum, Cyclonephelium exuberans sediments has been attributed to the estab• and members of the family Thalassipho• lishment of fresh water environment. raceae. It has been observed that Cleisto• sphaeridium disjunctum and Cyclonephelium RELATIONSHIP OF BIOFACIES WITH compactum flourish in norm'll saline and LITHOFACIES deeper condition of deposition. The Hexa• gonifera spp. Cenozone occurs in highly Evolution, undoubtedly, has been one calcareous facies showing thereby its as• of the major factors controlling the quali• sociation with the hypersaline environment. tative spectrum of the past palynofloras. Cordosphaeridium multispinosum is eury• Of late, it has been observed that, besides haline and thus it is uniformly distributed palaeolatitudes, the influence of environment in all the sections studied so far. It has has been appreciable in modifying com• been observed that the total microplankton position of the assemblages both in terms ratio is 97: 3 in the lower part of the of quantity and quality. Critical observa• Subathu Formation which runs in an inverse tions of Staplin (1961), Wall (1965), Scull proportion towards its top where the as• et al. (1966), Williams (1970) and Sarjeant semblage consists of spore-pollen and land (1974) paved a way towards the recognition derived elements (Text-fig. 3). Palyno• and application of this dimension in inter• logical analysis of the Subathu Formation pretation of dissimilar biofacies as related at its north-eastern and central parts of to the changing pattern of environment. the basin throws light on the bathymetric Singh and Khanna (1980) observed the and variable conditions of environment of selective distribution of various palyno• deposition. Modification in composition of morph complexes in the sediments of the assemblages has been minor to pro• Subathu Formation and later on selected nounced depending upon the interaction of 6 measured sections to confirm the obser• the variable environment controlling the vations and interpretations. The results development of biofacies. of the study have been embodied in a paper (Khanna & Singh, 1981) which deals with DAGSHAI FORMATION the environmental influence on the distri• bution of biofacies in the Subathu Forma• In some localities like Kumarhatti and tion. The details of this interesting study Dharmpur the top of the Subathu and are difficult to record here yet an attempt the base of the Dagshai formations are is made to disCIlSSits salient features. intercalated by a 10 m thick passage bed. w \0 00

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TEXT-FIG, 3 - Shows the microplankton/spore.pollen ratio occurring in the different sections of Subathu Formation, Simla Hills, SINGH - PALAEOGENE PALYNOSTRA TIGRAPBY OF SIMLA HILLS 399

Palynological composition of this bed Couperipollis, Palmidites, Palmaepollenites, reveals that the genus Pediastrum consti• Tricolpites and Verrutrico/pites. Specimens tutes about 90 per cent of the assemblage, of Pediastrum and fungal spores have also spores and pollen grains being relegated been identified. The qualitative and quanti• to a meagre of 10 per cent or sometimes tative changes in the distributional pattern even less. Bhatia and Mathur (1965) re• of the palynoflora in the Dagshai Formation ported the occurrence of Bulinus? and seem to be in response to the change in Planorbis, the two fresh water gastropods, the environment of deposition from brackish in the same beds indicating the appearance to fresh water (Text-fig. 4). Additionally, of fresh water conditions during the close palynological data in hand do not support of Subathu sediments. the earlier views that the Dagshai sediments The Dagshai assemblage is identified were deposited in brackish water environ• chiefly by the absence of microplanktons ment. On the contrary, the presence of (marine biota) and by the presence of pteri• Palmidites, Palmaepollenifes together with dophytic, gymnospermic and angiospermic trilete spores tend to indicate coastal tran• spores and pollen grains. The significant sitional environment for the Dagshai For• constituents of the assemblage are: Lygo• mation. diumsporites, Lycopodiumsporites, Todispo• It has not been possible to attempt a rites, Intrapunctisporis, Cyathidites, Podocar• detailed palynological scheme of zonation pidites, lnaperturopollenites, Laricoidites, as it has been done in the case of Subathu

CYCLONEPHELIUM-- SPPSPPSPPSPPSPP -• CLEISTOSPHAERIOIUMSUBATHUA SPP - POOOCARPIDITESHOMOTRYBLIUMTODISPORITESHEXAGONIFERACOROOSPHAERIOIUMSPP SPP -- -

INAPERTUROPOLLENITESSPICULESPOLLENsppSPP •ISPPSPPI•sppSPP I• - PALMAEPOLLENITESTRICOLPITESPOLYPOOIACEAESPORITESSPONGEPEOIASTRUMCOUPERIPOLLISVERRUTRICOLPITESMONOPORATESPP POLLENFUNGAL SPORESCOLPORATE - • • • • PALMIDITES SPP • SUBATHU OAGSHAr KASAULI FORMATION FORMATION FORMATION

INDEX

Ei I i II : j i II o~. '0, 10 30 "0 SOlo ...... till thon 1%

TEXT-FIG. 4 - Shows the distribution of stratigraphically significant palynomorphs in the Subathu, Dagshai and Kasauli formations of Simla Hills. 400 THE PALAEOBOTANlST

Formation, obviously for lack of sufficient base upwards thereby indicating one palynological data from the largely un• major tramgression of the Palaeocene• fossiliferous rock samples collected from Eocene sea in the lower part of the Dagshai Formation. Recently the t he formation followed by a north• author has succeeded in locating some more westward regression towards the close productive horizons in the Dagshai sedi• of Subathu sedimentation. ments of Surla-Jalal Section near Banethi 3. The Subathu assemblage is mostly in Nahan region. A diversified assemblage identified by the dominance of of well·preserved bisaccate pollen grains dinoflagellate cysts excepting in the of gymnospermic origin occurring in case of some top horizons thereby good numbers. has been recovered. and confirming the earlier view that the is being studied morphotaxonomlcally. Subathu sediments were deposited Further location of productive horizons under shallow marine condition. from the stratigraphically located samples On the basis of restricted distribution is necessary before any significance can and variable abundance of various paly• be attached to the present data in nomorphs in different stratigraphical hori• hand. zons seven cenozones alongwith one barren zone have been recognized. The selective KASAULI FORMATION association and distribution of the paly• nomorphs have been ascribed to the chang• The overlying Kasauli sediments are ing environment of dep~sition. largely unfossiliferous. Attempts for the Biostratigraphical evidences and the evi• recovery of palynomorphs have mostly ~en~es from other complimentary disciplines proved abortive. The samples colle~ted mdlcate an Upper Palaeocene to Lower from Koti yielded meagre palynological Eoc~ne ~ge to the stratigraphical column information which has been considered and rangmg m between Cyclonephelium spp. discussed here for the worth it deserves. The Cenozone and Homotryblium spp. Cenozone. Kasauli assemblage consists of the follow• The stratigraphical interval from Hexa• ing constituents: spongy spicules (27 %), gonifera spp. Cenozone to Subathua sahnii angiospermic pollen grain rep.rese~ted by Cenozone represents Middle Eocene age Palmaepol/enites spp., Couper/pol/Is spp., whereas the Todisporites spp. Cenozone some monoporate and colporate pollen corresponds to Upper Eocene age. grains (24 %). Podocarpidites. spp. (17 ~), A. close similarity in palynological suc• fungal spores (17 %) .a~d Pedwstrum (9 %) cessIOn between Jabli and Kumarhatti constitute the remallllllg components of sections indicates marginal environment of the assemblage. the basin whereas dissimilarities of local importance are apparent in the assemblages CONCLUSIONS of . Subathu and Dharmpur 'B' sections whlc~ a.re located away from the margin. The lithostratigraphical and palynostra• QualitatIve and quantitative analysis of tigraphical investigat~ons of .the Subathu, palynomorphs allow distinction of marine, Dagshai and Kasaull. formatIOns. have re• near-shore and coastal transitional zones. sulted in the followmg conclusIOns: Spores and pollen grains, though scantily 1. The Subathu Formation unconform• represented, indicate the prevalence of sub• ably overlies the pre-Tertiary sediments tropical to. tropicaJ climate during the exhibiting variable lower cont~ct due Su~athu sedimentatIOn. A major palyno• to tectonic disturbances and, In turn, logical change occurs across the Subathu• is conformably overlain by the Dagshai Dagshai boundary.. This sharp change is Formation which grades into the r~l~ted to changes III the depositional con• Kasauli Formation. ditIOns from shallow marine to coastal• 2. The Subathu Formation represents one tran~itiona. Finally, palynological infor• major transgression foll

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