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, India ABSTRACT The Palaeogene succession of Simla Hills consists of Subathu, Dagshai and Kasauli 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). f!Ir:lm ~ 'llT it~ 'fiT<'i't;rlfUll'Pl!~(fil<ll(tt ~ fuQ: f!Ir:lm ~ if; it~ ~ if~, ~ ~ ~ m,-~~ mi't@-";jilf if ~ ~ I ~ ~m if; ~ ~ ~ ~ lfUll'Pl!~ ~ t{'IFqlff if; ~ 'lm'r• f.nm:ur ~ fm:rir q (1'lio(filif'~",1 if; fild (Olieli if' ~ '1( '+iT wmr ~ ~ I m,~ if; ~ l#f 'llT ~ Sflfrf1rrcrrn if; fuQ:f.nh: ~ ritnr 'roIll"Tf<r<p 'lfufl+1;IT 'llT ~ f.t;1:rrl'fllT ~ I ~-~ IDm if; qn: ~ 'fittToft m,-t{'~ if If(f1fl1lTfCf'li-~ '1( '+iT wmr:sr<'lT l'fllT ~ I 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 Himachal Pradesh, 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 Barog along the Kalka-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 0 ~ .~t-....~ ~ §...~ ; ..t..c -~ ::: 0 C " SUBATHU ~ FORMATIONi· t-~:) .8 ~.t~ ie ~I:;~~ 'i': ~ ~i~~iS ~ ~ : UI'"III ."'lAIOCINI - L~II IOCIIII ••••OOLl IOCINI !IOCU•••••• IUt , i " --- t" !~i I'f: ~ 1 I Ii! CYCLONEPHELIUM COMPACTUM _. __ .._- CYCLONEPHELIUM EXUBERANS '-'- - CYCLONEPHELIUM SPINETUM 1-- ..........•• -_.. CYCLONEPHELIUM DIVARICATUM •..........- TENUA SIMLAENSIS '- TENUA KUTHARENSIS - TRICHODINIUM HIRSUTUM ACHILLEODINIUM PALAEOCENICUS ACHMOSPHAERA TRtDACTYLITES IMPLETOSPHAERIDluM KROEMMELBEINI .-•...... CLEISTOSPHAERIDIUM DIVERSISPINOSUM • CLEISTOSPHAERIDIUM DISJUNCTUM • HYSTRICHOKOLPOMA PALAEOCENICA •••• HYSTRICHOKOLPOMA INDICA -.'- -L-.. - -_ . - ----_ .. '):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 (Nahan 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