Early Cambrian trace fossils from the Tal Formation of the Mussoorie Syncline, India RESEARCH COMMUNICATIONS. Meera Tiwari* and S. K.

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1 36. Chen, W. P. and Molnar, P., Focal depths of intracontinental and intraplate earthquakes and their implications for the thermal and mechanical properties of the lithosphere. J. Geophys. Res., 1983, 88, Chen, W. P., A brief update on the focal depths of intracontinental earthquakes and their correlations with heat flow and tectonic age. Seismol. Res. Lett., 1988, 59, Kim, W. Y., Modelling short period crustal phases at regional distances for the seismic source parameter inversion. Phys. Earth Planet. Int., 1987, 47, McCue, K. and Leiba, M. M., Australia s deepest known earthquake. Seismol. Res. Lett., 1993, 64, Arvidsson, R., Wahlstrom, R. and Kulhanek, O., Deep crustal earthquakes in the southern Baltic shield. Geophys. J. Int., 1992, 108, Nyblade, A. A. and Langston, C. A., East African Earthquakes below 20 km and their implications for crustal structure. Geophys. J. Int., 1995, 121, Kiyoshi, I., Regional variations of the cut-off depth of seismicity in the crust and their relation to heat flow and large inland earthquakes. J. Phys. Earth, 1990, 38, Maasha, N. and Molnar, P., Earthquakes fault parameters and tectonics in Africa. J. Geophys. Res., 1972, 77, Simpson, F., Fluid trapping at the brittle ductile transition reexamined. Geofluids, 2001, 1, Manglik, A. and Singh, R. N., Thermomechanical structure of the central Indian shield: Constraints from deep crustal seismicity. Curr. Sci., 2002, 82, Johnston, A. C., Seismotectonic interpretation and conclusions from SCR seismicity database, Chapt. IV, California EPRI, 1994, p Gupta, H. K., Mandal, P. and Rastogi, B. K., How long will triggered earthquakes at Koyna, India continue? Curr. Sci., 2002, 82, ACKNOWLEDGEMENTS. We thank Dr V. P. Dimri, Director, NGRI for according permission to publish this work and to Dr H. K. Gupta (former Director) for his encouragement during this study. We also thank Dr Heinrich Brasse for his useful comments, which helped to improve the manuscript. We thank the anonymous reviewer for constructive suggestions. marks and burrows. The present assemblage could represent the middle to upper part of the Early Cambrian. Keywords: Cambrian, Dimorphichnus, Diplichnites, Monomorphichnus, trace fossils. IN the western Lesser Himalaya, the Tal Formation is an important lithostratigraphic unit of the Neoproterozoic Cambrian sequence (Blaini Krol Tal succession), which consists mainly of black shales, chert, siltstone and Quartzite. Our study area is located on the Mussoorie Dhanaulti road section, exactly on the 0 km milestone of Batagad. It shows exposures of huge Quartzite with sandstone shale intercalations and represents the lowermost member (Quartzite member) of Upper Tal Formation (Figure 1). Trace fossils reported and described here are preserved within these sand shale intercalations. It is well known that trace fossils present in the Neoproterozoic Cambrian boundary sections in the worldwide localities are generally well-preserved and well-diversified 1 7, and the boundary is defined by the first appearance of the trace fossil, Treptichnus pedum 5. Recent studies in the Mussoorie hills of Uttaranchal have revealed several trace fossil-bearing sections, especially in the arenaceous sandstone shale beds of the Upper Tal Quartzite member. The best preserved section is along the Mussoorie Dhanaulti road section. The traces are mostly in the form of burrows and tracks along with scratch marks and are identified mainly as Monomorphichnus isp, Dimorphichnus Received 6 October 2005; revised accepted 21 October 2005 Early Cambrian trace fossils from the Tal Formation of the Mussoorie Syncline, India Meera Tiwari* and S. K. Parcha Wadia Institute of Himalayan Geology, 33 General Mahadeo Singh Road, Dehradun , India A significant assemblage of trace fossils is presently described from the lowermost Quartzite member of Upper Tal Formation, in addition to earlier described trace fossils from Himachal Pradesh. The most common trace fossils described here are Monomorphichnus isp, Dimorphichnus isp., Dimorphichnus isp A, Diplichnites isp A, Planolites isp, Skolithos isp, Merostomichnites isp,?neonereites isp, along with various scratch *For correspondence. ( mtiwari@wihg.res.in) Figure 1. Field photograph showing fossiliferous horizon. CURRENT SCIENCE, VOL. 90, NO. 1, 10 JANUARY

2 isp., Dimorphichnus isp A, Diplichnites isp A, Planolites isp, Skolithos isp, Merostomichnites isp, and?neonereites isp. The trails occur as grooves and ridges with positive epirelief. Earlier, after detailed work in the Krol Tal belt of the Lesser Himalaya, various researchers have recorded several trace fossils in addition to mineralized fossils and organic-walled microfossils (e.g. small shelly fossils, trilobites, acritarchs and cyanobacteria) of the Neoproterozoic Cambrian boundary interval from the Tal Formation exposed in Mussoorie, Garhwal, Korgai, Nigalidhar and Nainital synclines At the present level, where mineralized fossils and organic-walled microfossils are not reported, this trace fossil assemblage is proved to be significant and can be used in identifying the Early Cambrian succession. The youngest litho unit of the Krol Group, the Tal Formation was described and named by Medlicott 27. This formation was subsequently mapped in four separate areas of Himachal and Uttaranchal in four major synclines, namely Nigalidhar, Korgai, Mussoorie and Garhwal, and classified as Lower and Upper Tal, separated by a disconformity 28,29. Bhargava 30, however, divided Tal Formation into Lower, Middle and Upper, where the Middle Tal includes Lower Tal of Auden 29. Shanker 31 further divided Lower Tal Formation into four members, i.e. Chert member, Argillaceous member, Arenaceous member, Calcareous member, and Upper Tal Formation into Quartzite member respectively. Singh 32 studied the Mussoorie Jabarkhet toll barrier succession in detail and divided the lithological succession into eight lithounits. Units A to D consist of black shales, chert and phosphorite corresponding to Chert and Argillaceous members of Shanker 31. Unit E consists of grey-coloured streaky siltstone, and thin sand layers alternating with mud layers corresponding to Arenaceous member. Unit F consists of purple sandy shale, corresponding to Calcareous member. Units G and H correspond to Quartzite member 31 and Masket member 33. Unit G is made up of purple sandstone and sand/shale intercalations and unit H is typically white-coloured, coarse-grained Quartzite. Lithological unit of Tal sediments from Mussoorie to Jabarkhet Toll barrier 31,32 : Upper Tal Quartzite H Coarse-grained member Quartzite *G Purple sandstone with greenish shaly streaks Calcareous F Purple sandy shale member Lower Tal Arenaceous E Streaky siltstone member Argillaceous D Grey to black member calcareous shale Chert C Sandy shales with member black calcareous bands B Dark coloured shale with sandy intercalations A Black shale 114 The trace fossil-bearing horizon, described presently, is exposed exactly on the 0 km milestone at Batagad near Jabarkhet toll barrier in the Mussoorie Dhanaulti road section (Figure 2 a, b), located at N : E and an altitude of 6585 ft asl. The studied section is characterized by the presence of quartz arenite with thinly layered micaceous shale which is sometimes nodular and compact. The trace fossil horizon occurs within an outcrop of ~1 m thickness, at the bedding plane of finely laminated siltstone and nodular, compact sandy shale and falls within the unit G of Singh 32. Diversified assemblages of trace fossils have been reported in the Arenaceous member 10. It was presumed that these trace fossils were produced by macrobenthonic community, and Skolithos dominate over the crawling traces of arthropod Diplichnites, Merostomichnites, Dimorphichnus, Monomorphichnus, Protichnites and Tasmanadia. Trace fossils Paleophycus and Skolithos along with arthropod traces, are reported from Quartzite member of Upper Tal Formation 11,34,52, and the Calcareous member which contains a rich assemblage of brachiopods also shows the presence of trace fossils 18,35. The traces are mostly in the nature of burrows, tracks and trails along with some scratch marks. The trails occur as grooves and ridges with positive epirelief on jointed and fractured micaceous sandstone, but where they occur as clustered pit-like impressions, it is difficult to interpret whether these impressions represent negative epirelief or hyporelief. Systematic ichnology Ichnogenus Monomorphichnus Crimes, 1970 Monomorphichnus isp. (Figure 3 a, c, g (A)) Description: A set of isolated, slightly curved sigmoidal ridges repeated laterally. The ridges vary in length from 1 to 2 cm and are about 1 2 mm wide and nearly 1.5 mm apart from one another. Repository ref.: WIHG/A/1571, 1572, 1573a. Remarks: The present species differs from Monomorphichnus bilineatus, Crimes 1970 in the pattern, shape and size of ridges. It differs from Monomorphichnus species from the Spiti valley and also the species from Kashmir valley in nature, pattern and size of ridges 36,37. Ichnogenus: Dimorphichnus Seilacher, 1955 Dimorphichnus isp. (Figure 3 e) Description: Paired, parallel series of asymmetrical wedge and rib-shaped markings of varying size. Each individual CURRENT SCIENCE, VOL. 90, NO. 1, 10 JANUARY 2006

3 a b Figure 2. a, Geological map of the area modified after Banerjee and Narain 8 showing sample location. b, Lithostratigraphic column showing sample horizon. wedge is aparted from one another by 5 to 8 mm. The longest pairs of rib-shaped markings vary from 12 to 18 mm in length and 1 to 2 mm in width. Some markings are shifted towards the other side, suggesting changes in the movement of the animal. Repository ref.: WIHG/A/1574. Remarks: Specimens apparently show resemblance with Ichnogenus Dimorphichnus in the curved and sub parallel ridges. Specimens differ from ichnospecies of Dimorphichnus from Spiti 36 in the nature and pattern of markings of the traces. The present specimen differs from all other known ichnospecies of Dimorphichnus. The Ichnogenus Dimorphichnus is known from the Lower Cambrian successions of Salt Range 38. Ichnogenus: Diplichnites Dawson, 1873 Diplichnites isp. A (Figure 3 j, p) Description: Dissimilar paired rows of unequal marks, individual ridges elongate and oblique. Distances between two rows about 1 to 4 mm, thickness and length of each CURRENT SCIENCE, VOL. 90, NO. 1, 10 JANUARY

4 ridge varies from 2 to 3.5 mm. Distance between the two ridges varies from 0.5 to 2 mm. The paired marks occur in a row up to some distance and then shift slightly towards the left. This disposition of tracks suggests that the animals have moved laterally. Repository ref.: WIHG/A/1575, 76. Remarks: The present specimens show close similarity in pattern and in nature of ridges with Diplichnites recorded widely in Cambrian rocks. 116 Ichnogenus: Planolites Nicholson, 1873 Planolites isp. (Figure 3 h) Description: Straight to slightly curved horizontal trails. Width of the trail ranges from 1 to 2 cm, individual burrow is 1 to 2.5 cm long and 5 to 8 mm wide. Burrows are unbranched and irregularly developed. Repository ref.: WIHG/A/1577. Remarks: The specimen closely resembles Planolites in unbranched nature of burrows. The specimen differs with all the known species of Planolites. Planolites B (Figure 3 o) Description: The burrow is 15 mm long and 5 mm wide, slightly curved, comparatively wider on one side. Sediments incorporated in the host rock and in the trace are similar. Repository ref.: WIHG/A/1584. Ichnogenus: Skolithos Haldemann, 1840 Skolithos isp. (Figure 3 m, n) Description: Unbranched, sub cylindrical burrows; width of burrows ranges from 2 to 6 mm; space between burrows is wide. Repository ref.: WIHG/A/1578, 79. Remarks: In the present material no vertical sections are available. The form shows some similarity with Skolithos linearis Haldemann. Ichnogenus: Merostomichnites Packard, 1960 Merostomichnites isp. (Figure 3 b) Description: Two parallel, spindle-shaped rows arranged obliquely. Individual impression varies in length from 1 to 1.7 cm and in width from 0.5 to 0.9 mm. The trace is preserved as epirelief. Repository ref.: WIHG/A/1580. Remarks: The specimen differs from Dimorphichnus in behaviour and pattern of ribs. Ichnogenus: Neonereites Seilacher, 1960? Neonereites isp. (Figure 3 l) Description: Meandering trail with numerous irregular pellets. Shape of the pustusels and indistinct rows distinguish it from other traces. The trail is generally horizontal. Repository ref.: WIHG/A/1581. Remarks: The specimen shows close resemblance with the Ichnogenus Neonereites in its shape of irregular pellets. Ichnogenus A (Figure 3 d) Description: It comprises a single row of slightly curved, 2 3 mm wide and 5 6 mm long ridges 1 mm apart from each other. Repository ref.: WIHG/A/1583. Ichnogenus B (Figure 3 k) Description: The specimen comprises a single U-shaped horizontal burrow. The trace width is 0.9 to 1.5 mm. The burrow is infilled by a different material than that of the host rock. Repository ref.: WIHG/A/1582. Remarks: The specimen shows some resemblance with the Ichnogenus Diplocraterion Torell, 1870 (refs 39, 40) CURRENT SCIENCE, VOL. 90, NO. 1, 10 JANUARY 2006

5 a b d c B e f g A i k h n j p m l o Figure 3. a, c, g (A), Monomorphichnus isp.; b, Merostomichnites isp.; d, Ichnogenus A; e, Dimorphichnus isp.; f, g (B), i, Scratch marks; h, Planolites isp.; j, p, Diplichnites isp. A; k, Ichnogenus B; l,?neonereites isp.; m, n, Skolithos isp.; o, Planolites B; Bar = 1 cm. but differs in the nature of preservation. The latter possesses a paired circular opening, which is lacking in the present specimen. Hence the present specimen is grouped under an open nomenclature as Ichnogenus B. Scratch marks (Figure 3 f, g (B), i) Description: The scratch mark ridges are sigmoidal with width ranging from 1 to 2 mm and length 7 to 10 mm. Probably they are produced by trilobites and can be assigned as isolated fragments of Monomorphichnus. Repository ref.: WIHG/A/1573b; In addition to the above trace fossil genera, various meandering trails occur, which vary in length from 10 to 30 mm in width with a wider front portion. Other varieties of trails consist of equal parts with meandering structure or are slightly straight. These generally cross each other. In absence of body fossils, trace fossils are found to be important elements for deciphering Neoproterozoic Cambrian transition. The Tal Formation is a thick stratigraphic unit, but most fossils are facies-dependent. The present assemblage of trace fossils is mostly found in the form of burrows, tracks and trails along with scratch marks. The trails occur as grooves and ridges with positive epirelief on jointed and fractured micaceous sandstone, which makes it difficult to collect the complete specimen. Sometimes CURRENT SCIENCE, VOL. 90, NO. 1, 10 JANUARY

6 these traces are found in a clustered, pit-like form. It is difficult to assign whether these impressions represent negative epirelief or hyporelief. Mostly trace fossils produced by arthropods occur at the horizon at or shortly below those containing trilobites 41. It has been noticed that the Neoproterozoic trace fossils are small, simple, unbranched and were made close to the sediment water interface, whereas early Cambrian trace fossils are well-diversified traces of bilaterian animals, showing morphological diversity and complexity 2, Trace fossils like Monomorphichnus, Planolites, Skolithos, Diplichnites and Dimorphichnus are known from the other early Cambrian successions of the Tethyan Himalayan succession of Kashmir, Spiti. In the Zanskar region, their occurrence is below the trilobite-bearing horizons Monomorphichnus occurs close to the Neoproterozoic Cambrian boundary in many sections 2. In the Neoproterozoic Cambrian boundary GSSP in Newfoundland, Monomorphichnus first appears 2.5 m above the base of the Treptichnus pedum zone and is used along with Treptichnus pedum in defining the base of the basal Cambrian Stage 5,53. In the Lesser Himalayan sequence, Rai 52 assigned a Lower Cambrian age to the Arenaceous member of the Lower Tal Formation, on the basis of trace fossil occurrence. Trace fossils like Skolithos, making pipe rock facies are abundant in the Arenaceous member of Tal Formation and is common in Lower Cambrian of Scotland and Sweden 10. A diverse assemblage of brachiopods, microgastropods, hyolithids and poriferids of Lower Cambrian affinity was reported from the Calcareous member 9. Further report of a rich assemblage of brachiopod from shale member of the Upper Tal Formation suggested Atdabanian (=Qiongzhusian/Chiungchussu) stages of the Early Cambrian to the Upper Tal Formation 18,35. The beds that overlie and underlie the brachiopod horizon exhibit fairly well preserved trace fossils, including small vertical burrows and trilobite fragments. The Lower Quartzite member of the Upper Tal exposed in Sirmur district, Himachal Pradesh also shows presence of Palaeophycus isp., Skolithos isp., and arthropod traces of Lower Cambrian affinity 11. It was observed that the trace fossils present in the Tal Formation shows marked behavioural complexity and diversity and occur at various horizons, but distinct zones are not evident 54,55. The present finds of trace fossil assemblage can be correlated with other trace fossil assemblages of the Tethyan and Lesser Himalayan horizons, and hence are of stratigraphic significance. Due to scarcity of body fossils at this level, the present assemblage can be useful in identifying the complete Early Cambrian succession in the Tal Formation. 1. Seilacher, A., Neues Jahrb. Geol. Palaeontol. Abh., 1956, 103, Crimes, T. P., Geol. 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7 42. Droser, M. L., Gehling, J. G. and Jensen, S., Geology, 1999, 27, Jensen, S., Saylor, B. Z., Gehling, J. G. and Germs, G. J. B., Geology, 2000, 28, Landing, E., Geology, 1994, 22, Raina, B. K., Kumar, G., Bhargava, O. N. and Sharma, V. P., J. Palaeontol. Soc. India, 1983, 28, Bhargava, D. N. and Srikantia, S. V., J. Geol. Soc. India, 1982, 23, Kumar, G., Raina, B. K., Bhargava, O. N., Maithy, P. K. and Babu, R., Geol. Mag., 1984, 121, Shah, S. K. and Sudan, C. S., J. Geol. Soc. India, 1983, 24, Shah, S. K., Kumar, A. and Sudan, C. S., J. Geol. Soc. India, 1998, 51, Parcha, S. K., J. Geol. Soc. India, 1998, 51, Daily, B., Centre for Precambrian Research Spl. Paper 1(13), Univ. Adelaide, South Australia, 1972, pp Rai, V., J. Paleontol. Soc. India, 1987, 32, Linan, E., Perejon, A. and Sdzuy, K., Geol. Mag., 1993, 130, Sudan, C. S., Sharma, U. K., Sahni, A. K. and Shah, S. K., J. Geol. Soc. India, 2000, 55, Hughes, N. C., Peng, S. and Luo, H., J. Paleontol., 2002, 76, ACKNOWLEDGEMENTS. We thank the Director, Wadia Institute of Himalayan Geology, Dehradun for providing the necessary facilities and for encouragement. We also thank the unknown reviewers for their constructive suggestions and Sh. Tirath Raj for photographing the samples. Received 11 July 2005; revised accepted 11 October 2005 Vertebrate steroids and the control of female reproduction in two decapod crustaceans, Emerita asiatica and Macrobrachium rosenbergii V. Gunamalai 1, R. Kirubagaran 2 and T. Subramoniam 1, * 1 Unit of Invertebrate Reproduction, Department of Zoology, University of Madras, Guindy Campus, Chennai , India 2 National Institute of Ocean Technology, Pallikkaranai, Chennai , India Vertebrate steroids, estradiol-17β (E 2 ) and progesterone (P), have been estimated in the hemolymph, ovary and hepatopancreas of mole crab Emerita asiatica and freshwater prawn Macrobrachium rosenbergii during the reproductive and molt cycle stages by radioimmunoassay. The maximum level of E 2 in hemolymph, ovary and hepatopancreas was detected only during the intermolt stage, whereas the level gradually decreased during premolt and postmolt stages in E. asiatica. The *For correspondence. ( thanusub@yahoo.com) E 2 level in the hemolymph was high in crabs with mature ovaries, while those with quiescent ovaries were low or undetectable. The trend in P level in all tissues during different molt and reproductive stages was remarkably similar to that of E 2. However, in M. rosenbergii, with two types of molt cycles, viz. reproductive and common (non-reproductive) molt, E 2 and P levels in hemolymph, ovary and hepatopancreas showed wide variation between them. During the reproductive molt cycle, the level of E 2 and P in all tissues peaked during intermolt, but declined drastically at premolt and postmolt stages. On the contrary, the level of E 2 in hemolymph was not detectable in any molt stage during the non-reproductive molt with the ovary containing undeveloped oocytes. However, the inactive ovary and hepatopancreas showed basal level of E 2 during non-reproductive molt cycle, whereas P was totally undetectable in the above tissues. Cumulatively, these studies suggest that the ovary may synthesize E 2 and release them into the hemolymph from where it may reach the hepatopancreas to stimulate vitellogenin synthesis in the two decapods. P may have a role in the post-vitellogenic meiotic maturation of the oocytes, as in vertebrates. Keywords: Crustaceans, estradiol-17β, molting, progesterone, reproduction. UNLIKE insects, most malacostracan crustaceans continue growth and molting with reproductive activities. Hormonal coordination of molting and reproduction in crustaceans is achieved by the combinatorial effects of eyestalk inhibitory neuropeptides and a variety of trophic hormones. The control of molting in crustaceans is accomplished by the common arthropodan molting hormone, ecdysteroid, the action of which is uniquely inhibited by the molt-inhibiting hormone 1. Similarly, the inhibitory role of gonadinhibitory hormone on the reproductive activities, especially on vitellogenesis, has been well documented 2,3. Conversely, there are discordant results concerning the gonad stimulatory factors among various crustacean species. For example, earlier studies revealed the occurrence of gonad stimulatory neuropeptides in the brain and thoracic ganglia of some crustaceans 4. Following this, several hormonal factors such as methyl farnesoate, a structural homologue of insect juvenile hormone, ecdysteroids as well as vertebrate steroids like estradiol-17β (E 2 ) and progesterone (P) have been implicated with inducement of ovarian maturation in different crustacean species (see ref. 5 for review). Apparently, crustaceans might employ more than one type of gonad stimulatory principles in the control of vitellogenesis, the central event of oogenesis. In decapod Crustacea, physiological processes of both molting and female reproduction are linked and hence the temporal separation of reproductive and molting activities becomes a necessity for judicial apportioning of the organic storage materials for both these energy-demanding processes. Yet another complexity in the female reproduction of malacostracan crustaceans is that they carry the brood CURRENT SCIENCE, VOL. 90, NO. 1, 10 JANUARY