Document Type : Original Research Paper

Authors

Department of Geology, Faculty of Science, Tarbiat Moallem University, Tehran, Iran

Abstract

The Upper Devonian sequences in vicinity of Darvar, southwest Damghan comprise alternation of conglomerates, quartzites, sandstones, siltstones, shales, with fossiliferous limestone intercalations unconformably overlying the Ordovician strata and gradually preceding carbonates of the Lower Carboniferous Mobarak Formation. Diverse biota embracing brachiopods, trilobites, fish, gastropods, corals, echinoderms, and conodonts in conjunction with well preserved palynomorphs, in descending order of abundance, of both terrestrial and marine origin occur in the Upper Devonian strata (Geirud Formation) of Darvar, southwest Damghan. Scolecodonts rarely occur in the material studied but no representative of Chitinozoans encountered. Based on the known stratigraphic distribution of taxa such as Cymatiosphaera perimembrana, Chomotriletes vedugensis, Deltotosoma intonsum, Papulogabata annulata, Tornacia sarjeantii, Unellium lunatum, Unellium piriforme, Retispora lepidophyta, Geminospora lemurata, Retusotriletes rugulatus, Grandispora cornuta, Grandispora sp. cf. G. gracilis the Geirud Formation is attributed to the Late Devonian (Frasnian-Famennian). Occurrence, in the material studied, of microphytoplankton cysts with relatively thin eilyma and ±circular, psilate or sculptured vesicle indicates deposition in a shallow, marginal marine depositional setting. Presence of Geminospora lemurata in majority of the samples refers to the occurrence of progymnosperms and that of poorly preserved Lepidodendrales to that of lycopodophytes in contemporaneous land vegetation. Affinity of sporae dispersae in the Geirud palynoflora indicates that fern allies such as Equisetopsida, Lycopodopsida, Rhyniopsida, and Progymnosperms were represented in the land vegetation. Relative abundance of Geminospora lemurata and spores attributed to lycopodophytes imply domination of the land vegetation by lycopodohytes and progymnosperms.

Keywords

References
Al-Ameri, T. K., 1983- Observations on the wall structure and the excystment mechanism of acritarchs. Journal of Micropalaeontology, 5(2): 27-35.
Alavi, M. & Bolourchi, M. H., 1973- Explanatory text of the Maku Quadrangle Map, 1: 250,000. Geological Survey of Iran, Tehran.
Assereto, R., 1963- The Paleozoic formations in central Elburz, Iran (preliminary note). Rivista Italiana Paleontologia e Stratigraphia, 60(4): 503-543.
Balme, B. E., 1995- Fossils in situ spores and pollen grains: an annotated catalogue. Review of Palaeobotany and Palynology, 87(2-4): 85-323.
Barss, M. S. & Williams, G. L., 1973- Palynology and nanofossil processing techniques. Geological Survey Canada, Paper, 73-26: 1-25.
Bozorgnia, F., 1973- Paleozoic foraminiferal biostratigraphy of central and east Alborz Mountains, Iran. National Iranian Oil Company, Geology Laboratories, Publication no. 4, 185 p.
Dashtban, H. & Racheboeuf, P., 2001- First occurrence of Echinocaridid phyllocarids (Crustacean) in the Famennian of Iran. Neues Jahrbuch für Geologie und Palaontologie, Monatshefte, pp. 58-94.
Dorning, K. J., 1981- Silurian acritarch distribution in the Ludlovian shelf area of South Wales and the Welsh Borderland. In: Neale, R. and Brasier, M. B. (eds.): Microfossils from Recent and fossil shelf seas. Ellis Horwood, Chichester, 31-36.
Downie, C., 1963- “Hystrichospheres” (acritarchs) and spores of the Wenlock Shales (Silurian) of Wenlock, England. Palaeontology, 6(4): 625-652.
Downie, C., 1973- Observations on the nature of acritarchs. Palaeontology, 16 (2): 239-259.
Gensel, P. G., Johnson, N. G. & Strother, P. K., 1990- Early land plant debris (Hooker’s “waifs and strays”?). Palaios, 5: 520-547.
Ghavidel-Syooki, M., 1994- Upper Devonian acritarchs and miospores from the Geirud Formation in Central Alborz rang, northern Iran: Journal of Sciences, Islamic Republic of Iran. 5(3): 103-122.
Ghavidel-Syooki, M., 1995- Palynostratigraphy and palaeogeography of a Palaeozoic sequence in the Hassanakdar area, central AlborzRange, northern Iran: Review of Palaeobotany and Palynology, 86: 91-109.
Górka, H., 1969- Microorganismes de l’Ordovicien de Pologne. Palaeontologica Polonica, 22: 102pp.
Gray, J. & Boucot, A. J., 1972- Palynological evidence bearing on the Ordovician-Silurian paraconformity in Ohio. Bulletin of Geological Society of America, 83(5): 1299-1314.
Hashemi, H. & Fahimi, M., 2006- Dictyotidium senticogremium sp. nov., a new prasinophyte (Chlorophyta) phycoma from the Upper Devonian of northern Iran. Micropaleontology, 52(1): 87-93.
Hashemi, H. & Playford, G., 2005- Devonian spore assemblages of the Adavale Basin, Queensland (Australia): Descriptive systematics and stratigraphic significance. Revista Española de Micropaleontologia, 37(3): 317-417.
House, M. R., Scrutton, C. T. & Bassett, M. G., 1979- The Devonian System. A Palaeontological Association International Symposium. Special Papers in Palaeontology, 23: 353pp.
Jacobson, S. R., 1979- Acritarchs as paleoenvironmental indicators in Middle and Upper Ordovician rocks from Kentucky, Ohio, and New York. Journal of Paleontology, 53(5): 1197-1212.
Le Hérissé, A., 1989- Acritarches et kystes d'algues prasinophycées du Silurien de Gotland, Suède. Palaeontographia Italica, 76: 57-302.
Le Hérissé, A. & Gourvennec, R., 1992- Paleobiology of Silurian-Early Devonian acritarchs. 8th International Palynological Congress, Aix-en-Province, Program and Abstracts, p. 83.
McMillan, N. J., Embry, A. F. & Glass, D. J., 1988- Devonian of the World. Memoirs of the Canadian Society of Petroleum Geologists, no. 14, 2 volumes.
Marshall, J. E. A. & Allen, K. C., 1982- Devonian miospore assemblages from Fair Isle, Shetland. Palaeontology, 25(2): 277-312.
Molynex, S. G., Le Hérissé, A. & Wicander, R., 1996- Paleozoic plankton. In: Jansonius, J. and McGregor, D. C. (eds.): Playnology: principles and applications, 2: 493-529. American Association of Stratigraphic Palynologists Foundation.
Oswald, D. H., 1968- International Symposium on the Devonian System. Calgary (1967). Alberta Society of Petroleum Geologists. 2 volumes.
Phipps, D. & Playford, G., 1984- Laboratory techniques for extraction of palynomorphs from sediments. Papers, Department of Geology, University of Queensland., 11(1): 23 pp.
Richardson, J. B., 1984- Mid-Palaeozoic palynoloy, facies and correlation. Proceedings of 27th International Geology Congress, V.N.U. Science Press, 2: 341-365.
Richardson, J. B. & Rasul, S. M., 1990- Palynofacies in a Late Silurian regressive sequence in the Welsh Borderland and Wales. Journal Geological Society London. 147: 675-686.
Riegel, W., 1974- Phytoplankton from the upper Emsian and Eifelian of the Rhineland, Germany - a preliminary report. Review of Palaeobotany and Palynology, 18(1-2): 29-39.
Sarmiento, R., 1957- Microfossil zonation of Mancos Group. Bulletin of the American Association of Petroleum Geologists, 41(8): 1683-1693.
Sartenaer, P., 1964- Découverte d’un niveau a plantes d’âge Famenňien supérieur dans l'Elburz central (Iran).Rivista Italiana Paleontologia e Stratigraphia, 70(4): 651-655.
Smith, N. D. & Saunders, R. S., 1970- Paleoenvironments and their control of acritarch distribution in the Silurian of east-central Pennsylvania. Journal of Sedimentary Petrology, 40(1): 324-333.
Staplin, F. L., 1961- Reef-controlled distribution of Devonian microplankton in Alberta. Palaeontology, 4(3): 392-424.
Strother, P. K., 1996- Acritarchs. In: Jansonius, J. and McGregor, D.C. (eds.). Palynology: principles and applications, 1: 81-106. American Association of Stratigraphic Palynologists Foundation.
Thusu, B., 1972- Depositional environments of the Rochester Formation (Middle Silurian) in southern Ontario. Journal of Sedimentary Petrology, 42(4): 930-934.
Traverse, A., 2007- Paleopalynology, 2nd edition. Springer Verlag, 813 p.
Tyson, R. V., 1995- Sedimentary Organic Matter: Organic Facies and Palynofacies. Chapman & Hall, London, 615 p.
Upshaw, C. F., 1964- Palynological zonation of the Upper Cretaceous Frontier Formation near Dubios, Wyoming. In: Cross, A.T. (ed.): Palynology in oil exploration: a symposium. Society of Economic Paleontologists and Mineralogists, Special Publication, 11: 153-168.
Viquesnal, A., 1850- Notice sur la collections de roches recueillie  Asie par feu Hommaire de Hell en Perse (mort a Isfahan en 1848) et sur les divers trauvaux executes pendant la cours de son voyage. Bulletin Société Géologique France, Series 2, Vol. 7: 419-517.
Wall, D., 1965- Microplankton, pollen, and spores from the Jurassic in Britain. Micropalaeontology, 11:151-190.
Williams, G. L. & Sarjeant, W. A. S., 1967- Organic-walled microfossils as depth and shoreline indicators. Marine Geology, 5:389-412.
Wood, G. D., Gabriel, A. M. & Lawson, J. C., 1996- Palynological techniques processing and microscopy. In: Jansonius, J.&McGregor, D.C. (eds.): Palynology: Principles and Applications. 1: 29-50. American Association of Stratigraphic Palynologists Foundation.