Palynostratigraphy of the Devonian strata of southwestern Shahrud

Authors

1 Assistant Professor, Department of Geology, Tarbiat Moallem University – Tehran

2 M.Sc. Tarbiat Moallem University – Tehran

Abstract

Diverse and reasonably well preserved palynofloras including 148 species, dominated by­ microphytoplankton cysts (acritarchs and prasinophyte phycomata) and spore assemblages, occur in most of surface samples of the Geirud Formation at the Dehmolla section; scolecodonts and chitinozoans are also represented as subordinate components. Co-occurrence of marine and terrestrial palynomorphs clearly indicates deposition in a marginal marine setting. Vertical distribution pattern of spores permits erection of two local assemblage zones in the material studied (here informally termed assemblage zones I and II). Occurrence in assemblage zone I of such distinctive spores as Grandispora inculta, Cymbosporites catillus, Geminospora lemurata, Teichertospora iberica, Laevigatosporites ovatus, Densosporites spitsbergensis, Punctatisporites labiatus, Retusotriletes rugulatus, R. pychovii, R. dubiosus, Dictyotriletes australis, Diducites mucronatus, Archaeoperisaccus sp., Stenozonotriletes conformis, and Ancyrospora ancyrea collectively denotes an early Late Devonian (Frasnian) age; the assemblage appears to be compatible with the ovalis-bulliferus and parts of the optivus-triangulatus and torquata-gracilis Assembalge Zones of the Old Red Sandstone Continent (ORSC). The succeeding assemblage II embracing Retispora lepidophyta, Vallatisporites hystricosus, V. vallatus, Verruciretusispora loboziakii, Punctatisporites planus, Densosporites rarispinosus, and Grandisporafacilis correlates with the pusillites-lepidophyta, flexuosa-cornuta, and  torquata-gracilis (partial) Assemblage Zones of the ORSC and is ascribed to late Late Devonian (Famennian). Additionally, a barren interval (20 m thick) devoid of any palynomorphs can also be identified in the basal, mostly red conglomerates and coarse-grained sandstones of the section studied. Co-occurrence of spore assemblages with such globally index microphytoplankton cysts as Cymatiosphaera perimembrana, Daillydium pentaster, Unellium lunatum, U. piriforme, Chomotriletes vedugensis, Crassiangulina sp. cf. C. tesselita corroborates the Late Devonian (Frasnian-Famennian) age assignment which is in general agreement with the faunal evidence. Affinity, diversity, and abundance of spores in the palynofloras investigated imply that contemporaneous coastal vegetation was probably diverse and likely dominated by lycopsids, filicopsids, and archaeopterid progymnosperms.
 
 

Keywords

References

 
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Fig. 1. Leiosphaeridia sp. ×2000. Fig. 2. Cymatisphaera perimembrana Staplin, 1961. ×1200. Fig. 3. Cymatiosphaera radiosepta Hashemi & Playford, 1998. ×1200. Fig. 4. Dictyotidium araiomegaronium Hashemi & Playford, 1998. ×1900. Fig. 5. Dictyotidium craticulum (Wicander & Loeblich) Wicander & Playford, 1985. ×1500. Fig. 6. Dictyotidium senticogremium Hashemi & Fahimi, 2006. ×1600. Fig. 7. Maranhites perplexus Wicander & Playford, 1985. ×600. Fig. 8. Maranhites britoi Stöckmans & Willière, 1969. ×700. Fig. 9. Arkonia sp. cf. A. nova Le Hérissé, 2002. ×1100. Fig. 10. Chomotriletes vedugensis Naumova, 1953. ×1300. Fig. 11. Crassiangulina sp. cf.C.tesselitaJardiné et al., 1972. ×650. Fig. 12. Daillydium pentaster (Staplin) emend. Playford in Playford & Dring, 1981. ×1400. Fig. 13. Deltotosoma intonsum Playford in Playford & Dring, 1981. ×1100. Fig. 14. Gorgonisphaeridium asperum Hashemi & Playford, 1998. ×900. Fig. 15. Gorgonisphaeridium plerispinosum Wicander, 1974. ×1100. Fig. 16. Gorgonisphaeridium tabasense Hashemi & Playford, 1998. ×780. Fig. 17. Gorgonisphaeridium ohioense (Winslow) Wicander, 1974. ×950. Fig. 18. Gorgonisphaeridium telum Wicander & Playford, 1985. ×1300. Fig. 19. Papulogabata lobata Hashemi & Playford, 1998. ×1320. Fig. 20. Scolecodont. × 820.
 
 
 
 
 
Fig. 1. Elektoriskos tenuis Playford in Playford & Dring, 1981. ×1500. Fig. 2. Lophosphaeridium papillatum (Staplin) Martin, 1969. ×1250. Fig. 3. Lophosphaeridium granulosum (Staplin) Playford, 1976. ×1000. Fig. 4. Saharidia lusca Playford in Playford & Dring, 1981. ×1700. Fig. 5. Micrhystridium pentagonale Stöckmans & Willière, 1963. ×1700. Fig. 6. Micrhystridium stellatum Deflandre, 1945. ×1850. Fig. 7. Solisphaeridium inaffectum Playford in Playford & Dring, 1981. ×1300. Fig. 8. Solisphaeridium spinoglobosum (Staplin) Wicander, 1974. ×1050. Fig. 9. Stellinium comptum Wicander & Loeblich, 1977. ×770. Fig. 10. Stellinium micropolygonale (Stöckmans & Willière) Playford, 1977. ×580. Fig. 11. Stellinium rabians (Cramer) Eisenack, Cramer & Díez, 1976. ×1085. Fig. 12. Stellinium octoaster (Staplin). Jardiné, Combaz, Magloire, Peniguel, & Vachey, 1972. ×900. Fig. 13. Tornacia sarjeantii Stöckmans & Willière, 1966. ×1500. Fig. 14. Papiliotypus sp. cf. P. pulvinus Hashemi & Playford, 1998. ×2000. Fig. 15. Spurimoyeria  iranica Hashemi & Playford, 1998. ×2500. Fig. 16. Unellium lunatum (Stöckmans & Willière) Eisenack et al. 1979. ×1750. Fig.17. Unellium piriforme Rauscher, 1969. ×2000. Fig. 18. Veryhachium downiei Stöckmans & Willière, 1962. ×1800. Fig. 19. Veryhachium inflatum Hashemi & Playford, 1998. ×1800. Fig. 20. Chitinozoan. × 600.
 
 
 
 
 
 
Fig. 1. Leiotriletes inermis (Waltz) Ishchenko, 1952. ×680. Fig. 2. Punctatisporites glaber (Naumova) Playford, 1963. ×800. Fig. 3. Retusotriletes planus Dolby & Neves, 1970. ×1100. Fig. 4. Retusotriletes dubiosus McGregor, 1973. × 1200. Fig. 5. Retusotriletes rotundus (Streel) Streel, 1967. ×800. Fig. 6. Retusotriletes rugulatus Riegel, 1973. ×680. Fig. 7. Apiculatasporites perpusillus (Naumova) McGregor, 1973. ×800. Fig. 8. Dictyotriletes australis de Jersey, 1966. ×950. Fig. 9. Cymbosporites catillus Allen, 1965. ×850. Fig. 10. Verruciretusispora loboziakii Tunbridge et al., 2002. ×1150. Fig. 11. Densosporites spitsbergensis Playford, 1963. ×560. Fig. 12. Vallatisporites hystricosus (Winslow) Byvscheva, 1985. ×1250. Fig. 13. Ancyrospora ancyrea (Eisenack) Richardson var. ancyrea Richardson, 1962. ×530. Fig. 14. Concentricosisporites Sagittarius Rodriguez, 1983. ×700. Fig. 15. Diducites mucronatus (Kedo)Van Veen, 1981. ×720. Fig. 16. Geminospora lemurata Balme emend. Playford, 1983. ×950. Fig. 17.Grandispora cornuta Higgs, 1975. ×1100. Fig. 18.Grandispora famenensis (Naumova) Streel var. minuta Nekriata, 1974. ×1050. Fig. 19. Retispora lepidophyta (Kedo) Playford, 1976. ×530. Fig. 20. Gneudnaspora divellomedia (Chibrikova) Balme, 1988 var. minor Breuer et al., 2007. ×1400.
 
Journal of Stratigraphy and Sedimentology Researches
Volume 27, Issue 2 - Serial Number 2
September 2011
Pages 27-40

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