Stratigraphy and Palaeontology
Azam Mahanipour; Maryam Eftekhari; Soheila Soheili
Abstract
In order to study the early Aptian Oceanic Anoxic Event 1a (OAE 1a), calcareous nannofossils are investigated at the late Barremian ‒ early Aptian sediments of the Garau Formation at south west of the Kabir-Kuh anticline, Qaleh-Darreh section. Ninety species of calcareous nannofossils from 43 genus ...
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In order to study the early Aptian Oceanic Anoxic Event 1a (OAE 1a), calcareous nannofossils are investigated at the late Barremian ‒ early Aptian sediments of the Garau Formation at south west of the Kabir-Kuh anticline, Qaleh-Darreh section. Ninety species of calcareous nannofossils from 43 genus and 15 families are identified along with marker species like Hayesites irregularis and Eprolithus floralis. Based on index calcareous nannofossil taxa, the studied interval is located between the uppermost part of the CC6/NC5 and the early part of CC7/NC7A. The first occurrence of H. irregularis, the marker of the Barremian ‒ Aptian boundary, used as an index species between CC6/NC5E and CC7/NC6. Statistical analysis of the calcareous nannofossil assemblages at the studied interval indicate the presence of nannoconid decline at the Barremian ‒ Aptian boundary and early Aptian and nannoconid crisis at CC7a/NC6B biozone. Nannoconid crisis is one of the main markers of the early Aptian OAE 1a that is recorded from different parts of the world at the Tethys and Boreal realms, Atlantic and Pacific oceans at the early Aptian (NC6 biozone). At the current study the early Aptian OAE 1a is recorded from the Garau Formation based on calcareous nannofossil assemblages.
Stratigraphy and Palaeontology
Maryam Eftekhari; Azam Mahanipour; Mohammad Dastanpour
Abstract
Abstract Barremian sediments of the Garau Formation have been investigated at the southwest of the Kabir-kuh anticline (Qaleh-Darreh section) with regard to calcareous nannofossils. According to the presence of index calcareous nannofossils, NC5 biozone and NC5c, NC5d and NC5e subzones of Roth (1978) ...
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Abstract Barremian sediments of the Garau Formation have been investigated at the southwest of the Kabir-kuh anticline (Qaleh-Darreh section) with regard to calcareous nannofossils. According to the presence of index calcareous nannofossils, NC5 biozone and NC5c, NC5d and NC5e subzones of Roth (1978) and CC5-CC6 biozones of Sissingh (1977) have been identified. At the studied interval, warm water taxa like Cyclagelosphaera margerelii, Diazomatolithus lehmanii, Lithraphidites carniolensis, Micrantholithus spp., Nannoconus spp., Rhagodiscus asper and Watznaueria spp. have been recorded along with cool water taxa such as Biscutum constans, Helenea chiastia and Zeugrhabdotus embergeri. The abundance of warm water taxa is higher than cool water taxa and a reverse trend can be observed between them. Regarding cool and warm water taxa three warming phases and two cooling phases are identified which includes the warming event of early Early Barremian, cooling event of Early Barremian, warming event of Mid-Barremian, cooling event of late Barremian and warming event of Barremian-Aptian boundary. It must be mentioned that these data are in accord with other parts of the world in the Tethyan (e.g., Italy) and the Boreal realms (e.g., NW Germany and NE England). Keywords: Barremian, Biostratigraphy, Paleoecology, Garau Formation, Calcareous nannofossils.
