CAMPANIAN CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY OF EASTERN KOPPEH-DAGH BASIN (NORTH EAST OF IRAN), TETHYAN REALM

Tethyan calcareous nannofossil assemblages have been recorded from three sections of the Abtalkh Formation including the type section at Abtalkh village and two others (Padeha and Jalilabad) in the east Koppeh-Dagh Basin, north east of Iran. The formation studied is expanded with a thickness of up to 1770 m at the type locality in the middle of eastern Koppeh-Dagh spanning biozones UC15bTP to UC16 while in the Padeha (973.5 m thick) in east and Jalilabad (1316 m thick) section in the west the formation spans biozones UC14dTP–UC15aTP to of UC16. The zonation erected indicates an age of early–latest Campanian for the Abtalkh Formation. The recorded assemblages are of low-latitude to intermediate forms suggesting placement of the Koppeh-Dagh Basin in low to intermediate latitudes during Campanian

Calcareous nannofossil biostratigraphy of Sarcheshmeh and Sanganeh formations in the west of Kopet-Dagh Basin, Sheikh Section

Abstract The Kopet-Dagh Basin is located in the north and north east of Iran, within the border triangle of Iran, Turkmenistan and Afghanistan. Sediments of Cretaceous age are well exposed in this basin. Sarcheshmeh and Sanganeh formations belong to the Cretaceous age in this basin and have the highest thickness in the west of the basin. Calcareous nannofossil investigation at the Sheikh section (in the west of the Kopet-Dagh Basin) lead to the recognition of 84 species from 35 genera which are belonging to 16 families. According to the index calcareous nannofossils, the upper part of NC5 Zone (Watznaueria oblonga Zone), NC6 Zone (Chiastozygus litterarius Zone) and the lower part of NC7a biozone (Rhagodiscus angustus Zone) are recognized at the Sarcheshmeh Formation and NC7a biozone (Rhagodiscus angustus Zone) is recognized at the basal part of Sanganeh Formation. Based on the calcareous nannofossils data, the age of Sarcheshmeh Formation is Late Barremian-early Late Aptian and the age of Sanganeh Formation is early Late Aptian -?Late Aptian

Calcareous nannofossil response to Late Cretaceous climate change in the eastern Tethys (Zagros Basin, Iran)

14 pagesInternational audienceConiacian to Maastrichtian changes in calcareous nannofossil assemblages have been investigated in the eastern Tethyan Shahneshin section (central Zagros Basin, Iran). The nannofossil assemblages are mainly composed of Watznaueria spp. (avg. 54%), Retecapsa spp (avg. 7.9%), Cribrosphaerella ehrenbergii (avg. 7.7%) and Micula spp. (avg. 5.7%). Throughout the late Campanian, there is a trend to lower abundances in Watznaueria spp. together with increasing abundances of C. ehrenbergii and Arkhangelskiella cymbiformis, which are considered in this basin as the main cool-water taxa. Our results reveal that, despite a diagenetic impact on calcareous nannoflora, a number of primary paleoecological trends are preserved which depict well features of the progressive Late Cretaceous cooling. The first pronounced cooling episode occurs across the late Campanian to early Maastrichtian. The onset of pronounced cooling in the eastern Tethys appears to occur prior to the Campanian/Maastrichtian Boundary event (CMBE) δ13C negative excursion, in contrast with the Boreal realm where pronounced cooling only occurs in the early Maastrichtian, postdating the onset of the CMBE. The coincidence of this earlier cooling in the Zagros Basin with an interval characterized by a significant increase in benthic foraminifera suggests an amplified response of the assemblage due to a change to shallower environments. Hence, the late Campanian calcareous nannofossil assemblage turnover in central Zagros is either a response to an early cooling trend in the eastern Tethys or to sea-level fall or both. The mid-Maastrichtian warming and late Maastrichtian cooling episodes are also delineated in the nannofossil assemblage of Shahneshin and likely correlate with similar episodes in the Boreal Realm

Integrated bio- and carbon-isotope stratigraphy of the Upper Cretaceous Gurpi Formation (Iran):A new reference for the eastern Tethys and its implications for large-scale correlation of stage boundaries

29 pagesInternational audienceA high-resolution stratigraphic analysis of the Upper Cretaceous Gurpi Formation has been undertaken in the Shahneshin section (Zagros Basin, Iran). New results on calcareous nannofossils, planktic foraminifers, dinoflagellate cysts and high-resolution carbon and oxygen stable isotopes form the basis of a reference section for the eastern Tethys that spans the upper Coniacian to the late Danian. Carbon-isotope correlation to Gubbio, Italy and the NW German chalk allows for the identification of many isotopic events as well as for the definition of new events in the Campanian and Maastrichtian. Our results allow for a review of the accurate position of the Coniacian/Santonian, Santonian/Campanian, and Campanian/Maastrichtian stage boundaries relative to carbon isotopes and plankton bioevents. The reliability of Coniacian to Maastrichtian planktic foraminifer, dinoflagellate cysts and calcareous nannofossil biohorizons is assessed