Introduction and Biostratigraphy of the the Middle Tethys Ocean Calcareous Nannofossils in the Upper Cretaceous in Central Iran

A detailed investigation into the calcareous nannofossils from the upper Campanian–Maastrichtian deposits of the Kladorub Formation (NW Bulgaria) has been carried out in order to examine their taxonomic content and test the applicability of cosmopolitan zonation schemes for this stratigraphic interval in the country. The Kladorub Formation is composed of silty to fine-sandy marlstones and rare marly limestones, occasionally interbedded with sandstone layers. The recovered nannofloras are abundant, taxonomically diverse and exhibit predominantly moderate preservation, which allowed precise taxonomic identifications and biostratigraphic analysis to be made. As a result, the presence of two previously undocumented, biostratigraphically significant taxa has been recorded (i.e., Eiffellithus parallelus and Ceratolithoides kamptneri). Consequently, the studied Upper Cretaceous sediments have been assigned to subzone UC15dTP (pars.)–subzone UC20dTP; in the uppermost 2 m of the section, the presence of zone NP1 has also been indicated, which is in concordance with previous authors’ data. Due to the lack of proper chronostratigraphic framework for the Kladorub Formation, top Uniplanarius trifidus and base Lithraphidites quadratus have, respectively, been used to approximate the Campanian/Maastrichtian and lower/upper Maastrichtian boundaries. The Cretaceous/Palaeogene boundary, however, could not be drawn with precision, because it falls within a 6.5-m interval of non-exposure. The resulting biostratigraphic framework offers higher stratigraphic resolution than previously used local zonation schemes and allows correlation with coeval sedimentary successions from other parts of the Tethyan and Boreal realms.

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Biostratigraphy of Baghamshah Formation based on calcareous nannofossils in the Southwest Tabas, Iran

Revista Brasileira de Paleontologia ◽

10.4072/rbp.2021.3.01 ◽

2021 ◽

Vol 24 (3) ◽

pp. 165-178

Author(s):

Azadeh Bordbar ◽

Fatemeh Hadavi ◽

Abbas Ghaderi ◽

Marziyeh Notghi Moghaddam

Keyword(s):

Central Iran ◽

Calcareous Nannofossils ◽

The West ◽

Lithostratigraphic Unit ◽

Lut Block ◽

Sedimentary Cycle ◽

Taxonomic Studies

The Tabas Block is part of the Central Iran microcontinent, located between the Lut Block in the East and the Yazd Block in the West. The Baghamshah Formation is the second lithostratigraphic unit from the sedimentary cycle of the Magu Group and the Baghamshah Subgroup in the Jurassic of Tabas Block. This formation is conformably underlaid with the grey pisoidal limestones of the Parvadeh Formation and overlaid with the Pectinid limestones of the Kamar-e-Mehdi Formation (Esfandiar Subgroup). In this research, the biostratigraphy of the Baghamshah Formation in the Rizu and Kamar-e-Mehdi sections, based on calcareous nannofossils, is examined. The thickness of the Baghamshah Formation in the Rizu section is 270 m (mostly including marl and green shales with intercalation of limestones and calcareous sandstones), and in the Kamar-e- Mehdi section is 236 m (composed of gypsiferous marly shales, marl, marly shales and alternation of marl-shale with limestones and calcareous sandstones). According to the taxonomic studies in the Rizu section, 52 species belong to 24 genera, and in the Kamar-e-Mehdi section, 45 species belong to 23 genera of calcareous nannofossils. Based on index calcareous nannofossils, the CC1, CC2, CC3, and CC4 biozones established by Sissinghh in both sections were determined. It is mentioned that CC5 biozone only occur in Kamar-e-Mehdi section. According to the identified biozones, the suggested age of the Baghamshah Formation is early Berriasian–early Hauterivian in the Rizu section, and early Berriasian–late Hauterivian in the Kamar-e-Mehdi section. Keywords: biostratigraphy, Baghamshah, calcareous nannofossils,Tabas, Iran.

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Some new and rarely documented Late Cretaceous calcareous nannofossils from subsurface sediments in South Carolina

Journal of Paleontology ◽

10.1017/s0022336000040786 ◽

1999 ◽

Vol 73 (5) ◽

pp. 952-963 ◽

Cited By ~ 2

Author(s):

Jean M. Self-Trail

Keyword(s):

South Carolina ◽

Upper Cretaceous ◽

New Combination ◽

Calcareous Nannofossils ◽

Calcareous Nannofossil ◽

East Central ◽

Transmission Electron ◽

Subsurface Sediments ◽

Central South ◽

Upper Campanian

One new calcareous nannofossil genus Senilatus; four new calcareous nannofossil species Calculites favosus, Lithraphidites? charactozorro Self-Trail and Pospichal, Rucinolithus oriens, and Watznaueria bybelliae; and one new combination, Senilatus zipperum n. gen. and comb., are described from Upper Cretaceous (upper Campanian to Maastrichtian) sediments of east-central South Carolina. These new species were described from five coreholes located in marine coastal plain deposits. There is evidence that the presence of one species, Senilatus zipperum, is indicative of nearshore, restricted environments. Scanning electron and light microscope pictures are provided for two species, Cretarhabdus multicavus Bukry, 1969 and Retemediaformis teneraretis Varol, 1991, that have previously been documented only with the transmission electron microscope. The ranges of these two species have been extended beyond those stated in the original descriptions.

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