In this research, the biostratigraphy of the Cretaceous deposits was investigated in the eastern margin of Lut Block in Khunik startigraphic section, west of Qaen, based on calcareous nannofossils. The stratigraphic interval mainly consists of marls with sandstone inter More
In this research, the biostratigraphy of the Cretaceous deposits was investigated in the eastern margin of Lut Block in Khunik startigraphic section, west of Qaen, based on calcareous nannofossils. The stratigraphic interval mainly consists of marls with sandstone interlayers (196 m thick). According to the systematic studies, 30 nannofossil species belonging to 20 genera were identified. Based on the presence of index calcareous nannofossils such as Calcicalathina oblongata, Speetonia colligata, Eiffellithus striatus and the fossil assemblages Calcicalathina oblongata Zone (CC3), Cretarhabdus loriei Zone (CC4) and Lithraphidites bollii Zone (CC5) these deposits are equivalent to NK3A subzone – middle part of NC5B subzone. According to the determined biozones, early Valanginian to late Hauterivian age was suggested for the studied interval.
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Paleocene-Miocene sediments in the central part of the Gorgan Plain were studied to evaluate lithostratigraphy, biostratigraphy and reconstruction of the paleogeography of the South Caspian Basin (SCB). Based on nannofossils distribution in the studied interval, the fol More
Paleocene-Miocene sediments in the central part of the Gorgan Plain were studied to evaluate lithostratigraphy, biostratigraphy and reconstruction of the paleogeography of the South Caspian Basin (SCB). Based on nannofossils distribution in the studied interval, the following points were identified: Foram layers equivalent sediments have Thanetian –Eocene age and Upper Maykop- Diatom equivalent sediments have Middle-Late Miocene age. Evaluation of the nannofossils distribution in the studied interval has clarified a major unconformity between lower Paleocene-Eocene sediments and the upper Middle-late Miocene sediments. This unconformity is coincident with collisional event of the Afro-Arabia and Eurasia Plates and rising of the surrounding mountain ranges around the Caspian Basin including Alborz and Kopet-Dagh Mountains. Nannofossils distribution of the studied succession displays that the SCB was connected to the Black Sea and Mediterranean Basin in the lower Middle Miocene and was isolated in the Middle-Late Miocene. The interpreted east-west running seismic lines displays a clear increase in the sediment thickness and accommodation space from eastern to western part of the Gorgan Plain. The higher available accommodation space from east to west of the Gorgan Plain led to a delay in the subaerial exposure in the western part of the Gorgan Plain due to rising of the Kopet-Dagh and Alborz Ranges. This interpretation is consistent with the lack of the Paleocene-Eocene sediments and presence of the Cretaceous sediments below the major unconformity in the eastern part of the Gorgan Plain and presence of the Paleocene-Eocene sediment below the unconformity in the studied area.
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