Biostratigraphy and Paleoecology of Maastrichtian and Paleocene Sediments in the Northern Alborz, Iran, Using Foraminifera

Abstract

In this study, the late-Maastrichtian and early-Paleocene transition at the Ziarat-Kola section has been investigated to recognize the biostratigraphy and paleoenvironmental changes. We applied a high-resolution quantitative study by using planktic foraminifera taxa and benthic foraminiferal morphotypes. Sixty-five species belong to twenty-eight genera were identified and seven biozones were differentiated. These biozones are 1. Racemiguembelina fructicosa, 2. Pseudoguembelina hariaensis, 3. Pseudoguembelina palpebra, 4. Parvularugoglobigerina eugubina, 5. Parasubbotina pseudobulloides, 6. Subbotina triloclinoides, 7. Globonomalina compressa-Preamurica inconstans. In the late Maastrichtian, benthic and planktic foraminifera are well mixed of epifauna/infauna morphotypes and diversified suggesting a stable and mesotrophic environment. By contrast, the early Paleocene is marked by high values of epifaunal benthic morphogroups, and extinction of Cretaceous species suggesting highly unstable and variable conditions, partly due to the dramatic collapse of calcareous primary producers. Additionally, four different zones were determined based on the benthic foraminifera morphogroups that show several changes in oxygen and organic matter flux during this time. Also, analysis of planktic foraminifera genera in this section indicating a close similarity with assemblages in Tethyan provinces.