Quarternary ecostratigraphy and paleogeographic reconstructions of the Caspian region based on benthic foraminifera
Дата
2014
Назва журналу
Номер ISSN
Назва тому
Видавець
Nafta-Press
Анотація
Stratigraphy and paleoenvironmental reconstructions of the Caspian Quaternary are based largely on changes in the evolutionary patterns and ecological characteristics of the mollusk Didacna Eichwald in coastal outcrops and drillholes (Yanina, 2005, 2013; Yanina and Svitoch, 2014 [this volume]).
In contrast, this paper is focused on ecostratigraphic and paleoenvironmental reconstructions of the Caspian Quaternary using benthic foraminifera as the main evaluation tool. The value of benthic foraminifera for these purposes is well known. They are ubiquitous in marine environments and have tremendous taxonomic diversity; therefore they have the potential for diverse biological responses to environmental changes. Their tests are readily preserved in sediments and are small and abundant compared to other larger hard-shelled taxa (such as mollusks). This makes them particularly easy to recover in statistically significant numbers (Yanko et al., 1999).
In our work, we follow the Russian divisions of the Quaternary System, which separates the Quaternary into the Eopleistocene (1.8-0.78 Ma), the Neopleistocene (0.78-0.01 Ma), and the Holocene (0.01-0.0 Ma) (Zhamoida, 2002). The boundary between the Eopleistocene and Neopleistocene coincides with the Matuyama-Brunhes reversal [MBR], which is readily traced in both the BS and CS regions at the bottom of the Lower Chaudian and Gurian horizons, respectively.
The first information on Caspian foraminifera was published by Ehrenberg (1873), who identified 23 species in the surface sediments of 132 stations located at water depths of 6-836 m. Most of the species were found in areas above 25 m water depth; with increasing depth, their number decreased to 1-2 species. At least two species (Rotalia globulosa Ehrenberg and Textularia globulosa Ehrenberg) were recognized as reworked from the Cretaceous. About one hundred years later, Bening (1937) described 13 benthic species. Klenova (1956) found three recent species and plenty of reworked Cretaceous foraminifera. None of the abovementioned studies provided data on the quantitative distribution of foraminifera except for Klenova (1956), who mentioned that 75% of the foraminifcral assemblages consist of Rotalia beccarrii (Linne). The most complete data set on recent foraminifera of the Caspian Sea was provided by Mayer (1980). She described 18 species, two of which (Hemisphaerammina sp. and Saccammina sp.) were given in open nomenclature, two others—Miliamina fusca (Brady) and Trichohyalus aguajoi (Bermudez)—are well known from the literature, and the rest were described by Mayer for the first time. There are some recent publications on modem foraminifera of the Caspian Sea (Ghane et al., 2014) and very few (Svitoch et al., 1992) on those from Quaternary sediments of the Caspian region.
Опис
Proceedings of the second plenary conference IGCP 610 "From the Caspian to Mediterranean: environmental change and human response during the quaternary", (2013-2017) : international geoscience programme, 12-20 oktober 2014 / ed. in chief: A. S. Gilbert ; The Azerbaijan national acad. of sciences, Geology and geophysics inst. – Baku : Nafta-Press, 2014.
Ключові слова
stratotypes, salinity, sea level, water exchange
Бібліографічний опис
Proceedings of the second plenary conference IGCP 610 "From the Caspian to Mediterranean: environmental change and human response during the quaternary", (2013-2017) : international geoscience programme, 12-20 oktober 2014