River inflow and salinity changes in the Caspian Sea during the last 5500 years

Abstract

Pollen, spores and dinoflagellate cysts have been analysed on three sediment cores (1.8 to 1.4 m-long) taken from the south and middle basins of the Caspian Sea. A chronology available for one of the cores is based on calibrated radiocarbon dates (ca 5.5-0.8 cal. ka BP). The pollen and spores assemblages indicate fluctuations between steppe and desert. In addition there are some outstanding zones with a bias introduced by strong river inflow. The dinocyst assemblages change between slightly brackish (abundance of Pyxidinopsis psilata and Spiniferites cruciformis) and more brackish (dominance of Impagidinium caspienense) conditions. During the second part of the Holocene, important flow modifications of the Uzboy River and the Volga River as well as salinity changes of the Caspian Sea, causing sea-level fluctuations, have been reconstructed. A major change is suggested at ca 4 cal. ka BP with the end of a high level phase in the south basin. Amongst other hypotheses, this could be caused by the end of a late and abundant flow of the Uzboy River (now defunct), carrying to the Caspian Sea either meltwater from higher latitudes or water from the Amu-Daria. A similar, later clear phase of water inflow has also been observed from 2.1 to 1.7 cal. ka BP in the south basin and probably also in the north of the middle basin.

Reconstructions of deltaic environments from Holocene palynological records in the Volga delta, northern Caspian Sea

“…Dinocyst evidence from the central and southern Caspian Sea regions also suggests that early to mid-Holocene Caspian Sea levels were mainly high, with highest levels being reached prior to c. 4000 cal. BP, coinciding with maximum abundances of the dinocysts P. psilata and I. caspienense, caused by increased glacial melt-water from the Pamir Mountains via the Uzboy and Amu-Darya river systems (Leroy et al, 2007(Leroy et al, , 2013a. The end of Delta Phase 2 at Damchik occurs at more or less the same time as a cold and dry episode interpreted at around 4000 cal.…”

Caspian sea-level changes during the last millennium: historical and geological evidence from the south Caspian Sea

“…The largest input of sediments in the whole of the CS comes, however, from the Sefidrud (Lahijani et al, 2008). According to Leroy et al (2007), the Aral Sea and CS were connected episodically during the last millennia through the Uzboy pass ( Fig. 1) due to sea level fluctuations, tectonic events or human intervention.…”

“…4) is dependent on the reservoir effect (RE), which has been estimated differently in various studies: from 290 to 400 yr (Leroy et al, 2011). For example, some of the reported RE ages are: 345 to 384 14 C yr in Karpychev (1993), 290 14 C yr in Kroonenberg et al (2007), 390-440 14 C yr in Kuzmin et al (2007), and 383 14 C yr in Leroy et al (2007). Although almost all of the chronological data are coincident with the LIA in the North Atlantic Ocean and already recorded in the CS by a high-stand (Leroy et al, 2011 in Gilān, andKakroodi et al, 2012 in Golestān), they could be linked to different sealevel rise episodes between the fifteenth and the nineteenth centuries, depending on the reservoir age used in calibrating the radiocarbon dates.…”

Late Little Ice Age palaeoenvironmental records from the Anzali and Amirkola Lagoons (south Caspian Sea): Vegetation and sea level changes

“…The increasing demands for development of 63 human activities in the coastal areas reinforce the necessity for unravelling 64 the history of sea-level fluctuations (Leroy et al, 2010). Records of the CS-65 level changes have been discovered both offshore and in coastal sediments 66 (Rychagov, 1997;Leroy et al, 2007). On the basis of these studies, some 67 CS-level curves have been reconstructed.…”