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

Abstract

New palynological and ostracod data are presented from the Holocene Volga delta, obtained from short cores and surface samples collected in the Damchik region, near Astrakhan, Russian Federation in the northern Caspian Sea. Four phases of delta deposition are recognized and constrained by accelerated mass spectrometry (AMS) radiocarbon ages. Palynological records show that erosive channels, dunes (Baer hills) and inter-dune lakes were present during the period 11,500-8900 cal. BP at the time of the Mangyshlak Caspian lowstand. The period 8900-3770 cal. BP was characterized regionally by extensive steppe vegetation, with forest present at times with warmer, more humid climates, and with halophytic and xerophytic vegetation present at times of drought. The period 3770-2080 cal. BP was a time of active delta deposition, with forest or woodland close to the delta, indicating relatively warm and humid climates and variable Caspian Sea levels. From 2080 cal. BP to the present-day, aquatic pollen is frequent in highstand intervals and herbaceous pollen and fungal hyphae frequent in lowstand intervals. Soils and incised valley sediments are associated with the regional Derbent regression and may be time-equivalent with the 'Medieval Warm Period'. Fungal spores are an indicator of erosional or aeolian processes, whereas fungal hyphae are associated with soil formation. Freshwater algae, ostracods and dinocysts indicate mainly freshwater conditions during the Holocene with minor brackish influences. Dinocysts present include Spiniferites cruciformis, Caspidinium rugosum, Impagidinium caspienense and Pterocysta cruciformis, the latter a new record for the Caspian Sea. The Holocene Volga delta is a partial analogue for the much larger oil and gas bearing Mio-Pliocene palaeo-Volga delta.

Base level changes, river avulsions and Holocene human settlement dynamics in the Caspian Sea area (middle Kura valley, South Caucasus)

“…BP, Fig. 6), followed by the Derbent lowstand period (Kroonenberg et al, 2007(Kroonenberg et al, , 2008Richards et al, 2014), and the 'Medieval Warm Period' (with development of pine forest cover, Fig. 11.…”

Cyst‐Theca Relationship and Phylogenetic Position of Impagidinium caspienense Incubated from Caspian Sea Surface Sediments: Relation to Gonyaulax baltica and Evidence for Heterospory within Gonyaulacoid Dinoflagellates

“…, ); and (vii) the northern Caspian Sea (Richards et al. ). The irregular height of the septa, the occurrence of a high septum at the junction of the paraplate 1′′′′ and the sulcus, and the low intratabular relief separate I. caspienense from all other extant Impagidinium species (Marret et al.…”

“…(v) Holocene of the Caspian Sea (Leroy et al 2007(Leroy et al , 2013a; (vi) the late Pleistocene to Holocene of the centre of the middle and south Caspian Sea basins (Leroy et al 2013b; and (vii) the northern Caspian Sea (Richards et al 2014). The irregular height of the septa, the occurrence of a high septum at the junction of the paraplate 1 0000 and the sulcus, and the low intratabular relief separate I. caspienense from all other extant Impagidinium species (Marret et al 2004, p. 13).…”

Spiniferites cruciformis,Pterocysta cruciformisandGaleacysta etrusca: morphology and palaeoecology

“…Overlying sediments of the Kirmaky Suite are dated as early Pliocene (Zanclean) based on magnetostratigraphy (van Baak 2015) and these fluvio-lacustrine beds contain occasional Spiniferites cruciformis, in association with Caspidinium rugosum Marret in Marret et al 2004 and varied numbers of freshwater algae (Richards 2012). Spiniferites cruciformis is then rare but consistently present within the sediments of the Pliocene Productive Series (Richards et al 2014a) and becomes locally abundant during the Pleistocene (Richards et al 2011(Richards et al , 2014a and new data shown in Sect. 3).…”