Hydroclimatic variations over the last two glacial/interglacial cycles at Lake Urmia, Iran

Abstract

A coarse-resolution, absolutely dated isotope record spanning the last 180 ka was constructed from aragonite-rich fecal pellets in a sediment core from Lake Urmia, Iran. The isotope record is not continuous as a consequence of detrital calcite that contaminates the pellets at certain depths. An isotopic correction was applied to samples [ 50% aragonite, using the d 18 O values of calcite-only pellets. Absolute dates were derived from U-Th analyses on pellets [ 80% aragonite. The resultant d 18 O record and sediment lithofacies confirm that the Penultimate Glacial was cold and dry, with pronounced interstadials at ca. 150 and [175 ka. Deglaciation began at ca. 130 ka, but climate was unstable and supported a probable no-analog vegetation assemblage. The onset of true interglacial conditions occurred at ca. 126 ka. Peak moisture conditions lasted for 5-6 ka before the climate became drier, with the loss of some tree taxa towards the end of the Last Interglacial. A period of greater moisture occurred between 116 and 108 ka, overlapping in timing with interstadial conditions recorded in the Soreq Cave speleothem record. In general, stadial to interstadial transitions (OIS 5d-5c, 5b-5a) are marked by decreasing d 18 O values and rising lake levels. The nature of the OIS 5 to OIS 4 transition cannot be resolved in this study because of the loss of 5 m of core and imprecise dates. According to the present chronology, d 18 O values, and inferred lake levels, arid conditions began at 60 ka and persisted until Termination I. Episodic increases in moisture, characterized by layers of aragonite-rich pellets, ostracodes, and the pollen of trees and/or aquatic plants, occurred during the Last Glacial. Deglaciation associated with the Late-glacial Interstadial began at 14 ka but was interrupted by a marked Younger Dryas event that resulted in renewed aridity. The Holocene began at approximately 10 ka. Despite large errors in the chronology, the overall timing and pattern of effective moisture matches the record from Soreq Cave, Israel, suggesting that the two regions were climatically in-phase.

Vegetation and environmental changes during the last interglacial in eastern Anatolia (Turkey): a new high-resolution pollen record from Lake Van

“…Such event stratigraphy may miss changes in climate variability and possible lags in vegetation response. However, Stevens et al (2012) point out that the LI starts at ca. 130 ka BP, with full interglacial conditions at~126 ka BP (time lag ca.…”

“…5C). Most of the thermophilous trees disappear at~116 ka, although Stevens et al (2012) mentioned that Quercus pollen persisted until~110 ka (Fig. 5C).…”

“…The low-resolution pollen sequence of Lake Urmia (NW Iran, Fig. 1) is available for this time period (Van Zeist and Bottema, 1977;Bottema, 1986;Djamali et al, 2008;Stevens et al, 2012) and only recently, the publications of Shumilovskikh et al (2012Shumilovskikh et al ( , 2013 have complemented the last interglacial picture in northern Anatolia based on cores from the Black Sea. In light of the scarcity of long continental archives in the Near East, Lake Van is in a key position to clarify regional paleoclimate evolution (Litt et al, 2012).…”

Biodiversity of the Hypersaline Urmia Lake National Park (NW Iran)

“…Palaeoecological and geochemical investigations of long sediment cores from Urmia Lake have revealed that lake levels underwent dramatic changes during the glacial-interglacial cycles of the Quaternary period [17,50,87]. Based on the total thickness of the fluvio-lacustrine infill of the Urmia Lake basin, as revealed by geophysical explorations and the dated 100-m long core samples taken from the central basin, the age of the lake can be grossly estimated at >600,000 years.…”

“…Although the glacial periods are known as periods with a significant loss of biodiversity, they were times of a more diversified plant and most probably animal life within the lake and in its associated ecosystems. The presence of several peaks of brackish to fresh water dinoflagellates and Pediastrum (green alga) indicate that the algal life also increased in response to the dilution of lake water [17,50,87,88]. …”