Holocene stable isotope record of insolation and rapid climate change in a stalagmite from the Zagros of Iran

Abstract

We explore Holocene climatic change as recorded by stable isotopes in a single, well-dated, stalagmite from the northern Zagros Mountains of Iran, a region where stalagmite records have so far only provided short glimpses of Holocene climatic changes. Stalagmite KT-3 from Katalekhor Cave began growing ~9.5 ka under wet early Holocene conditions (δ 18 O values around or below -9.0‰, maximum growth diameter and lowest 234 U/ 238 U0 activity values). Progressive reduction in winter precipitation amount after 7.0 ka was driven by decreasing summer insolation, indicated by increasing δ 18 O and 234 U/ 238 U0 activity values and reduction in growth diameter until ~2.0 ka. Centennial-scale variability is not a feature of the δ 18 O record suggesting a stable winter recharge regime without marked interannual rainfall variability. KT-3 δ 13 C compositions are enriched relative to lower altitude stalagmites in the Levant, implying low soil CO2 contribution (thin montane soils) with stronger ingress of atmospheric CO2. However, the δ 13 C values also show ~ 1.5‰ centennial-scale variability with higher δ 13 C values between 8.3-7.7 ka, 6.5-5.5 ka, 5.4-4.5 ka and ~4.3-2.0 ka: three of these correspond with Rapid Climate Change (RCC) events based on non-seasalt potassium (K + ) in Greenland ice cores. Higher δ 13 C values indicate poor soil development caused by aridity. The first centennial-scale δ 13 C anomaly (8.3-7.7 ka) is in part overprinted by the ~160 year-long, 8.2 ka cold/dry event, but culmination ~7.7 ka corresponds with other records suggesting an intensified Siberian High Pressure system affecting regional climate. The centennial-scale δ 13 C anomaly between 4.3 and 2.0 ka overlaps the 2.65 to 2.50 ka 'Assyrian megadrought' evident in stalagmite stable isotope records in northern Iraq. The KT-3 record is key in better understanding Holocene climate change in the central Zagros region, representative of montane 'fertile crescent' environments. The KT-3 δ 18 O record also suggests that nearby lacustrine carbonate isotope records (Lakes Zeribar and Mirabad) can be reinterpreted as insolation-driven records, starting wet, but with recharge decreasing until ~7.0 ka, followed broadly by developing aridity.

Morphoevolution of the Seymareh landslide-dam lake system (Zagros Mountains, Iran): Implications for Holocene climate and environmental changes

“…At the end of the early Holocene (~9-8.5 ka), the continental dry conditions progressively shifted towards a wetter climate regime typical of the Mediterranean area, as recorded by more negative δ 18 O values from Mirabad, Zeribad, Van and Katalekhor (Fig. 9; Stevens et al, 2001;Wick et al, 2003;Stevens et al, 2006;Çagatay et al, 2014;Andrews et al, 2020). However, during this period, pollen records (Stevens et al, 2001;Wasylikowa, 2005;Stevens et al, 2006;Wasylikowa et al, 2006;Litt et al, 2014) still highlight dry conditions, showing the delayed vegetation response to the climatic transition.…”

“…During the early Holocene (~10-9 ka), when the emplacement of the Seymareh landslide formed the dam lakes (Roberts and Evans, 2013;Shoaei, 2014;Delchiaro et al, 2019Delchiaro et al, , 2020, dry climate conditions prevailed in the Middle East, as demonstrated by the δ 18 O curves reported in Fig. 9 (Stevens et al, 2001;Wick et al, 2003;Stevens et al, 2006;Çagatay et al, 2014;Andrews et al, 2020). In addition, Griffiths et al (2001) proposed that the early Holocene low-level phase in Mirabad Lake, located on the surface of Seymareh landslide debris, where shallow-water ostracods were detected, was related to the increase in water temperature and the abundance of winter precipitation.…”

“…The climatic conditions in the Zagros Mountains are mostly controlled by three different climate regimes: (i) the Mediterranean in the west, (ii) the monsoon in the south, and (iii) the continental in the eastern and northern sectors. The area corresponds to the easternmost sector of the ancient Near East Fertile Crescent, where rainfall occurs in winter because of cyclogenesis in the Arabian Sea, Persian Gulf, Red Sea, and northern Indian Ocean (Evans and Smith, 2006;Andrews et al, 2020). The modern Iranian climate is mainly characterized by arid and semiarid conditions, especially in the Iranian plateau where the Caspian and the Mediterranean basins are bounded by the Alborz and Zagros-Bitlis Mountains, respectively.…”

“…The level of uncertainty is mainly because of the temporal overlap of the errors of the ages of the different samples and is strictly dependent on the dating method. (Stevens et al, 2006), Zeribad Lake (Stevens et al, 2001), b, c) Van Lake (Wick et al, 2003;Çagatay et al, 2014), and d) Katalekhor stalagmite (Andrews et al, 2020). e, f, g, h) Focus of the δ 18 O curves in the period from 8 to 7 ka.…”

Remote sensing applications for the assessment of the geomorphic response of fluvial systems to the Holocene Climate Changes

“…The mean annual rainfalls in the UMP ranges from 400 to 150 mm/yr, while in the LMP the annual rainfalls decrease to 140 mm/yr (Engel and Brückner, 2018). Besides the considerable number of geo-bio-archives in the north and west Mesopotamia heartland, such as the marine records of the eastern Mediterranean and northern Red Seas, and the Mirabad and Zeribar lake records in the Zagros Mountains (e.g., Stevens et al, 2001;Wick et al, 2003;Wasylikowa et al, 2006;Stevens et al, 2006;Jones and Roberts, 2008;Bar-Matthews et al, 2011;Engel et al, 2012;Zanchetta et al, 2014;Talebi et al, 2016;Andrews et al, 2020), their proxy data are not suitable for reconstructing the LMP climate conditions during the Holocene (Engel and Brückner, 2018).…”