Cold and wet Last Glacial Maximum on Mount Sandıras, SW Turkey, inferred from cosmogenic dating and glacier modeling

https://doi.org/10.1016/j.quascirev.2008.01.002Get rights and content

Abstract

In situ cosmogenic 36Cl was measured in boulders from moraines on Mount Sandıras (37.1°N, 28.8°E, 2295 m), the southwestern most previously glaciated mountain in Turkey. Valleys on the north side of the mountain were filled with 1.5 km long glaciers that terminated at an altitude of 1900 m. The glacial activity on Mount Sandıras correlates with the broadly defined Last Glacial Maximum (LGM). The maximum glaciation occurred approximately 20.4±1.3 ka (1σ; 1 ka=1000 calendar years) ago, when glaciers started retreating and the most extensive moraines were deposited. The glaciers readvanced and retreated by 19.6±1.6 ka ago, and then again by 16.2±0.5 ka. Using the glacier modeling and the paleoclimate proxies from the Eastern Mediterranean, we estimated that if temperatures during LGM were 8.5–11.5 °C lower than modern, precipitation was up to 1.9 times more than that of today. Thus, the local LGM climate was cold and wet which is at odds with the conventional view of the LGM as being cold and dry in the region.

Introduction

The evidence of past glacial activities in mountain settings provides direct information of the magnitude and frequency of past climate changes. Because of the unique location of Turkey in the transition zone between the temperate Mediterranean climates influenced by North Atlantic cyclones (Macklin et al., 2002) and the subtropical high pressure climatic zone (la Fontaine et al., 1990), the paleoclimate of Turkey is highly sensitive to climatic perturbations that affect the position and/or intensity of the westerly storm tracks that carry moisture from the North Atlantic and Mediterranean Sea. Thus, studying the timing and extent of past glacial activity as a proxy of past climates on Turkey can reveal valuable information on Late Quaternary climate changes.

Several mountain ranges in Turkey supported glaciers during the Late Quaternary (Erinç, 1952; Messerli, 1967; Birman, 1968; Kurter and Sungur, 1980; Çiner, 2004; Akçar et al., 2007). Among these, the Taurus Mountain Range, in south Anatolia, has two-thirds of the previously glaciated mountains in the country. On the far east (Fig. 1), Mount Cilo (4135 m) has the largest glaciated area in Turkey, including ice caps and valley glaciers up to 4 km long (Kurter, 1991). In the central Taurus, Mount Aladağlar (3756 m) has a well-preserved moraine record of extensive Early Holocene glaciers (Klimchouk et al., 2006; Zreda et al., 2006). While much lower than their eastern counterparts, the western Taurides also have several mountains with evidence of Pleistocene glaciers. Mount Dedegöl (2990 m, Zahno et al., 2007), Beydağ (3086 m, Messerli, 1967), Akdağ (3016 m, Onde, 1952) and Sandıras (2295 m, de Planhol, 1953; Doğu, 1993) (Fig. 1) show several cirques and well-preserved glacier related landforms especially on their north and northeast facing slopes. Today, due to the increasing effect of continentality from west to east in Anatolia, western mountains experience wetter and warmer climate than the eastern mountains. Today, active glaciers are present only in central and eastern mountains, and their sizes are increasing from west to east. Additionally, Late Pleistocene equilibrium line altitude (ELA) estimates in Turkey support this continental effect (Messerli, 1967; Erinç, 1971, Erinç, 1978; Atalay, 1987). During the Last Glacial Maximum (LGM, 21,000 calendar years ago), western Anatolian mountains had ELAs as low as 2000–2400 m while eastern mountains had ELAs about 3000–3200 m.

Glacial deposits in all these mountains have been studied to some degree, but few of them have been dated numerically. Most of the age estimates for glacial deposits are based on relative dating techniques, including stratigraphic relationships, degree of weathering and soil development (de Planhol, 1953; Birman, 1968; Doğu, 1993). Generally, previous studies assigned Late Pleistocene to the age of glaciation in the southwest Taurus Mountains (de Planhol, 1953; Doğu, 1993; Çiner, 2004 and references therein).

The glacial landforms on Mount Sandıras were mapped and their lithostratigraphy described in detail by de Planhol (1953) and Doğu (1993). However, because these glacial deposits have not been dated numerically, the exact timing of glaciations is unknown, which precludes paleoclimatic interpretation based on the glacial records. In this study, we examined the timing (from the age of landforms) and magnitude (from the position of ice margins) of paleoclimatic changes on Mount Sandıras by using the cosmogenic 36Cl exposure dating method. We modeled the glacier response to climatic changes using a glacier model to reconstruct temperature and precipitation at the time of glaciation. Finally, we compared our paleoclimatic findings with other Late Quaternary climate proxies from the Eastern Mediterranean region.

Section snippets

Physical setting and climate

Mount Sandıras (37.1°N, 28.8°E, 2295 m above mean sea level), also known as Çiçekbaba (Flower father, in Turkish), Sandras or Gölgeli Dağları (Shaded Mountains), is the southwestern most previously glaciated mountain in the Anatolian Peninsula (Fig. 1). The mountain is located about 40 km from the Mediterranean coast. The land elevation increases rapidly towards inland creating a natural climatic barrier between the coastal area and the interior.

The summit of Mount Sandıras is a plateau

Evidence of glacial action on Mount Sandıras

Philippson (1915), cited by Doğu (1993), first described evidence of former glaciations on Mount Sandıras. de Planhol (1953) suggested that an ice cap covered the flat top of the mountain during the Würm glacial age and the tongues of that ice cap reached an altitude of 1900 m on the north side. He calculated the Würm glaciation snow line (similar to ELA) to be at 2000–2050 m and proposed that this snow line lower than that on other mountains in southwestern Turkey is due to the tectonic lowering

Determination of 36Cl ages

We used the cosmogenic 36Cl method (Davis and Schaeffer, 1955; Phillips et al., 1986; Zreda and Phillips, 2000) to determine surface exposure ages of boulders from moraines associated with the Sandıras glaciation. Chlorine 36 is produced in rocks by collisions of cosmic-ray neutrons and muons with atoms of Cl, Ca and K (Zreda et al., 1991). Once produced, it remains in place and accumulates continuously with time (Zreda and Phillips, 2000). Because the production rates of 36Cl from the three

Cosmogenic 36Cl exposure ages

We dated six boulders from the Kartal Lake Valley and three from the Northwest Valley (Fig. 2; Table 1). All boulder ages include correction for thickness and shielding by surrounding topography and snow. The uncertainties quoted for the boulder ages were calculated by propagation of analytical errors on 36Cl/Cl and on Cl (both reported by the AMS laboratory) and assuming a 20% uncertainty on the calculated nucleogenic component. Boulder age uncertainties are based only on analytical errors and

Conclusion

The most extensive glacial advance on Mount Sandıras ended by 20.4±1.3 ka ago, and the final deglaciation commenced by 16.2±0.5 ka ago. Modeling of glacier mass balance shows a wide range of possible temperatures and precipitation rates necessary to produce Mount Sandıras glaciers. Without independent estimates of temperature and precipitation for LGM, model results do not provide a unique combination of these variables based on simulated ice extent. An LGM half as wet as today requires a cooling

Acknowledgments

This research was supported by the US National Science Foundation (Grant 0115298) and by the Scientific and Technological Research Council of Turkey (TÜBİTAK) (Grant 101Y002).

References (88)

  • G. Gvirtzman et al.

    Climate of the last 53,000 years in the Eastern Mediterranean based on soil-sequence stratigraphy in the coastal plain of Israel

    Quaternary Science Reviews

    (2001)
  • P.D. Hughes et al.

    Late Pleistocene glaciers and climate in the Mediterranean

    Global and Planetary Change

    (2006)
  • M.D. Jones et al.

    Quantifiying climatic change through the last glacial-interglacial transition based on lake isotope paleohydrology from central Turkey

    Quaternary Research

    (2007)
  • N. Kallel et al.

    Mediterranean and pluvial periods and sapropel formation during last 200 000 years

    Palaeogeography Palaeoclimatology Palaeoecology

    (2000)
  • K. Kashima

    Environmental and climatic changes during the last 20 000 years at Lake Tuz, Central Turkey

    Catena

    (2002)
  • M.G. Macklin et al.

    Correlation of fluvial sequences in the Mediterranean basin over the last 200 ka and their relationship to climate change

    Quaternary Science Reviews

    (2002)
  • S. McGarry et al.

    Constraints on hydrological and paleotemperature variations in the Eastern Mediterranean region in the last 140 ka given by the δD values of speleothem fluid inclusions

    Quaternary Science Reviews

    (2004)
  • P.J. Mudie et al.

    Pollen stratigraphy of Late Quaternary cores from Marmara Sea: land-sea correlation and paleoclimatic history

    Marine Geology

    (2002)
  • F.M. Phillips et al.

    An improved approach to calculating low-energy cosmic ray neutron fluxes near the land/atmosphere interface

    Chemical Geology

    (2001)
  • S.C. Porter

    Equilibrium-line altitudes of late Quaternary glaciers in the Southern Alps, New Zealand

    Quaternary Research

    (1975)
  • N. Roberts

    Age, paleoenvironments and climatic significance of Late Pleistocene Konya Lake, Turkey

    Quaternary Research

    (1983)
  • N. Roberts et al.

    Chronology and stratigraphy of Late Quaternary sediments in the Konya Basin, Turkey: results from the KOPAL Project

    Quaternary Science Reviews

    (1999)
  • S.A. Robinson et al.

    A review of paleoclimates and paleoenvirments in the Levant and Eastern Mediterranean from 25 000 to 5 000 years BP: setting the environmental background for the evolution of human civilization

    Quaternary Science Reviews

    (2006)
  • J.O.H. Stone et al.

    Cosmogenic chlorine-36 production in calcite by muons

    Geochimica et Cosmochimica Acta

    (1998)
  • T.W. Swanson et al.

    Determination of 36Cl production rates derived from well dated deglaciation surfaces of Whidbey and Fidalgo Islands, Washington

    Quaternary Research

    (2001)
  • A. Vaks et al.

    Paleoclimate and location of the border between Mediterranean climate region and the Saharo-Arabian Desert as revealed by speleothems from the northern Negev Desert, Israel

    Earth and Planetary Science Letters

    (2006)
  • M.G. Zreda et al.

    Cosmogenic Chlorine-36 production rates in terrestrial rocks

    Earth and Planetary Science Letters

    (1991)
  • Almasi, P.F., 2001. Dating the paleobeaches of Pampa Mejillones, Northern Chile by cosmogenic chlorine-36. M.S. Thesis,...
  • Anderson, K.M., Bradley, E., Zreda, M., Rassbach, L., Zweck, C., Sheehan, E., 2007. ACE: Age Calculation Engine—a...
  • I. Atalay

    Introduction to Geomorphology of Turkey

    (1987)
  • J.H. Birman

    Glacial reconnaissance in Turkey

    Geological Society of America Bulletin

    (1968)
  • R.J. Braithwaite

    Positive degree-day factors for ablation on the Greenland ice sheet studied by energy-balance

    Journal of Glaciology

    (1995)
  • R.J. Braithwaite et al.

    Sensitivity of mass balance of five Swiss glaciers to temperature changes assessed by tuning a degree-day model

    Journal of Glaciology

    (2000)
  • Collins, A.S., 1997. Tectonic evolution of Tethys in the Lycian Taurides, southwest Anatolia. Ph.D. Thesis, University...
  • A.S. Collins et al.

    Processes of Late Cretaceous to Late Miocene episodic thrust-sheet translation in the Lycian Taurides, SW Turkey

    Journal of the Geological Society, London

    (1998)
  • R.J. Davis et al.

    Chlorine-36 in nature

    Annals of the New York Academy of Science

    (1955)
  • de Graciansky, P.C., 1967. Existance d’une nappe ophiolitique à l’extrémité occidentale de la chaîne sud-anatolienne;...
  • de Planhol, X., 1953. Les formes glaciaires du Sandıras Dag et la limite des neiges eternelles quaternaries dans le SW...
  • Doğu, A.F., 1986. Geomorphology of Koycegiz and Dalaman lowland and surrounding area (in Turkish). Ph.D. Thesis, Ankara...
  • A.F. Doğu

    Glacier shapes on the Mount Sandıras

    Turkish Geography Bulletin, Ankara University

    (1993)
  • A.F. Doğu

    The importance of Akkopru terraces (Dalaman River) in geomorphology of southwest Anatolia

    Turkish Geography Bulletin, Ankara University

    (1994)
  • J. Ehlers

    Quaternary and Glacial Geology

    (1996)
  • H.N. Elsheimer

    Application of an ion-selective electrode method to the determination of chloride in 41 international geochemical reference materials

    Geostandards Newsletter

    (1987)
  • Emeis, K.C., Schulz, H.M., Struck, U., Sakamoto, T., Doose, H., Erlenkeuser, H., Howell, M., Kroon, D., Paterne, M.,...
  • Cited by (123)

    View all citing articles on Scopus
    View full text