Lake Van deep drilling project PALEOVAN
Introduction
Long continental paleoclimate records mainly based on lacustrine sediments are prime targets of the International Continental Scientific Drilling Project – ICDP (Harms et al., 2007). During the last recent years, successful deep drilling operations have been carried out in Lake Baikal (Colman et al., 1995), Lake Titicaca (Rowe et al., 2003), Lake Malawi (Scholz et al., 2007), Lake Bosumtwi (Koeberl et al., 2007), Lake Petén Itzá (Anselmetti et al., 2006, Hodell et al., 2006), Lake Potrok Aike (Zolitschka et al., 2013), Lake Qinghai (Zhisheng et al., 2006) and Lake El'gygytgyn (Melles et al., 2012). However, our knowledge about paleoclimate evolution during the past glacial–interglacial cycles in the Near East based on long continental records was rather poor. Only the last two glacial–interglacial cycles are documented in a low-resolution pollen record from Lake Urmia, Iran (Djamali et al., 2008) and probably from the recently drilled Dead Sea sedimentary record (Stein et al., 2011). Continuous continental records covering more than the last 200 ka are only available in SE Europe (i.e. pollen record from Tenaghi Philippon and Ioannina, see Tzedakis et al., 1997, Tzedakis et al., 2001, Tzedakis et al., 2006).
Considering this lack of available regional paleoclimate data, Lake Van (Turkey) was flagged as a suitable additional candidate for an ICDP project to analyze past climate and environmental changes (Litt et al., 2009). Lake Van's morphometry (e.g., volume and depth) suggested that its partially varved lacustrine sediments hold a continuous climate archive spanning multiple glacial–interglacial cycles. The lake is situated at a key climatic position at the crossroad of the atmospheric south-western jet stream and the northern branch of the subtropical high-pressure belt. The former, steering the pathways of deep-pressure cyclones, is responsible for the supply of moist Mediterranean air masses from spring to autumn seasons, and the latter is controlling the southward extension of dry continental climate of north-eastern Europe and Asia (La Fontaine et al., 1990, Litt et al., 2009). Within the climate region of eastern Anatolia, Lake Van represents a first-order continental climate archive between the Black Sea, the Arabian Sea and the Red Sea (Roberts and Wright, 1993, Cullen and de Menocal, 2000, Lamy et al., 2006, Litt et al., 2012).
Lake Van, located on the high plateaus of eastern Anatolia in Turkey, has a surface area of 3522 km2, a volume of 607 km3, a maximum depth of 460 m, and extends for 130 km WSW–ENE (Kadioğlu et al., 1997). Due to its tectonic setting Lake Van is known to accumulate fluids from the sub-continental mantle (Kipfer et al., 1994, Tomonaga et al., 2011). It is the largest body of water in Turkey. The present lake level is at 1648 m asl. The lake water is highly alkaline, the pH reaches 9.8, and salinity is 22 g/kg (Kempe et al., 1991, Kaden et al., 2010). It is the largest soda lake of the world by volume. The southern shore is formed by the Bitlis massif (3500 m a.s.l.) mainly consisting in metamorphic rocks whereas the area north and west of the lake is dominated by the large Nemrut and Süphan volcanoes (Karaoglu et al., 2005, Tomonaga et al., 2011). Isolation of Lake Van is tentatively suggested to have resulted from the growth of Nemrut mountain prior to 400 ka—probably before 500 ka—in the hinge area between the Muş and Van pull-apart graben structures (Sumita and Schmincke, 2013a, Sumita and Schmincke, 2013b, Sumita and Schmincke, 2013c). Rivers within this basin discharge water and sediment into the lake, which has no outflow today.
The first sediment cores recovered in 1974 (Degens and Kurtman, 1978), were annually laminated (Kempe and Degens, 1978) and the first pollen analyses were published by Van Zeist and Woldering (1978). High-resolution hydrochemical, geochemical, geological and biological investigations of Lake Van were continued in 1990 during a German–Swiss expedition. The reconstruction of the frequency, duration and rate of climate changes during the last 12,500 years in eastern Anatolia was dated using an absolute chronology based on varve counting. Continuous records of varve thickness, geochemistry, δ18O, δ13C, and pollen allowed to distinguish several different climate phases (Landmann et al., 1996a, Landmann et al., 1996b, Lemcke and Sturm, 1997, Wick et al., 2003). Moreover, the first insights on the recent hydrological regime and the emission of geogenic fluids into Lake Van could be obtained (Kipfer et al., 1994). Ongoing expeditions to Lake Van in more recent years produced sediment-trap data that allowed for detailed reconstructions of the seasonal cycles for particles (Stockhecke et al., 2012) and biomarkers (Huguet et al., 2011).
An international team of scientists started to discuss the possibility of drilling the sedimentary archive of Lake Van in the frame of the International Continental Scientific Drilling Program (ICDP) in 2001. Based on the results of a site-survey (short cores and seismic survey) carried out in 2004 (Litt et al., 2009) and discussions during an ICDP-funded workshop held in Van in 2006, a full drilling proposal, submitted to ICDP in 2007, was accepted in the same year. The main objectives of this proposal and the PALEOVAN project are (see also Litt et al., 2009, Litt et al., 2012):
- i)
to recover and analyze a long continental paleoclimate record in a climatically sensitive semiarid region
- ii)
to reconstruct the dynamics of lake-level fluctuations and the hydrogeological regime of Lake Van
- iii)
to analyze the formation and age of Lake Van,
- iv)
to study and interpret organic-matter content and biomarkers as paleoenvironmental proxies,
- v)
to determine noble-gas concentrations in the pore water of the lake sediments to analyze terrestrial fluid transport,
- vi)
to analyze the temporal, spatial and compositional evolution of regional volcanism,
- vii)
to reconstruct the seismic and earthquake activities of the past, and
- viii)
to assess the microbiology and its activity in the sediments.
In this special issue we present first results of the deep drilling ICDP PALEOVAN project. This introductory chapter provides background information and an overview of the studies presented in this volume.
Section snippets
ICDP PALEOVAN drilling operations
Based on the seismic site survey (Cukur et al., 2013a, Cukur et al., 2013b, Cukur et al., 2014), five sites were defined in the initial drilling plan (Fig. 1) (Litt et al., 2009) from which two were finally drilled (Litt et al., 2011, Litt et al., 2012). Drilling operations were carried out during ten weeks from July 2 to August 23, 2010. DOSECC (Drilling, Observation and Sampling of the Earths Continental Crust. www.dosecc.com), as operator of the deep drilling, developed and assembled the new
Lithology and sedimentology of the composite profiles
Detailed litho- and chemostratigraphies of the Lake Van drill cores are presented in Stockhecke al. (in press). The study revealed that the AR section consists of ∼76% lacustrine carbonaceous clayey silt, ∼2% fluvial deposits, ∼17% volcaniclastic deposits and ∼5% gaps. The succession is basically continuous excluding two unconformities, a gap and a deformed unit, the latter also confirmed by seismic evidence (Cukur et al., 2013a, Cukur et al., 2013b). Stockhecke et al. (in press) present a
Chronology
The chronologies for both drill sites of the Lake Van sedimentary record encompassing 600 ka are described and discussed in detail in this volume by Stockhecke et al. (2014), Proxy records based on high-resolution XRF measurements (Ca/K ratio, details in Kwiecien et al., 2014), total organic carbon and color reflectance (TOC, b*; Stockhecke et al., in press) and pollen (details see Litt et al., 2014), were used for the age-model construction of the 174-m-long event-corrected (without tephra
Summary outlook: Lake Van as key record in the eastern Mediterranean
During the last decades paleoenvironmental information has accumulated from the eastern Mediterranean to improve our understanding of the climate dynamics at the transition between low- and high-latitude circulation systems (Tzedakis, 2007). However, suitable continuous and long continental records being chronologically well constrained and encompassing past glacial–interglacial cycles are rare. As demonstrated by the contributions in this special volume summarized above, the sediments of Lake
Acknowledgments
Recovery of the drill cores would not have been possible without the support of Turkish authorities and numerous members of Yuzuncu Yil University in Van, in particular of Ayşegül Feray Meydan. DOSECC provided the technical expertise to drill and recover the sediment cores under partly difficult and harsh conditions. ICDP and its staff supported the project from the planning to the execution phase. The entire PALEOVAN scientific team worked hard on the drilling barge, the shore-based laboratory
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2021, Palaeogeography, Palaeoclimatology, PalaeoecologyCitation Excerpt :Due to a strong gradient in annual precipitation, the vegetation in the northeastern region is characterized by high plateau steppe and oak-forest remnants, whereas the southwestern region is characterized by a Kurdo-Zagrosian oak forest (van Zeist and Woldring, 1978; Wick et al., 2003). A 219 m long sediment core was drilled at Ahlat Ridge (AR; Fig. 1) (ICDP Site 5034–2, 38.667°N, 42.669°E) at a water depth of 350 m in summer 2010 (Litt and Anselmetti, 2014). The lithostratigraphy of the core from Holocene to MIS4 is characterized by laminated and banded clayey silts, interrupted by volcaniclastic layers and turbidites.
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2020, Global and Planetary ChangeCitation Excerpt :Two obvious examples are those occupied the largest lakes in the country, Lake Van and Lake Tuz. Lake Van, in eastern Anatolia, is a high-level (1648 m above sea level) highly alkaline (pH up to 9.8) and saline lake in a tectonically generated basin; the world's largest soda lake by volume, it has accumulated sediments that provide a valuable climatic record from the last ~600,000 years (Litt and Anselmetti, 2014; Stockhecke et al., 2014a, 2014b). It is thought to have formerly been exorheic, with an outlet to the south-west that was blocked as a result of volcanic activity during the formation of the large stratovolcano ‘Nemrut’, located ~15 km to the west, probably during the Early Pleistocene (Degens et al., 1984).