Analysis of a fragmentary diatom record from Lake Van (Turkey) reveals substantial lake-level variability during previous interglacials MIS7 and MIS5e

North, Sam; Stockhecke, Mona; Tomonaga, Yama; Mackay, Anson W.

doi:10.1007/s10933-017-9973-z

Cited by 12 publications

(18 citation statements)

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“…In contrast, both pH and alkalinity may have even been lower during at least one period of intense dolomite formation. In the entire studied profile only one short interval (equivalent of 126–128 ka BP) contains diatoms (North et al, ). The same sediments also contain a substantial concentration of dolomite (Figure ).…”

Section: Evaluating Factors Controlling Dolomite Formationmentioning

confidence: 99%

“…Instead, it provides a unique opportunity for testing the envelope of environmental conditions assumed essential for dolomite formation. If juxtaposed with environmental proxies reflecting regional and local hydrological conditions (Kwiecien et al, ; Litt et al, ; North et al, ; Pickarski, Kwiecien, Djamali, et al, ; Pickarski, Kwiecien, Langgut, et al, ; Pickarski & Litt, ; Randlett et al, ; Stockhecke, Sturm, et al, ; Tomonaga et al, ) (Figure ), the dolomite occurrence is incompatible with the commonly accepted hypothesis of evaporitic conditions driving its formation. Our high‐resolution dolomite concentration data (Figure ), presented on the common Lake Van age model (Stockhecke, Kwiecien, et al, ), suggest that most of the dolomite‐rich intervals coincide with sediments deposited during a high lake level and generally wetter conditions.…”

Section: Introductionmentioning

confidence: 99%

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Controls on Cyclic Formation of Quaternary Early Diagenetic Dolomite

McCormack

Bontognali

Immenhauser

et al. 2018

Geophysical Research Letters

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The origin of sedimentary dolomite and the factors that control its formation within the geological record remain speculative. In most models, dolomite formation is linked to evaporative conditions, high water temperature, increasing Mg/Ca ratio, increasing alkalinity, and high amounts of biomass. Here we challenge these archetypal views, by documenting a case example of Quaternary dolomite which formed in Lake Van at constantly low temperature (<4°C) and without direct control of the latter conditions. Dolomite occurs within highstand sediments related to suborbital climate variability (Dansgaard‐Oeschger cycles). We propose that dolomite precipitation is a product of a microbially influenced process, triggered by ecological stress, resulting from reventilation of the water‐sediment interface. Independently from the validity of this hypothesis, our results call for a reevaluation of the paleoenvironmental conditions often invoked for early diagenetic dolomite‐rich intervals within sedimentary sequences and for caution when interpreting time series of subrecent lacustrine carbonates.

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Section: Evaluating Factors Controlling Dolomite Formationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Controls on Cyclic Formation of Quaternary Early Diagenetic Dolomite

McCormack

Bontognali

Immenhauser

et al. 2018

Geophysical Research Letters

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“…(a) Isotopic composition of the NGRIP ice core (NGRIP, 2004;Steffensen et al, 2008;Svensson et al, 2008;Wolff et al, 2010) and a synthetic Greenland record (GL T _syn) (Barker et al, 2011). Sedimentary proxies from Lake Van include (b) the XRF Ca / K ratio (Kwiecien et al, 2014), (c) arboreal pollen and Quercus pollen percentage Pickarski et al, 2015a, b;Pickarski and Litt, 2017), (d) porewater salinity plotted against depth in metres' composite below lake floor (mcblf; Tomonaga et al, 2017), (e) biomarker Archaeol and Caldarchaeol Ecometric (ACE) index (Randlett et al, 2017) and (k) lithologies with genetic interpretations related to lake level variability as a coloured bar (simplified according to Stockhecke et al, 2014a) and major lake level variations (Stockhecke et al, 2014a;Tomonaga et al, 2017) in metre above/below present lake level (mapll/mbpll). ( Fig.…”

Section: Ostracod Valve Oxygen and Carbon Isotopymentioning

confidence: 99%

“…Amount and number of noded Limnocytherinae species valves relative to Lake Van palaeoenvironmental proxy records. Sedimentary proxies from Lake Van include (a) arboreal pollen and Quercus pollen percentage Pickarski et al, 2015a, b;Pickarski and Litt, 2017), (b) porewater salinity plotted against depth in metres' composite below lake floor (mcblf;Tomonaga et al, 2017), (c) biomarker Archaeol and Caldarchaeol Ecometric (ACE) index(Randlett et al, 2017) and (h) lithologies with genetic interpretations related to lake level variability as a coloured bar (simplified according toStockhecke et al, 2014a) and major lake level variations(Stockhecke et al, 2014a;Tomonaga et al, 2017). (d-f) Number of nodes in percent.…”

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confidence: 99%

Ostracods as ecological and isotopic indicators of lake water salinity changes: the Lake Van example

et al. 2019

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Abstract. Ostracods are common lacustrine calcitic microfossils. Their faunal assemblage and morphological characteristics are important ecological proxies, and their valves are archives of geochemical information related to palaeoclimatic and palaeohydrological changes. In an attempt to assess ostracod ecology (taxonomic diversity and valve morphology) combined with valve geochemistry (δ18O and δ13C) as palaeosalinity indicators, we analysed sedimentary material from the International Continental Scientific Drilling Program (ICDP) Ahlat Ridge site from a terminal and alkaline lake, Lake Van (Turkey), covering the last 150 kyr. Despite a low species diversity, the ostracod faunal assemblage reacted sensitively to changes in the concentration of total dissolved salts in their aquatic environment. Limnocythere inopinata is present throughout the studied interval, while Limnocythere sp. A is restricted to the Last Glacial period and related to increased lake water salinity and alkalinity. The presence of species belonging to the genus Candona is limited to periods of lower salinity. Valves of Limnocytherinae species (incl. L. inopinata) display nodes (hollow protrusions) during intervals of increased salinity. Both the number of noded valves and the number of nodes per valve appear to increase with rising salinity, suggesting that node formation is related to hydrological changes (salinity and/or alkalinity). In contrast to Lake Van's bulk δ18O record, the δ18O values of ostracod valves do record relative changes of the lake volume, with lower values during high lake level periods. The δ13C values of different species reflect ostracod habitat preferences (i.e. infaunal vs. epifaunal) but are less sensitive to hydrological changes. However, combined with other proxies, decreasing Holocene δ13C values may indicate a freshening of the lake water compared to the low lake level during the Last Glacial period. The Lake Van example underscores the significance and value of coupling ostracod ecology and valve geochemistry in palaeoenvironmental studies of endorheic lake basins.

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“…Ostracod valves are almost absent in the Ahlat Ridge sediments deposited during the early MIS 5e (124 -133 ka BP; Fig. 2 j), a period in which the lake level probably rose sufficiently to establish a short-lived outflow (Stockhecke et al, 2014a;Tomonaga et al, 2017;North et al, 2017). Apparently, this has led to a larger and/or more oxygen-depleted suboxic/anoxic water body compared to other highstand periods, preventing or Limnocythere sp.…”

Section: Ostracod δ 18 O: Palaeoenvironmental Implications and Comparmentioning

confidence: 96%

Ostracods as ecological and isotopic indicators of lake water salinity changes: The Lake Van example

McCormack¹,

Viehberg²,

Akdemi̇r³

et al. 2019

Preprint

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Abstract. Ostracods are common lacustrine calcitic microfossils. Their faunal assemblage and morphological characteristics are important ecological proxies, while their valves are archives of geochemical information related to palaeoclimatic and palaeohydrological changes. In an attempt to assess ostracod ecology (taxonomic diversity and valve morphology) combined with valve geochemistry (&#948;18O and &#948;13C) as palaeosalinity indicators, we analysed material from terminal and alkaline Lake Van (Turkey) covering the last 150&#8201;kyr. Despite a low species diversity, the ostracod faunal assemblage reacted sensitive to changes in the concentration of total dissolved salts in their aquatic environment. Limnocythere inopinata is present throughout the studied interval, while Limnocythere sp. A is restricted to the Last Glacial period and related to increased lake water salinity and alkalinity. The presence of species belonging to the genus Candona is limited to periods of lower salinity. Valves of limnocytherinae species (incl. L. inopinata) display nodes (hollow protrusions) during intervals of increased salinity. Both the amount of noded valves and the number of nodes per valve appear to increase with rising salinity, suggesting that node formation is related to hydrological changes (salinity and/or alkalinity). In contrast to Lake Van's inorganic &#948;18O record, the &#948;18O values of ostracod valves do record relative changes of the lake volume, with lower values during high lake level periods. The &#948;13C values of different species reflect ostracod habitat preferences (i.e., infaunal versus epifaunal) but are less sensitive to hydrological changes. However, combined with other proxies, decreasing Holocene &#948;13C values may indicate a freshening of the lake water compared to the low lake level during the Last Glacial period. The Lake Van example underscores the significance and value of coupling ostracod ecology and valve geochemistry in palaeoenvironmental studies of endorheic lakes basins.

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Analysis of a fragmentary diatom record from Lake Van (Turkey) reveals substantial lake-level variability during previous interglacials MIS7 and MIS5e

Cited by 12 publications

References 77 publications

Controls on Cyclic Formation of Quaternary Early Diagenetic Dolomite

Controls on Cyclic Formation of Quaternary Early Diagenetic Dolomite

Ostracods as ecological and isotopic indicators of lake water salinity changes: the Lake Van example

Ostracods as ecological and isotopic indicators of lake water salinity changes: The Lake Van example

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