Abstract. Lake Ohrid (Macedonia/Albania) is an ancient lake with unique biodiversity and a site of global significance for investigating the influence of climate, geological, and tectonic events on the generation of endemic populations. Here, we present oxygen (δ18O) and carbon (δ13C) isotope data from carbonate over the upper 243 m of a composite core profile recovered as part of the Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) project. The investigated sediment succession covers the past ca. 637 ka. Previous studies on short cores from the lake (up to 15 m, < 140 ka) have indicated the total inorganic carbon (TIC) content of sediments to be highly sensitive to climate change over the last glacial–interglacial cycle. Sediments corresponding to warmer periods contain abundant endogenic calcite; however, an overall low TIC content in glacial sediments is punctuated by discrete bands of early diagenetic authigenic siderite. Isotope measurements on endogenic calcite (δ18Oc and δ13Cc) reveal variations both between and within interglacials that suggest the lake has been subject to palaeoenvironmental change on orbital and millennial timescales. We also measured isotope ratios from authigenic siderite (δ18Os and δ13Cs) and, with the oxygen isotope composition of calcite and siderite, reconstruct δ18O of lake water (δ18Olw) over the last 637 ka. Interglacials have higher δ18Olw values when compared to glacial periods most likely due to changes in evaporation, summer temperature, the proportion of winter precipitation (snowfall), and inflow from adjacent Lake Prespa. The isotope stratigraphy suggests Lake Ohrid experienced a period of general stability from marine isotope stage (MIS) 15 to MIS 13, highlighting MIS 14 as a particularly warm glacial. Climate conditions became progressively wetter during MIS 11 and MIS 9. Interglacial periods after MIS 9 are characterised by increasingly evaporated and drier conditions through MIS 7, MIS 5, and the Holocene. Our results provide new evidence for long-term climate change in the northern Mediterranean region, which will form the basis to better understand the influence of major environmental events on biological evolution within Lake Ohrid.
Carbonates and diatoms are rarely deposited together in lake sediments in sufficient quantities for the oxygen isotope composition (δ18O) to be investigated simultaneously from both hosts. Here, δ18Ocarbonate are compared to δ18Odiatom data from the varved sediments of Nar Gölü, a closed lake in central Turkey, over the last 1710 years. Lake monitoring suggests carbonate is probably precipitated during May–June and δ18Ocarbonate is a proxy for regional water balance. Diatom activity is mainly weighted towards the spring. At times between ∼301 and 561 AD, while δ18Ocarbonate values are the highest for the entire 1710 year period, suggesting summer drought, δ18Ocorrected-diatom values are among the lowest. δ18Olakewater values estimated for the times of diatom growth and carbonate precipitation show large differences. We suggest this could be explained by increased snowmelt that formed a freshwater lid on the lake at the time of peak diatom growth. Increased snowmelt is also inferred ∼561–801 AD. From 801 AD to the present, precipitation is less winter-dominated, although increased snowmelt is inferred 921–1071 AD and in the latter part of the Little Ice Age (i.e. the mid to late 1800s AD). By combining oxygen isotope data from hosts that form in lakes at different times of the year, we show that such analyses can provide insights into palaeo-seasonality.
We aim to reconstruct the climatic and environmental conditions in the Valsequillo Basin during the deposition of the Valsequillo gravels between c. 40,000 and 8000 years ago, when large mega-fauna and potentially humans occupied the basin. Fossil freshwater (Fossaria sp. and Sphaeriidae (Family)) and terrestrial (Polygyra couloni, Holospira sp. and Cerionidae (Family)) snail shells from sections within the Barranca Caulapan were collected for oxygen and carbon stable isotope analysis. Oxygen and carbon isotopes in terrestrial and freshwater snail shells relate to local climatic parameters and environmental conditions prevailing during the lifetime of the snail. Whole shell isotope analysis showed that c. 35,000 years ago climate in the Valsequillo Basin was similar to the present day. Between c. 35,000 and 20,000 BP conditions became increasingly dry, after which conditions became wetter again, although this record is truncated. Intra-shell isotopic analyses show that the amount of precipitation varied seasonally during the late Pleistocene. If people did reach this part of the Americas in the late Pleistocene they would have experienced changing long-term and seasonal climatic conditions and would have had to adapt their life strategies accordingly.
Research Article| February 01, 2019 LIFE HISTORY, ENVIRONMENT AND EXTINCTION OF THE SCALLOP CAROLINAPECTEN EBOREUS (CONRAD) IN THE PLIO-PLEISTOCENE OF THE U.S. EASTERN SEABOARD ANDREW L.A. JOHNSON; ANDREW L.A. JOHNSON 1School of Environmental Sciences, University of Derby, Kedleston Road, Derby DE22 1GB, United Kingdom Search for other works by this author on: GSW Google Scholar ANNEMARIE M. VALENTINE; ANNEMARIE M. VALENTINE 1School of Environmental Sciences, University of Derby, Kedleston Road, Derby DE22 1GB, United Kingdom 2Current address: School of Geography and Environmental Science, Nottingham Trent University, Brackenhurst Campus, Southwell NG25 0QF, United Kingdom Search for other works by this author on: GSW Google Scholar MELANIE J. LENG; MELANIE J. LENG 3NERC Isotope Geoscience Facilities, British Geological Survey, Nicker Hill, Keyworth NG12 5GG, United Kingdom Search for other works by this author on: GSW Google Scholar BERND R. SCHÖNE; BERND R. SCHÖNE 4Institute of Geosciences, University of Mainz, Johann-Joachim-Becher-Weg 21, 55128 Mainz, Germany Search for other works by this author on: GSW Google Scholar HILARY J. SLOANE HILARY J. SLOANE 3NERC Isotope Geoscience Facilities, British Geological Survey, Nicker Hill, Keyworth NG12 5GG, United Kingdom Search for other works by this author on: GSW Google Scholar PALAIOS (2019) 34 (2): 49–70. https://doi.org/10.2110/palo.2018.056 Article history first online: 01 Feb 2019 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation ANDREW L.A. JOHNSON, ANNEMARIE M. VALENTINE, MELANIE J. LENG, BERND R. SCHÖNE, HILARY J. SLOANE; LIFE HISTORY, ENVIRONMENT AND EXTINCTION OF THE SCALLOP CAROLINAPECTEN EBOREUS (CONRAD) IN THE PLIO-PLEISTOCENE OF THE U.S. EASTERN SEABOARD. PALAIOS 2019;; 34 (2): 49–70. doi: https://doi.org/10.2110/palo.2018.056 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyPALAIOS Search Advanced Search ABSTRACT Plio-Pleistocene mass extinction of marine bivalves on the U.S. eastern seaboard has been attributed to declines in temperature and primary production. We investigate the relationship of growth rate in the scallop Carolinapecten eboreus to variation in these parameters to determine which contributed to its extinction. We use ontogenetic profiles of shell δ18O to estimate growth rate and seasonal temperature, microgrowth-increment data to validate δ18O-based figures for growth rate, and shell δ13C to supplement assemblage evidence of production. Post-larval growth started in the spring/summer in individuals from the Middle Atlantic Coastal Plain but in the autumn/winter in some from the Gulf Coastal Plain. Growth rate typically declined with age and was usually higher in summer than winter. Many individuals died in winter but the largest forms typically died in spring, possibly on spawning for the first time. No individuals lived longer than two years and some grew exceedingly fast overall, up to 60% more rapidly than any other scallop species (< 145.7 mm in a year). Faster growth was generally achieved by secreting more rather than larger microgrowth increments. Some very fast-growing individuals lived in settings of high production and low temperature. No individuals grew slowly under high production whereas most if not all grew slowly under 'average' production and low temperature. In that the rapid growth evidently enabled by high production would have afforded protection from predators, Plio-Pleistocene decline in production was probably contributory to the extinction ofC. eboreus. However, the negative impact of low temperature on growth under 'average' production suggests that temperature decline played some part. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Despite a growing body of work that uses diatom δ30Si to reconstruct past changes in silicic acid utilisation, few studies have focused on calibrating core top data with modern oceanographic conditions. In this study, a microfiltration technique is used to divide Southern Ocean core top silica into narrow size ranges, separating components such as radiolaria, sponge spicules and clay minerals from diatoms. Silicon isotope analysis of these components demonstrates that inclusion of small amounts of non-diatom material can significantly offset the measured from the true diatom δ30Si. Once the correct size fraction is selected (generally 2–20 μm), diatom δ30Si shows a strong negative correlation with surface water silicic acid concentration (R2 = 0.92), highly supportive of the qualitative use of diatom δ30Si as a proxy for silicic acid utilisation. The core top diatom δ30Si matches well with mixed layer filtered diatom δ30Si from published in situ studies, suggesting little to no effect of either dissolution on export through the water column, or early diagenesis, on diatom δ30Si in sediments from the Southern Ocean. However, the core top diatom δ30Si shows a poor fit to simple Rayleigh or steady state models of the Southern Ocean when a single source term is used. The data can instead be described by these models only when variations in the initial conditions of upwelled silicic acid concentration and δ30Si are taken into account, a caveat which may introduce some error into quantitative reconstructions of past silicic acid utilisation from diatom δ30Si.
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