Environmental changes in Syowa Station area of Antarctica during the last ,-** years inferred from organic components in lake sediment cores (original) (raw)
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Polarforschung, 1992
Dara on thc sedimcnt composition from four sediment cores, locatcd in a freshwater lake and in two marine busins of Bunger Hills. East Antarctica, are presented and discusscd in respcct of thcir paleoenvironmental implications. All investigated sedimcnts arc laruinated. They consist predominantly of algnc, mosscs and clastics, and exhibit vanous. somctimes vcry high contcnts in carbonatc, organic earbon and sulfur. Thc scdiment cornposition is Jargely influenced by the salinity of the watcr, by the degrec of iee coverage, by the supply of mclt watcr, and by thc glaciological and morphological conditions in the vicinity of thc lakes. Three individual sedimcnt units ean bc distinguished, each probably representing the same depositiona! time intervals at thc rcspectivc sampling sites. Transitions bctween the units ean be traced back to regional changes in the environmental conditions and thercfore providc information conceming the paleoenvironmcntal and paleoclimatical history in thc oasis. Near the Plcistocene/Holocenc boundary probably a marine transgression into the oasis occurrcd, resuhing in the Formation of marine busins. Presumably as a consequencc of thc postglacial isostatical uplift, parts of the basins were isolated from occan watcr and by meltwater inflow transformcd into fresh water lakes. Before reaching the recent environmcntal conditions, sampling sites in a large fresh water lake as weil as in a marine inlet have becn uuder anoxic conditions. presumably as a consequenee of a cooler climate than that of today. Zusammenfassung: Die Zusammensetzung von vier Sedimentkernen aus einem SÜßwassersee und zwei Meeresbecken der Bunger-Oase wird vorgestellt und in Bezug auf ihre Bedeutung für die Umweltgeschichte diskutiert. Alle untersuchten Sedimente sind laminiert. Sie sind hauptsächlich aus Algen, Moosen und klastischen Partikeln zusammengesetzt und zeigen unterschiedliche, z.T; sehr hohe Gehalte an Karbonat, organischem Kohlenstoff und Schwefel. Die Sedimentzusammensetzung wird wesentlich vom Salzgehalt des Wassers, vom Grad der Eisbedeckung. vom Eintrag an Schmelzwasser und von den glaziologischen und morphologischen Verhältnissen am Ufer gesteuert. Es lassen sich drei Sedimenteinheiten unterscheiden, die an den einzelnen Probcnnahmcstationen wahrscheinlich jeweils gleiche Ablagerungszeiträume umfassen. Übergänge zwischen den Sedimenteinheiten sind auf Veränderungen der Umweltbedingungen zurückzuführen. Die Sedimentabfolgen liefern daher Informationen Über die Entwicklung der Umweltbedingungen und des Klimas im Bereich der Oase. Nahe der Pleistozän/Holozän-Grenze führte wahrscheinlich eine marine Transgression zur Bildung von Meeresbecken innerhalb der Oase. Als Folge der nacheiszeitlichen isostatischen Landhebung wurden vermutlich Teile der Meeresbecken vom Ozean isoliert und durch den Eintrag von Schmelzwasser in Süßwasserseen überführt. Bevor die heutigen Umweltbedingungen erreicht wurden, befanden sich Probennahmestationen in einem großen Süßwassersee und in einem Meeresann unter anoxischcn Bedingungen. Dies war vermutlich die Folge eines kühleren Klimas als heute.
Particle size distribution Long Lake Organic carbon a b s t r a c t Sediments from the pristine lakes of ice-free regions of Antarctica are a great source for proxies to reconstruct the effect of past-climate on the lake evolution and its response to Antarctic climate. A 50 cm long sediment core retrieved from Long Lake, a periglacial lake of Schirmacher Oasis in Dronning Maud Land was measured for elemental (C%, N% and C/N), isotopic (d 13 C, d 15 N) and particle size (sand-silt-clay percent) variation. The radiocarbon dated core spanning the last 48 cal ka BP has been deciphered for the lake's response to Antarctic climate. The C/N ratio (atomic ratio) predominantly indicates that the productivity has been autochthonous for majority of the down-core while the top 0e3 cm indicates that there has been addition of terrestrial organic matter into the lake system owing to longer ice-free conditions. The organic carbon shows significantly lower values (0.2%) throughout the glacial period and major part of the Holocene while the core-top values are consistent with the presence of a microbial mat which is reflected as higher organic carbon (12%). The d 13 C and d 15 N range from À33 to À9‰ and 2 e18‰, respectively. The isotopic signals vary marginally for the entire glacial period (48e8 cal ka BP) suggesting an intense cold period. The gradual increase in C/N ratio, sand content and d 13 C and decrease in d 15 N beginning at about 6 cal ka BP suggest that the Long Lake experienced longer ice-free conditions owing to sustained warmer Holocene conditions suggesting that the ice-cover over the Long Lake persisted well through early-Holocene. The sand and silt percent shows inverse correlation likely reflecting the warmer and colder conditions. The Holocene is characterised by higher sand content owing to melting of ice due to warmer conditions. The Long Lake's response to Antarctic climate is reflected in its response to the ice-cover conditions which regulates the productivity and sedimentation in the lake system.
Quaternary Science Reviews, 2006
We reconstruct terrestrial and freshwater environments of the last two Quaternary interglacials in coastal east Antarctica by examining multi-proxy evidence in a lake sediment core. The record, from Progress Lake in the Larsemann Hills consists of two discrete sediment units. The lower unit contains the first known evidence of Antarctic coastal environments during a previous interglacial, likely to be MIS5e. Biogeochemical, biological and sedimentological climate proxies revealed a productive biological community and an active hydrological regime, consistent with the warmer conditions detected in continental ice cores at this time. The diatom assemblage was similar to that currently found in the sub-and maritime-Antarctic biome and included some sub-Antarctic endemic taxa that have not previously been reported from east Antarctica. This suggests southward expansion of the sub-Antarctic diatom biome during MIS5e. Mosses were also present in the lake or the catchment but are rare in the region today. Two discrete periods of enhanced productivity show that the MIS5e environment was not stable. MIS5e ended abruptly with a rapid transition to glacial conditions, the lake was covered by a layer of firnified snow and ice, and phototrophic biological activity ceased for a period of c. 90,000 years. The upper unit was deposited in MIS1 after 3470-3687 cal yr BP after phototrophic biological production resumed. Lower species diversity, pigment production, an Antarctic continental diatom assemblage and an absence of moss layers suggest cooler conditions during MIS1. r
Paleoceanography, 2007
1] The 18S ribosomal DNA (rDNA) isolated from sulfidic Holocene sediments and particulate organic matter in the water column of the stratified Small Meromictic Basin (SMB) in Ellis Fjord (eastern Antarctica) was analyzed to identify possible biological sources of organic matter. Previous work had shown that the sediments contained numerous diatom frustules and high contents of a highly branched isoprenoid (HBI) C 25:2 alkene (which is a specific biomarker of certain species of the diatom genera Navicula, Haslea, Pleurosigma, or Rhizosolenia), so we focused our search on preserved fossil 18S rDNA of diatoms using sensitive polymerase chain reaction (PCR) approaches. We did not find diatom-derived fossil 18S rDNA using general eukaryotic primers, and even when we used primers selective for diatom 18S rDNA, we only identified a Chaetoceros phylotype, which is known to form cysts in the SMB but is not a likely source of the C 25:2 HBI. When we used PCR/denaturing gradient gel electrophoresis methods specific to phylotypes within the HBI-biosynthesizing genera, we were able to identify three phylotypes in the sediments related to HBI-producing strains of the genera Haslea and Navicula. The ancient DNA data thus provided a limited, but valuable, view of the diversity of late Holocene primary producers with a particular bias to specific components of the biota that were better preserved such as the Chaetoceros cysts. This use of paleogenetics also revealed unexpected possible sources of organic matter such as novel stramenopiles for which no specific lipid biomarkers are known and thus would not have been identified based on traditional lipid stratigraphy alone. Citation: Coolen, M. J. L., J. K. Volkman, B. Abbas, G. Muyzer, S. Schouten, and J. S. Sinninghe Damsté (2007), Identification of organic matter sources in sulfidic late Holocene Antarctic fjord sediments from fossil rDNA sequence analysis, Paleoceanography, 22, PA2211,
Polar Science, 2018
Three sediment cores collected from GL-1, V-1(Vetehiya) and L-6 lakes of Schirmacher Oasis, East Antarctica were studied for sediment components (sand, silt, clay, total organic carbon, total nitrogen, TOC/TN ratio and biogenic silica), major elements (Aluminium, Iron and Manganese) and trace metals (Chromium, Zinc, Lead, Cobalt, Cadmium and Nickel). High sand content in all the three cores revealed the release of coarser sediments through mechanical weathering in fluvio-glacial environment. Relatively, high biogenic silica along with high total organic carbon associated with high clay in some sections indicated high primary productivity due to the warming and exposure of the lakes to the ice-melt water influx. TOC/TN ratio for all the cores was found to be < 10 which indicated that the major source of organic matter was autochthonous. Metals were found to be strongly associated with clay and organic carbon in core V-1, with sand and clay in core L-6 while, with silt and organic matter in core GL-1 indicating their role in regulating the distribution of metals. Cadmium in lake GL-1 was found to be associated with total organic carbon and showed largely biogenic origin, while, Cd and Pb in lakes L-6 and V-1 were found to be of anthropogenic origin. All the other metals showed signatures of lithogenic origin.
Sedimentological and stable-isotope evolution of lakes in the Vestfold Hills, Antarctica
Palaeogeography, Palaeoclimatology, Palaeoecology, 1991
Bird, M.I., Chivas, A.R., Radnell, C.J. and Burton, H.R., 1991. Sedimentological and stable-isotope evolution of lakes in the Vestfold Hills, Antarctica. Palaeogeogr., Palaeoclimatol., Palaeoecol., 84: 109-130.
1998
Sediments from the Antarctic continental margin may provide detailed palaeoenvironmental records for Antarctic shelf waters during the late Quaternary. Here we present results from a palaeoenvironmental study of two sediment cores recovered from the continental shelf ofT Mac. Robertson Land, East Antarctica. These gravity cores were coll ected approximately 90 km apart from locations on the inner and outer shelf. Both cores are apparently undisturbed sequences of diatom ooze mixed with fine, quartz-rich sand. Core stratigraphies have been established from radiocarbon analyses of bulk organic carbon. Down-core geochemical determinations include the lithogenic components Al and Fe, biogenic components opal and organic carbon, and palaeo-redox proxies Mn, Mo and U. We use the geochemical data to infer past variations in the deposition of biogenic and lithogenic materials, and the radiocarbon dates to estimate average sediment accumulation rates. The Holocene record of the outer-shelf core suggests three episodes of enhanced diatom export production at about 1.8,3.8 and 5.5 ka BP, as well as less pronounced bloom episodes which occurred over a shorter period. Average sediment accumu lation rates at this location range from 13.7 cm ka 1 in the late Pleistocene-early Holocene to 82 cm ka I in the late Holocene, and suggest that the inferred episodes of enhanced biogenic production lasted 100-1000 years. In contrast, data for the inner-shelf core suggest that there has been a roughly constant proportion of biogenic and lithogenic material accumulating during the middle to late Holocene, with a greater proportion of biogenic material relative to the outer shelf. Notably, there is an approximately 7-fold increase in average sediment accumulation rate (from 24.5 to 179 cm ka I) at this innershelf location between the middle and late Holocene, with roughly comparable increases in the mass accumulation rates of both biogenic and lithogenic material. This may represent changes in sediment transport processes, or reflect real increases in pelagic sedimentation in this region during the Holocene. Our results suggest quite different sedimentation regimes in these two shelflocations during the middle to late Holocene.
Annals of Glaciology, 1998
Eight sediment gravity cores, collected from the joides and Drygalski basins, were analysed in order to understand late Pleistocene-Holocene biogenic flux changes in the Ross Sea, driven by paleoenvironmental changes. Core lithologies and magnetic-susceptibility depth profiles were used for core logging and stratigraphic correlation. Nineteen AMS radiocarbon dates of bulk organic matter were used to set chronological constraints and calculate sediment accumulation rates. These rates, which vary from 1.4-38 cm ka−1. were used to obtain the burial fluxes of biogenic components. The highest fluxes occur in the deepest parts of the basins (TOC, 0.05-0.2 g cm−2ka−1; biogenic silica, 1.5-5 g cm−1ka−1), where as topographic highs show the lowest values (TOC, 0.01-0.1 g cm−2ka−1; biogenic silica, 0.1-1.4 g cm−2ka−1). Dramatic changes in both physical properties and fluxes record the establishment of open marine-sedimentation conditions which occurred first in the joides basin and then, with...
Holocene Climate Variability from Lake Sediment Core in Larsemann Hills, Antarctica
Journal Geological Society of India, 2011
A sediment core (L2) from Larsemann Hills, Antarctica was analyzed for Biogenic Silica (BSi), Sand (%) and Total Organic Carbon (TOC). The 78 cm core length represents the time span of ~8.3 cal ka BP. The values of BSi from the core show prominent high productivity from ~8.3 to ~6 cal ka BP in comparison to less productivity in mid-late Holocene (~6 cal ka BP to recent). Moreover, high sand (%) infers the glacio-fluvial deposition from ~8.3 to ~5 cal ka BP TOC shows little variation through out the core, except in the upper ~10 cm (~4 cal ka BP) part wherein it is comparatively high. The increased TOC in the upper part of the core possibly indicates presence of algal mat due to exposure of the lake to the ice free (glacier free) conditions.