125 research outputs found
Rock weathering observations of surface sediment in the Australian Antarctic Territory
No full textProgress Code: completedStatement: Schmidt Hammer results from a collection of sites (817-819, 821, 823, 832-834, 838) from the early part of the 2016-17 season were not consistent with nearby results from earlier or later seasons and so are not presented in this dataset. These are available on request to Duanne White if required.<b>Purpose</b><br/>Rock weathering observations were collected to provide a semi-quantitative measure of the surface exposure age of glacial and other sediments. This was used to map out the extent of glacial advances and to aid in sampling and interpreting cosmogenic exposure ages collected across the region.Metadata for Rock Weathering observations collected by field parties on AAS 4318 ‘CADAGIA’ geological surveys.<br/><br/>Rock weathering observations were collected to provide a semi-quantitative measure of the exposure age, to map out the extent of glacial advances and to aid in sampling and interpreting cosmogenic exposure ages. Visual estimates (Moriwaki index values) were collected at most sites visited, with Schmidt Hammer measurements collected where time and a sufficient abundance of clasts were available (i.e. greater than 20 boulders bigger than 30 cm diameter).<br/><br/>Measurements were conducted by several different field scientists across three distinct field seasons (Duanne White, Steven Phipps, Marcello Blaxell and David Small). Also included in the dataset are a few measurements conducted by Duanne White during 2003 as part of the PCMEGA expedition. Each field scientist was trained by Duanne White, either at Australian-based glacial sediments (Marcello Blaxell and Steven Phipps) or at Windmill Islands (David Small), following the same set of written guidelines. Visual assessments (i.e. Moirwaki index values) were also vetted via field photographs by Duanne White. Schmidt hammer measurements collected by different field parties were compared and checked for reproducibility. <br/><br/>Main site info sheets:<br/><br/>Date SampleID Lat Long Locality <br/><br/>All lat/longs are recorded relative to the WGS 84 datum.<br/><br/>Site elevation (metres)<br/><br/>Handheld GPS, relative to WGS 84. 2015/16 used a barometric corrected GPS (Etrex 300), while other seasons used a standard GPS.<br/><br/>SiteID<br/><br/>Name used to identify site in respective field book.<br/><br/>Schmidt Hammer measurements<br/><br/>Schmidt hammer measurements were conducted with the same Proceq N-34 hammer across each of the three seasons that data was collected. Measurements were primarily taken as a semi-quantitative measure of exposure age on glacial deposits. <br/><br/>Measurements are recorded in R (rebound) values. Higher rebound values represent less weathered rock, and thus typically a younger deposit. However, there are likely substantive differences in weathering rates across the region (e.g. with altitude/temperature, salinity, water availability etc) so comparing measurements from different localities should be done with care.<br/><br/>Landform<br/><br/>Where recorded, identifies the landform on which the Schmidt hammer or weathering measurement or sample was collected.<br/><br/>Lithology <br/><br/>Rock type that the Schmidt hammer measurements were conducted on. Typically a mix of felsic metamorphic lithologies, but occasionally others depending on what was present at the site.<br/><br/>Type <br/><br/>What the Schmidt hammer measurements were conducted on. Typically the top (horizontal) surface of erratics greater than 30 cm in diameter, with no obvious fractures or hollows. Each boulder was measured once, with boulders selected randomly from within ~50 m of the GPS measurement. At some sites bedrock was also measured.<br/><br/>Summary statistics <br/><br/>Mean, standard deviation, standard error and the count (how many) measurements were conducted at each site. <br/><br/>Rebound 1-40 record the rebound measurements at each site.<br/><br/>Moriwaki Clast weathering:<br/><br/>Similar to the Schmidt hammer measurements, this is a (very) semi-quantitative way measuring the relative exposure age on glacial deposits. See White et al. 2009 Quaternary Research for reference on how this has been applied previously.<br/><br/>The DW0-4 represent the proportion (%) of clasts (usually glacial erratics) at each site that fall into each moriwaki index value: <br/> <br/><br/><br/>DW0: a fresh clast<br/>DW1: a stained clast without cavernous weathering, ventifact and crumbling<br/>DW2: a stained, cavernously weathered and/or wind-faceted, not crumbled clast<br/>DW3: a distinctly stained and somewhat crumbled clast<br/>DW4: a strongly stained and crumbled clast<br/><br/>Previous workers have used the original version of the Moriwaki index, whereby the largest 100 clasts on the surface of a 10 x 10 m quadrangle are individually assigned a MDoW value, according to the following scheme:<br/><br/>The Moriwaki Degree of Weathering (MDoW) is then assigned to each deposit using the following formula:<br/><br/>DW = N0*0 + N1*1 + N2*2 + N3*3 + N4*4<br/><br/>where Nx is equal to the number of DWX clasts in each count. However, this method is time consuming and not suitable for mapping large areas during a relatively short field campaign. Thus, the proportion of clasts in each weathering category was visually estimated (see White et al., 2009). Overall, a fresh (recent) deposit will record a MDoW of less than 100. Very weathered deposits are typically 300 or greater.<br/><br/>Lithology <br/><br/>Rock types that were present in the glacial sediments that the Moriwaki measurements were conducted on. Typically a mix of all lithologies at each site, but occasionally specific lithology depending on what was present at the site. Experience in East Antarctic glacial sediments indicates that these are generally quite well mixed, and that the Moriwaki index values are not strongly influenced by site to site differences in lithology (White et al., 2009, Quaternary Research).<br/><br/>Felsic gneiss, Mafic Gneiss Dolerite etc…<br/><br/>Where recorded, a visual estimate of the volumetric fraction that each lithology at the site … i.e. the rock type that the Moriwaki index value was recorded on. <br/><br/>For the remainder of the sites (i.e. where these observations were not explicitly recorded) the rock types were typically a mix of ~ 50-75% felsic gneiss, 20-40 % mafic gneiss, 0-20 % quartzite, and 0-20% other high grade metamorphic or igneous lithologies (e.g. granite, dolerite, garnet-rich gneiss). Notable exceptions to this typical ‘East Antarctic’ lithological mix include sites 567 and 569 at Cape Jones, where the glacial sediments were composed of ~50 % lightly metamorphosed red sandstone, and the Edisto moraines at Bunger Hills (sites 587-590, 816-819, 832-833) which had a large granitic and dolerite component
GIS data of geomorphic features at Beaver Lake-Amery Oasis
No full textProgress Code: completedStatement: Field mapping was conducted across the region during the 2003-04 season. Distances between traverse lines varied averaged about ~2km, but vary from 1km to 10km. These areas are specified in the data.
Mapping was performed on a rectified SPOT-5 2.5m resolution image taken in January 2004, with 1974 and 1995 stereo colour aerial photography used as supplement where SPOT data were snow covered or ambiguous. Air photo runs include: Film CAS/C 8574 run 23, 24 and 27; CAS/C 8575 run 26; CAS/C 8572 run 25 and ANT 1059 run 7-10.
Features were digitised on the SPOT image using ARCGIS 9, and are accurate to within 20-50m. Relative age for the features is constrained by surface weathering parameters and stratigraphic relationships. Absolute ages for mid-late pleistocene (less than 1Ma) features are derived from cosmogenic exposure age dating to within ~10-20%. Ages prior to this period are constrained by reference to the Pagodroma Group, dated using diatom stratigraphy. Dating reliability is specified for each feature within the attribute tables.The data include a 1:10,000 scale map of the surfical glacial and periglacial features of the Amery Oasis, East Antarctica. Features currently include:<br/><br/>areas covered by exposed bedrock, fluvial sediments and moraine<br/>moraine ridges<br/>streams (flowing during the 2003/04 season)<br/>watercourses<br/>lakes<br/>cosmogenic exposure ages<br/>degree of weathering<br/><br/>and includes areas of glaciers, glacial bedforms, scree and patterned ground.<br/><br/>Rock samples are currently held by Duanne White (as at 2015-09-23), but will eventually be archived at Geoscience Australia
Age-related environmental gradients influence invertebrate distribution in the prince Charles mountains, east Antarctica
Full text linkThe potential impact of environmental change on terrestrial Antarctic ecosystems can be explored by inspecting biodiversity patterns across large-scale gradients. Unfortunately, morphology-based surveys of Antarctic invertebrates are time-consuming and limited by the cryptic nature of many taxa. We used biodiversity information derived from high-throughput sequencing (HTS) to elucidate the relationship between soil properties and invertebrate biodiversity in the Prince Charles Mountains, East Antarctica. Across 136 analysed soil samples collected from Mount Menzies, Mawson Escarpment and Lake Terrasovoje, we found invertebrate distribution in the Prince Charles Mountains significantly influenced by soil salinity and/or sulfur content. Phyla Tardigrada and Arachnida occurred predominantly in low-salinity substrates with abundant nutrients, whereas Bdelloidea (Rotifera) and Chromadorea (Nematoda) were more common in highly saline substrates. A significant correlation between invertebrate occurrence, soil salinity and time since deglaciation indicates that terrain age indirectly influences Antarctic terrestrial biodiversity, with more recently deglaciated areas supporting greater diversity. Our study demonstrates the value of HTS metabarcoding to investigate environmental constraints on inconspicuous soil biodiversity across large spatial scales.Paul Czechowski, Duanne White, Laurence Clarke, Alan McKay, Alan Cooper, Mark I. Steven
East Antarctic ice sheet geometries during the past 30 ka: timing of retreat、forcings and opportunities for new research
Full text link第4回極域科学シンポジウム
特別セッション：[S] 南極研究の将来展望―第Ⅸ期6か年計画策定に向けて
11月13日（水） 国立極地研究所 ２階大会議室conference objec
Geomorphic map of Rauer Group
No full textProgress Code: completedStatement:
No specific issues with the data or data collection, but note that the field survey density is much greater in the north (where most islands were visited) than the south (mostly airphoto reconnaissance).The GIS data was produced following a three week expedition to the region onboard the Alfred Wegener Institute research vessel Polarstern (cruise ANT-XXIII/9) in 2007, and subsequent analysis of aerial and field photography on return to Australia. The results are discussed in the expedition report and the following manuscripts. Cosmogenic exposure samples that will further constrain the age of ice retreat in the region are expected to be finalised during 2012. The data are intended to accompany existing polygons that detail the lakes, bedrock and penguin breeding sites (i.e. areas of biogenic sediment) from the area that are already present in the AAD digital database.<br/><br/>See the word document in the download file for further information
East Antarctic ice sheet geometries during the past 30 ka: timing of retreat、forcings and opportunities for new research
No full textElemental composition of sediment core 1430, Peterson Inlet, Windmill Islands
No full textThis data set comprises elemental data obtained from sediment samples of core 1430 (also termed PG1430). Detailed descriptions of the site and core lithology are given in Cremer et al. (2003). Geochemical analyses were performed on freeze-dried and ground material. Total organic carbon (TOC) and total inorganic carbon (TIC) were analyzed with a DIMATOC 200 analyzer (DIMATEC Corp.). Nitrogen (N wt%) and sulphur (S wt%) were measured with a Vario Mircrocube (Elementar). Inorganic elemental composition reported here was analysed with an ITRAX µXRF core scanner (Cox Analytical Systems, Sweden) with a Cr X-ray tube (settings: 30 kV, 55 mA). To convert the semi-quantitative XRF counts obtained with the ITRAX core scanner to absolute elemental concentrations reference samples with known elemental compositions were analyzed along with each batch of samples and absolute element concentrations were calculated based on linear calibration curves for elements with a Pearson correlation coefficient R² >0.65. The data set is a supplement to the manuscript "Rapid relative sea-level fall during the mid-Holocene in the Windmill Islands, East Antarctica" submitted for publication in the journal Quaternary Science Reviews by Small et al
Elemental composition of sediment core 1433, Browning Bay, Windmill Islands
No full textThis data set comprises elemental data obtained from sediment samples of core 1433 (also termed PG1433). Detailed descriptions of the site and core lithology are given in Cremer et al. (2003). Geochemical analyses were performed on freeze-dried and ground material. Total organic carbon (TOC) and total inorganic carbon (TIC) were analyzed with a DIMATOC 200 analyzer (DIMATEC Corp.). Nitrogen (N wt%) and sulphur (S wt%) were measured with a Vario Mircrocube (Elementar). Inorganic elemental composition reported here was analysed with an ITRAX µXRF core scanner (Cox Analytical Systems, Sweden) with a Cr X-ray tube (settings: 30 kV, 55 mA). To convert the semi-quantitative XRF counts obtained with the ITRAX core scanner to absolute elemental concentrations reference samples with known elemental compositions were analyzed along with each batch of samples and absolute element concentrations were calculated based on linear calibration curves for elements with a Pearson correlation coefficient R² >0.65. The data set is a supplement to the manuscript "Rapid relative sea-level fall during the mid-Holocene in the Windmill Islands, East Antarctica" submitted for publication in the journal Quaternary Science Reviews by Small et al
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