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EARTH SCIENCE > PALEOCLIMATE > OCEAN/LAKE RECORDS > MICROFOSSILS

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  • A collaborative Italian/Australian marine geoscience research voyage to the George Vth Land sector of the East Antarctic continental margin was carried out between 11th February and 20th March, 2000, on board the of the RV Tangaroa. The cost of the expedition was shared jointly by the Italian and Australian National Antarctic Research Programs. Twenty four scientific personnel from 13 institutions participated in the expedition. The geophysical data collected includes a total of 1827 km of multi-channel seismic data and 562 km of Chirper sonar data. A total of 11 gravity cores, 28 piston cores, 18 surface grabs and 11 short trigger cores were collected on the voyage. Water profile (CTD) measurements and water samples were collected at nine stations and seabed bottom photographs were made at 11 stations. The expedition discovered and mapped a shelf sediment drift deposit covering about 400 km2 lying in an greater than 800m deep section of the George Vth basin west of the Mertz Glacier. It is a true 'drift' deposit, since these sediments exhibit a patchy distribution, large-scale bedforms, contain foreset bedding and display a depositional architecture indicative of contour-parallel sediment transport. A significant observation is that the drift thins to the north into an acoustically-transparent veneer; this observation implies that the drift is sourced from the outer continental shelf, with sediment being transported landwards, across the shelf and into an 850m deep inner shelf basin. The 'Mertz Drift' is over 35 m thick and core samples demonstrate that it is composed of laminated, anoxic, gelatinous olive green, silicious mud and diatom ooze (SMO). Preliminary shipboard counts of the laminae suggest a thickness of from 4 to 20mm, with a mean of about 7mm. While the lower sediments are laminated, there is a 20 to 50cm thick sandy drape at the surface over the whole of the drift. This suggests that a recent (late Holocene) change in the depositional environment has occurred, possibly related to changes in the extent of the nearby Mertz Glacier tongue, current regime and/or to the persistence of sea ice over the shelf area. Multi-channel seismic data show the occurrence of foreset beds at the shelf break, interpreted as having been deposited by ice streams that grounded on the outer shelf during glacial maxima. On the shelf, the seismic character of the seafloor exhibits highly reflective, parabolic reflectors suggestive of crystalline basement, cropping out at the seafloor. Northwards of these basement outcrops, the water depth increases to over 1,100 m which is the George Vth Basin. The basin coincides with an abrupt transition in seismic character from acoustic basement in the south to seaward (northeasterly) dipping reflectors. On the continental rise, seismic sections were taken across a contourite drift deposit and submarine canyon system in 2500 to 3500 m water depth. Piston cores were collected along the profile of one drift deposit which gave a preliminary Mid-Pliocene age to truncated strata that crop out on the drift's steeper lee side. These data will provide useful site-survey information in support of a proposal sent to the Ocean Drilling Program under the auspices of the SCAR-ANTOSTRAT project for drilling key sites along the Antarctic margin.

  • Preliminary data set contains details of cores processed (eg. sample name/interval, dry weights, reactions, notes) and the methodology used. The future data set will document diatoms observed and counted for each sample. This project also has links to ASAC project 1044 (ASAC_1044), the Wilkes Land Glacial History (WEGA) project. WEGA cores from both the continental shelf (PC7,11,12) and slope (PC19, 20, 21) region have been silica-selectively processed for their diatom content (see methodology file for details). The slides are mounted for quantitative assessment. Details of the cores that have been prepared are listed in the file WEGA_cores.csv in the downloadable dataset. Additional silica-selective slides of the surface sediments on the continental shelf were processed for quantitative assessment. Details of the samples and their locations are listed in the file sediment_samples.csv in the downloadable dataset. There have been no publications from the prepared slides as of the 15/04/02. An unpublished Honours Thesis uses limited diatom counts from slides prepared from PC 12. (Ms J. Erbs 2001). Title to be forthcoming. Any further enquiries referring to sample availability, curation, additional samples or publications arising from this material should be directed to Dr L. Armand. The fields in this dataset are: dry weight (gm) Sol A* reaction HCL reaction final dilution notes cm depth bottom depth latitude longitude core depth

  • The SCAR Spatial Data Model has been developed for Geoscience Standing Scientific Group (GSSG). It was presented to XXVII SCAR, 15-26 July 2002, in Shanghai, China. The Spatial Data Model is one of nine projects of the Geographic Information Program 2000-2002. The goal of this project is 'To provide a SCAR standard spatial data model for use in SCAR and national GIS databases.' Activities within this project include: 1. Continue developing the SCAR Feature Catalogue and the SCAR Spatial Data Model 2. Provide SCAR Feature Catalogue online 3. Creation and incorporation of symbology 4. Investigate metadata / data quality requirements 5. Ensure compliance to ISO TC211 and OGC standards Source: http://www.geoscience.scar.org/geog/geog.htm#stds Spatial data are increasingly being available in digital form, managed in a GIS and distributed on the web. More data are being exchanged between nations/institutions and used by a variety of disciplines. Exchange of data and its multiple use makes it necessary to provide a standard framework. The Feature Catalogue is one component of the Spatial Data Model, that will provide the platform for creating understandable and accessible data to users. Care has been taken to monitor the utility of relevant emerging ISO TC211 standards. The Feature Catalogue provides a detailed description of the nature and the structure of GIS and map information. It follows ISO/DIS 19110, Geographic Information - Methodology for feature cataloguing. The Feature Catalogue can be used in its entirety, or in part. The Feature Catalogue is a dynamic document, that will evolve with use over time. Considerable effort has gone into ensuring that the Feature Catalogue is a unified and efficient tool that can be used with any GIS software and at any scale of geographic information. The structure includes data quality information, terminology, database types and attribute options that will apply to any GIS. The Feature Catalogue is stored in a database to enable any component of the information to be easily viewed, printed, downloaded and updated via the Web.