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  • ACRES Update, Issue 24, July 2001 STAR Service shortens delivery time ACRES Poster features impace crater A unique applicaiton using satellie imagery as art

  • Nara Inlet in the Whitsunday Islands is a natural depocenter for clastic and carbonate sediment on the middle shelf of the central Great Barrier Reef (GBR) platform. Three sediment cores were collected from the inlet to understand sediment accumulation in this tropical mixed clastic/carbonate system over time. Surface and subsurface sediment is comprised of two main components: terrigenous clay and shallow marine carbonate. Similar to other regions on the middle shelf of the GBR platform, the carbonate component, 25.80% by weight and dominated by Sr-poor foraminifera tests and mollusc shells, generally increases towards the surface. Radiocarbon ages derived from tests of benthic foraminifera indicate that the top 3 m of sediment accumulated within the last 3000 years, but that the rate has slowed toward present-day. The change in clastic and carbonate abundance therefore indicates a system where both clastic and carbonate accumulation has decreased over time, but where clastic accumulation has decreased faster. Reduced clastic accumulation may reflect progressive impedance of terrigenous input by a laterally growing fringing reef at the mouth of Nara Inlet. Likewise, reduced carbonate accumulation may reflect preferential reef growth and carbonate deposition outside of the inlet. Even though clastic accumulation has decreased significantly over time, the late Holocene mass, composition, and distribution of clastic material in Nara Inlet implies a terrigenous source previously unrecognized in models for the evolution of the GBR platform. Large amounts of terrigenous sediment probably were stored around topographic highs on the middle shelf during lowstand and early transgression. This clastic material was then removed over time, mixed with autochthonous carbonate, and deposited in embayments on the middle shelf. The accumulation of sediment on the middle shelf of a tropical mixed clastic/carbonate margin is not straightforward.

  • OCCAM 5.0 has new limits: 20 stations and 100 radiosources can be processed simultaneously. The number of baselines under study is 190, correspondingly. The current version of OCCAM supports IERS Conventions 2000. The ephemeride DE405/LE405 takes the place of DE403/LE403. To correct subdiurnal EOP variations two models can be chosen: proposed by Ray (recommended by IERS Conventions 1996) and by Eanes (IERS Conventions 2000) which takes into account many more tidal terms. A new leastsquares approach based on the Gauss-Markov model is available with the new version

  • Time series of Earth Orientation Parameters (EOP) have been obtained from independent parallel VLBI networks NEOS-A and CORE-A using OCCAM 5.0 software. This paper presents the results and their detailed consideration. The EOP time series are approximated by linear functions so offset and rate of the differences NEOS - CORE canbe estimated. It appears that biases between two EOP systems are negligibly small in 1996-1997 years but are increasing in time.

  • Map produced for the Lands Claims Mapping Unit (LCMU) of WA Department of Land Information and contains AUS323 image as background and red coloured areas showing thw area between lowest astronomic tide and the 2 metre isobath. Map for internal use of LCMU.

  • This paper describes the highlights of AGSO's work in the North Pilbara Project, a joint AGSO-Western Australia Geological Survey (GSWA) effort conducted under the National Geoscience Mapping Accord (NGMA) between 1995 and 2000. One of the principal drivers for AGSO's research in the Pilbara was the possible inapplicability of exploration models and genetic interpretations of Archaean mineral deposits because these models were commonly based upon late Archaean examples. One of our goals was to document the differences between the late Archaean and the early-mid Archaean mineral systems, and to develop regional thematic synthesis datasets so that more robust models could be developed to encompass the entire Archaean era. These datasets, together with our research into new exploration tools, have, and continue to assist exploration in the Pilbara. Our results also have applications to other terranes.