(poster p.)
M. Berrocoso, C. Torrecillas, R. Paez, J.M. Enriguez-Salamanca, E. Ramirez, A. Fernandez-Ros, A.
Perez-Pena & M.J. Gonzalez
Laboratorio de Astronomfa y Geodesia, Departamento de Matematicas, Facultad de Ciencias, Universidad de Cadiz, Campus Rfo San Pedro, 11510 Puerto Real (Cadiz); <mariaeva.ramirez@uca.es>;
<manuel.berrocoso@uca.es>.
The desribed information support system can be defined as a set of interrelated components that collect, process, store and distribute information to the basis for decision-making and control in an organization (STAR 1992).
Geographical Information Systems (GIS) are information systems designed for working with georeferenced data. GIS are of great value where the variable or attribute has great geographical influence. Among the advantages offered by GIS, is an environment for the analysis, creation and study of topological relations, as well as comparitive spatial, proximity or adjacency studies. It also allows for two-dimensional spatial indexating and multi-user editing of data and versions.
Since the Spanish Antarctic campaigns began in 1987 on Deception Island, South Shetland Islands we have obtained a large amount of cartographic data and graphic output on numerous projections, referenced to several geodetic systems. There is now a need to compile this multidisciplinary data and integrate it into a geographic information system. This would make the information on Deception Island more accessible to the scientific world, avoid duplicating information and enhance collaboration among research groups through the exchange of data and transfer of results.
27
-DECVOL and GEODEC projects (poster p.)
M. Berrocoso1, A. Garda2, J. Martin-Davila3, M. Catalan-Moroll6n3, M. Astiz4, E. Ramirez', C.
Torrecillas' & J.M. Enriquez-Salamanca'.
1Laboratorio de Astronomfa y Geodesia, Departamento de Matematicas, Facultad de Ciencias, Universidad de Cadiz, Puerto Real (Cadiz); <manuel.berrocoso@uca.es>;
2Departamento de Volcanologfa, Museo Nacional de Ciencias Naturales, Madrid;
3Secci6n de Geofisica, Real Institute y Observatorio de la Armada, San Fernando (Cadiz);
4Departamento de Matematicas, Escuela Superior de Arquitectura, Universidad Politecnica, Madrid;
In the presented paper it is shown the main objetives and results obtained in DECVOL project as well as the objetives and activities carried out in GEODEC project. The information resulting from continuous studies from 1987 has shown a scientifically interesting situation in the geodynamical aspect. Three of the most active groups which have been working in Deception Island will gather to provide a current an projected status of the volcanic complex by means of high resolution models.
In December 1999, DECVOL project consisted of the realization of a short campaign set aside for a geodetic and geophysical monitoring, with the aim of determining the activity situation in the island resulting from the seismic crisis during the austral summer in I 998- I 999. During this campaign, a great deal of measurements were collected, as GPS observations and gravimetric and magnetic measurements, among others.
In the GEODEC project the network REGID has been reobserved, and it has been improved with new points, determined from the recent activity. The extension of the network and the use of a permanent station in Livingston Island will allow a centrimetric resolution required for volcano monitoring. A marine geophysical campaign sequel to a previous campaign (DECVOL 99) will allow a superficial definition of Deception Volcano structure. The existence and delimitation of the latest eruptions' magmatic chamber and an evaluation of possible short and medium term eruptions. The use of geographical information systems has revealed itself as imperious in the making of risks maps, integrating all available data (geological, geochemical, geodetical, geophysical, etc. ) a map of Deception Island may be produced. These maps are required to develop models of lava flows, products emission, etc. In others words, the effects of an eruptive process. In a parallel way, statistical methods will be use to evaluate return period and deterministic models reconstructing pasted events and forecasting future eruptions. The final deliverable will be the creation of volcanic hazard and risk maps for Deception Island.
Climate changes over the last two glacial-interglacial cycles: sea surface temperature and sea-ice records from the Southern Ocean
{poster p.) Christina Bianchi & Rainer Gersonde
Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany; <cbianchi@awi-bremerhaven.de>.
Opal-rich sediment sequences from two high latitude locations of the Atlantic sector (ODP Sites I 093 and I 094) in the southern Polar Front Zone and the Antarctic Zone respectively, allowed us to reconstruct the Southern Ocean climate development over the past 180 ka. Here we present records of summer sea surface temperature (SSST), obtained by means of a transfer function, and records of sea-ice extent, inferred from abundance fluctuations of sea-sea-ice diatoms (Fragilariopsis curta, F.
cylindrus, F. obliquecosrara).
28
-During glacial times the maximum extent of the sea-ice edge reaches c 3° latitude to the north relative lo present and sea-ice seasonality appears reduced. The diatom assemblage shows high abundances of Eucampia antarcrica, Chaeroceros spp. and sea-ice algae (Fragi/ariopsis curta and F. cylindrus). The southward retreat of the sea-ice edge and surface water warming at the onset of the deglaciations results in dramatic changes of the environmental conditions, as indicated by the drastical increases in sedimentation rates and marked changes in the composition of the diatom assemblage, which becomes dominated by the open water species Fragilariopsis kerguelensis.
The warming along Terminations I and II occurs in two steps separated by a temperature rebound, resembling the structure of the Antarctic Cold Reversal. While during Termination I the major environmental changes occur during the first step of deglaciation (18-14 ky BP), at Termination II these take place during the second step, which is concluded at c 128 ka.
The southward retreat of the sea-ice and SSST development at Terminations I and II well correlates with the timing and shape of the increases in atmospheric C02, as recorded by ice cores, supporting the idea that the Antarctic winter sea-ice, Southern Ocean temperature and/or water column structure exert a primary control on the atmospheric-ocean C02 exchanges and hence on global climate.
Structural geology and geochronology of the Gjesvikfjella area, northern Maud Belt, East Antarctica
(oral p.) A. Bisnath1, H.E.Frimmel1 & R.A. Armstrong2
1 University of Cape Town, Department of Geological Sciences, Rondebosch 770 I, South Africa:
<avinash@geology.uct.ac.za>, <hef@geology.uct.ac.za>;
2Australian National University, Research School ofEarth Science, Canberra ACT 0200, Australia;
<.Prise.Armstrong@anu.edu.au>.
The Maud Belt of western Dronning Maud Land (DML) represents the western extension of the East Antarctic Shield that preserves a polymetamorphic history with two orogenic episodes of
"Grenvillian", i.e. 1.2-1.0 Ga age and secondly "Pan-African", i.e. 0.6-0.5 Ga age. Gjelsvikfjella forms the north-easternmost portion of the high-grade polydeformed metamorphic terrane, known as the Maud Belt in western DML, East Antarctica.
Studies by JACKSON ( 1999) in the Kirwanveggen, western DML suggests that the existence of regional pervasive tectonic structures of Pan-African age in the northeast trending Maud Belt is unclear, because of the possibility of co-linearity of Grenvillian and Pan-African structures. JACOBS et al. ( 1998) and SHIRAISHI et al. ( 1994) emphasized the Pan-African event for east-west trending central DML and eastern DML respectively, thereby casting doubt on the presumed continuity of Grenvillian-age crust within the East Antarctic Shield. In support, recent studies by BOARD (2001) suggest that the regional pervasive tectonic structures present in Sverdrupfjella area of western Dronning Maud Land formed during Pan-African times, implying that the earlier orogenic event has been completely overprinted.
This study concentrates on the Gjelsvikfjella area, which provides a unique opportunity to address the above problem as two structural trends intersect there. This paper aims at highlighting new structural and geochronological data. Field relationships show that the oldest unit present is a metasupracrustal sequence of continuous to discontinuous metatuff, metabasalt and metagabbro. Remnants of eclogite might be present in the form of stretched and rotated boudins of garnet-clinopyroxene rock. The supracrustal rocks were intruded by a megacrystic, granitic augen gneiss with a single zircon SHRIMP age of 1104.4 ±8.3 Ma.
29
-Three stages of granitic intrusions have been observed. The first is a medium to coarse-grained variety that intruded at 1130
±
19 Ma prior to the regional deformation. The second are granitic vein lets that possibly formed as a product of partial melting at approximately I 030 Ma, and finally the youngest intrusion being aplite dykes (497.6 ±5.3 Ma) that cut across the regional foliation and a major shear zone.Five deformation events are recorded in the rocks. D2 and D3 appear to be a continuous deformation event. The D1 event is represented by (F1) fold axes that have been rotated parallel to sub-parallel into the dip direction of the regional pervasive foliation (S2). The older D 1 event is interpreted to represent the Grenvillian deformation event that has been overprinted by the D2-D3 events in certain areas providing support for the data published by BOARD & FRIMMEL (2001) suggesting a top to the northwest shearing event that occurred during Pan-African deformation. D3 folds the regional fabric and D4 is seen as a broad open type of folding or warping event. D5 is expressed as fractures related to Gondwana break-up.
Board. W.S.] Frimmel, H.E. (2001): SANAP Final Project Report. Department of Environmental Affairs and Tourism, Pretoria, 16 pp.
Jacobs, J., Fanning, C.M .. Henjes-Kunst. F .. Olesch. M. & Paech. H.S. (1998): J. Geo!. 106: 385-406.
Jackson, C. ( 1999): SANAP Final Project Report. Department of Environmental Affairs and Tourism, Pretoria, 80 pp.
Shiraishi, K., Ellis, D.J., Horoi, Y., Fanning, C.M., Motoyoshi, Y. & Nakai, Y. (1994): J. Geol. 102: 47-65.