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Investigations of Crustal Structures beneath Dronning Maud Land

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Hoffmann, M. , Eckstaller, A. , Jokat, W. and Miller, H. (2003): Investigations of Crustal Structures beneath Dronning Maud Land , ISAES 9th International Symposium on Antarctic Earth Sciences 8. - 12. September 2003, Potsdam, Germany .
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Abstract:

The western part of Dronning Maud Land (DML), Antarctica, principally consistof the Archean Grunehogna Craton and the Grenville-age (1.1 Ga) Maud Province(Jacobs, 1991). Most of the area is covered by ice. Outcrops are the mountainranges Heimefrontfjella, Kirvanveggen and Sverdrupfjella. These are the westernparts of the East Antarctic Orogen, the southern continuation of the EastAfrican Orogen, formed during the collision of East and West Gondwana(Pan-African orogenesis, ca 550. Ma).The Heimefrontfjella metamorphic complex is splitted by the Heimefront shearzone. This steeply dipping and NE trending dextral shear zone separates tworegions with a different tectonic history: the Vardeklettane and Kottas terranewith Grenvillian crust at the NW side and the Sivorgfjella Terrane with strongPan-African tectono-thermal overprinted crust at the SE side of the shear zone.(Golynsky & Jacobs, 2001)The structure of the crust and mantle in western DML is mostly unknown.Especially the deeper crustal fabric along the geological boundaries is ofgreat interest. Thus, during the Antarctic summer 2002/2003, a temporaryseismometer network consisting of five seismometers was installed along a 250km line crossing the Heimefrontfjella shear zone. In addition a permanentbroadband seismometer station at Kohnen Station (ca. 75°S, 0°E) wasestablished. In combination with registrations from the Neumayer seismometernetwork and the seismometer at the South African SANAE IV Station, a spatialmapping of crust thickness (Moho depth) by means of calculating the receiverfunctions will be obtained. Further analysis of the data will yield to therecent/past strain/stress distribution (seismic anisotropy) and the detectionof local seismicity.Preliminary results (Eckstaller, et al., 1991) from a analysis of a refractionseismic profile, perpendicular to the shear zone, are showing different regionsof crustal thickness: in the north-west 42 km and in the south-east 50 km. Thisconfirms that the Heimefrontfjella shear zone is also a boundary in terms ofcrustal evoloution and fabric. The interpretation of this seismic profiletogether with new obtained aerogravity, aeromagnetic and ice thickness data incombination with the seismological data will provide a 3-D model of the crustalstructures beneath western Dronning Maud Land.ReferencesJacobs, 1991, Berichte zur Polarforschung 97Golynsky & Jacobs, 2001, The Journal of Geology, vol. 109: 136-142Eckstaller, et al., 1991, Berichte zur Polarforschung 86: 108-122

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