Special Section: Polar Seas Geological Record
Geology and structure of the Astrid Ridge, Dronning Maud Land, Antarctica
Article first published online: 4 MAY 2010
Copyright 1988 by the American Geophysical Union.
Volume 3, Issue 5, pages 583–599, October 1988
How to Cite
1988), Geology and structure of the Astrid Ridge, Dronning Maud Land, Antarctica, Paleoceanography, 3(5), 583–599, doi:10.1029/PA003i005p00583., , and (
- Issue published online: 4 MAY 2010
- Article first published online: 4 MAY 2010
- Manuscript Accepted: 28 MAY 1988
- Manuscript Received: 27 NOV 1987
Bathymetric (458 line km), Seismic reflection, higher energy sparker source (405 line km) and magnetic (452 line km) studies of the Astrid ridge, a prominent broad bathymetric feature in water depths of about 1520–2900 m on the continental margin of Dronning Maud Land, are carried out. The crest of the ridge in the area surveyed trends N-S in the south but veers to NNW-SSE at about 68° S Latitude and is found to change to NNE-SSW at about 67° S Latitude. The western flanks of the ridge in the south are gently sloping while the eastern flanks are marked by NNE-SSW trending scarps of about 80–280 m. The northern area is marked by a NW to NNW-SE to SSE trending valley, about 5–15 km wide and 240–380 m deep with steep gradients. The ridge is mantled by layered sediments of a top transparent layer (50 to 0.4 s) underlain by a prominent reflector (50 ms to 100 ms) and the acoustic basement. The basement occur at 0.4 to 0.6 s depth. The sediments dip away from the crest of the ridge to the flanks. The seismic records further indicated that the NNE-SSW trending scarps on the eastern flanks represent faults which extend only to the younger sediments. They are not reflected in the magnetics indicating that they are not deeper structures. The NW-NNW to SE-SSE trending narrow valleys with steep gradient walls occurring on the ridge crest in the study area are grabens where the basement and associated sediments have been faulted down. The graben in the north is marked by a series of magnetic anomalies of about 50 to 200 nT superposed over the peak of a broad high amplitude anomaly of a mafic material buildup and appears to be a deep crustal feature. The positive bathymetric feature of the ridge part in the south of the study area is not reflected in magnetic anomaly signatures, implying heterogeneity in composition. The magnetic basement is interpreted at depths to top of 1.8 km to 4.0 km. The graben appears to be a major tectonic feature of the area and marks a change in the trend of the ridge at about 68°S Latitude.