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Report on the Victoria University of Wellington Antarctic Expedition 1960-61: VUWAE 4

Bouguer Anomaly Map

Bouguer Anomaly Map

In Figure 1 the values of Bouguer anomaly at a representative number of gravity stations are plotted, together with the isogals obtained by considering all of the station values. The Bouguer anomaly decreases from a value of 0 mgals in the northeast to −90 mgals at the extreme western point of the survey. A full consideration of the results has not yet been made but the following points may be significant.

1.In the northeast part of the area the isogals are approximately north-south, as they are in the Wright Valley further north. This probably indicates that if the coastline is fault controlled, that the fault continues southwards from Cape Chocolate and does not swing southwesterly to follow the northern side of the Koettlitz Glacier.
2.The gravity gradient in the north-east part of the area is smaller than the 10 mgals/mile which occurs at the coastal end of the Wright Valley, and which has been interpreted in accord with the existence of a major fault along the coastline.page 11
3.A gravity graidnet of about 10 mgals/mile does occur a few miles to the west, between the mouth of the Marshall Valley and the head of Miers Valley. This large gravity gradient is not associated with any major fault.
4.Heald Island appears to be gravitationally associated with the area on the mainland immediately west of it. It is unlikely that the northern side of the Koettlitz Valley is fault-controlled.
5.Values of Bouguer anomaly are significantly higher near the Pyramid, which was one of the main centres of recent volcanic activity in the area.
6.The overall east-west gradient is approximately 2 mgals/mile. This is a value similar to that found in traverses from the lowlands of Austria or Italy into the regionally isostatically compensated Alps.
7.In the western end of the Wright Valley the gravity gradient changes sign, and higher values of Bouguer anomaly are found to the west. This probably indicates that the western side of the Victoria Land mountain chain is also fault controlled and that the formation is a horst. No similar change in the gravity gradient is found in the present survey; values of the Bouguer anomaly continue to decrease westwards. It is regretted that time was not available to continue the survey into the Royal Society Range.