Abstract
Geophysical data are presented and discussed for an area approximately 290 km long and 220 km wide in the Aleutian trench south of Kodiak Island. Variations in total magnetic intensity (residual) of more than 600 γ were found in the center of the trench and more than 1100 γ on the southern flank. The free-air gravity values varied by as much as 150 mgal. The residual magnetic and gravity anomalies suggest that a fissure zone, filled with basic igneous material, is located in the center of the trench. Free-air anomaly calculations indicate that the top of the mantle is 4 km below the trench floor. The magnetic anomaly trend on the southern flank of the trench is interpreted as a fracture zone. Both magnetic and gravity data suggest the existence of a ridge of igneous rock material underlying the northern trench slope. It is concluded that the geophysical results in this area are comparable to those obtained in many other continental margins of the earth. This conclusion supports the theory that continental margins and trenches are affected by tensional forces in the earth's crust.
Published Version
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