ABSTRACT: Preliminary Interpretation of Combined GLORIA and SeaBeam Imagery in the Vicinity of the Chile Margin Triple Junction

S. F.Tebbens, G. K. Westbrook, S. C. Cande, S. D. Lewis, N. Bangs

In early 1988, a suite of geophysical data in the vicinity of the Chile Margin Triple Junction was collected aboard the R/V Conrad, which included a detailed SeaBeam bathymetric survey and numerous multichannel seismic profiles. In late 1988, the same region was surveyed with GLORIA long-range side-scan sonar from the RRS Charles Darwin. Analysis of the two data sets reveals the character of the 40-km-long actively spreading Chile Ridge between the Darwin fracture zone and the ridge's intersection with the landward trench slope. SeaBeam bathymetry shows the rift valley to be relatively flat, containing numerous seamounts. On the GLORIA imagery the rift valley is associated with a bright return which is believed to be from fresh oceanic basalts. At the intersection of the ift and the trench slope, the axial bright return on the GLORIA imagery extends approximately 2.5 km onto the base of the landward trench slope.

Off the ridge axis, sedimentary features observed in the combined data sets include (1) slumps forming lobate flows of sediment on the rift valley floor and (2) erosional canyons with dendritic-style tributary gullies on the landward trench slope.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990