Geologic Mapping of the Franklin Volcanic Field Western Ross Sea, Antarctica
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Date
2004-12
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The Ohio State University
Abstract
The RVIB N. B. Palmer collected bathymetric and seismic data in the western Ross Sea
in January/February 2004 with the specific purpose of mapping neotectonic structural and
volcanic features on and beneath the seafloor. The Franklin Volcanic Field (FVF) is an important
feature revealed by the bathymetric data. The volcanic field, which is expressed as a regional
bathymetric high, is a minimum of 80 km long and up to 40 km wide. As one moves north, the
overall trend of the volcanic field appears to curve from N-S to NE. Superimposed on the regional
high are the subaerial portion of Franklin Island and clusters of submarine volcanic cones.
Franklin Island has been interpreted as the western remnant of a shield volcano and has a single
K-Ar date of 4.8+2 Ma. Its submarine morphology is characterized by a steep western flank and
an eastern flank that, within the limits of the mapped region, appears to have a shallower slope.
North of the island, there are 8 discrete cones, three of which were dredged, yielding basaltic
lava, hyaloclastite and tuft. The seafloor morphology in the northern sector of the field is
characterized by lineations at several scales, some hummocky terrain marked by circular to oval
depressions, and superimposed iceberg scours. Based on morphology alone, the linear features
could reflect volcanic ridges, faults, or glacial lineations, or may have formed by a combination of
these processes. The origin of the seafloor features within the FVF has been determined through
integrated analysis of magnetic, gravimetric and seismic data. Using the spatial associations of
the features, this work proposes a reconstruction of the direction of glacial flow during the Last
Glacial Maximum as well as maximum and minimum crustal stress directions during the formation
of the Franklin Volcanic Field.