Quaternary Uplift of the Torres Islands, Northern New Hebrides Frontal Arc: Comparison with Santo and Malekula Islands, Central New Hebrides Frontal Arc
- 1 July 1985
- journal article
- Published by University of Chicago Press in The Journal of Geology
- Vol. 93 (4) , 419-438
- https://doi.org/10.1086/628964
Abstract
Coral reef terraces on the Torres Islands have recorded the Quaternary uplift of part of the northern New Indian plate underthrusts the arc from the west. 14C and 230Thp34U ages for Torres fossil corals indicate that for approximately the past 100,000 years the islands uplifted at a constant rate ranging geographically from 0.7 to 0.9 "/yr. The occurrence of similar uplift rates and eastward-tilting directions and the absence of major crosscutting structures or rupture zone boundaries suggest that the islands may be part of a single tectonic block or arc segment. The frontal arc morphology in the Torres area is typical of frontal arcs. Farther south, the central New Hebrides frontal arc has no physiographic trench at the plate boundary west of Santo and Malekula Islands, and the axes of the maximum uplift rate are at the seaward edge of the plate. The d'Entrecasteaux Ridge (DR), a massive E-W trending bathymetric feature on the Indian plate, is underthrusting Santo and Malekula. The eastern parts of Santo and Malekula are physiographically equiva- lent to the Torres Islands and seem to have been on a former axis of maximum uplift rate. However, in response to subduction of the DR, the uplift axes of Santo and Malekula may have shifted westward. In a few hundred thousand years the new uplift axes caused the western parts of these islands to achieve their present topographic dominance over the earlier uplift axes. Holocene uplift rates on southern Santo and northern Malekula are about twice the average rates of the previous 100,000 years. The accelerated Holocene uplift could be explained if a particularly prominent part of the DR has recently underthrust Santo and Malekula. d Hebrides frontal arc. These isles lie about midway between the volcanic chain and trench axis, where theKeywords
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