Implications of the occurrence of large gravity gradients in Northern Timor

Abstract

Recent gravity measurements in eastern Timor have shown that steep gradients occur in the northern part of the island, and that the maximum Bouguer Anomaly values attained are greater than those on the inner volcanic arc immediately to the north. The observations can be explained only by supposing that the dense source rocks rise very close to the surface, and analogies can be drawn with the large anomalies associated with ophiolitic thrusts in New Guinea and New Caledonia. The pattern of volcanic activity north of Timor also resembles that of eastern New Guinea, suggesting, again by analogy, that a thrust slice is wedged in the subduction zone south of the inner Banda arc. If correct, this hypothesis provides some support for the concept of Timor as built up of a series of thrust slices resting ultimately on continental basement.