ABSTRACT: Origins of the Celebes and Sulu Seas: Results of ODP Leg 124

Eli A. Silver, Claude Rangin

The Celebes and Sulu seas originated in very different tectonic settings. Celebes formed in the middle Eocene, restricted from terrigenous input. Basal sedimentary red clays, rich in radiolaria, fish teeth, and manganese micronodules, overlie MORB tholeiites. Green silty clay sedimentation beginning in lower Miocene suggests proximity to land sources, and relatively high rates of turbidite input mark the middle Miocene. Turbidites decrease in late Miocene, accompanied by higher influx of carbonate sediments and volcanic ash, suggesting initiation of surrounding island arcs and development of trench systems to trap the turbidites. Sulu sea formed in late early Miocene time, followed closely by deposition of thick, pyroclastic deposits. Thin, radiolarian-rich brown mudstone lies above and below the pyroclastics, then silty clays follow soon after. The middle Miocene is also marked by high rates of turbidite sedimentation, and carbonates and volcanic ash dominate the Pleistocene deposits. Basement is basalt with arc affinities. The Celebes Sea spent its first 20 m.y. away from terrigenous sources, yet maintained low paleolatitudes. The SE Sulu Sea is most easily explained as a back-arc rifted basin, but it formed close to the time of cessation of activity of the Cagayan arc. Modern regional stress orientations determined with borebole televiewer in both basins show a consistent NE direction of maximum stress, suggesting that stress within the basins is dominated by collision of the Philippine islands against the Palawan, Cagayan, and Sulu ridges.

AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990