Paleolatitudes and magnetostratigraphy of Cretaceous and Lower Tertiary sedimentary rocks, Deep Sea Drilling Project Site 585, Mariana Basin, western central Pacific ( Leg 89).

Abstract

Coring in 2 adjacent holes at DSDP Site 585 (13.5oN, 156.8oE) recovered lower Tertiary through Aptian sedimentary rocks. The paleolatitudes of each hole from the late Aptian through Paleocene were derived from an extensive set of paleomagnetic minicores. Each sample underwent progressive thermal demagnetization, and the characteristic direction of magnetization was derived from the region of stable directions. True mean inclinations were computed for each lithologic unit and for each stage or pair of stages, using the method of Kono (1980b). The results yield average paleolatitudes of 1oS for the Paleocene-Maestrichtian, 7oS for the Santonian-Turonian, and 15oS for the Albian-late Aptian. The Aptian-Albian paleolatitudes agree with paleomagnetic results from DSDP Sites 462 and 289 in the western central Pacific. The average rate of northward drift by the site was about 30km/m.y. through the Late Cretaceous and earliest Tertiary. Recovery of the latest Cretaceous-early Tertiary sediments was inadequate to allow unique determination of the magnetostratigraphy. No reversed interval could be identified within the late Aptian or early Albian. -from Author