Motion of the Australian Plate from Sediment Paleoinclinations, Early Cretaceous through Holocene

Abstract

The change in paleolatitude of the areas off northwestern Australia since the Early Cretaceous was determined from Paleomagnetism of cores from ODP Leg 123 (Sites 765 and 766) and DSDP Leg 27 (Site 261). The Early Cretaceous paleolatitudes determined for Sites 766 and 261 agree with each other, indicating an average paleolatitude of 37° ± 3°, which is slightly lower than expected from the Australian apparent polar wander path (APWP). The Early Cretaceous to Paleogene paleolatitudes for Site 765 are systematically lower than those predicted by the Australian apparent polar wander path. In particular, the disagreement between these data and predictions for the mid-to-Late Cretaceous is in excess of 15°. INTRODUCTIONLeg 123 of the Ocean Drilling Program was undertaken in the Argo and Gascoyne abyssal plains in the eastern Indian Ocean, which lie between the Java Trench to the north and the northwestern margin of Australia to the south (Fig. 1). Analyses of marine magnetic anomalies (Larson, 1975;Heirtzler et al., 1978;Fullerton et al., 1989) and previous drilling of DSDP Leg 27 in the Argo Abyssal Plain (Veevers, Heirtzler, et al., 1974) suggested that the basins off northwestern Australia are among the oldest in the Indian Ocean, with an age for the oldest portion of Oxfordian to Kimmeridgian (150-160 Ma). Although DSDP Site 261 in the Argo Abyssal Plain (12.9°S, 117.9°E) was penetrated down to basaltic basement, the recovery of sediment cores was poor (20% on average), and the paleontological age of the basalt/sediment contact was not well constrained as Hauterivian-Valanginian to upper Oxfordian (Veevers, Heirtzler, et al., 1974).Thus, the primary objectives of Leg 123 were (1) to recover a complete sedimentary section from the Late Jurassic to Holocene for elucidating the tectonic and paleoceanographic development of the Indian Ocean, (2) to improve the Late Jurassic to Early Cretaceous magnetobiostratigraphy for the Southern Hemisphere by correlating to the magnetic polarity time scale, as compiled from the Pacific and Atlantic-Tethys regions, and (3) to investigate the geochemistry and petrology of the oldest oceanic basement formed at the initial break-up of Gondwanaland. Site 765 of Leg 123 thus was placed near the ocean/continent boundary of the Argo Abyssal Plain and the Exmouth Plateau (16.0°S, 117.6°E; 5730 mbsf), where a Late Jurassic marine magnetic anomaly lineation identified as Chron M25 (late Oxfordian) by Fullerton et al. (1989) trends in an east-northeast to west-southwest direction (Fig. 2). Site 766 was located at the foot of the western Exmouth Plateau (19.9°S, 110.5°E; 4008 mbsf), about 10 km southeastward from Chron M10 of Fullerton et al. (1989). Thick sequences of Lower Cretaceous to Holocene strata, together with basaltic basement, were recovered at both sites. No Jurassic sediment, however, has been recognized from Site 765, the basal age of which was late Berriasian, while the age of the sediment/basalt Gradstein, F. M., Ludden, J. N., et al., 1992. Proc. ODP, Sci. Results, 123...

Paleolatitudes and magnetostratigraphy for Cenozoic sediments, ODP Leg 182: The Great Australian Bight

“…Kodama and Ogg (1992) Musgrave (1989) Idnurm (1994) Embleton and McElhinny (1982) Embleton and McElhinny (1982), (2) Musgrave (1989), and (3) Idnurm (1985Idnurm ( , 1994. The numbers indicate approximate age of the reference (south) pole.…”

“…Only recently, has the paleomagnetic record of deep-sea sediments been used to place constraints in APWPs of major plates (Klootwijk et al, 1991;Kodama and Ogg, 1992;Acton, 1999). The record of Australia's plate motion contained in Cenozoic sediments recovered on ODP Leg 182 provide the means to better define Australia's APWP.…”