USAP 1989 Cruise IV R/V Polar Duke, Cruise Report

This is a report for the 1989 R/V Polar Duke scientific cruise, PD IV-89 (also known as PD8904), around the Antarctic Peninsula. The cruise collected single-channel seismic data, piston cores, and heatflow data.National Science Foundation's Office of Polar ProgramsInstitute for Geophysic

Heat flow in the central Gulf of California

One hundred and five new heat flow measurements in the Gulf of California support the premise that conductive heat loss is not the only mode by which heat is lost from a sea floor spreading center, even in an area with thick sediment cover. Theoretical estimates suggest that the average heat flow in the Guaymas and Farallon basins should be at least 11 μcal/cm2 s (HFU) (325 mW/m2). Outside a 30-km-wide zone centered on the central troughs, the heat flow values measured are reasonably uniform but average only 4.3±0.2 HFU (180±10 mW/m2). Although the high sedimentation rate may depress the measured heat flow, the effect probably does not exceed 15%. Some heat, particularly in the smaller basins, may be lost to the adjacent cooler continental blocks. The discrepancy between the measured and predicted heat losses, which is at least 30%, may be due to the discharge of thermal waters, through the thinner sediment cover in the central troughs or along active faults

Preliminary plate tectonic reconstruction of the Indian Ocean at Anomaly M10, 34, 28, 13, and 5 times, Part I.

Contact [email protected] for more information.During the winter of 1984 work was begun on the Paleoceano­ graphic Mapping Project at the Institute for Geophysics, Univer­ sity of Texas, Austin, Texas. The goal of the Paleoceanographic Mapping Project (POMP) is to produce a set of maps and film animations illustrating the tectonic evolution of the ocean ba­ sins during the last 200 million years. The basis of these global reconstructions is a new digital data base of linear magnetic anomaly data and sea floor bathymetry. Initial support for the Paleoceanographic Mapping Project was received from British Petroleum, and as a result of their support a set of the Indian Ocean reconstructions were produced using a preliminary version of the POMP database. The six reconstructions described in this report represent the initial test of POMP data gathering procedures and mapping programs. The maps in this report are based on the published rotation parameters of Norton and Sclater (1979), Sclater et al. (1981 ), Scotese and Ross (1982), Fisher and Sclater (1983) (see Appendix I)., and represent our current understanding of the plate tectonic evolution of the Indian Ocean. These maps highlight the remaining problem areas, and serve as the starting point from which a revised set of Indian Ocean reconstructions will be produced.Paleoceanograhic Mapping Project Consortium, Institute for Geophysics, The University of Texas at AustinInstitute for Geophysic

Heat flow at the spreading centers of the Guaymas Basin, Gulf of California

Fifty-four new heat flow measurements in the central troughs of the Guaymas basin support the hypothesis that they are sites of active intrusion. In the northern trough a distinct pattern of hydrothermal cooling is revealed, with venting along the western boundary fault of the trough. In the southern trough an analogous pattern is apparently superimposed upon a conductive cooling anomaly associated with a recent central intrusion. The discharge of thermal waters occurs along the boundary faults and through other faults associated with a possible horst block located in the north central floor of the southern trough. The heat flow patterns suggest that the intrusions are episodic and do not occur simultaneously along the length (15–40 km) of a spreading segment. A review of all available heat flow measurements for the Guaymas basin suggests that most of the recharge for a pervasive regional hydrothermal system is limited to the central depressions, with perhaps some contribution from pore water. The discharge of thermal waters occurs predominantly in the central depressions and possibly along the boundary transform faults and fracture zones. The regions of the basin more than a few kilometers in distance from the spreading axis, although presumably underlain by a hydrothermal system, are probably not the location of numerous vents or recharge zones

Single Channel Seismic Section Images From Larsen Ice Shelf, Antarctica Acquired by the RVIB Nathaniel B. Palmer in 1993 (NBP9301)

This 1993 RVIB Nathaniel B. Palmer cruise collected single channel seismic data in Bransfield Strait, Powell Basin and on the Larsen Ice Shelf. This report contains seismic sections images from the data on Larsen Ice Shelf. Funded by the National Science Foundation, Grant OPP-9019247.National Science FoundationInstitute for Geophysic

A Tight fit-Early Mesozoic Gondwana, a Plate Reconstruction Perspective

Gondwana, with East Antarctica as its center, began to break up during Late Triassic to Early Jurassic time. Use of the satellite derived gravity map to approximate the ocean-continent boundary allows us to generate a much tighter fit for the reconstructed supercontinent then previously attempted. Major mantle plumes such as the Karoo-Ferrar Plume that first split Gondwana at about 182Ma, the Parana-Etendeka plume at 132Ma that split South America and Africa, the Marion plume at 88Ma that split Madagascar and India and finally the Reunion hotspot that split the Mascarene Plateau from India at 64Ma, were all critical events in the break-up of Gondwana. Our tight-fit produces overlap between cratonic East Antarctica and the Limpopo Plain of Mozambique but there is no evidence that the crustal material underlying the Limpopo Plain pre-dates the break-up of Gondwana. Likewise Madagascar has been reconstructed so that it substantially overlies coastal East Africa in the vicinity of the Anza Trough, an early Jurassic rift in Kenya. The western margin of the island of Madagascar may in fact be crustal material that is younger than the break-up. It may have been produced as a result of the Karoo mantle plume or some may have been the result of the Marion hotspot. Between South America and Africa there are three significant overlaps. Two of them are deltaic, and the third is the Abrolhos and Royal Charlotte banks which post-date Gondwanide breakup by 80 to 100 million years

Cenozoic Evolution of the American-Antarctic Ridge (Paleoceanographic Mapping Project Report No. 09-0286)

New bathymetric and magnetic anomaly data for the American-Antarctic Ridge region of the South Atlantic are compiled and presented. The magnetic anomaly data are used to produce poles of rotation and angles of opening for six stages for the Cenozoic between anomaly 5 time (9. 7 Ma) and anomaly 21 time (50.3 Ma). Synthetic spreading centers and fracture zones are generated, some of which give very close agreement with noted SEASAT derived gravity anomalies. Two large symmetrical regions of the American-Antarctic Ridge area could not have been formed at the present-day active American-Antarctic Ridge spreading centers. We conclude that the 560 kilometer long Bullard Fracture Zone was created just prior to anomaly 6 (20.4 Ma) time eliminating two or more spreading segments of the American-Antarctic Ridge. The change in spreading and direction which precipitated the realignment of transform faults was caused by the subduction of about 25% of the American-Antarctic Ridge at anomaly 6A or 6B time (21.0-23.0 Ma) at Jane Bank. An additional section of the ridge was subducted near Discovery Bank at about 7-10 Ma and about half of the remaining American-Antarctic Ridge will be subducted between 17 and 20 million years from now if present-day rates persist.UT Institute for Geophysics Paleoceanographic Mapping Project (POMP)Institute for Geophysic

South Georgia Enigma using PALEOMAP (Paleoceanographic Mapping Project Progress Report No. 28-1287)

This report presents plate reconstructions of the Scotia Sea.UT Institute for Geophysics Paleoceanographic Mapping Project (POMP)Institute for Geophysic