Underway Geophysical Measurements, Leg 39, Deep Sea Drilling Project

Neprochnov, Y.P.; Merklin, L. R.; Supko, P.R.

doi:10.2973/dsdp.proc.39.143.1977

Cited by 3 publications

(3 citation statements)

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“…(a) Southern Gambia Basin (Jones 1987); ~) West of Sierra Leone Rise (Jones 1987); (e) Sierra Leone Basin (Jones 1987); (d) Guinea Basin (Delteil et al 1974); (e) Demerara Abyssal Plain (Neprochnov et al 1977). Aptian time at the earliest (Jones 1987).…”

Section: Deep-water Seismic Stratigraphy and The Opening Of The Equatmentioning

confidence: 99%

Evolution of a major oceanographic pathway: the equatorial atlantic

Jones

Cande

Spathopoulos

1995

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The history of continental separation in the equatorial Atlantic is important to our understanding of the events which have led to the establishment of the present patterns of water circulation. Orientations of oceanic basement-lineaments determined from bathymetric, seismic, magnetic and satellite altimetry data, and the distribution of seismic reflectors in deep-water sediments indicate that during its early opening stages the Atlantic was bounded to the south by the Guinea Fracture Zone. Using stage poles obtained from South Atlantic spreading patterns, basement ages and the palaeobathymetry of the equatorial region have been derived. The proximity of magnetic anomaly M0 to the present continental slopes suggests that the deep-water basins began to form in the Aptian. During

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Section: Deep-water Seismic Stratigraphy and The Opening Of The Equatmentioning

confidence: 99%

Evolution of a major oceanographic pathway: the equatorial atlantic

Jones

Cande

Spathopoulos

1995

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“…Glomar Challenger profiles from Legs 36, 39, 71, and 72 comprise the remaining single-channel airgun data. Those from Legs 36 (Barker, Dalziel, et al, 1976) and 71 (Ludwig, Krashenninikov, et al, in press) cross only the lower slopes of the Rise; those from Leg 39 (Neprochnov et al, 1977) are of uneven quality, because they were shot partly in bad weather. Leg 72 tracks are distinguished in Figures 2 and 3 by dashed lines.…”

Section: Data Distributionmentioning

confidence: 99%

A Seismic Reflection Study of the Rio Grande Rise

Barker¹,

Buffler²,

Gambôa³

1983

Initial Reports of the Deep Sea Drilling Project, 72

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Seismic reflection profiles have been interpreted in combination with deep-sea drilling data to examine the sedimentary evolution of the Rio Grande Rise.Restricted and unevenly distributed seismic reflection coverage (particularly multichannel) and limited well control confined most of our interest to the northern flank of the main western elevated block of the Rise, near to DSDP Site 516. The basement of much of the Rise above approximately 3000 m present depth has the "dipping reflector" character of some continental margins, produced by interbedded lavas and sediments formed directly above sea level. The overlying Late Cretaceous and early Tertiary sediments are mainly pelagic, but lap onto originally subaerial basement in places. A major middle Eocene tectonic event (involving uplift, tilting, faulting, and probably local volcanism) resulted in subaerial erosion, submarine slumping, and turbidite deposition. Submarine slides associated with the early stages of this tectonism probably caused the chaotic midsection reflector sequence identified with the middle Eocene Unit 4 at Site 516. Middle Eocene tectonism also produced the central graben of the Rise, which contains rotated fault blocks, and the broad guyot between the graben and Site 516. The guyot shows thick sequences dipping away from the graben and truncated, presumably by subaerial erosion. Prograded biogenic debris, swept off the top by bottom currents after resubmergence in the Oligocene, extended the guyot's top farther. Biogenic debris from the same source probably formed the initial load of the density currents that have dissected the steeper northern slopes of the Rise. Interpretation of reflection profiles from all around the Rise suggests erosion between depths of 2000 and 3600 m, even where the creation of density currents upslope is unlikely; a component of contour current erosion by North Atlantic Deep Water may be involved. The Vema Terrace, which in the west separates the Rio Grande Rise from the Vema Channel, shows signs of sedimentation from turbidity currents originating on the Rise. The Terrace and the Vema Channel extend around the north flank of the Rise also; their positions are controlled by the topography of the east-west Rio Grande Fracture Zone. If the eastward flow of Antarctic Bottom Water north of the Rise is inferred, the direct transport of debris from the Rise to the Brazil Basin by turbidity currents becomes a more complex process.

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“…Tristan da Cunha was recently active and lies about 400 km from the ridge crest, on ocean floor about 20 Ma old (Ladd, 1974). At DSDP Site 359 subaerial trachytic tuff, which yielded a K-Ar age of 40 Ma , was drilled from the top of a seamount that was about 1000 km from the ridge crest and lay on ocean floor of Anomaly 25 age, about 59 Ma old (Neprochnov et al, 1977(Neprochnov et al, , p. 1009. Northeastward, the topographic expression of the Walvis Ridge changes, becoming more massive and linear, reflecting the influence of ridge crest and fracture zone trends in the ocean floor.…”

Section: The Rio Grande Rise-walvis Ridge Systemmentioning

confidence: 99%

Regional Tectonic Setting of the Southwestern Atlantic

Barker¹,

Carlson²

1983

Initial Reports of the Deep Sea Drilling Project, 72

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This paper, an introduction to the tectonic aspects of Leg 72, begins with an explanation for the presence of a tectonic element within a paleoenvironmental drilling program, in terms of the importance of the Rio Grande Rise as an influence on and sampler of deep and intermediate circulation and sedimentation. The state of knowledge of the origin and history of this part of the South Atlantic before Leg 72 drilling (including that of the Rio Grande Rise-Walvis Ridge system of seamounts and ridges) is then reviewed, and the main body of the Rio Grande Rise is considered in detail. Finally, with benefit of hindsight, we examine how Leg 72 drilling could most effectively help our understanding of the evolution of the Rise and increase the precision with which a subsidence history may be computed.

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Underway Geophysical Measurements, Leg 39, Deep Sea Drilling Project

Cited by 3 publications

References 0 publications

Evolution of a major oceanographic pathway: the equatorial atlantic

Evolution of a major oceanographic pathway: the equatorial atlantic

A Seismic Reflection Study of the Rio Grande Rise

Regional Tectonic Setting of the Southwestern Atlantic

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