Chain and romanche fracture zones

Heezen, Bruce C.; Bunce, Elizabeth T.; Hersey, J. B.; Tharp, Marie

doi:10.1016/0011-7471(64)91079-4

Cited by 45 publications

(25 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The valley floor is just over 5000 m deep at the western ridgetransform intersection, and 5500 m at the eastern intersection. It exceeds 7000 m near 20°W and reaches a maximum of 7800 m near 18 ° 30' W in "Vema Deep" (Heezen et al, 1964). The valley is thus longitudinally asymmetric, being generally deeper and wider at its eastern end.…”

Section: Transform Valleymentioning

confidence: 98%

“…The transform fault zone does not follow the topographic axis of the transform valley, being located north of this axis over the western 720 km of the transform valley and south of it over the remainder of its length. The zone crosses the topographic axis of the transform valley near 18 ° 40'W, which corresponds to the sedimented Vema Deep (Heezen et al, 1964).…”

Section: Transform Fault Zonementioning

confidence: 99%

See 1 more Smart Citation

Morphology and tectonics of the Romanche Transform and its environs

1994

View full text Add to dashboard Cite

Abstract.We describe the results of GLORIA surveys of the Romanche Transform and neighbouring areas of the Equatorial Atlantic Ocean. These surveys have imaged the whole of the Romanche Transform Fault, the eastern end of the Saint Paul Transform, the spreading centre joining them, and the northern part of the spreading centre between Romanche and Chain transforms. They have also imaged representative parts of the off-axis seafloor structure in these areas, and have facilitated preparation of a new bathymetric map, which is presented here. Contrary to previous descriptions of the area, we have found that there is 'normal' spreading fabric (volcano-tectonic lineaments trending NNW-SSE orthogonal to the spreading direction) between these major equatorial fracture zones. This implies that normal seafloor spreading processes have operated there. The Romanche Transform Domain, within which normal spreading fabric is either absent or heavily modified, and transform-related structures predominate, is about 100 km wide. There are multiple transform faults within Saint Paul Fracture Zone, of which we have imaged the active traces of the two southernmost ones. These transforms are joined by short but otherwise normal spreading segments. The Romanche Transform is shorter than previously thought, with a length of 840 km. This is equivalent to an age offset of about 50 Ma. The transform has a complex system of short normal and oblique spreading centres at its eastern intersection, forming an overall oblique section of ridge which may have recently cut off the corner of an earlier, simple, orthogonal ridge-transform intersection. The recent complex system appears to have developed at about 1.5 Ma. An oblique valley is mapped south of the western end of Romanche Transform, and is thought to be the fracture zone trace of an old transform offset between Romanche and Chain transforms. This transform disappeared at about chron 8 (26.9 Ma), as its trace is not seen between 20°W and the spreading centre.

show abstract

Section: Transform Valleymentioning

confidence: 98%

Section: Transform Fault Zonementioning

confidence: 99%

Morphology and tectonics of the Romanche Transform and its environs

1994

View full text Add to dashboard Cite

show abstract

“…After reaching the equatorial zone at the northern periphery of the Brazil basin, this flow divides into two branches (Figure a). One branch crosses the MAR through the Romanche and Chain fractures (Heezen et al, ; Mantyla & Reid, ; Mercier & Speer, ; Messias et al, ), and another branch continues its northward propagation in the West Atlantic (Hall et al, ; Heezen et al, ; Limeburner et al, ; Mantyla & Reid, ; McCartney et al, ; Vangriesheim, ; Whitehead & Worthington, ). The core of this flow in the Northern Hemisphere deflects to the right in accordance with the geostrophic balance; it is confined to the North Atlantic Ridge.…”

Section: Introductionmentioning

confidence: 99%

Structure of the Deep Spillway in the Western Part of the Romanche Fracture Zone

et al. 2018

View full text Add to dashboard Cite

Structure of the deep spillway was studied on the basis of conductivity‐temperature‐depth, lowered acoustic Doppler current profiler, and mooring measurements in 2011–2014 in the Romanche fracture zone (22°27′–22°32′W). The spillway exists quasi‐permanently in the regime of hydraulic control overflow and consists of two flows in the layer θ < 1.20 °C (deeper than 4,150 m). The first flow enters the fracture from the south through a gap in the Southern Wall. The second flow is directed to the east along the narrow valley of the fracture. The sill depths of these passages are 4,570 and 4,430 m, respectively. The depths over the surrounding ridges are shallower than 4,100 m. Both flows descend to the local depression of the fracture with 5,000‐m depth. Bottom potential temperatures over both sills were 0.51 °C, and the measured velocities were 20–40 cm/s. When the flows descend down the slope, they accelerate in supercritical regime. Maximal measured velocities were up to 65 cm/s. Analysis of the 189‐day time series of velocities on the mooring deployed in the flow descending from the gap showed a very high level of fluctuation energy: 10 times greater than the energy of the barotropic tide at this point. The only energy source of these fluctuations is the available potential energy of the deep thermocline in the West Atlantic transforming to the kinetic energy of the deep spillway. The total transport of the bottom water below θ = 1.2 °C based on the lowered acoustic Doppler current profiler measurements is estimated at 0.29–0.35 Sv, which agrees with the predicted values.

show abstract

“…The cause of this ambiguous usage may reflect the fact that the well-defined topography of oceanic fracture zones can become obscured along continental margins where fracture zones are buried under heavily sedimented continent-ocean boundaries (Le Pichon and Hayes 1971). In purely oceanic settings fracture zones were initially defined to include transform segments (e.g., Heezen 1964). However, other workers have limited the definition of a fracture zone to include only the inactive trace of transform faults (e.g., Detrick et al 1993).…”

Section: Introductionmentioning

confidence: 99%

Sheared continent–ocean margins: an overview

Lorenzo

1997

Geo-Marine Letters

View full text Add to dashboard Cite

Continent-ocean fracture zones are the fossil transform offsets located along passive rifted continental margins. Kinematic models identify at least two principal stages in their evolution. During the first stage as rifting proceeds, continent-continent shearing dominates a narrow region in which the transform fault will eventually rupture. High-standing continental marginal ridges 50-100 km wide and bounding deep sedimentary basins, are derived in such settings. In stage two as sea-floor spreading proceeds, the younger oceanic block slides along the active transform, heating the older continental block, and possibly induces thermal uplift and accompanying denudation. Magnetic injection into the continental block at depth may also induce an isostatic uplift. After ridge-transform intersection time, mechanical coupling between the continental and oceanic blocks may influence the stratigraphy and structure of these margins.

show abstract

Chain and romanche fracture zones

Cited by 45 publications

References 16 publications

Morphology and tectonics of the Romanche Transform and its environs

Morphology and tectonics of the Romanche Transform and its environs

Structure of the Deep Spillway in the Western Part of the Romanche Fracture Zone

Sheared continent–ocean margins: an overview

Contact Info

Product

Resources

About