ISSN:
1573-0581
Keywords:
Romanche
;
transform fault
;
equatorial Atlantic
;
tectonics
;
morphology
;
GLORIA
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Physics
Notes:
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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01270518
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