Abstract
The basement topography and the free-air gravity along two profiles in the central North Atlantic between 16° and 25° N, crossing a number of fracture zones, were divided in three wavelength intervals. Two-dimensional modelling shows that the short wavelength (>50 km) gravity is well explained by uncompensated topography (mainly spreading topography). For the long wavelengths (>200 km) there is no correlation of topography and gravity. In principle this topography is compensated. Residual anomalies comprise the Ridge effect as well as regional anomalies related to depth anomalies. The 50 to 200km band-pass filtered topography and gravity contain relevant information on fracture zones. Models require a base of the crust that parallels the topography rather than a form of regional compensation. For an explanation of this crustal model that has the appearance of ‘frozen in’ normal faults we have to consider the typical morphology as created in the transform domain. The geophysical processes that cause this morphology are still an object of study.
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References
Cochran, J. R.: 1973, ‘Gravity and Magnetic Investigations in the Guiana Basin, Western Equatorial Atlantic’, Geol. Soc. Amer. Bull. 84, 3249–3268.
Cochran, J. R. and Talwani, M.: 1977, ‘Free-Air Gravity Anomalies in the World's Oceans and Their Relationship to Residual Elevation’, Geophys. J. Roy. Astron. Soc. 50, 495–552.
Cochran, J. R. and Talwani, M.: 1978, ‘Gravity Anomalies, Regional Elevation, and the Deep Structure of the North Atlantic’, J. Geophys. Res. 83, 4907–4924.
Collette, B. J.: 1980, ‘Structure and Development of the African Plate in the Central North Atlantic’, in 26e Congrès Geologique Internationale, Abstracts, Paris, II, 715.
Collette, B. J., Verhoef, J., and deMulder, A. F. J.: 1980, ‘Gravity and a Model of the Median Valley’, J. Geophys. Res. 47, 91–98.
Collette, B. J., Slootweg, A. P., Verhoef, J., and Roest, W. R.: 1984, ‘Geophysical Investigations of the Floor of the Atlantic Ocean between 10° and 38° N (Kroonvlag-project)’, Proc. Kon. Ned. Ak. Wet., Series B 86, 1–76, Amsterdam.
Detrick, R. S.Jr. and Purdy, G. M.: 1980, ‘The Crustal Structure of the Kane Fracture Zone from Seismic Refraction Studies’, J. Geophys. Res. 85, 3759–3777.
Detrick, R. S. and Cormier, M. H.: 1983, ‘Seismic Constraints on the Crustal Structure within the Vema Fracture Zone’, J. Geophys. Res. 87, 599–612.
Diament, M.: 1981, ‘Etude de la Réponse isostatique en domain océanique et applications à trois zones de fractures de l'Atlantique’, Thèse doct. 3e cycle, Université de Paris-Sud, Paris.
Fox, P. J., Schreiber, E., Rowlett, H., and McCamy, K.: 1976, ‘The Geology of the Oceanographer Fracture Zone: A Model for Fracture Zones’, J. Geophys. Res. 81, 4117–4128.
Francis, T. J. G.: 1981, ‘Serpentinization Faults and Their Role in the Tectonics of Slow Spreading Ridges’, J. Geophys. Res. 86, 616–622.
Kogan, M. G. and Kostoglodov, V. V.: 1981, ‘Isostasy of Fracture Zones in the Atlantic Ocean’, J. Geophys. Res. 86, 9248–9258.
Louden, K. E. and Forsyth, D. W.: 1982, ‘Crustal Structure and Isostatic Compensation near the Kane Fracture Zone from Topography and Gravity Measurements’, Geophys. J. Roy Astron. Soc. 68, 725–750.
McKenzie, D. P. and Bowin, C.: 1976, ‘The Relationship Between Bathymetry and Gravity in the Atlantic Ocean’, J. Geophys. Res. 81, 1903–1915.
Robb, J. M. and Kane, M. F.: 1975, ‘Structure of the Vema Fracture Zone from Gravity and Magnetic Intensity Profiles’, J. Geophys. Res. 80, 4441–4445.
Sandwell, D. T. and Schubert, G.: 1982a, ‘Geoid Height-Age Relation from SEASAT Altimeter Profiles across the Mendocino Fracture Zone’, J. Geophys. Res. 87, 3949–3958.
Sandwell, D. and Schubert, G.: 1982b, ‘Lithospheric Flexure at Fracture Zones’, J. Geophys. Res. 87, 4657–4667.
Sclater, J. G. and Francheteau, J.: 1970, ‘The Implications of Terrestrial Heat Flow Observations on Current Tectonic and Geochemical Models of the Crust and Upper Mantle of the Earth’, Geophys. J. Roy. Astron. Soc. 20, 509–542.
Searle, R. C. and Laughton, A. S.: 1977, ‘Sonar Studies of the Mid-Atlantic Ridge and the Kurchatov Fracture Zone’, J. Geophys. Res. 82, 5313–5328.
Sibuet, J. C. and Veyrat-Peiney, B.: 1980, ‘Gravimetric Model of the Atlantic Equatorial Fracture Zones’, J. Geophys. Res. 85, 943–954.
Sinha, M. C.: 1981, ‘The Seismic Structure of Aseismic Ridges and Fracture Zones’, Ph. D. thesis, University of Cambridge, Cambridge.
Talwani, M., Worzel, J. L., and Landisman, M.: 1959, ‘Rapid Gravity Computations for Two-Dimensional Bodies with Application to the Mendocino Submarine Fracture Zone’, J. Geophys. Res. 64, 49–59.
Twigt, W., Verhoef, J., Rohr, K., Mulder, Th. F. A., and Collette, B. J.: 1983, ‘Topography and Magnetics over the Kane Fracture Zone in the Cretaceous Magnetic Quiet Zone (African plate)’, Proc. Kon. Ned. Ak. Wet., Series B 86, 181–210, Amsterdam.
VanAndel, Tj. H., vonHerzen, R. P., and Phillips, J. D.: 1071, ‘The Vema Fracture Zone and the Tectonics of Transverse Shear Zones in Oceanic Crustal Plates’, Mar. Geophys. Res. 1, 261–283.
Whitmarsh, R. B. and Laughton, A. S.: 1976, ‘A long Range Sonar Study of the Mid-Atlantic Ridge Crest near 37° N (FAMOUS area) and its Tectonic Implications’, Deep Sea Res. 23, 1005–1023.
White, R. S. and Matthews, D. H.: 1980, ‘Variations in Oceanic Upper Crustal Structure in a small Area of the Northeastern Atlantic’, Geophys. J. Roy. Astron. Soc. 61, 401–435.
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Mulder, T.F.A., Collette, B.J. Gravity anomalies over inactive fracture zones in the central North Atlantic. Mar Geophys Res 6, 383–394 (1984). https://doi.org/10.1007/BF00286251
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DOI: https://doi.org/10.1007/BF00286251