Structure of the Transkei Basin and Natal Valley, Southwest Indian Ocean, from seismic reflection and potential field data

被引:11
作者
Reznikov, M [1 ]
Ben-Avraham, Z
Hartnady, C
Niemi, TM
机构
[1] Geophys Inst Israel, Holon, Israel
[2] Univ Cape Town, Dept Geol Sci, ZA-7700 Rondebosch, South Africa
[3] Tel Aviv Univ, Dept Geophys & Planetary Sci, IL-69978 Tel Aviv, Israel
[4] Umvoto Africa, Hydrotecton & Hydroseismol Unit H2U, Muizenberg, South Africa
[5] Univ Missouri, Dept Geosci, Kansas City, MO 64110 USA
关键词
oceanic crust; acoustic basement; mesozoic magnetic anomalies; deformations;
D O I
10.1016/j.tecto.2004.11.002
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
Marine geophysical data from the southern Natal Valley and northern Transkei Basin, offshore southeast Africa, were used to study the structure of the crust and sedimentary cover in the area. The data includes seismic reflection, gravity and magnetics and provides information on the acoustic basement geometry (where available), features of the sedimentary cover and the basin's development. Previously mapped Mesozoic magnetic anomalies over a part of the basin are now recognized over wider areas of the basin. The ability to extend the correlation to the southeast within the Natal Valley further confirms an oceanic origin for this region and provides an opportunity to amplify the existing plate boundary reconstructions. The stratigraphic structure of the southern Natal Valley and the northern Transkei Basin reflects processes of the ocean crust formation and subsequent evolution. The highly variable relief of the acoustic basement may relate to the crust formation in the immediate vicinity of the continental transform margin. Renewed submarine seismicity and neotectonic activity in the area is probably related to the diffuse boundary between the Nubia and Somalia plates. 2.5-D crustal models show that a 1.7-3.2-km-thick sediment sequence overlies a 6.3 +/- 1.2-km-thick normal oceanic crust in the deep southern Natal Valley and Transkei Basin. The oceanic crust in the study area is heterogeneous, made up of blocks of laterally varying remanent magnetization (0.5-3.5 A/m) and density (2850-2900 kg/m(3)). Strong modifications of accretionary processes near ridge/fracture zone intersections may be a reason of such heterogeneity. (c) 2004 Elsevier B.V. All rights reserved.
引用
收藏
页码:127 / 141
页数:15
相关论文
共 43 条
[1]  
[Anonymous], 1974, NATAL S AFR J GEOL
[2]   EARLY TECTONIC EXTENSION BETWEEN THE AGULHAS BANK AND THE FALKLAND PLATEAU DUE TO THE ROTATION OF THE LAFONIA MICROPLATE [J].
BENAVRAHAM, Z ;
HARTNADY, CJH ;
MALAN, JA .
EARTH AND PLANETARY SCIENCE LETTERS, 1993, 117 (1-2) :43-58
[3]   MIDTERTIARY CHANGES IN DEEP-OCEAN CIRCULATION PATTERNS IN THE NATAL VALLEY AND TRANSKEI BASIN, SOUTHWEST INDIAN-OCEAN [J].
BENAVRAHAM, Z ;
NIEMI, TM ;
HARTNADY, CJH .
EARTH AND PLANETARY SCIENCE LETTERS, 1994, 121 (3-4) :639-646
[4]   Stress field changes in the Afro-Arabian rift system during the Miocene to Recent period [J].
Bosworth, W ;
Strecker, MR .
TECTONOPHYSICS, 1997, 278 (1-4) :47-62
[6]  
Chetty P., 1977, Marine Geophysical Researches, V3, P197, DOI 10.1007/BF00310110
[7]   Evidence for motion between Nubia and Somalia along the southwest Indian ridge [J].
Chu, DH ;
Gordon, RG .
NATURE, 1999, 398 (6722) :64-67
[8]  
CORDELL L, 1992, US GEOL SURV POTENTI, P92
[9]  
DARRACOTT BW, 1974, EARTH PLANET SC LETT, V24, P282, DOI 10.1016/0012-821X(74)90106-X
[10]   EFFECT OF RECENT REVISIONS TO THE GEOMAGNETIC REVERSAL TIME-SCALE ON ESTIMATES OF CURRENT PLATE MOTIONS [J].
DEMETS, C ;
GORDON, RG ;
ARGUS, DF ;
STEIN, S .
GEOPHYSICAL RESEARCH LETTERS, 1994, 21 (20) :2191-2194