Origin of the northwestern Bahama Platform; review and reinterpretation
Origin of the northwestern Bahama Platform; review and reinterpretation
复制标题
巴哈马地台西北部的起源；
DOI：
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发表时间：
1977
期刊：
影响因子：
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通讯作者：
G. W. Lynts
中科院分区：
文献类型：
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作者：
H. T. Mullins;G. W. Lynts
《巴哈马纲领》的起源是一个世纪以来争论的主题。主要的分歧点是：（1）巴哈马基底是大陆基底还是海洋基底;（2）巴哈马深海水道的年龄和起源。地球物理数据仅表明巴哈马基底具有中等密度、地震速度和厚度。我们建议，这个基底最初是前三叠纪的大陆材料，是普遍侵入的镁铁质和超镁铁质物质在裂谷的北美从非洲和南美洲在晚三叠世的时间。为了减轻北大西洋重建过程中的巴哈马重叠，我们认为巴哈马地台在白垩纪和第三纪早期由于加勒比板块的相对撞击运动而向东北旋转了约25°。由于这种假定的旋转，巴哈马地台在非洲和南美洲之间形成了一个极好的配合。我们提出了以下模式的起源西北巴哈马平台：（1）该平台是大陆的，最初是非洲的一部分。(2)在晚三叠世期间，北美洲从非洲和南美洲的裂谷开始于巴哈马西北部附近，在此之前，大陆的大穹状隆起引发了作为地堑的巴哈马海峡。(3)巴哈马地台主要沿着一条大的右旋剪切带从非洲大陆裂陷而成，并由此演化为一个横推型大陆边缘。(4)在巴哈马深水水道的早期发育过程中，这些地堑底部沉积了晚三叠世的大陆长石纹质铷粒岩和砂粒岩;（5）早至中侏罗世的初始海洋条件可能导致由于循环受限而在水道中沉积了富含盐和有机质的页岩。(6)随着更开阔的海洋条件的出现，3至6公里的侏罗纪至全新世深水碳酸盐和生物碎屑浊积岩沉积物沉积在河道中。(7)巴哈马西北部的大部分台内地形似乎是区域沉降期间相对于通道的堤岸堆积的结果。
The origin of the Bahama Platform has been the subject of debate for more than a century. The major points of disagreement are (1) whether the Bahamian basement is continental or oceanic, and (2) the age and origin of the deep Bahama channels. Geophysical data indicate only that the Bahamian basement is of intermediate density, seismic velocity, and thickness. We propose that this basement was originally pre-Triassic continental material that was pervasively intruded by mafic and ultramafic material during the rifting of North America from Africa and South America in Late Triassic time. To alleviate the Bahama overlap in reconstructions of the North Atlantic we suggest that the Bahama Platform has been rotated approximately 25° to the northeast by the relative impinging motion of the Caribbean plate during Cretaceous and early Tertiary time. By accounting for this postulated rotation, the Bahama Platform forms an excellent fit between Africa and South America. We propose the following model for the origin of the northwestern Bahama Platform: (1) The platform is continental and was originally part of Africa. (2) Rifting of North America from Africa and South America began in the vicinity of the northwestern Bahamas during the Late Triassic, preceded by a large domal uplift of the continents that initiated the deep Bahama Channels as grabens. (3) The Bahama Platform rifted from Africa principally along a large right-lateral shear and thus evolved as a transcurrent-type continental margin. (4) During the incipient development of the deep Bahama channels, Late Triassic continental arkosic rudites and arenites were deposited at the base of these grabens; (5) Initial marine conditions in Early to Middle Jurassic time may have resulted in the deposition of salt and organic-rich shales in the channels due to restricted circulation. (6) With the onset of more open marine conditions 3 to 6 km of Jurassic to Holocene deep-water carbonate and bioclastic turbidite sediments were deposited in the channels. (7) Most of the intraplatform relief of the northwestern Bahamas appears to be the result of the build-up of the banks relative to the channels during regional subsidence.