Structure of Colombia Basin, Caribbean Sea, from profiler‐sonobuoy measurements
Structure of Colombia Basin, Caribbean Sea, from profiler‐sonobuoy measurements
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DOI：
10.1029/jb082i030p04861
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发表时间：
1977-10
影响因子：
--
通讯作者：
R. Houtz;W. Ludwig
中科院分区：
文献类型：
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作者：
R. Houtz;W. Ludwig
根据沿着哥伦比亚盆地西南走向的26个气枪/声纳浮标剖面计算地震速度和地层深度。穿透到更深的地壳层和上地幔实现了一个大的气枪声源。哥伦比亚盆地的地壳结构是一个复杂的基底脊和插入盆地的安排，被厚厚的覆盖层，平坦的沉积物所掩盖。早期的两艘船折射站无意中位于基底山脊上，这导致了错误的结论，即盆地包含异常厚的地壳。地幔折射从两个声纳浮标配置文件在盆地的未受干扰的部分表明，一个正常的海洋地壳已被压低了约3公里的沉积物。哥伦比亚盆地的反射记录表明，基底岩石有相当大的起伏，不像委内瑞拉盆地的光滑B“（声学基底）表面。此外，在委内瑞拉盆地的沉积物中没有一致的反射层可以与层位A″对比。沉积物中的声速在14°N以南以正常速率增加，但在没有中间（层位A″型）反射体的北部，由于高速沉积层上的覆盖层较薄，增加速率异常高。因此，在哥伦比亚盆地目前的工作中，没有遵循层位A“和B”的用法。
Seismic velocities and layer depths were computed from 26 air gun/sonobuoy profiles made along a southwesterly traverse of the Colombia basin. Penetration to the deeper crustal layers and the upper mantle was achieved with a large air gun sound source. The crustal structure of the Colombia basin is a complex arrangement of basement ridges and interposed basins that is masked by an overburden of thick, flat-lying sediments. Earlier two-ship refraction stations were inadvertently located on the basement ridges, which had led to the mistaken conclusion that the basin contains unusually thick crust. Mantle refractions from two sonobuoy profiles in the undisturbed parts of the basin suggest a normal oceanic crust that has been depressed by the addition of about 3 km of sediment. The reflection records from the Colombia basin show that the basement rocks have considerable relief, unlike the smooth B″ (acoustic basement) surface in the Venezuela basin. Furthermore, there is no consistent reflector in the sediments that can be correlated with horizon A″ in the Venezuela basin. Sound velocity in the sediments increases at a normal rate south of about 14°N, but to the north where there is no intermediate (horizon A″ type) reflector, the rate of increase is unusually high, owing to a thinner overburden on a high-speed sediment layer. Accordingly, the horizon A″ and B″ usage is not followed in the present work in the Colombia basin.