Seismic stratigraphy and sediment distribution on the Wilkes Land and Terre Adelie margins, East Antarctica
Seismic stratigraphy and sediment distribution on the Wilkes Land and Terre Adelie margins, East Antarctica
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DOI：
10.1016/j.margeo.2006.12.010
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发表时间：
2007-04-16
期刊：
影响因子：
2.9
通讯作者：
O'Brien, P. E.
中科院分区：
文献类型：
--
作者：
Close, D. I.;Stagg, H. M. J.;O'Brien, P. E.
地震反射数据表明，南极洲东部威尔克斯地和特雷阿德利大陆边缘沿着存在两个主要沉积盆地，沉积物厚度超过5 s TWT（> 9 km）。四个地震megasequence确定（MS 4至MS 1），是有界的：基底，不整合面的解释Turonian，Maastrichtian和早中始新世的年龄，和海底。4-5 km厚的裂谷和裂谷前沉积物集中在边缘平行盆地（Sabrina盆地）。根据与澳大利亚边缘的地震对比，该盆地的时代为晚侏罗世至中白垩世。裂谷后的沉积物一般沿边缘和邻近的深海盆地沿着较厚，但在威尔克斯地西部以外的一个主要沉积中心（这里称为巴德海岸盆地（BCB））特别厚。BCB包含最大观测厚度为5 s TWT（-9 km）的裂谷后沉积物，其位置表明沉积物主要来自目前被Totten Glacier.Within裂谷后沉积物占据的冰下盆地，确定了一个主要的区域不整合面，该不整合面被解释为中始新世早期（类似于45 Ma）。虽然以前的一些解释表明，这种不整合标志着东南极洲冰川作用的开始，这里的不整合被解释为在始新世中期的主要全球板块重组和澳大利亚和南极洲之间的海底扩张率的同步急剧增加的产物。没有发现与冰川作用开始有关的地震不整合面，只能通过从下伏剖面和深海钻探项目269号现场推断沉积速率来估计沉积剖面内冰川作用开始的位置。中始新世后剖面比下伏裂谷后剖面厚得多，这被解释为主要是由于与34-9 Ma的多温冰川期相关的非常高的沉积物通量。由区域地震网格得出的沉积物等时线和等厚线图显示，BCB的沉积中心大致向北-在大陆坡之下向南偏转，但在深海盆地之下向东偏转。这一分布表明，深海过程在沿边缘的横向沉积物迁移中很重要。根据沉积物分布推断，其运动方向为西向东。这一方向与现今沿大陆坡沿着上升的边缘流方向相反。(c)2007 Elsevier B. V.保留所有权利。
Seismic reflection data show the existence of two major sedimentary basins along the continental margin of Wilkes Land and Terre Adelie, East Antarctica, that contain more than 5 s TWT (> 9 km) of sediments. Four seismic megasequences are identified (MS4 to MS1) that are bounded by: basement, unconformities of interpreted Turonian, Maastrichtian and early Middle Eocene age, and the seafloor. The 4-5 km thick rift and pre-rift sediments are concentrated in a margin-parallel basin (Sabrina Basin). On the basis of seismic correlation with the Australian margin, this basin is interpreted to be of Late Jurassic to mid-Cretaceous age. The post-rift sediments are generally thick along the margin and in the adjacent deep-ocean basin, but are particularly thick in a major depocentre off west Wilkes Land, named here the Budd Coast Basin (BCB). The BCB contains a maximum observed thickness of 5 s TWT (-9 km) of post-rift sediments and its location suggests that the sediments were largely derived from a sub-glacial basin currently occupied by the Totten Glacier.Within the post-rift sediments, a major regional unconformity is identified that is interpreted to be of early Middle Eocene age (similar to 45 Ma). While some previous interpretations have suggested that this unconformity marks the onset of the glaciation of East Antarctica, the unconformity is interpreted here to be the product of the major global plate reorganisation in the Middle Eocene and the coincident sharp increase in the sea-floor spreading rate between Australia and Antarctica. A seismic unconformity that can be correlated with the onset of glaciation is not identified, and the position of glacial onset within the sedimentary section can only be estimated through the extrapolation of sedimentation rates from the underlying section and from Deep Sea Drilling Project Site 269. The post-Middle Eocene section is much thicker than the underlying post-rift section and this is interpreted to be largely due to the very high sediment fluxes associated with the period of polythermal glaciation from similar to 34-9 Ma.Sediment isochron and isopach maps derived from a regional seismic grid show that the depocentre of the BCB trends approximately north-south beneath the continental slope but is deflected to the east beneath the deep ocean basin. This distribution indicates that deep-marine processes were important in lateral, along-margin sediment transport. A west-to-east direction of movement is inferred by the sediment distribution. This direction is opposite to the present-day marginal currents along the continental slope and rise. (c) 2007 Elsevier B.V. All rights reserved.