Ocean basins near the Scotia–Antarctic plate boundary: Influence of tectonics and paleoceanography on the Cenozoic deposits
Ocean basins near the Scotia–Antarctic plate boundary: Influence of tectonics and paleoceanography on the Cenozoic deposits
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斯科舍-南极板块边界附近的海洋盆地：构造和古海洋学对新生代沉积物的影响
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
J. Vázquez
中科院分区：
文献类型：
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作者：
A. Maldonado;F. Bohoyo;J. Galindo‐Zaldívar;J. Hernández;A. Jabaloy;F. Lobo;J. Rodríguez;E. Suriñach;J. Vázquez
通过对多道地震反射剖面的分析，描述了舌状板块-斯科舍板块边界附近盆地沉积物中地震单元的分布。识别出5个主要地震单元。这些单元以高振幅连续反射体为界，从上到下命名为a至d。这两个较老的单元在每个盆地中具有不同的时代和地震相，通常在活动裂谷和海底扩张期间沉积。相比之下，三个最年轻的单元（3到1）表现出相当相似的地震相，可以在区域尺度上进行对比。这些沉积物是威德尔海底层水（WSBW）向东北流动与北方威德尔海复杂水深相互作用以及南极绕极流和斯科舍海WSBW影响下的等深漂积物。在中新世中期，Reflector c记录了一个重大的古海洋学事件，这代表了简盆地打开后斯科舍海和威德尔海之间的连接。第3单元（暂定为中新世中期至晚中新世）显示了WSBW最初侵入斯科舍海，与下伏沉积物形成对比，这影响了向北的横向格局。反射体B的年龄与西斯科舍海岭扩张的结束时间一致（约6.4 Ma）。第2单元（年代为1990 - 1999年，中新世晚期至上新世早期）包括威德尔海北方丰富的高能席状沉积物，这可能反映了西南极冰盖向大陆架推进的结果，即西南极冰盖的产量较高。反射面a代表最后一次主要的区域性古海洋学变化。这一事件的发生时间（距今3.5-3.8 Ma）与凤凰-南极海脊扩张的结束相吻合，但也可能与全球性事件有关，如永久性北方半球冰盖的形成和海平面的大幅下降。1号单元（年代为1990 - 1999年，上新世晚期至近代）的特征是，除了各种等深流岩外，还存在大量混乱的高能席状沉积，这表明深水开采得到了加强。此外，单元1和单元2还显示出一种循环模式、更丰富的波状沉积和内部不整合的发育，所有这些都证明了底流能量增加的交替周期。
The distribution of seismic units in deposits of the basins near the Antarctic–Scotia plate boundary is described based on the analysis of multichannel seismic reflection profiles. Five main seismic units are identified. The units are bounded by high-amplitude continuous reflectors, named a to d from top to bottom. The two older units are of different age and seismic facies in each basin and were generally deposited during active rifting and seafloor spreading. The three youngest units (3 to 1) exhibit, in contrast, rather similar seismic facies and can be correlated at a regional scale. The deposits are types of contourite drift that resulted from the interplay between the northeastward flow of Weddell Sea Bottom Water (WSBW) and the complex bathymetry in the northern Weddell Sea, and from the influence of the Antarctic Circumpolar Current and the WSBW in the Scotia Sea. A major paleoceanographic event was recorded by Reflector c, during the Middle Miocene, which represents the connection between the Scotia Sea and the Weddell Sea after the opening of Jane Basin. Unit 3 (tentatively dated ∼Middle to Late Miocene) shows the initial incursions of the WSBW into the Scotia Sea, which influenced a northward progradational pattern, in contrast to the underlying deposits. The age attributed to Reflector b is coincident with the end of spreading at the West Scotia Ridge (∼6.4 Ma). Unit 2 (dated ∼Late Miocene to Early Pliocene) includes abundant high-energy, sheeted deposits in the northern Weddell Sea, which may reflect a higher production of WSBW as a result of the advance of the West Antarctic ice-sheet onto the continental shelf. Reflector a represents the last major regional paleoceanographic change. The timing of this event (∼3.5–3.8 Ma) coincides with the end of spreading at the Phoenix–Antarctic Ridge, but may be also correlated with global events such as initiation of the permanent Northern Hemisphere ice-sheet and a major sea level drop. Unit 1 (dated ∼Late Pliocene to Recent) is characterized by abundant chaotic, high-energy sheeted deposits, in addition to a variety of contourites, which suggest intensified deep-water production. Units 1 and 2 show, in addition, a cyclic pattern, more abundant wavy deposits and the development of internal unconformities, all of which attest to alternating periods of increased bottom current energy.