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Sedimentary evolution of the Le Danois contourite drift systems (southern Bay of Biscay, NE Atlantic): A reconstruction of the Atlantic Mediterranean Water circulation since the Pliocene
Marine Geology ( IF 2.6 ) Pub Date : 2020-05-12 , DOI: 10.1016/j.margeo.2020.106217
Shan Liu , F. Javier Hernández-Molina , Gemma Ercilla , David Van Rooij

The evolution of the Le Danois contourite depositional systems (CDS) during the Pliocene and Quaternary was investigated based on high-resolution seismic reflection data. From old to young, six seismic units (U1–U6) bounded by major discontinuities (H1–H6) were identified. Regarding variations of the bottom-current circulation, four evolution stages of the Le Danois CDS were identified, including onset (~5.3 to 3.5–3.0 Ma), initial (3.5–3.0 to 2.5–2.1 Ma), intermediate (2.5–2.1 to 0.9–0.7 Ma) and drift-growth (0.9–0.7 Ma to present day) stages. The CDS associated with the Atlantic Mediterranean Water (AMW) along the middle continental slope initiated at ~3.5–3 Ma and was widely built after the Mid-Pleistocene Transition (MPT; 0.9–07 Ma). At a shallower water depth, a second CDS associated with the Eastern North Atlantic Central Water (ENACW) started to develop from the late Quaternary (~0.47 Ma) onwards. In the AMW-related drift system, the Le Danois Drift was generated both under glacial and interglacial climatic oscilations. Repeated internal structures in unit 5 that consist of acoustically transparent lower parts, moderate amplitude upper parts and high amplitude erosional surfaces at the top, are compared with interglacial/glacial cycles since the middle Pleistocene to the present day. These cyclic features suggest coarsening-upward sequences of the Le Danois Drift and processes related to enhanced AMW during glacial stages. The estimated sedimentation rate of the Le Danois CDS reached a maximum during the MPT (at least ~27 cm/ky) and then decreased until present-day (~5 cm/ky). Variations of sedimentary stacking patterns and processes of the Le Danois CDS imply full domination of the intermediate water mass along the central Atlantic and southwest European continental slopes from the late Pliocene (~3.5–3.0 Ma) onwards.



中文翻译:

Le Danois等高线漂移系统的沉积演化(北比斯开南部湾,东北大西洋):上新世以来大西洋地中海水循环的重建

基于高分辨率地震反射数据,研究了上新世和第四纪Le Danois等高体沉积系统(CDS)的演化。从大到小,确定了以主要不连续性(H1-H6)为边界的六个地震单元(U1-U6)。关于底流的变化,确定了Le Danois CDS的四个演化阶段,包括开始(〜5.3至3.5-3.0 Ma),初始(3.5-3.0至2.5-2.1 Ma),中间(2.5-2.1至0.9-0.7 Ma)和漂移生长(今天为0.9-0.7 Ma)阶段。与中大西洋大陆斜坡上的大西洋地中海水(AMW)相关的CDS始于〜3.5–3 Ma,并在中更新世过渡(MPT; 0.9–07 Ma)之后广泛建立。在浅水深度,从第四纪晚期(〜0.47 Ma)开始,与东部北大西洋中央水域(ENACW)相关的第二个CDS开始发展。在与AMW有关的漂流系统中,Le Danois漂流是在冰川和冰川间气候振荡的作用下产生的。从中更新世至今,将单元5中重复的内部结构(由透声的下部,中等振幅的上部和顶部的高振幅侵蚀表面组成)与冰川/冰川循环进行了比较。这些周期性特征提示了Le Danois Drift的向上粗化序列以及与冰川期AMW增强有关的过程。Le Danois CDS的估计沉降速率在MPT期间达到最大值(至少〜27 cm / ky),然后一直下降到今天(〜5 cm / ky)。

更新日期:2020-05-12
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