Sedimentary model for mixed depositional systems along the Pacific margin of the Antarctic Peninsula: Decoding the interplay of deep-water processes
Sedimentary model for mixed depositional systems along the Pacific margin of the Antarctic Peninsula: Decoding the interplay of deep-water processes
复制标题
南极半岛太平洋边缘混合沉积系统的沉积模型：解码深水过程的相互作用
DOI：
10.1016/j.margeo.2022.106754
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发表时间：
2022
期刊：
影响因子：
2.9
通讯作者：
Rodrigues S
中科院分区：
文献类型：
--
作者：
Rodrigues S
混合（浊积岩-等深岩）沉积体系是由深水过程的复杂相互作用形成的。对其形态要素及其横向和空间分布的评价，对于更好地了解运输和沉积过程的相互作用至关重要，包括顺坡底流和下坡浊流。本文研究了沿着南极半岛太平洋边缘发育的广泛而活跃的混合沉积体系，包括大型不对称丘状漂积物、树枝状河道复合体系和宽干河道。这些系统提供了一个独特的环境，可利用多波束测深和声学海底下剖面图，在高分辨率空间尺度（10-100米）调查各种形态要素。4个主要地震单元划分了从更新世到现今的不同演化阶段：a）1.3-1 Ma，主要由沿斜坡的底流形成的堆积丘状漂积体，B）1- 0.6Ma，主要由SW向底流和NW向浊流的同步相互作用形成; c）0.6-0.2 Ma，特征为在弱SW流动底流（包括改良的下绕极深水（LCDW））下，在边缘沉积厚重力沉积物;和d）0.2 Ma -目前，当底流，其特征是流速波动，和短暂的浊流之间的同步相互作用，导致浊积岩，等深流，改造浊积岩沉积和半长岩的夹层。地层堆积模式的交替表明重力驱动的下坡过程和沿坡底流的周期性时空变化，这是负责这些现代混合沉积体系的建设，而这些体系本身又受到冰川-间冰期变化的控制。新的研究结果与类似的混合沉积体系进行了比较，以解码其形成过程中所涉及的主要过程，探索它们在短期和长期时间尺度上的相互作用，并提出了一个概念性的沉积模型。
Mixed (turbidite-contourite) depositional systems are formed by a complex interplay of deep-water processes. An evaluation of their morphological elements and their lateral and spatial distribution is crucial to better understand the interplay of transport and depositional processes, involving along-slope bottom currents and down-slope turbidity currents. This work investigates extensive and still active mixed depositional systems developed along the Pacific margin of the Antarctic Peninsula, which comprise large asymmetric mounded drifts, dendritic channel-complex systems and wide trunk channels. These systems offer a unique setting to investigate diverse morphological elements at a high-resolution spatial scale (10–100 m), using multibeam bathymetry and acoustic sub-bottom profiles. Four main seismic units define distinct evolutionary stages for the Pleistocene to present day record: a)1.3–1 Ma, characterized by aggradational mounded drifts built by a dominant along-slope bottom current; b)1–0.6 Ma, built by synchronous interactions between a SW-flowing bottom current and NW-directed turbidity currents; c)0.6–0.2 Ma, characterized by deposition of thick gravitational deposits across the margin under a weak SW-flowing bottom current comprising modified Lower Circumpolar Deep Water (LCDW); and d)0.2 Ma – present, when synchronous interactions between the bottom current, characterized by flow speed fluctuations, and ephemeral turbidity currents led to intercalations of turbidites, contourites, reworked turbidite deposits and hemipelagites. Alternations in the stratigraphic stacking pattern suggest cyclic spatial and temporal variations of gravity-driven down-slope processes and along-slope bottom currents, which were responsible for the construction of these modern mixed depositional systems and which themselves were controlled by glacial-interglacial changes. The new results are compared with similar mixed depositional systems to decode the main processes involved in their formation, explore their interactions at short- and long-term time scales, and propose a conceptual sedimentary model.