淹没的屏障和山谷:南大西洋西部海平面变化的形态档案

IF 2.6 3区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Marine Geology Pub Date : 2024-09-24 DOI:10.1016/j.margeo.2024.107404
Antonio R. Ximenes Neto , Valéria S. Quaresma , Pedro S. Menandro , Paulo H. Cetto , Alex C. Bastos
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引用次数: 0

摘要

保存在大陆架上的淹没古海岸和河流地貌是第四纪海平面变化的重要指标。利用多波束测深数据作为基本数据集,对巴西东南大陆架上的古海岸和河流淹没地貌进行了形态学分析。目的是研究切谷与水下障碍物之间的相互作用及其时间关系。观测到六个部分被填平的切谷,具有蜿蜒曲折的特征,河道切口长达 40 米,包括与蜿蜒曲折有关的几种形态(如点状条形、颈状、切槽)。在四个深度范围(DR)发现了古海岸特征,主要与障碍物有关,呈倾角方向:DR1(60 米);DR2(55 米-60 米);DR3(50 米-55 米);DR4(45 米-50 米)。地貌结果表明,山谷和海岸屏障共存,较低和较窄的屏障往往出现在陆架断裂附近。切谷与海岸屏障之间的初步地貌演变包括两种可能的起源:I) DR 2-4 的古海岸地貌是在 MIS 3-5 的海平面间期波动中形成的,和/或具有不同基底面周期的多个成因阶段。山谷有两个阶段的切口与大陆架断裂以下的基底面下降有关:浅切口(阶地)为 MIS 4,主切口为 MIS 2。此外,DR 1 的发展与后大地构造时期的基面上升有关;(II) 所有沉积海岸地貌(DR 1-4)和河流地貌都是在后大地构造时期基面上升过程中形成的(即河流和海岸动力学处于同一基面变化周期)。基面变化的多个阶段引起山谷切裂和屏障形成的阶段,更有可能是一种更好的解释。从这个角度看,利用古海岸和河流地貌中的沉积岩芯进行地质年代研究,对于验证这些假设是至关重要的,从而有助于填补大西洋西缘形态沉积对基底变化响应方面的知识空白。
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Drowned barriers and valleys: A morphological archive of base level changes in the western South Atlantic
Drowned paleo-coastal and fluvial landforms preserved on continental shelves are important indicators of sea-level changes during the Quaternary. Morphological analyses of paleo-coastal and fluvial submerged features using multibeam bathymetry as basic datasets, were carried out on the Southeast Brazilian Shelf. The aim was to investigate the interaction between incised valleys and submerged barriers and their temporal relationship. Six partially infilled incised valleys with sinuous and meandering features, and up to ∼40 m of fluvial incision were observed, including several morphologies associated with meanders (e.g., point bars, neck, cut-bank). Paleo-coastal features, mainly related to barriers, were found at four depth ranges (DR) in a dip orientation: DR1 (>60 m); DR2 (55 m–60 m); DR3 (50 m–55 m); DR4 (45 m–50 m). The geomorphic results show that valleys and coastal barriers coexisted and that lower and narrower barriers tend to occur near the shelf break. Preliminary geomorphic evolution between incised valleys and coastal barriers encompasses two possible origins: I) paleo-coastal features of DR 2–4 developed during the interstadial fluctuations of sea-level in MIS 3–5 and/or multiple genetic phases with different base level cycles. The valleys had two phases of incisions related to the base level drop below the shelf break: MIS 4 in the shallow incisions (terraces) and MIS 2 in the main incisions. Moreover, the development of DR 1 was related to the post-LGM base level rise; II) All submerged coastal (DR 1–4) and fluvial features developed during post-LGM base level rise (i.e., fluvial and coastal dynamics in the same cycle of base level change). The multiple phases of base-level changes inducing phases of valley incisions and barrier formation is more likely the be a better explanation. From this perspective, geochronological studies using sedimetary cores in the paleo-coastal and fluvial features are crucial to validate these scenarios, and thus contributing to fill knowledge gaps regarding morphosedimentary responses to base-level changes on the western Atlantic margin.
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来源期刊
Marine Geology
Marine Geology 地学-地球科学综合
CiteScore
6.10
自引率
6.90%
发文量
175
审稿时长
21.9 weeks
期刊介绍: Marine Geology is the premier international journal on marine geological processes in the broadest sense. We seek papers that are comprehensive, interdisciplinary and synthetic that will be lasting contributions to the field. Although most papers are based on regional studies, they must demonstrate new findings of international significance. We accept papers on subjects as diverse as seafloor hydrothermal systems, beach dynamics, early diagenesis, microbiological studies in sediments, palaeoclimate studies and geophysical studies of the seabed. We encourage papers that address emerging new fields, for example the influence of anthropogenic processes on coastal/marine geology and coastal/marine geoarchaeology. We insist that the papers are concerned with the marine realm and that they deal with geology: with rocks, sediments, and physical and chemical processes affecting them. Papers should address scientific hypotheses: highly descriptive data compilations or papers that deal only with marine management and risk assessment should be submitted to other journals. Papers on laboratory or modelling studies must demonstrate direct relevance to marine processes or deposits. The primary criteria for acceptance of papers is that the science is of high quality, novel, significant, and of broad international interest.
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