Middle slope contourite deposits and associated sedimentary facies off NE Argentina
Middle slope contourite deposits and associated sedimentary facies off NE Argentina
复制标题
阿根廷东北部的中坡等高线矿床及相关沉积相
DOI：
--
复制
发表时间：
2011
期刊：
影响因子：
--
通讯作者：
M. E. Cerredo
中科院分区：
文献类型：
--
作者：
G. Bozzano;R. Violante;M. E. Cerredo
阿根廷大陆边缘的特点是由不同水深的南部水团驱动的大型轮廓岩沉积体系。在地球科学和相关领域，对等长岩矿床的兴趣正在增加，尽管对阿根廷等长岩系统的了解仍然有限。特别是缺乏根据岩心资料详细描述沉积相的研究，也缺乏对主要沉积物源区和控制沉积过程的关键因素的调查。本研究结合了目视岩心描述和下岩心粒度分析，以及岩石薄切片和磁化率分析，从616 - 1208米的中间水深对14个岩心进行了分析，以表征阿根廷东北部斜坡上的等长岩矿床。确定了富砾石、砂粉质、泥质等高线岩及半深海相。这些等长岩的沉积可能受海平面、南极水团深度范围、气候条件和风源供给的控制。在冰川低洼区<900 m处沉积了泥质等高岩，而在较深处则以砂质粉质层序为主。在晚更新世-全新世过渡时期，砂粉质等高线覆盖了整个中坡。当海平面达到现在的位置时，半深海相覆盖了中间斜坡的有限部分，富含砾石的等高岩被限制为等高岩河道和护城河。北巴塔哥尼亚和南潘帕是沿坡过程沉积的最可能的沉积物来源，而坦迪利亚山脉是沿坡过程沉积的最佳候选沉积物。
The Argentine continental margin is characterised by a large contourite depositional system driven by southern-sourced water masses flowing at different water depths. Interest in contourite deposits is increasing in geoscience and related fields, though knowledge of the Argentine contourite system is still limited. In particular, studies based on core data providing detailed descriptions of sedimentary facies are lacking, as are investigations of principal sediment source areas and of key factors controlling sedimentary processes. This study combines visual core description and downcore grain-size analyses as well as petrographic thin-section and magnetic susceptibility analyses of 14 cores from intermediate water depths of 616–1,208 m to characterise contourite deposits on the north-eastern Argentinean slope. Gravel-rich, sandy–silty and muddy contourites as well as hemipelagic facies were identified. The deposition of these contourites was presumably controlled by sea level, the depth range of the Antarctic water mass, climate conditions and windborne terrigenous supply. It is proposed that, during glacial lowstands, muddy contourites were deposited at depths <900 m, whereas sandy–silty sequences dominated at deeper depths. During the late Pleistocene–Holocene transition, sandy–silty contourites covered the entire middle slope. Hemipelagic facies draped limited sectors of the middle slope when the sea level reached the present-day position and gravel-rich contourites became restricted to contouritic channels and moats. Northern Patagonia and the southern Pampa are the most plausible sources for sediments deposited via along-slope processes, whereas the Tandilia Range is the best candidate for sediments deposited via down-slope processes.