Sediment recycling and adjustment of deposition during deglacial drowning of a low-accumulation shelf (NW Iberia)
Sediment recycling and adjustment of deposition during deglacial drowning of a low-accumulation shelf (NW Iberia)
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DOI：
10.1016/j.csr.2010.06.013
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发表时间：
2010-09-01
影响因子：
2.3
通讯作者：
Henrich, Ruediger
中科院分区：
文献类型：
--
作者：
Lantzsch, Hendrik;Hanebuth, Till J. J.;Henrich, Ruediger
基于已建立的地层格架和47个AMS-C-14定年沉积物岩心，分析了伊比利亚西北边缘的凋零类型分布，以响应末次冰期海平面上升，从而为高能低堆积陆架体系的沉积演化提供了一个案例研究。总共确定了四种主要的沉积相类型。(1)以砾石为主的沉积相以时间海侵冲刷床为主，在末次海平面低潮期外陆架浅水地区最初发育为滨面和风暴沉积；(2)广泛分布的硅质/生物源-碳质混合砂蚀带表明该地区具有中等水动力条件，对陆架物质的改造贡献较大，并有河流对陆架的补给；(3)陆架外固定位置的含海绿石砂相主要是在末次冰期海平面上升期间由较老沉积物的改造和自生矿物形成形成的；(4)泥相主要局限于全新世封闭型细粒沉积中心，位于中陆架位置。这些相类型在高能量、低堆积的NW伊比利亚陆架上的时空分布主要受沉积物供应、陆架形态和水动力系统强度的局部相互作用控制。这些模式与高堆积系统相反，在高堆积系统中，广泛的沉积物供应是相分布的主导因素。本研究强调了冰架消融过程中大规模侵蚀和物质循环对沉积堆积的重要性。滞后水平面上存在均匀且厚达15米的海侵覆盖层，这与通常认为在去冰期海平面上升期间高能量陆架系统上存在稀疏且侧向受限的沉积物堆积的假设相矛盾。与这种广泛的沙覆盖相反，在全新世海平面高水位期间，横向非常狭窄且最大的4米薄泥沉积形成。细粒沉积中心的限制形成与以下因素有关：(1)频繁发生的高能水动力条件；(2)邻近河流的陆源输入总体偏低；(3)加利西亚泥带距离其主要沉积物供应地较远。(C) 2010 Elsevier Ltd.版权所有。
Based on a well-established stratigraphic framework and 47 AMS-C-14 dated sediment cores, the distribution of fades types on the NW Iberian margin is analysed in response to the last deglacial sea-level rise, thus providing a case study on the sedimentary evolution of a high-energy, low-accumulation shelf system.Altogether, four main types of sedimentary facies are defined. (1) A gravel-dominated facies occurs mostly as time-transgressive ravinement beds, which initially developed as shoreface and storm deposits in shallow waters on the outer shelf during the last sea-level lowstand; (2) A widespread, time-transgressive mixed siliceous/biogenic-carbonaceous sand fades indicates areas of moderate hydrodynamic regimes, high contribution of reworked shelf material, and fluvial supply to the shelf: (3) A glaucony-containing sand facies in a stationary position on the outer shelf formed mostly during the last-glacial sea-level rise by reworking of older deposits as well as authigenic mineral formation; and (4) A mud facies is mostly restricted to confined Holocene fine-grained depocentres, which are located in mid-shelf position.The observed spatial and temporal distribution of these facies types on the high-energy, low-accumulation NW Iberian shelf was essentially controlled by the local interplay of sediment supply, shelf morphology, and strength of the hydrodynamic system. These patterns are in contrast to high-accumulation systems where extensive sediment supply is the dominant factor on the facies distribution.This study emphasises the importance of large-scale erosion and material recycling on the sedimentary buildup during the deglacial drowning of the shelf. The presence of a homogenous and up to 15-m thick transgressive cover above a lag horizon contradicts the common assumption of sparse and laterally confined sediment accumulation on high-energy shelf systems during deglacial sea-level rise. In contrast to this extensive sand cover, laterally very confined and maximal 4-m thin mud depocentres developed during the Holocene sea-level highstand. This restricted formation of fine-grained depocentres was related to the combination of: (1) frequently occurring high-energy hydrodynamic conditions; (2) low overall terrigenous input by the adjacent rivers; and (3) the large distance of the Galicia Mud Belt to its main sediment supplier. (C) 2010 Elsevier Ltd. All rights reserved.