Climate forcing of fine-grained deep-marine systems in an active tectonic setting: Middle Eocene, Ainsa Basin, Spanish Pyrenees
Climate forcing of fine-grained deep-marine systems in an active tectonic setting: Middle Eocene, Ainsa Basin, Spanish Pyrenees
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DOI：
10.1016/j.palaeo.2014.06.005
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发表时间：
2014-09-15
影响因子：
3
通讯作者：
Pickering, Kevin T.
中科院分区：
文献类型：
--
作者：
Cantalejo, Blanca;Pickering, Kevin T.
一个多代理的方法来了解在深时间的环境变化进行了约150米的核心，从一个230米长的中始新世的核心从安萨盆地，西班牙比利牛斯山脉，代表深海硅质岩沉积物，使用详细的沉积测井，高分辨率多元素XRF地球化学，总有机碳，和稳定的碳同位素。作为工业-大学联合体的一部分，A6井的钻探穿过粉砂岩、细粒/极细粒砂岩浊积岩和半远洋无结构泥岩，这些沉积物是由一个桑迪海底扇和扇间沉积物形成的漫滩和离轴沉积物。为了比较砂岩浊积岩和粉砂岩之间的矿物学，扫描电子显微镜（SEM）和X射线衍射（XRD）进行选定的样品。砂岩浊积岩显示出富集的碎屑元素，如硅，锆和钛，这可能与更大的石英和重矿物含量相比，邻近的粉砂岩。无结构的半远洋泥岩主要由粘土矿物和碳酸盐组成。我们解释砂岩浊积岩从hyperpycnal流在高河流泥沙排放，而半远洋泥岩的悬浮液脱落hypopycnal流。岩芯的旋回地层分析揭示了米兰科维奇旋回的频率类似于0.03周期/米（短偏心率），类似于0.09周期/米（旋度），类似于0.15周期/米（岁差偶）和类似于0.19周期/米（岁差偶）。轨道参数似乎控制了浊流循环输送粗颗粒沉积物。两种同样合理的沉积模式，都是Milankovitch驱动的，可以解释深海沉积物的周期性变化：（1）气候周期，潮湿时期的化学风化增强，风暴增加和河流径流增加，导致高沉积物通量的深盆砂岩浊积岩;（2）气候循环，较冷的条件与高频小尺度海平面升降波动有关，低水位陆架边缘三角洲沉积，导致大量的粗碎屑沉积物通过高密度流流向海底。这项研究提供了一个深入了解轨道引起的气候变化对陆源沉积物的性质和交付到深海环境可能的沉积影响。(C)2014爱思唯尔有限公司版权所有。
A multi-proxy approach to understand environmental change in deep time was undertaken on about 150 m of core from a 230 m-long Middle Eocene core from the Ainsa basin, Spanish Pyrenees, representing deep-marine siliciclastic sediments, using detailed sedimentary logging, high-resolution multi-element XRF geochemistry, total organic carbon, and stable carbon isotopes. The Well A6 was drilled, as part of an industry-university consortium, through siltstones, fine-/very fine-grained sandstone turbidites, and hemipelagic structureless mudstones, that were deposited as overbank and off-axis deposits from a sandy submarine fan, and interfan deposits. For comparative mineralogy between the sandstone turbidites and siltstones, scanning electron microscopy (SEM) and X-ray diffraction (XRD) were undertaken on selected samples. The sandstone turbidites show enrichment of detrital elements such as Si, Zr and Ti, that can be linked to greater quartz and heavy-mineral content compared with adjacent siltstones. Structureless hemipelagic mudstones comprise mainly clay minerals and carbonate. We interpret the sandstone turbidites as from hyperpycnal flows during high river sediment discharge, whilst hemipelagic mudstones resulted from the suspension fall-out of hypopycnal flows. Cyclostratigraphic analysis of the core reveals Milankovitch cyclicity at frequencies of similar to 0.03 cycles/m (short eccentricity), similar to 0.09 cycles/m (obliquity), similar to 0.15 cydes/m (precession couplet) and similar to 0.19 cycles/m (precession couplet). Orbital parameters appear to have controlled the cyclic delivery of coarser-grained sediment by turbidity currents. Two equally plausible depositional models, both as Milankovitch-driven, can explain the cyclical changes in the deep-marine sediments: (1) climatic cycles, with humid periods of enhanced chemical weathering, increased storminess and greater riverine run-off, leading to high sediment flux to the deep basin as sandstone turbidites; (2) climatic cycles, with cooler conditions linked to high-frequency small-scale eustatic sea-level fluctuations, with lowstand shelf-edge delta progradation, resulting in greater volumes of coarse detrital sediment to the seafloor by hyperpycnal flows. This study provides an insight into the likely depositional effects of orbitally-induced climate change on the nature and delivery of terrigenous sediment into deep-marine environments. (C) 2014 Elsevier B.V. All rights reserved.