Flow dynamics at the origin of thin clayey sand lacustrine turbidites: Examples from Lake Hazar,Turkey          下载免费PDF全文

Sophie Hage  Aurélia Hubert‐Ferrari  Laura Lamair  Ulaş Avşar  Meriam El Ouahabi  Maarten Van Daele  Frédéric Boulvain  Mohamed Ali Bahri  Alain Seret  Alain Plenevaux 《Sedimentology》2017,64(7):1929-1956

Turbidity currents and their deposits can be investigated using several methods, i.e. direct monitoring, physical and numerical modelling, sediment cores and outcrops. The present study focused on thin clayey sand turbidites found in Lake Hazar (Turkey) occurring in eleven clusters of closely spaced thin beds. Depositional processes and sources for three of those eleven clusters are studied at three coring sites. Bathymetrical data and seismic reflection profiles are used to understand the specific geomorphology of each site. X‐ray, thin sections and CT scan imagery combined with grain‐size, geochemical and mineralogical measurements on the cores allow characterization of the turbidites. Turbidites included in each cluster were produced by remobilization of surficial slope sediment, a process identified in very few studies worldwide. Three types of turbidites are distinguished and compared with deposits obtained in flume studies published in the literature. Type 1 is made of an ungraded clayey silt layer issued from a cohesive flow. Type 2 is composed of a partially graded clayey sand layer overlain by a mud cap, attributed to a transitional flow. Type 3 corresponds to a graded clayey sand layer overlain by a mud cap issued from a turbulence‐dominated flow. While the published experimental studies show that turbulence is damped by cohesion for low clay content, type 3 deposits of this study show evidence for a turbulence‐dominated mechanism despite their high clay content. This divergence may in part relate to input variables, such as water chemistry and clay mineralogy, that are not routinely considered in experimental studies. Furthermore, the large sedimentological variety observed in the turbidites from one coring site to another is related to the evolution of a sediment flow within a field‐scale basin made of a complex physiography that cannot be tackled by flume experiments.  相似文献   

The Pelona–Orocopia–Rand and related schists of southern California: a review of the best-known archive of shallow subduction on the planet     

Alan D. Chapman 《International Geology Review》2017,59(5-6):664-701

ABSTRACT

The Pelona–Orocopia–Rand and related schists of southern California are an archetypal example of an exhumed shallow subduction complex. ‘The schist’ comprises mainly trench materials underthust beneath continental arc rocks during Late Cretaceous–early Cenozoic collision of one or more oceanic plateaux with southern California. The arc-on-trench relationship, without intervening mantle or lowermost crust, implies that significant subduction erosion accompanied shallow subduction. Upsection increases in metamorphic grade (~150 ± 100°C/km) and spatial variations in age and peak temperature provide an ~50 million year long record of tectonic underplating within a cooling system. Evidence for palaeoseismic events in earliest formed and hottest (locally transitional granulite grade) schists provides a possible field-based record of episodic tremor and slow slip events such as detected in several modern shallow subduction zones. Structural ascent of the schist was achieved in distinct Late Cretaceous–early Eocene and late Oligocene–early Miocene extensional pulses, the first during collapse of gravitationally unstable upper plate assemblages and accompanied by trench-directed (top-NE) lower plate extrusion and the second corresponding temporally, spatially, and in character with core complex formation in the SW United States. The line between schist and core complex belts is blurred by the recent discovery of schist within 40 km of the nearest core complex and containing synkinematic Miocene intrusions, a hallmark of SW U.S. core complexes. The history of schist assembly, metamorphism, and exhumation provides the most complete field-based record of thermo-mechanical processes, subduction erosion and tectonic underplating in particular, that operated during a shallow subduction event. Future cross-disciplinary investigations of, and comparisons between, the schist and other possible ancient (e.g. Swakane gneiss, Sanbagawa belt, Qiangtang terrane) and modern (e.g. Cascadia, SW Japan, central Mexico, Chile) shallow subduction zones will yield new insights into the tectonic and petrologic processes that operate within such systems.  相似文献   

基于浅层探冰雷达的东南极内陆地区冰盖内部等时层提取   总被引：2，自引：1，他引：1  

潘曜  窦银科  郭井学  稂时楠  裴玉晶  丁云风 《冰川冻土》2017,39(2):252-258

中国第32次南极考察内陆队首次使用雪地车载浅层探冰雷达取得了中山站至昆仑站全程1 300 km 的浅层冰盖数据,通过MATLAB对数据进行FFT转换、背景滤波、改变叠加次数去噪和基于曲波变换的图像处理,使用Reflexw对MATLAB处理后数据进行地形校正、二次背景滤波和平滑滤波等处理,成功提取了冰盖浅层等时层并得出了等时层的平均深度、最大深度和波动情况。最后进行了数据的连接,展示了LGB69冰芯处等时层的分布并与冰芯数据结合大体对应了相应等时层的年代和事件。给出了Dome A附近的等时层分布情况。为东南极中山站至昆仑站沿途的物质积累率计算提供重要的数据支撑。  相似文献   

沙漠地区页岩气地质调查井施工技术          下载免费PDF全文

尹亮先  李得新  田小林  谢治国 《探矿工程》2017,44(3):17-20

武威盆地儿马湖凹陷地质调查井武地1井钻井工程位于内蒙古自治区腾格里沙漠腹地,施工条件恶劣。上部第四系覆盖层主要岩性为黄色砂土和红色细砂,厚度大,松散易垮塌。针对武地1井钻井难点,从井场建设、钻井设备的选择、井身结构、钻井液优化等方面采取措施,为沙漠地区钻井施工积累了经验。  相似文献   

巨厚砂砾层裸孔钻进施工技术          下载免费PDF全文

殷宝兵  黄留新  张瑞琼 《探矿工程》2017,44(9):26-31

在江苏沿海地区进行城市地质及水文地质等区域性地质调查,主要的野外工作手段就是全孔取心岩心钻探,但江苏沿海地区沉积层厚度300～500 m不等,最深处800 m之多。在如此之深的巨厚沉积层中钻探取心、且取心率要求之高在江苏乃至全国没有先例。结合某钻孔的施工实例,从钻探设备的选择、施工工艺的确定、泥浆控制技术等方面入手,全面总结了江苏沿海地区巨厚砂砾层全孔取心施工技术,对类似钻探项目的实施具有很好的借鉴作用。  相似文献   

廊坊市工程地质问题及防治措施          下载免费PDF全文

王德强  熊伟  关鉴 《探矿工程》2017,44(4):66-70

在工程地质、水文地质、构造地质条件评价的基础上,讨论了廊坊市工程软土、液化土层工程地质问题的分布特征,对地基持力层进行了初步选择。在此基础之上确定地基加固措施或桩基础方法处理工程地质问题。  相似文献   

福州江滨地区超高层建筑灌注桩成孔工艺分析          下载免费PDF全文

张志刚 《探矿工程》2017,44(6):84-87

以福州江滨地区2个有代表性的超高层建筑桩基础工程实例为依据,通过无卡式冲击 正循环,旋挖 气举反循环,回转 泵吸反循环3种成孔工艺之间的比对,提出了在福州市江滨地区超大粒径厚层卵石与花岗岩地层灌注桩施工成孔工艺方面的一些见解,认为回转 泵吸反循环是较为可靠的工艺。  相似文献   

基于非静压模型的波浪破碎模拟          下载免费PDF全文

张景新 《水科学进展》2017,28(3):438-444

波浪破碎是海岸工程所关注的关键水动力学问题之一,而波浪破碎的数值模拟技术的研究方兴未艾。高效的浅水方程基于静压假定,而通过引入动压项建立的完全非静压模型,可成功应用于色散水波的模拟。自由表面的捕捉采用的垂向坐标变换技术,较之VOF（Volume of Fluid）模型,计算效率较高。但垂向坐标变换不能模拟大曲率自由表面变形,即波浪破碎过程。对于破碎波的模拟,一种高效的模式分裂法应用至非静压模型,即在波浪破碎局部水域将模型分裂为静压模型和非静压模型,破碎波波峰附近退化至静压模型,并持续至波浪破碎结束再恢复为动压模型。通过典型算例,验证了模式分裂法的适用性及对于波浪破碎过程的模拟精度,鉴于模式分裂法对于波浪破碎过程的模拟未引入新的概化模型,计算效率较高,可应用于大尺度的海岸带波浪的变形、破碎及越浪的数值模拟。  相似文献   

生物滞留带结构层参数对道路径流滞蓄效应影响   总被引：1，自引：0，他引：1       下载免费PDF全文

高建平  潘俊奎  谢义昌 《水科学进展》2017,28(5):702-711

基于非饱和土壤水分运动理论,采用数值模拟方法研究了4种降雨作用下生物滞留带结构层参数对设施积水、产流及径流调控效应的影响特性。结果表明:生物滞留带表层积水受蓄水层深度影响显著,随蓄水层深度由20 cm增加到30 cm,设施的溢流控制水量平均提高0.196 m3左右,但积水时长增加可达85 min;生物滞留带各结构层参数对穿孔管产流均有一定影响,随种植土层与砂滤层厚度比或内部储水区高度增加,穿孔管产流时刻推迟,产流峰值减小,而蓄水层深度的增加则可导致穿孔管产流时刻提前、产流峰值增大;在4种降雨作用下,5类滞留带径流量平均消减率为16.71%~37.31%,径流峰值平均消减率为41.53%~63.90%,产流平均延迟时间为97.75~166.50 min;当滞留带发生溢流时,设施的径流调控能力显著降低,且结构层参数对设施径流调控效果的影响减弱。  相似文献   

浅层地震反射在郧西盆地断层探测中的应用与研究     

林松  罗登贵  李媛  周欣 《大地测量与地球动力学》2017,37(2):146-148

在前期详细地质调查的基础上,对郧西盆地进行针对性的浅层地震反射勘探,并利用地震发射结果来确定断层位置及构造特征。该研究对南水北调中线核心水源区地震安全系统的建设有一定意义。  相似文献