Dispersal of the Zhujiang River (Pearl River) derived sediment in the Holocene

High-resolution Chirp profiling and coring reveals an elongated(ca. 400 km) Holocene Zhujiang River(Pearl River)-derived mud area(maximum thickness 20 m) extending from the Zhujiang River Delta, southwestward off the Guangdong coast, to the Leizhou Peninsula. Two depo-centers, one proximal and one distal, are identified. On the continental shelf off the west Guangdong Province, the mud is deposited in water depth shallower than 50 m; while to the southeast of the Zhujiang River Estuary, the mud area can extend to the-120 m isobath. A combined analysis with the stratigraphic sequences of other muddy deposits in the Western Pacific marginal seas(mainly Changjiang(Yangtze) and Huanghe(Yellow) Rivers derived) indicates that the initiation of the Zhujiang River muddy deposit can be further divided into two stages: Stage 1 is before the mid-Holocene sea-level highstand(ca. 7.0 cal. ka BP), the proximal mud was mostly deposited after 9.0 cal. ka BP, when the sea-level rose slowly after the Meltwater Pulse-1C; Stage 2, after the mid-Holocene sealevel highstand, clinoform developed on the continental shelf off the west Guangdong Province, extending ca. 400 km from the Zhujiang River Estuary. The proximal clinoform thins offshore, from ca. 10 m thickness around 5–10 m water depth to less than 1–2 m around 20–30 m water depth. In addition, we also find a developed distal clinoform in the east of the Leizhou Peninsula.     

真空预压法在珠江流域某冲填土场地的应用

依托珠江流域某冲填土场地工程实例,介绍了真空预压法的施工参数及应用效果,另对“薄弱部位”泥浆搅拌桩密封墙处地层的强度进行了定量分析,结果表明真空预压法适用于此类场地,加固效果明显,但密封墙位置强度降幅较大,需采取换填等措施二次处理后才能使用,可为其他类似工程提供参考经验.     

Mud dispersal across a Cretaceous prodelta: Storm‐generated,wave‐enhanced sediment gravity flows inferred from mudstone microtexture and microfacies

Determining sediment transport direction in ancient mudrocks is difficult. In order to determine both process and direction of mud transport, a portion of a well‐mapped Cretaceous delta system was studied. Oriented samples from outcrop represent prodelta environments from ca 10 to 120 km offshore. Oriented thin sections of mudstone, cut in three planes, allowed bed microstructure and palaeoflow directions to be determined. Clay mineral platelets are packaged in equant, face‐face aggregates 2 to 5 μm in diameter that have a random orientation; these aggregates may have formed through flocculation in fluid mud. Cohesive mud was eroded by storms to make intraclastic aggregates 5 to 20 μm in diameter. Mudstone beds are millimetre‐scale, and four microfacies are recognized: Well‐sorted siltstone forms millimetre‐scale combined‐flow ripples overlying scoured surfaces; deposition was from turbulent combined flow. Silt‐streaked claystone comprises parallel, sub‐millimetre laminae of siliceous silt and clay aggregates sorted by shear in the boundary layer beneath a wave‐supported gravity flow of fluid mud. Silty claystone comprises fine siliceous silt grains floating in a matrix of clay and was deposited by vertical settling as fluid mud gelled under minimal current shear. Homogeneous clay‐rich mudstone has little silt and may represent late‐stage settling of fluid mud, or settling from wave‐dissipated fluid mud. It is difficult or impossible to correlate millimetre‐scale beds between thin sections from the same sample, spaced only ca 20 mm apart, due to lateral facies change and localized scour and fill. Combined‐flow ripples in siltstone show strong preferred migration directly down the regional prodelta slope, estimated at ca 1 : 1000. Ripple migration was effected by drag exerted by an overlying layer of downslope‐flowing, wave‐supported fluid mud. In the upper part of the studied section, centimetre‐scale interbeds of very fine to fine‐grained sandstone show wave ripple crests trending shore normal, whereas combined‐flow ripples migrated obliquely alongshore and offshore. Storm winds blowing from the north‐east drove shore‐oblique geostrophic sand transport whereas simultaneously, wave‐supported flows of fluid mud travelled downslope under the influence of gravity. Effective wave base for sand, estimated at ca 40 m, intersected the prodelta surface ca 80 km offshore whereas wave base for mud was at ca 70 m and lay ca 120 km offshore. Small‐scale bioturbation of mud beds co‐occurs with interbedded sandstone but stratigraphically lower, sand‐free mudstone has few or no signs of benthic fauna. It is likely that a combination of soupground substrate, frequent storm emplacement of fluid mud, low nutrient availability and possibly reduced bottom‐water oxygen content collectively inhibited benthic fauna in the distal prodelta.     

A Middle Miocene carbonate embankment on an active volcanic slope: Ilhéu de Baixo,Madeira Archipelago,Eastern Atlantic

Carbonate factories on insular oceanic islands in active volcanic settings are poorly explored. This case study illuminates marginal limestone deposits on a steep volcanic flank and their recurring interruption by deposits linked to volcaniclastic processes. Historically known as Ilhéu da Cal (Lime Island), Ilhéu de Baixo was separated from Porto Santo, in the Madeira Archipelago, during the course of the Quaternary. Here, extensive mines were tunnelled in the Miocene carbonate strata for the production of slaked lime. Approximately 10 000 m³ of calcarenite (−1 to 1ø) was removed by hand labour from the Blandy Brothers mine at the south end of the islet. Investigations of two stratigraphic sections at opposite ends of the mine reveal that the quarried material represents an incipient carbonate ramp developed from east to west and embanked against the flank of a volcanic island. A petrographic analysis of limestones from the mine shows that coralline red algae from crushed rhodoliths account for 51% of all identifiable bioclasts. This material was transported shoreward and deposited on the ramp between normal wave base and storm wave base at moderate depths. The mine's roof rocks are formed by Surtseyan deposits from a subsequent volcanic eruption. Volcaniclastic density flows also are a prevalent factor interrupting renewed carbonate deposition. These flows arrived downslope from the north and gradually steepened the debris apron westwards. Slope instability is further shown by a coral rudstone density flow that followed from growth of a coral reef dominated by Pocillopora madreporacea (Lamarck), partial reef collapse, and transport from a more easterly direction into a fore‐reef setting. The uppermost facies represents a soft bottom at moderate depths in a quiet, but shore‐proximal setting. Application of this study to a broader understanding of the relationship between carbonate and volcaniclastic deposition on oceanic islands emphasizes the susceptibility of carbonates to dilution and complete removal by density flows of various kinds, in contrast to the potential for preservation beneath less‐disruptive Surtseyan deposits. Copyright © 2013 John Wiley & Sons, Ltd.     

红层“哑地层”划分对比方法——以东营凹陷南坡始新统为例

针对红层划分对比所面临的难题,在充分吸收前人研究成果的基础上,将现有的多种分层方法相互整合,彼此约束和印证,形成了一套科学、便捷的技术方法,即"接触关系明顶底、岩电特征找界面、多元融合定方案、地震约束建格架"的综合地层划分对比技术。该方法针对红层的特殊性,根据岩电特征对干旱气候的响应变化,充分利用了测、录井资料纵向上的连续性优势(避免了取样分析的局限),以及地震资料横向上的优势,有效地解决了红层纵向划分、横向对比的难题,在济阳坳陷东营凹陷南坡始新统沙河街组、孔店组的应用取得了良好效果。该方法可为其它地区同类复杂地层划分对比提供技术支持。     

岩石物理化学性质对泰宁丹霞洞穴的形成制约

泰宁丹霞红层由铁钙质混合胶结的较松散固结红色砂砾岩构成,岩石胶结物中CaCO3含量较高,抗压强度极低、孔隙度和含水性均较高。当岩石遇水湿润或浸泡时,或者生物风化过程中受到各种动植物分泌的有机酸作用,岩石胶结物中CaCO3易溶解流失,促使丹霞红层进一步软弱松散。冬季水结冰之后体积会膨胀,所以岩层表面产生片状裂隙。通过裂隙的毛细管效应,孔隙-裂隙水由岩石内部向结冰的表面扩散,在表面张力作用下水呈表面积最小的球状。春季化冻时岩石沿球形片状裂隙自由剥落的片状风化,圆球形洞穴开始形成,随着四季交替,年复一年,间歇性结冰和融化过程,使得洞穴逐渐扩大,形成泰宁丹霞各种形态的洞穴奇观。     

干涸尾闾湖盆区泥漠地表磨蚀释尘特征

沙粒的表面磨蚀效应是地表产尘、释尘的重要机制,针对干湖盆泥漠地表开展磨蚀释尘实验研究,对理解干湖盆地表风蚀过程及盐碱尘暴形成机理具有重要意义。对采自西居延海干涸湖盆泥漠地表土样进行室内磨蚀模拟实验,研究了不同粒级（细、中、粗）沙粒不同落沙角度（30°,45°,60°）的磨蚀效应。结果表明：（1）泥漠地表磨蚀实验中能够产生明显释尘效应的沙粒粒级阈值为中沙（0.25 mm<M_d<0.50 mm）;（2）磨蚀粒径粒级相同时,磨蚀角度会对泥漠地表磨蚀释尘速率产生影响,磨蚀量的角度排序为60°>30°>45°,但同一粒级3种角度下的磨蚀释尘率差异不显著。（3）磨蚀角度为45°时,计算了泥漠地表的质量磨蚀率与能量磨蚀率,其中中沙为0.04 g·kg^-1、0.43 g·J^-1,粗沙为0.08 g·kg^-1、0.74 g·J^-1,极粗沙为0.26 g·kg^-1、2.54 g·J^-1;在磨蚀沙粒粒级倍增而磨蚀角度不变情况下,泥漠地表磨蚀释尘率与能量磨蚀率未发生正比例线性增长变化。     

最佳小波包基的矿区植被及红边位置提取

小波包变换能同时对植被光谱信息的低频和高频分量进行分解,并能克服小波变换时间分辨率高而频率分辨率低的缺陷从而具有能够探测植被细微变化的优势。实验利用Hyperion高光谱影像对云南省普朗铜矿区植被像元的光谱进行最佳小波包基参量获取与植被信息识别,并在此基础上提出一种提取重金属污染下植被红边位置的最佳小波包基系数应用模型。研究结果表明基于最佳小波包基参量的植被信息识别及基于最佳小波包基系数的重金属污染探测具有可行性与一定优越性。     

红团簇巨星的光谱分析及其作为I、K波段标准烛光的研究

基于高分辨率、高信噪比光谱观测资料，确定了19颗贫金属红团簇巨星的恒星大气参数，得到样本星4种α族元素(O、Mg、Ca、Si)的化学丰度．讨论了铁丰度与恒星大气参数的相关性以及α族元素丰度随金属丰度的变化，计算了共58颗红团簇巨星在I、K波段的绝对星等，讨论了它们与恒星铁丰度之间的关系．结果表明，在分析铁丰度范围内相对于I波段，K波段的绝对星等与铁丰度的相关性更弱，并且与利用理论模型得到的红团簇巨星I、K波段绝对星等与铁丰度的关系进行了比较与验证。     

上天梯膨润土在钻井泥浆中的应用研究

信阳上天梯矿区钙基膨润土可分为四个自然类型。根据矿石理化性能和蒙脱石晶体结构特征，选用第Ⅲ类矿石，运用对辊挤压钠化法和最佳工艺进行实验研究，获得钻井泥浆用Ａ．Ｐ．Ｉ级膨润土。