What is preserved in the aeolian rock record? A Jurassic Entrada Sandstone case study at the Utah–Arizona border

Aeolian dune fields evolve from protodunes and small dunes into a pattern of progressively fewer, larger and more widely spaced dunes within limits defined by boundary conditions. However, the allogenic boundary conditions that promote aeolian dune‐field development, accumulation of strata and preservation of accumulated strata are not the same. Autogenic processes, such as dune interactions, scour‐depth variation along migrating dunes and substrate cannibalization by growing dunes, result in removal of the stratigraphic record. Moreover, dune‐field events may be collapsed into major erosional bounding surfaces. The question is what stages of evolving dune fields are represented in the rock record? This case study of ca 60 m of Jurassic Entrada Sandstone on the Utah/Arizona border (USA) defines stratigraphic intervals by gross architecture of bounding surfaces and sets of cross‐strata. The interpreted intervals in stratigraphic order consist of: (i) a lower sabkha bed that transitions upward into erosional remnants of small sets representing an initial wet aeolian system; (ii) large, compound cross‐strata representing a mature dune field; (iii) isolated scour‐fill representing negatively climbing dunes that produced ca 25 m of palaeo‐topographic relief; (iv) downlapping sets that fill the landscape‐scale relief; (v) four intervals of stacked climbing sets that each represent short periods of time; and (vi) an upper sabkha bed that again transitions into small sets representing a wet system. Accumulations appear to be associated with sediment pulses, a rising water table, and filling of scoured troughs and landscape‐scale depressions. Preservation of the accumulations is selective and associated with a rising water table, burial and subsidence. The preserved record appears remarkably incomplete. Speculation about missing strata gravitates towards cannibalization of the record of early dune‐field construction, and strata removed during the formation of bounding surfaces. This local Entrada record is thought to represent a point in the spectrum of preservation styles in the rock record.     

Brittleness index predictions from Lower Barnett Shale well-log data applying an optimized data matching algorithm at various sampling densities

The capability of accurately predicting mineralogical brittleness index(BI)from basic suites of well logs is desir-able as it provides a useful indicator of the fracability of tight formations.Measuring mineralogical components in rocks is expensive and time consuming.However,the basic well log curves are not well correlated with BI so correlation-based,machine-learning methods are not able to derive highly accurate BI predictions using such data.A correlation-free,optimized data-matching algorithm is configured to predict BI on a supervised basis from well log and core data available from two published wells in the Lower Barnett Shale Formation(Texas).This transparent open box(TOB)algorithm matches data records by calculating the sum of squared errors be-tween their variables and selecting the best matches as those with the minimum squared errors.It then applies optimizers to adjust weights applied to individual variable errors to minimize the root mean square error(RMSE)between calculated and predicted(BI).The prediction accuracy achieved by TOB using just five well logs(Gr,pb,Ns,Rs,Dt)to predict BI is dependent on the density of data records sampled.At a sampling density of about one sample per 0.5 ft BI is predicted with RMSE～0.056 and R2～0.790.At a sampling density of about one sample per 0.1 ft BI is predicted with RMSE～0.008 and R2～0.995.Adding a stratigraphic height index as an additional(sixth)input variable method improves BI prediction accuracy to RMSE～0.003 and R2～0.999 for the two wells with only 1 record in 10,000 yielding a BI prediction error of＞±0.1.The model has the potential to be applied in an unsupervised basis to predict BI from basic well log data in surrounding wells lacking mineralogical measure-ments but with similar lithofacies and burial histories.The method could also be extended to predict elastic rock properties in and seismic attributes from wells and seismic data to improve the precision of brittleness index and fracability mapping spatially.     

Historical tsunami in the Makran Subduction Zone off the southern coasts of Iran and Pakistan and results of numerical modeling

Tsunami hazard in the Makran Subduction Zone (MSZ), off the southern coasts of Iran and Pakistan, was studied by numerical modeling of historical tsunami in this region. Although the MSZ triggered the second deadliest tsunami in the Indian Ocean, among those known, the tsunami hazard in this region has yet to be analyzed in detail. This paper reports the results of a risk analysis using five scenario events based on the historic records, and identifies a seismic gap area in western Makran off the southern coast of Iran. This is a possible site for a future large earthquake and tsunami. In addition, we performed numerical modeling to explain some ambiguities in the historical reports. Based on the modeling results, we conclude that either the extreme run-up of 12–15 m assigned for the 1945 Makran tsunami in the historical record was produced by a submarine landslide triggered by the parent earthquake, or that these reports are exaggerated. The other possibility could be the generation of the huge run-up heights by large displacements on splay faults. The results of run-up modeling reveal that a large earthquake and tsunami in the MSZ is capable of producing considerable run-up heights in the far field. Therefore, it is possible that the MSZ was the source of the tsunami encountered by a Portuguese fleet in Dabhul in 1524.     

我国绦虫一新记录属(钩吻属)及其一种记述

从730条海水鱼体内采得73种绦虫和其他寄生虫(线虫、吸虫等)。其中一种绦虫共有27条标本,经鉴定为假叶目Pseudophyllidea三枝钩科Triaenophoridae钩吻属Anchistrocephalus。本属为国内新记录,宿主马面鲀为本属新宿主。     

南海芋螺科一新记录种(软体动物门, 腹足纲, 新腹足目)

在对中国科学院南海海洋生物标本馆馆藏芋螺科 Conidae 标本, 以及近年来在南海补充采集的标本进行整理的过程中, 通过形态分类学方法鉴定发现隶属于芋螺属 Conus 的中国海新记录种1种: 锈色芋螺 Conus ferrugineus Hwass in Bruguière, 1792, 标本采自西沙群岛。文章描述了该种的外部形态, 查明了其生活习性和地理分布特点, 并与相似种犊纹芋螺 Conus vitulinus Hwass in Bruguière, 1792 进行了比较, 通过壳口内面前沟部位的颜色可将两者区分开: 锈色芋螺呈白色, 而犊纹芋螺呈紫 (褐) 色; 同时对这两个相似种的其他区别特征进行了总结。     

大亚湾西部海域沉积物中生物硅的含量及其分布特征

采用2. 0 mol/dm~3Na_2CO_3溶液5h单点化学提取-硅钼蓝连续分光光度分析法分别测定了大亚湾西部海域13个表层沉积物和1个沉积物岩芯中生物硅的含量.表层沉积物和沉积物岩芯中生物硅含量占比分别为0. 69%～2. 02%和1. 24%～2. 05%,平均值分别为1. 42%和1. 60%.结果证实西大亚湾沉积物中生物硅含量水平与我国南海近岸海域基本一致.在210Pbex测年的基础上,通过分析沉积物岩芯中生物硅、有机物、无机碳等多指标,揭示近百年来大亚湾周边环境变化对海洋环境的影响,证实了上世纪80年代以来西大亚湾周边农业、海水养殖业和工业发展等人类活动加剧了该海域生态环境变化,尤其90年代核电站运行对海洋生态变化造成一定的影响.     

南粤古驿道历史建筑数字化保护与VR场景构建

南粤古驿道遗留了众多文化遗产,具有较高的历史、艺术、科学价值,但历史建筑损坏较为严重.为推进南粤古驿道活化利用,本文采用精细三维建模技术与虚拟现实(VR)技术实现了南粤古驿道的数字化保护.首先对南粤古驿道遗址进行了分析,然后从数据采集、点云数据处理、几何模型加工、纹理贴图等方面阐述对历史遗迹进行精细三维建模和VR场景构...     

三维并行合成震源记录叠前深度偏移

提出了一种基于波动理论的三维合成震源记录叠前深度偏移方法,该方法不含任何物理假设,利用波动方程算子的3个性质,合成炮震源及炮震源记录,将面炮记录合成与相位编码合成两种方法在理论上和计算上合二为一,成为一个统一的合成理论. 通过双重叠加把三维叠前五维数据转换为三维数据,既保证了成像质量同炮记录偏移成像一样精确,又显著地提高了计算效率,且适于复杂地质构造成像. 针对不同情况,给出了几种不同的合成算子,使方法在实际应用中有较大的灵活性和选择性. 基于MPI并行算法的实现,进一步提高了计算效率. SEG＼EAGE盐丘C3_NA数据模型上的试算结果和新疆三维起伏地表实际地震资料的处理结果进一步说明了该方法的有效性和实用性.     

2003年10月25日民乐-山丹MS6.1、5.8地震加速度记录特征分析

2003年10月25日甘肃民乐-山丹发生Ms6．1、5．8地震。在时域和频域内对记录到的94条282道加速度记录进行了处理和分析,结果显示：（1）垂直向加速度峰值一般小于水平向;（2）震中距50km尤其是30km以内区域是主要地震灾区;（3）不同情况影响速度反应谱的主要因素不同,实际工作中应区别对待。     

渤海自由生活海洋线虫两个新纪录种

在对渤海滨州贝壳堤岛的自由生活海洋线虫进行分类和多样性研究中,发现2个我国新纪录种并进行了描述。其中,澳洲深咽线虫Bathylaimus australis Cobb,1894主要特征为:头刚毛长约20μm,分为4节,顶端膨大;前口腔大,无齿,后口腔小,具小齿;化感器双环形,位于口腔中部位置;交接刺细长,稍向腹面弯曲,近端膨大呈头状,长32-37μm;引带宽大,肾形,长36-40μm,末端角质化,渐尖。古氏努朵拉线虫Nudora gourbaultae Vincx,1989主要特征为:体表具12列纵向排列的V型装饰;第二体环较宽,头刚毛11-15μm(为头颈的67%-81%);化感器圆形,直径4-6μm(为相应体径的29%-38%),位于第二体环上;具双咽球;交接刺细长,弯曲呈S型,长为肛径的1.3-1.5倍;引带等于或长于交接刺,镰刀型,无肛前辅器。