Hydrocarbon source rock potential in the southwestern Gulf of Suez graben: Insights from organic geochemistry and palynofacies studies on well samples from the Ras El Bahar Oilfield

Palynological and biomarker characteristics of organic facies recovered from Cretaceous–Miocene well samples in the Ras El Bahar Oilfield, southwest Gulf of Suez, and their correlation with lithologies, environments of deposition and thermal maturity have provided a sound basis for determining their source potential for hydrocarbons. In addition to palynofacies analysis, TOC/Rock-Eval pyrolysis, kerogen concentrates, bitumen extraction, carbon isotopes and saturated and aromatic biomarkers enable qualitative and quantitative assessments of sedimentary organic matter to be made. The results obtained from Rock-Eval pyrolysis and molecular biomarker data indicate that most of the samples come from horizons that have fair to good hydrocarbon generation potential in the study area. The Upper Cretaceous–Paleocene-Lower Eocene samples contain mostly Type-II to Type-III organic matter with the capability of generating oil and gas. The sediments concerned accumulated in dysoxic–anoxic marine environments. By contrast, the Miocene rocks yielded mainly Type-III and Type-II/III organic matter with mainly gas-generating potential. These rocks reflect deposition in a marine environment into which there was significant terrigenous input. Three palynofacies types have been recognized. The first (A) consists of Type-III gas-prone kerogen and is typical of the Early–Middle Miocene Belayim, Kareem and upper Rudeis formations. The second (B) has mixed oil and gas features and characterizes the remainder of the Rudeis Formation. The third association (C) is dominated by amorphous organic matter, classified as borderline Type-II oil-prone kerogen, and is typical of the Matulla (Turonian–Santonian) and Wata (Turonian) formations. Rock-Eval T_max, PI, hopane and sterane biomarkers consistently indicate an immature to early mature stage of thermal maturity for the whole of the studied succession.     

Population connectivity of an overexploited coastal fish,Argyrosomus coronus (Sciaenidae), in an ocean-warming hotspot

The West Coast dusky kob Argyrosomus coronus is a commercially exploited fish with a distribution confined to the Angola–Benguela Frontal Zone (ABFZ) of the southeastern Atlantic Ocean. A previous study revealed that during a recent period of local warming the species extended its distribution into Namibian waters, where it hybridised with the resident and congeneric Argyrosomus inodorus. Environmental changes are a major threat to marine biodiversity and when combined with overfishing have the potential to accelerate the decline of species. However, little is known regarding the evolutionary history and population structure of A. coronus across the ABFZ. We investigated genetic diversity, population structure and historical demographic changes using mtDNA control region sequences and genotypes at six nuclear microsatellite loci, from 180 individuals. A single, genetically homogeneous population was indicated across the distributional range of A. coronus (φ_ST = 0.041, F_ST = 0.000, D = 0.000; p > 0.05). These findings imply that the oceanographic features within the ABFZ do not appear to significantly influence population connectivity in A. coronus, which simplifies management of the species. However, reconstruction of the demographic history points to a close link between the evolutionary history of A. coronus and the environmental characteristics of the ABFZ. This outcome suggests the species’ vulnerability to the rapid environmental changes being observed across this region, and highlights a pressing need for transboundary management to mitigate the impacts of climate change in this global hotspot of seawater temperature changes.     

Microbial activity promotes the enrichment of cobalt over nickel on hydrogenetic ferromanganese crusts

The different mineral phases of the ferromanganese (Fe–Mn) crusts stem from the interaction of biotic and abiotic components. It is therefore vital to study the activity of these components to decipher their contribution to the enrichment/depletion of metals in the crust. Thus, the present study examined sorption and release of Co and Ni by Fe-Mn crusts with associated microbial communities in the presence and absence of the metabolic poison sodium azide (15?mM). The study was conducted in the presence (G⁺) and absence (G^?) of added glucose (0.1%) at temperatures of 4?±?1°C and 28?±?2°C. Results showed that the microbial community had maximal sorption of Co of 66.12?µg?g^?1 at 4?±?1°C in the absence of added glucose and 479.75?µg?g^?1 at 28?±?2°C in the presence of added glucose. Maximum sorption of Ni in the absence of added glucose was 1.89?µg?g^?1 at 4?±?1°C and release of Ni was 51.28?µg?g^?1 in the presence of added glucose. Under abiotic conditions with 15?mM sodium azide as a metabolic inhibitor, significant amounts of Co and Ni were released in the G⁺ medium. Total cell counts on the Fe-Mn crust in the presence of added glucose increased by an order of magnitude from 10⁶ to 10⁷ cells g^?1 and in the absence of added glucose remained within the order of 10⁶ cells?g^?1 irrespective of temperature of incubation. Microscopic observation of the samples from biotic incubations showed numerous bacterial cells, exopolysaccharides, and structures resembling secondary minerals formed by bacteria. The results indicate that bacteria promote the enrichment of Co and Ni on the hydrogenetic Fe-Mn crusts by sorption processes and release of Ni by reductive dissolution of the oxides. The higher enrichment of Co than Ni is attributed to the way in which microbes interact with the metals.     

有孔虫初房特征变化在珠江三角洲晚全新世东亚夏季风降雨研究中的应用

研究中国降雨格局变化对理解东亚夏季风演化意义重大。本文分析了珠江三角洲柱状样ZJK03-Z中浅水底栖有孔虫常见种Rotalidium annectens的平均初房大小、微球型/显球型比值和壳体δ18O值,以及底栖有孔虫组合中瓷质壳的百分含量,探讨它们对由夏季风降雨引起的河口水体盐度变化的响应,得到了珠江三角洲3114—1260a BP季风降雨的强度变化,识别出了这期间14次季风降雨减少的偏干期。与南美洲Cariaco海盆的钛含量记录对比,二者一致的结果表明,珠江三角洲晚全新世的东亚夏季风降雨与热带辐合带(ITCZ)的南北移动密切相关:夏季风降雨减少,对应于ITCZ纬度位置的南移。     

Whether human-induced activities could change the gradient pattern of coastal land use along the sea-land direction: a case study in Manila Bay,Philippines

Increasing intense human activities have largely changed the coastal landscape and caused many environmental issues. However, whether human-induced activities could change the coastal land use gradient pattern, an important coastal zonal characteristic along the sea–land direction, remains unclear. Manila Bay was selected as the study area in this work. According to the distance of the land use and land cover(LULC) to the coastline, we clustered the typical coastal land use sequence patterns(CLU...     

New interpretation on the provenance changes of the upper Pinghu–lower Huagang Formation within Xihu Depression,East China Sea Shelf Basin

Both Pinghu and Huagang formations are important hydrocarbon reservoirs of the Xihu Depression in the East China Sea Shelf Basin. Clarifying the source suppliers and restoring source-to-sink transport routes are of great significance to the future petroleum and gas undertakings. Previous researchers were largely confined by either limitation of geological records, highly dependence on a singular method or low-precision dating techniques. Our study integrated heavy mineral assemblages, geochemica...     

Coastal ridge constructive processes at a multi-decadal scale in Barreta Island (southern Portugal)

Multiple ridges across prograding coasts may display variable geometries, commonly expressed through varying elevations. Changes in ridge elevation have been traditionally related to the occurrence of fluctuating progradation rates, which might, in turn, be driven by shifting environmental conditions. Here, we explore the geometry and growth mechanisms of multiple ridges, generated at Barreta Island (Ria Formosa, southern Portugal), as a consequence of the rapid progradation of the island over the last 70 years, following the artificial fixation of the downdrift Faro-Olhão inlet with jetties in 1955. The variability in the morphology of these features was analysed in combination with available wind and wave data, in order to better distinguish growth mechanisms and understand the main parameters determining the final geometry of the observed ridges. The results suggest that (1) most of the identified ridges fall in the beach ridge classification, as they have been mostly built by marine processes, and (2) the parameters derived from, or closely related to wave climate variability (e.g. progradation rates, storm occurrence) can jointly explain most of the observed morphological changes, while aeolian processes played a secondary role. Indeed, ridge geometry appears mainly controlled by progradation rates, with higher ridges associated with lower progradation rates. Progradation rate, in turn, is mostly related to longshore wave power, storminess, and the occurrence storm groups. Yet, the final configuration of ridges can also be affected by runup levels and onshore winds. Therefore, establishing the relation between ridge geometry and wave climate is not a straightforward task, because of the complex processes and interactions that control coastal morphodynamics. © 2019 John Wiley & Sons, Ltd.     

双向耦合循环剪切条件下超固结饱和海洋黏土孔压与强度特性研究

针对长江口地区的重塑饱和海洋黏土,进行了一系列均等固结条件下的应力控制式轴向-扭转双向耦合循环剪切试验,着重探讨了循环荷载分量比R与超固结比OCR对孔压与动强度特性的影响。试验结果表明,随着R的减小,波动孔压幅值逐渐降低,而残余孔压先降低后升高,R = 1时残余孔压最小。在循环耦合剪切作用过程中,对应相同循环次数,随着OCR的增大,累积孔压变小,而波动孔压幅值却在增大。对应相同循环次数比N/Nf,随着OCR增大,残余孔隙水压力比ur / urmax减小。经归一化处理后ur / urmax-N/Nf关系曲线对于正常固结与超固结饱和黏土可分别用不同的表达式来表达。随着R的降低,破坏循环次数先增大后减小,R = 1时最大。随着OCR的增大,饱和黏土的强度变化减小     

边界层风廓线雷达在降水时段中的在线分析应用研究

本研究提出了一种在边界层风廓线雷达连续运行的降水探测时段中对降水频谱进行在线分析的新的应用方式。详细介绍了边界层风廓线雷达在线分析原理和方法。同时结合典型降水频谱个例,分析了可获得的多个潜在的气象参数和信息。并指出,该在线分析方式的实施可以使风廓线雷达的应用领域从晴空探测向降水测量拓展;有效缓解当前风廓线雷达应用存在的瓶颈问题;间接证明边界层风廓线雷达组网间距不固定的观点。文章分析说明,随着在线分析方式的推广应用,边界层风廓线雷达将成为单站精细化气象探测和预报/服务的重要工具。     

基于区域自动站数据的兰州地区降水精细化特征

基于2012—2019年兰州地区146个区域自动气象站小时降水数据,从不同时间尺度分析兰州地区近8 a降水精细化特征。结论如下:(1)2012—2019年,兰州地区年均降水量总体呈"北少南多、外多内少"的空间分布特征;年降水量具有明显的年际变化,2018年降水异常偏多46%,而2015、2017年降水异常偏少,尤其2015年偏少30%。(2)兰州地区降水主要集中在7—8月,受环流形势影响,7—8月南部降水明显多于北部,其余月份南北降水差异不明显。(3)兰州地区降水量和降水范围分别表现为"朝少夕多"、"夜大日小"的日变化特征;受海拔高度影响,城区降水量总体比山区小,且因热岛效应,城区降水主要集中在午后至傍晚前后,多为对流性降水,而山区降水日分布较为均匀,整体日波动较小。(4)安宁区短时强降水发生频次最高,但短时强降水频发的站点出现在皋兰县六合站和永登县徐家磨村站,永登县是兰州地区短时强降水预报需重点关注的地区。