燕山地区土城子组划分、时代与盆地性质探讨

燕山地区土城子组分布广泛,顶底清晰,是本区最具特色的岩石地层单位之一。区域地质对比研究表明,燕山西部土城子组与燕山中东部土城子组在地层、时代上有较大的不同,西部盆地中髫髻山组火山岩不发育或很少发育,土城子组在地层划分上常包含九龙山组或髫髻山期火山岩,时代为中晚侏罗世(J2—J3);东部盆地普遍发育髫髻山组火山岩浆或火山-沉积地层,土城子组划分与层型剖面一致。古生物化石和同位素年龄研究表明:土城子组时限在156~139Ma之间,属于晚侏罗世—早白垩世。土城子期盆地沉积的不对称性,相分布特征,古水流等指示其形成在一个挤压作用下的陆内火山-沉积盆地环境。     

Post-Last Glacial Maximum evolution of a “fjord-type” lake based on high-resolution seismic data: the Lago Roca/Acigami (southern Tierra del Fuego,Argentina/Chile)

Lago Roca/Acigami is a “fjord-type” lake located in the southernmost part of South America, in the proximity of the Beagle Channel. A high-resolution seismic survey was carried out to analyse the seismic stratigraphy of the lake and to shed some light on the post-Last Glacial Maximum history of the area. Six seismic units were recognised, and their nature and depositional context were interpreted using seismic stratigraphy and acoustic facies analysis. A buried large ridge was identified within the glacial unit (SU1), interpreted as a frontal moraine that indicates a stabilisation phase. After retreat of the glacier from the basin, the trough was flooded by meltwater and a lake developed (SU2). The seismic facies, from bottom to top, depict a transition from ice-contact (SU2; SU3) to ice-distal proglacial conditions (SU4). A thick draping unit (SU5) marks a marine transgressive event and the instauration of a fjord environment in the basin. The marine transgression was a rapid event preceded by a fall in the lake level that caused an erosional unconformity. During the fjord phase the sedimentation remained controlled by meltwater discharge. Sea level fall, and subsequent disconnection from the Beagle Channel was accompanied by a progradation of the glaciofluvial deltaic sediments and the occurrence of several mass-wasting deposits (SU6). © 2019 John Wiley & Sons, Ltd.     

Cretaceous amber inclusions of Spain and Myanmar demonstrate early diversification and wide dispersal of Cephenniitae (Coleoptera: Staphylinidae: Scydmaeninae)

The taxonomic status of previously misplaced species of an ant-like stone beetle from Spanish amber (Albian) is clarified. Specimens of Kachinus magnificus (originally placed as incertae sedis within Scydmaenitae) were re-examined and their characters were found different from those of the type species of Kachinus from Myanmar amber. Consequently, Archeutheia gen. nov. is proposed to accommodate the Spanish species, resulting in Archeutheia magnifica comb. nov. Moreover, in a comprehensive phylogenetic analysis Archeutheia was placed as a sister group to extant Eutheia, within the tribe Eutheiini of Cephenniitae. A specimen of an undetermined genus from Myanmar amber clearly belonging in Cephenniini is also recorded. Both taxa represent the first definite Cretaceous Cephenniitae, a supertribe whose recent members are distributed on all continents but are especially diverse in the Oriental and East Palaearctic regions. This finding demonstrates a diversification of two presently most species-rich tribes of Cephenniitae already in Early Cretaceous. Archeutheia is strikingly similar to the extant species of Eutheia and Veraphis, showing male dimorphic characters (modified protrochanters) and antennal cavities characteristic of Palaearctic Eutheiini. This fact suggests a long morphological stability in the supertribe. A previously proposed hypothesis of an early presence of the Cephenniitae in the Northern Hemisphere is for the first time supported by the fossil record, and the palaeolocalities (western Europe and Southeast Asia) demonstrate a wide distribution of Cephenniitae in the Cretaceous and an early split of its ancestral lineage.     

滇黔北坳陷及邻区下志留统龙马溪组页岩气储层特征

基于8口钻井、2个剖面点的岩样观察和测试分析,滇黔北坳陷及邻区下志留统龙马溪组下段是富有机质泥页岩发育的层段,有机质演化达到过成熟阶段。X衍射全岩分析表明,龙马溪组泥页岩由黏土矿物、石英、碳酸盐、长石、黄铁矿等矿物组成,黏土矿物则以伊利石为主。泥页岩的平均脆性指数56.11%~73.21%,压裂时易于形成网络裂缝;常规物性测试,孔隙度、渗透率很低,扫描电镜观察,纳米级孔隙和裂缝发育。     

Water table variations in Atacama Desert alluvial fans: discussion of “Evidence of short-term groundwater recharge signal propagation from the Andes to the central Atacama Desert: a singular spectrum analysis approach”*

ABSTRACT

Using a statistical approach, Scheihing attempts to demonstrate the direct influence of recharge events in the Precordillera and the Andean Piedmont on water table variations in downstream alluvial fans. The author “unquestionably” discards the existence of ephemeral recharge processes in alluvial fans although they are frequently impacted by major floods. However, the author does not consider previous publications about recharge processes in arid alluvial fans, the hydraulic setting of the Pampa del Tamarugal Aquifer (PTA) and anthropogenic pressure changes in the PTA. Because the sustainable management of groundwater resources in drylands depends on a good understanding of hydrogeological processes, we propose a thorough reinterpretation of the short- and long-term PTA water table variations addressed by the author. In this comment, we illustrate the limits of the sole use of a statistical approach for characterizing both recharge processes and factors controlling the water table variations in the Atacama Desert.     

试论海相碳酸盐岩储层发育的影响因素：以任丘油田雾迷山组为例

依据任丘潜山碳酸盐岩储层研究成果及潜山油藏有关储层资料,分析了海相碳酸盐岩储层发育的影响因素。储层中泥质白云岩与粗结构藻白去岩的韵律性的岩性剖面,纵向上储层与非储层交替出现,孔洞的发育顺层分布,形成同层渗透带;多次沉积间断,构成多岩溶期,并有沿风化壳的溶蚀缝洞带及古水平岩溶带;构造应力产生断层和构造缝发育带,可形成断裂高渗带;成岩后生作用及储层演化,经历了各种次生改造,形成现今的储层面貌。认为层位     

Morphodynamic interactions of continental shelf,beach and dunes: the Cabopino dune system in southern Mediterranean Spain

The complex morphodynamic interactions between nearshore, shoreface and dune systems are usually simplified by studying these zones and their associated processes in isolation. However, the established relationships between each of them suggests that an integrated approach is required to examine the genesis, evolution and adaptation of the entire morphodynamic system. The Cabopino dune system in the southern Spanish Mediterranean Sea provides a clear example of a linked morphodynamic system in which a relatively large dune system has been generated and grown through the supply of sediments from an adjacent littoral supply environment. Here, we present a conceptual model of how the nearshore has provided suitable conditions for beach and dune development. We purport that synchronization of sediment activation in the marine and aeolian sections of the system have played a major role in this microtidal setting in which temporal aspects are not only tied to storm action, but to large sedimentary features moving alongshore. © 2019 John Wiley & Sons, Ltd.     

Statistical evaluation of fluoride contamination in groundwater resources of Santiago del Estero Province,Argentina

This study investigates the suitability of statistical techniques for evaluating the fluoride content and the groundwater quality from Robles Department (RD) and Banda Department (BD) in Santiago del Estero (Argentina). For the original statistical study, evaluation of nine parameters (fluoride, pH, conductivity, atmospheric and water temperature, total dissolved solids, chloride, hardness, and alkalinity) of 110 collected underground water samples from 23 dispersed rural areas was proposed. Groundwater samples were obtained by sampling taken from wells at different depths. Fluoride levels were determined by a standard colorimetric method in two seasonal periods, the dry (from April to September) and rainy (from October to March) period. The analytical results obtained for physicochemical parameters such as pH, total dissolved solids (TDS), and temperature does not reveal any notable difference between the rainy and dry seasons studied. In both seasons, the atmospheric temperature average was 22 ​°C. With respect to fluoride content, approximately 50% of the analysed groundwater samples exceeded the limit established by current legislation (1.0 ​mg/L), obtaining concentration levels in the range of 0.01–2.80 ​mg/L. This study demonstrates the usefulness of the univariate statistical method (quartiles calculation, interquartile range IQR), multivariate principal component analysis (PCA), and cluster analysis to establish a better understanding of the state of the contamination of the waters in the region studied.     

IMPACT OF NEOTECTONICS ON THE RECORD OF GLACIER AND SEA LEVEL FLUCTUATIONS, STRAIT OF MAGELLAN, SOUTHERN CHILE

ABSTRACT. This paper presents evidence for a neotectonic influence on Late Pleistocene/Holocene records of environmental change in the southern Strait of Magellan. We concentrate on one site, Puerto del Hambre, a key location for reconstructing palaeoenvironmental change in southernmost South America. We report geomorphological, structural geological, seismic and topographic data that all show the site has been affected by postglacial faulting. There is also indirect evidence from the site stratigraphy that the site has been displaced. Also, recent faulting explains some of the puzzles associated with interpretation of the palaeoenvironmental record at Puerto del Hambre. The implication of this work is that neotectonic faulting had a pervasive influence in the southern part of the Strait of Magellan and southernmost Tierra del Fuego, and thus affects glacial or sea level reconstructions in the area.     

黔西北下寒武统牛蹄塘组页岩气成藏条件与有利勘探区预测

以野外露头调查、老井复查和岩心样品测试等为基础,通过现场解吸实验和等温吸附模拟的含气性分析,认为黔西北下寒武统牛蹄塘组岩性主要为深水陆棚黑色碳质页岩和浅水陆棚粉砂质页岩,其中富有机质页岩段为牛蹄塘组底部的碳质页岩。页岩沉积厚度大(大于39m)、分布稳定。有机质类型主要为Ⅰ型干酪根,有机碳含量较高(富有机质页岩段平均大于5%),有机质热演化程度处于高—过成熟阶段;页岩储层中微裂缝、微孔隙发育,具较好的孔隙度(平均5.14%)和渗透率(0.011 4×10-3μm2),含气量大(平均1.3 m3/t),具有良好的气资源潜力。预测金沙—息烽以及仁怀两个地区为页岩气勘探有利区。