Depositional Controls on the Ichnology of Ordovician Wave-dominated Marine Facies: New Evidence from the Shirgesht Formation, Central Iran

The Lower Ordovician Shirgesht Formation in central Iran is composed of siliciclastic and carbonate rocks deposited in diverse coastal and marine shelfal environments (tidal flat, lagoon, shoreface, offshore-shelf and carbonate ramp). Five facies associations contain diverse ichnofossil assemblages that show distinct proximal to distal trends formed in a wide range of physical-chemical conditions. The ethological groups of trace fossils in the Shirgesht Formation reflect a gradient of depositional stress conditions across a wave-influenced shoreline and shelf. Deposits of wave-influenced environments make up a significant component of the geological record of shallow marine settings, and the ability to determine paleoenvironments in detail in such successions is critical for reconstruction of depositional histories and sequence-stratigraphic interpretation.The Cruziana ichnofacies of the study shows highly diverse suites that record the establishment of a benthic community under stable conditions and a long-term colonization window. The Skolithos ichnofacies recognized is a low diversity opportunistic ichnocommunity suite that resulted from colonization after tempestite deposition in a stressed environment. The strata record an onshore to offshore replacement of the Cruziana ichnofacies (with abundant feeding traces of deposit-feeders) by the Skolithos ichnofacies (dominated by suspension-feeders and predators). A transitional zone between the two ichnofacies coincides with the offshore-transition/distal lower-surface deposits. The distribution of ichnofacies, the diversity and range of ethological characteristics reflected by the ichnogenera, and the wide range of wave-dominated coastal facies demonstrate the potential to use individual trace fossils and ichnofacies for significantly refined palaeoenvironmental analysis of wave-dominated coastal settings, particularly in Ordovician successions.     

中国南海天然气水合物第二次试采主要进展

泥质粉砂型天然气水合物被认为是储量最大开采难度亦最大的水合物储层,2017年南海天然气水合物试采,初步验证了此类水合物储层具备可开采性。在总结前次试采认识的基础上,对试采矿体进行优选、精细评价、数值与试验模拟和陆地试验,中国地质调查局于2019年10月—2020年4月在南海水深1225 m神狐海域进行了第二次天然气水合物试采。本次试采攻克了钻井井口稳定性、水平井定向钻进、储层增产改造与防砂、精准降压等一系列深水浅软地层水平井技术难题,实现连续产气30 d,总产气量86.14×104m3,日均产气2.87×104m3,是首次试采日产气量的5.57倍,大大提高了日产气量和产气总量。试采监测结果表明,整个试采过程海底、海水及大气甲烷含量无异常。本次成功试采进一步表明,泥质粉砂储层天然气水合物具备可安全高效开采的可行性。     

Latitudinal and climatic distributions of 3D craniofacial features among Holocene populations

The geographical and climatic patterning in craniofacial morphology among recent hominids has been regarded as relatively reliable evidence of environmental adaptation and natural selection,which is largely attributed to thermoregulation.However,the relative influence of genetic and environmental factors on craniofacial features is unclear.Our study employed 3D laser scanning techniques to evaluate the association between geographical(latitude),climatic(annual temperature)factors,and 3D craniofacial measurements in 18 recent populations through bivariate correlation analysis.Significant correlations were found among braincase surface area,zygomatic bone surface area,cranial-facial index(facial surface area relative to braincase surface area)and local temperature,and a clear latitudinal gradient was also found in variation of braincase surface area.No significant correlations were found between zygomatic bone surface area,cranial-facial index and latitude.Our analysis supports the idea that the braincase functions as a radiator and is closely related to direct sunlight.We also suggest that absolute/relative craniofacial surface area varies consistently with predictions derived from Bergmann’s Rule.The mosaic craniofacial traits of American Indians may reflect retention of cold-derived,ancestral features,as well as a response to a slightly warmer climate.Because different craniofacial regions preserve environmental/genetic signatures differentially,caution is suggested when craniofacial anatomy is used for phylogenetic reconstruction and functional-morphological analysis.     

塔城盆地1961-2009年气候变化特征分析

根据新疆塔城盆地4个气象站1961—2009年实测资料,统计分析了塔城盆地49 a气温、降水的变化特征,结果显示:近49 a塔城盆地年、季平均气温呈显著增暖的趋势,尤其以秋、冬两季的增暖更为显著,对年际增暖的贡献较大。气温偏暖年多发生在20世纪80年代以后,气温偏冷年多发生在20世纪60、70年代。塔城盆地年降水量亦呈上升趋势,年降水最多年多出现在气温相对偏暖的20世纪90年代,而降水最少年多出现在气温偏低的60年代。降水量的显著性检验显示,四季中除冬季外均通过了0.01的显著性水平检验,表明春、夏、秋三季对塔城盆地年降水量增多都有贡献。     

Partition of Forecast Error into Positional and Structural Components

Weather manifests in spatiotemporally coherent structures. Weather forecasts hence are affected by both positional and structural or amplitude errors. This has been long recognized by practicing forecasters(cf., e.g.,Tropical Cyclone track and intensity errors). Despite the emergence in recent decades of various objective methods for the diagnosis of positional forecast errors, most routine verification or statistical post-processing methods implicitly assume that forecasts have no positional error.The Forecast Error Decomposition(FED) method proposed in this study uses the Field Alignment technique which aligns a gridded forecast with its verifying analysis field. The total error is then partitioned into three orthogonal components:(a) large scale positional,(b) large scale structural, and(c) small scale error variance.The use of FED is demonstrated over a month-long MSLP data set. As expected, positional errors are often characterized by dipole patterns related to the displacement of features, while structural errors appear with single extrema, indicative of magnitude problems. The most important result of this study is that over the test period, more than 50% of the total mean sea level pressure forecast error variance is associated with large scale positional error. The importance of positional error in forecasts of other variables and over different time periods remain to be explored.     

Optimization for performance-based design under seismic demands,including social costs

Performance-based design in earthquake engineering is a structural optimization problem that has, as the objective, the determination of design parameters for the minimization of total costs, while at the same time satisfying minimum reliability levels for the specifi ed performance criteria. Total costs include those for construction and structural damage repairs, those associated with non-structural components and the social costs of economic losses, injuries and fatalities. This paper presents a general framework to approach this problem, using a numerical optimization strategy and incorporating the use of neural networks for the evaluation of dynamic responses and the reliability levels achieved for a given set of design parameters. The strategy is applied to an example of a three-story offi ce building. The results show the importance of considering the social costs, and the optimum failure probabilities when minimum reliability constraints are not taken into account.     

Reassessment of Prejanopterus curvirostris,a Basal Pterodactyloid Pterosaur from the Early Cretaceous of Spain

Prejanopterus curvirostra, from the Early Cretaceous of La Rioja province, was the first pterosaur genus and species described from Spain. The material comprises disarticulated cranial and postcranial remains from several individuals. The fossil-bearing bed is assigned to the lacustrine Leza Formation (eastern Cameros Basin, NW margin of the Iberian Range). This unit is regarded as either Berriasian-Valanginian or Barremian-Aptian. Prejanopterus curvirostris (specific name emended) was originally diagnosed on the basis of several characters of which the most significant was a lateral curvature of the rostrum. Re-examination of the holotype (rostrum) and paratype (partial rostrum with teeth) indicates that there is no genuine sideways bend of the preserved premaxilla-maxilla segments, but a slight dorsal curvature. Prejanopterus is characterized by a unique combination of characters: an emended diagnosis is provided. In contrast with previous estimates, the wing span of Prejanopterus was probably not much (if ever) in excess of 2 m. A phylogenetic analysis suggests that Prejanopterus is a basal pterodactyloid positioned between Pterodactylus and Cycnorhamphus-Gallodactylus. Prejanopterus represents the first evidence of Pterodactylidae in the Early Cretaceous of the Iberian Peninsula.