The Cenomanian short snout enchodontid fishes (Aulopifomes,Enchodontidae) from Sierra Madre Formation,Chiapas, southeastern Mexico

In this paper the short snout Cenomanian enchodontids from the El Chango quarry, Chiapas, southeastern Mexico, are reviewed. Unicachichthys multidentata nov. gen. and sp. is named and identified as a new member of the Enchodontidae because it has the predorsal scute series that is the distinctive character of such family. This new genus resembles other short snout enchodontids, as Enchodus and Eurypholis; however, Unicachichthys differs from these and other members of the family because it shows characters ever observed, including a multitoothed dermopalatine, the presence of a basal sclerotic bone, and the serrations in the posterior edge of the preopercle vertical limb. The inclusion of Unicachichthys in two phylogenetic analyses, based on studies previously performed, suggests that this is a primitive representative of the family Enchodontidae. Additionally specimens of two different species of Enchodus from the El Chango quarry are also described; these specimens are so scarce and fragmentary that it is not possible to determine their specific taxonomic identity. The record of these Mexican fossils enrich the knowledge about the diversity of Cenomanian enchodontids in the North American domain of the Tethys Sea, which now contains new taxa that should be considered in future efforts to recognize the phylogenetic and biogeographic processes experienced by this fish group.     

First record of late Campanian ammonites from the Abderaz Formation of the Koppeh Dagh,northeastern Iran

An ammonite fauna from the upper Abderaz Formation of Kuh-e-Bul in the northwestern part of the Koppeh Dagh (Iran) is described and illustrated. The collection of 30 specimens is assigned to seven species, all of which are recorded from Iran for the first time: Pseudophyllites indra (Forbes, 1846), Pachydiscus (Pach.) haldemsis (Schlüter, 1867), Patagiosites stobaei (Nilsson, 1827), Menuites wittekindi (Schlüter, 1876), Glyptoxoceras retrorsum (Schlüter, 1872), Lewyites elegans (Moberg, 1885) and Trachyscaphites spiniger (Schlüter, 1872). This fauna is of a typical Boreal character, with all taxa having been described from northwest Europe originally. The stratigraphic range indicated by the ammonites is lower upper Campanian, below the first occurrence of Nostoceras (Bostrychoceras) polyplocum (Roemer, 1841) and probably above the last occurrence of Hoplitoplacenticeras (H.) vari (Schlüter, 1872). A nannofossil sample from the ammonite-bearing interval corresponds to the upper Campanian nannofossil zone UC15/CC22. Thus, on the basis of both ammonites and calcareous nannofossils, the upper Abderaz Formation is shown to be younger than assumed previously.     

塔中隆起中-上奥陶统之间的不整合成因机制

塔里木盆地众多岩溶储层不整合中, 中-上奥陶统之间的不整合研究意义重大.本文以塔中隆起中-上奥陶统之间的不整合结构特征为依据, 对不整合成因机制进行了分析.研究表明, 发生在恰尔巴克组沉积期间的地壳褶皱作用控制了不整合的发育, 其分布范围受背斜控制.在背斜区, 不同层系缺失的原因存在差异, 一间房组和鹰山组的缺失是剥蚀缺失, 而恰尔巴克组的缺失是沉积缺失.成因上可将其不整合划分为同构造型和后构造型两种不整合类型.同构造不整合分布在塔中背斜型隆起两翼的恰尔巴克组与一间房组之间, 后构造不整合分布在塔中背斜型隆起顶部的良里塔格组与鹰山组之间.     

安阳上第三系化学矿物指标显示物源区大地构造

南水北调（中线）安阳主干渠段施工过程中开挖出大量成熟度低且受近源构造影响较大的河湖相沉积岩。对现场采集的上第三系岩石样品开展了化学成分、 岩石骨架成分测试。利用Dickinson法和化学指标法, 研究得到安阳主干渠段西部物源区属于被动陆缘, 在上新世晚期向活动陆缘变化的认识。同期构造活动强烈的克什米尔N—J引水隧洞段的沉积岩, 属于岛弧和活动陆缘的大地构造背景。本文结果丰富了构造稳定和活跃区新近纪沉积构造背景认识, 可为喜马拉雅运动以来不同构造活动背景下的岩石组分和化学指标特征提供参考。     

Calibrating the middle and late Permian palynostratigraphy of Australia to the geologic time-scale via U–Pb zircon CA-IDTIMS dating

The advent of chemical abrasion-isotope dilution thermal ionisation mass spectrometry (CA-IDTIMS) has revolutionised U–Pb dating of zircon, and the enhanced precision of eruption ages determined on volcanic layers within basin successions permits an improved calibration of biostratigraphic schemes to the numerical time-scale. The Guadalupian and Lopingian (Permian) successions in the Sydney, Gunnedah, Bowen and Canning basins are mostly non-marine and include numerous airfall tuff units, many of which contain zircon. The eastern Australian palynostratigraphic scheme provides the basis for much of the local correlation, but the present calibration of this scheme against the numerical time-scale depends on a correlation to Western Australia, using rare ammonoids and conodonts in that succession to link to the standard global marine biostratigraphic scheme. High-precision U–Pb zircon dating of tuff layers via CA-IDTIMS allows this tenuous correlation to be circumvented—the resulting direct calibration of the palynostratigraphy to the numerical time-scale highlights significant inaccuracies in the previous indirect correlation. The new data show: the top of the Praecolpatites sinuosus Zone (APP3.2) lies in the early Roadian, not the middle Kungurian; the top of the Microbaculispora villosa Zone (APP3.3) lies in the middle Roadian, not the early Roadian; the top of the Dulhuntyispora granulata Zone (APP4.1) lies in the Wordian, not in the latest Roadian; the top of the Didecitriletes ericianus Zone (APP4.2) lies in the first half of the Wuchiapingian, not the latest Wordian; the Dulhuntyispora dulhuntyi Zone (APP4.3) is exceptionally short and lies within the Wuchiapingian, not the early Capitanian; and the top of the Dulhuntyispora parvithola Zone (APP5) lies at or near the Permo-Triassic boundary, not in the latest Wuchiapingian.     

鄂尔多斯盆地东部二叠系山西组页岩气成藏条件与有利区筛选

鄂尔多斯盆地东部榆106井区山西组页岩沉积在三角洲平原分流河道间沼泽、天然堤、决口扇远端与洼地环境。根据有机地球化学、物性、含气性、岩性实验分析,结合钻井、录井、测井资料与沉积相研究,开展了该区山西组页岩气成藏条件与有利区分布研究。山西组页岩有机碳含量较高,山二段平均5.28%,山一段平均3.02%,有机质类型以Ⅱ_2、Ⅲ型干酪根为主,有机质成熟度较高,R_o平均1.89%,生气条件优越。页岩孔隙度平均1.7%,渗透率平均0.0415×10~(-3)μm~2,平均含气量0.64 m~3/t,页岩单层厚度小,垂向上普遍与致密砂岩、煤层组成互层,累计厚度较大(平均达75 m),页岩渗透性较好而储集性能稍差。页岩脆性矿物含量平均49.9%,黏土矿物含量平均50.1%,黏土矿物含量较高,资源丰度普遍较低,但是页岩埋深小于3000 m,试气产能较高(0.64×10~4m~3/d),商业开发潜力较好。山二段有机质含量比山一段更高,含气性比山一段更好。主要基于页岩厚度与沉积相展布预测的山二段页岩气有利区呈北东向、南北向条带状展布,受分流河道间沼泽微相的控制。     

From river to shelf,anatomy of a high‐frequency depositional sequence: The Late Pleistocene to Holocene Tiber depositional sequence

The Late Pleistocene/Holocene Tiber delta succession represents the most recent and one of the best preserved, high‐frequency/low‐rank depositional sequences developed along the Latium continental margin of the Italian peninsula. Several previous studies have established a robust data set from which it has been possible to describe the stratigraphic architecture of the entire Tiber depositional sequence from the landward to seaward sectors and over a distance of 60 km. The Tiber depositional sequence shows many characteristics found in other Late Pleistocene to Holocene deltaic and coastal successions of the Mediterranean area. The stratigraphic architecture of the Tiber depositional sequence is controlled mainly by glacioeustasy, although factors such as tectonic uplift, volcanism and subsidence, exert an influence at a local scale. The resulting depositional model allowed discussion of some important points such as: (1) the genesis of the Tiber mixed bedrock‐alluvial valley, extending from the coastal plain to the innermost portion of the shelf, recording (i) multiple episodes of incision during relative sea‐level fall, and (ii) a downstream increase of depth and width of the valley during the base‐level fall and the subsequent base‐level rise; (2) the different physical expression of the Tiber depositional sequence boundary from landward to seaward, and its diachronous and composite character; (3) the maximum depth reached by the Tiber early lowstand delta at the end of the sea‐level fall is estimated at ca 90 m below the present sea‐level and not at 120 m as suggested by previous works; (4) the backward position of the Tiber late lowstand delta relative to the deposit of early lowstand; (5) the change of the channel pattern and of the stacking pattern of fluvial deposits within the Lowstand Systems Tract, Transgressive Systems Tract and Highstand Systems Tract. All of these features indicate that the Late Pleistocene/Holocene Tiber delta succession, even if deposited in a short period of time from a geological point of view, represents the result of the close interaction among many autogenic and allogenic factors. However, global eustatic variations and sediment supply under the control of climatic changes can be considered the main factors responsible for the stratigraphic architecture of this sedimentary succession, which has been heavily modified by human activity only in the last 3000 years.     

内蒙东部晚古生代构造格局:来自中、晚二叠-早三叠世砂岩碎屑锆石U-Pb年代学的证据

内蒙东部的克旗-林西-阿鲁科尔沁-扎鲁特-索伦-蘑菇气地区位于华北板块与西伯利亚板块所夹持的中亚造山带东段,西拉木伦缝合带与贺根山-黑河缝合带之间,是古亚洲洋晚古生代残余海盆最后消失的地区,保存了上述两缝合带构造演化过程的相关信息。本文针对中、晚二叠-早三叠世砂岩开展碎屑锆石LA-ICP-MS U-Pb年代学研究。测试的上二叠统林西组与下三叠统陶海营子组、老龙头组砂岩均具有成分成熟度低,近源快速沉积的特点,碎屑骨架成分显示多为火山岩区物源供给。锆石CL图和Th/U值也指示了绝大多数锆石为岩浆成因锆石。结合前人研究成果,区域内已获得的2533粒碎屑锆石U-Pb年龄主要分为3组:约230~570Ma(峰值年龄为270~315Ma、430Ma和500Ma)、700~1100Ma(峰值970Ma)及1500Ma(峰值1800Ma和2500Ma)。较古老的峰值年龄1800Ma和2500Ma,暗示了华北克拉通基底的物源信息。其余两组年龄则与西拉木伦缝合带北侧的额尔古纳-兴安-锡林浩特地块内部岩浆事件的时间相吻合。对比分析内蒙东部不同区域(克旗-林西地区、阿鲁科尔沁-扎鲁特地区和索伦-蘑菇气地区)、不同时代(中、晚二叠世-早三叠世)沉积物碎屑组分变化趋势,推测古亚洲洋最终沿西拉木伦缝合带自西向东呈"剪刀"式闭合,时间持续至早三叠世。此外,索伦-蘑菇气地区中、晚二叠-早三叠世相对稳定的物源供给,证实了额尔古纳-兴安地块与松辽-锡林浩特地块至少在中二叠世沉积以前就已经沿贺根山-黑河缝合带完成拼贴,应为前人提出的早石炭世末。     

中扬子二叠系碳酸盐岩定量岩相模式

以迭代因子分析、FPFS——模糊聚类、模糊识别为主体,构成了包括变量的选取、定量岩相模式的建立、岩相的定量识别等一套定量岩相分析的数学方法;用该方法对京山、崇阳两条实测剖面的岩相数据进行处理,得到了中扬子二叠系碳酸盐岩定量岩相模式,该模式也包括7个相带,与地质上的7个亚相一致。     

Spatial and vertical distributions of elements in sediments of the Colorado River delta and Upper Gulf of California

The abundance of major components (Fe, Ca, K, and organic carbon) and trace elements was analyzed in surface sediments and core samples from the Colorado River delta (CRD) and the Upper Gulf of California (UGC) using instrumental neutron activation analysis.The spatial distribution patterns of the elements studied are consistent with the model of sedimentary dynamics proposed for this area [Mar. Geol. 158 (1999) 125]: intense tidal resuspension of sediments in the delta with subsequent transport of suspended particulate matter in a southerly direction, followed by sedimentation of fine-grained material in a depocenter near the southwestern margin of the UGC. Concentrations of most of the elements are higher in the surface sediments of this depocenter. The gradual mixing of terrigenous and marine biogenic materials, normally expected for the estuarine sediments, was not detected in the CRD–UGC system because of homogenization of the sediments by tides and wind.Vertical profiles of element contents in samples of the sediment core collected in the depocenter area revealed (i) almost no anthropogenic contamination of the area by environmentally important trace elements such as Cr, Co, Sb, and As; (ii) a twofold decrease of Fe, Sc, Cr, and Co in upper core sediments; and (iii) the enrichment of the sediments at 60–62 cm depth in the core, in calcium carbonate, Ca, Sr, and the Eu_n/Sm_n shale-normalized ratio along with a depletion in this layer of Fe, Sc, Cr, Co, light rare-earth elements (REEs), and some other elements of terrigenous origin, presumably caused by the dilution of fluvial terrigenous material by biogenic carbonates, which were probably introduced at this level in the sediments by the action of a strong episodic winter storm, followed by the advective transport of shell fragments from the coastal clam banks or as a result of strong planktonic bloom.