重庆秀山下志留统龙马溪组的双菌迹及其地质意义

重庆秀山地区下志留统龙马溪组上部的灰色页岩中产出有肉红色粉砂岩填充的U形浅潜穴双菌迹(Bifungites),其丰度较高,但属种十分单调,淡化潮坪相的沉积表明秀山地区早志留世龙马溪期晚期为淡化潮坪相的沉积.     

Regional Δ<Superscript>14</Superscript>C patterns and fossil fuel derived CO<Subscript>2</Subscript> distribution in the Beijing area using annual plants

The level of atmosphericΔ14C and the fossil fuel derived CO 2 concentration in the Beijing area from May to September,2009, were systematically analyzed based on radiocarbon(14C)measurements of annual plants by accelerator mass spectrometry(AMS). The results show that the maximumΔ14C in Beijing was 29.6‰±2.2‰,and the minimum was–28.2‰±2.5‰,with a trend of decreasingΔ14C from the outer suburbs to inner suburbs to the urban center.This trend correlates well with increases in fossil fuel derived CO2 caused by human activities such as population density,industrial emissions and traffic,with lower values of atmosphericΔ14C associated with more intensive human activities.The fossil fuel derived CO 2 concentrations from May to September, 2009,ranged from 3.9±1.0 ppm to 25.4±1.0 ppm.It was calculated that each additional 1 ppm of CO2 from fossil fuels depleted the atmosphericΔ14C by approximately 2.70‰.This study suggests that 14C measurements of annual plants by AMS provide an effective method to rapidly trace fossil fuel derived CO2.     

Climatic and environmental implications from n-alkanes in glacially eroded lake sediments in Tibetan Plateau: An example from Ximen Co

Gas chromatography-mass spectrometry was used to identify a series of n-alkanes in the sediments of a typical glacially eroded lake in the eastern Tibetan Plateau.By comparing the distribution patterns of n-alkanes in lake sediments,surface soils and cow manure,it was shown that n-C 27-n-C 33 alkanes in the soil ecosystem of Ximen Co are derived from vascular plant species and that the distribution pattern of n-C 27-n-C 33 alkanes remains unchanged during the feeding and digestion processes of herbivores.The relative percentage of C 27,C 29 and C 31 n-alkanes decreased from the bottom to the top of the sediment core showing a trend of degradation of higher plants in the Ximen Co lake region during the formation of the 44 cm core.210 Pb dating,combined with pre-existing AMS 14 C dating results showed that the depositional core reflects climatic and environmental variations since about 900 years before present.The n-alkane indexes (ACL 27-33,P aq,P wax) are comparable with regional temperature variation,especially recording the Little Ice Age event (LIA).This study highlights that n-alkanes are valid proxies for paleo-climate and paleo-environment reconstruction,despite the same distribution patterns in n-alkane molecular fossils derived from a typical glacially eroded lake.     

Platygonus sp. (Mammalia: Tayassuidae) in Uruguay (Raigón? Formation; Pliocene–early Pleistocene), comments about its distribution and palaeoenvironmental significance in South America

This study provides the first record of Platygonus in Uruguay (Raigón? Formation, Pliocene–early Pleistocene; Canelones Department). The allocation to the Raigón Formation is tentative because the remains were found in a drill core. It is the oldest record of a tayassuid in Uruguay. The following morphological features clearly indicate that it belongs to Platygonus: simple premolars that are bicuspid, bunolophodont, mesodont and with an enamel cingulum surrounding the entire tooth. This is one of the largest forms among North American and South American Platygonus. The record of Platygonus in the Raigón Formation suggests arid or semi-arid climates, and, as do some associated birds and mammals, open or relatively open environments. A significant level of specific diversity of Platygonus in South America is recognized during the late Pliocene with the lowest diversity occurring during the early–middle Pleistocene.     

鄂尔多斯盆地北部古风化壳储层孔隙分布定量预测及非构造圈闭形成模式探讨

从化学动力学及热力学、流体动力学和弥散动力学角度 ,建立了接近实际地质条件的古风化壳储层岩溶斜坡地质模型和数学模型 ,在计算机上对模型的承压流、潜流模式流体 -岩石系统进行了动力学模拟研究 ,得出岩溶斜坡剖面上孔隙发育带和孔隙充填带的有利区和古风化壳储层孔隙演化分布规律 ,并探讨了相关非构造圈闭模式及有利部位     

Yunnanozoon是半索动物的远祖

对澄江化石库中Ｙｕｎｎａｎｏｚｏｏｎ（云南虫）重新研究表明，其身体由吻、邻和躯干三部发构成；躯干前段为具有成对鳃孔的咽腔，后段为消化区这种独特的身体造型与现生肠鳃类半索动物几无二致，从鸸 有明这个早寒武世动物是地球上半索动物门中书已知最古老的祖先类型。     

New finding of Mesozoic ephippia of the Anomopoda (Crustacea: Cladocera)

Fossil Mesozoic anomopods (Crustacea: Cladocera) have only been found twice previously, although this group apparently differentiated in the Palaeozoic. This paper describes the finding of anomopod ephippia of three different types in the locality Khutel‐Khara, Mongolia (Lower Cretaceous, 129±9 Mya). This discovery demonstrates once more that the idea of rarity of cladocerans in Mesozoic fossils was motivated by insufficient attention of carcinologists to such fossils.     

与大荔人头骨化石共生的双壳类化石及其环境意义

记述了与大荔人头骨化石共生的双壳类化石3属12种。通过与现生的相近双壳类生活环境的对比，得出大荔地区当时的气候环境主要受夏季风控制的暖湿气候的结论。结合对沉积特征的分析，引出了对该地区地貌演化模式的讨论。     

Yangtzedonta and the early evolution of shelled molluscs

The holotype of Yangtzedonta Yu, 1985 and its type species, Y. primitiva Yu, 1985, is an incomplete specimen of Xianfengella prima He et Yang, 1982. Therefore, based on the principle of priority, the names Yangtzedonta and Y. primitiva Yu (1985) should be abandoned. The fact that ventral valve of Xianfengella is bilaterally symmetrical indicates that they are not the left valve of a bivalved mollusc, as originally proposed by Yu. At present, the oldest certain bivalve is Xianfengoconcha elliptica Zhang, which occurs in the Early Cambrian Qiongzhusi Stage in China. The oldest known rostroconch is Heraultipegma yunnanensis He et Yang, which first occurs in the third small shelly fossil assemblage zone of the Early Cambrian Meishucunian Stage. The oldest known monoplacophoran, Maikhanella pristinis (Jiang), first occurs in the first small shelly fossil assemblage zone (Meishucunian Stage). Evidence derived from analyses of shell morphology, mode of growth, histology, and stratigraphic occurrence suggests that bivalves evolved from a branch of rostroconchs, and that rostroconchs in turn evolved from a branch of monoplacophorans. The hypothesis that these three groups originated simultaneously and independently at the beginning of the Cambrian and subsequently evolved in parallel, probably is incorrect.