Recently Ratified and Proposed Cambrian Global Standard Stratotype-section and Points

This paper briefly summarizes an officially ratified Global Standard Stratotype-section and Point (GSSP) and a proposed GSSP for global stages of the Cambrian System. The Luoyixi section near Luoyixi town, Guzhang, northwestern Hunan is ratified as the boundary stratotype for the base of the global Guzhangian Stage, which is the upmost stage of an unnamed series termed provisionally as Cambrian Series 3. The GSSP position lies 121.3 m above the base of the Huaqiao Formation in the section, coinciding with the first appearance of the cosmopolitan agnostoid trilobite Lejopyge leavigata. The Duibian B section at Duibian village, Jiangshan, western Zhejiang, is proposed as the boundary stratotype for the base of the proposed global Jiangshanian Stage that is the second stage of the Furongian Series. The proposed GSSP position lies 108.12 m above the base of the Huayansi Formation in the section, coinciding with the first appearance of the cosmopolitan agnostoid trilobite Agnostotes orientalius. This horizon is also with the first appearance of the cosmopolitan polymerid trilobite Irvingella angustilimbata.     

新疆卡拉麦里姜巴斯套组火山岩地球化学特征与构造意义

通过对新疆卡拉麦里姜巴斯套组火山岩野外地质特征、岩石学和高精度同位素年代学的研究,发现姜巴斯套组火山岩具典型双峰式组合,岩石类型包括玄武岩-酸性火山碎屑岩-玄武粗面安山岩;得到玄武粗面安山岩LA-ICP-MS锆石U-Pb年龄为(319.8±2)Ma(加权均方偏差值为3),表明姜巴斯套组火山岩形成于早石炭世谢尔普霍夫阶。对火山岩地球化学特征的研究表明,姜巴斯套组火山岩钙碱性系列、高钾钙碱性系列和钾玄岩系列岩石兼而有之,岩石的稀土元素配分曲线均为轻稀土元素富集型,无明显Eu异常,玄武岩和玄武粗面安山岩具有K正异常和Sr负异常,酸性火山碎屑岩表现出Nb、Ta和Ti显著亏损。总体来说,姜巴斯套组火山岩富集大离子亲石元素,相对亏损高场强元素。玄武岩和玄武粗面安山岩表现出大陆裂谷(大陆板内拉张区域)岩石特征;酸性火山碎屑岩表现出岛弧或者活动大陆边缘岩石属性。总之,姜巴斯套组火山岩形成于卡拉麦里洋盆闭合碰撞造山后的拉张伸展环境,卡拉麦里地区在早石炭世末期就进入了碰撞后的陆内伸展拉伸阶段。     

A late Quaternary lake record from the Qilian Mountains (NW China): evolution of the primary production and the water depth reconstructed from macrofossil, pollen, biomarker, and isotope data

The history (45–0 ka BP) of the aquatic vegetation composition of the shallow alpine Lake Luanhaizi from the NE Tibetan Plateau is inferred from aquatic plant macrofossil frequencies and aquatic pollen and algae concentrations in the sediments. C/N (range: 0.3–100), δ¹³C (range: −28 to −15‰), and n-alkane measurements yielded further information on the quantitative composition of sedimentary organic matter. The inferred primary production of the former lake ecosystem has been examined in respect of the alternative stable state theory of shallow lakes [Scheffer, M., 1989. Alternative stable states in eutrophic, shallow freshwater systems: a minimal model. Hydrobiological Bulletin 23, 73–83]. Switches between clear and turbid water conditions are explained by a colder climate and forest decline in the catchment area of Lake Luanhaizi. The macrofossil-based reconstruction of past water depth and salinity ranges, as well as other organic matter (OM) proxies allowed climatic inferences of the summer monsoon intensity during the late Quaternary. Around 45 ka BP, conditions similar to or even moister than present-day climate occurred. The Lake Luanhaizi record is further evidence against an extensive glaciation of the Tibetan Plateau and its bordering mountain ranges during the Last Glacial Maximum. Highest lake levels and consequently a strong summer monsoon are recorded for the early Holocene period, while gradually decreasing lake levels are reconstructed for the middle and late Holocene.     

Late middle pleistocene interglacial deposits at upper strensham,worcestershire, england

Pleistocene deposits containing the disarticulated skeleton of a mammoth, and associated faunal and floral remains, were discovered in July 1990 at Upper Strensham, Worcestershire. The environmental evidence from the fauna and flora together with limited geological evidence, indicates that the deposits accumulated within a low energy fluvial environment with a surrounding marsh and restricted tree cover on, or close to, the floodplain. The patchy occurrence of trees in a species-rich grassland is discussed, and the climatic significance of the fauna and flora is considered. The Strensham site lies within the valley of the River Avon, which is known to contain at least five altitudinally distinct river terraces. The deposits at Strensham lie beneath a terraced surface that cannot be accommodated within the existing framework of terrace development in the valley, and evidence is presented which may suggest that these deposits form a previously unrecognised fluvial unit, the Strensham Member of the Avon Valley Formation. Amino-acid age estimates from shells taken from the fossiliferous sediments of the Strensham Member suggest a correlation with Oxygen Isotope Stage 7. This correlation suggests that the temperate deposits at this site should be correlated with the temperate phase recorded at Marsworth, Buckinghamshire and Stoke Goldington in the valley of the Great Ouse.     

The effect of the Messinian Deep Stage on karst development around the Mediterranean Sea. Examples from Southern France

It is difficult to explain the position and behaviour of the main karst springs of southern France without calling on a drop in the water table below those encountered at the lowest levels of Pleistocene glacio-eustatic fluctuations. The principal karst features around the Mediterranean are probably inherited from the Messinian period (“Salinity crisis”) when sea level dropped dramatically due to the closing of the Straight of Gibraltar and desiccation of the Mediterranean Sea. Important deep karst systems were formed because the regional ground water dropped and the main valleys were entrenched as canyons. Sea level rise during the Pliocene caused sedimentation in the Messinian canyons and water, under a low hydraulic head, entered the upper cave levels.

The powerful submarine spring of Port-Miou is located south of Marseille in a drowned canyon of the Calanques massif. The main water flow comes from a vertical shaft that extends to a depth of more than 147 m bsl. The close shelf margin comprises a submarine karst plateau cut by a deep canyon whose bottom reaches 1,000 m bsl. The canyon ends upstream in a pocket valley without relation to any important continental valley. This canyon was probably excavated by the underground paleoriver of Port-Miou during the Messinian Salinity Crisis. Currently, seawater mixes with karst water at depth. The crisis also affected inland karst aquifers. The famous spring of Fontaine de Vaucluse was explored by a ROV (remote observation vehicle) to a depth of 308 m, 224 m below current sea level. Flutes observed on the wall of the shaft indicate the spring was formerly an air-filled shaft connected to a deep underground river flowing towards a deep valley. Outcroppings and seismic data confirm the presence of deep paleo-valleys filled with Pliocene sediments in the current Rhône and Durance valleys. In the Ardèche, several vauclusian springs may also be related to the Messinian Rhône canyon, located at about 200 m below present sea level. A Pliocene base level rise resulted in horizontal dry cave levels. In the hinterland of Gulf of Lion, the Cévennes karst margin was drained toward the hydrologic window opened by the Messinian erosional surface on the continental shelf.     

Grain-size characteristics and climate variability in TMS5e sequence of Tumen section in southern Tengger Desert, northwestern China

The TMS5e sequence from the Tumen section,at the southern edge of Tengger Desert in the northwestern China,is synchronous with Marine Isotope Stage 5e(MIS5e).It consists of 16 layers of aeolian dune sands,11 layers of lacustrine loess-like facies,and 5 layers of lacustrine facies.The results of grain-size analysis shows that the palaeo-mobile dune sands,palaeo-fixed to semi-fixed dune sands and loess-like sandy loams are mainly composed of sands,ranging from 70% to 96%;their silt contents ranged from 4% to 20%,and their clay contents ranged from 1% to 5%;the climate under which the aeolian dune sands were deposited is similar to that under which modern mobile dune sands form,which is caused by the dominance of the cold,dry East Asian winter monsoon.In contrast,the lacustrine loess-like facies and lacustrine facies had a lower sand contents than those of the three aeolian dune sands,but have higher silt and clay contents,most of their sand content ranged from 30% to 60%,their silt contents ranged from 35% to 55%,and their clay contents ranged from 6% to 20%.The lacustrine loess-like facies and lacustrine facies formed under the influence of the warm,humid East Asian summer monsoon based on their similarity with modern sediments.The grain-size indicator Mz(mean grain diameter) and the SC/D value in the TMS5e sequence indicate climatic insta-bility at the southern edge of the Tengger Desert during MIS5e,with at least 14 fluctuations between a warm,humid climate and a cold,dry climate,divided into five stages:TMS5e5(139 kyr to 129.3 kyr B.P.),TMS5e4(129.3 kyr to 124 kyr B.P.),TMS5e3(124 kyr to 119.5 kyr B.P.),TMS5e2(119.5 kyr to 116.5 kyr B.P.),and TMS5e1(116.5 kyr to 113.7 kyr B.P.).These correspond roughly to MIS5e5,MIS5e4,MIS5e3,MIS5e2,and MIS5e1,respectively,in the GRIP ice core data.     

Climate variability in the Salawusu River valley of the Ordos Plateau (Inner Mongolia,China) during Marine Isotope Stage 3

Fluctuations in climatic proxies of the Milanggouwan section in the Salawusu River valley of the Ordos Plateau (Inner Mongolia, China) during Marine Isotope stage 3 (MIS 3) coincide well with sedimentary cycles for palaeo‐mobile dune sands alternating with fluvial–lacustrine facies and palaeosols. We compared the palaeo‐mobile dune sands with modern mobile dune sands (products of a cold and dry climate dominated by the East Asian winter monsoon), whereas the fluvial–lacustrine facies and palaeosols were controlled by a wet–warm climate similar to that of the East Asian summer monsoon. The MIS 3 climate of the Salawusu River valley appears to have experienced at least nine wet–warm and ten cold–dry fluctuations, divided into five stages: MIS 3e (58 900–49500 yr BP), MIS 3d (49 500–40 700 yr BP), MIS 3c (40 700–36 900 yr BP), MIS 3b (36 900–27 000 yr BP) and MIS 3a (27 000–22 300 yr BP). The 19 cold–warm climatic fluctuations corresponded roughly to the GRIP and Guliyan records, and with fluctuations in the North Atlantic climate. Notable peaks in the spectral analysis occurred at 19 500 yr, 1020 yr, 640 yr and 500 yr. Our results show that the millennial–centennial climate was closely related to the relative strengths of East Asian monsoons, which are controlled by the North Atlantic thermohaline circulation, and which is also closely linked to the Sun's precession period. Copyright © 2008 John Wiley & Sons, Ltd.     

内蒙古萨拉乌苏河流域第四系更新统上部萨拉乌苏阶基本特征剖析

本文概述了对内蒙古萨拉乌苏河流域酒房台剖面更新统上部年代地层-萨拉乌苏阶初步研究的成果.萨拉乌苏阶底部为黄棕色砂层.底界年龄暂定为150 ka.顶界年龄约10 ka,萨拉乌苏阶上部与下部界线年龄约75 ka.萨拉乌苏阶下部以湖沼相沉积为主,夹风、河流堆积物:上部以风成砂为主,夹湖沼相沉积物.150 ka以来该区经受3次水体扩张3次风砂侵入.阶内代表性的古脊椎动物化石,下部是:鄂尔多斯人(即河套人)、主氏水牛、诺氏象、河套大角鹿、哈克图转角羊等:上部是:披毛犀和野驴等.古气候特征是:150～75ka期间,以温湿为主,但中间曾夹有多次气候波动.75～60 ka时期气候转为干冷、多风,60～20 ka间气候明显暖湿,20～10 ka气候又转温.     

陆相下白垩统阜新阶重新厘定及其层型剖面

实测辽宁省建昌县冰沟剖面,选择其为单位层型;开展岩石地层、多门类生物化石和沉积相分析等系统研究,重新厘定陆相阜新阶定义。建昌冰沟组主要由砾岩、砂岩、泥岩和煤层组成,分成三个岩段,第二段为煤系地层。该组为陆相湖盆扇三角洲沉积体系,相序叠置分析属砂砾坝、分流河道、泥沙坪、泥炭沼泽和洪积平原等沉积环境。通过研究以叶肢介为主的化石发生和演变序列,及综合前人研究资料,阜新阶生物地层划分包括叶肢介组合带3个、孢粉化石组合2个、双壳类组合1个和介形虫组合2个。底界层型定在小冰沟村西单一浅湖相地层中,生物标志为叶肢介Orthestheropsis originalis的始现。依据孢粉和介形虫化石资料,阜新阶对比为国际地层表早白垩世巴列姆阶(Barremian)~阿尔必阶(Albian)。     

“常么阶”沉积相及微相的研究与对比

研究、对比了广西宜山、隆林常么及贵州紫云扁平剖面常么阶的沉积相及微相类型。多元统计分析及碳酸盐岩岩石学的研究表明，这一地区常么阶至少有台前斜坡、台缘生物礁、礁后湖、台缘生物滩、开阔台地、局限台地及蒸发台地等７种沉积相类型及１２种具有不同环境意义的微相类型。古地理位置、水动力条件、循环状况是控制各剖面沉积过程及生物分布的主要环境因素；某些生物（如藻类）的繁盛可以对局部环境进行改造，并进而造成其它生物在种类和数量上的差异。西南地区常么阶代表了马平期与栖霞期之间海退序列的沉积，这一时期的环境变化对有关古生物类群的地理分布产生了重要影响