Low-latitude seasonality of Cretaceous temperatures in warm and cold episodes

The Cretaceous period is generally considered to have been a time of warm climate. Evidence for cooler episodes exists, particularly in the early Cretaceous period, but the timing and significance of these cool episodes are not well constrained. The seasonality of temperatures is important for constraining equator-to-pole temperature gradients and may indicate the presence of polar ice sheets; however, reconstructions of Cretaceous sea surface temperatures are predominantly based on the oxygen isotopic composition of planktonic foraminifera that do not provide information about such intra-annual variations. Here we present intra-shell variations in delta18O values of rudist bivalves (Hippuritoidea) from palaeolatitudes between 8 degrees and 31 degrees N, which record the evolution of the seasonality of Cretaceous sea surface temperatures in detail. We find high maximum temperatures (approximately 35 to 37 degrees C) and relatively low seasonal variability (< 12 degrees C) between 20 degrees and 30 degrees N during the warmer Cretaceous episodes. In contrast, during the cooler episodes our data show seasonal sea surface temperature variability of up to 18 degrees C near 25 degrees N, comparable to the range found today. Such a large seasonal variability is compatible with the existence of polar ice sheets.     

High temperatures in the Late Cretaceous Arctic Ocean

To understand the climate dynamics of the warm, equable greenhouse world of the Late Cretaceous period, it is important to determine polar palaeotemperatures. The early palaeoceanographic history of the Arctic Ocean has, however, remained largely unknown, because the sea floor and underlying deposits are usually inaccessible beneath a cover of floating ice. A shallow piston core taken from a drifting ice island in 1970 fortuitously retrieved unconsolidated Upper Cretaceous organic-rich sediment from Alpha ridge, a submarine elevated feature of probable oceanic origin. A lack of carbonate in the sediments from this core has prevented the use of traditional oxygen-isotope palaeothermometry. Here we determine Arctic palaeotemperatures from these Upper Cretaceous deposits using TEX86, a new palaeothermometer that is based on the composition of membrane lipids derived from a ubiquitous component of marine plankton, Crenarchaeota. From these analyses we infer an average sea surface temperature of approximately 15 degrees C for the Arctic Ocean about 70 million years ago. This calibration point implies an Equator-to-pole gradient in sea surface temperatures of approximately 15 degrees C during this interval and, by extrapolation, we suggest that polar waters were generally warmer than 20 degrees C during the middle Cretaceous (approximately 90 million years ago).     

羌塘盆地那底岗日地区上侏罗统—下白垩统碳酸盐岩微量元素与古环境

那底岗日剖面是羌塘盆地发育最完整的上三叠统-下白垩统剖面之一。采用V/Cr、V/Sc、V/(V+Ni)、Th/U、Ni/Co和Fe2+/Fe3+的比值作为判断氧化还原环境的指标,Mn、Ti、P的富集程度推断古气候,Sr/Ba、Sr/Ca、Rb、V/Ni反映古盐度变化,结合沉积相的分析,研究那底岗日地区晚侏罗世-早白垩世的古环境变化。结果表明:上侏罗统索瓦组为开阔台地相,形成于贫氧的干旱炎热高盐度环境;下白垩统索瓦组经历了局限台地相和三角洲相沉积环境,形成于氧化-贫氧的潮湿-干旱炎热高盐度环境,且盐度高于上侏罗统。剖面中页岩产出层位与下白垩统海相油页岩的产出层位相当,均为潟湖相沉积;该时期气候温暖潮湿,有利于生物的大量繁殖,导致区域上大规模油页岩的沉积。     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

海南岛西北岸三万年前后浅海相地层的发现及其意义

在海南岛西北部神尖沿岸地区,广泛出露一套富含海相化石的粉细砂—砾石沉积层,组成了高达20米左右的沿岸台地。该地层中所含化石组合主要有海扇、曼氐孔楯海胆、舌骨牡蛎和个体很大的盖虫。根据岩性、沉积相及~(14)C年代数据可知,在距今三万年前后,这里是一个环境比较稳定的热带浅海湾。海水的温度比现在高。我国其它沿海地区,在0—-27米也普遍存在三万年前后的海相沉积层。不同的是,海南岛西北岸三万年前后的海相层,因受后期火山作用而被抬升至高于现代海面20米左右。     

鲁西隆起蒙山晚白垩世-新生代抬升的裂变径迹证据

 研究晚白垩世以来蒙山的抬升对全面认识鲁西隆起区的构造演化具有重要的意义。对采自蒙山山脉的6个岩石样品进行了磷灰石/锆石裂变径迹测年及热历史模拟分析。分析结果表明蒙山自晚白垩世开始快速抬升,经历了70~43 Ma和32~20 Ma两个快速抬升阶段,并且蒙山的抬升表现出加速抬升的特征。晚白垩世以来蒙山的快速抬升与其毗邻的泰山有着较好的对应关系,蒙山的整体抬升略早于泰山,并且鲁西隆起的抬升表现出由南向北的抬升序列。蒙山的两期快速抬升事件很好地对应了济阳坳陷在这两个时期经历的构造沉降和区域隆升过程,表明新生代蒙山的快速抬升与济阳坳陷的构造演化有着良好的隆拗耦合关系。     

哈维氏弧菌TS-628菌株抗原性研究

哈维氏弧菌(Vibrio harveyi)是海水鱼虾养殖中常见的致病菌,由该菌引发的病害给世界各地的养殖业带来重大经济损失,但对其有效抗原的筛选或相关疫苗的研究报道相当少,对其病害的防治也尚无有效措施.本文以患病青石斑鱼分离到的病原菌哈维氏弧菌TS-628菌株为研究对象,分别提取它的鞭毛蛋白、脂多糖(LPS)和外膜蛋白(OMP),并采用Western blot技术分析检测这3种成分的抗原性.结果显示,鞭毛蛋白主要的免疫印迹带约有4条,其中43、52 ku为主要免疫反应显色带;OMP主要的免疫印迹带约有5条,其中43 ku为最主要免疫反应显色带, 35、38、47和52 ku也具有较强的免疫显色反应.LPS没有检测到免疫印迹反应.这一研究结果将为灵敏检测哈维氏弧菌以及研制高效疫苗奠定基础.     

Effect of evaporite deposition on Early Cretaceous carbon and sulphur cycling

The global carbon and sulphur cycles are central to our understanding of the Earth's history, because changes in the partitioning between the reduced and oxidized reservoirs of these elements are the primary control on atmospheric oxygen concentrations. In modern marine sediments, the burial rates of reduced carbon and sulphur are positively coupled, but high-resolution isotope records indicate that these rates were inversely related during the Early Cretaceous period. This inverse relationship is difficult to reconcile with our understanding of the processes that control organic matter remineralization and pyrite burial. Here we show that the inverse correlation can be explained by the deposition of evaporites during the opening of the South Atlantic Ocean basin. Evaporite deposition can alter the chemical composition of sea water, which can in turn affect the ability of sulphate-reducing bacteria to remineralize organic matter and mediate pyrite burial. We use a reaction-transport model to quantify these effects, and the resulting changes in the burial rates of carbon and sulphur, during the Early Cretaceous period. Our results indicate that deposition of the South Atlantic evaporites removed enough sulphate from the ocean temporarily to reduce biologically mediated pyrite burial and organic matter remineralization by up to fifty per cent, thus explaining the inverse relationship between the burial rates of reduced carbon and sulphur during this interval. Furthermore, our findings suggest that the effect of changing seawater sulphate concentrations on the marine subsurface biosphere may be the key to understanding other large-scale perturbations of the global carbon and sulphur cycles.     

Discovery of Late Cretaceous foraminifera in the Songliao Basin: Evidence from SK-1 and implications for identifying seawater incursions

The Songliao Basin is the largest oil-bearing basin in China.In the absence of sufficient evidence,the possibility of seawater incursion(s) into the Songliao Basin remains controversial.Recently,we discovered relatively abundant foraminifera fossils from units 1 and 2 of the Nenjiang Formation of borehole SK-1.Benthic foraminifera (Gavlinella sp.,Anomalinoides sp.,Pullenia sp.,Haplophragmoides sp.,Karrorulina hokkaidoana,Clavulinoides sp.),as well as planktonic foraminifera (Archaeoglobigerina blowi,Archaeoglobigerina cretacea and Hedbergella flandrini),were identified.These fossils were widely distributed in the marine Cretaceous.According to the global distribution of the above-mentioned planktonic foraminifera,the age of these fossil bearing strata appears to be Late Coniacian to Santonian.More importantly,these foraminifera provide direct evidence for marine water incursions into the Songliao Basin during deposition of the Lower Nenjiang Formation.     

Magnetostratigraphic study of Cretaceous depositional succession in the northern Kuqa Depression, Northwest China

Stratigraphic studies on the depositional succession in the Kuqa Depression can be traced back to as early as 1950s[1], however, there are still some disputes about chronostratigraphic division of the Bashenjiqike For- mation because of the paucity of fos…     

川西地区中二叠统-下三叠统碳酸盐岩碳氧同位素特征

 针对川西地区中二叠统-下三叠统碳酸盐岩,通过分析3 个剖面的碳氧同位素数据,计算Z 值及古温度,并结合沉积相、古生物等,对该区域碳酸盐岩碳氧同位素演化特征及古环境进行了系统研究。结果表明,川西地区中二叠统-下三叠统碳酸盐岩的δ¹³C 值为-3.90‰~2.80‰,主要值域为-2.80‰~2.80‰,均值为-0.04‰;δ¹⁸O 值为-9.70‰~-1.80‰,主要值域为-8‰~-4‰,均值为-6.60‰。研究区古环境基本处于海相环境,东北边缘水体相对较深,西南边缘水体相对较浅,海水温度为8.8~68.4℃,主要值域为16~33℃,属于温暖或炎热的亚热带气候,经历了栖霞期-茅口期、吴家坪期-长兴期、飞仙关期-嘉陵江期3 次大的海平面变化旋回,且其间各有若干次次级旋回。     

High-latitude influence on the eastern equatorial Pacific climate in the early Pleistocene epoch

Many records of tropical sea surface temperature and marine productivity exhibit cycles of 23 kyr (orbital precession) and 100 kyr during the past 0.5 Myr (refs 1-5), whereas high-latitude sea surface temperature records display much more pronounced obliquity cycles at a period of about 41 kyr (ref. 6). Little is known, however, about tropical climate variability before the mid-Pleistocene transition about 900 kyr ago, which marks the change from a climate dominated by 41-kyr cycles (when ice-age cycles and high-latitude sea surface temperature variations were dictated by changes in the Earth's obliquity) to the more recent 100-kyr cycles of ice ages. Here we analyse alkenones from marine sediments in the eastern equatorial Pacific Ocean to reconstruct sea surface temperatures and marine productivity over the past 1.8 Myr. We find that both records are dominated by the 41-kyr obliquity cycles between 1.8 and 1.2 Myr ago, with a relatively small contribution from orbital precession, and that early Pleistocene sea surface temperatures varied in the opposite sense to local annual insolation in the eastern equatorial Pacific Ocean. We conclude that during the early Pleistocene epoch, climate variability at our study site must have been determined by high-latitude processes that were driven by orbital obliquity forcing.     

阳江原生态红树林土壤放线菌Streptomyces sp. strain V65的次级代谢产物

 一株分自阳江原生态红树植物老鼠簕根部土壤的放线菌Streptomyces. strain V65在高氏Ⅰ号培养基中可产生丰富的红色素。采用硅胶柱色谱、反相硅胶柱色谱、LH-20凝胶柱色谱等技术对其菌体和培养液的提取物进行分离,初步得到2个红色素和1个酰胺类化合物;它们的结构通过核磁共振波谱技术及质谱技术鉴定,分别为：Undecylprodigiosin(Ⅰ) Metacycloprodigiosin(Ⅱ)和SW-B(Ⅲ)((2E,4E)-2,4,6-trimethyldeca-2,4-dienamide)。这是首次关于阳江原生态红树林海洋放线菌Streptomyces. strain V65次级代谢产物研究的报道。     

Glacier changes during the last forty years in the Tarim Interior River basin, northwest China

By comparing digitized glacier outlines from the Chinese Glacier Inventory (CGI) during the 1960s–1970s and Landsat Enhance Thematic Mapper (ETM+) images from 1999 to 2001, we investigated changes for about 7665 alpine glaciers among 11665 glaciers in seven sub-basins of the Tarim Interior River basin (TIRB). The results showed that the total glacier area was reduced by 3.3% from the 1960s/ 1970s to 1999/2001 and area losses for 1–5 km2 glaciers accounted for 48.3% of the total glacier area loss in the TIRB. However, the glacier area reductions varied from 0.7% to 7.9% among the seven sub-basins of the TIRB during the study period. The glacier area changing with altitude showed that the maximum contribution of area shrinkage occurred at 4900–5400 m. Data from 25 meteorological stations in the TIRB showed increases in both the annual mean air temperature and annual precipitation during 1960–2000. This indicates that the glacier shrinkage in the TIRB over the last 40 years was largely due to regional climate warming that enhanced glacier ablation and overcame the effects of increased precipitation on the glacier mass balance.     

Marine dinoflagellates from Lower Cretaceous Muling Formation of Jixi Basin,China and their palaeoenvironmental significance

Newly discovered marine dinoflagellates from the lower-middle parts of the Lower Cretaceous Muling Formation of the Jixi Basin, eastern Heilongjiang Province,China, were identified as Circulodinium cingulatum He et al.,C. attadalicum (Cookson et Eiscnack) Helhy, Palaeoperidinium cretaceum Pocock, Oligosphaeridium totum Brideaux and Sentusidinium sp. Most of these species are distributed in the marine Lower Cretaceous strata of Europe, North America,Africa, Australia and Asia. It demonstrates that a transgression occurred in eastern Heilongjiang Province during the deposition of the Muling Formation, which was previously considered to be a coal-bearing continental stratigraphic unit.The marine dinoflagellates indicated that the Muling Formation is Barremian in age. The Palaeogeographic framework of eastern HeUongjiang Province in Late Mesozoic era should be rebuilt through systematic facies analyses of the marine,paralic and terrestrial deposits.     

A 2500-year sea level change record in Fildes Peninsula, Antarctica

A detailed record of sea level changes during the last 2500 years is preserved in the northernwest coast of Fildes Peninsula in Antarctica. Fourteen marine alga layers were deposited in the beach with an altitude of 2.80 m, and one diatom layer deposited in the ancient lake on the terrace with an altitude of 6.84 m. A radiocarbon age of 695±70 aBP was obtained for the modern marine alga, and the age was used in correction for the carbon reservoir effect of the marine alga. Sea level fell 4.98 m from the 4th century B.C. to the early 13th century, at an average of -0.31 cm/a, then rose about 0.78 m during the early 13th to the middle 18th century, at an average of 0.14 cm/a. It has risen about 0.16 m since the middle 18th century, at an average of 0.07 cm/a.     

Cretaceous oceanic anoxic event 2 triggered by a massive magmatic episode

Oceanic anoxic events (OAEs) were episodes of widespread marine anoxia during which large amounts of organic carbon were buried on the ocean floor under oxygen-deficient bottom waters. OAE2, occurring at the Cenomanian/Turonian boundary (about 93.5 Myr ago), is the most widespread and best defined OAE of the mid-Cretaceous. Although the enhanced burial of organic matter can be explained either through increased primary productivity or enhanced preservation scenarios, the actual trigger mechanism, corresponding closely to the onset of these episodes of increased carbon sequestration, has not been clearly identified. It has been postulated that large-scale magmatic activity initially triggered OAE2 (refs 4, 5), but a direct proxy of magmatism preserved in the sedimentary record coinciding closely with the onset of OAE2 has not yet been found. Here we report seawater osmium isotope ratios in organic-rich sediments from two distant sites. We find that at both study sites the marine osmium isotope record changes abruptly just at or before the onset of OAE2. Using a simple two-component mixing equation, we calculate that over 97 per cent of the total osmium content in contemporaneous seawater at both sites is magmatic in origin, a approximately 30-50-fold increase relative to pre-OAE conditions. Furthermore, the magmatic osmium isotope signal appears slightly before the OAE2-as indicated by carbon isotope ratios-suggesting a time-lag of up to approximately 23 kyr between magmatism and the onset of significant organic carbon burial, which may reflect the reaction time of the global ocean system. Our marine osmium isotope data are indicative of a widespread magmatic pulse at the onset of OAE2, which may have triggered the subsequent deposition of large amounts of organic matter.     

基于PLC的船舶冷藏集装箱控制装置设计

为了开发具有自主知识产权并且能够满足船用冷藏集装箱应用要求的制冷机组控制系统,设计了一种基于PLC的新型船用冷藏集装箱控制装置。该装置利用触摸屏上位机对系统的运行进行在线监控,并采用压缩机变频调节为主,热气旁通调节为辅的控制策略,实现箱内温度控制。机组的运行实验结果表明,控制装置在冷藏模式下从28 ℃降至0 ℃仅需约810 s,冷冻模式从27 ℃降至-18 ℃仅需约2100 s,箱内温度控制的静态偏差±0.3 ℃,具有良好的控制品质。     

Oxygen isotope geochemistry of phosphorite and dolomite and palaeo-ocean temperature estimation: A case study from the Neoproterozoic Doushantuo Formation, Guizhou Province,South China

The Neoproterozoic Doushantuo Formation at Weng'an in Guizhou Province of South China consists of phosphorites and dolomites.Three types of samples are recongnized for the phosphate-bearing rocks.In Type I samples, interstitial phosphates occur within the dolomite rocks, whereas in Type III samples, interstitial dolomites occur within the phosphorites; both of them may have diagenetic origin.The Type II samples are interbedded phosphorites and dolomites.Oxygen isotopic compositions of phosphate and coeval carbonate were analyzed.Phosphates of Type I and II samples show similar low δ18Ophos (SMOW) values of 10.9‰～12.1‰ and 10.7‰～12.8‰, respectively, whereas Type III phosphates show higher δ18Ophos (SMOW) values of 13.2‰～15.0‰.Dolomites from Type I and II samples have δ18Ocarb (PDB) and δ13Ccarb (PDB) values of -6.2‰～-3.4‰ and -2.2‰～-0.7‰, respectively, whereas interstitial dolomites from Type III samples show lower δ18Ocarb (PDB) and δ13Ccarb (PDB) values of -12.9‰～-8.6‰ and -4.4‰～-2.6‰.Petrology and oxygen isotope data suggest that diagenetic alteration may have partially affected the studied rocks, but the dolomites from Type I and phosphates from Type III samples represent the most pristine isotopic compositions of primary carbonates and phosphates precipitated from seawater.Calculations of palaeocean temperatures from the most 18O enriched dolomite and phosphate indicate a temperature range of 32.2 ℃ to 34.0 ℃ for the seawater of the Doushantuo Formation period.Ce anomaly also suggests more oxic conditions and possibly shallower water depth in the upper strata of the Doushantuo Formation at Weng'an, Guizhou Province.     

Environmental and biogeo-chemical process of accumula-tion of iron-phosphorus in marine sediments

This paper discusses the environmental andbiogeochemical process of accumulation of iron-phosphorusin marine sediments for the north aktian of the South ChinaSea and analyzes the relationships between the contents ofiron, phosphorus and calcium carbonate as well as their ex-istent characteristics. The results show that the variances ofphosphorus and calcium carbonate contents with depths areopposite and those of iron and calcium carbonate contentsare almost accordant. It is not only related to the biogeo-chemical process of accumulation of biogenous calcium car-bonate in sediments, which resulted from the fact that themarine primary productivity was stimulated by part of ter-rigenous phosphorus dissolved into seawater due to declineof superficial water temperature and increase of carbon di-oxide content in the glacial period, but also related to ironimpelled oxidation and accelerated deposit by the dissolvedoxygen from the atmosphere and the photosynthesis of hy-drophytes in seawater. The variance of soluble iron-phos-phorus species (Fe-P) in sediment columns can sensitivelyreflect the changes of climate and environment, which sug-gests that the accumulative characteristics and existent statesof iron-phosphorus species (Fe-P) in marine sediments havethe significance as an indicator of the changes of paleocli-mate and paleoenvironment.