Tepsankumpu revisited — pollen evidence of stable Eemian climates in Finnish Lapland

Several till-covered organic deposits, principally lake gyttja, in Finnish Lapland have been correlated with the last (i.e. Eemian) interglacial on the basis of their lithostratigraphic position and pollen stratigraphy. Most of the sequences are short, but together with three longer sequences from Finnish Lapland and one from Swedish Lapland (Leveäniemi) they provide a complete picture of Eemian vegetational and climatic development. The Tepsankumpu site was revisited, and the till-covered thick freshwater gyttja deposit was studied in detail for pollen in order to search for signals of rapid climatic fluctuations postulated for the earlier part of the Eemian on the basis of Greenland ice core studies. The Eemian pollen stratigraphy in Finnish Lapland closely resembles the Holocene pollen stratigraphy of the area. The abundance of spruce and alder pollen suggests, however, more northerly limits for forest vegetation zones during the Eemian than during the Holocene. Oak also grew closer to Lapland, indicating a wanner climate than during the Holocene climatic optimum. The Tepsankumpu pollen stratigraphy indicates climatic stability over the entire time-span it covers, i.e. the major part of the interglacial. This finding is in conflict with results from Greenland GRIP ice core studies and interpretations of some Continental European Eemian pollen diagrams.     

Historical floods within the Selenga river basin: chronology and extreme events

Large floods are among the most hazardous natural phenomena, which in many cases cause enormous losses to the economy and lead to human casualties. Along with the use of modern instrumental data, the analysis of historical information on large past floods is widely practiced in the world. This allows obtaining qualitative and quantitative characteristics of historical floods and significantly expanding the observation series. The Selenga River is one of the largest rivers of Central Asia with catchment area equal to 447,060 km², and also it is rather flood-prone river. The hydrological regime of the Selenga River is quite well studied in the twentieth century on the basis of gauging stations data, but there is still a lack of knowledge about past floods. In this paper, we present a list of 26 known floods within the Selenga River basin from 1730 to 1900, compiled from available historical documents (newspapers, scientific reports, diaries, memoirs, etc.). We estimated peak water levels for three catastrophic floods (1830, 1869 and 1897), the historical maximum of which was 850 cm. The reliability of our estimates is confirmed by a comparative analysis of the large 1971 flood. It was revealed that the largest floods can cause a rise of the Lake Baikal water level up to 200 cm. The inflow to Lake Baikal resulting from the largest floods in the Selenga River basin is comparable to the average annual inflow of water into the lake. We can conclude that the use of historical data for the analysis of floods in Eastern Siberia is quite acceptable, but some limitations must be taken into account.

     

Continental evaporites and the search for evidence of life on Mars

Continental evaporites are deposits that originate from the evaporation of saline waters in the low areas of saline lakes from all continents, except Europe, and mainly consist of chloride, sulphate and potash minerals. In recent years, the discovery on the Martian surface of hydrated salt minerals, including sulphates and chlorides, interpreted as deriving from the desiccation of preexisting large bodies of water, such as lakes, has provided further convincing evidence of liquid water activity on the surface of Mars and, consequently, it has reinforced the plausibility of finding life. Because evaporites require short‐term aqueous processes for their formation, they can trap and preserve over geologic times a biological record made up of halophilic extremophiles—such as microalgae, bacteria, and their remains—that recent research on Earth has shown to be characterized by unexpectedly high biodiversity. This record may consist of varying types of fossils, including morphological fossils, chemofossils and biominerals. As a consequence, continental evaporite environments and their saline deposits are now a primary target for the near future astrobiology missions devoted to the search for fossil Martian life. Lacustrine evaporite deposits and minerals have, therefore, been identified as primary targets for the NASA–ESA joint programme of the Mars sample return, planned for the end of the current decade. Copyright © 2011 John Wiley & Sons, Ltd.     

中国极端降水事件的频数和强度特征

使用1951-2004年中国738个测站逐日降水资料,采用百分位的方法定义极端降水事件的阈值,分析了不同持续时间的极端降水事件的时空分布及变化趋势特征。结果表明,极端降水事件多发于35°N以南,特别是在长江中下游和江南地区以及高原东南部,且在这些地区极端降水事件持续时间也较长。季节分布上,主要出现在夏季,以低持续性事件为主。在中国东部地区,持续时间越长的极端降水其强度往往越强。趋势分析表明,全国持续1d极端事件的相对频数具有上升趋势而平均强度具有下降趋势,其空间上均表现为全国大部分上升、华北和西南等地下降的趋势。持续2d以上极端事件在长江中下游流域、江南地区和高原东部等地区有显著增多和增强的趋势,而在华北和西南地区有减少和减弱趋势,但全国平均的趋势不显著。     

中国极端降水事件的区域性和持续性研究

利用中国542个站1960-2003年逐日降水资料,分析中国极端降水事件的区域性和持续性,研究发现:滇西藏东一带极端降水的持续性较好,但该地区极端降水的区域性较差;长江以南地区夏季极端降水的区域性与持续性均较好,容易导致区域性洪涝灾害的发生;东南沿海冬季极端降水的区域性与持续性均较好,易形成成片且持续时间在3d或3d以上的极端(较强)降水事件;黄河中下游秋季极端降水的区域性与持续性均较好,该地区秋季发生洪涝的可能性较大;除新疆以外,东北、华北以及西北等大部分北方地区极端降水的持续性以及区域性均较差。     

Mechanism and forecasting method of persistent extreme weather events: review and prospect

Persistent extreme weather is of high disaster causing capability, represents a great threat to the safety of both people and property and results in substantial economic losses. However, the underlying mechanism of such high impact weather remains unclear, and related forecasting methods are quite under studied currently. Based on the comprehensive reviews of the relevant studies about persistent extreme weather, the prediction of such events within the period during 1～2 weeks in advance is believed to be a significant scientific issue. For this scientific problem, the studies of atmospheric low frequency process, the interaction between multi scale systems, the forcing of complicated underlying surface and sea land atmosphere interactions are necessary to be performed. These multi perspective studies will favor the final establishment of the corresponding forecasting theory and method based on the combination of dynamical prediction and statistical predication. It is hoped that the deficiencies in systematic studies about persistent extreme weather may be made up through pertinent studies, which will prolong the time length of forecasting and increase the prediction precision of such high impact events.     

Petrological and zircon evidence for the Early Cretaceous granulite‐facies metamorphism in the Dabie orogen,China

An integrated study of petrology, mineralogy, geochemistry, and geochronology was carried out for contemporaneous mafic granulite and diorite from the Dabie orogen. The results provide evidence for granulite‐facies reworking of the ultrahigh‐pressure (UHP) metamorphic rock in the collisional orogen. Most zircons from the granulite are new growth, and their U‐Pb ages are clearly categorized into two groups at 122–127 Ma and 188.2 Ma. Although these two groups of zircons show similarly steep HREE patterns and variably negative Eu anomalies, the younger group has much higher U, Th and REE contents and Th/U ratios, much lower εHf(t) values than the older group. This suggests their growth is associated with different types of dehydration reactions. The older zircon domains contain mineral inclusions of Grt, Cpx and Qz, indicating their growth through metamorphic reactions at high pressures. In contrast, the young zircon domains would have grown through peritectic reaction at low to medium pressures. The younger granulite‐facies metamorphic age is in agreement not only with the adjacent diorite at 125.1 Ma in this study but also the voluminous emplacement of coeval mafic and felsic magmas in the Dabie orogen. Mineral separates from both mafic granulite and its adjacent diorite show uniformly lower δ18O values than normal mantle, similar to those for UHP eclogite‐facies metaigneous rocks in the Dabie orogen. In combination with major‐trace elements and zircon Lu‐Hf isotope compositions, it is inferred that the protolith of mafic granulites shares with the source rock of diorites, both being a kind of mafic metasomatites at the slab‐mantle interface in the continental subduction channel. This provides a direct link in petrogenesis between the granulitic, migmatic and magmatic rocks in the collisional orogen to active continental rifting, whereby high heat flow was transferred from the asthenospheric mantle into the thinned orogenic lithosphere for partia melting.     

Unstable climates: Exploring the statistical and social constructions of ‘normal’ climate

The idea of climate has both statistical and social foundations. Both of these dimensions of climate change over time: climate, as defined by meteorological statistics, changes for both natural and anthropogenic reasons; and our expectations of future climate also change, as cultures, societies and knowledge evolves. This paper explores the interactions between these different expressions of climate change by focusing on the idea of ‘normal’ climates defined by statistics. We show how this idea came into being in meteorological circles and then review how this idea of climatic normality gets entangled with cultural and psychological processes. Using data from historical and predicted climates in the UK, we illustrate the significance of choosing different baseline ‘normals’ for retrospective and prospective interpretations of climate change. Since the choice of these statistical ‘normals’ reflects cultural, political and psychological preferences and practices as much as scientific ones, we argue that expectations of the climatic future are influenced by social as well as statistical norms. Seeing climate as co-constructed between the psycho-cultural constraints of society and the physical constraints of the material world offers a different way of thinking about the instabilities of climate and the ways we adapt to them.     

Evolution of the carnivorous dinosaurs during the Cretaceous: The evidence from Patagonia

Patagonia has yielded the most comprehensive fossil record of Cretaceous theropods from Gondwana, consisting of 31 nominal species belonging to singleton taxa and six families: Abelisauridae, Noasauridae, Carcharodontosauridae, Megaraptoridae nov. fam., Alvarezsauridae, and Unenlagiidae. They provide anatomical information that allows improved interpretation of theropods discovered in other regions of Gondwana. Abelisauroids are the best represented theropods in Patagonia. They underwent an evolutionary radiation documented from the Early Cretaceous through to the latest Cretaceous, and are represented by the clades Abelisauridae and Noasauridae. Patagonian carcharodontosaurids are known from three taxa (Tyrannotitan, Giganotosaurus and Mapusaurus), as well as from isolated teeth, collected from Aptian to Cenomanian beds. These allosauroids constituted the top predators during the mid-Cretaceous, during which gigantic titanosaur sauropods were the largest herbivores. Megaraptorans have become better documented in recent years with the discovery of more complete remains. Megaraptor, Aerosteon and Orkoraptor have been described from Cretaceous beds from Argentina, and these taxa exhibit close relationships with the Aptian genera Australovenator, from Australia, and Fukuiraptor, from Japan. The Gondwanan megaraptorans are gathered into the new family Megaraptoridae, and the Asiatic Fukuiraptor is recovered as the immediate sister taxon of this clade. Although megaraptorans have been recently interpreted as members of Allosauroidea, we present evidence that they are deeply nested within Coelurosauria. Moreover, anatomical information supports Megaraptora as more closely related to the Asiamerican Tyrannosauridae than thought. Megaraptorans improve our knowledge about the scarcely documented basal radiation of Gondwanan coelurosaurs and tyrannosauroids as a whole. Information at hand indicates that South America was a cradle for the evolutionary radiation for different coelurosaurian lineages, including some basal forms (e.g., Bicentenaria, Aniksosaurus), megaraptorans, alvarezsaurids less derived than those of Laurasia, and unenlagiids, revealing that Gondwanan coelurosaurs played sharply differing ecological roles, and that they were taxonomically as diverse as in the northern continents. The unenlagiids represent an endemic South American clade that has been recently found to be more closely related to birds than to dromaeosaurid theropods. Analysis of the theropod fossil record from Gondwana shows the highest peak of origination index occurred during the Aptian–Albian and a less intense one in the Campanian time spans. Additionally, peaks of extinction index are recognized for the Cenomanian and Turonian–Coniacian time spans. In comparison, the Laurasian pattern differs from that of Gondwana in the presence of an older extinction event during the Aptian–Albian time-span and a high origination rate during the Cenomanian time-bin. Both Laurasian and Gondwanan theropod records show a peak of origination rates during the Campanian.     

In search for fingerprints of an extraterrestrial event: Trace element characteristics of sediments from the lake Medvedevskoye (Karelian Isthmus,Russia)

Concentration and distribution of trace elements across the sequence of the Late Pleistocene sediments from the lake Medvedevskoye suggest the addition of materials other than those from a common source for the lake sediments of the region. The sediments of the lake Medvedevskoye carry some geochemical fingerprints which could be related the ET event that occurred at ca. 12.9 ka. Because such fingerprints are extremely subtle, the NW Russia can be considered to be the most remote eastern region of the extent of the Late Pleistocene airborne ET material. The sediments of the lake Medvedevskoye can also contain volcanic material from the eruption of the Laacher See (Germany) volcano and probably from other Late Pleistocene volcanoes of Western Europe and/or Iceland.     

Toward a general procedure for analysis of extreme random events in the earth sciences

Engineering and scientific approaches to design magnitude estimation are briefly revisited. Some defense is offered for use of annual maxima in design as if they were variables from a common distribution. However, to assume any particular form of distribution tail beyond the largest data value is not justifiable, regardless of the degree of data support over the main body of the distribution. An alternative approach to the design problem is suggested through use of parameter-free nonparametric estimation using the kernel method. Some simulation results are presented which suggest that the parameter-free approach is worthy of further development. A particular advantage of nonparametric methods is that competing estimators can be checked against parametric distributions, leading to a progressive improvement in estimator accuracy.This paper was presented (by title) at Engineering Concepts, MGUS-87 Conference, Redwood City, California, 13–15 April 1987.     

Searches for extraterrestrial life in the solar system: Status and perspectives

The results of space studies of the Moon and Mars are considered from the perspective of questions related to the appearance and evolution of life, as presented in the monograph of I.S. Shklovskii “Universe, Life and Razum” (Vselennaya, Zhizn’, Razum [in Russian]).     

National vulnerability to extreme climatic events: the cases of electricity disruption in China and Japan

Extreme climatic events are likely to adversely affect many countries throughout the world, but the degrees among countries may be different. China and Japan are the countries with high incidences of extreme weather/disaster, both facing with the urgent task of addressing climate change. This study seeks to quantitatively compare the impacts of extreme climatic events on socioeconomic systems (defined as vulnerability) of the two countries by simulating the consequences of hypothetical same degree of electricity disruption along with extreme events. To do that, two computable general equilibrium models are constructed, by using which three-stage scenarios are simulated for China and Japan, respectively. The results reveal that China and Japan have unequal socioeconomic vulnerabilities to extreme events. (1) Negative impact of the same degree of power outages is bigger on China’s socioeconomic system than on that of Japan, and this difference is more obvious in the very short-run scenario. (2) The decline of China’s GDP, total output, and employment levels is 2–3 times higher than that of Japan, while the difference of the resident welfare levels is sharper, which of China drops 3–5 times of Japan. (3) Structural factors are the main reason for vulnerability differences between China and Japan, including the differences of expenditure structure, factor input structure for production of life requirement sectors, material and energy dependence for the production of industrial sectors, and usage structure of services outputs. Based on these findings, some policy implications and recommendations for fairness issues on climate change adaptation are proposed.     

The great 1950 Assam Earthquake revisited: Field evidences of liquefaction and search for paleoseismic events

Extensive field investigations were carried out for the first time in the meizoseismal area of the great 1950 Assam Earthquake aimed at exploring the paleoseismic history of the NE Indian region through documentation of liquefaction features and radiocarbon (¹⁴C) dating. Trenching at more than a dozen locations along the Burhi Dihing River valley and within the alluvial fans adjoining the Brahmaputra and Dibang Rivers resulted in the identification of more than a dozen very prominent liquefaction features (sand dykes, sills, sand blows etc.) as evidences of large to great earthquakes. ¹⁴C dating of the organic material associated with some of the features indicates a paleoseismic record of about 500 yrs archived by the sediments in this region. Compelling geological evidence(s) of the great 1950 earthquake are well constrained by ¹⁴C dating. Out of the two historically reported seismic events (1548 AD and 1697 AD) from this region, ¹⁴C dating could constrain the 1548 AD event though not distinctly. Further studies using combined ¹⁴C and OSL dating may better constrain the seismo-chronology of the study region.     

赣中相山地区白垩纪隐爆作用与铀成矿突发事件探讨

赣中相山地区是我国重要的铀资源生产基地,铀矿化产于相山火山侵入杂岩体中,主要由早白垩世熔结凝灰岩、流纹英安斑岩、碎斑熔岩、花岗斑岩、英安玢岩、煌斑岩等组成,杂岩体中还分布大量隐爆作用遗迹——隐爆碎屑岩,隐爆作用发生的时间与火山侵入杂岩活动时间一致或稍后.文章通过对隐爆碎屑岩野外地质调查及室内镜下观察,将隐爆碎屑岩划分为岩浆隐爆碎屑岩和热液隐爆碎屑岩,相应地将隐爆作用划分为岩浆隐爆作用和热液隐爆作用.岩浆隐爆作用主要指流纹英安斑岩侵入活动之后发生的隐爆活动和碎斑熔岩的隐爆侵入活动,发生在早白垩世早期;热液隐爆作用主要指英安玢岩侵入活动之后发生的、与铀成矿密切相关的热液隐爆活动,发生在早白垩世晚期或晚白垩世初期.从早白垩世早期到晚白垩世初期,隐爆作用呈现“弱—强—弱”的演化趋势.铀成矿作用与晚白垩世初期的热液隐爆作用有关,该隐爆作用与铀成矿时间同步,形成年龄约为90 Ma,铀成矿是一种突发事件.     

晚白垩世西峡盆地和夏馆盆地古地震事件的发现及意义

以大量的野外工作为基础,辅以地球化学研究,确定了西峡盆地和夏馆盆地普遍存在着古地震事件的物质记录。同沉积期古地震事件主要表现为同沉积小断裂、同沉积角砾岩层等,且同沉积地震事件对于河流侵蚀作用的产生具有重要的影响;成岩期古地震事件主要表现为沿断裂上盘砾岩的"涂抹"和成岩期形成的方解石擦磨晶体,以及由断裂(裂隙)所围限的不同于周侧岩性的块体。古地震事件的研究不仅可以为恐龙蛋的埋藏作用提供信息,也可以为研究古地理和古构造背景提供信息。     

Cretaceous crustal thinning in North Africa: Implications for magmatic and thermal events in the Eastern Tunisian margin and the Pelagic Sea

The integrated use of geological, geophysical, and geochemical data from Eastern Tunisia onshore and offshore samples indicate a crustal thinning induced from the Tethyan rifting. This is responsible for the subsequent evolution of the North African passive margin during the Late Cretaceous, and the creation of the fold–thrust belt and associated foreland deformations. This thinned crust was an area of mantle upwelling that favoured the increase of isotherms, the uprise of basalt magma, and the circulation of hydrothermal fluids. The Cretaceous magmatism generated a major hydrothermal event characterised by the circulation of hot fluids along faults and a relatively high heat flow in the basin. Temperature elevation and hydrothermal conditions led to alteration of basalts and generated a new mineral equilibrium around the enclosing sedimentary deposits.