Hydrogeological Characteristics of a Karst Mountainous Catchment in the Northwest of Vietnam

This paper presents a preliminary assessment of the hydrogeological characteristics of a karst mountainous catchment, the Suoi Muoi River catchment, in the northwest of Vietnam. The catchment is located at 600 -700 m a.s.l. and covers an area of 284 km. Exposed limestone occupies 32% of the total catchment area. Various types of assessments have been carried out, including geological and hydrogeological field surveys, cave surveys, dye-tracer tests, meteorological and surface water monitoring. Geological studies and cave surveys have identified the most important active cave/conduit systems within the catchment. Although these data are essential, they are insufficient to make a comprehensive appraisal of the hydrologic nature of the catchment under interest. An attempt was made to calculate a global water balance of the catchment, based on short-term (15 months) meteorological and streamflow records. The results show that, despite the existence of a number of substantial cavem conduit systems, the groun     

Hydrogeological modeling as a tool supporting the interpretation of pollen proxies for palaeoclimate reconstitution: The Senegalese “niayes” case-study

The Niayes of Senegal are sahelian interdunal fens, that hosted an azonal subguinean vegetation during the Holocene thanks to the availability of fresh groundwater despite contrasted climatic conditions. Exploratory scenario-based modeling of the zonal hydrogeology has been conducted for different periods with the Cast3M code. The results show that the delay in the onset of humid vegetation ca. 10 ky cal. BP could be ecosystemic and denote a start of the African Humid Period (AHP) ca. 11.5 ky cal. BP. Alternatively, the AHP could have started earlier while its beneficial effects would have been canceled by low sea levels. Vegetation degradation around 7.5 ky cal. BP is shown to have resulted from a climate minoration, that possibly alleviated until 4 ky cal. BP. The rising watertable allowed the degraded forest to persist during that period however. The forest expansion that followed ca. 3.5 ky cal. BP had then clearly a climatic origin. The interpretation of pollens for climate research requires a careful filtering-out of local groundwater availability.     

The “Donauplatin”: source rock analysis and origin of a distal fluvial Au-PGE placer in Central Europe

The mineral assemblage and the sedimentological characteristics of the “Donauplatin” (Danubian fluvial placer containing platinum-group elements (PGE) and gold (Au)) are described for the first time in connection with upstream reference placer deposits near the potential source area in tributaries of the River Danube/Donau. Granulometric and morphometric data have been obtained using the CCD-based CAMSIZER technique. The platinum-group minerals (PGM; iridium, osmium, unknown iridium-osmium-sulfide, ruthenium-osmium-iridium alloys, platinum-iron alloys, iridium-bearing platinum, sperrylite) have been derived from ultramafic magmatic rocks, probably belonging to the ophiolitic series in the Tepla Barrandian unit of the Bohemian Massif. The Au-Pd-Cu compounds in the placer originated from dynamo-metamorphogenic processes in a sulfur-deficient environment at the SW edge of the Bavarian Basement. Gold in the “Donauplatin” has been reworked from a “secondary” or intermediate repository of lateritic gold (Boddington-type). Its primary source is supposed to be of orogenic origin. Provenance analyses of the associated non-heavy minerals point to high-pressure metamorphic rocks, igneous rocks (monazite) and high-temperature metamorphic rocks (750° to 850°C, zircon morphology). Garnet compositions indicate that meta(ultra)basic igneous rocks, calc-silicate rocks and skarns prevailed over paragneisses in the provenance area. Extraterrestrial processes creating the well-known Ries impact crater in the environs of Nördlingen during the Miocene have a minor share in the PGE budget by delivering molybdenum-ruthenium-osmium-iridium alloys and iridium solid-solution series (s.s.s.) minerals. Judging by the heavy mineral suites, Saxothuringian source rocks of the NE Bavarian Basement connected with the Donau River via the Naab River drainage system have not contributed to the element budget of the “Donauplatin” under study. Stream sediments which have been derived from this provenance area are characterized by low-temperature (LT) crystalline rocks and a considerable proportion of pegmatitic and metabauxitic material lacking in the Holocene sediments of the “Donauplatin”.     

Advances in research of Asian geology—A summary of 1:5M International Geological Map of Asia project

The International Geological Map of Asia at a 1:5,000,000 scale (IGMA5000) is the first digital Asian geological map under the standard of the Commission for the Geological Map of the World (CGMW). Major advances that have been achieved in compiling the map are manifested in the following understandings.

• (1)Large amounts of Mesozoic volcanic rocks occurring in the eastern Asian coastal area are mainly Cretaceous instead of Upper Jurassic–Lower Cretaceous. Most of the Carboniferous–Permian volcanic rocks in Central Asia seem not to be arc volcanics, but the product of an extensional stage. The basal boundary of the Meso-Neoproterozoic Jixian section in China is not dated at 1.8 Ga as defined previously, but less than 1.68 Ga.
• (2)The most significant Neoarchean tectono-thermal events in the Sino-Korean craton and the Indian craton took place at 2.5 Ga rather than at 2.7 Ga. The basement of the Yangtze craton was finally formed at 0.75–0.8 Ga, which is 0.2–0.3 Ga later than the Greenville orogenic cycle. Geologically, South China is identified to be an Early Paleozoic Caledonian foldbelt. The Qinling belt, where no oceanic basin was developed in Triassic times, is not an Indosinian collisional orogen, but a continental crust subduction one. When Pangea was formed, Indo-Australian Gondwana had been joined to Paleo-Asia and between them there was no oceanic basin, i.e. no Paleo-Tethys which continued from Paleozoic to Mesozoic. A huge Indosinian orogenic belt existed on the southern margin of Paleo-Asia to the north of the Zagros–Himalayas.
• (3)Asia is a composite continent consisting of three major cratons—the Siberian, Indian and Arabian and three huge orogenic belts with a number of minor cratons and numerous microcontinents included. The main body of the Asian continent took its shape during the Mesozoic. The orogenic belts belong respectively to three global tectonic domains: the Paleo-Asian, Tethyan and Pacific. The small cratons, such as Sino-Korea, Yangtze, Tarim, and Sibumasu are thought to be affiliated to the tectonic transform zone between Gondwana and Siberia. They had been situated on the northern margin of Gondwana before the disappearance of the Paleo-Asian Ocean, and were lying on the southern margin of Paleo-Asia after the closing of the Paleo-Asian Ocean and then the opening of the Tethys. The fact that ophiolites in Asia appear to get progressively younger in age from north to south throws light on the Phanerozoic evolutionary process of the dispersion of Gondwana and the accretion of Asia accompanied by a southward migration of its orogenic belts.

     

Russian Mountain Glaciers in a “Thawing” World: The First Estimates of the Balance of Greenhouse Gases in the Caucasus and Altai

Doklady Earth Sciences - In the modern sense, glaciers are a unique large terrestrial biome. They combine autotrophic–heterotrophic ecosystems with the most significant contribution of...     

The phenomenon of “self-focusing” in the gaseous disk of the Galaxy

We consider perturbations in interstellar gas excited by the gravitational field of the spiral-density wave that is responsible for the Galactic arms, taking into account thermal effects. Under the conditions of fairly efficient cooling, the reaction of the gas to the perturbing field is non-trivial: the thickness of the gaseous layer is reduced in the region of the Galactic disk where the density of the gas is enhanced. We call this effect “self-focusing,” and explain it using observational results for the Galactic radio emission in the 21 cm line. Under our assumptions, we find the control parameter (δ) governing the relationship between perturbations of the thickness of the gaseous disk and the gas density in the vicinity of the Galactic equator, i.e., this parameter shows whether the correlation between these quantities is positive or negative, and provides important additional information on the thermal properties of the medium. It can be used as a diagnostic in joint studies of Galactic structure and large-scale features of the interstellar gas. Estimates for the typical Galactic parameters show that the effect of self-focusing should be clearly manifest in the Galaxy.     

Topography of the Variscan orogen in Europe: failed–not collapsed

The Variscan orogenic collage consists of three subduction-collision systems (Rheno-Hercynian, Saxo-Thuringian and Massif Central-Moldanubian). Devonian to early Carboniferous marine strata are widespread not only in the individual foreland fold and thrust belts, but also in post-tectonic basins within these foreland belts and on the Cadomian crust of peri-Gondwanan microcontinental fragments, which represent the upper plates of the subduction/collision zones. These marine basins preclude high elevations in the respective areas and also in their neighbourhood. Widespread late Carboniferous intra-montane basins with their coal-bearing sequences are likewise incompatible with high and dry plateaus. While narrow belts with high elevations remain possible along active margins within the orogen, comparison of the Variscides with the Himalaya/Tibetan plateau is unfounded. Plausible reasons for the scarcity of high Variscan relief include subduction of oceanic and even continental crust, subduction erosion, orogen-parallel extension and—most important—lithospheric thinning accompanied by high heat flow and magmatism. In many areas, timing and areal array of magmatism and HT metamorphism are not compatible with a model of tectonic thickening and subsequent gravitational collapse. It is suggested, instead, that lithospheric thinning and heating are due to mantle activities caused by the Tethys rift. The lower and middle crust were thermally softened and rendered unfit for stacking and isostatic uplift: in terms of topography, the Variscides represent a failed orogen. The HT regime also explains the abundance of granitoids and HT/LP metamorphic rocks typical of the Variscides. Melting in the HT regime extracted mafic components from Variscan and Cadomian crust as well as from Cadomian metasomatized lithospheric mantle, thus mimicking subduction-related magmatism. The onset of the HT regime at c. 340 Ma may also have triggered the final ascent of HP/UHP felsic metamorphic rocks.     

The Nature of the “Voice of the Sea”

Strong vibrations of the Earth’s crust in the frequency range of 7–9 Hz, referred to as the “voice of the sea,” have been recorded in the course of processing synchronous experimental data obtained during recording of variations in the deformation of the Earth’s crust using a shore laser strainmeter, atmosphere pressure variations using a laser nanobarograph, and hydrosphere pressure variations using a laser meter for hydrospheric pressure and wind velocity variations. The nature of these vibrations and their transformation to adjacent geospheres have been discussed.     

Map presentation of changes in Europe’s artificial surfaces for the periods 1990–2000 and 2000–2006

The landscapes of the world are constantly changing under the influence of human activities leading to the growth of artificial surfaces. The covering of soil by artificial surfaces is referred to as soil sealing. Aerial and satellite images or data derived from them (for instance CORINE land cover — CLC data used here) provide important information that makes it possible to assess the occurrence, area and rate of soil sealing. As the term sealed soil cannot be wholly identified with the content of the appropriate CLC classes, the term land cover flow urbanization (LCFU) will be used here. The essence of this study is the demonstration and documentation of the trends of the LCFU in Europe for the periods 1990–2000 and 2000–2006 on a single map. This may contribute to a better spatial awareness of the ongoing transformation of landscape under the effects of human activities in an pan-European context. Changes in the LCFU can be seen on a map, compiled from 3 × 3 km squares at an all-European scale, using colours and their hues, to fulfil the role both of identification and classification. The colour method employed makes it possible to perceive three groups of LCFU changes on two time horizons, that is, whether the rate of LCFU in 2000–2006 increased or remained the same (hues of red); or dropped compared to the 1990–2000 period (hues of light to dark blue). The third group represents the LCFU with rates higher or lower than the average (countries with changes recorded in only one time horizon are presented in dark and light magenta colours).     

The Cretaceous-Tertiary boundary in a sector of the south limb of the Miranda-Treviño synclinal: the first appearance of chelonia and archosauria in the Basque country

This paper presents a study of the Cretaceous-Tertiary boundary in the Miranda-Treviño Synclinorium (Basque-Cantabric basin) where two main sequences have been recognised; the lower is regressive and theupper one has a marked transgressive trend. They are separated by a low angled un-conformity which is indicative of the Maastrichtian-Danian boundary.The lower sequence (S1) indicates a clear transition between the shoreface and backshore sub-environments. Bone accumulations are located in the sandy sediments of the upper foreshore and backshore, associated with ferrugenous hardgrounds and gypsum efflorescences.The upper sequence (S2) indicates the beginning of a marine transgression. It is composed a dominantly carbonate-rich sediments and the fauna suggests a deposition in environmental conditions ranging from stenohaline, to littoral, and to a coastal lagoon and inner carbonaterich platform.In the lower sequence (Maastrichtian Unit S₁ U₃), the following herpetofauna have been identified; an eusuchian alligator, and two dinosaurs (an ornithopod and a sauropod). Several plates of chelonia have been identified as? Adocus sp.     

Constraining the onset of the Holocene “Neoglacial” over the central Italy using tephra layers

A study of six tephra layers discovered in different deposits between 1600 and 2700 m a.s.l. in the Apennine chain in central Italy allowed precise stratigraphic constraints on environmental and climatic changes between ca. 4.5 and 3.8 cal ka BP. Chemical analyses allowed the correlation of these tephra layers with the eruptions of Agnano Mt Spina (AMST) from Phlegrean Field and Avellino (AVT) from Somma–Vesuvius. Major environmental changes in the high mountains of the Central Apennines occurred just after the deposition of the AMST and predate the deposition of the AVT. At this time, renewed growth of the Calderone Glacier occurred, marking the onset of the Apennine “Neoglacial”. The presence of the AMST and AVT enabled us to make a precise, physical correlation with other archives in central Italy. Synchronization of records between sites showed that the period intervening the deposition of the AMST and AVT layers coincided with environmental changes that were not always exactly in phase. This highlights the fact that stratigraphic correlations using only radiocarbon chronologies (the most common method used for dating archives during the Holocene) could produce erroneous correlation of events, giving rise to oversimplified paleoclimatic reconstructions.     

The results of geochronological and isotope–geochemical study of zircons from tuff of the Sylvitsa Group (western slope of the Middle Urals): The origin of ash layers in Vendian rocks of the East European Platform

Doklady Earth Sciences - New LA-ICP-MS data on the U–Pb isotope age, Hf isotope characteristics, and concentrations of trace elements in zircons from volcanic tuff of the Upper Vendian...     

Land sharing not sparing in the “green economy”: The role of livelihood bricolage in conservation and development in the Philippines

In Southeast Asia’s green economy, conservation interventions intensify the production of resources as commodities through land sparing activities and zoning in extensively used landscapes. Such initiatives encounter problems where poor resource users diversify livelihoods in multi-functional landscapes over time. In terms of ‘livelihood bricolage’ – the mixing, matching and building of portfolios – we describe how forest users enhance security by building dynamic livelihood portfolios based on the economic and socio-cultural considerations of place. Philippine case studies show how disrupting livelihood bricolage in multi-functional landscapes with ‘intensifying interventions’ spatially constrains livelihood security and conservation objectives. We conclude that more equitable forest governance supports land sharing with diverse, extensive livelihoods in varied landscapes.     

The “Problem of the quaternary” and the taxonomic rank of the late cenozoic in the international stratigraphic scale

An international scientific conflict has arisen around the International Stratigraphic Scale, the main document that regulates the rules of reading of geological records and, hence, concerns all Earth sciences. The matter of debate is the geological time scale of 2004, developed by the International Commission on Stratigraphy, where the Quaternary system was abandoned. This ICS decision triggered a protest among Quaternary geologists, members of INQUA, and became the subject of much controversy. This article provides a comprehensive analysis of the Quaternary problem and proposes a reasonable scientific solution that may be appropriate for both parties.     

The degradation of submarine permafrost and the destruction of hydrates on the shelf of east arctic seas as a potential cause of the “Methane Catastrophe”: some results of integrated studies in 2011

On the basis of the analysis of published data and in the course of the authors’ long-term geochemical and acoustic surveys performed in 1995–2011 on the East Siberian shelf (ESS) and aimed to research the role of the Arctic shelf in the processes of massive methane outbursts into the Earth’s atmosphere, some crucially new results were obtained. A number of hypotheses were proposed concerning the qualitative and quantitative characterization of the scale of this phenomenon. The ESS is a powerful supplier of methane to the atmosphere owing to the continued degradation of the submarine permafrost, which causes the destruction of gas hydrates. The emission of methane in several areas of the ESS is massive to the extent that growth in the methane concentrations in the atmosphere to values capable of causing a considerable and even catastrophic warning on the Earth is possible. The seismic data were compared to those of the drilling from ice performed first by the authors in 2011 in the southeastern part of the Laptev Sea to a depth of 65 m from the ice surface. This made it possible to reveal some new factors explaining the observed massive methane bursts out of the bottom sediments.