Architecture of growth basins in a tidally influenced,prodelta to delta-front setting: The Triassic succession of Kvalpynten,East Svalbard     

Aleksandra Smyrak-Sikora  Per Terje Osmundsen  Alvar Braathen  Kei Ogata  Ingrid Anell  Mark J. Mulrooney  Valentin Zuchuat 《Basin Research》2020,32(5):949-978

World-class examples of fault-controlled growth basins with associated syn-kinematic sedimentary fill are developed in Upper Triassic prodelta to delta-front deposits exposed at Kvalpynten, SW Edgeøya in East Svalbard. They are interpreted to have interacted with north-westerly progradation of a regional delta system. The syn-kinematic successions consist of 4 to 5 coarsening-upward units spanning from offshore mudstones to subtidal heterolithic bars and compound tidal dunes, which were blanketed by regional, post-kinematic sandstone sheets deposited as laterally continuous, subaqueous tidal dune fields. The rate of growth faulting is reflected in the distribution of accommodation, which governs sedimentary architecture and stacking patterns within the coarsening-upward units. Fully compartmentalized basins (12, 200–800 m wide and c. 150 m high grabens and half grabens) are characterized by syn-kinematic sedimentary infill. These grabens and half-grabens are separated by 60–150 m high horsts composed of pro-delta to distal delta-front mudstones. Grabens host tabular tidal dunes (sandwaves), whereas half-grabens bound by listric faults (mainly south-dipping) consist of wedge-shaped, rotated strata with erosive boundaries proximal to the uplifted fault block crests. Heterolithic tidal bars (sand ridges) occur in narrow half-grabens, showing migration oblique to the faults, up the dipslope. Structureless sandstone wedges and localized subaqueous slumps that formed in response to collapse of the block crests were only documented in half-grabens. Late-kinematic deposition during the final stages of faulting occurred in partly compartmentalized basins, filled with variably thick sets of continuous sandstone belts (compound tidal dunes).  相似文献   

The end of the Great Khersonian Drying of Eurasia: Magnetostratigraphic dating of the Maeotian transgression in the Eastern Paratethys     

Dan Valentin Palcu  Iuliana Vasiliev  Marius Stoica  Wout Krijgsman 《Basin Research》2019,31(1):33-58

Central Eurasia underwent significant palaeoclimatic and palaeogeographic transformations during the middle to late Miocene. The open marine ecosystems of the Langhian and Serravallian seas progressively collapsed and were replaced in the Tortonian by large endorheic lakes. These lakes experienced major fluctuations in water level, directly reflecting the palaeoclimatic conditions of the region. An extreme lowstand of the Eastern Paratethys lake (?300 m) during the regional Khersonian stage reveals a period of intensely dry conditions in Central Eurasia causing a fragmentation of the Paratethys region. This period of “Great Drying” ended by a climate change towards more humid conditions at the base of the Maeotian stage, resulting in a large transgressive event that reconnected most of the Paratethyan basins. The absence of a robust time frame for the Khersonian–Maeotian interval hampers a direct correlation with the global records and complicates a thorough understanding of the underlying mechanisms. Here we present a new chronostratigraphic framework for the Khersonian and Maeotian deposits of the Dacian Basin of Romania, based on integrated magneto‐biostratigraphic studies on long and continuous sedimentary successions. We show the dry climate conditions in the Khersonian start at 8.6–8.4 Ma. The Khersonian/Maeotian transition is dated at 7.65–7.5 Ma, several million years younger than previous estimates. The Maeotian transgression occurs later (7.5–7.4 Ma) in more marginal and shallower basins, in agreement with the time transgressive character of the flooding. In addition, we date a sudden water level drop of the Eastern Paratethys lake, the Intra‐Maeotian Event (IME), at 6.9 Ma, and hypothesize that this corresponds to a reconnection phase with the Aegean basin of the Mediterranean. Finally, we discuss the potential mechanisms explaining the particularities of the Maeotian transgression and conclude that the low salinity and the seemingly “marine influxes” most likely correspond to episodes of intrabasinal mixing in a gradual and pulsating transgressive setting.  相似文献   

The Multiscale TROPIcal CatchmentS critical zone observatory M-TROPICS dataset II: Land use,hydrology and sediment production monitoring in Houay Pano,northern Lao PDR     

Laurie Boithias  Yves Auda  Stéphane Audry  Jean-Pierre Bricquet  Alounsavath Chanhphengxay  Vincent Chaplot  Anneke de Rouw  Thierry Henry des Tureaux  Sylvain Huon  Jean-Louis Janeau  Keooudone Latsachack  Yann Le Troquer  Guillaume Lestrelin  Jean-Luc Maeght  Pierre Marchand  Pierre Moreau  Andrew Noble  Anne Pando-Bahuon  Kongkeo Phachomphon  Khambai Phanthavong  Alain Pierret  Olivier Ribolzi  Jean Riotte  Henri Robain  Emma Rochelle-Newall  Saysongkham Sayavong  Oloth Sengtaheuanghoung  Norbert Silvera  Nivong Sipaseuth  Bounsamay Soulileuth  Xaysatith Souliyavongsa  Phapvilay Sounyaphong  Sengkeo Tasaketh  Chanthamousone Thammahacksa  Jean-Pierre Thiebaux  Christian Valentin  Olga Vigiak  Marion Viguier  Khampaseuth Xayyathip 《水文研究》2021,35(5):e14126

Mountain regions of the humid tropics are characterized by steep slopes and heavy rains. These regions are thus prone to both high surface runoff and soil erosion. In Southeast Asia, uplands are also subject to rapid land-use change, predominantly as a result of increased population pressure and market forces. Since 1998, the Houay Pano site, located in northern Lao PDR (19.85°N 102.17°E) within the Mekong basin, aims at assessing the long-term impact of the conversion of traditional slash-and-burn cultivation systems to commercial perennial monocultures such as teak tree plantations, on the catchment hydrological response and sediment yield. The instrumented site monitors hydro-meteorological and soil loss parameters at both microplot (1 m²) and small catchment (0.6 km²) scales. The monitored catchment is part of the network of critical zone observatories named Multiscale TROPIcal CatchmentS (M-TROPICS). The data shared by M-TROPICS in Houay Pano are (1) rainfall, (2) air temperature, air relative humidity, wind speed, and global radiation, (3) catchment land use, (4) stream water level, suspended particulate matter, bed particulate matter and stones, (5) soil surface features, and (6) soil surface runoff and soil detachment. The dataset has already been used to interpret suspended particulate matter and bed particulate matter sources and dynamics, to assess the impact of land-use change on catchment hydrology, soil erosion, and sediment yields, to understand bacteria fate and weed seed transport across the catchment, and to build catchment-scale models focused on hydrology and water quality issues. The dataset may be further used to, for example, assess the role of headwater catchments in large tropical river basin hydrology, support the interpretation of new variables measured in the catchment (e.g., contaminants other than faecal bacteria), and assess the relative impacts of both climate and land-use change on the catchment.  相似文献   

Exhumation of eclogite and blueschist (Cyclades,Greece): Pressure–temperature evolution determined by thermobarometry and garnet equilibrium modelling          下载免费PDF全文

Valentin Laurent  Pierre Lanari  Inès Naïr  Romain Augier  Abdeltif Lahfid  Laurent Jolivet 《Journal of Metamorphic Geology》2018,36(6):769-798

High‐P rocks such as eclogite and blueschist are metamorphic markers of palaeo‐subduction zones, and their formation at high‐P and low‐T (HP–LT) conditions is relatively well understood since it has been the focus of numerous petrological investigations in the past 40 years. The tectonic mechanisms controlling their exhumation back to the surface are, however, diverse, complex and still actively debated. Although the Cycladic Blueschist Unit (CBU, Greece) is among the best worldwide examples for the preservation of eclogite and blueschist, the proposed P–T evolution followed by this unit within the Hellenic subduction zone is quite different from one study to another, hindering the comprehension of exhumation processes. In this study, we present an extensive petrological data set that permits refinement of the shape of the P–T trajectory for different subunits of the CBU on Syros. High‐resolution quantitative compositional mapping has been applied to support the thermobarometric investigations, which involve semi‐empirical thermobarometry, garnet equilibrium modelling and P–T isochemical phase diagrams. The thermodynamic models highlight the powerful use of reactive bulk compositions approximated from local bulk compositions. The results are also combined with Raman spectrometry of carbonaceous material (RSCM) to retrieve the metamorphic peak temperature distribution at the scale of the island. A major result of this study is the good agreement between all the independent thermobarometric methods, permitting reconstruction of the prograde and retrograde P–T trajectories. Garnet compositional zoning was used to retrieve prograde, peak and retrograde growth stages in line with the results of the P–T isochemical phase diagrams, RSCM temperature and peak‐pressure crystallization of the garnet–omphacite–phengite assemblage. Our results are consistent with previous thermobarometric estimates from other occurrences of CBU rocks (Tinos, Andros), suggesting a multistage exhumation process with (1) early syn‐orogenic exhumation within the subduction channel, (2) isobaric heating at mid‐crustal depths (~10–12 kbar) following thermal re‐equilibration of the lithosphere from a cold syn‐orogenic regime in the subduction zone to a warmer post‐orogenic regime in the back‐arc domain and (3) exhumation and cooling related to a post‐orogenic phase of extension following slab retreat. Expanding to the general aspects of subduction zones, we suggest that such metamorphic evolution of HP–LT units should be regarded as a characteristic feature of exhumation driven by slab rollback.  相似文献   

Sorption behavior of the sandy residual unconsolidated materials from the sandstones of the Botucatu Formation,the main aquifer of Brazil     

Junio René Toledo Fagundes  Lázaro Valentin Zuquette 《Environmental Earth Sciences》2011,62(4):831-845

Pollutant transport through porous geological materials depends on the intrinsic characteristics of the materials that define the sorption behavior. This is the main environmental aspect that must be evaluated in terms of natural attenuation and retardation factor of the pollutants. Sorption is directly related to the electrostatic charge of the mineral, the organic matter, and the oxide and hydroxide contents. We assessed the sorption characteristics of the sandy residual unconsolidated material of the Botucatu Formation, which is part of the main aquifer of Brazil, using Batch Equilibrium Tests. The tests used multicomponent solutions of NaCl, KCl, ZnCl₂, and CuCl₂·H₂O with a total concentration that varied from 20 to 1,000 ppm. Different plotting systems were applied so that the isotherms better reflected the sorption behavior of the studied cations onto the unconsolidated materials. The cation Na⁺ was not sorbed. The Langmuir I and Freundlich equations adequately represent the behavior of Cu⁺⁺, the Langmuir II approximation better represented K⁺, and the Langmuir I and Freundlich equations were reasonably fitted Zn⁺⁺.  相似文献   

Textural history of recent basaltic-andesites and plutonic inclusions from Merapi volcano   总被引：1，自引：1，他引：0  

Froukje M. van der Zwan  Jane P. Chadwick  Valentin R. Troll 《Contributions to Mineralogy and Petrology》2013,166(1):43-63

Mt. Merapi in Central Java is one of the most active stratovolcanoes on Earth and is underlain by a multistage plumbing system. Crystal size distribution analyses (CSD) were carried out on recent Merapi basaltic-andesites and co-eruptive magmatic and plutonic inclusions to characterise the crystallisation processes that operate during storage and ascent and to obtain information on respective time scales. The basaltic-andesites exhibit log-linear, kinked-upwards CSD curves for plagioclase and clinopyroxene that can be separated into two main textural populations. Large plagioclase phenocrysts (≥1.6 mm) make up one population, but correspond to crystals with variable geochemical composition and reflect a period of crystal growth at deep to mid-crustal levels. This population was subsequently influenced by crystal accumulation and the onset of crustal assimilation, including the incorporation of high-Ca skarn-derived xenocrysts. Textural re-equilibration is required for these crystals to form a single population in CSD. A second episode of crystal growth at shallower levels is represented by chemically homogenous plagioclase crystals <1.6 mm in size. Crustal assimilation is indicated by, for example, oxygen isotopes and based on the CSD data, crystallisation combined with contamination is likely semi-continuous in these upper crustal storage chambers. The CSD data observed in the basaltic-andesite samples are remarkably consistent and require a large-volume steady state magmatic system beneath Merapi in which late textural equilibration plays a significant role. Plagioclase CSDs of co-eruptive magmatic and plutonic inclusions may contain a third crystal population (<1 mm) not found in the lavas. This third population has probably formed from enhanced degassing of portions of basaltic-andesite magma at shallow crustal levels which resulted in increased crystallinity and basaltic-andesite mush inclusions. A suite of coarse plutonic inclusions is also present that reflects crystallisation and accumulation of crystals in the deep Merapi plumbing system, as deduced from CSD patterns and mineral assemblages.  相似文献   

Sources of δ18O Concentration Variability in Greenland Ice Cores: Temperature, North Atlantic Oscillation and Solar Activity     

Valentin A. Dergachev  Sergey S. Vasiliev 《Solar physics》2004,224(1-2):433-443

This work concerns possible connection between variations of δ¹⁸O in Greenland ice, temperature, precipitation amount, NAO indices and relative sunspot numbers. The relationships between 10-year averaged values of this data were derived making use of regression analysis methods. It was discovered that February temperature yields the main contribution in variability of δ¹⁸O. The multiple correlation coefficient between weighted night temperature of the most important months and δ¹⁸O equals 0.95±0.01. Besides the local source of δ¹⁸O changes, defined by the amount of precipitation and temperature, an additional source correlated with the level of solar activity has been revealed. The relative contribution of this source in the δ¹⁸O variance is about 0.1. It has been shown that the multiple correlation coefficient between δ¹⁸O and NAO indices is equal to 0.85. Therefore the NAO yields more than 2/3 of the variances of climatic change in Greenland. An independent contribution of solar activity in climatic changes is about 1/3.  相似文献   

Numerical Investigation of Seismically Induced Rock Mass Fatigue as a Mechanism Contributing to the Progressive Failure of Deep-Seated Landslides     

Valentin Gischig  Giona Preisig  Erik Eberhardt 《Rock Mechanics and Rock Engineering》2016,49(6):2457-2478

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Structure and U–Pb zircon geochronology of an Alpine nappe stack telescoped by extensional detachment faulting (Kulidzhik area,Eastern Rhodopes,Bulgaria)     

Neven Georgiev  Nikolaus Froitzheim  Zlatka Cherneva  Dirk Frei  Valentin Grozdev  Silke Jahn-Awe  Thorsten J. Nagel 《International Journal of Earth Sciences》2016,105(7):1985-2012

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Review of the experience with monitoring uncertainty requirements in the Clean Development Mechanism     

Igor Shishlov  Valentin Bellassen 《Climate Policy》2016,16(6):703-731

In order to ensure the environmental integrity of carbon offset projects, emission reductions certified under the Clean Development Mechanism (CDM) have to be ‘real, measurable and additional’, which is ensured, inter alia, through the monitoring, reporting and verification (MRV) process. MRV, however, comes at a cost that ranges from several cents to €1.20 and above per tCO₂e depending on the project type. This article analyses monitoring uncertainty requirements for carbon offset projects with a particular focus on the trade-off between monitoring stringency and cost. To this end, existing literature is reviewed, overarching monitoring guidelines, as well as the ten most-used methodologies are scrutinized, and finally three case studies are analysed. It is shown that there is indeed a trade-off between the stringency and the cost of monitoring, which if not addressed properly may become a major barrier for the implementation of offset projects in some sectors. It is then demonstrated that this trade-off has not been systematically addressed in the overarching CDM guidelines and that there are only limited incentives to reduce monitoring uncertainty. Some methodologies and calculation tools as well as some other offset standards, however, do incorporate provisions for a trade-off between monitoring costs and stringency. These provisions may take the form of discounting emissions reductions based on the level of monitoring uncertainty – or more implicitly through allowing a project developer to choose between monitoring a given parameter and using a conservative default value.

Policy relevance

The CDM Executive Board acknowledged that monitoring uncertainty has not been treated in a consistent manner and the draft standard on uncertainty was subsequently presented in May 2013. This article supports the implementation of this standard for more comprehensive, yet cost-efficient accounting for monitoring uncertainty in carbon offset projects. Moreover, in the light of the ongoing discussions on the New Market Mechanisms as well as the operationalization of the Green Climate Fund and different national mitigation policies, the CDM experience provides valuable insights with regards to the treatment of monitoring uncertainty and constitutes a solid basis for designing uncertainty requirements for new mechanisms to mitigate climate change.  相似文献