Lithostratigraphic units of the Helvetic Palaeogene: review,new definition,new classification     

Ursula Menkveld-Gfeller  Oliver Kempf  Hanspeter Funk 《Swiss Journal of Geoscience》2016,109(2):171-199

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Targeting carbon dioxide removal in the European Union     

Oliver Geden  Glen P. Peters  Vivian Scott 《Climate Policy》2019,19(4):487-494

In principle, many climate policymakers have accepted that large-scale carbon dioxide removal (CDR) is necessary to meet the Paris Agreement’s mitigation targets, but they have avoided proposing by whom CDR might be delivered. Given its role in international climate policy, the European Union (EU) might be expected to lead the way. But among EU climate policymakers so far there is little talk on CDR, let alone action. Here we assess how best to ‘target’ CDR to motivate EU policymakers exploring which CDR target strategy may work best to start dealing with CDR on a meaningful scale. A comprehensive CDR approach would focus on delivering the CDR volumes required from the EU by 2100, approximately at least 50 Gigatonnes (Gt) CO₂, according to global model simulations aiming to keep warming below 2°C. A limited CDR approach would focus on an intermediate target to deliver the CDR needed to reach ‘net zero emissions’ (i.e. the gross negative emissions needed to offset residual positive emissions that are too expensive or even impossible to mitigate). We argue that a comprehensive CDR approach may be too intimidating for EU policymakers. A limited CDR approach that only addresses the necessary steps to reach the (intermediate) target of ‘net zero emissions’ is arguably more achievable, since it is a better match to the existing policy paradigm and would allow for a pragmatic phase-in of CDR while avoiding outright resistance by environmental NGOs and the broader public.

Key policy insights

• Making CDR an integral part of EU climate policy has the potential to significantly reshape the policy landscape.

• Burden sharing considerations would probably play a major role, with comprehensive CDR prolonging the disparity and tensions between progressives and laggards.

• Introducing limited CDR in the context of ‘net zero’ pathways would retain a visible primary focus on decarbonization but acknowledge the need for a significant enhancement of removals via ‘natural’ and/or ‘engineered’ sinks.

• A decarbonization approach that intends to lead to a low level of ‘residual emissions’ (to be tackled by a pragmatic phase-in of CDR) should be the priority of EU climate policy.

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Thermal evolution of the central Halls Creek Orogen,northern Australia     

S. Bodorkos  N. H. S. Oliver  P. A. Cawood 《Australian Journal of Earth Sciences》2013,60(3):453-465

The Halls Creek Orogen in northern Australia records the Palaeoproterozoic collision of the Kimberley Craton with the North Australian Craton. Integrated structural, metamorphic and geochronological studies of the Tickalara Metamorphics show that this involved a protracted episode of high‐temperature, low‐pressure metamorphism associated with intense and prolonged mafic and felsic intrusive activity in the interval ca 1850–1820 Ma. Tectonothermal development of the region commenced with an inferred mantle perturbation event, probably at ca 1880 Ma. This resulted in the generation of mafic magmas in the upper mantle or lower crust, while upper crustal extension preceded the rapid deposition of the Tickalara sedimentary protoliths. An older age limit for these rocks is provided by a psammopelitic gneiss from the Tickalara Metamorphics, which yield a ²⁰⁷Pb/²⁰⁶Pb SHRIMP age of 1867 ± 4 Ma for the youngest detrital zircon suite. Voluminous layered mafic intrusives were emplaced in the middle crust at ca 1860–1855 Ma, prior to the attainment of lower granulite facies peak metamorphic conditions in the middle crust. Locally preserved layer‐parallel D₁ foliations that were developed during prograde metamorphism were pervasively overprinted by the dominant regional S₂ gneissosity coincident with peak metamorphism. Overgrowths on zircons record a metamorphic ²⁰⁷Pb/²⁰⁶Pb age of 1845 ± 4 Ma. The S₂ fabric is folded around tight folds and cut by ductile shear zones associated with D₃ (ca 1830 Ma), and all pre‐existing structures are folded around large‐scale, open F₄ folds (ca 1820 Ma). Construction of a temperature‐time path for the mid‐crustal section exposed in the central Halls Creek Orogen, based on detailed SHRIMP zircon data, key field relationships and petrological evidence, suggests the existence of one protracted thermal event (>400–500°C for 25–30 million years) encompassing two deformation phases. Protoliths to the Tickalara Metamorphics were relatively cold (～350°C) when intruded by the Fletcher Creek Granite at ca 1850 Ma, but were subsequently heated rapidly to 700–800°C during peak metamorphism at ca 1845 Ma. Repeated injection of mafic magmas caused multiple remelting of the metasedimentary wall rocks, with mappable increases in leucosome volume that show a strong spatial relationship to these intrusives. This mafic igneous activity prolonged the elevated geotherm and ensured that the rocks remained very hot (≥650°C) for at least 10 million years. The Mabel Downs Tonalite was emplaced during amphibolite facies metamorphism, with intrusion commencing at ca 1835 Ma. Its compositional heterogeneity, and the presence of mutual cross‐cutting relations between ductile shear zones and multiple injections of mingled magma suggest that it was emplaced syn‐D₃. Broad‐scale folding attributable to F₄ was accompanied by widespread intrusion of granitoids, and F₄ fold limbs are truncated by large, mostly brittle retrograde S₄ shear zones.  相似文献   

Planform of convection with strongly temperature-dependent viscosity     

D. S. Oliver  J. R. Booker 《地球物理与天体物理流体动力学》2013,107(1-2):73-85

Abstract

This paper experimentally investigates the convective planform near critical in a fluid layer whose temperature-dependent viscosity varies from top to bottom by up to a factor of 1500. Convection occurs in three different planforms: rolls, hexagons and squares. The square planform, which appears only for fluids with viscosity variation greater than about 50, replaces the hexagonal convection pattern as the Rayleigh number increases much above critical. The large amplitude of hexagonal convection with strong viscosity variation precludes studying the hexagon-square transition with perturbation methods of the type used to study the hexagon-roll transitions at smaller viscosity variations.  相似文献   

Evaluation of magmatic processes for the products of the Nevado del Ruiz Volcano, Colombia from geochemical and petrological data     

Nicole Vatin-Prignon  Pierre Goemans  Richard A. Oliver  Eduardo Parra Palacio 《Journal of Volcanology and Geothermal Research》1990,41(1-4)

Trace-element concentrations of the eruptive products from the Nevado del Ruiz volcano indicate that at least for the last 1 Ma, the major controlling factor in the evolution of the magma has been a simple fractional crystallization.The Zr/Hf ratios suggest that the source material is mantle-like in origin and whilst subduction-related contamination of the source material has taken place, there is no evidence that assimilation of continental crust has affected the series.No convincing geochemical evidence for magma mixing was found, and data on banded pumices of Pleistocene, Historic and the 1985 eruptions strongly support a crystal fractionation model to explain the compositional variation of their glasses. Therefore, if mixing has taken place it can only be a mixing of layers within a stratified or partially stratified magma chamber.Modeling of fractional crystallization using a stepwise program has been undertaken and least-squares approximations with small residuals are commensurate with analyzed samples. Crystal fractionation models with plagioclase dominating two-pyroxenes and iron oxides give good fits for all calculations. We conclude that simple crystal fractionation is the process most consistent with major- and trace-element variations in the Ruiz series. This closed-system model requires at least 77% crystal fractionation of a basaltic parent to generate the observed compositions of dacites.  相似文献   

Total nitrogen content of deep sea basalts     

Thomas L. Norris  Oliver A. Schaeffer 《Geochimica et cosmochimica acta》1982,46(3):371-379

Various models have been suggested concerning the origin and evolution of the earth's atmosphere. An estimate of the nitrogen content of the mantle could further constrain atmospheric models. Total nitrogen content was determined by thermal neutron activation analysis via ¹⁴N(n,p)¹⁴C. The ¹⁴C was converted to carbon dioxide and counted in miniature low level proportional counters. The total nitrogen content of U.S.G.S. standards BCR-1 and G-2 as determined by different laboratories is variable, probably due to atmospheric adsorption by the finely ground samples. Total nitrogen content was determined in deep sea basalt glasses from three regions: East Pacific Rise ($\text{15 ± 4, 18 ± 4}$, and $\text{7 ±}\text{ppm}\text{2 N}$), Mid-Atlantic Rift (FAMOUS Region:$\text{22 ± 5, 18 ± 3}$, and $\text{10 ± 2}\text{ppm}\text{N}$) and the Juan de Fuca Ridge ($\text{17 ± 4}\text{ppm}\text{N}$). Matrix material from the same samples as the glasses was available from the East Pacific Rise ($\text{37 ± 6, 26 ± 4}$, and $\text{34 ± 6}\text{ppm}\text{N}$) and the Mid-Atlantic Rift ($\text{39 ± 4}\text{ppm}\text{N}$) which are about 50 to 100% greater than the associated glasses. The increased matrix abundance may be due to incorporation of chemically bound nitrogen from sea water rather than dissolved molecular nitrogen. The nitrogen content of the FAMOUS samples are inconsistent with the model of Langmuir et al. (1977) for petrogenesis based on trace element data. Factors which can affect the observed nitrogen content in the basalts and the interpretation in terms of the mantle nitrogen abundance are discussed (e.g. partial melting and degassing of the basalts). A lower limit of about 2 ppm N in the mantle can be estimated.  相似文献   

The contribution of humic substances to the acidity of colored natural waters   总被引：1，自引：0，他引：1  

Barry G. Oliver  Earl M. Thurman  Ronald L. Malcolm 《Geochimica et cosmochimica acta》1983,47(11):2031-2035

An operationally defined carboxyl content of humic substances extracted from rivers, streams, lakes, wetlands, and groundwaters throughout the United States and Canada is reported. Despite the diversity of the samples, only small variations were observed in this humic carboxyl content. The dissociation behavior of two combined fulvic/humic acid extracts was studied and it was found that the dissociation of the humics varied in a predictable manner with pH. Using a carboxyl content of 10 μeq/ mg humic organic carbon, and mass action quotient calculated from sample pH, the ionic balances of three highly colored Nova Scotia rivers were estimated.  相似文献   

A three-dimensional geophysical model of the crust in the Barents Sea region: model construction and basement characterization   总被引：2，自引：0，他引：2  

Oliver Ritzmann  Nils Maercklin  Jan Inge Faleide  Hilmar Bungum  Walter D. Mooney  Shane T. Detweiler 《Geophysical Journal International》2007,170(1):417-435

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Two-dimensional modelling of some CFC replacement compounds     

Oliver Wild  Oliver V. Rattigan  Roderic L. Jones  John A. Pyle  R. Anthony Cox 《Journal of Atmospheric Chemistry》1996,25(2):167-199

The Cambridge 2-D Eulerian model has been used to study the potential atmospheric distributions and lifetimes of a number of CFC replacement compounds and their degradation products. The study has focused on HFC 134a and HCFCs 123, 141b and 142b and the major products formed by their atmospheric degradation. The loss of these compounds and their products by hydroxyl radical attack, photolysis and in-cloud hydrolysis have been investigated. The study has shown that HCFCs 141b and 142b have sufficiently long lifetimes to enter the stratosphere in significant quantities, where degradation leads to an increase in the total stratospheric chlorine concentration. The study has also highlighted areas where further experimental work would be valuable, in particular characterisation of the product channels for the degradation reactions and determination of the removal rates of the products in the aqueous phase.  相似文献   

Stochastic perturbation analysis of groundwater flow. Spatially variable soils,semi-infinite domains and large fluctuations     

G. Christakos  C. T. Miller  D. Oliver 《Stochastic Environmental Research and Risk Assessment (SERRA)》1993,7(3):213-239

As is well known, a complete stochastic solution of the stochastic differential equation governing saturated groundwater flow leads to an infinite hierarchy of equations in terms of higher-order moments. Perturbation techniques are commonly used to close this hierarchy, using power-series expansions. These methods are applied by truncating the series after a finite number of terms, and products of random gradients of conductivity and head potential are neglected. Uncertainty regarding the number or terms required to yield a sufficiently accurate result is a significant drawback with the application of power series-based perturbation methods for such problems. Low-order series truncation may be incapable of representing fundamental characteristics of flow and can lead to physically unreasonable and inaccurate solutions of the stochastic flow equation. To support this argument, one-dimensional, steady-state, saturated groundwater flow is examined, for the case of a spatially distributed hydraulic conductivity field. An ordinary power-series perturbation method is used to approximate the mean head, using second-order statistics to characterize the conductivity field. Then an interactive perturbation approach is introduced, which yields improved results compared to low-order, power-series perturbation methods for situations where strong interactions exist between terms in such approximations. The interactive perturbation concept is further developed using Feynman-type diagrams and graph theory, which reduce the original stochastic flow problem to a closed set of equations for the mean and the covariance functions. Both theoretical and practical advantages of diagrammatic solutions are discussed; these include the study of bounded domains and large fluctuations.  相似文献