Petroleum source rocks of the Tarfaya Basin and adjacent areas, Morocco     

Victoria F. Sachse  Ralf Littke  Sabine Heim  Oliver Kluth  Jürgen Schober  Lahcen Boutib  Haddou Jabour  Ferdinand Perssen  Sven Sindern 《Organic Geochemistry》2011,42(3):209-227

This work characterizes the source rock potential of the Tarfaya Basin and enabled us to reconstruct its geochemical history. Outcrop samples covering different stratigraphic intervals, plus the northwestern part of the Zag/Tindouf Basin (Bas Draa area), were analyzed for total organic carbon (C_org) and total inorganic carbon contents and total sulfur content. Rock-Eval analysis and vitrinite reflectance measurements were performed on 56 samples chosen on the basis C_org content. A set of 45 samples were extracted and non-aromatic hydrocarbons were analyzed by way of gas chromatography-flame ionization detection (GC-FID) and GC-mass spectrometry (GC-MS). Non-isothermal open system pyrolysis at different heating rates was applied to obtain kinetic parameters for modelling petroleum generation from four different source rocks.High quality petroleum source rocks with high C_org content and hydrogen index (HI) values were found for samples of Eocene, Coniacian, Turonian and Cenomanian age. Most samples were carbonate rich and organic/sulfur values were high to moderate. Various maturity parameters indicated immature or possibly early mature organic matter. Based on organic geochemical and petrological data, the organic matter is of marine/aquatic origin (Cenomanian) or a mixture of aquatic and terrigenous material (Eocene). The Early Cretaceous interval did not contain high quality source rocks, but indications of petroleum impregnation were found.  相似文献   

Future seagrass beds: Can increased productivity lead to increased carbon storage?     

Bayden D. Russell  Sean D. Connell  Sven Uthicke  Nancy Muehllehner  Katharina E. Fabricius  Jason M. Hall-Spencer 《Marine pollution bulletin》2013

While carbon capture and storage (CCS) is increasingly recognised as technologically possible, recent evidence from deep-sea CCS activities suggests that leakage from reservoirs may result in highly CO₂ impacted biological communities. In contrast, shallow marine waters have higher primary productivity which may partially mitigate this leakage. We used natural CO₂ seeps in shallow marine waters to assess if increased benthic primary productivity could capture and store CO₂ leakage in areas targeted for CCS. We found that the productivity of seagrass communities (in situ, using natural CO₂ seeps) and two individual species (ex situ, Cymodocea serrulata and Halophila ovalis) increased with CO₂ concentration, but only species with dense belowground biomass increased in abundance (e.g. C. serrulata). Importantly, the ratio of below:above ground biomass of seagrass communities increased fivefold, making seagrass good candidates to partially mitigate CO₂ leakage from sub-seabed reservoirs, since they form carbon sinks that can be buried for millennia.  相似文献   

Causal thinking and support for climate change policies: International survey findings     

Ann Bostrom  Robert E. O’Connor  Gisela Böhm  Daniel Hanss  Otto Bodi  Frida Ekström  Pradipta Halder  Sven Jeschke  Birgit Mack  Mei Qu  Lynn Rosentrater  Anethe Sandve  Ingrid Sælensminde 《Global Environmental Change》2012,22(1):210-222

Few comparative international studies describe the climate change policies people are willing to support and the reasons for their support of different policies. Using survey data from 664 economics and business undergraduates in Austria, Bangladesh, Finland, Germany, Norway, and the United States, we explore how perceived risk characteristics and mental models of climate change influence support for policy alternatives. General green policies such as funding research on renewable technologies and planting trees were the overwhelmingly most popular policy alternatives. Around half the students support carbon reduction policies such as requiring higher car fuel efficiency and increasing taxes on fossil fuels. Least popular were engineering alternatives such as fertilizing the oceans and replacing fossil fuels with nuclear power. Variations among nations are generally small. Support for different policy alternatives corresponds with different causal thinking. Those who hold a pollution model of the causes of climate change, tend to blame environmental harms (e.g., air pollution from toxic chemicals), see general green policy alternatives as effective, and support general green policies. Support of carbon reduction strategies is associated with seeing carbon emissions as the cause and reducing carbon emissions as effective solutions. Support of engineering solutions increases with identifying volcanoes among causes and regarding engineering solutions as effective. Although these international students agree that climate change is a threatening problem, their causal thinking correlates with support for different mitigative policy actions, with the most popular ones not necessarily the most effective.  相似文献   

Discussion: a critique of Possible waterways between the Marmara Sea and the Black Sea in the late Quaternary: evidence from ostracod and foraminifer assemblages in lakes ?znik and Sapanca, Turkey, Geo-Marine Letters, 2011     

Cenk Yalt?rak  Umut B. ülgen  Cengiz Zabc?  Sven Oliver Franz  Sena Ak?er ?n  Mehmet Sak?n?  M. Nam?k ?a?atay  Bedri Alpar  Kurultay ?ztürk  Cemal Tuno?lu  Selma ünlü 《Geo-Marine Letters》2012,32(3):267-274

The identification of past connection routes between the Black Sea and the Sea of Marmara, other than the traditional one through to the Bosphorus Strait, would be of considerable interest to the international scientific community. Nazik et al. (Geo-Mar Lett 31:75?C86 (2011) doi:10.1007/s00367-010-0216-9) suggest the possibility of two alternative waterway connections via lakes Sapanca and ?znik. Their Black Sea to Sea of Marmara multi-connection hypothesis, which is based on undated marine fossils collected in both lakes from surficial grab samples, conflicts with many earlier studies. In this contribution, the hypothesis and the underlying data are discussed in the light of previous tectonic, sedimentological and limnological findings showing that it is impossible to have had marine connections through lakes Sapanca and ?znik during the last 11.5?ka. Global sea-level trends and tectonic uplift rates would accommodate a connection between the Sea of Marmara and Lake ?znik in the middle Pleistocene. Uplift rates for the northern block of the North Anatolian Fault, when compared with the global sea-level curve, clearly indicate that there cannot have been a connection through the ?zmit Gulf?CLake Sapanca?CSakarya Valley for at least the past 500?ka. Moreover, borehole sediments along the western shores of Lake Sapanca, which reach down to the bedrock, do not contain any marine fossils.  相似文献   

Dynamic adjustment of training sets (‘moving-window’ reconstruction) by using transfer functions in paleolimnology—a new approach   总被引：1，自引：0，他引：1  

Thomas Hübener  Mirko Dreßler  Anja Schwarz  Kirsten Langner  Sven Adler 《Journal of Paleolimnology》2008,40(1):79-95

This paper presents a new method (moving-windows) that optimizes diatom-based paleolimnological reconstructions of past environmental conditions from supra-regional training sets. The moving-window method identifies the best number of nearest neighbours (window size) from a merged supra-regional EDDI and local (MV) training set (n = 429) for each fossil diatom assemblage and the best type of transfer function (ML, WA-PLS) based on the error statistic of each transfer function (highest cross-validated R ², lowest cross-validated average bias, maximum bias and RMSEP). At first we evaluated the moving-window approach by comparing measured TP-values with inferred TP-values using both the moving-window approach and the WA-PLS method. The relative errors of the moving-window approach were not significantly different for 208 samples that had an error <15 μg/l TP using the WA-PLS method. However, for the remaining 221 samples with errors >>15 μg/l TP using the WA-PLS method, the moving window approach significantly reduced the relative error of the inferred TP levels. Secondly, the moving- window approach was used to reconstruct epilimnetic total phosphorous (TP) for Lake Dudinghausen, Lake Rugensee, Lake Tiefer See and Lake Drewitzer See (Northern Germany) using both the supra-regional EDDI training set and a local training set from Northern Germany (MV training set). The moving-window inferred TP-levels of the four study lakes were compared with published reconstructed TP-values and with inferred TP-values based on the local MV training set. Overall, the moving-window and the published TP-trends agree well with each other. However, the moving-window reconstructions generally indicated lower TP-levels throughout the past ∼5,000 to 12,000 years, including past maxima. Thus, the moving-window method seems to generate more realistic absolute TP levels due to the optimized window size (highest number of modern analogues, best error statistics). The identification of more realistic absolute historic TP-values is important for the validation of reference conditions for inland waters. This study also demonstrates that a robust local training set may, similar to moving-window training sets, also lead to reliable reconstructions, if the geological settings of the local training set lakes and the study lakes are similar.  相似文献   

Symbiont-specific responses in foraminifera to the herbicide diuron     

van Dam JW  Negri AP  Mueller JF  Uthicke S 《Marine pollution bulletin》2012,65(4-9):373-383

The effects of the photosystem II (PSII) herbicide diuron was assessed on thirteen tropical foraminifera hosting diatom, dinoflagellate, red or green algae endosymbionts. Inhibition of photosynthesis (reduced ΔF/F(m)(')) by diuron depended on both symbiont type and test ultrastructure, with greatest sensitivity observed for diatom- and chlorophyte-hosting species (24h IC(25) 2.5-4μg L(-1)). Inhibition kinetics was slow (24-48h until maximum inhibition) in comparison with corals, suggesting structural differences may influence herbicide uptake and transport. Although foraminifera were generally less sensitive to direct effects of diuron (inhibition ΔF/F(m)(')) than other marine phototrophs, damage to PSII (reduction F(v)/F(m)) occurred at concentrations lower than observed for other organisms (24h IC(25) 3-12μg L(-1)). Damage to PSII was highly light dependent and occurred at very low light intensities indicating limited photoprotective capacity. The high diversity, widespread occurrence and relative sensitivity make foraminifera good bioindicator organisms to evaluate phytotoxic stress on coral reefs.  相似文献   

GT-57633 catalogue of Martian impact craters developed for evaluation of crater detection algorithms     

Goran Salamuni?car  Sven Lon?ari? 《Planetary and Space Science》2008,56(15):1992-2008

Crater detection algorithms (CDAs) are an important subject of the recent scientific research. A ground truth (GT) catalogue, which contains the locations and sizes of known craters, is important for the evaluation of CDAs in a wide range of CDA applications. Unfortunately, previous catalogues of craters by other authors cannot be easily used as GT. In this paper, we propose a method for integration of several existing catalogues to obtain a new craters catalogue. The methods developed and used during this work on the GT catalogue are: (1) initial screening of used catalogues; (2) evaluation of self-consistency of used catalogues; (3) initial registration from three different catalogues; (4) cross-evaluation of used catalogues; (5) additional registrations and registrations from additional catalogues; and (6) fine-tuning and registration with additional data-sets. During this process, all craters from all major currently available manually assembled catalogues were processed, including catalogues by Barlow, Rodionova, Boyce, Kuzmin, and our previous work. Each crater from the GT catalogue contains references to crater(s) that are used for its registration. This provides direct access to all properties assigned to craters from the used catalogues, which can be of interest even to those scientists that are not directly interested in CDAs. Having all these craters in a single catalogue also provides a good starting point for searching for craters still not catalogued manually, which is also expected to be one of the challenges of CDAs. The resulting new GT catalogue contains 57,633 craters, significantly more than any previous catalogue. From this point of view, GT-57633 catalogue is currently the most complete catalogue of large Martian impact craters. Additionally, each crater from the resulting GT-57633 catalogue is aligned with MOLA topography and, during the final review phase, additionally registered/aligned with 1/256° THEMIS-DIR, 1/256° MDIM and 1/256° MOC data-sets. Accordingly, the resulting GT-57633 catalogue can successfully be used as a part of the framework for evaluation of CDAs.  相似文献   

Statistical downscaling of daily precipitation over Sweden using GCM output   总被引：3，自引：2，他引：1  

Fredrik Wetterhall  András Bárdossy  Deliang Chen  Sven Halldin  Chong-yu Xu 《Theoretical and Applied Climatology》2009,96(1-2):95-103

A classification of Swedish weather patterns (SWP) was developed by applying a multi-objective fuzzy-rule-based classification method (MOFRBC) to large-scale-circulation predictors in the context of statistical downscaling of daily precipitation at the station level. The predictor data was mean sea level pressure (MSLP) and geopotential heights at 850 (H850) and 700 hPa (H700) from the NCEP/NCAR reanalysis and from the HadAM3 GCM. The MOFRBC was used to evaluate effects of two future climate scenarios (A2 and B2) on precipitation patterns on two regions in south-central and northern Sweden. The precipitation series were generated with a stochastic, autoregressive model conditioned on SWP. H850 was found to be the optimum predictor for SWP, and SWP could be used instead of local classifications with little information lost. The results in the climate projection indicated an increase in maximum 5-day precipitation and precipitation amount on a wet day for the scenarios A2 and B2 for the period 2070–2100 compared to 1961–1990. The relative increase was largest in the northern region and could be attributed to an increase in the specific humidity rather than to changes in the circulation patterns.  相似文献   

Modelling Hydrological Consequences of Climate Change—— Progress and Challenges   总被引：8，自引：1，他引：7  

Chong-yu XU  Elin WID 《大气科学进展》2005,22(6):789-797

The simulation of hydrological consequences of climate change has received increasing attention from the hydrology and land-surface modelling communities. There have been many studies of climate-change effects on hydrology and water resources which usually consist of three steps： （1） use of general circulation models （GCMs） to provide future global climate scenarios under the effect of increasing greenhouse gases, （2） use of downscaling techniques （both nested regional climate models, RCMs, and statistical methods） for ＂downscaling＂ the GCM output to the scales compatible with hydrological models, and （3） use of hydrologic models to simulate the effects of climate change on hydrological regimes at various scales. Great progress has been achieved in all three steps during the past few years, however, large uncertainties still exist in every stage of such study. This paper first reviews the present achievements in this field and then discusses the challenges for future studies of the hydrological impacts of climate change.  相似文献   

Acropora coral colonies as microhabitats for sponges in Tayrona National Natural Park,Colombian Caribbean          下载免费PDF全文

Eliana M. Pineda‐Munive  Rocío del P. García‐Urueña  Sven Zea 《Marine Ecology》2017,38(1)

Sponges are sessile organisms capable of colonizing diverse substrata. In the Caribbean, coral reefs have suffered a drastic decline, and branching corals of the genus Acropora have been widely decimated. On dead coral skeletons and around surviving tissue the settling of sessile organisms can be observed, sponges being common. In order to investigate whether or not sponges have a preference for a particular species of coral, or for specific microhabitats of the colonies, we evaluated species composition, cover, richness and diversity of sponges colonizing the dead parts of still live colonies of the branching corals Acropora palmata and Acropora cervicornis in five locations of the Tayrona National Natural Park in the Colombian Caribbean. Ten colonies of Ac. palmata were quantified in each of the five locations, and eight Ac. cervicornis colonies in each of two locations. Quantification was carried out using video taken within 0.625‐m² photoquadrats. Seventeen sponge species were found, 13 of them associated with Ac. palmata and seven with Ac. cervicornis. Desmapsamma anchorata, Clathria venosa and Scopalina rutzleri were found to be common to all Ac. palmata locations, while De. anchorata occurred in the two Ac. cervicornis locations. On Ac. palmata, encrusting sponges dominated, while on Ac. cervicornis branched and lobed sponges predominated. Significant differences in sponge cover were not found among locations but were observed in the sponge species present. On Ac. palmata the species with highest cover were D. anchorata and Cla. venosa, while on Ac. cervicornis it was De. anchorata. The richness and diversity of sponges were low for both coral species, and their varying distribution can be attributed to the differences in available substrate for attachment, given coral colony morphology; for Ac. palmata, sponges predominated on the underside of the branches, semi‐cryptic areas and colony bases, whereas for Ac. cervicornis, they were located over the entire area of the cylindrical branches. Surviving colonies of Ac. palmata and Ac. cervicornis that are still erect offer additional microhabitats for reef sponges, some of which can be found directly interacting with live coral tissue, further threatening their recovery.  相似文献