Petrophysical characterization of the South Georgia Rift Basin for supercritical CO2 storage: a preliminary assessment

The Triassic–Jurassic South Georgia Rift (SGR) Basin, buried beneath Coastal Plain sediments of southern South Carolina, southeastern Georgia, western Florida, and southern Alabama, consists of an assemblage of continental rift deposits (popularly called red beds), and mafic igneous rocks (basalt flows and diabase sills). The red beds are capped by basalts and/or diabase sills, and constitute the target for supercritical CO₂ storage as part of a Department of Energy funded project to study the feasibility for safe and permanent sequestration. The purpose of this research is to evaluate subsurface suitability for underground CO₂ storage in terms of the local and regional distribution of porous and permeable reservoirs. In addition, unlike shale-capped CO₂ reservoirs, very little is known about the ability of basalts and diabase sills to act as viable seals for CO₂ storage. New results demonstrate the presence of confined porous rocks that may be capable of storing significant quantities of supercritical CO₂. Reservoir thicknesses as high as 420 m and an average porosity as high as 14 % were obtained. The SGR Basin manifests distinct porosity–permeability regimes that are influenced by the depositional environments. These are: a high-porosity, medium/low-permeability zone associated with lacustrine deposits, a medium/low-porosity, low-permeability zone dominated by fluvial fine- to very fine-grained sandstone, and an extremely low porosity and permeability zone characterized by fluvial and alluvial-fan deposits. Analyses further show that the basalt flows and diabase sills are characterized by low porosity as well as high seismic velocities and densities that are favorable to caprock integrity.     

Macrobenthos and multi-molecular markers as indicators of environmental contamination in a South American port (Mar del Plata,Southwest Atlantic)

We evaluated benthic habitat quality along a presumed contamination gradient in the Mar del Plata port (Southwestern Atlantic) by coupling biological and chemical proxies in a multidisciplinary approach. Organic matter and photosynthetic pigment contents were higher in silty-clay bottoms of the inner port sites. Levels of all fecal steroids decreased from the inner sites to the port inlet. High concentrations of coprostanol in the inner sites seemed to derive from a permanent population of sea lions rather than from sewage outfalls due to coprostanol/epicoprostanol ratio (IV) values <2.5. PAHs levels were also higher in the inner sector, related to both biomass combustion and petroleum combustion associated to local marine traffic. High disturbance and low ecological status were reflected in low benthic diversity and high AMBI values in the inner sites.     

Optical dating of clastic deposits generated by an extreme marine coastal flood: The 1755 tsunami deposits in the Algarve (Portugal)

Identification of past tsunamis is important for risk assessment and management of coastal areas. Obtaining accurate and precise ages of sediments originating from such extreme marine coastal floods is crucial for a reliable estimation of the recurrence interval of these often devastating events. We present here the results of quartz optical dating and ¹⁴C dating of two sites (Boca do Rio and Martinhal) on the Algarve coast (southern Portugal). These sites contain deposits of the great tsunami of November 1, 1755. The sections were described using sedimentological techniques; at both sites tsunami-laid sands and gravels were identified, intercalated between estuarine muds. Quartz luminescence ages from these sedimentary successions were derived using standard SAR-OSL dating using multi-grain sub-samples. A multiple sampling strategy was employed with several samples taken from the AD 1755 tsunami deposit and from the sediments bracketing the tsunami layer. Our SAR-OSL protocol was shown to be appropriate using dose recovery measurements (measured/given dose ratio of 1.004 ± 0.007, n = 165). The several OSL ages from the 1755 tsunamigenic deposits are internally reproducible but yield age overestimates of between 20 and 125% (60–310 years respectively); this is in agreement with values reported in the literature for similar deposits. The age overestimation of the tsunami-laid sands is presumably due to the rapid erosion and deposition of older sediments, with insufficient light exposure for complete bleaching during the tsunami event itself. The absence of significant bleaching during the tsunami is also suggested by the shape of the dose distributions based on sub-samples made up of only about 100 grains. Analysis of the distributions with the minimum-age model seems to yield the expected age for two of the three distributions. It is important to note that age offsets of a few tens of years to a few hundred years rapidly become insignificant when dating older (>1 to few ka) tsunami layers.     

Polycyclic aromatic hydrocarbons and amino acids in meteorites and ice samples from LaPaz Icefield,Antarctica

Abstract— –We have analyzed ice samples and meteorites from the LaPaz region of Antarctica to investigate the composition of polycyclic aromatic hydrocarbons (PAHs) and amino acids with the goal to understand whether or not there is a compositional relationship between the two reservoirs. Four LL5 ordinary chondrites (OCs) and one CK carbonaceous chondrite were collected as part of the 2003/2004 ANSMET season. Ice samples collected from directly underneath the meteorites were extracted. In addition, exhaust particles from the snowmobiles used during the expedition were collected to investigate possible contributions from this source. The meteorite samples, the particulate matter and solid‐state extracts of the ice samples and the exhaust filters were subjected to two‐step laser mass spectrometry (L2MS) to investigate the PAH composition. For amino acids analysis, the meteorites were extracted with water and acid hydrolyzed, and the extracts were analyzed with offline OPA/NAC derivatization combined with liquid chromatography with UV fluorescence detection and time of flight mass spectrometry (LC‐FD/ToF‐MS). PAHs in the particulate matter of the ice were found to be qualitatively similar to the meteorite samples, indicating that micron‐sized grains of the meteorite may be embedded in the ice samples. The concentration levels of dissolved PAHs in all the ice samples were found to be below the detection limit of the L2MS. The PAH composition of the snowmobile exhaust is significantly different to the one in particulate matter, making it an unlikely source of contamination for Antarctic meteorites. The amino acids glycine, β‐alanine and γ‐amino‐n‐butyric acid that were detected at concentrations of 3 to 19 parts per billion (ppb) are probably indigenous to the Antarctic meteorites. Some of the LaPaz ice samples were also found to contain amino acids at concentration levels of 1 to 33 parts per trillion (ppt), in particular α‐aminoisobutyric acid (AIB), an abundant non‐protein amino acid of extraterrestrial origin found in some carbonaceous chondrites. We hypothesize that this amino acid could have been extracted from Antarctic micrometeorites and the particulate matter of the meteorites during the concentration procedure of the ice samples.     

漏阈值系统的自组织临界性: 近平均场的动力学影响及其对地震、神经生物学和预测方面的意义

阈值系统被看作是自然界中某些最重要的非线性自组织系统,包括地震断层系统、神经网络、超导和半导体、互联网以及政治、社会和生态系统。所有这些系统都具有与时、空、强相关的动力学,且都典型地显示了时空尺度的多重性。我们在两种不同尺度上讨论地震阈值系统自组织的物理学问题：(1)“微观”的实验室尺度,来自模拟结果的考虑导致了动力学方程,这些方程可以推导从滑动实验中得到的结果;(2)“宏观”的地震断层系统尺度,强相关地震断层系统的物理学可以通过应用定义在希尔伯特本征态空间有关的态向量来理解。所有的这些系统中,长程相关导致局部各态历经动力学的存在。耗损效应的存在导致了“漏阈值”动力学的出现,它等同于一个控制与背景涨落尺度有关的成核事件尺度的新的标度场的出现。在宏观地震断层尺度的框架下,这些作为一种预报未来地震活动方法的观念显示出了比较大的希望。     

Evidences for multiple remagnetization of Proterozoic dykes from Iguerda inlier (Anti-Atlas Belt,Southern Morocco)

No paleomagnetic data exist for Paleo-Mesoproterozoic times of the West African Craton (WAC). Therefore, paleogeographic reconstructions for such old geological times are difficult to constrain. Gaps on the sedimentary record and intense remagnetizations are the major problems that paleomagnetic studies come across. Recent geochronological results for dyke swarms that intrude several Proterozoic inliers of WAC in the Anti-Atlas Belt (southern Morocco) revealed ages between Paleoproterozoic and early Neoproterozoic, opening for the first time a window of opportunity to conduct paleomagnetic studies and tentatively infer about the paleoposition of WAC during Proterozoic. On this scope we conducted a paleomagnetic study on seven Proterozoic dykes of the Iguerda inlier. The meaning of the obtained paleomagnetic directions was evaluated by rock magnetic and mineral analyses, complemented by petrographic observations. Our samples record the presence of a complex history of remagnetization, mostly assigned to several Phanerozoic thermal/chemical events, in particular to the late stages of Pan African orogeny (s.l.), to the Late Carboniferous Variscan orogeny, and even to more recent events. The recognized remagnetization processes are related to widespread metamorphic events under greenschist facies followed by low-temperature oxidation, both responsible for the formation of new magnetic phases, like magnetite and hematite. These events obliterated the primary (magmatic) thermo-remanent magnetization and promoted multiple remagnetizations of the dykes, thermally and chemically. For only one dyke the presence of primary magnetization is possible to infer, though not to confirm, and would place WAC at an equatorial position around 1750 Ma.     

The influence of cloud cover index on the accuracy of solar irradiance model estimates

Summary Cloud cover index (CCI) obtained from satellite images contains information on cloud amount and their optical thickness. It is the chief climate data for the assessment of solar energy resources in most radiative transfer models, particularly for the model BRASIL-SR that is currently operational at CPTEC. The wide range of climate environments in Brazil turns CCI determination into a challenging activity and great effort has been directed to develop new methods and procedures to improve the accuracy of these estimations from satellite images (Martins 2001; Martins et al. 2003a; Ceballos et al. 2004). This work demonstrates the influence of CCI determination methods on estimates of surface solar irradiances obtained by the model BRASIL-SR comparing deviations among ground data and model results. Three techniques using visible and/or thermal infrared images of GOES-8 were employed to generate the CCI for input into the model BRASIL-SR. The ground-truth data was provided by the solar radiation station located at Caicó/PE, in Brazilian Northeast region, which is part of the UNEP/GEF project SWERA (Solar and Wind Energy Resources Assessment). Results have shown that the application of the bi-spectral techniques have reduced mean bias error up to 66% and root mean square error up to 50% when compared to the usual technique for CCI determination based on the straightforward determination of month-by-month extremes for maximum and minimum cloud states. Correspondence: Fernando R. Martins, Brazilian Institute for Space Research (INPE), P.O. Box 515, S?o José dos Campos, 12245-970 S?o Paulo, Brazil     

Paradoxes of modernity: imperial Rio de Janeiro, 1808–1821

This paper examines the spatial dynamics of urbanism in Rio de Janeiro during the early nineteenth century. Conventional narratives of modernisation fail to capture the complexities of this moment, between 1808 and 1821, when the city replaced Lisbon as the capital of the Portuguese empire. The position of colony and metropolis were inverted, Portuguese absolutism was bolstered by British liberalism, and a market-economy arose alongside the expansion of slavery. As the newly-created imperial capital, Rio felt the effects of these various transformations: the physical boundaries of the city rapidly expanded, its economy diversified and the cultural life of the city was re-shaped. Our aim in this paper is to understand this particular moment of urban transformation as a product of the intersection of global networks of trade, slavery and industrial capitalism. Rather than depicting the historical geography of the city as a passive space for European conquest and expansion, we consider the extent to which its urban dynamics were shaped by a distinct local geography of globalisation. In particular, we examine the interrelated spatialities that are part and parcel of the modernising process.     

Selective chemical extraction of Cu from selected mineral and soil samples: enhancement of Cu geochemical anomalies in Southern Portugal

The study described herein concerns the application of selective chemical extractions on metal-bearing minerals and soils to geochemical exploration. Specifically, the study aims at the detection of anomalous soils in the vicinity of two mineralized zones in Southern Portugal.A kinetic study of the selectivity of partial chemical extractions applied to Cu minerals has been carried out in order to establish a systematic procedure (reagents, extraction plateau, etc.) which could be recommended for soils of the two study zones. It is shown that: (1) NH₄ acetate dissolves malachite, azurite and cuprite completely and chrysocolla, conicalcite and atacamite only partially; (2) hydroxylamine hydrochloride dissolves chrysocolla and conicalcite only partially; (3) H₂O₂ dissolves chalcopyrite only partially; (4) NH₄ oxalate (U.V.) dissolves conicalcite and atacamite only partially; (5) mixed-acid attack dissolves residual chalcopyrite, chrysocolla, atacamite and conicalcite.A total of 740 soil samples were collected from the Salgadinho and Tinoca areas. The Cu mineralization in the Salgadinho area is situated in an Upper-Devonian Volcanic-Siliceous Complex. The weathering products of the mineralization are mainly amorphous iron oxides, goethite and hematite. The Cu mineralization in Tinoca area is located in the Arronches-Campo Maior belt, where stratiform Cu mineralization is found. The weathering products of the mineralization are mainly malachite, amorphous iron oxides, goethite and hematite.In order to identify the Cu-bearing phases and the extraction plateau, the −80 mesh fraction of two soil samples was submitted to an extraction procedure using the following reagents in sequence: NH₄ acetate, hydroxylamine hydrochloride, NH₄ oxalate (dark), NH₄ oxalate (U.V.) and finally strong acids.In soils from the Salgadinho and Tinoca areas, the use of NH₄ oxalate (U.V.) in single dissolution which would incorporate those phases dissolved by NH₄ acetate and NH₄ oxalate (dark), gives the broadest anomalous surface and higher contrast for Cu than acid digestion. The analysis of NH₄ oxalate (U.V.) extractions, instead of acid digestion, can thus be recommended for both areas.