Sedimentary Rock

The IGUANES cruise took place in May 2013 on the R/V L'Atalante along the Demerara passive transform margin off French Guiana and Surinam. Seismic, multibeam and chirp acquisitions were made. Piston cores were collected for pore geochemistry and sedimentology. A mooring was deployed on the sea-bottom for 10 months (temperature, salinity, turbidity and current measurements). This new dataset highlights the lateral variability of the 350 km-long Guiana–Surinam transform margin due to the presence of a releasing bend between two transform segments. The adjacent Demerara Plateau is affected by a 350 km-long giant slide complex. This complex initiated in Cretaceous times and was regularly reactivated until recent times. Since the Miocene, contourite processes seem to be active due to the onset of the North Atlantic Deep Water (NADW) bottom current. A main NADW water vein flows towards SE, eroding slide headscarps and allowing the deposition of contourite drifts. Numerous depressions ...

Abstract High-resolution 2D seismic reflection profiles were examined to explore the stratigraphic architecture of the late Quaternary sediments deposited in the Beibu Gulf (SW off the Hainan Island, South China Sea). Two discontinuities identified in previous research by seismic reflectors R1 (top) and R2 (bottom) allowed to infer the presence of a paleodelta offshore Hainan Island. A detailed analysis of all discontinuities determined the extension of delta body, its thickness and spatial pattern of deltaic clinoforms. Analysis of data obtained by interpretation of seismic records allowed also to depict the relief of lower and upper delta surfaces identified by major erosional discontinuities. The seismic cross-sections provided tools with which to discern all the erosional incisions representing paleo-distributary channels of the delta on both surfaces. In addition, the delta geometry and clinoform dip angles were determined. Analyses have provided information on the direction of sediment transport and sources of deltaic sedimentary material. Distribution of vectors indicating the direction of delta progradation revealed the sediment transport from Hainan Island to be generally southwards to Yinggehai Basin and further towards the shelf edge, thus supporting the hypothesis of Hainan Island as the main source of sediment supply. The vector distribution is unclear in the westernmost part of delta body only, mainly because of an insufficient coverage of this part of the Gulf with seismic tracks and disturbances related to other sediment sources reaching Beibu Gulf in the north, which significantly contributed to the sediment supply.

: A study was performed of the seismic velocity structure of the South China Shelf from the westernmost parts of the Beibu Gulf, adjacent to the Gulf of Tonkin, south of Hainan Island and offshore southern mainland China, as far east as 118 deg east. Stacking velocities from petroleum industry multichannel seismic surveys were compiled into a database from which the depth or two way travel time to any given velocity interval could be calculated. The data was filtered to remove major decreases in velocity with depth, as these normally reflected decreasing data quality below -3 km. Data quality is typically good to 3 km, the approximate level of basement, and shows a good correlation with pre-existing seismic velocity data from sonobuoys. Seismically the shelf sediments are usually flat bedded, with generally well defined reflective character. The slope does not appear to be strongly affected by slumping, although locally such disturbances ar,e noted. The seismic data show that the se...

Five examples, obtained during exploration for hydrocarbons in the Pannonian Basin of Hungary, are used to show how the interpretation of seismic sections can be usefully complemented by results from MT surveys.Selection of the most appropriate MT quantities, considered to be proper ‘MT attributes’ for the purpose of visualization as well as recognition of the subsurface structures and the different inversions of MT data is essential for practical integration of seismic and MT surveys.A new technique providing a semiquantitive MT-attribute pseudosection for the purpose of visualization of the subsurface structures is proposed. The procedure utilizes derivative functions of the phase of MT impedance for visualization and derives estimated depths from the Bostick transformation of Cagniard apparent resistivities.On the basis of the MT-attribute pseudosections, constructed from the phase derivatives and transformed resistivity data, depths are estimated for interfaces between geological formations with significant resistivity contrast. In particular examples, the interface between the Tertiary sediments and the older basement rocks as well as tectonic fracture zones with decreased resistivity can be resolved.

Practical use of Trichoderma harzianum requires feasible formulated products. The objective of this study was to investigate the survival and effectiveness of a T. harzianum bentonite–vermiculite formulation against fusarium wilt and its growth-promotion effect on melon plants under nursery conditions compared with the incorporation of this agent as a nonformulated conidia suspension. The effectiveness of the application of T. harzianum to melon plants was related directly to its formulation, as the formulation had a clear influence on its survival on peat. The formulated form maintained the inoculation level of T. harzianum colony-forming units after 8 weeks, whereas the nonformulated form reduced it by two orders of magnitude. Plants treated with the bentonite–vermiculite formulation showed a higher shoot weight and higher resistance to fusarium wilt disease.

SummaryThe study of groundwater hydrogeochemistry of the Paleozoic Basses-Laurentides sedimentary rock aquifer system in Québec produced a large geochemical dataset. Groundwater samples were collected at 153 sites over a 1500 km 2 study area and analyzed for major and minor ions. The large number of data can lead to difficulties in the integration, interpretation and representation of the results. Two multivariate statistical methods, hierarchical cluster analysis (HCA) and principal components analysis (PCA), were applied to a subgroup of the dataset to evaluate their usefulness to classify the groundwater samples, and to identify geochemical processes controlling groundwater geochemistry. This subgroup consisted of 144 samples and 14 parameters (Ca 2+, Mg 2+, Na +, K +, HCO3-, Cl -, SO42-, Fe 2+, Mn 2+, Br -, Sr 2+, F -, Ba 2+, HS -). Seven geochemically distinct clusters, C1-C7, resulted from the HCA. Samples from clusters C3, C4, C6 and C7 are mostly located in preferential recharge areas. The majority of these samples have Ca-Mg-HCO 3 recharge groundwater (C3, C6, C7) and Na-HCO 3 evolved groundwater (C4). Samples from the other three clusters (C1, C2, C5) are characteristic of an aquifer system under confined conditions. The majority of these samples have Na-HCO 3 evolved groundwater (C1, C5) and Na-Cl ancient groundwater that exhibits elevated concentrations in Br - (C2). In addition to recognizing the importance of hydrogeological conditions on groundwater geochemistry, the distribution of clusters also showed the importance of the geological formations on minor and trace elements, such as Fe 2+, Mn 2+, Sr 2+, F - and Ba 2+. The first five components of the PCA account for 78.3% of the total variance in the dataset. Component 1 is defined by highly positive loadings in Na +, Cl - and Br - and is related to groundwater mixing with Champlain Sea water and solute diffusion from the marine clay aquitard. The high positive loadings in Ca 2+ and Mg 2+ of component 2 suggest the importance of dissolution of carbonate rocks in this aquifer system. From their characteristic loadings, the first two components are defined as the "salinity" and "hardness" components, respectively. Components 3-5 are related to more local and geological effects. The integration of the HCA and the PCA, with conventional classification of groundwater types, as well as with the hydrogeological and geological contexts, allowed the division of the region into four main geochemical areas, providing an improved regional picture of the aquifer system dynamics and hydrogeochemical evolution of groundwater. The following factors were recognized as influencing the evolution of groundwater identified in every geochemical area: (1) geological characteristics including sedimentary rock type and till mineralogy; (2) hydrogeological characteristics represented by the level of confinement and the hydraulic gradient; and (3) the geological history including the latest glaciation and the Champlain Sea invasion. With its integrated approach, this hydrogeochemical study contributes to the characterization and understanding of complex groundwater flow systems, and provides an example of the long-term geochemical evolution of hydrogeological systems after a major perturbation, in this case seawater invasion.

La decouverte de grandes accumulations de petrole dans les couches rocheuses au-dessous du sel (ou pre-sel) des bassins sedimentaires offshore s'avere une vraie « surprise petroliere » au Bresil, qui transforme le contexte strategique petrolier de la nation. Cet evenement est discute dans toutes les spheres politiques. Il gagne aussi une grande audience dans la presse nationale et internationale. Il s'agit d'un grand theme qui a des repercussions sur la dynamique electorale de la campagne presidentielle de 2010, qui s'annonce diffccile et imprevisible pour tous les candidats potentiels. Le gouvernement du president Lula a bien voulu marquer une frontiere historique (et geographique) claire en proposant des modifications legales et institutionnelles importantes pour le developpement des ressources petrolieres du pre-sel (en opposition au modele actuel, qui restera valable pour les ressources trouvees dans les couches rocheuses au-dessus du sel, ou post-sel). L'objectif de ce travail est de presenter les principaux elements des modifications legales et institutionnelles proposees. Le texte se concentre principalement sur les activites en amont de l'exploration et de la production du petrole et sur les questions de captation et de distribution de la rente petroliere. Ce sont les deux themes principaux sur lesquels le nouveau modele legal et institutionnel se penche.

Palaeomagnetic analysis of Mesozoic pelagic sediments of the island of Misool, northeast Indonesia, showed that a large part of the sediments have very low initial remanence intensities. Progressive demagnetization both with alternating magnetic fields and with heating yielded characteristic remanence directions in two formations: the Waaf Formation of Santonian age revealed the following data: D = 318.10, I = -33.8

A new deterministic computer program has been developed which simulates the evolution of basin stratigraphy on geologic time scales. The stratigraphy of basins reflects the subtle interaction between two basic groups of processes: those controlling the creation and destruction of space in the basin, and those controlling the introduction and removal of sediments. In the program the primary space-controlling mechanisms are eustasy, tectonic subsidence, sediment compaction, and the isostatic response to sediment and water loads. The depositional surface at a given time is modeled as a function of rate of sediment introduction, rate of sediment dispersal, erosion, and slope stability. The nonmarine profile may aggrade or be eroded, with material eroded from the nonmarine portion of the basin added to the marine sediment fill. The program may be used (1) to simulate clastic, carbonate, and mixed carbonate/clastic basin fills in consecutive time slices, (2) to model the stratigraphic response to eustatic and tectonic events, and (3) to evaluate independently derived sea level curves. A movie will be shown illustrating the stratigraphic evolution of a typical passive margin transect in response to changes in the rates of subsidence, sea level rise and fall, and sedimentation.

... 1 Petrobras, E&P, UN-EXP, 500, General Canabarro St., Rio de Janeiro, 20271-200, Brazil; aviana{at}petrobras.com.br 2 Laboratorio de Geologia Marinha, Instituto de Geociencias, Universidade Federal Fluminense, Avenida Litoranea, 24210-340, Niteroi, RJ, Brazil 3 ...

... Although there may be also other causes, such as desiccation or tectonically induced fissures, there is a widespread association of ground failure with water declines (Burbey, 2002, Rojas et al., 2002, Garduño-Monroy et al., 2001, Bell and Helm, 1998, Rothenburg et al., 1995 ...