basin ne atlantic: Topics by Science.gov

  • Assessment of undiscovered oil and gas resources of the East Coast Mesozoic basins of the Piedmont, Blue Ridge Thrust Belt, Atlantic Coastal Plain, and New England Provinces, 2011

    USGS Publications Warehouse

    Milici, Robert C.; Coleman, James L.; Rowan, Elisabeth L.; Cook, Troy A.; Charpentier, Ronald R.; Kirschbaum, Mark A.; Klett, Timothy R.; Pollastro, Richard M.; Schenk, Christopher J.

    2012-01-01

    During the early opening of the Atlantic Ocean in the Mesozoic Era, numerous extensional basins formed along the eastern margin of the North American continent from Florida northward to New England and parts of adjacent Canada. The basins extend generally from the offshore Atlantic continental margin westward beneath the Atlantic Coastal Plain to the Appalachian Mountains. Using a geology-based assessment method, the U.S. Geological Survey estimated a mean undiscovered natural gas resource of 3,860 billion cubic feet and a mean undiscovered natural gas liquids resource of 135 million barrels in continuous accumulations within five of the East Coast Mesozoic basins: the Deep River, Dan River-Danville, and Richmond basins, which are within the Piedmont Province of North Carolina and Virginia; the Taylorsville basin, which is almost entirely within the Atlantic Coastal Plain Province of Virginia and Maryland; and the southern part of the Newark basin (herein referred to as the South Newark basin), which is within the Blue Ridge Thrust Belt Province of New Jersey. The provinces, which contain these extensional basins, extend across parts of Georgia, South Carolina, North Carolina, Virginia, Maryland, Delaware, Pennsylvania, New Jersey, New York, Connecticut, and Massachusetts.

  • An Estimate of the North Atlantic Basin Tropical Cyclone Activity for the 2010 Hurricane Season

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.

    2010-01-01

    Estimates are presented for the tropical cyclone activity expected for the 2010 North Atlantic basin hurricane season. It is anticipated that the 2010 season will be more active than the 2009 season, reflecting increased frequencies more akin to that of the current more active phase that has been in vogue since 1995. Averages (+/- 1 sd) during the current more active phase are 14.5+/-4.7, 7.8+/-3.2, 3.7+/-1.8, and 2+/- 2, respectively, for the number of tropical cyclones (NTC), the number of hurricanes (NH), the number of major hurricanes (NMH), and the number of United States (U.S.) land-falling hurricanes (NUSLFH). Based on the “usual” behavior of the 10-yma parametric first differences, one expects NTC = 19+/-2, NH = 14+/-2, NMH = 7+/-2, and NUSLFH = 4+/-2 for the 2010 hurricane season; however, based on the “best guess” 10-yma values of surface-air temperature at the Armagh Observatory (Northern Ireland) and the Oceanic Nino Index, one expects NTC > or equals 16, NH > or equals 14, NMH > or equals 7, and NUSLFH > or equals 6.

  • The concurrence of atmospheric rivers and explosive cyclogenesis in the North Atlantic and North Pacific basins

    NASA Astrophysics Data System (ADS)

    Eiras-Barca, Jorge; Ramos, Alexandre M.; Pinto, Joaquim G.; Trigo, Ricardo M.; Liberato, Margarida L. R.; Miguez-Macho, Gonzalo

    2018-01-01

    The explosive cyclogenesis of extratropical cyclones and the occurrence of atmospheric rivers are characteristic features of a baroclinic atmosphere, and are both closely related to extreme hydrometeorological events in the mid-latitudes, particularly on coastal areas on the western side of the continents. The potential role of atmospheric rivers in the explosive cyclone deepening has been previously analysed for selected case studies, but a general assessment from the climatological perspective is still missing. Using ERA-Interim reanalysis data for 1979-2011, we analyse the concurrence of atmospheric rivers and explosive cyclogenesis over the North Atlantic and North Pacific basins for the extended winter months (ONDJFM). Atmospheric rivers are identified for almost 80 % of explosive deepening cyclones. For non-explosive cyclones, atmospheric rivers are found only in roughly 40 % of the cases. The analysis of the time evolution of the high values of water vapour flux associated with the atmospheric river during the cyclone development phase leads us to hypothesize that the identified relationship is the fingerprint of a mechanism that raises the odds of an explosive cyclogenesis occurrence and not merely a statistical relationship. These new insights on the relationship between explosive cyclones and atmospheric rivers may be helpful to a better understanding of the associated high-impact weather events.

  • A paleomagnetic and relative paleointensity record from the Argentine Basin (western South Atlantic Ocean) for the last ~125 kyrs

    NASA Astrophysics Data System (ADS)

    Heil, C. W., Jr.; Stoner, J. S.; St-Onge, G.; King, J. W.

    2015-12-01

    The paucity of paleomagnetic records from the western South Atlantic Ocean presents a significant gap in our understanding of the spatial variations in geomagnetic field dynamics as they relate to the occurrence of geomagnetic excursions and changes in field strength. As such, high quality records from this region can help build upon Holocene observations and extend the geographic and temporal data coverage for spherical harmonic models. To that end, we present paleomagnetic directional (inclination) and strength (relative paleointensity) records from two cores from the Argentine Basin (RC11-49 and RC16-88). Although the cores were collected more than 40 years ago, the sediments appear to hold a stable remanence and reliable magnetic directions, as evidenced by their reproducibility between the two cores that are separated by ~25 km. The records show evidence of 4 excursional features in the uppermost 16-m of the sediments from the basin. A comparison of the relative paleointensity records from these cores to the South Atlantic Paleointensity Stack (SAPIS) (Stoner et al., 2002) and the relative paleointensity record from ODP Site 1089 (Stoner et al., 2003) indicate that the sediments reliably record relative changes in geomagnetic field intensity and suggests that the longest record (RC11-49) spans the last ~125 kyrs. Our results indicate that the sediments of the Argentine Basin are an important sedimentary archive of geomagnetic field behavior and strength at least through the Holocene and Late Pleistocene and highlight the need for further studies of cores within the basin.

  • Controls on facies and sequence stratigraphy of an upper Miocene carbonate ramp and platform, Melilla basin, NE Morocco

    USGS Publications Warehouse

    Cunningham, K.J.; Collins, Luke S.

    2002-01-01

    Upwelling of cool seawater, paleoceanographic circulation, paleoclimate, local tectonics and relative sea-level change controlled the lithofacies and sequence stratigraphy of a carbonate ramp and overlying platform that are part of a temporally well constrained carbonate complex in the Melilla basin, northeastern Morocco. At Melilla, from oldest to youngest, a third-order depositional sequence within the carbonate complex contains (1) a retrogradational, transgressive, warm temperate-type rhodalgal ramp; (2) an early highstand, progradational, bioclastic platform composed mainly of a temperate-type, bivalve-rich molechfor facies; and (3) late highstand, progradational to downstepping, subtropical/tropical-type chlorozoan fringing Porites reefs. The change from rhodalgal ramp to molechfor platform occurred at 7.0??0.14 Ma near the Tortonian/Messinian boundary. During a late stage in the development of the bioclastic platform a transition from temperate-type molechfor facies to subtropical/tropical-type chlorozoan facies occurred and is bracketed by chron 3An.2n (??? 6.3-6.6 Ma). Comparison to a well-dated carbonate complex in southeastern Spain at Cabo de Gata suggests that upwelling of cool seawater influenced production of temperate-type limestone within the ramp and platform at Melilla during postulated late Tortonian-early Messinian subtropical/tropical paleoclimatic conditions in the western Paleo-Mediterranean region. The upwelling of cool seawater across the bioclastic platform at Melilla could be related to the beginning of ‘siphoning’ of deep, cold Atlantic waters into the Paleo-Mediterranean Sea at 7.17 Ma. The facies change within the bioclastic platform from molechfor to chlorozoan facies may be coincident with a reduction of the siphoning of Atlantic waters and the end of upwelling at Melilla during chron 3An.2n. The ramp contains one retrogradational parasequence and the bioclastic platform three progradational parasequences. Minor erosional surfaces

  • Screening of perfluorinated compounds in water, sediment and biota of the Llobregat River basin (NE Spain)

    NASA Astrophysics Data System (ADS)

    Campo, Julian; Perez, Francisca; Pico, Yolanda; Farre, Marinella; Barcelo, Damia; Andreu, Vicente

    2014-05-01

    PFCs present significant thermal and chemical stability being persistent in the environment, where they can bio-accumulate and adversely affect humans and wildlife (Llorca et al., 2012). Human exposure to PFCs is of concern since PFCs tend to be associated with fatty acid binding proteins in the liver or albumin proteins in blood, and have been detected in human serum, urine, saliva, seminal plasma and breast milk (Sundstrom et al., 2011). This study is aimed at the screening of 21 perfluorinated compounds (PFCs) in environmental samples by high-performance liquid chromatography tandem mass spectrometry (LC-MS/MS). The main objective is to identify target compounds at low levels in water, sediments and biota of the Llobregat River (2010), second longest river in Catalonia and one of Barcelona’s major drinking water resources. PFCs were extracted from water samples by Solid Phase Extraction (SPE); from sediment by ultrasonication with acidified methanol followed by an off-line SPE procedure (Picó et al., 2012), and from biota (fish) with alkaline digestion, clean-up by TurboFlow™ on line technology coupled to LC-MS/MS (Llorca et al., 2012). The limits of detection (LODs) and limits of quantification (LOQs) of the method were calculated by analysis of spiked river water, sediment, and biota with minimum concentrations of each individual compound at a signal-to-noise ratio of 3 and 10, respectively. The LODs and LOQs of the method in river water ranged between 0.004 and 0.8 ng L-1 and between 0.01 and 2 ng L-1, respectively. In sediment LODs were 0.013-2.667 ng g-1 dry weight (dw) and LOQs were 0.04-8 ng g-1 dw, meanwhile in biota these were 0.006-0.7 pg μL-1 and 0.02-2.26 pg μL-1, respectively. Recoveries ranged between 65% and 102% for all target compounds. The method was applied to study the spatial distribution of these compounds in the Llobregat River basin. For this, a total of 40 samples were analysed (14 water, 14 sediments, 12 fishes). Of the 21 target

  • Forecasting Total Water Storage Changes in the Amazon basin using Atlantic and Pacific Sea Surface Temperatures

    NASA Astrophysics Data System (ADS)

    De Linage, C.; Famiglietti, J. S.; Randerson, J. T.

    2013-12-01

    Floods and droughts frequently affect the Amazon River basin, impacting the transportation, river navigation, agriculture, economy and the carbon balance and biodiversity of several South American countries. The present study aims to find the main variables controlling the natural interannual variability of terrestrial water storage in the Amazon region and to propose a modeling framework for flood and drought forecasting. We propose three simple empirical models using a linear combination of lagged spatial averages of central Pacific (Niño 4 index) and tropical North Atlantic (TNAI index) sea surface temperatures (SST) to predict a decade-long record of 3°, monthly terrestrial water storage anomalies (TWSA) observed by the Gravity Recovery And Climate Experiment (GRACE) mission. In addition to a SST forcing term, the models included a relaxation term to simulate the memory of water storage anomalies in response to external variability in forcing. Model parameters were spatially-variable and individually optimized for each 3° grid cell. We also investigated the evolution of the predictive capability of our models with increasing minimum lead times for TWSA forecasts. TNAI was the primary external forcing for the central and western regions of the southern Amazon (35% of variance explained with a 3-month forecast), whereas Niño 4 was dominant in the northeastern part of the basin (61% of variance explained with a 3-month forecast). Forcing the model with a combination of the two indices improved the fit significantly (pbasin as a whole with a 3-month lead time. While 66% of the observed variance was explained in the northeastern Amazon, only 39% of the variance was captured by the combined model in the central and western regions, suggesting that other, more local, forcing sources were

  • Reconstruction of Sea/Lake-Level Changes in an Active Strike-Slip Basin (Gulf of Cariaco, NE Venezuela)

    NASA Astrophysics Data System (ADS)

    van Daele, M.; Audemard, F.; Beck, C.; de Batist, M.; van Welden, A.; Moernaut, J.; 2006 Shipboard Party, G.

    2008-05-01

    . According to this age model, our seismic stratigraphy reaches back to MIS6, and the average sedimentation rate in the central parts of the gulf since MIS5e is 0.92 mm/y. Our data show that reconstructed lake levels in the Gulf of Cariaco, which represent a proxy for climate in NE- Venezuela, are very strongly coupled to the global stadials and interstadials of the last glacial period. Also the Younger Dryas is recognised in the sedimentary record of the Gulf of Cariaco as lowstand deposit resulting from an (almost) complete desiccation. Our data reveal that the stratigraphy of the Gulf of Cariaco holds a very accurate, complete and promising record of eustasy and climate change, at least since the penultimate glacial maximum. The quality of this record and the vicinity to the iconic Cariaco Basin make the Gulf of Cariaco an ideal target for future ocean drilling (or long coring).

  • Nonlinear interactions between the Amazon River basin and the Tropical North Atlantic at interannual timescales

    NASA Astrophysics Data System (ADS)

    Builes-Jaramillo, Alejandro; Marwan, Norbert; Poveda, Germán; Kurths, Jürgen

    2018-04-01

    We study the physical processes involved in the potential influence of Amazon (AM) hydroclimatology over the Tropical North Atlantic (TNA) Sea Surface Temperatures (SST) at interannual timescales, by analyzing time series of the precipitation index (P-E) over AM, as well as the surface atmospheric pressure gradient between both regions, and TNA SSTs. We use a recurrence joint probability based analysis that accounts for the lagged nonlinear dependency between time series, which also allows quantifying the statistical significance, based on a twin surrogates technique of the recurrence analysis. By means of such nonlinear dependence analysis we find that at interannual timescales AM hydrology influences future states of the TNA SSTs from 0 to 2 months later with a 90-95% statistical confidence. It also unveils the existence of two-way feedback mechanisms between the variables involved in the processes: (1) precipitation over AM leads the atmospheric pressure gradient between TNA and AM from 0 to 2 month lags, (2) the pressure gradient leads the trade zonal winds over the TNA from 0 to 3 months and from 7 to 12 months, (3) the zonal winds lead the SSTs from 0 to 3 months, and (4) the SSTs lead precipitation over AM by 1 month lag. The analyses were made for time series spanning from 1979 to 2008, and for extreme precipitation events in the AM during the years 1999, 2005, 2009 and 2010. We also evaluated the monthly mean conditions of the relevant variables during the extreme AM droughts of 1963, 1980, 1983, 1997, 1998, 2005, and 2010, and also during the floods of 1989, 1999, and 2009. Our results confirm that the Amazon River basin acts as a land surface-atmosphere bridge that links the Tropical Pacific and TNA SSTs at interannual timescales. The identified mutual interactions between TNA and AM are of paramount importance for a deeper understanding of AM hydroclimatology but also of a suite of oceanic and atmospheric phenomena over the TNA, including recently

  • Bottom melting of Arctic Sea Ice in the Nansen Basin due to Atlantic Water influence

    NASA Astrophysics Data System (ADS)

    Muilwijk, Morven; Smedsrud, Lars H.; Meyer, Amelie

    2016-04-01

    Our global climate is warming, and a shrinking Arctic sea ice cover remains one of the most visible signs of this warming. Sea Ice loss is now visible for all months in all regions of the Arctic. Hydrographic and current observations from a region north of Svalbard collected during the Norwegian Young Sea Ice Cruise (N-ICE2015) are presented here. Comparison with historical data shows that the new observations from January through June fill major gaps in available observations, and help describing important processes linking changes in regional Atlantic Water (AW) heat transport and sea ice. Warm and salty AW originating in the North Atlantic enters the Arctic Ocean through the Fram Strait and is present below the Arctic Sea Ice cover throughout the Arctic. However, the depth of AW varies by region and over time. In the region north of Svalbard, we assume that depth could be governed primarily by local processes, by upstream conditions of the ice cover (Northwards), or by upstream conditions of the AW (Southwards). AW carries heat corresponding to the volume transport of approximately 9 SV through Fram Strait, varying seasonally from 28 TW in winter to 46 TW in summer. Some heat is recirculated, but the net annual heat flux into the Arctic Ocean from AW is estimated to be around 40 TW. The Atlantic Water layer temperature at intermediate depths (150-900m) has increased in recent years. Until recently, maximum temperatures have been found to be 2-3 C in the Nansen Basin. Studies have shown that for example, in the West Spitsbergen Current the upper 50-200m shows an overall AW warming of 1.1 C since 1979. In general we expect efficient melting when AW is close to the surface. Previously the AW entering through Fram Strait has been considered as less important because changes in the sea ice cover have been connected to greater inflow of Pacific Water through Bering Strait and atmospheric forcing. Conversely it is now suggested that AW has direct impact on melting of

  • Linking benthic hydrodynamics and cold-water coral occurrences: A high-resolution model study at three cold-water coral provinces in the NE Atlantic

    NASA Astrophysics Data System (ADS)

    Mohn, Christian; Rengstorf, Anna; White, Martin; Duineveld, Gerard; Mienis, Furu; Soetaert, Karline; Grehan, Anthony

    2014-03-01

    Observations from numerous cold-water coral locations in the NE Atlantic show energetic near-bottom flow dynamics along the European continental margin at individual coral mounds and mound clusters. Dynamics are largely controlled by tide-topography interaction generating and enhancing periodic motions such as trapped waves, freely propagating internal tides and internal hydraulic jumps. In this study, linkages between key abiotic parameters and cold water coral occurrences are explored across entire cold-water coral mound provinces using an integrated modelling and observational approach. The 3-D ocean circulation model ROMS-AGRIF was applied to simulate near-bottom hydrodynamic conditions at three provinces in the NE Atlantic (Logachev mounds, Arc mounds and Belgica mounds) adopting a nested model setup with a central grid resolution of 250 m. Simulations were carried out with a focus on accurate high-resolution topography and tidal forcing. The central model bathymetry was taken from high-resolution INSS (Irish National Seabed Survey) seafloor mapping data. The model was integrated over a full one-year reference period starting from the 1st January 2010. Interannual variability was not considered. Tidal forcing was obtained from a global solution of the Oregon State University (OSU) inverse tidal model. Modelled fields of benthic currents were validated against available independent in situ observations. Coral assemblage patterns (presence and absence locations) were obtained from benthic surveys of the EU FP7 CoralFISH programme and supplemented by data from additional field surveys. Modelled near-bottom currents, temperature and salinity were analysed for a 1-month subset (15th April to 15th May 2010) corresponding to the main CoralFISH survey period. The model results show intensified near-bottom currents in areas where living corals are observed by contrast with coral absence and random background locations. Instantaneous and time-mean current speeds at

  • Reproductive and feeding spatial dynamics of the black scabbardfish, Aphanopus carbo Lowe, 1839, in NE Atlantic inferred from fatty acid and stable isotope analyses

    NASA Astrophysics Data System (ADS)

    Farias, Inês; Figueiredo, Ivone; Janeiro, Ana Isabel; Bandarra, Narcisa Maria; Batista, Irineu; Morales-Nin, Beatriz

    2014-07-01

    The black scabbardfish (Aphanopus carbo) is a benthopelagic species widely distributed across the NE Atlantic, where it is admitted to perform a clockwise migration throughout its life cycle stimulated by feeding and reproduction. To overcome the limitations of direct observation of this species, fatty acids profile (FA) and δ15N and δ13C stable isotopes (SI) were analyzed in the muscle tissue of the black scabbardfish and related with diet and maturity. Specimens were collected in four geographic areas in the NE Atlantic: Iceland, the west of the British Isles, mainland Portugal, and Madeira. For all areas, the FA profile was related with the different phases of the reproductive cycle and with diet, whereas the SI were related with diet, environmental characteristics, such as latitude and depth, and particulate organic matter (POM). Stomach content of black scabbardfish caught off mainland Portugal was analyzed and the most frequent prey item identified was the lophogastrid crustacean Gnathophausia zoea, followed by the cephalopod Mastigotheutis spp. and the teleost Rouleina maderensis. For specimens from Iceland and the west of the British Isles, monounsaturated fatty acids (MUFA) were the most important FA, followed by polyunsaturated (PUFA) and saturated FA (SFA), whereas for specimens from mainland Portugal and from Madeira the sequences were PUFA>MUFA>SFA and PUFA>SFA>MUFA, respectively. Immature specimens from the first three areas were found to be accumulating oleic acid which is an intermediate product of the metabolic pathway that transforms SFA to MUFA and these into PUFA. Specimens caught off Madeira were mature and showed a significant prevalence of ARA and DHA which are PUFA with an important role in reproduction. δ15N was significantly higher in the muscle of black scabbardfish from Madeira, whereas δ13C was significantly lower in specimens from Iceland. The low isotopic ratios as well as the prevalence of certain fatty acid trophic markers (FATM

  • Effects of cold-water corals on fish diversity and density (European continental margin: Arctic, NE Atlantic and Mediterranean Sea): Data from three baited lander systems

    NASA Astrophysics Data System (ADS)

    Linley, T. D.; Lavaleye, M.; Maiorano, P.; Bergman, M.; Capezzuto, F.; Cousins, N. J.; D’Onghia, G.; Duineveld, G.; Shields, M. A.; Sion, L.; Tursi, A.; Priede, I. G.

    2017-11-01

    Autonomous photographic landers are a low-impact survey method for the assessment of mobile fauna in situations where methods such as trawling are not feasible or ethical. Three institutions collaborated through the CoralFISH project, each using differing lander systems, to assess the effects of cold-water corals on fish diversity and density. The Biogenic Reef Ichthyofauna Lander (BRIL, Oceanlab), Autonomous Lander for Biological Experiments (ALBEX, NIOZ) and the Marine Environment MOnitoring system (MEMO, CoNISMa) were deployed in four CoralFISH European study regions covering the Arctic, NE Atlantic and Mediterranean, namely Northern Norway (275-310 m depth), Belgica Mound Province (686-1025 m depth), the Bay of Biscay (623-936 m depth), and Santa Maria di Leuca (547-670 m depth). A total of 33 deployments were carried out in the different regions. Both the time of first arrival (Tarr) and the maximum observed number of fish (MaxN) were standardised between the different lander systems and compared between coral and reference stations as indicators of local fish density. Fish reached significantly higher MaxN at the coral stations than at the reference stations. Fish were also found to have significantly lower Tarr in the coral areas in data obtained from the BRIL and MEMO landers. All data indicated that fish abundance is higher within the coral areas. Fish species diversity was higher within the coral areas of Atlantic Ocean while in Northern Norway and Santa Maria di Leuca coral areas, diversity was similar at coral and reference stations but a single dominant species (Brosme brosme and Conger conger respectively) showed much higher density within the coral areas. Indicating that, while cold-water coral reefs have a positive effect on fish diversity and/or abundance, this effect varies across Europe’s reefs.

  • Patterns of landscape form in the upper Rhône basin, Central Swiss Alps, predominantly show lithologic controls despite multiple glaciations and variations in rock uplift rates

    NASA Astrophysics Data System (ADS)

    Stutenbecker, L. A.; Costa, A.; Schlunegger, F.

    2015-10-01

    The development of topography is mainly dependent on the interplay of uplift and erosion, which are in term controlled by various factors including climate, glaciers, lithology, seismic activity and short-term variables such as anthropogenic impact. While most studies have focused on the role of tectonics and climate on the landscape form and underlying processes, less attention has been paid on exploring the controls of lithology on erosion. The Central European Alps are characterized by a large spatial variability in exposed lithologies and as such offer an ideal laboratory to investigate the lithological controls on erosion and landscape form. Here, we focus on the ca. 5400 km2-large upper Rhône basin situated in the Central Swiss Alps to explore how the lithological architecture of the bedrock conditions the Alpine landscape. To this extent, we extract geomorphological parameters along the channels of ca. 50 tributary basins, whose catchments are located in either granitic basement rocks (External massifs), oceanic meta-sedimentary and ophiolitic rocks (Penninic nappes) or fine-grained continental-margin sediments (Helvetic nappes). The analysis of longitudinal river profiles show that all tributary rivers within the Rhône basin are in topographic transient state as testified by mainly convex or concave-convex longitudinal stream channel profiles with several knickpoints of either tectonic or glacial origin. In addition, although the entire Rhône basin shows a strong glacial inheritance (and is still partly glaciated) and some of the highest uplift rates recently measured in the Alps, the river network has responded differently to those perturbations as revealed by the morphometric data. In particular, tributary basins in the Helvetic nappes are the most equilibrated (concave river profiles, overall lower elevations, less steep slope gradients and lowest hypsometric integrals), while the tributaries located in the External massifs are least equilibrated

  • Origin and evolution of phyllosilicate deformation bands in the poorly lithified sandstones of the Rio do Peixe Basin, NE Brazil

    NASA Astrophysics Data System (ADS)

    Nogueira, Francisco; Nicchio, Matheus; Balsamo, Fabrizio; Bezerra, Francisco; Souza, Jorge; Carvalho, Bruno; Storti, Fabrizio

    2017-04-01

    In this work we describe the genetic processes and the microstructural evolution of phylossilicate deformation bands developed in poorly lithified, high porosity sandstones of the Rio do Peixe Basin, Northeast Brazil. The studied deformation bands occur in damage zones of NE-SW and NW-SE transtensional faults that exhibit well developed anastomosed clusters, with a thickness varying from tens of centimeters to 1 meter. The Host rocks are arkosic to lithic arkosic coarse sandstones to fine conglomerate and with less than 1% of clay content in the matrix. Based on (i) field observations, (ii) clay amount in deformation band cores and (iii) clay mineral arrangements in deformation bands cores, we identified two types of phyllosilicate deformation bands: (1) clay smearing deformation bands and (2) phyllosilicate deformation bands formed by clay authigenesis. The former occur only in fault zones that cut across clay-rich layers and are characterized by 45-50% of clay content. Single element chemical analysis indicates that the composition of clay minerals in clay smearing deformation bands is similar to that of clay-rich layers in the host rocks. The dominant deformation mechanism is particulate flow, which produces preferential alignments of grains and clay minerals. Only subordinate cataclasis occurs. Based on microstructural fabrics, three evolutionary stages can be identified for phyllosilicate deformation bands formed by clay authigenesis. The first one is characterized by preferentially cataclasis and weathering of feldspars. Clay concentration is relatively low, reaching 15-20%, with preferential concentration where crushed feldspar abundance is higher. The second stage is characterized by clay migration within deformation bands, to form continuous films with more than 20-25% of clay concentration. In the last stage clay mineral fabric re-organization occurs, forming well a developed S-C foliation. Clay concentration exceeds 35%. Single element chemical analysis

  • Between-Habitat Variation of Benthic Cover, Reef Fish Assemblage and Feeding Pressure on the Benthos at the Only Atoll in South Atlantic: Rocas Atoll, NE Brazil

    PubMed Central

    Longo, G. O.; Morais, R. A.; Martins, C. D. L.; Mendes, T. C.; Aued, A. W.; Cândido, D. V.; de Oliveira, J. C.; Nunes, L. T.; Fontoura, L.; Sissini, M. N.; Teschima, M. M.; Silva, M. B.; Ramlov, F.; Gouvea, L. P.; Ferreira, C. E. L.; Segal, B.; Horta, P. A.; Floeter, S. R.

    2015-01-01

    The Southwestern Atlantic harbors unique and relatively understudied reef systems, including the only atoll in South Atlantic: Rocas atoll. Located 230 km off the NE Brazilian coast, Rocas is formed by coralline red algae and vermetid mollusks, and is potentially one of the most “pristine” areas in Southwestern Atlantic. We provide the first comprehensive and integrative description of the fish and benthic communities inhabiting different shallow reef habitats of Rocas. We studied two contrasting tide pool habitats: open pools, which communicate with the open ocean even during low tides, thus more exposed to wave action; and closed pools, which remain isolated during low tide and are comparatively less exposed. Reef fish assemblages, benthic cover, algal turfs and fish feeding pressure on the benthos remarkably varied between open and closed pools. The planktivore Thalassoma noronhanum was the most abundant fish species in both habitats. In terms of biomass, the lemon shark Negaprion brevirostris and the omnivore Melichtys niger were dominant in open pools, while herbivorous fishes (mainly Acanthurus spp.) prevailed in closed pools. Overall benthic cover was dominated by algal turfs, composed of articulated calcareous algae in open pools and non-calcified algae in closed pools. Feeding pressure was dominated by acanthurids and was 10-fold lower in open pools than in closed pools. Besides different wave exposure conditions, such pattern could also be related to the presence of sharks in open pools, prompting herbivorous fish to feed more in closed pools. This might indirectly affect the structure of reef fish assemblages and benthic communities. The macroalgae Digenea simplex, which is uncommon in closed pools and abundant in the reef flat, was highly preferred in herbivory assays, indicating that herbivory by fishes might be shaping this distribution pattern. The variations in benthic and reef fish communities, and feeding pressure on the benthos between open

  • Between-Habitat Variation of Benthic Cover, Reef Fish Assemblage and Feeding Pressure on the Benthos at the Only Atoll in South Atlantic: Rocas Atoll, NE Brazil.

    PubMed

    Longo, G O; Morais, R A; Martins, C D L; Mendes, T C; Aued, A W; Cândido, D V; de Oliveira, J C; Nunes, L T; Fontoura, L; Sissini, M N; Teschima, M M; Silva, M B; Ramlov, F; Gouvea, L P; Ferreira, C E L; Segal, B; Horta, P A; Floeter, S R

    2015-01-01

    The Southwestern Atlantic harbors unique and relatively understudied reef systems, including the only atoll in South Atlantic: Rocas atoll. Located 230 km off the NE Brazilian coast, Rocas is formed by coralline red algae and vermetid mollusks, and is potentially one of the most “pristine” areas in Southwestern Atlantic. We provide the first comprehensive and integrative description of the fish and benthic communities inhabiting different shallow reef habitats of Rocas. We studied two contrasting tide pool habitats: open pools, which communicate with the open ocean even during low tides, thus more exposed to wave action; and closed pools, which remain isolated during low tide and are comparatively less exposed. Reef fish assemblages, benthic cover, algal turfs and fish feeding pressure on the benthos remarkably varied between open and closed pools. The planktivore Thalassoma noronhanum was the most abundant fish species in both habitats. In terms of biomass, the lemon shark Negaprion brevirostris and the omnivore Melichtys niger were dominant in open pools, while herbivorous fishes (mainly Acanthurus spp.) prevailed in closed pools. Overall benthic cover was dominated by algal turfs, composed of articulated calcareous algae in open pools and non-calcified algae in closed pools. Feeding pressure was dominated by acanthurids and was 10-fold lower in open pools than in closed pools. Besides different wave exposure conditions, such pattern could also be related to the presence of sharks in open pools, prompting herbivorous fish to feed more in closed pools. This might indirectly affect the structure of reef fish assemblages and benthic communities. The macroalgae Digenea simplex, which is uncommon in closed pools and abundant in the reef flat, was highly preferred in herbivory assays, indicating that herbivory by fishes might be shaping this distribution pattern. The variations in benthic and reef fish communities, and feeding pressure on the benthos between open and

  • Migration and diving behavior of Centrophorus squamosus in the NE Atlantic. Combining electronic tagging and Argo hydrography to infer deep ocean trajectories

    NASA Astrophysics Data System (ADS)

    Rodríguez-Cabello, Cristina; González-Pola, Cesar; Sánchez, Francisco

    2016-09-01

    A total of nine leafscale gulper sharks Centrophorus squamosus (Bonnaterre, 1788), were tagged with pop-up, satellite, archival, transmitting tags (PSAT) in the Marine Protected Area (MPA) of El Cachucho (Le Danois Bank) located in waters to the north of Spain, (NE Atlantic). Tags provided data on time, pressure and temperature that were used to examine movement patterns and diving behavior. Data collected from Argo floats in the study area have been used to devise a simple geolocation algorithm to infer the probable routes followed by this species. Tag release points revealed that C. squamosus moved both to the west (Galician waters) and to the north (Porcupine Bank) from the tagging area, suggesting well defined preferred pathways. The inferred trajectories indicated that sharks alternate periods constrained to specific geographical regions with quick and prompt movements covering large distances. Two sharks made conspicuous diurnal vertical migrations being at shallower depths around midnight and at maximum depths at midday, while other sharks did not make vertical migrations. Vertical movements were done smoothly and independently of the fish swimming long-distances or resting in the area. Overall results confirm that this species is highly migratory, supporting speeds of 20 nautical miles.day-1 and well capable to swim and make vertical migrations well above the abyssal plain.

  • Hydrodynamic Conditions Influencing Cold-Water Coral Carbonate Mound Development (Challenger Mound, Porcupine Seabight, NE Atlantic): a Contribution to IODP Exp307

    NASA Astrophysics Data System (ADS)

    Thierens, M.; Odonnell, R.; Stuut, J.; Titschack, J.; Dorschel, B.; Wheeler, A. J.

    2007-12-01

    Cold-water coral carbonate mounds are complex geo-biological systems, originating from the interplay of hydrodynamic, sedimentological and biological factors. As changes in hydrodynamic and sedimentary regime are assumed to be amongst the main controls on mound evolution, reconstruction of the hydrodynamic and palaeoclimatic microenvironment on-mound, compared to the background environmental conditions (as seen off- mound), contributes to the fundamental understanding of these intriguing features and the development of a cold- water coral carbonate mound development model. Challenger Mound, one of the large cold-water coral carbonate mounds along the eastern Porcupine Seabight continental margin (NE Atlantic, SW off Ireland), was successfully drilled during IODP Expedition 307, providing the first complete recovery of a continuous sedimentary sequence through a carbonate mound. High-resolution particle size analysis of the terrigenous sediment component is used as primary proxy for reconstructing the hydrodynamic conditions during mound development. First results indicate repeated shifts in hydrodynamic conditions during sediment deposition on Challenger Mound, from lower-energetic conditions to higher-energetic environments and visa versa, which might reflect environmental variation over interglacial-glacial timescales throughout the whole mound development period. In conjunction with other available data, this dataset provides insight in local current regimes and sediment dynamics, the specific role of cold-water corals in these complex geo-biological systems and the differentiation of different sediment contributors to the coral mound system and its surroundings.

  • Biological validation of physical coastal waters classification along the NE Atlantic region based on rocky macroalgae distribution

    NASA Astrophysics Data System (ADS)

    Ramos, Elvira; Puente, Araceli; Juanes, José Antonio; Neto, João M.; Pedersen, Are; Bartsch, Inka; Scanlan, Clare; Wilkes, Robert; Van den Bergh, Erika; Ar Gall, Erwan; Melo, Ricardo

    2014-06-01

    A methodology to classify rocky shores along the North East Atlantic (NEA) region was developed. Previously, biotypes and the variability of environmental conditions within these were recognized based on abiotic data. A biological validation was required in order to support the ecological meaning of the physical typologies obtained. A database of intertidal macroalgae species occurring in the coastal area between Norway and the South Iberian Peninsula was generated. Semi-quantitative abundance data of the most representative macroalgal taxa were collected in three levels: common, rare or absent. Ordination and classification multivariate analyses revealed a clear latitudinal gradient in the distribution of macroalgae species resulting in two distinct groups: one northern and one southern group, separated at the coast of Brittany (France). In general, the results based on biological data coincided with the results based on physical characteristics. The ecological meaning of the coastal waters classification at a broad scale shown in this work demonstrates that it can be valuable as a practical tool for conservation and management purposes.

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