The effect of the "Prestige" oil spill on the plankton of the N-NW Spanish coast     

Varela M  Bode A  Lorenzo J  Alvarez-Ossorio MT  Miranda A  Patrocinio T  Anadón R  Viesca L  Rodríguez N  Valdés L  Cabal J  Urrutia A  García-Soto C  Rodríguez M  Alvarez-Salgado XA  Groom S 《Marine pollution bulletin》2006,53(5-7):272-286

Chlorophyll, primary production, zooplankton biomass and the species composition of phytoplankton and zooplankton were studied in 2003, after the Prestige shipwreck. The information obtained was compared to previous data series available for the area affected by the spill. A large data series on plankton variables for the N-NW Spanish coast existed, and therefore a realistic evaluation of the effects by comparison with the range of natural variability could be carried out. We emphasized the evaluation of impact during the spring bloom, the first important biological event after the spill. Some minor changes were observed occasionally, but they did not show any clear pattern and were more related to the natural variability of the ecosystem than to effect of the spill. Plankton community structure did not undergo any changes. Only a few species were more abundant during spring 2003 than in previous years. No significant changes were detected in the planktonic community during productive periods, such as the spring bloom and the summer blooms related to intrusions of East North Atlantic Central Waters. The lack of evidence of the effects of the spill on planktonic communities is discussed in terms of the characteristics of the fuel, the high dynamics of the water masses, the biological mechanisms through which the fuel from the surface waters is transferred to the sea floor and, particularly, the influence of the natural variability by means of large and meso-scale hydrographic processes in the area under study. At the present time it is not possible to determine any minor effects the spill may have had on the plankton owing to the great variability of the planktonic cycles and the short-term impact of the oil from the Prestige on the pelagic system.  相似文献   

A comparison of the sedimentary records of the 1960 and 2010 great Chilean earthquakes in 17 lakes: Implications for quantitative lacustrine palaeoseismology          下载免费PDF全文

Maarten Van Daele  Jasper Moernaut  Lindsey Doom  Evelien Boes  Karen Fontijn  Katrien Heirman  Willem Vandoorne  Dierk Hebbeln  Mario Pino  Roberto Urrutia  Robert Brümmer  Marc De Batist 《Sedimentology》2015,62(5):1466-1496

Seismically‐induced event deposits embedded in the sedimentary infill of lacustrine basins are highly useful for palaeoseismic reconstructions. Recent, well‐documented, great megathrust earthquakes provide an ideal opportunity to calibrate seismically‐induced event deposits for lakes with different characteristics and located in different settings. This study used 107 short sediment cores to investigate the sedimentary impact of the 1960 M_w 9·5 Valdivia and the 2010 M_w 8·8 Maule earthquakes in 17 lakes in South‐Central Chile (i.e. lakes Negra, Lo Encañado, Aculeo, Vichuquén, Laja, Villarrica, Calafquén, Pullinque, Pellaifa, Panguipulli, Neltume, Riñihue, Ranco, Maihue, Puyehue, Rupanco and Llanquihue). A combination of image analysis, magnetic susceptibility and grain‐size analysis allows identification of five types of seismically‐induced event deposits: (i) mass‐transport deposits; (ii) in situ deformations; (iii) lacustrine turbidites with a composition similar to the hemipelagic background sediments (lacustrine turbidites type 1); (iv) lacustrine turbidites with a composition different from the background sediments (lacustrine turbidites type 2) and (v) megaturbidites. These seismically‐induced event deposits were compared to local seismic intensities of the causative earthquakes, eyewitness reports, post‐earthquake observations, and vegetation and geomorphology of the catchment and the lake. Megaturbidites occur where lake seiches took place. Lacustrine turbidites type 2 can be the result of: (i) local near‐shore mass wasting; (ii) delta collapse; (iii) onshore landslides; (iv) debris flows or mudflows; or (v) fluvial reworking of landslide debris. On the contrary, lacustrine turbidites type 1 are the result of shallow mass wasting on sublacustrine slopes covered by hemipelagic sediments. Due to their more constrained origin, lacustrine turbidites type 1 are the most reliable type of seismically‐induced event deposits in quantitative palaeoseismology, because they are almost exclusively triggered by earthquake shaking. Moreover, they most sensitively record varying seismic shaking intensities. The number of lacustrine turbidites type 1 linearly increases with increasing seismic intensity, starting with no lacustrine turbidites type 1 at intensities between V½ and VI and reaching 100% when intensities are higher than VII½. Combining different types of seismically‐induced event deposits allows the reconstruction of the complete impact of an earthquake.  相似文献   

Multidirectional,synchronously‐triggered seismo‐turbidites and debrites revealed by X‐ray computed tomography (CT)     

Maarten Van Daele  Veerle Cnudde  Philippe Duyck  Mario Pino  Roberto Urrutia  Marc De Batist 《Sedimentology》2014,61(4):861-880

On 21 April 2007, a M_w 6·2 earthquake struck Aysén fjord (Chilean Patagonia) and caused onshore and offshore mass movements which triggered tsunamis and density flows in the fjord. To better understand the facies successions in, and the intercalation of, the density‐flow deposits, a study was made of the 2007 deposits in 22 short sediment cores taken in the inner Aysén fjord. By combining grain‐size analysis with X‐ray computed tomography scanning, it was possible to demonstrate that the encountered facies correspond to classical divisions of debrites and turbidites. The single‐event deposits consist of a succession of several sub‐deposits deposited under different flow directions and can be interpreted as stacked turbidites. Orientations of: (i) folds; (ii) imbricated mud clasts; (iii) backsets and foresets of climbing ripples; and (iv) asymmetrical convolute lamination were used to determine relative flow directions at the location of the cores. By assigning the basal flow of the stacked debrites and turbidites to the closest principal mass flow, the absolute flow directions of the sub‐deposits were determined which, in combination with multibeam basin‐floor morphology, allowed reconstruction of the 2007 density‐flow successions in Aysén fjord. Furthermore, alternating flow directions provide evidence for a seiche induced by the density flows. It was concluded that X‐ray computed tomography scans provide crucial information for reconstructing palaeoflows and can be a useful tool in marine and lacustrine sedimentology and palaeoseismology. The multidirectionality of sub‐deposits in turbidites is, next to differences in mineralogy, a new criterion to identify stacked turbidites. These multidirectional, stacked turbidites are an indication of simultaneous triggering of density flows and can therefore, in most cases, be attributed to earthquakes, ruling out other triggers, such as floods, storms or other sediment failures.  相似文献   

Age modeling of young non-varved lake sediments: methods and limits. Examples from two lakes in Central Chile     

Lucien von Gunten  Martin Grosjean  Jürg Beer  Philipp Grob  Arturo Morales  Roberto Urrutia 《Journal of Paleolimnology》2009,42(3):401-412

High-resolution and highly precise age models for recent lake sediments (last 100–150 years) are essential for quantitative paleoclimate research. These are particularly important for sedimentological and geochemical proxies, where transfer functions cannot be established and calibration must be based upon the relation of sedimentary records to instrumental data. High-precision dating for the calibration period is most critical as it determines directly the quality of the calibration statistics. Here, as an example, we compare radionuclide age models obtained on two high-elevation glacial lakes in the Central Chilean Andes (Laguna Negra: 33°38′S/70°08′W, 2,680 m a.s.l. and Laguna El Ocho: 34°02′S/70°19′W, 3,250 m a.s.l.). We show the different numerical models that produce accurate age-depth chronologies based on ²¹⁰Pb profiles, and we explain how to obtain reduced age-error bars at the bottom part of the profiles, i.e., typically around the end of the 19th century. In order to constrain the age models, we propose a method with five steps: (i) sampling at irregularly-spaced intervals for ²²⁶Ra, ²¹⁰Pb and ¹³⁷Cs depending on the stratigraphy and microfacies, (ii) a systematic comparison of numerical models for the calculation of ²¹⁰Pb-based age models: constant flux constant sedimentation (CFCS), constant initial concentration (CIC), constant rate of supply (CRS) and sediment isotope tomography (SIT), (iii) numerical constraining of the CRS and SIT models with the ¹³⁷Cs chronomarker of AD 1964 and, (iv) step-wise cross-validation with independent diagnostic environmental stratigraphic markers of known age (e.g., volcanic ash layer, historical flood and earthquakes). In both examples, we also use airborne pollutants such as spheroidal carbonaceous particles (reflecting the history of fossil fuel emissions), excess atmospheric Cu deposition (reflecting the production history of a large local Cu mine), and turbidites related to historical earthquakes. Our results show that the SIT model constrained with the ¹³⁷Cs AD 1964 peak performs best over the entire chronological profile (last 100–150 years) and yields the smallest standard deviations for the sediment ages. Such precision is critical for the calibration statistics, and ultimately, for the quality of the quantitative paleoclimate reconstruction. The systematic comparison of CRS and SIT models also helps to validate the robustness of the chronologies in different sections of the profile. Although surprisingly poorly known and under-explored in paleolimnological research, the SIT model has a great potential in paleoclimatological reconstructions based on lake sediments.  相似文献   

Peering inside the peak ring of the Chicxulub Impact Crater—its nature and formation mechanism     

Jaime Urrutia‐Fucugauchi  Ligia Prez‐Cruz  Joanna Morgan  Sean Gulick  Axel Wittmann  Johanna Lofi 《Geology Today》2019,35(2):68-72

The IODP‐ICDP Expedition 364 drilled into the Chicxulub crater, peering inside its well‐preserved peak ring. The borehole penetrated a sequence of post‐impact carbonates and a unit of suevites and clast‐poor impact melt rock at the top of the peak ring. Beneath this sequence, basement rocks cut by pre‐impact and impact dykes, with breccias and melt, were encountered at shallow depths. The basement rocks are fractured, shocked and uplifted, consistent with dynamic collapse, uplift and long‐distance transport of weakened material during collapse of the transient cavity and final crater formation.  相似文献   

Changes in sub-fossil chironomid assemblages in two Northern Patagonian lake systems associated with the occurrence of historical fires     

Alberto Araneda  Patricia Jana  Carolina Ortega  Fernando Torrejón  Sébastien Bertrand  Patricia Vargas  Nathalie Fagel  Denisse Alvarez  Alejandra Stehr  Roberto Urrutia 《Journal of Paleolimnology》2013,50(1):41-56

Patagonia is commonly seen as an exceptionally pristine area because of its wildlife and practically unpolluted waters. However, during the twentieth century the burning of natural forests was one of the most important human activities in Northern Chilean Patagonia. Some estimations indicate that three million hectares were burned during the first three decades of the century. Hence the objective of this study was to evaluate the impacts of the historical fires in Lake Burgos (45º42′S) and Lake Thompson (45º38′S) in Chilean Patagonia. The impact was measured by evaluating chironomid assemblage since they are sensitive enough to be used as an indicator of aquatic ecosystem health. Fires have a direct and drastic effect on a lake watershed but also indirectly affect a lake ecosystem, changing sedimentation patterns or increasing nutrient inputs. In the studied lakes the periods with higher prevalence of fires were identified by charcoal analysis, while organic matter and magnetic susceptibility allowed the confirmation of pre-fire and post-fire periods. The chironomid composition was evaluated through a PCA and an analysis of similarity (ANOSIM) to test the significance among periods while a Detrended Correspondence Analysis was applied to the chironomid assemblage downcore to assess compositional structure and taxa turnover. In Lake Burgos the ANOSIM test indicated significant differences between the pre-fire and fire periods (p < 0.05), while in Lake Thompson differences were not significant. However, in Lake Thompson the PCA clearly separated the pre-fire from the fire period but not the fire from the post-fire periods. In both lakes chironomid composition changed in relation to the period of higher prevalence of fires, which in turn implies catchment changes, pollution, and other anthropogenic impacts. Particularly a marked change in mesotrophic/eutrophic taxa was detected, reflecting an increase in nutrient input due to deforestation. Our findings point out that the lacustrine ecosystems are still affected by the impact of fires and the subsequent increase in nutrient supply that occurred almost 50 years ago. No sign of reverting to pre-disturbance conditions was observed, which makes these lakes highly sensitive to current human-induced impacts.  相似文献   

Textural and compositional controls on modern beach and dune sands,New Zealand     

J. J. Kasper‐Zubillaga  G. Ortiz‐Zamora  W. W. Dickinson  J. Urrutia‐Fucugauchi  A. M. Soler‐Arechalde 《地球表面变化过程与地形》2007,32(3):366-389

Textural, compositional, physical and geophysical determinations were carried out on 111 beach and dune sand samples from two areas in New Zealand: the Kapiti–Foxton coast sourced by terranes of andesite and greywackes and the Farewell Spit–Wharariki coast sourced by a wide variety of Paleozoic terranes. Our aim is to understand how long‐shore drift, beach width and source rock control the sedimentological and petrographic characteristics of beach and dune sands. Furthermore, this study shows the usefulness of specific minerals (quartz, plagioclase with magnetite inclusions, monomineralic opaque grains) to interpret the physical processes (fluvial discharges, long‐shore currents, winds) that distribute beach and dune sands in narrow and wide coastal plains. This was done by means of direct (grain size and modal analyses) and indirect (specific gravity, magnetic/non‐magnetic separations M/NM, magnetic susceptibility measurements, hysteresis loops) methods. Results are compared with beach sands from Hawaii, Oregon, the Spanish Mediterranean, Elba Island and Southern California. Compositionally, the Kapiti–Foxton sands are similar to first‐order immature sands, which retain their fluvial signature. This results from the high discharge of rivers and the narrow beaches that control the composition of the Kapiti–Foxton sands. The abundance of feldspar with magnetite inclusions controls the specific gravity of the Kapiti–Foxton sands due to their low content of opaque minerals and coarse grain size. Magnetic susceptibility of the sands is related mainly to the abundance of feldspars with Fe oxides, volcanic lithics and free‐opaque minerals. The Farewell Spit–Wharariki sands are slightly more mature than the Kapiti–Foxton sands. The composition of the Farewell Spit–Wharariki sands does not reflect accurately their provenance due to the prevalence of long‐shore drift, waves, little river input and a wide beach. Low abundance of feldspar with magnetite inclusions and free opaque grains produces poor correlations between specific gravity (Sg) and Fe oxide bearing minerals. The small correlation between opaque grains and M/NM may be related to grain size. The magnetic susceptibility of Farewell Spit–Wharariki sands is low due to the low content of grains with magnetite inclusions. Hysteresis and isothermal remnant magnetization (IRM) agree with the magnetic susceptibility values. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Changes in diatom, pollen, and chironomid assemblages in response to a recent volcanic event in Lake Galletué (Chilean Andes)     

Roberto Urrutia  Alberto Araneda  Fabiola Cruces  Laura Torres  Luis Chirinos  Hans C. Treutler  Nathalie Fagel  Sebastien Bertrand  Ingrid Alvial  Ricardo Barra  Emmanuel Chapron 《Limnologica》2007,37(1):49-62

Several lakes in Chile are near important volcanic areas where eruption impacts can limit the quality of lacustrine sediments for reconstructing past environmental changes. In this study, we report changes in diatoms, pollen, and chironomids assemblages after a tephra deposition in Lake Galletué (Chilean Andes). A sediment core obtained from Lake Galletué (40 m water depth) was sliced in 1 cm intervals and subsamples were taken to analyze each proxy. ²¹⁰Pb and ¹³⁷Cs activities were measured to obtain the geochronology and mineralogical analyses were performed to determine the mineral composition of the tephra. Diatom species composition and productivity were modified when the lake received the tephra; Aulacoseira granulata decreased and was later replaced by Cyclotella af. glomerata. After the tephra input, Aulacoseira granulata abundance increased to pre-disturbance levels and Cyclotella af. glomerata decreased. These changes seem to suggest a momentary increase in lake nutrient levels after the tephra deposition. Chironomid assemblages also decreased in head capsules just after the tephra deposition, but the most important change was the replacement of Ablabesmyia by Parakiefferiella, probably due to the sedimentological changes produced by the input of coarse tephra grains. Furthermore, unlike other studies, chironomid assemblages in Lake Galletué did not show a decrease drastically in diversity within the tephra layer. The pollen analysis indicated that, prior to the volcanic event, the vegetal community was dominated by Nothofagus sp., Araucaria araucana, and Blechnum sp.-type. After the tephra deposition, the same taxa are dominant, indicating that the volcanic event seems not produce changes in the vegetation. Nevertheless, within the tephra layer it is possible to see an increase in Poaceae, which represent – due to the percolation process – the effect of eruption on the vegetation. According to our results, diatoms were the most sensitive proxy for describing the changes produced by tephra deposition into the aquatic ecosystem and, despite the noticeable changes in its sedimentological properties; the lake seems to have a high resilience capacity, allowing it to return to pre-tephra input conditions.  相似文献   

Palaeointensity determination and K—Ar dating of the Tertiary north-east Jalisco volcanics (Mexico)     

J. Urrutia Fucugauchi 《Geophysical Journal International》1980,63(3):601-618

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Sixteen samples representing eight Tertiary volcanic units from north-east Jalisco, Mexico were studied in an attempt to estimate the palaeointensity of the Earth's magnetic field. The experimental technique used was similar to that proposed by Shaw (1974) and an attempt was made to incorporate further criteria using the directional behaviour of the NRM, TRM and two ARMs during the af treatment and measuring the rate of ARM acquisition before and after heating. The directional information was used for checking the stability of all remanent magnetizations involved and for correcting the ARM test values. In addition the TRM directional behaviour could be a valuable yet simple test to detect the problem of insufficient heating. The use of the ARM acquisition test in the palaeointensity determination permits the full investigation of the coercive force spectrum and could lead to a more reliable palaeointensity method. This combined ARM method was applied to one sample. Further work is needed to understand the NRM—ARM1 and TRM—ARM2 relationships if the ARM tests are to be used for correcting TRM alteration effects. Whole rock K—Ar age determinations were carried out on samples from four selected units. Ten samples, representing six of the units, are considered to yield reliable palaeointensity values. Mean values were computed for each unit and reduced to the palaeoequator. The mean palaeoequatorial values and K—Ar ages determined are: I (13 |Mp 2 Myr), 0.504 Oe; II, 0.453 Oe; III, 0.439 Oe; VI (52 |Mp 10 Myr), 0.074 Oe; VII (14 |Mp 2 Myr), 0.187 Oe and VIII (12 |Mp 2 Myr), 0.251 Oe. These results agree reasonably well with those from previous studies. A large number of palaeointensity estimations, many more than currently available, are required to obtain an average estimate of the behaviour of the Earth's magnetic field during the Tertiary.  相似文献   

Ex post analysis of engineered tsunami mitigation measures in the town of Dichato,Chile     

Oportus  Maximiliano  Cienfuegos  Rodrigo  Urrutia  Alejandro  Aránguiz  Rafael  Catalán  Patricio A.  Hube  Matías A. 《Natural Hazards》2020,103(1):367-406

Natural Hazards - Due to Chile’s notorious and frequent seismic activity, earthquake- and tsunami-related studies have become a priority in the interest of developing effective...  相似文献