The coccolithophore summer–autumn assemblage in the upwelling waters of Portugal: Patterns of mesoscale distribution (1985–2005)     

M.T. Moita  A. SilvaS. Palma  M.G. Vilarinho 《Estuarine, Coastal and Shelf Science》2010

A study of the mesoscale distribution of phytoplankton communities observed along the Portuguese upwelling coast in 1985–1986 made it possible to identify an assemblage composed by the coccolithophores Helicosphaera carteri, Syracosphaera pulchra and Coronosphaera mediterranea. The assemblage was consistently present in the coast in the following years (1991, 1992, 1994, 2003 and 2005) and from 1992 onwards, Rhabdosphaera clavigera was recognised as being part of it, although in low concentrations During late summer, this group of species showed higher affinities with upwelling waters of subtropical origin (ENACWst) on the SW coast. At the end of the upwelling season, in autumn, the assemblage was advected to the NW shelf due to the intensification of the poleward surface circulation or meridional seasonal changes of environmental conditions. The species maximum abundances were not coincident in space: H. carteri developed at the central part of the western coast while blooms of S. pulchra and C. mediterranea generally occurred further south, such as at the upwelling centre of cape S. Vicente. Syracosphaera pulchra blooms were characterised by lower concentrations of C. mediterranea and vice-versa. The above patterns were recurrent along the years but the relative abundance of each species appeared related to the interannual variability of physical conditions as the upwelling.  相似文献   

Comment: Tephrochronological dating of varved interglacial lake deposits from Piànico‐Sèllere (Southern Alps,Italy) to around 400 ka. Achim Brauer,Sabine Wulf,Clara Mangili and Andrea Moscariello Journal of Quaternary Science 22: 85–96     

Daniele L. Pinti  Virgile Rouchon  Xavier Quidelleur  Pierre‐Yves Gillot  Sergio Chiesa  Cesare Ravazzi 《第四纪科学杂志》2007,22(4):411-414

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How Does Large Flaring Activity from the Same Active Region Produce Oppositely Directed Magnetic Clouds?     

Louise K. Harra  Nancy U. Crooker  Cristina H. Mandrini  Lidia van Driel-Gesztelyi  Sergio Dasso  Jingxiu Wang  Heather Elliott  Gemma Attrill  Bernard V. Jackson  Mario M. Bisi 《Solar physics》2007,244(1-2):95-114

We describe the interplanetary coronal mass ejections (ICMEs) that occurred as a result of a series of solar flares and eruptions from 4 to 8 November 2004. Two ICMEs/magnetic clouds occurring from these events had opposite magnetic orientations. This was despite the fact that the major flares related to these events occurred within the same active region that maintained the same magnetic configuration. The solar events include a wide array of activities: flares, trans-equatorial coronal loop disappearance and reformation, trans-equatorial filament eruption, and coronal hole interaction. The first major ICME/magnetic cloud was predominantly related to the active region 10696 eruption. The second major ICME/magnetic cloud was found to be consistent with the magnetic orientation of an erupting trans-equatorial filament or else a rotation of 160° of a flux rope in the active region. We discuss these possibilities and emphasize the importance of understanding the magnetic evolution of the solar source region before we can begin to predict geoeffective events with any accuracy.  相似文献   

3D soft-sediment deformation structures: evidence for Quaternary seismicity in the Madrid basin, Spain     

Pablo G. Silva  Juan C. Cañaveras  Sergio Sanchez-Moral  Javier Lario  Enrique Sanz 《地学学报》1997,9(5-6):208-212

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North Atlantic oscillation control of droughts in north-east Spain: evaluation since 1600 a.d.     

Sergio M. Vicente-Serrano  José M. Cuadrat 《Climatic change》2007,85(3-4):357-379

This paper analyses the role played by the North Atlantic Oscillation (NAO) in the creation of drought conditions in a semi-arid region of north-east Spain (the middle Ebro valley), from 1600 to the year 2000. The study used documents from ecclesiastical archives for the seventeenth, eighteenth and nineteenth centuries. For the twentieth century, instrumental precipitation records were used as well. A December–August drought index from 1600 to 1900 was compiled from the historical documentary sources (rogation ceremonies). The index was validated by means of precipitation records between 1858 and 1900 and independent precipitation data from 1600 reconstructed by means of dendrochronological records. Using instrumental data a drought index was also calculated (Standardized Precipitation Index, SPI) for the 1958–2000 period. We found that the NAO was important in explaining the droughts identified in the study area from documents and instrumental data. Positive values of the winter NAO index are prone to cause droughts in the middle Ebro valley. This finding has been verified since 1600 by means of two independent reconstructions of the winter NAO index. The same behaviour has been observed during the nineteenth and twentieth centuries by means of instrumental records. The climatic and geographic factors that explain the high influence of North Atlantic Oscillation on droughts in this region are discussed in depth.  相似文献   

A parametric approach to the slope of the globular clusters giant branches     

Vittorio Castellani  Daniele Palma 《Astrophysics and Space Science》1977,47(1):217-223

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Giant versus small porphyry copper deposits of Cenozoic age in northern Chile: adakitic versus normal calc-alkaline magmatism   总被引：63，自引：0，他引：63  

Roberto Oyarzun  Alvaro Márquez  Javier Lillo  Ivan López  Sergio Rivera 《Mineralium Deposita》2001,36(8):794-798

Cenozoic magmatic activity in northern Chile led to the formation of two contrasting porphyry copper belts: (1) a Paleocene-Early Eocene belt comprising small porphyry copper deposits (e.g., Lomas Bayas) of normal calc-alkaline affinity; and (2) a Late Eocene-Early Oligocene belt hosting huge porphyry copper deposits (e.g., Chuquicamata) of adakitic affinity. Although the first belt comprises both volcanic and plutonic rocks (andesitic-basaltic and rhyolitic lavas and tuffs, and associated sub-volcanic porphyries and felsic stocks), the latter only includes intrusions (mostly granodioritic types, including porphyry copper deposits). We suggest that the Late Eocene-Early Oligocene belt formed when fast and oblique convergence between the South America and Farallon plates led to flat subduction and direct melting of the subducting plate, hence giving rise to plutonic rocks of adakitic affinity. The absence of volcanism, under prevailing compressional conditions, prevented the escape of SO₂ from the adakitic, sulfur-rich, highly oxidized magmas ("closed porphyry system"), which allowed formation of huge mineral deposits. On the contrary, coeval volcanic activity during formation of the Paleocene-Early Eocene calc-alkaline porphyries allowed development of "open systems", hence to outgassing, and therefore, to small mineral deposits.  相似文献   

Ammonia observations of the nearby molecular cloud MBM 12     

José F. Gómez  Joaquín Trapero  Sergio Pascual  Nimesh Patel  Carmen Morales  José M. Torrelles 《Monthly notices of the Royal Astronomical Society》2000,314(4):743-746

We present NH₃(1,1) and (2,2) observations of MBM 12, the closest known molecular cloud (65-pc distance), aimed at finding evidence for on-going star formation processes. No local temperature (with a T _rot upper limit of 12 K) or linewidth enhancement is found, which suggests that the area of the cloud that we have mapped (15-arcmin size) is not currently forming stars. Therefore this nearby 'starless' molecular gas region is an ideal laboratory to study the physical conditions preceding new star formation.
A radio continuum source has been found in Very Large Array archive data, close to but outside the NH₃ emission. This source is likely to be a background object.  相似文献   

Impact of the 6 April 2009 L'Aquila earthquake on groundwater flow in the Gran Sasso carbonate aquifer,Central Italy     

Antonella Amoruso  Luca Crescentini  Marco Petitta  Sergio Rusi  Marco Tallini 《水文研究》2011,25(11):1754-1764

The Mw = 6·3 L'Aquila earthquake on 6 April 2009 produced a mainshock that caused significant changes in the hydrogeology of the Gran Sasso carbonate fractured aquifer: (i) the sudden disappearance at the time of the mainshock of some springs located exactly along the surface trace of the Paganica normal fault (PF); (ii) an immediate increase in the discharge of the Gran Sasso highway tunnel drainages and of other springs and (iii) a progressive increase of the water table elevation at the boundary of the Gran Sasso aquifer during the following months. Using the data collected since the 1990s that include aftershock monitoring as well as data regarding spring discharge, water table elevations, turbidity and rainfall events, a conceptual model of the earthquake's consequences on the Gran Sasso aquifer is proposed herein. In this model that excludes the contribution of seasonal recharge, the short‐term hydrologic effects registered immediately after the mainshock are determined to have been caused by a pore pressure increase related to aquifer deformation. Mid‐term effects observed in the months following the mainshock suggest that there was a change in groundwater hydrodynamics. Supplementary groundwater that flows towards aquifer boundaries and springs in discharge areas reflects a possible increase in hydraulic conductivity in the recharge area, nearby the earthquake fault zone. This increase can be attributed to fracture clearing and/or dilatancy. Simulations by numerical modelling, related to pore pressure and permeability changes with time, show results in accordance with observed field data, supporting the conceptual model and confirming the processes that influenced the answer of the Gran Sasso aquifer to the L'Aquila earthquake. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Tephrochronology of recent events in the Andean Range (northern Patagonia): spatial distribution and provenance of lacustrine ash layers in the Nahuel Huapi National Park     

Romina Daga  Sergio Ribeiro Guevara  M. Lidia Sánchez  María Arribére 《第四纪科学杂志》2010,25(7):1113-1123

Tephrochronology is a powerful tool for dating sedimentary sequences, especially in Patagonia, where a large number of active volcanoes have produced frequent historical eruptions. Short lacustrine sedimentary sequences were extracted from the lakes Moreno Oeste and Ton?ek (Nahuel Huapi National Park). Seventeen volcanic ash layers were identified in both cores, ²¹⁰Pb and ¹³⁷Cs were used for dating techniques, and historical volcanic records were employed for correlation. White pumice and glass shards from the tephras were characterised by measuring major and trace element contents by instrumental neutron activation analysis. Two volcanic sources – the Cordón Caulle and the Calbuco volcanoes – were recognised as the prevailing systems that impacted the area in the past 800–1000 a. The Calbuco volcano was mainly responsible for the nine tephras identified in the Lake Ton?ek sequence. Four of these nine tephras also contained material from the Cordón Caulle complex, and could be interpreted as composite tephras or possible reworked ones. The Calbuco volcano showed predominant influences in the Lake Moreno Oeste sequence. Six of the eight tephras identified in such a sequence were from the Calbuco volcano, and three of these six contained material from the Cordón Caulle complex. The other two were from the Cordón Caulle complex, with contributions from the Calbuco volcano in one of them. These findings show that the high frequency of volcanic events in the study region demands an accurate characterisation of the products generated by each source, as well as an evaluation of their spatial distribution, to obtain a consistent framework for dating recent environmental changes. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献