Sedimentological and ichnological signatures of changes in wave,river and tidal influence along a Neogene tropical deltaic shoreline     

LUIS A. BUATOIS  NUBIA SANTIAGO  MEYLIN HERRERA  PIRET PLINK‐BJÖRKLUND  RON STEEL  MARÍA ESPIN  KAOLU PARRA 《Sedimentology》2012,59(5):1568-1612

Analysis of Neogene cores from the Eastern Venezuela Basin along 65 km of a west–east trending shoreline allows characterization of the sedimentological and ichnological signatures of wave, river and tidal processes. The area displays deltas prograding northward from the Guyana Shield. Twenty‐three facies are defined and grouped into four categories (wave‐influenced, river‐influenced, tide‐influenced and basinal). Wave‐dominated deltaic deposits occur mostly in the Tácata Field. The delta plain was characterized by tide‐influenced distributary channels separated by interdistributary bays. Fluvial discharge in the delta front and prodelta was repeatedly interrupted by storm‐wave reworking and suspended sediment fallout. Delta‐front and prodelta deposits contain some ichnotaxa that typically do not occur in brackish water (for example, Chondrites and Phycosiphon). Amalgamated storm deposits are unburrowed or contain vertical Ophiomorpha. Lateral (especially on the updrift side) to the river mouths, waves caused nearly continuous accretion of the associated strandplains. These deposits are the most intensely bioturbated, and are dominated by the estenohaline echinoid‐generated ichnogenus Scolicia. River‐dominated deltaic deposits are present in the Santa Bárbara, Mulata, Carito and El Furrial Fields. Low‐sinuosity rivers characterized the alluvial plain, whereas the subaerial delta plain was occupied by higher‐sinuosity rivers. The subaqueous delta plain includes distributary channels and tide‐influenced interdistributary bays. Further seaward, successions are characterized by terminal distributary‐channel and distributary mouth‐bar deposits, as well as by delta‐front and prodelta deposits showing evidence of sediment gravity‐flow and fluid‐mud emplacement. Delta‐front and prodelta deposits are unbioturbated to sparsely bioturbated, suggesting extreme stress, mostly as a result of high fluvial discharge and generation of sediment gravity flows. Tidal influence is restricted to interdistributary bays, lagoons and some distributary channels. From an ichnological perspective, and in order of decreasing stress levels, four main depositional settings are identified: river‐dominated deltas, tide‐influenced delta plains, wave‐dominated deltas and wave‐dominated strandplain–offshore complexes.  相似文献   

The 2011 submarine volcanic eruption in El Hierro (Canary Islands)   总被引：1，自引：0，他引：1  

Juan Carlos Carracedo  Francisco Pérez Torrado  Alejandro Rodríguez González  Vicente Soler  José Luis Fernández Turiel  Valentin R. Troll  Sebastian Wiesmaier 《Geology Today》2012,28(2):53-58

Forty years after the Teneguía Volcano (La Palma, 1971), a submarine eruption took place off the town of La Restinga, south of El Hierro, the smallest and youngest island of the Canarian Archipelago. Precursors allowed an early detection of the event and its approximate location, suggesting it was submarine. Uncertainties derived from insufficient scientific information available to the authorities during the eruption, leading to disproportionate civil protection measures, which had an impact on the island's economy—based primarily on tourism—while residents experienced extra fear and distress.  相似文献   

Rotational atmospheric circulation during North Atlantic-European winter: the influence of ENSO     

J. Garc��a-Serrano  B. Rodr��guez-Fonseca  I. Blad��  P. Zurita-Gotor  A. de la C��mara 《Climate Dynamics》2011,37(9-10):1727-1743

The dominant variability modes of the North Atlantic-European rotational flow are examined by applying a principal component analysis (PCA/EOF) to the 200?hPa streamfunction mid-winter anomalies (Jan?CFeb monthly means). The results reveal that, when this norm is used, the leading mode (EOF1) does not correspond to the traditional North Atlantic Oscillation (NAO, which appears in our analysis as the second leading mode, EOF2) but is the local manifestation of the leading hemispheric streamfunction EOF. The regression of this regional mode onto the global SST field exhibits a clear El Ni?o signature, with no signal over the Atlantic, while the associated upper height anomalies resemble the Tropical/Northern Hemisphere (TNH) pattern. East of North America, this TNH-like wavetrain produces a meridional dipole-like pattern at lower levels. Although in some ways this pattern resembles the NAO (EOF2), the dynamics of these two modes are very different in that only EOF2 is associated with a latitudinal shift of the North Atlantic stormtrack. Thus, the choice of the streamfunction norm in the EOF analysis allows the separation of two different phenomena that can produce similar dipolar surface pressure anomalies over the North Atlantic but that have different impact on European climate. These two modes also differ on their contribution to variability at lower levels: while NAO-EOF2 is mostly confined to the North Atlantic, TNH-EOF1 has a more annular, global character. At upper levels NAO-EOF2 also produces a global pattern but with no annular structure, reminiscent of the ??circumglobal?? teleconnection.  相似文献   

Response of single benthic metrics and multi-metric methods to anthropogenic pressure gradients, in five distinct European coastal and transitional ecosystems   总被引：4，自引：0，他引：4  

Borja A  Barbone E  Basset A  Borgersen G  Brkljacic M  Elliott M  Garmendia JM  Marques JC  Mazik K  Muxika I  Magalhães Neto J  Norling K  Rodríguez JG  Rosati I  Rygg B  Teixeira H  Trayanova A 《Marine pollution bulletin》2011,62(3):499-513

In recent times many benthic indices have been proposed to assess the ecological quality of marine waters worldwide. In this study we compared single metrics and multi-metric methods to assess coastal and transitional benthic status along human pressure gradients in five distinct environments across Europe: Varna bay and lake (Bulgaria), Lesina lagoon (Italy), Mondego estuary (Portugal), Basque coast (Spain) and Oslofjord (Norway). Hence, 13 single metrics (abundance, number of taxa, and several diversity and sensitivity indices) and eight of the most common indices used within the European Water Framework Directive (WFD) for benthic assessment were selected: index of size spectra (ISS), Benthic assessment tool (BAT), Norwegian quality index (NQI), Multivariate AMBI (M-AMBI), Benthic quality index (BQI), (Benthic ecosystem quality index (BEQI), Benthic index based on taxonomic sufficiency (BITS), and infaunal quality index (IQI). Within each system, sampling sites were ordered in an increasing pressure gradient according to a preliminary classification based on professional judgement. The different indices are largely consistent in their response to pressure gradient, except in some particular cases (i.e. BITS, in all cases, or ISS when a low number of individuals is present). Inconsistencies between indicator responses were most pronounced in transitional waters (i.e. IQI, BEQI), highlighting the difficulties of the generic application of indicators to all marine, estuarine and lagoonal environments. However, some of the single (i.e. ecological groups approach, diversity, richness) and multi-metric methods (i.e. BAT, M-AMBI, NQI) were able to detect such gradients both in transitional and coastal environments, being these multi-metric methods more consistent in the detection than single indices. This study highlights the importance of survey design and good reference conditions for some indicators. The agreement observed between different methodologies and their ability to detect quality trends across distinct environments constitutes a promising result for the implementation of the WFD’s monitoring plans. Moreover, these results have management implications, regarding the dangers of misclassification, uncertainty in the assessment, use of conflicting indices, and testing and validation of indices.  相似文献   

Trace elements in Holocene sediments of the southern Doñana National Park (SW Spain): historical pollution and applications     

M. I. Carretero  M. Pozo  F. Ruiz  J. Rodríguez Vidal  L. M. Cáceres  M. Abad  J. M. Muñoz  F. Gómez  J. M. Campos  M. L. González-Regalado  M. Olías 《Environmental Earth Sciences》2011,64(5):1215-1223

The multidisciplinary analysis of core sediments from Doñana National Park, south Spain, permits to delimitate both the paleoenvironmental changes and the geochemical evolution of this area during the Holocene. In a first phase (10–6.5 kyr cal), this area was occupied by freshwater/brackish marshes with periodical alternation of dry periods and humid intervals. In a second phase, these marshes were inundated during the Flandrian transgression (~6.5 kyr cal), with the deposition of bioclastic sands. The third phase (6.5–3.6 kyr cal) is characterized by the transition to an old lagoon, with unpolluted, bottom sediments. The geochemical concentrations of these clayey sediments can be used as a geochemical background for present-day and future environmental evaluations of this area. In the following 600 years approximately, two tsunamis caused the partial infilling of this area with bioclastic, marine sediments. In the interval comprised between these two tsunamis, this lagoon was polluted with heavy metals derived from historical mining activities. This environmental contamination represents one of the oldest evidences of mining pollution in the world (>3 kyr cal BP).  相似文献   

The study of metal contamination in urban topsoils of Mexico City using GIS   总被引：1，自引：0，他引：1  

María Teresa Rodríguez-Salazar  Ofelia Morton-Bermea  Elizabeth Hernández-Álvarez  Rufino Lozano  Victor Tapia-Cruz 《Environmental Earth Sciences》2011,62(5):899-905

This research presents and discusses information concerning the spatial distribution of heavy metals (Pb, Cu, Zn, Ba, Co, Cr, Ni and V) in the urban environments of Mexico City using geographical information system and statistical analysis. Superficial soil samples (n = 146) were analyzed. The highest contamination indices were found in the north and center zone of the metropolitan area. In contrast, the surrounding rural fields show a lower impact grade. The higher concentrations of Pb, Cu, Zn and Ba were observed as being related to high vehicular traffic, nevertheless other elements such as Co, Cr, Ni and V do not show anthropogenic influence and their content can be attributed to the parental rock. The results are compared with previous surveys carried out in 2003 in order to evaluate temporal deposition trends. No changes were found on reported concentrations except for Cu and Zn, whose concentration has increased in later years. The results suggest that spatial distribution analysis and results in comparison with previous studies could be useful for the management and sustainable development of the metropolitan area of Mexico City.  相似文献   

Ichnological data as a useful tool for deep-sea environmental characterization: a brief overview and an application to recognition of small-scale oxygenation changes during the Cenomanian�CTuronian anoxic event     

Francisco J. Rodr��guez-Tovar  Alfred Uchman 《Geo-Marine Letters》2011,31(5-6):525-536

The oceanic anoxic event at the Cenomanian?CTuronian transition (OAE-2) is a worldwide phenomenon related with variations in atmosphere?Cocean dynamics. This event coincides with significant changes in the palaeoenvironment determining marine mass extinction affecting numerous groups of organisms. Ichnological analysis of the Cenomanian?CTuronian boundary interval has been conducted in three selected sections from different ecological and depositional settings in the western Tethys. Indeed, a brief overview of existing knowledge in this domain highlights increasing recognition of the usefulness of trace fossils in the characterization of even minor-scale deep-sea environmental changes linked to sea-level dynamics. At the study sites, variations in ichnological features, including trace fossil composition, tiering patterns and ichnofabrics, can be related to fluctuations in bottom- and pore-water oxygenation during the Cenomanian?CTuronian interval. In the Barnasiówka section (Polish Outer Carpathians), changes between oxic/dysoxic??characterized by Chondrites, Planolites and even Thalassinoides??and euxinic conditions, without trace fossils or only with Chondrites, can be explained by variations in gravity flows influencing the benthic habitat. In the El Chorro and Hedionda sections (Betic Cordillera), longer anoxic intervals during the OAE-2, characterized by the absence of trace fossils, are interrupted by shorter dysaerobic and aerobic sub-events associated with Chondrites, Palaeophycus, Planolites, Thalassinoides, Trichichnus and Zoophycos, but showing significant differences between these two sections related to the palaeogeographically differentiated influence of upwelling conditions.  相似文献   

RESTORATION OF SHEEP TRANSHUMANCE IN THE EBRO VALLEY,ARAGON, SPAIN*     

PATRICK O'FLANAGAN  TEODORO LASANTA MARTÍNEZ  MARÍA PAZ ERREA ABAD 《Geographical review》2011,101(4):556-575

For centuries, sheep transhumance has connected the Spanish highlands with the lowlands, creating a livestock system with important social, economic, cultural, and landscape effects. About 5 million sheep were involved in transhumant movements in the mid‐1700s, but transhumance started to decay in the nineteenth century and almost disappeared in the 1970s and 1980s. In the 1980s, transhumant sheep did not number more than 25,000 in the study area; at present the number exceeds 134,000, with herders practicing both descending and ascending transhumance. In this article we provide information not only on current numbers of transhumant sheep but also on the origins and destinations of the flocks. We also confirm that the reputation of transhumance, once regarded as quaint and antiquated, has been enhanced by the ecosystem services it provides and by the cultural and heritage continuities it renders.  相似文献   

Mississippian coral assemblages from the Khenifra area,Central Morocco: Biostratigraphy,biofacies, palaeoecology and palaeobiogeography     

Ismail Said  Ian D. Somerville  Sergio Rodríguez  Pedro Cózar 《Gondwana Research》2013,23(1):367-379

Analysis of Mississippian coral assemblages from the Khenifra region of Central Morocco together with data from foraminiferal/algal microfossils has established new age dating of 5 localities within the Azrou–Khenifra Basin: Souk El Had and Sidi Lamine, where corals occur mainly in biostromes protected by oolitic shoals, Tabainout, where corals have been recorded in different environments related to microbial mounds, Alhajra Almatkouba, where corals occur in biostromal reworked beds and Tiouinine, where corals occur in a well structured, fringing reef. This study demonstrates the presence of richer more diverse coral assemblages than previously recorded, in a variety of environmental settings. These coral assemblages strengthen correlations with the Adarouch area in the NE part of the Azrou–Khenifra Basin. It is emphasised that in the upper Viséan there are close similarities with rugose coral assemblages in other parts of the Western Palaeotethys including North Africa, SW Spain and NW Europe, and that all belong to the same biogeographic province.  相似文献   

Hydrogeological research on intensively exploited deep aquifers in the ‘Loma de Úbeda’ area (Jaén, southern Spain)     

Antonio González-Ramón  Javier Rodríguez-Arévalo  Sergio Martos-Rosillo  Javier Gollonet 《Hydrogeology Journal》2013,21(4):887-903

The intensive use of groundwater for irrigation in the area of Úbeda (‘Loma de Úbeda’, Jaén, southern Spain) has transformed an area of traditionally rain-fed dry farmland into fields with some of the highest olive oil productivity in the world. Early hydrogeological research studies, initiated just after the beginning of the groundwater exploitation, revealed that the water was collected from three different overlapping aquifers occupying an area of over 1,100 km², with the lower aquifers located at depths from 300 to over 700 m in an area of 440 km². Multidisciplinary research, based on geological characterization, and piezometric, hydrochemical and isotopic data, has led to a conceptual model of functioning in this complex hydrogeological system. The proposed model allows for the identification of the recharge areas, and the discharge, which is at present mainly associated with the groundwater pumping. Areas of mixing of waters from the different aquifers and the main hydrogeochemical processes affecting groundwater quality are described.  相似文献