Larger foraminifera distribution and strontium isotope stratigraphy of the La Cova limestones (Coniacian–Santonian, “Serra del Montsec”, Pyrenees, NE Spain)     

Carme Boix  Gianluca Frijia  Vicent Vicedo  Josep M. Bernaus  Matteo Di Lucia  Mariano Parente  Esmeralda Caus 《Cretaceous Research》2011,32(6):806-822

The Upper Cretaceous La Cova limestones (southern Pyrenees, Spain) host a rich and diverse larger foraminiferal fauna, which represents the first diversification of K-strategists after the mass extinction at the Cenomanian–Turonian boundary.The stratigraphic distribution of the main taxa of larger foraminifera defines two assemblages. The first assemblage is characterised by the first appearance of lacazinids (Pseudolacazina loeblichi) and meandropsinids (Eofallotia simplex), by the large agglutinated Montsechiana montsechiensis, and by several species of complex rotalids (Rotorbinella campaniola, Iberorotalia reicheli, Orbitokhatina wondersmitti and Calcarinella schaubi). The second assemblage is defined by the appearance of Lacazina pyrenaica, Palandrosina taxyae and Martiguesia cyclamminiformis.A late Coniacian-early Santonian age was so far accepted for the La Cova limestones, based on indirect correlation with deep-water facies bearing planktic foraminifers of the Dicarinella concavata zone. Strontium isotope stratigraphy, based on many samples of pristine biotic calcite of rudists and ostreids, indicates that the La Cova limestones span from the early Coniacian to the early-middle Santonian boundary. The first assemblage of larger foraminifera appears very close to the early-middle Coniacian boundary and reaches its full diversity by the middle Coniacian. The originations defining the second assemblage are dated as earliest Santonian: they represent important bioevents to define the Coniacian-Santonian boundary in the shallow-water facies of the South Pyrenean province.By means of the calibration of strontium isotope stratigraphy to the Geological Time Scale, the larger foraminiferal assemblages of the La Cova limestones can be correlated to the standard biozonal scheme of ammonites, planktonic foraminifers and calcareous nannoplankton. This correlation is a first step toward a larger foraminifera standard biozonation for Upper Cretaceous carbonate platform facies.  相似文献   

Land-use and vegetation-cover mapping of an indigenous land area in the state of Mato Grosso (Brazil) based on spectral linear mixing model,segmentation and region classification     

Fernando Shinji Kawakubo  Rubia Gomes Morato  Carmen Lucia Midaglia  Maria Lucia Cereda Gomide  Ailton Luchiari 《国际地球制图》2013,28(2):165-175

A spectral linear-mixing model using Landsat ETM+ imagery was undertaken to estimate fraction images of green vegetation, soil and shade in an indigenous land area in the state of Mato Grosso in the central-western region of Brazil. The fraction images were used to classify different types of land use and vegetation cover. The fraction images were classified by the following two methods: (a) application of a segmentation based on the region-growing technique; and (b) grouping of the regions segmented using the per-region unsupervised classifier named ISOSEG. Adopting a 75% threshold, ISOSEG generated 44 clusters that were grouped into eight land-use and vegetation-cover classes. The mapping achieved an average accuracy of 83%, showing that the methodology is efficient in mapping areas of great land-use and vegetation-cover diversity, such as that found in the Brazilian cerrado (savanna).  相似文献   

Outflow Velocity Structure in the Upper Transition Region and Corona     

Alan Gabriel  Lucia Abbo 《Solar physics》2012,280(2):435-443

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Heterogeneity,cyclicity and diagenesis in a Mississippian brachiopod shell of palaeoequatorial Britain     

Lucia Angiolini  Michael Stephenson  Melanie J. Leng  Flavio Jadoul  Dave Millward  Anthony Aldridge  Julian Andrews  Simon Chenery  Gareth Williams 《地学学报》2012,24(1):16-26

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Tracer hydrology of the data-scarce and heterogeneous Central American Isthmus     

Ricardo Sánchez-Murillo  Germain Esquivel-Hernández  José L. Corrales-Salazar  Laura Castro-Chacón  Ana M. Durán-Quesada  Manuel Guerrero-Hernández  Valeria Delgado  Javier Barberena  Katia Montenegro-Rayo  Heyddy Calderón  Carlos Chevez  Tania Peña-Paz  Saúl García-Santos  Pedro Ortiz-Roque  Yaneth Alvarado-Callejas  Laura Benegas  Antonio Hernández-Antonio  Marcela Matamoros-Ortega  Lucia Ortega  Stefan Terzer-Wassmuth 《水文研究》2020,34(11):2660-2675

Numerous socio-economic activities depend on the seasonal rainfall and groundwater recharge cycle across the Central American Isthmus. Population growth and unregulated land use changes resulted in extensive surface water pollution and a large dependency on groundwater resources. This work combines stable isotope variations in rainfall, surface water, and groundwater of Costa Rica, Nicaragua, El Salvador, and Honduras to develop a regionalized rainfall isoscape, isotopic lapse rates, spatial–temporal isotopic variations, and air mass back trajectories determining potential mean recharge elevations, moisture circulation patterns, and surface water–groundwater interactions. Intra-seasonal rainfall modes resulted in two isotopically depleted incursions (W-shaped isotopic pattern) during the wet season and two enriched pulses during the mid-summer drought and the months of the strongest trade winds. Notable isotopic sub-cloud fractionation and near-surface secondary evaporation were identified as common denominators within the Central American Dry Corridor. Groundwater and surface water isotope ratios depicted the strong orographic separation into the Caribbean and Pacific domains, mainly induced by the governing moisture transport from the Caribbean Sea, complex rainfall producing systems across the N-S mountain range, and the subsequent mixing with local evapotranspiration, and, to a lesser degree, the eastern Pacific Ocean fluxes. Groundwater recharge was characterized by (a) depleted recharge in highland areas (72.3%), (b) rapid recharge via preferential flow paths (13.1%), and enriched recharge due to near-surface secondary fractionation (14.6%). Median recharge elevation ranged from 1,104 to 1,979 m a.s.l. These results are intended to enhance forest conservation practices, inform water protection regulations, and facilitate water security and sustainability planning in the Central American Isthmus.  相似文献   

Insights into eruption dynamics from textural analysis: the case of the May, 2008, Chaitén eruption     

Fabrizio Alfano  Costanza Bonadonna  Lucia Gurioli 《Bulletin of Volcanology》2012,74(9):2095-2108

The May, 2008, Chaitén (southern Chile) eruption was characterized by several explosive events, each associated with plumes which reached up to about 19?km above sea level on May 6. A study of the textural and physical features of the juvenile clasts erupted during the climactic phase of the 2008 eruption of Chaitén is presented. Pumice clasts show unimodal density distribution (main mode at 600?kg/m³), average vesicularity of about 69?%, a glassy groundmass with no microcrystals, and vesicles with dimension between ～1?μm and ～2?mm. They also show a unimodal vesicle size distribution with most frequent vesicle size in the range 0.05–0.08?mm and an estimated vesicle number density of 1.3?±?0.5?×?10⁵?mm^?3 related to a rapid nucleation event produced during the late phases of magma rise. This is confirmed by the absence of microcrystals that could otherwise have delayed vesicle formation and allowed the magma to maintain a low viscosity and a supersaturation in volatiles. Vesiculation and fragmentation were triggered by a sudden decompression of the melt associated with the opening of the volcanic conduit (～10?MPa?s^?1).  相似文献   

Geoarchaeological sea-level proxies from a silted up harbour: A case study of the Roman colony of Luni (northern Tyrrhenian Sea, Italy)     

Monica Bini  Alessandro Chelli  Anna Maria Durante  Lucia Gervasini  Marta Pappalardo   《Quaternary International》2009,206(1-2):147

The Luni Plain, which faces the northern Tyrrhenian Sea, underwent major landscape changes over the last 3000 years. The coastline shifted south and west, separating the ruins of the ancient Roman colony of Luni (founded in 177 BC) from the sea by means of a new coastal plain. The precise location of the coastline during the main settlement phase as well as during the city's decline has never been established, although partial and qualitative scenarios have been suggested by various authors. According to these authors, an indentation of the coastline west of the city formed a major water basin, along the shores of which traces of pre-Roman settlements exist; near the city, two minor basins were present, suitable for hosting harbour structures. The city of Luni was famed for its harbour (Portus Lunae), from which the marbles quarried in the Apuan Alps, used to build many of the monuments in Rome, were delivered. The traces of its port, however, are scattered and uncertain.Newly available subsurface data are presented, associated with a revision of unpublished archaeological evidence of the ancient city topography. Progress in palaeoenvironmental reconstructions at Luni has been possible thanks to the collection and analysis of ancient and recent cores, supported by radiocarbon dates, as well as the interpretation of archaeological findings suitable as markers for sea-level recognition. The main environmental changes in the area have been refined: since a few centuries before the colony was founded, the Luni plain had been characterized by a complex architecture of swamps and marshes limited by dune ridges and fluvial sand bars. The positions of these landforms were not fixed, but shifted, mainly depending on the spatial relationship between the coastline and the river mouths.Determining the precise position of the Roman coastline is useful to constrain the area in which archaeological surveys should be concentrated in order to identify the harbour location. Moreover, some of these results have been used to infer altitude constraints on the sea-level position in Roman times: preliminary data are shown for constructing a Late Holocene local sea-level curve in the area.  相似文献   

Water management for irrigation,crop yield and social attitudes: a socio-agricultural agent-based model to explore a collective action problem     

Lucia Tamburino  Giuliano Di Baldassarre 《水文科学杂志》2020,65(11):1815-1829

ABSTRACT

When rainfall does not meet crop water requirements, supplemental irrigation is needed to maintain productivity. On-farm ponds can prevent excessive groundwater exploitation – to the benefit of the whole community – but they reduce the cultivated area and require investments by each farmer. Thus, choosing the source of water for irrigation (groundwater vs on-farm pond) is a problem of collective action. An agent-based model is developed to simulate a smallholder farming system; the farmers’ long-/short-view orientation determines the choice of the water source. We identify the most beneficial water source for economic gain and its stability, and how it can change across communities and under future climate scenarios. By using on-farm ponds, long-view-oriented farmers provide collective advantages but have individual advantages only under extreme climates; a tragedy of the commons is always possible. Changes in farmers’ attitudes (and hence sources of water) based on previous experiences can worsen the economic outcome.  相似文献   

The use of predictive modeling techniques for optimal exploitation of spatial databases: a case study in landslide hazard mapping with expert system-like methods   总被引：5，自引：0，他引：5  

Alberto Pistocchi  Lucia Luzi  Paola Napolitano 《Environmental Geology》2002,41(7):765-775

. A case study is presented in which different probabilistic prediction models (Bayesian probability, fuzzy logic "and", "or", "sum", "product", "gamma" operations, and certainty factors) are used to produce landslide hazard maps for a hilly and mountainous region in the northern Apennines, Italy. Seven data layers are exploited to detect most vulnerable areas: lithology, distance from the geological lineaments, annual rainfall amount, land cover type, topographic slope and aspect, and the distance from hydrographic network segments. The results of the different predictions are compared using the prediction rate index and critically discussed, to evaluate the possibility of using readily available databases for land planning.  相似文献   

Anisotropy of magnetic susceptibility studies of depositional processes in the Campanian Ignimbrite,Italy     

Michael H. Ort  Giovanni Orsi  Lucia Pappalardo  Richard V. Fisher 《Bulletin of Volcanology》2003,65(1):55-72

The late Pleistocene trachytic Campanian Ignimbrite underlies much of the Campanian Plain near Naples, Italy, and occurs in valleys in the mountainous area surrounding the plain out to about 80 km from its source, the Campi Flegrei caldera. At sites within 15 km of the Campi Flegrei, anisotropy of magnetic susceptibility (AMS) principal directions indicate that, in the absence of significant topography, deposition came from a flow moving in a roughly radial direction. AMS studies of the more distal ignimbrite reveal downhill and/or downvalley flow directions prior to deposition, even where these directions are at high angles to a generally radial transport direction from the vent. On the flanks of Roccamonfina Volcano, flow was directly downhill, as if the source of the ignimbrite was the summit of the volcano. In most localities, the ignimbrite consists of a single massive deposit. In a few localities in the Apennine Mountains, however, the confluence of multiple drainage systems off mountains resulted in multiple local flow units that cannot be correlated between valleys. A detailed study of the ignimbrite in the flat Titerno River valley near Massa shows that the AMS fabrics are not due to late-stage creeping during deposition or compaction. Well-defined, but non-parallel AMS fabrics from vertical and lateral sections in the Massa area are best explained by the merging of gravity currents flowing down the valley and steep valley sides to form a single aggradational deposit. Clast compositions and AMS axes at Mondragone indicate that the pyroclastic flow encountered the Monte Massico massif and was partially blocked, so that flow during deposition was toward the Campi Flegrei. Similar AMS data from sites along the edge of the Campanian Plain indicate back-flow off the first ridge of the Apennine Mountains reached at least 5 km from their base. The Campanian Ignimbrite was deposited from a density-stratified pyroclastic flow. The depositional system consisted of the lower, denser portion of the current, and was controlled by topography. The grouping of the AMS axes is interpreted to indicate that deposition occurred under laminar flow conditions.  相似文献