119,150 research outputs found
Reply to Shanmugam, G., Comment on Internal Waves, an Underexplored Source of Turbulence Events in the Sedimentary Record by Pomar Et Al. [Earth-Science Reviews, 111 (2012), 56-81], Earth Science Reviews (2012)
No full textShanmugam (2012) just published a criticism about the study of
Pomar et al. (2012) on the potential importance of internal waves
in shaping the sedimentary record in lakes and oceans. We would
like to acknowledge the effort done by G. Shanmugam for initiating
such a discussion. However, while scientific debates and controversies are necessary for the advancement of science in general, and for sedimentology in particular, they should be carried out with coherence and rigor to be constructive. Unfortunately, Shanmugam's comment appears to us not to follow this logic such that it is difficult for us to reply in a sensible manner
Characterization of upslope migrating cross-bedded deposits in a carbonate ramp (Upper Miocene, Menorca, Balearic Islands, Spain)
No full textMenorca is subdivided in main regions with different stratigraphic and tectonic characteristics. To the north, folded, thrusted and faulted Paleozoic, Mesozoic and Paleogene rocks compose the Tramuntana region. To the south, upper-Miocene carbonate and, locally, siliciclastic rocks compose the Migjorn region. Upper Miocene rocks unconformably overlie Paleozoic to middle Miocene basement. In the Migjorn, three Miocene depositional units were recognized (Pomar et al., 2002 and references herein): the Basal Conglomeratic Unit (Burdigalian p.p.), interpreted as near-shore to fan-delta deposits; the Lower Bar Unit (early Tortonian), interpreted as a distally steepened carbonate ramp; the Reef Complex (upper Tortonian - lower Messinian), a reef-rimmed platform prograding complex. Within the ramp, Pomar et al. (2002) distinguished four facies belts: fan-delta conglomerates and bioturbated packstones (inner ramp), crossbedded grainstones (middle- ramp), rhodolithic rudstone clinobeds (ramp slope) and fine-grained wackestone-packstone with planktonic foraminifers (outer ramp). The cross-bedded units here analysed occur at the transition lower slope-outer ramp. They infill the axial depression of large slide/slump scars. These scars truncate the gently, 10°-12° basinward dipping, slope-to-outer ramp succession.
The wedge-shaped cross-bedded units, 10-12m thick, pinch out basinward and extend laterally for tens of meters. Several amalgamated cross-laminated bodies, 40cm- to 2m wide each with erosive base compose each unit.
They are composed by rhodolithic-mollusk rudstone with coarse grain/packstone matrix. Porosity is very high, cementation low and dolomitization patchy. Matrix consists of red-algal-, bivalve-, echinoderm, coral fragments, and benthic foraminifers. Ooids are, locally abundant along with limestone pebbles. Pebbles are flat, 5- to 10-cm wide, of oolitic grainstone, sometimes with mollusk borings. Cross bedding is underlined by the abundance and orientation of coarser components. Cross-laminae within units dip upslope (8° to 35°) forming backstepping backsets. Upslope bedform migration has been explained as forming when a supercritical flow encounters a local obstruction (or a local break on the slope), and a hydraulic jump may occur within the flow, upcurrent from the obstruction. Sediment will be therefore deposited at the obstruction forming an up-flow-dipping slipface that will tend to accrete and migrate in the upflow direction. In Menorca, these sedimentary structures have been interpreted by Pomar et al. (2002), as backset beds related to up-stream migrating hydraulic jump where slide scars acted as slope channels funneling platform debris down the slope.
The occurrence of aragonitic components (oolites, corals) within these units, absent in the ramp system, and the scars development at the end of the ramp progradation, suggest the involvement of Reef Complex sediment. Therefore, those events, involved both sediment of the upper Tortonian distally steepened ramp and part of the Reef Complex.
These structures have been mostly described in different environments of terrigenous systems. In carbonate systems are scarcely described and none from carbonate ramps. The architecture characterizing these upslope cross-bedded beds seams to call for a scour-and-fill process, therefore initially the action of a strong scouring event immediately followed by depositional events. The presence of these bodies in various intervals suggests the repetitive occurrence of this process.
In the studied system, deep-scouring events on the platform could be represented by slope failures that induced tsunami events or by eustatic variations, able to create strong downslope flows directed offshore. Scours have been rapidly infilled by shallow-water sediment
Internal waves vs. surface storm waves: a review on the origin of hummocky cross-stratification
No full textHummocky cross-stratification (HCS) is considered a diagnostic structure of surface storm activity at the shoreface–offshore transition. However, the origin of HCS is still debated. Laboratory experiments have not yet reproduced it and direct observations on the continental shelves do not exist. Most hydrodynamic interpretations invoke pure oscillatory flows, unidirectional-dominated combined flows and oscillatory-dominated flows, but they all share the assumption of HCS to reflect the combined action of surface storm waves and related currents. Within this context of uncertainties, internal waves (gravity waves propagating along the pycnocline) provide an alternative mechanism to explain the origin of HCS. Internal waves breaking on the shelf create episodic high-turbulence events and induce upslope- and downslope currents as well as oscillatory flows at the depth where the pycnocline intersects the sea floor. In this scenario, both the oscillatory- and the unidirectional components needed for HCS to form are not necessarily linked to surface storm waves, but can occur at various depth as far and near there is a pycnocline where internal waves can for
The Calcarenite di Gravina Formation in Matera (Southern Italy): new insights for coarse-grained, large-scale, crossbedded bodies encased in offshore deposits
No full textExcellent outcrops of the upper Pliocene-lower Pleistocene Calcarenite di Gravina around Matera (southern Italy) provide continuous exposure of coarse-grained, clastic basin-margin, shoreline to offshore facies. Among these facies, the most conspicuous and volumetrically important are the transition-slope deposits that form large-scale, high-angle, cross-bedded lithosomes. These are laterally extensive, parallel with the paleoshoreline, and show seaward progradation. We interpret them to represent avalanches of sediment swept out onto a depositional slope, below wave base, from the shoreface zone by storm waves and wind-driven currents. Three types of building blocks are recognized based on bedding patterns and facies architecture: embryonic parasequences, mature parasequences, and simple sequences. Parasequences formed during stillstands of sea level and simple sequences during high-frequency cycles of relative change of sea level. These building blocks are stacked in a backstepping configuration and onlap onto Cretaceous limestone substrate. Backstepping is believed to be due to a tectonically forced transgression that is punctuated by high-frequency cycles of sea level. Modern analogs for these building blocks are the Holocene prograding prisms detected in high-resolution seismic lines of the Mediterranean shelves. The reflection patterns of these seismic units resemble the bedding architecture of the Matera simple sequences and parasequences and show similarities of shape, size, position, and orientation of coastal setting, and direction of progradation. Comparison of the Holocene prisms and the Pliocene-Pleistocene accretional units in Matera indicates that they may represent the same genetic process, progradation of clastic prisms below the wave base level. The Matera accretional units also show similarities with other examples of laterally extensive, large-scale, cross-bedded sand bodies encased in offshore deposits, such as some sandbanks. Differentiating between these laterally extensive and seaward-prograding cross-bedded sand bodies and some coarse-grained Gilbert-type deltas is difficult, however, if interpretations are based only on two-dimensional (2-D) outcrops in dip section. Without high-resolution data it is also difficult to distinguish between transition-slope and prograding shoreface lithosomes. This difficulty may be acute where only seismic or well-log data are available; however, certain other architectural characteristics, such as stacking and preservation of facies belts and position of bounding surfaces, as well as differences in associated sedimentary structures and fossil content, may be used for interpretation. The Matera example provides a mechanism for emplacement in offshore settings of elongate and strandline-parallel sand and gravel deposits that prograde seaward and that preserve a coarsening-upward internal succession. This article offers an interpretation for other ancient examples of large-scale, cross-bedded lithosomes encased in offshore deposits
Fontes de nitrogênio e manejo de plantas espontâneas em pomar de macieira
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Agrárias, Programa de Pós-Graduação em Agroecossistemas, Florianópolis, 2015.O Estado de Santa Catarina (SC) é o segundo maior produtor de maçãs do Brasil. Normalmente, o nitrogênio (N) é fornecido às maciei-ras na forma de ureia. Porém, outras fontes de N, como a ureia peletiza-da e a cama sobreposta de suínos podem liberar o nutriente mais lenta-mente no solo, potencializando a absorção pelas plantas, o que pode me-lhorar o estado nutricional e até afetar positivamente a produção, bem como reduzir a perda de N por lixiviação. Além disso, nos pomares de SC, as plantas espontâneas são dessecadas ou roçadas na linha de plan-tio, para diminuir a competição por água e nutrientes com as macieiras. Porém, é possível que em pomares adultos em produção não aconteça essa competição, não afetando negativamente o estado nutricional e produção das macieiras. Assim, pode não ser necessária nem a roçada ou dessecamento das plantas espontâneas. O crescimento das plantas es-pontâneas nos pomares pode diminuir a lixiviação de N e melhor os a-tributos químicos do solo. O trabalho objetivou (a) avaliar o teor de N total em folhas, a produção e o fluxo de N no solo e na solução, em po-mar de macieira com a aplicação de distintas fontes de N, (b) avaliar o estado nutricional, a produtividade de maçã, o fluxo de N no solo e na solução lixiviada, e os atributos químicos do solo, em pomar de maciei-ras com diferentes manejos de plantas espontâneas. O Estudo 1 foi inti-tulado produção e N no solo e na solução em pomar de macieira subme-tido à aplicação de fontes de nutrientes. O experimento foi instalado em Urubici (SC). As macieiras foram submetidas à aplicação de 33 kg de N ha-1 na forma de ureia, ureia peletizada e cama sobreposta de suínos; ha-vendo ainda um tratamento sem aplicação de N. O Estudo 2 foi intitula-do nutrição, produtividade e atributos químicos do solo, em pomar de macieira sob manejo de plantas espontâneas. O experimento foi implan-tado em um pomar em Urubici (SC). Os tratamentos foram manejos de plantas espontâneas: sem manejo das plantas espontâneas (SM), desse-camento das plantas espontâneas na linha de plantio (DL), roçada das plantas espontâneas na linha de plantio (RL) e roçada das plantas espon-tâneas na linha e entrelinha de plantio (RLE). No Estudo 1 e 2 foram a-valiados os teores de nutrientes nas folhas e mensurado o diâmetro do caule e a produção de frutos. Foram coletadas amostras de solo e de so-lução, e analisados os teores de N-NH4+ e N-NO3- ao longo de duas sa-fras no Estudo 1 e três safras no Estudo 2. Além disso, no Estudo 2 fo-ram abertas trincheiras e coletado nas camadas de 0-0,025, 0,025-0,05, 0,05-0,10, 0,10-0,15 0,15-0,20 e 0,20-0,4 m, após 24 meses da instala-ção do experimento. No Estudo 1 a aplicação de cama sobreposta de su-ínos, ureia e ureia peletizada em macieiras aumentou a produção de fru-tos na segunda safra avaliada, mas o teor de N total nas folhas não foi afetado. A aplicação de fontes de N no solo afetou o fluxo de formas do nutriente no solo e na solução ao longo do ciclo da macieira, com pe-quenos incrementos em períodos próximos às aplicações das diferentes fontes de N ao solo. No Estudo 2 observou-se que os diferentes manejos das plantas espontâneas não afetaram a produtividade, o crescimento das macieiras e pouco alteraram o teor de nutrientes nas folhas e nas cama-das de solo. Assim, as plantas espontâneas nas linhas de plantio e entre-linhas não necessitam ser manejadas nem com roçadas ou uso de herbi-cidas, para evitar a competição por água e nutrientes com as macieiras. Os maiores teores de N-NO3- e, por consequência, de N mineral tende-ram a ser observados na solução lixiviada no solo com dessecamento das plantas espontâneas na linha de plantio, o que pode potencializar a contaminação de águas sub-superficiais.Abstract : The state of Santa Catarina (SC) is the second largest producer of apples in Brazil. Typically, nitrogen (N) is supplied to the apple trees in urea form. However, other N sources such as pelletized urea and pig deep litter can slowly release the nutrient in the soil, enhancing the ab-sorption from the apple tree, which can improve the nutritional status and even affect positively the production and reduce the loss of N leach-ing. In addition, the SC orchards, the spontaneous plants are discarded or desiccation on row to reduce competition for water and nutrients to plants. However, it is possible that in adults orchards in production might not happen this competition, not adversely affecting the nutrition-al status and production of apple trees. So it may not be necessary mow-ing or desiccation of weeds. The growth of weeds in orchards can re-duce the leaching of N and better soil chemical attributes. Two studies were conducted. The study aimed to (a) evaluate the total N content in leaves, the production and the nitrogen flow in the soil and solution in apple orchard with the application of different sources of N, (b) evaluate the nutritional status, apple productivity, N flow in soil and leach solu-tion, and soil chemical properties in apple orchard with different man-agement of weeds. Study 1 corresponded: Production and nitrogen in soil and solution in apple orchard submitted to the application of nutri-ent sources. The experiment was in Urubici (SC). The apple trees were subjected to application of 33 kg N ha-1 as urea form, pelletized urea and pig deep litter; there was a treatment without application of N. Study 2 was titled: Nutrition, productivity and soil chemical attributes in apple orchard under management of weeds. The experiment was installed in an orchard in Urubici (SC). The treatments were different management of weeds: without management of weeds, desiccation of weeds in the rows, mowing of weeds in the row and mowing of weeds in the row and interrows. The study 1 and 2 was evaluated the levels of nutrients in the leaves and measured the diameter of the stem and fruit production. Soil and solution were collected and analyzed the content of NH4+-N and NO3--N over two seasons in Study 1 and three harvests in Study 2. In addition, in Study 2 were open trenches and collected in layers 0-0.025, 0.025-0.05, 0.05-0.10, 0.10-0.15, 0.15-0.20 e 0,20-0,4 m after 24 months of the experiment installation. The results obtained in Study 1 show that the pig deep litter application, urea and pelletized urea on ap-ples tree increased fruit production in the second season, but the total N content in leaves was not affected. The N sources in the soil affected the flow of the nutrient in the soil and solution over apple cycle, with smallincrements in near periods of the application of different nitrogen sources in the soil. The Study 2 showed that the different managements of weeds did not affect productivity, growth of apple tree and little changed the nutrient content in leaves and soil layers. Therefore, weeds in the rows and interrow need not be managed either with mowing or use of herbicides, to avoid competition for nutrients and water to the ap-ple trees. The highest levels of nitrate and, therefore, mineral C tended to be observed in the leach solution whit the desiccation of the weeds in the row, which can enhance the subsurface contamination of water
Atributos físicos de cambissolo húmico submetido a fontes de nitrogênio e manejo de plantas espotâneas em pomar de macieira
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Agrárias, Programa de Pós-Graduação em Agroecossistemas, Florianópolis, 2015.Santa Catarina é o segundo maior produtor de maçã do Brasil. Estudos sobre diferentes fontes de nitrogênio (N) e manejo de plantas espontâneas vêm sendo realizados em pomares de maçã em Urubici, SC, com enfoque no aspecto químico do solo. Porém, o uso agrícola, os diferentes manejos de adubação e da cobertura do solo também interferem na sua estruturação física, podendo afetar a conservação do solo e reduzir a produtividade das culturas, interferindo ou influenciando os atributos edáficos e a relação solo-planta. O objetivo do trabalho foi avaliar os atributos físicos de Cambissolo em pomar de macieira em Urubici, SC, submetido a diferentes fontes de adubação nitrogenada e manejo de plantas espontâneas. Os tratamentos foram aplicados durante 2011-2013, compondo dois experimentos, a saber - (1) Fontes de adubação nitrogenada, com os seguintes tratamentos: testemunha, ureia comum, ureia peletizada e adubação orgânica (cama sobreposta de suínos); e (2) Manejo de plantas espontâneas, com os seguintes tratamentos: testemunha (sem manejo das espontâneas), dessecagem e roçada. Foram coletadas amostras indeformadas de solo nas camadas de 0-5, 5-10, 10-15 e 15-20 cm, nas quais foram avaliados a condutividade hidráulica saturada (CH); densidade do solo (Ds); resistência do solo à penetração; porosidade  total, macro, meso e microporos; índices de agregação do solo  diâmetro médio aritmético e geométrico dos agregados secos ao ar e estáveis em água (DMAsa, DMAea, DMGsa, DMGea, respectivamente); índice de estabilidade de agregados (IEADMA e IEADMG) e umidade volumétrica. O uso da adubação orgânica com cama sobreposta de suínos aumentou a porosidade total, a microporosidade, os agregados estáveis em água (4-2 mm), o DMGsa, a umidade volumétrica e diminuiu a Ds em comparação aos demais tratamentos na camada de 0-5 cm. O uso da adubação orgânica ou da ureia comum não alterou a macroporosidade e resistência à penetração, porém esses tratamentos apresentaram menor macroporosidade em relação à testemunha e resistência a penetração em relação à ureia peletizada. As fontes de N aumentaram o DMAea, DMGea e o IEADMA em comparação à testemunha. O manejo das plantas espontâneas com roçada ou dessecagem aumentou a Ds em profundidade (15-20 cm) e diminuiu a quantidade de agregados secos ao ar da classe de 2  1 mm quando comparados com a testemunha. O manejo com a roçada foi responsável por apresentar a maior quantidade de agregados estáveis em água na classe >4,0 mm e o IEADMG, enquanto a dessecagem contribui para a maior quantidade de agregados estáveis em água na classe <0,5 mm e o menor IEADMG. O manejo com a dessecagem diminuiu o DMAea (0-10 cm), IEADMA (0-5 cm), DMGea (5-10 cm) e reduziu em 15% a condutividade hidráulica do solo
Rhodolith assemblages from the lower Tortonian carbonate ramp of Menorca (Spain): Environmental and paleoclimatic implications
No full textLower Tortonian distally steepened carbonate ramp of Menorca mostly consists of foramol and rhodalgal facies deposited in inner-middle ramp, ramp slope and outer ramp settings. Red algae are abundant from the middle ramp to the lower part of the slope and their taxonomic assemblages are clearly related to the bathymetric position. Melobesioids percentage increases basinward, passing from 55.8% in the middle ramp to 97% in the toe of slope. Mastophoroids are more abundant in the middle ramp (43.1%) and decrease toward deeper paleoenvironments (1.2%). Lithophylloids and sporolithaceans appear as accessory components from the middle ramp to slope settings. The percentage of melobesioids and mastophoroids observed in the middle ramp suggest that growth of the rhodoliths started in a water depth below 10–20 m. The deepest occurrence of the rhodoliths is in the ramp slope environment, where the dominance of melobesioids and the low percentage of shallower-water subfamily suggests a water depth range of 70 to 100 m. Shape and structure of rhodoliths are indicative of high-energy conditions in all ramp settings and they do not reflect a decrease in hydrodynamic energy related to water depth increase. These conditions are related to the presence of unidirectional currents that produced cross-bedded grainstones existing in the middle ramp, ramp slope and at the toe of the ramp slope settings. The high percentage of mastophoroids in the shallowest environments and the presence of Lithoporella and Sporolithon in the coralline assemblages suggests that carbonate production took place in tropical waters
Reseña del libro "Educación, historia y sociedad. El legado historiográfico de Antonio Viñao" de Pedro L. Moreno Martínez (Editor)
No full textEditor: Pedro L. Moreno Martínez
Editorial: Tirant lo Blanch, Valencia
Año de edición: octubre 2018, primera edición
Páginas: 455
Formato papel: Tapa blanda, 15 x 21 cm.
ISBN papel: 9788417203771
Ebook: 9788417203788
Dep Legal: B-19019-2016
Autor de la reseña: Pilar Cancer Pomar[1]
[1] Catedrática de E. Secundaria y miembro de Fedicaria, Zaragoza (España).
Architectural complexity of a carbonate transgressive systems tract induced by basement physiography
No full textThree-dimensional exposure of the Plio-Pleistocene Calcarenite di Gravina Formation around Matera Horst, Italy, permits analysis of the architecture and internal complexities of carbonate sedimentary bodies around a palaeoisland. Spatial organization of the different lithosomes, along with their skeletal composition, sedimentary structures and bedding patterns, helps decipher the key factors that controlled platform architecture and distribution of heterogeneities: basement physiography, type and loci of carbonate production, bottom currents and changes in accommodation. Relative sea-level changes resulted from high-frequency glacioeustatic cycles that punctuated an overall tectonically induced transgression. Topographic relief, fragmentation of the limestone basement and wave energy controlled lithoclastic supply. Basement physiography and relative sea-level changes determined the area available for carbonate-producing biotas, and thus the amount and type of skeletal sediments. On the moderately dipping south-western margin, waves and associated currents re-distributed the lithoclasts derived from coastal abrasion. Bioclasts mostly derived from epiphytic seaweed production in the shoreface. Infralittoral prisms resulted from downdip transport (progradation) and longshore transport, which controlled along strike continuity of the prisms. Where basement continuity was interrupted at the margin of the palaeoisland, a lithoclastic fan was deposited from dumping sediments carried by shore-parallel currents. Fan-shaped skeletal bodies coalesced to form an apron on the steeper northern side of the palaeoisland, when a structural platform was flooded and epiphytic carbonates were shed. Red algae contribution depended on the available oligophotic area which, in turn, was controlled by high-frequency sea-level cycles, basement physiography and apron aggradation. The internal architecture of this apron resembles a low stand wedge but it accumulated during transgression. Deeper-water, contour-parallel currents formed a lithosome at the foot of the structural relief. Interpreted as drift deposits, it is composed of shallow-water benthonic skeletal components, planktonic foraminifera and some limeclasts
Foramol, rhodalgal and bryomol sediments are not necessarily temperate-water carbonates.
No full text- …
