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1.
Juliano Kuchle Claiton Marlon dos Santos Scherer Christian Correa Born Renata dos Santos Alvarenga Felipe Adegas 《Journal of South American Earth Sciences》2011,31(4):358-371
The Dom João Stage comprises an interval with variable thickness between 100 and 1200 m, composed of fluvial, eolian and lacustrine deposits of Late Jurassic age, based mainly on the lacustrine ostracod fauna (although the top deposits may extend into the Early Cretaceous). These deposits comprise the so-called Afro-Brazilian Depression, initially characterized as containing the Brotas Group of the Recôncavo Basin (which includes the Aliança and the Sergi Formations) and subsequently extended into the Tucano, Jatobá, Camamu, Almada, Sergipe, Alagoas and Araripe Basins in northeastern Brazil, encompassing the study area of this paper. The large occurrence area of the Dom João Stage gives rise to discussions about the depositional connectivity between the basins, and the real extension of sedimentation. In the first studies of this stratigraphic interval, the Dom João Stage was strictly associated with the rift phase, as an initial stage (decades of 1960–70), but subsequent analyses considered the Dom João as an intracratonic basin or pre-rift phase – without any relation to the active mechanics of a tectonic syn-rift phase (decades of 1980–2000). The present work developed an evolutionary stratigraphic and tectonic model, based on the characterization of depositional sequences, internal flooding surfaces, depositional systems arrangement and paleoflow directions. Several outcrops on the onshore basins were used to build composite sections of each basin, comprising facies, architectural elements, depositional systems, stratigraphic and lithostratigraphic frameworks, and paleocurrents. In addition to that, over a hundred onshore and offshore exploration wells were used (only 21 of which are showed) to map the depositional sequences and generate correlation sections. These show the characteristics and relations of the Dom João Stage in each studied basin, and they were also extended to the Gabon Basin. The results indicate that there were two main phases during the Dom João Stage, in which distinctive sedimentary environments were developed, reflecting depositional system arrangements, paleoflow directions were diverse, and continuous or compartmented basins were developed. 相似文献
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The presence of matter in its different forms in a hexadimensional space-time, where gravitation is coupled to a conformal field, generates a class of cosmological solutions with very peculiar features: the initial proper distance between any two points of the space-time is infinite, following successive contraction and expansion phases in the evolution of the Universe. This behaviour defines a Anti-Big Bang Singular Cosmology. In this article we analyze this primordial cosmological scenario considering different matter forms and the effects of a Conformal Transformation on the metric. 相似文献
3.
Wang Qing Yamaguchi Ryan T. Kalogiros John A. Daniels Zachary Alappattu Denny P. Jonsson Haflidi Alvarenga Oswaldo Olson Alex Wauer Benjamin J. Ortiz-Suslow David G. Fernando Harindra Joseph 《Boundary-Layer Meteorology》2021,181(2-3):267-292
Boundary-Layer Meteorology - A total of 15 fog events from two field campaigns are investigated: the High Energy Laser in Fog (HELFOG) project (central California) and the Toward Improving Coastal... 相似文献
4.
John Bershaw Carmala N. Garzione Pennilyn Higgins Bruce J. MacFadden Frederico Anaya Herculano Alvarenga 《Earth and Planetary Science Letters》2010,289(3-4):530-538
Paleoelevation constraints from fossil leaf physiognomy and stable isotopes of sedimentary carbonate suggest that significant surface uplift of the northern Andean plateau, on the order of 2.5 ± 1 km, occurred between ～ 10.3 and 6.4 Ma. Independent spatial and temporal constraints on paleoelevation and paleoclimate of both the northern and southern plateau are important for understanding the distribution of rapid surface uplift and its relation to climate evolution across the plateau. This study focuses on teeth from modern and extinct mammal taxa (including notoungulates, pyrotheres, and litopterns) spanning ～ 29 Ma to present, collected from the Altiplano and Eastern Cordillera of Bolivia (16.2°S to 21.4°S), and lowland Brazil. Tooth enamel of large, water-dependent mammals preserves a record of surface water isotopes and the type of plants that animals ingested while their teeth were mineralizing. Previous studies have shown that the δ18O of modern precipitation and surface waters decrease systematically with increasing elevations across the central Andes. Our results from high elevation sites between 3600 and 4100 m show substantially more positive δ18O values for late Oligocene tooth samples compared to < 10 Ma tooth δ18O values. Late Oligocene teeth collected from low elevation sites in southeast Brazil show δ18O values similar (within 2‰) to contemporaneous teeth collected at high elevation in the Eastern Cordillera. This affirms that the Andean plateau was at a very low elevation during the late Oligocene. Late Oligocene teeth from the northern Eastern Cordillera also yield consistent δ13C values of about ? 9‰, indicating that the environment was semi-arid at that time. Latitudinal gradients in δ18O values of late Miocene to Pliocene fossil teeth are similar to modern values for large mammals, suggesting that by ～ 8 Ma in the northern Altiplano and by ～ 3.6 Ma in the southern Altiplano, both regions had reached high elevation and established a latitudinal rainfall gradient similar to modern. 相似文献
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6.
Post-Brasiliano (Pan-African) high-K granitic magmatism in Central Brazil: the role of late Precambrian-early Palaeozoic extension 总被引：1，自引：0，他引：1
In western Goiás, Brazil, the emplacement of large, high-K postorogenic granites and associated small gabbro-dioritic intrusions, followed immediately after the last deformational events of the Brasiliano-Pan-African orogeny at 600 Ma. Well-fitted whole-rock Rb---Sr isochrons indicate ages which suggest two discrete intrusive events: the older between 588 and 560 Ma and the younger between 508 and 485 Ma. The older granites display general petrographic and geochemical characteristics of highly differentiated calc-alkaline I-type granitoids, whereas the younger intrusions are more alkaline, similar to A-type granites.Initial 87Sr/86Sr ratios vary from 0.703 to 0.710 and initial Nd isotope ratios yield εNd(T) values in the range between −4.0 and +3.0. There are no major differences in initial isotopic compositions between the two granite groups, suggesting that the parental magmas for both groups of rocks mostly originated by refusion of crustal sources isotopically similar to the 940-640 Ma basement arc-type metatonalites-metagranodiorites and associated arc metavolcanics.The major and trace element compositional differences between the two granite groups is explained in terms of modifications in the melting conditions within the crust, with younger melts being produced by the refusion of anhydrous, depleted crustal sources left after the extraction of previous batches of more hydrated calc-alkaline magmas. The heat input required to promote extensive remelting of the continental crust was, most likely, provided by mantle-derived mafic magmas that invaded and probably underplated the crust, during uplift and extension.The two intrusive events are bimodal in nature and are interpreted as shallow-level extension-related events associated with regional uplift and denudation occurring just after two orogenic pulses at the end of the Proterozoic and early Palaeozoic, the older at 600 Ma and the younger between 550 and 510 Ma. The onset of the granite magmatism at 590 Ma, shortly post-dating the Brasiliano orogeny (600 Ma), is broadly coeval with the initial stages of sedimentation of the terrigenous and carbonatic rocks of the ensialic Paraguay Belt in Brazil and its correlative in Bolivia, the Tucavaca Belt, which probably correspond to rift deposits related to the break up of Laurentia from Gondwana at the end of the Proterozoic and beginning of the Palaeozoic. Granites of the younger group cut the deformational structures of the Paraguay Belt metasediments and pre-date, by between 40 and 20 Ma, the initial stages of subsidence and sedimentation of the Paraná Basin. 相似文献
7.
J.B. Rodrigues M.M. Pimentel B. Buhn M. Matteini M.A. Dardenne C.J.S. Alvarenga R.A. Armstrong 《Gondwana Research》2012,21(2-3):439-450
The Vazante Group show varied U–Pb provenance patterns along the basin. Zircon ages range from 936 to 3409 Ma, but Paleo- and Mesoproterozoic terrains constitute the main sources of the original sediments. The youngest population (~ 930 Ma) establishes the maximum depositional age of the group. Sm–Nd TDM data show the predominance of Paleoproterozoic ages (1.90–2.08 Ga) and also indicate some input from younger sources in rocks of the Lapa Formation (1.67 to 2.0 Ga) in the upper part of the group, whereas rocks of the Serra do Garrote Formation present the oldest model ages (2.03 to 2.76 Ga). Hf isotopic compositions of the detrital zircons indicate that they were derived mainly from recycled Paleoproterozoic crust with a minor Mesoproteroic juvenile component. Terranes within the São Francisco Craton represent the main sources of detrital sediments of this group and reinforce the interpretation that it may be a passive margin sequence developed along the western margin of the original continent. However, the origin of Mesoproterozoic grains remains uncertain. Slightly younger Sm–Nd model ages in the Lapa Formation, however, are not entirely consistent with derivation solely from the craton and may indicate contribution from younger sources, such as the Neoproterozoic Goiás Magmatic Arc. 相似文献
8.
Drumond David Alvarenga Amarante Flávio Azevedo Neves Koppe Vanessa Cerqueira Costa João Felipe Coimbra Leite 《Natural Resources Research》2020,29(1):551-560
Natural Resources Research - Resources of mineral deposits are commonly estimated using data extracted from rock cores obtained by drilling. Information of good quality and quantity is essential to... 相似文献
9.
Roberto Ventura Santos Paulo A. Souza Carlos Jos Souza de Alvarenga Elton Luiz Dantas Marcio Martins Pimentel Claudinei Gouveia de Oliveira Laury Medeiros de Araújo 《Gondwana Research》2006,9(4):456-463
This paper presents the first SHRIMP zircon age data from bentonitic ash fall layers intercalated with the Irati sedimentary rocks, as well as palynofossils retrieved from the PETROBRAS-Six mine, Paraná State, southern Brazil. The Permian Irati Formation is one the most important oil source horizons within the Paraná Basin, and consists mainly of siltstones, gray claystones, as well as organic-rich claystones intercalated with limestones. Zircon morphology based on cathodoluminescence images includes two different populations: a dominant population of euhedral, prismatic, elongate to acicular grains which are most likely related to an ash fall volcanism; and a population of rounded to large prismatic grains, that were interpreted as detrital grains. SHRIMP analysis performed on the euhedral and prismatic grains revealed an age of ca. 278.4 ± 2.2 Ma (7 points with 95% confidence) interpreted as the crystallization age of the volcanic eruption. Based on this new dating, the Irati Formation should be placed on the Lower Permian (Cisuralian), Artinskian in age, modifying substantially the traditional ages previously attributed to this unit. The palynofossils from this level include key species of the Lueckisporites virkkiae Zone (such as L. virkkiae, L. densicorpus, L. stenotaeniatus, Weylandites lucifer, Alisporites splendens). Typical species of this zone also occur in African and other South American (Argentina) Permian strata, allowing stratigraphical correlations. The origin of the ash falls is not clearly defined. It may be related either to calc-alkaline arc magmatism associated to the Sanrafaelica Orogeny (275 and 250 Ma) or to bimodal volcanic events associated to an early intracontinental rift developed within southwestern Gondwana at ca. 278 My. The dating of this unit is significative to calibrate biostratigraphic schemes along the Paraná Basin, as well as equivalent zones in Gondwana areas, mainly in its Occidental portion. 相似文献
10.
Carlos J.S. de Alvarenga Marcel A. Dardenne Roberto V. Santos Emanuele R. Brod Simone M.C.L. Gioia Alcides N. Sial Elton L. Dantas Valderez P. Ferreira 《Gondwana Research》2008,13(4):469-479
The Neoproterozoic carbonate sequence on the southeastern border of the Amazon Craton is divided into three lithostratigraphic units: a basal cap dolomite, an intermediate limestone, limestone-mudstone unit, and an upper dolarenite-dolorudite unit. Sections of the cap-carbonate were measured from the inner shelf to the outer shelf. Carbon isotope ratios (relative to PDB) vary between − 10.5 and − 1.7‰ in cap dolomite, and between − 5.4 and + 0.1‰ in laminated limestone and mud-limestone. Limestones and mud-limestones exhibit 87Sr/86Sr ratios ranging from 0.70740 to 0.70780. A comparative isotope stratigraphy between the inner-shelf and the middle-shelf basin shows differences in carbon isotope ratios: The cap dolomite and limestones have lower δ13C ratios on the border of the basin (inner shelf) than in the middle shelf of the basin. These lower values can be related to shallower environmental conditions and to a stronger influence of the continental border. The 87Sr/86Sr ratios are the same in both areas, and are consistent with seawater composition at around 600 Ma. 相似文献