Upper Cretaceous trench deposits of the Neo-Tethyan subduction zone: Jiachala Formation from Yarlung Zangbo suture zone in Tibet,China     

Hanpu Fu  Xiumian Hu  Erica M. Crouch  Wei An  Jiangang Wang  Eduardo Garzanti 《中国科学:地球科学(英文版)》2018,61(9):1204-1220

The history of convergence between the India and the Asia plates, and of their subsequent collision which triggered the Himalayan orogeny is recorded in the Yarlung Zangbo suture zone. Exposed along the southern side of the suture, turbidites of the the Jiachala Formation fed largely from the Gangdese arc have long been considered as post-collisional foreland-basin deposits based on the reported occurrence of Paleocene-early Eocene dinoflagellate cysts and pollen assemblages. Because magmatic activity in the Gangdese arc continued through the Late Cretaceous and Paleogene, this scenario is incompatible with U-Pb ages of detrital zircons invariably older than the latest Cretaceous. To solve this conundrum, we carried out detailed stratigraphic, sedimentological, paleontological, and provenance analyses in the Gyangze and Sajia areas of southern Tibet,China. The Jiachala Formation consists of submarine fan deposits that lie in fault contact with the Zongzhuo Formation.Sandstone petrography together with U-Pb ages and Hf isotope ratios of detrital zircons indicate provenance from the Gangdese arc and central Lhasa terrane. Well preserved pollen or dinoflagellate cysts microfossils were not found in spite of careful research, and the youngest age obtained from zircon grain was ～84 Ma. Based on sedimentary facies, provenance analysis and tectonic position, we suggest that the Jiachala Formation was deposited during the Late Cretaceous(~88–84 Ma) in the trench formed along the southern edge of Asia during subduction of Neo-Tethyan oceanic lithosphere.  相似文献   

Planimetric and volumetric changes of reef islands in response to wave conditions          下载免费PDF全文

Mirella B. Costa  Eduardo C. Macedo  Eduardo Siegle 《地球表面变化过程与地形》2017,42(15):2663-2678

Reef islands are morphologically dynamic features located on atolls and platform reefs that are very sensitive to wave‐induced processes on different timescales. The planform morphological evolution of reef islands is widely described; however, the mechanisms of the volumetric variations in response to wave energy are still poorly documented. To assess their multitemporal vertical and horizontal mobility, we performed a series of synchronous measurements of the volumetric changes and incident wave energies at two reef islands and a shingle bank at the Rocas Atoll in the South Atlantic Ocean. The results show the differences in the magnitudes and locations of the sediment mobility between the reef islands. Whereas one island remained stable on all timescales, with only small volumetric changes concentrated at its extremities, the other island (Farol Island) showed high mobility, especially during the energetic northern swell season. The gross volumetric change reached 10.03 × 10³ m³ (5% of the total island volume) on a daily timescale; however, on a seasonal scale, the gross erosion was compensated by the gross accretion, indicating a cyclical seasonal pattern. Moreover, the observed volumetric changes induced by the waves on both daily and seasonal timescales did not result in large shoreline displacements. However, long‐term oceanward erosion and substantial lagoonward accretion were observed at Farol Island on a decadal scale, resulting in a pronounced change in its planform morphology. This appears to be promoted by at least three sediment transport pathways induced by waves at the atoll, including sediment adjustment between the reef islands. Our results show that reef islands on the same atoll can have very distinct morphological behaviors on daily, seasonal and decadal scales in response to the same boundary conditions. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Magnetic record of El Niño Southern Oscillation in Late Pleistocene sediments from Mucubají lake (western Venezuela)     

Juan Andrés Arévalo Groening  Vincenzo Costanzo-Alvarez  Milagrosa Aldana  Eduardo Carrillo  Franck Audemard 《Studia Geophysica et Geodaetica》2017,61(2):336-360

El Niño Southern Oscillation (ENSO) is an internal forcing of the climate system. This event has an actual frequency of 2 to 8 years. Evidence from a paleoclimate proxy database of gray scale (GS), in samples from Pallcacocha lake in Ecuador, indicates that the ENSO had a frequency of 35 to 75 years during the Late Pleistocene. In this work we explored the possible relationship between the ENSO proxies (GS) from Pallcacocha and magnetic parameters from sediments sampled at the Mucubají lake in Mérida, Venezuela (i.e. mass-specific magnetic susceptibility, magnetic remanence S ratio and susceptibilitynormalized saturation isothermal remanent magnetization). After applying a Lanczos bandpass filter to the rock magnetic and the GS data, in order to remove, as much as possible, frequencies associated to any periodic event other than ENSO, we found significant correlations between GS and magnetic parameters for the period between 12450 and 10560 cal. yrs BP. These relationships were obtained using an Adaptive Neuro Fuzzy Inference System (ANFIS), a hybrid algorithm that combines fuzzy logic with neural networks. The results show that the magnetic parameters obtained in Mucubají are able to explain 50.5% of the total variance of the ENSO proxy in a range of 35 to 75 years in Pallcacocha, which is roughly the same percentage of the total variance of the temperature in the Venezuelan Andes, explained by the ENSO at present times. In this way we have inferred a possible influence of the ENSO in the Venezuelan Andes during the Late Pleistocene.  相似文献   

Local groundwater balance model: stakeholders’ efforts to address groundwater monitoring and literacy     

Yolanda Lopez-Maldonado  Eduardo Batllori-Sampedro  Claudia R. Binder  Brian D. Fath 《水文科学杂志》2017,62(14):2297-2312

Understanding groundwater systems is crucial to ensure their monitoring and protection. Global groundwater models and predictive tools exist to better understand them. In view of scarce groundwater data, especially in developing countries, the question of how to model these systems and make them usable for groundwater management is crucial. Herein, we demonstrate how a transdisciplinary process can overcome the data scarcity problem and lead to the development of a local groundwater balance model (LGBM). Over 50 actors from more than 15 disciplines and groundwater-related sectors were involved for the case of Yucatan, Mexico. Results revealed high wastewater emissions to the aquifer discharged without treatment and poor recycling practices. The method can be adapted to specific regions, can be used to address methodological challenges for monitoring, and can contribute to the achievement of the 2030 Development Agenda by addressing Sustainable Development Goal 6-related Targets (6.3, 6.4, 6.5, 6.6(a, b)).  相似文献   

Filtered incremental velocity: A novel approach in intensity measures for seismic collapse estimation     

Héctor Dávalos  Eduardo Miranda 《地震工程与结构动力学》2019,48(12):1384-1405

This study evaluates the performance of a new intensity measure, referred to as filtered incremental velocity FIV3, which is computed using time-domain features extracted from an acceleration time series and is aimed at the evaluation of structural collapse. This novel approach focuses on the area under a small number of acceleration pulses in the ground motion instead of focusing on the peak response of linear elastic oscillators as in many recently proposed measures of ground motion intensity. FIV3 is developed based on previous research that has highlighted the close relation between the incremental velocity of a ground motion and its potential to induce large inelastic incursions on structures. However, unlike the original definition of incremental velocity which provides a single level of intensity for a ground motion, this new intensity measure is period-dependent and computed as the sum of the three largest incremental velocities obtained from a low-pass filtered ground acceleration time series. Efficiency and sufficiency with respect to several ground motion parameters such as magnitude, source-to-site-distance, spectral shape, scale factor, and duration are carefully evaluated and compared against those computed with some traditional and recently proposed intensity measures using collapse results from a four-story reinforced concrete frame. Results indicate that FIV3 leads to lower variability of collapse estimates and therefore higher efficiency as well as high sufficiency compared with those of other ground motion intensity parameters indicating that this new intensity measure is a promising parameter for structural collapse risk assessment.  相似文献   

Object-based image analysis supported by data mining to discriminate large areas of soybean     

Carlos Antonio da Silva Junior  Marcos Rafael Nanni  José Francisco de Oliveira-Júnior  Everson Cezar  Paulo Eduardo Teodoro  Rafael Coll Delgado 《International Journal of Digital Earth》2019,12(3):270-292

This research aimed to analyze the possibility to estimate and automatically map large areas of soybean cultivation through the use of MODIS (Moderate-Resolution Imaging Spectroradiometer) images. Two major techniques were used: GEOgraphic-Object-Based Image Analysis (GEOBIA) and Data Mining (DM). In order to obtain the images, the segmentation algorithm implemented by Definiens Developer was used. A decision tree (DT) was created from a training set previously prepared. Time-series of images from the MODIS sensor aboard the Terra satellite were acquired in order to represent the wide variation of the vegetation pattern along the soybean crop cycle. The time-series data were used only for the CEI index. Furthermore, to compare the results obtained from GEOBIA, the slicing technique was used at the CEI level. After the training, the DT was applied to the vegetation indices generating the thematic map of the spatial distribution of soybean. In accordance with the error matrix and kappa parameter analysis, tests for statistical significance were created. Results indicate that the classification achieved by Kappa coefficients is 0.76. In short, the obtained results proved that combining vegetation indices and time-series data using GEOBIA return promising results for mapping soybean plantation on a regional scale.  相似文献   

Ichthyoplankton spatial pattern in the inner shelf off Bahía Blanca Estuary, SW Atlantic Ocean     

Mnica Susana Hoffmeyer  Menndez María Clara  Biancalana Florencia  Nizovoy Alicia Mabel  Torres Eduardo Ramn 《Estuarine, Coastal and Shelf Science》2009,84(3):181-392

This study focuses on the composition, abundance and distribution of ichthyoplankton in the inner shelf area off Bahía Blanca Estuary on the SW Atlantic Ocean during late spring. Eggs and larvae of Brevoortia aurea, Engraulis anchoita, Parona signata, Sciaenidae spp. – such as Cynoscion guatucupa and Micropogonias furnieri –, and Odontesthes argentinensis were found. Species richness was low probably as a result of season and shallow depths. Ichthyoplankton abundance reached values close to 10 000 per 10 m⁻³ (eggs) and 4000 per 10 m⁻³ (larvae) and displayed a spatial distribution pattern with maximum abundance values restricted to a band parallel to the coast. Differences between egg and larval patterns, probably derived from a different displacement and hydrodynamic behavior, were observed. Egg and larvae distribution patterns were found related with spawning areas and to directly depend on salinity and mesozooplankton. The larvae distribution pattern, in particular, was found to inversely depend on particulate organic carbon. In addition, the geographic location of egg and larvae maxima strongly coincided with a saline front reported for this area in springtime, thus suggesting a direct relationship with it.  相似文献   

Development of a foraminifera-based transfer function in the Basque marshes, N. Spain: Implications for sea-level studies in the Bay of Biscay     

Eduardo Leorri  Benjamin P. Horton  Alejandro Cearreta 《Marine Geology》2008,251(1-2):60-74

In order to reconstruct former sea level we have developed a foraminifera-based transfer function using three models based on a modern dataset of 59 samples and 23 species obtained from four Basque marshes in Northern Spain. The relationship between observed and foraminifera-predicted elevation illustrated the strong performance of the transfer function (r²_jack ranges from 0.74 to 0.81). These results indicated that precise reconstructions of former sea levels are possible (error ranges from 0.11 to 0.19 m). The transfer function was used to calibrate the foraminiferal assemblages collected from a 50 cm salt marsh core. We placed the foraminifera-based reconstructions into a temporal framework using ¹³⁷Cs, Pb concentrations, and ²¹⁰Pb-derived sediment accumulation rates. The resulting relative sea-level curve is in good agreement with regional tide-gauge data. Both instrumental data and microfossil records suggest a rate of relative sea-level rise of approximately 2 mm yr^− 1 for the 20th century.  相似文献   

Full-scale experimental investigations on the response of a flooded passenger vehicle under subcritical conditions     

Al-Qadami  Ebrahim Hamid Hussein  Mustaffa  Zahiraniza  Shah  Syed Muzzamil Hussain  Matínez-Gomariz  Eduardo  Yusof  Khamaruzaman Wan 《Natural Hazards》2022,110(1):325-348

Natural Hazards - Vehicles can be easily swept away by floodwaters once the flow velocity and depth reach certain critical limits, with probabilities toward fatality reported to be nearly 50%....  相似文献