Late Quaternary vegetation and climate dynamics in central-eastern Brazil: insights from a ~35k cal a bp peat record in the Cerrado biome     

Ingrid Horák-Terra  Antonio Martínez Cortizas  Cynthia Fernandes Pinto Da Luz  Alexandre Christófaro Silva  Tim Mighall  Plínio Barbosa De Camargo  Carlos Victor Mendonça-Filho  Paulo Eduardo De Oliveira  Francisco Willian Cruz  Pablo Vidal-Torrado 《第四纪科学杂志》2020,35(5):664-676

The late Quaternary evolution of central-eastern Brazil has been under-researched. Questions remain as to the origin of the Cerrado, a highly endangered biome, and other types of vegetation, such as the Capões – small vegetation islands of semi-deciduous and mountain forests. We investigated the factors that influenced the expansion and contraction of the Cerrado and Capões during the late Quaternary (last ~35 ka), using a multi-proxy approach: stable isotopes (δ¹³C, δ¹⁵N), geochemistry, pollen and multivariate statistics derived from a peat core (Pinheiro mire, Serra do Espinhaço Meridional). Five major shifts in precipitation, temperature, vegetation and landscape stability occurred at different timescales. Our study revealed that changes in the South Atlantic Convergence Zone (SACZ) seem to have been coeval with these shifts: from the Late Glacial Maximum to mid-Holocene the SACZ remained near (~29.6 to ~16.5k cal a bp ) and over (~16.5 to ~6.1 k cal a bp ) the study area, providing humidity to the region. This challenges previous research which suggested that climate was drier for this time period. At present, the Capões are likely to be a remnant of a more humid climate; meanwhile, the Cerrado biome seems to have stablished in the late Holocene, after ~3.1 k cal a bp .  相似文献   

Robust numerical implementation of a 3D rate-dependent model for reservoir geomechanical simulations     

Giovanni Isotton  Pietro Teatini  Massimiliano Ferronato  Carlo Janna  Nicolò Spiezia  Stefano Mantica  Giorgio Volonte 《国际地质力学数值与分析法杂志》2019,43(18):2752-2771

A 3D elasto-plastic rate-dependent model for rock mechanics is formulated and implemented into a Finite Element (FE) numerical code. The model is based on the approach proposed by Vermeer and Neher (A soft soil model that accounts for creep. In: Proceedings of the International Symposium “Beyond 2000 in Computational Geotechnics,” pages 249-261, 1999). An original strain-driven algorithm with an Inexact Newton iterative scheme is used to compute the state variables for a given strain increment.The model is validated against laboratory measurements, checked on a simplified test case, and used to simulate land subsidence due to groundwater and hydrocarbon production. The numerical results prove computationally effective and robust, thus allowing for the use of the model on real complex geological settings.  相似文献   

Sedimentological analysis of two drill cores through the crater moat‐filling breccia,Flynn Creek impact structure,Tennessee     

L. De Marchi  J. Orm  D. T. King  D. R. Adrian  J. J. Hagerty  T. A. Gaither 《Meteoritics & planetary science》2019,54(11):2864-2878

Sedimentological (line‐logging) analysis of two drill cores, FC77‐3 and FC67‐3, situated, respectively, in the northwestern and southeastern quadrants of the Flynn Creek impact structure's crater‐moat area reveals that the ~27 m thick crater moat‐filling breccia consists of three subequal parts. These parts, which were deposited during early modification stage of this marine‐target impact structure, are distinguished on the basis of vertical trends in sorting, grain size, and counts of clasts per meter in comparison with other well‐known marine‐target impact structures, namely Lockne, Tvären, and Chesapeake Bay. The lower part is interpreted to represent mainly slump deposits, and the middle part is interpreted to represent a stage intermediate between slump and marine resurge, that is, a traction flow driven by overriding suspension flow. The upper part (size graded, and relatively well sorted and fine grained) is interpreted to represent marine resurge flow only. The upper part is capped by a relatively thin and relatively fine‐grained calcarenite to calcisiltite deposit.  相似文献   

The role of a national park in classifying mountain tourism destinations: An exploratory study of the Italian Western Alps     

DUGLIO Stefano  LETEY Marilisa 《山地科学学报》2019,(7)

Together with the main aim of preserving nature, national parks are also expected to play an important role for the local communities, driving economic activities toward the lens of sustainable development. This contribution aims to present an exploratory study on the relationship between the presence of a protected mountain area, the Gran Paradiso National Park(GPNP), in the North West of the Italian Alps, and the classification of tourism destinations, according to Weaver model of destination management. Starting from the model,the authors provide a quantitative analysis using a set of variables and indicators to comprehensively assess the differing patterns assumed by the municipalities within the borders of the GPNP and those that are not.The provisional results illustrate that the municipalities within the border of a protected area are more likely to be grouped alongside the sustainable mountain destinations. Meanwhile,research outcomes confirm that a protected area does not necessarily contrast the tourism industry but instead may boost local development by driving it within the borders of the sustainable development,switching from the area's only preservation function to a flywheel for the local communities.  相似文献   

Carbonaceous chondrites as analogs for the composition and alteration of Ceres          下载免费PDF全文

Harry Y. McSween Jr.  Joshua P. Emery  Andrew S. Rivkin  Michael J. Toplis  Julie C. Castillo‐Rogez  Thomas H. Prettyman  M. Cristina De Sanctis  Carle M. Pieters  Carol A. Raymond  Christopher T. Russell 《Meteoritics & planetary science》2018,53(9):1793-1804

The mineralogy and geochemistry of Ceres, as constrained by Dawn's instruments, are broadly consistent with a carbonaceous chondrite (CM/CI) bulk composition. Differences explainable by Ceres’s more advanced alteration include the formation of Mg‐rich serpentine and ammoniated clay; a greater proportion of carbonate and lesser organic matter; amounts of magnetite, sulfide, and carbon that could act as spectral darkening agents; and partial fractionation of water ice and silicates in the interior and regolith. Ceres is not spectrally unique, but is similar to a few other C‐class asteroids, which may also have suffered extensive alteration. All these bodies are among the largest carbonaceous chondrite asteroids, and they orbit in the same part of the Main Belt. Thus, the degree of alteration is apparently related to the size of the body. Although the ammonia now incorporated into clay likely condensed in the outer nebula, we cannot presently determine whether Ceres itself formed in the outer solar system and migrated inward or was assembled within the Main Belt, along with other carbonaceous chondrite bodies.  相似文献   

Mineralogy and temperature of crater Haulani on Ceres          下载免费PDF全文

F. Tosi  F. G. Carrozzo  A. Raponi  M. C. De Sanctis  G. Thangjam  F. Zambon  M. Ciarniello  A. Nathues  M. T. Capria  E. Rognini  E. Ammannito  M. Hoffmann  K. Krohn  A. Longobardo  E. Palomba  C. M. Pieters  K. Stephan  C. A. Raymond  C. T. Russell 《Meteoritics & planetary science》2018,53(9):1902-1924

We investigate the region of crater Haulani on Ceres with an emphasis on mineralogy as inferred from data obtained by Dawn's Visible InfraRed mapping spectrometer (VIR), combined with multispectral image products from the Dawn Framing Camera (FC) so as to enable a clear correlation with specific geologic features. Haulani, which is one of the youngest craters on Ceres, exhibits a peculiar “blue” visible to near‐infrared spectral slope, and has distinct color properties as seen in multispectral composite images. In this paper, we investigate a number of spectral indices: reflectance; spectral slopes; abundance of Mg‐bearing and NH₄‐bearing phyllosilicates; nature and abundance of carbonates, which are diagnostic of the overall crater mineralogy; plus a temperature map that highlights the major thermal anomaly found on Ceres. In addition, for the first time we quantify the abundances of several spectral endmembers by using VIR data obtained at the highest pixel resolution (~0.1 km). The overall picture we get from all these evidences, in particular the abundance of Na‐ and hydrous Na‐carbonates at specific locations, confirms the young age of Haulani from a mineralogical viewpoint, and suggests that the dehydration of Na‐carbonates in the anhydrous form Na₂CO₃ may be still ongoing.  相似文献   

An on Orbit Determination of Point Spread Functions for the <Emphasis Type="Italic">Interface Region Imaging Spectrograph</Emphasis>     

Hans Courrier  Charles Kankelborg  Bart De Pontieu  Jean-Pierre Wülser 《Solar physics》2018,293(9):125

Using the 2016 Mercury transit of the Sun, we characterize on orbit spatial point spread functions (PSFs) for the Near- (NUV) and Far- (FUV) Ultra-Violet spectrograph channels of NASA’s Interface Region Imaging Spectrograph (IRIS). A semi-blind Richardson–Lucy deconvolution method is used to estimate PSFs for each channel. Corresponding estimates of Modulation Transfer Functions (MTFs) indicate resolution of 2.47 cycles/arcsec in the NUV channel near 2796 Å and 2.55 cycles/arcsec near 2814 Å. In the short (\({\approx}\,1336~\mathring{\mathrm{A}}\)) and long (\({\approx}\,1394~\mathring{\mathrm{A}}\)) wavelength FUV channels, our MTFs show pixel-limited resolution (3.0 cycles/arcsec). The PSF estimates perform well under deconvolution, removing or significantly reducing instrument artifacts in the Mercury transit spectra. The usefulness of the PSFs is demonstrated in a case study of an isolated explosive event. PSF estimates and deconvolution routines are provided through a SolarSoft module.  相似文献   

Proactive Management of Ecosystem Services in Oil Sands Pre-mining Phase     

Omotehinse  A. O.  De Tomi  G.  Baninla  Yvette 《Natural Resources Research》2020,29(2):949-965

Natural Resources Research - Ecosystems and their services are essential to human well-being, but mining activities often cause adverse impacts on these services. Although impact of mining...  相似文献   

城市中心体系研究的理论基础与分析框架     

晏龙旭  王德  张尚武 《地理科学进展》2020,39(9):1576-1586

“经济—空间”视角下城市中心体系的理论与实证研究之间缺少相互衔接的分析框架。论文通过对经典理论的系统归纳与演绎,建立整体视角下理解城市中心体系形成与发展的理论框架,将城市中心体系的发展规律概括为空间竞争和空间联系2个机制,体现在本地服务功能和非本地功能的空间组织过程,分别形成等级网状结构和专业化点状结构,并相互融合形成“半网格”的城市中心体系,扮演着本地与宏观区域结构之间的“转换发动机”。最后探讨了对实证研究的若干启示,提出城市中心的定义和识别方法应注意与理论研究相互衔接;认为城市中心的本地/非本地功能特征及相应的发展机制亟待实证;认为中心及其空间影响的调控潜力是制定规划政策的前提。  相似文献   

Use of Olive Mill Wastewater as a Growth Medium for Superoxide Dismutase and Catalase Production          下载免费PDF全文

Didem Değirmenbaşı  Serpil Takaç 《洁净——土壤、空气、水》2018,46(5)

  相似文献