Environmental changes and carbon cycle perturbations at the Triassic–Jurassic boundary in northern Switzerland     

Nathan Looser  Elke Schneebeli-Hermann  Heinz Furrer  Thomas M. Blattmann  Stefano M. Bernasconi 《Swiss Journal of Geoscience》2018,111(3):445-460

The Triassic–Jurassic boundary is characterized by strong perturbations of the global carbon cycle, triggered by massive volcanic eruptions related to the onset of the Central Atlantic Magmatic Province. These perturbations are recorded by negative carbon isotope excursions (CIEs) which have been reported worldwide. In this study, Triassic–Jurassic boundary sections from the southern margin of the Central European Basin (CEB) located in northern Switzerland are analyzed for organic carbon and nitrogen isotopes in combination with particulate organic matter (POM) analyses. We reconstruct the evolution of the depositional environment from Late Triassic to Early Jurassic in northern Switzerland and show that observed negative shifts in δ¹³C of the total organic carbon (δ¹³C_TOC) in the sediment are only subordinately influenced by varying organic matter (OM) composition and primarily reflect global changes in the carbon cycle. Based on palynology and the stratigraphic positions of isotopic shifts, the δ¹³C_TOC record of the studied sections is correlated with the GSSP section at Kuhjoch (Tethyan realm) in Austria and with the St. Audrie’s Bay section (CEB realm) in southwest England. We also show that in contrast to POM analyses the applicability of organic carbon/total nitrogen (OC/TN) atomic ratios and stable isotopes of total nitrogen (δ¹⁵N_TN) for detecting changes in source of OM is limited in marginal depositional environments with frequent changes in lithology and OM contents.  相似文献   

高校新型测量实验场地的建立研究     

王迪  邹浜  周海波  王伟权 《测绘与空间地理信息》2018,(1):202-204,210

提出了一种针对高校的新型测量实验场地建立方法,该新型测量实验场地可以有效地进行高速铁路CPⅢ控制网和建筑变形监测网的仿真实验,克服了传统测量实验场地不能进行此类实验的局限。实践证明,学生或科研团队在该实验场地通过仿真实验能够熟悉并掌握相应实际工程的作业流程并获得可靠的基础实验数据。  相似文献   

Phenological metrics-based crop classification using HJ-1 CCD images and Landsat 8 imagery   总被引：1，自引：0，他引：1  

Xiaochun Zhang  Qinxue Xiong  Liping Di  Junmei Tang  Jin Yang  Huayi Wu 《International Journal of Digital Earth》2018,11(12):1219-1240

Crop type data are an important piece of information for many applications in agriculture. Extracting crop type using remote sensing is not easy because multiple crops are usually planted into small parcels with limited availability of satellite images due to weather conditions. In this research, we aim at producing crop maps for areas with abundant rainfall and small-sized parcels by making full use of Landsat 8 and HJ-1 charge-coupled device (CCD) data. We masked out non-vegetation areas by using Landsat 8 images and then extracted a crop map from a long-term time-series of HJ-1 CCD satellite images acquired at 30-m spatial resolution and two-day temporal resolution. To increase accuracy, four key phenological metrics of crops were extracted from time-series Normalized Difference Vegetation Index curves plotted from the HJ-1 CCD images. These phenological metrics were used to further identify each of the crop types with less, but easier to access, ancillary field survey data. We used crop area data from the Jingzhou statistical yearbook and 5.8-m spatial resolution ZY-3 satellite images to perform an accuracy assessment. The results show that our classification accuracy was 92% when compared with the highly accurate but limited ZY-3 images and matched up to 80% to the statistical crop areas.  相似文献   

Along‐strike evolution of folding,stretching and breaching of supra‐salt strata in the Plataforma Burgalesa extensional forced fold system (northern Spain)          下载免费PDF全文

Stefano Tavani  Pablo Granado 《Basin Research》2015,27(4):573-585

The Plataforma Burgalesa is a partly exposed extensional forced fold system with an intermediate salt layer, which has developed along the southern portion of the Basque‐Cantabrian Basin from Malm to Early Cretaceous as part of the Bay of Biscay‐Pyrenean rift system. Relationships between syn‐ and pre‐rift strata of the supra‐salt cover sequence and distribution of intra‐cover second‐order faults are observed both along seismic sections and at the surface. These relationships indicate an along‐strike variability of the extensional structural style. After a short period of salt mobilization and forced folding, high slip rates in the central portion of the major basement faults have rapidly promoted brittle behaviour of the salt layer, preventing further salt mobilization and facilitating the propagation of the fault across the salt layer. In contrast, at the tip regions of basement faults, slower slip rates have facilitated ductile salt behaviour, ensuring its further evaporite evacuation, preventing fault propagation across the salt layer and, in essence, allowing for a long‐living forced folding process. Our results indicate the important effect of along‐strike variation in displacement and displacement rates in controlling evaporite behaviour in extensional basins. Amount of displacement and displacement rates are key factors controlling the propagation of basement faults across evaporite layers. In addition, growth strata patterns are recognized as a powerful tool for constraining the up‐dip propagation history of basement faults in extensional fault‐related fold systems with intermediate décollement levels.  相似文献   

Heat capacity of hydrous trachybasalt from Mt Etna: comparison with CaAl<Subscript>2</Subscript>Si<Subscript>2</Subscript>O<Subscript>8</Subscript> (An)–CaMgSi<Subscript>2</Subscript>O<Subscript>6</Subscript> (Di) as basaltic proxy compositions     

D.?GiordanoEmail author  A.?R.?L.?Nichols  M.?Potuzak  D.?Di?Genova  C.?Romano  J.?K.?Russell 《Contributions to Mineralogy and Petrology》2015,170(5-6):48

The specific heat capacity (C _p) of six variably hydrated (~3.5 wt% H₂O) iron-bearing Etna trachybasaltic glasses and liquids has been measured using differential scanning calorimetry from room temperature across the glass transition region. These data are compared to heat capacity measurements on thirteen melt compositions in the iron-free anorthite (An)–diopside (Di) system over a similar range of H₂O contents. These data extend considerably the published C _p measurements for hydrous melts and glasses. The results for the Etna trachybasalts show nonlinear variations in, both, the heat capacity of the glass at the onset of the glass transition (i.e., C _p ^g ) and the fully relaxed liquid (i.e., C _p ^l ) with increasing H₂O content. Similarly, the “configurational heat capacity” (i.e., C _p ^c  = C _p ^l  ? C _p ^g ) varies nonlinearly with H₂O content. The An–Di hydrous compositions investigated show similar trends, with C _p values varying as a function of melt composition and H₂O content. The results show that values in hydrous C _p ^g , C _p ^l and C _p ^c in the depolymerized glasses and liquids are substantially different from those observed for more polymerized hydrous albitic, leucogranitic, trachytic and phonolitic multicomponent compositions previously investigated. Polymerized melts have lower C _p ^l and C _p ^c and higher C _p ^g with respect to more depolymerized compositions. The covariation between C _p values and the degree of polymerization in glasses and melts is well described in terms of SM_hydrous and NBO/T _hydrous. Values of C _p ^c increase sharply with increasing depolymerization up to SM_hydrous ~ 30–35 mol% (NBO/T _hydrous ~ 0.5) and then stabilize to an almost constant value. The partial molar heat capacity of H₂O for both glasses (\( C_{{{\text{p}}\;{\text{H}}_{2} {\text{O}}}}^{\text{g}} \)) and liquids (\( C_{{{\text{p}}\;{\text{H}}_{2} {\text{O}}}}^{\text{l}} \)) appears to be independent of composition and, assuming ideal mixing, we obtain a value for \( C_{{{\text{p}}\;{\text{H}}_{2} {\text{O}}}}^{\text{l}} \) of 79 J mol^?1 K^?1. However, we note that a range of values for \( C_{{{\text{p}}\;{\text{H}}_{2} {\text{O}}}}^{\text{l}} \) (i.e., ~78–87 J mol^?1 K^?1) proposed by previous workers will reproduce the extended data to within experimental uncertainty. Our analysis suggests that more data are required in order to ascribe a compositional dependence (i.e., nonideal mixing) to \( C_{{{\text{p}}\;{\text{H}}_{2} {\text{O}}}}^{\text{l}} \).  相似文献   

Landslide susceptibility modeling assisted by Persistent Scatterers Interferometry (PSI): an example from the northwestern coast of Malta     

Piacentini  Daniela  Devoto  Stefano  Mantovani  Matteo  Pasuto  Alessandro  Prampolini  Mariacristina  Soldati  Mauro 《Natural Hazards》2015,78(1):681-697

Natural Hazards - Persistent Scatterers Interferometry (PSI) techniques are widely employed in geosciences to detect and monitor landslides with high accuracy over large areas, but they also suffer...  相似文献   

Adaptation of the Canadian Fire Weather Index to Mediterranean forests     

Chelli  Stefano  Maponi  Pierluigi  Campetella  Giandiego  Monteverde  Paolo  Foglia  Monica  Paris  Eleonora  Lolis  Andreas  Panagopoulos  Thomas 《Natural Hazards》2015,75(2):1795-1810

Natural Hazards - The Canadian Fire Weather Index (FWI) is one of the most used tools to forecast forest fire hazard. In this paper, we propose an adaptation of the FWI to take into account the...  相似文献   

Modelling feedback from stars and black holes in galaxy mergers   总被引：2，自引：0，他引：2  

Volker Springel  Tiziana Di Matteo  Lars Hernquist 《Monthly notices of the Royal Astronomical Society》2005,361(3):776-794

  相似文献   

高美古空气湿度的初步分析     

马开全 《天文研究与技术》1999,(2):12

给出丽江高美古天文候选点两年的湿度观测结果与宾川３００２ｍ山峰的比较,初步分析了湿度对天文可用时间及视宁度的影响。  相似文献   

基于条件价值法的风云卫星数据和服务社会效益评估研究     

李雪  咸迪 《气象研究与应用》2022,43(1):53-58

基于条件价值法,分析风云卫星数据和服务的分类支付意愿,利用二元Logistic模型,对影响用户支付意愿的因素进行研究.结果表明:(1)40％的受访公众对风云卫星数据和服务有支付意愿,人均年支付意愿额为31元;(2)风云卫星的数据和服务对十省市民众的年总价值为189亿元;(3)本人或家属是否在气象部门工作以及对风云卫星数...  相似文献