Spectral identification of materials by reflectance spectral library search

Spectral library search is emerging as a viable approach for material identification and mapping by reusing spectral knowledge gained from hyperspectral remote sensing across space and time. The potential of retrieving meaningful spectral material identifications in the presence of reflectance of spectra of various material types and with various similarity metrics has been assessed in this study. Test reflectance spectra of various vegetation, minerals, soils and urban material types are identified by searching through the composite reflectance spectral library obtained by combining various institutional reflectance spectral libraries. The accuracy of material identifications under various conditions: (i) in the presence of identical, similar and dissimilar spectra; (ii) in the presence of only identical and dissimilar spectra; and (iii) in the presence of only dissimilar spectra has been assessed with several similarity metrics. Results indicate the possibility of obtaining 100% accurate material identifications by library search if the spectral library contains identical spectra. However, the presence of a large number of similar spectra, despite the presence of identical spectra, is found to increase false positives, thereby reducing the accuracy of retrievals to 82% at best. Further, the accuracy of material identifications in the presence of similar spectra is similarity metric-dependent and varied from about 52% (obtained from Binary Encoding) to 82% (obtained from Normalized Spectral Similarity Score). Overall, results support the possibility of using independent reflectance spectral libraries for material identification while calling for robust spectral similarity metrics.     

内蒙古锡林郭勒地区上古生界极低级变质作用:伊利石和镜质体反射率的证据

本文使用D/max-2500X射线衍射仪研究了内蒙古锡林郭勒地区上古生界泥质岩石伊利石的成因标志,讨论了有机质镜质体反射率对变质温度的表征。研究区上古生界泥质岩石伊利石的标型特征为:伊利石结晶度分布于0.28～>0.77之间,平均值0.40;伊利石(白云母)多型以2M1型为主,2M1+1Md多型和1Md多型相对较少;伊利石(白云母)b0值变化于8.983～9.046之间,平均值9.019,指示其形成于成岩-极低级变质作用。有机质镜质体反射率具有示踪变质温度的作用,应用Barker and Pawlewiez(1986,1994)、Barker and Goldsteinl(1990)和Mullis et al.(2001)建立的镜质体反射率地质温度计,对研究区上古生界泥质岩石变质温度进行了估算,揭示古地温处于136～321℃之间,温度估算值主要分布在180～260℃之间,平均值为245℃,这表明研究区上古生界遭受了成岩-极低级变质作用,变质程度属近变质带。研究区上古生界泥质岩石的Ro值主要分布在1.01%～3.67%之间,表明有机质演化处于成熟-过成熟阶段,泥质岩石具有生烃的能力,部分层位可能具有形成油气资源的潜力。     

利用新近系煤的镜质组反射率计算滇西高原 的隆升幅度

为了定量地计算滇西高原的隆升幅度,在滇西中甸、保山、景东、景谷四地分别取新近纪煤岩样,在野外实测煤层上覆地层残留厚度和测得样品的镜质组反射率并确定有效作用时间后,根据三者关系曲线图计算出成煤时的最大古地温和最大埋深,进而计算出滇西高原上新世时期自北而南的隆升幅度在1500~1700m之间。该时期隆升表现出总体均匀抬升的特征。     

Airborne imagery of a disintegrating Sargassum drift line

Airborne hyperspectral and thermal infrared imagery collected over the Florida Current provide a view of the disintegration of a Sargassum drift line in 5 m s⁻¹ winds. The drift line consists mostly of rafts 20-80 m² in size, though aggregations larger than 1000 m² also occur. Rafts tend to be elongated, curved in the upwind direction, and 0.1-0.5 °C warmer than the surrounding ocean surface. Long weed ‘trails’ extending upwind from the rafts are evidence of plants dropping out and being left behind more rapidly drifting rafts. The raft line may be a remnant of an earlier Sargassum frontal band, which is detectible as an upwind thermal front and areas of submerged weed. Issues are identified that require future field measurements.     

Thermal history of the Rio Muni (West Africa)–NE Brazil margins during continental breakup

We document the thermal record of breakup of the conjugate Rio Muni (West Africa) and NE Brazil margins using apatite fission track analysis, vitrinite reflectance data and stratigraphic observations from both margins. These results permit determination of the timing of four cooling episodes, and the temperature of samples at the onset of each episode. All samples are interpreted to have experienced higher temperatures in the geological past due to i) elevated basal heatflow (palaeogeothermal gradient in Rio Muni-1 well decaying from 58 °C/km during the Mid Cretaceous to 21.5 °C/km in the Late Cenozoic) and ii) progressive exhumation from formerly greater burial depth. A well constrained history of changing palaeogeothermal gradient allows for much more precise quantification of the thickness of eroded section (exhumation) than if a constant heatflow is assumed. Cooling episodes identified from the palaeotemperature data at 110–95 Ma (both margins) and 85–70 Ma (Rio Muni only) coincide with major unconformities signifying, respectively, the cessation of rifting (breakup) and compressional shortening that affected the African continent following the establishment of post-rift sedimentation (drift). The interval between these separate unconformities is occupied by allochthonous rafts of shallow-water carbonates recording gravitational collapse of a marginal platform. The rift shoulder uplift that triggered this collapse was enhanced by local transpression associated with the obliquely divergent Ascension Fracture Zone, and thermal doming due to the coeval St Helena and Ascension Plumes. The data also reveal a c.45–35 Ma cooling episode, attributed to deep sea erosion at the onset of Eo-Oligocene ice growth, and a c.15–10 Ma episode interpreted as the record of Miocene exhumation of the West African continental margin related to continent-wide plume development. Integration of thermal history methods with traditional seismic- and stratigraphy-based observations yields a dynamic picture of kilometre-scale fluctuations in base level through the breakup and early drift phases of development of these margins. Major unconformities at ocean margins are likely to represent composite surfaces recording not only eustasy, but also regional plate margin-generated deformation, local ‘intra-basinal’ reorganization, and the amplifying effect of negative feedbacks between these processes.     

Estimating leaf area index by inversion of reflectance model for semiarid natural grasslands

The study developed an integrated reflectance model combining radiative transfer and geometric optical properties in order to inverse leaf area index (LAI) of semiarid natural grasslands. In order to better link remote sensing information with land plants, and facilitate regional and global climate change studies, the model introduced a simple but important geometrical similarity parameter related to plant crown shapes. The model revealed the influences of different plant crown shapes (such as spherical, cylindrical/cuboidal and conic crowns) on leaf/branch angle distribution frequencies, shadow ground coverage, shadowed or sunlit background fractions, canopy reflectance, and scene reflectance. The modeled reflectance data agreed with the measured ones in the three Leymus chinensis steppes with different degradation degrees, which validated the reflectance model. The lower the degradation degree was, the better the modeled data agreed with the measured data. After this reflectance model was coupled with the optimization inversion method, LAI over the entire study region was estimated once every eight days using the eight-day products of surface reflectance obtained by multi-spectral Moderate-Resolution Imaging Spectroradiometer (MODIS) during the growing seasons in 2002. The temporal and spatial patterns of inversed LAI for the steppes with different cover degrees, swamps, flood plains, and croplands agreed with the general laws and measurements very well. But for unused land cover types (sands, saline, and barren lands) and forestlands, totally accounting for about 10% of the study region, the reasonable LAI values were not derived by inversing, requiring further revising of the model or the development of a new model for them. Supported by the National Natural Science Foundation of China (Grant No. 30500076), the National Basic Research Program of China (Grant No. 2007CB714407), and the President Foundation of Graduate University of Chinese Academy of Sciences (Grant No. YZJJ200205)     

Relationship between statistical thermal alteration index and vitrinite reflectance for sedimentary rocks in northern Japan with reference to effects for unconformity,faulting, and contact metamorphism

Two organic maturity indices, the statistical thermal alteration index (stTAI) and vitrinite reflectance (R_O), are used to gain insight into the geological histories of sequences of Tertiary and Upper Cretaceous sediments in northern Japan that contain an unconformity and which are affected by faulting and contact metamorphism. The stTAI is based on the brightness, or gray level, of fossil pollen of Pinus, Podocarpus, Abies, and Picea species. Pollen brightness is measured using a transmitted‐light microscope equipped with a computer‐driven digital image processor. The stTAI represents the mean value of the modes for the complete array of indigenous pollen in rock samples. The stTAI indicates the level of organic maturation for Neogene sedimentary rocks of Japan, from incipient diagenesis to early catagenesis (R_O ≤1.0%). With the progressive diagenesis and catagenesis of sedimentary rocks, stTAI values generally show a progressive decrease, whereas R_O values increase. The effects of an unconformity and faulting are more clearly recorded in stTAI trends than in R_O trends. During early stages of organic maturation (R_O ≤0.7%), stTAI shows a rapid decrease, while R_O shows a rapid increase during the mature and post‐mature stages (R_O ≥0.8%). The occurrence of a range in R_O values for a given level of organic maturity makes it difficult to determine the influence of the unconformity on the increasing R_O trend. R_O values show a progressive increase toward an igneous dyke, but this trend is not apparent in stTAI values. Measurements of Tertiary and Upper Cretaceous rocks in Japan reveal that stTAI is more sensitive to heating duration than R_O, although R_O is more sensitive to heating temperature.     

南海沉积物漫反射光谱反映的220ka以来东亚夏季风变迁

对南海越南岸外“太阳号”95航次17954孔220ka以来的沉积样品进行了漫反射光谱分析, 并从中提取F1和F2两个主因子及亮度和红度等漫反射光谱特征值, 发现漫反射光谱F1值和亮度反映了沉积物中的碳酸盐含量, 而漫反射光谱F2值和红度反映了沉积物中的铁氧化物含量, 后者可用作东亚夏季风的替代性指标.17954孔沉积物的漫反射光谱F2值显示, 倒数第二次冰消期东亚夏季风快速增长时间约在129ka; 本次工作还发现东亚夏季风在两次冰消期前的氧同位素2阶段和6阶段晚期各有一个异常强盛的时期.漫反射分析结果显示东亚夏季风主要受控于太阳辐射强度变化, 并明显地受低纬地区气候的影响.      

植物单叶偏振反射特征研究

简明地阐述了植物单叶偏振反射特征以及影响植物单叶偏振反射的主要因素 ,这对偏振光遥感的深入研究具有一定的理论和实践意义     

论砂岩储集岩相

储集岩相是以基本标志反映储集岩的沉积相、成岩变化以及油气显示面貌的。采用的标志包括：岩石学标志(沉积相、镜质体反射率),物性标志(三维孔喉比、配位数)以及有机地球化学标志(单有机包裹体光化学参数)。区分出的储集岩相类型不仅根据上述定量标志能进行自身评价,还可以编入相柱状图和古地理图进行预测和追索油气藏。依据由岩心或者岩屑制成双面抛光不加盖片的薄光片(岩心部分副样要浸注玫瑰红荧光剂并制成平行与垂直层理的三维薄光片),用显微镜光度法、显微付里叶红外谱和激光拉曼谱确定以上标志。