Deepwater Ventilation and Stratification in the Neogene South China Sea

Combined data of physical property, benthic foraminifera, and stable isotopes from ODP Sites 1148, 1146, and 1143 are used to discuss deep water evolution in the South China Sea (SCS) since the Early Miocene. The results indicate that 3 lithostratigraphic units, respectively corresponding to 21-17 Ma, 15-10 Ma, and 10-5 Ma with positive red parameter (a*) marking the red brown sediment color represent 3 periods of deep water ventilation. The first 2 periods show a closer link to contemporary production of the Antarctic Bottom Water (AABW) and Northern Component Water (NCW), indicating a free connection of deep waters between the SCS and the open ocean before 10 Ma. After 10 Ma, red parameter dropped but stayed higher than the modern value (a*=0), the CaCO3 percentage difference between Site 1148 from a lower deepwater setting and Site 1146 from an upper deepwater setting enlarged significantly, and benthic species which prefer oxygen-rich bottom conditions dramatically decreased. Coupled with a major negative excursion of benthic δ13C at ~10 Ma, these parameters may denote a weakening in the control of the SCS deep water by the open ocean. Probably they mark the birth of a local deep water due to shallow waterways or rise of sill depths during the course of sea basin closing from south to east by the west-moving Philippine Arc after the end of SCS seafloor spreading at 16-15 Ma. However, it took another 5 Ma before the dissolved oxygen approached close to the modern level. Although the oxygen level continued to stabilize, several Pacific Bottom Water (PBW) and Pacific Deep Water (PDW) marker species rapidly increased since ~6 Ma, followed by a dramatic escalation in planktonic fragmentation which indicates high dissolution especially after ~5 Ma. The period of 5-3 Ma saw the strongest stratified deepwater in the then SCS, as indicated by up to 40% CaCO3 difference between Sites 1148 and 1146. Apart from a strengthening PDW as a result of global cooling and ice cap buildup on northern high latitudes, a deepening sea basin due to stronger subduction eastward may also have triggered the influx of more corrosive waters from the deep western Pacific. Since 3 Ma, the evolution of the SCS deep water entered a modern phase, as characterized by relative stable 10% CaCO3 difference between the two sites and increase in infaunal benthic species which prefer a low oxygenated environment. Thesubsequent reduction of PBW and PDW marker species at about 1.2 Ma and 0.9 Ma and another significant negative excursion of benthic δ13C to a Neogene minimum at ~0.9 Ma together convey a clear message that the PBW largely disappeared and the PDW considerably weakened in the Mid-Pleistocene SCS. Therefore, the true modern mode SCS deep water started to form only during the "Mid-Pleistocene climatic transition" probably due to the rise of sill depths under the Bashi Strait.     

BP神经网络在矿产资源评价中的应用

简述BP神经网络的基本原理,通过实例阐述BP神经网络在矿产资源GIS评价应用方法,提出注意事项及如何提高评价应用效果.     

基于ArcEngine的管线系统的实现

城市综合管网是城市建设的重要组成部分,随着城市地理空间基础框架工程的推进和城市管网信息化的加速发展,城市管网数据将更加与基础地理数据融合为一体,并为城市建设提供基础服务。结合实际应用,介绍了Ar-cEngine在城市管线管理中的应用,以及管线数据库和基础地理空间框架库集成,对于基于GIS的综合管线系统开发具有借鉴和参考价值。     

基于数学形态学的第四系地层遥感影像分割

利用数学形态学的方法对遥感影像的第四系地层进行了影像分割实验。经实验结果得出,利用数学形态学的基本运算组合成的各种算子:高、低帽变换、滤波与阈值截取相结合的增强方法,通过选择合适的结构元素,对图像进行预处理后,就可以用形态学方法对第四系地层进行影像分割。经过处理的遥感影像,能够更有效地提取影像的目标。实验结果表明了本文所提的方法的有效性。最后,对形态学方法的不足之处和将来的研究方向展开了讨论。     

Variations in the Ice Phenology and Water Level of Ayakekumu Lake,Tibetan Plateau,Derived from MODIS and Satellite Altimetry Data

The alpine lakes on the Tibetan Plateau (TP) are highly sensitive to variations in climate changes, and the lake ice phenology and water level are considered to be direct indicators of regional climate variability. In this study, we first used 14 years of moderate resolution imaging spectroradiometer snow cover products to analyse the freeze dates, ablation dates, and ice coverage durations. The lake level changes during 2002–2015 were estimated, derived from satellite altimetry and Hydroweb data. Unexpectedly, the freeze dates of lake ice greatly advanced, and the ablation dates were markedly delayed. The complete freezing duration lengthened by approximately 77 days. As a result of the warm-wet climate in the northern TP, the lake area expanded from 770 to 995 km² during 2002–2015, and the water levels rose by 4.2 m in total, at a rate of 0.3 m/year. The progressive expansion of Ayakekumu Lake profoundly affected the ice phenology. Larger water volume with larger thermal capacity likely led to the delaying of ablation dates, with the freezing point depression caused by decreasing salinity. Some new narrow and shallow bays located in southern and eastern Ayakekumu Lake were conducive to early freezing of ice. Additionally, the changes in air temperature, precipitation, potential evaporation, and sunshine duration may be related to the prolonged ice cover duration since 2002. In sum, accurate measurements of lake ice and water levels are critical for understanding the water resource balance and hydrologic cycle in arid or semi-arid regions of China.     

形态参数下地表采动裂缝三维建模及可视化方法

实现对地表采动裂缝的三维建模及可视化能促进裂缝的形状、成因研究,并为开采沉陷监测和生态环境恢复提供科学支持。目前三维建模方法和软件主要面向建筑物、管道、地质体等地物地貌,若直接应用于地表裂缝的建模与表达会存在野外测绘工作量大、形态规律表达不准确、呈现不逼真等问题。本文结合三维地形建模、分形、空间插值等理论,提出了基于几何形态参数的地表裂缝三维建模方法,并利用ArcEngine平台实现了对裂缝的三维可视化;选取甘肃省东峡矿区为试验区,根据裂缝分布与形态预计参数,实现了对区域内裂缝的模拟,并通过与实测数据和高分辨率影像进行对比,验证了该方法能真实逼真呈现裂缝的形态、延伸与细节信息。     

最小二乘配置法优化的REHSM模型及应用

REHSM模型由于顾及了板内形变,实际上是一种对传统刚体板块运动模型的优化模型,但鉴于其假设条件为板内应变均匀,导致其可能难以适用于复杂地质构造区域。本文提出了将板内偏离整体旋转和均匀应变的块体形变部分看作是干扰信号,利用信号对块体内部偏离整体旋转与均匀应变的形变部分进行补偿,建立了一种优化的弹性运动及形变分析模型;对最近几期中国大陆构造环境监测网络在环渤海区域的速度场数据进行拟合分析,结果表明,新方法能有效地精化REHSM模型,具有更高的拟合精度。     

城市建筑水平特征对城市热环境效应的影响——以大连市中山区为例

以大连市中山区的遥感和建筑等多源数据为基础,结合单窗算法和相关分析方法,研究分析了2002—2014年研究区的地表温度空间分异特征及地表温度与建筑密度的相关性。研究结果表明:(1)2002—2014年地表温度高温区域多分布在中山区西北部、解放路和中南路的沿线,且温度增加明显,东北部由于填海造陆温度明显升高;(2)高密度和较高密度的地块主要分布在青泥洼天津街商业区,大部分低、较低、中密度地块分布在解放路和中南路沿线;(3)2002年、2014年,地表温度与建筑密度呈现中等相关性,相关系数分别为0.514、0.537。     

地下管线信息综合管理的探索与实践——以浦东新区为例

为解决地下管线信息准确性不高、更新不及时、共享应用程度低等常见问题,提出明确地下管线信息综合管理机构,创新领导管理决策-执行协同网络-多层次沟通渠道的综合管理机制,构建管线信息一门式集中管理模式。总结了浦东新区地下管线信息管理经验,提出全生命周期信息沟通与采集机制,健全管线跟测与汇交体系,建立信息管理平台及常态化保障措施。     

PS-InSAR和SBAS-InSAR技术对昆明主城区地面沉降监测的对比分析

以昆明主城区为例,分别利用PS-InSAR和SBAS-InSAR技术对2014—2017年间29景升轨Sentinel-1A数据进行沉降监测,对比两种技术得到的沉降结果,进行剖面图分析与时序分析。结果表明,PS-InSAR和SBAS-InSAR技术监测结果具有一致性、相关性和可靠性。研究发现,昆明市沉降漏斗主要位于居民区、地铁、道路、高速公路以及滇池等区域,最大年沉降速率可达-39.580mm/a,累积沉降量达到85mm。研究表明,昆明主城区地面沉降主要由于近几年城市和轨道交通建设的飞跃发展,导致居民区和交通网络密集,地面载荷增加,地下隧道开挖与地下水开采等原因引起地面软土地层下沉。