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Controlled by climate changes, there were three large-scale transgressions and regressions around the Bohai Sea during the late Quaternary, which were accepted by most geologists. However, a big controversy still exists about the time when the transgressions occurred separately. In order to find out the process of the paleoenvironmental changes around the Bohai Sea in the late Quaternary, the foraminifera assemblages from a new borehole Lz908 in the southern coast of the Laizhou Bay were studied, and then the transgressive strata were indentified. Combined with accelerator mass spectrometry radiocarbon 14C（AMS14C） and optically stimulated luminescence（OSL） ages, the occurrence time of these transgressions were re-determined. The result showed that three major large-scale transgressions occurred separately at the beginning of marine isotopic stage 7（MIS7）, the last interglacial period（MIS5） and the Holocene. In addition, a small-scale transgression occurred in the mid-MIS6, and the corresponding transgressive stratum was deposited. The transgressive deposition of MIS3 was also discovered in this study. However, the characteristics of the foraminifera indicated the environment during this period was colder than that in the MIS5. By comparison with the global sea-level changes, the paleoenvironmental changes around the Bohai Sea in the late Quaternary can be consistent with the global climate changes. 相似文献
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基于卫星高度计的北极海冰厚度变化研究 总被引：5，自引：3，他引：2
A modified algorithm taking into account the first year(FY) and multiyear(MY) ice densities is used to derive a sea ice thickness from freeboard measurements acquired by satellite altimetry ICESat(2003–2008). Estimates agree with various independent in situ measurements within 0.21 m. Both the fall and winter campaigns see a dramatic extent retreat of thicker MY ice that survives at least one summer melting season. There were strong seasonal and interannual variabilities with regard to the mean thickness. Seasonal increases of 0.53 m for FY the ice and 0.29 m for the MY ice between the autumn and the winter ICESat campaigns, roughly 4–5 month separation, were found. Interannually, the significant MY ice thickness declines over the consecutive four ICESat winter campaigns(2005–2008) leads to a pronounced thickness drop of 0.8 m in MY sea ice zones. No clear trend was identified from the averaged thickness of thinner, FY ice that emerges in autumn and winter and melts in summer. Uncertainty estimates for our calculated thickness, caused by the standard deviations of multiple input parameters including freeboard, ice density, snow density, snow depth, show large errors more than 0.5 m in thicker MY ice zones and relatively small standard deviations under 0.5 m elsewhere. Moreover, a sensitivity analysis is implemented to determine the separate impact on the thickness estimate in the dependence of an individual input variable as mentioned above. The results show systematic bias of the estimated ice thickness appears to be mainly caused by the variations of freeboard as well as the ice density whereas the snow density and depth brings about relatively insignificant errors. 相似文献
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渤海南部Lz908 孔海陆交互沉积的粒度特征及其对沉积环境的指示 总被引：3，自引：0，他引：3
对采自莱州湾南岸的钻孔沉积物样品进行了粒度测试和分析。样品平均粒径介于3.3Φ~6.8Φ,以极细砂和粗粉砂为主,含有少量的黏土质;分选较差;偏度表现为正偏和极正偏;沉积物粒度表现为正态、正态-尖锐和尖锐,少数表现为平坦和极尖锐。粒度象图指示了历史时期持续高的初始沉积水动能和多种沉积环境的变化,粒度参数散点图反映了多种动能影响了沉积物的沉积改造,综合判别分析对沉积环境的限定,得到了莱州湾南岸沉积物受到河水径流、潮流、波浪等共同作用形成。沉积物总体反映了莱州湾南岸长时期处于河流相和三角洲相的沉积环境,少数较细的粒度表现可能与研究区的多期海侵过程相对应。结果表明了粒度的综合分析对渤海南部的沉积环境有良好的辨识,是判断沉积环境的重要指标。 相似文献
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潮汐波动具有稳定的周期性,当地下水受其影响时,这种周期性在地下水位变化中必会有所反映,但同时也会受到人为开采地下水、降雨等因素的影响而很难被识别出来。通过谱分析认为莱州湾南岸地下水位同潮位共同存在12和24h两个主要周期,采用傅立叶变化与去趋势分析结合的方法提取出了地下水位中受潮汐影响的频率成分,并利用自相关分析的方法对处理后的地下水位数据与潮位数据进行了对比分析。结果显示,虽然莱州湾南岸地下水受人为开采地下水影响显著,但通过去除长期趋势和提取频率的方法可以有效提取冬季地下水位中受潮汐作用影响的因素,从而为其他研究提供了一种有效的原始数据处理方法。 相似文献
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针对莱州湾南岸咸水入侵区地下水质连续、渐变和边界模糊的特征,利用规格化变换对莱州湾南岸地下水化学组分数据进行标准化,采用夹角余弦法作为相似系数,用平方法计算传递闭包构造模糊等价矩阵进行模糊聚类分析,将莱州湾南岸地下水划分为3类并绘制其平面分区图.在此基础上,用探索性数据分析技术的箱线图分别识别各类地下水各组分的分位数、中位数、极值等数据分布情况,并结合 Radial 图绘制各类地下水各组分均值;利用基于 CA 舒卡列夫分类方法的 Piper三线图识别了各类地下水的水化学类型;最后在相关分析基础上选取代表性指标绘制等值线图,结合模糊聚类分区探讨了分区各指标的空间结构特征及内在机理.综合上述分析,定义玉区为海水入侵重点治理区,域区为海水入侵综合防范与整治区,芋区为卤水区. 相似文献
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为了解潮汐对滨海地区地下水位的影响,为相关水利工程建设和水资源开发利用提供依据,文章根据莱州湾南岸的水文观测井和潮位站的观测数据,采用时间序列分析方法和互相关分析方法,研究地下水位相对于潮位的变化频率和滞后性。研究结果表明:由于受地下卤水开采的人为干扰,与潮位相比,地下水位在较低频率时振幅较高;去长期趋势处理对于排除人为干扰效果明显,地下水位的频率振幅与潮位波动规律一致,即均存在明显的12h和24h的周期,但大部分观测井的地下水位受24h周期影响较大,这与潮位差异显著;互相关分析进一步证实地下水位与潮位具有相同频率,潮汐向陆地侵入对地下水位的影响显著,地下水位相对于潮位的滞后时间随其距平均高潮线水平距离的增加迅速上升,二者呈抛物线关系。 相似文献
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灾害链是在时间上有先后、空间上彼此相依、成因上相互关联,破坏性极强的呈链式结构的多种灾害。由于灾害链的形成与演化具有叠加、放大和链式效应,已经成为灾害研究的热点和难点。受全球气候变化和人为因素的双重影响,海岸带地区成为地球上最活跃、最脆弱的区域。海水入侵和土壤盐渍化成为海岸带地区面临的主要地质灾害,威胁生态安全和人类生存环境,这2种灾害相继发生、相互关联,构成海水入侵-土壤盐渍化灾害链。归纳总结了灾害链研究进展,阐述了海水入侵-土壤盐渍化灾害链的演化特征和研究中的关键科学问题,展望了海水入侵-土壤盐渍化灾害链研究趋势。 相似文献
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