台湾岛以东A-24C及A-50C岩芯中的放射虫化石与沉积环境

根据对台湾岛以东海域A-24C,A-50C岩芯中放射虫化石的分析结果,并借助WP3岩芯有孔虫,δ^18O曲线分析,测试资料,对两岩芯地层作了对比与划分,结果显示：两岩芯的上部（A-24C为0～30cm,A-50C为0～35cm）属全新世沉积;下部（A-24C为30～234cm,A-50C为35～163cm）属晚期更新世沉积。 两岩芯中放射虫丰度、分异度的变化与黑潮主流线的摆动密度相关。末次冰期时的低海面导致黑潮主流线移至研究区（125℃E）以东,放射虫丰度,分异度出现低值,有的层位出现零值,而随着海面回升,黑潮逐渐移至现在的位置,放射虫的丰度,分异度出现高值,另外综合该区分析资料,推算两岩芯的平均沉积速率为A-24C岩芯全新世3cm,晚期更新世12.6cm,A-50C岩芯全新世2.9cm,晚更新世12.4cm,晚期更新世沉积速率均大于全新世。     

基于Landsat-8 的湛江东海岛地物分类研究

“宝钢湛江项目”的实施对近十年湛江东海岛的地物分布产生剧烈影响，尤其是工业用地。本文基于2013 年、2017 年和2021 年的陆地卫星8 号（Landsat-8） 数据对湛江东海岛进行地物分类，研究该区域近十年的用地变化趋势。以2013 年数据为参照：采用归一化水体指数（Normalized Difference Water Index，NDWI） 模型和谱间关系模型实现水陆分离，比对选择分离效果较优者以提取东海岛岸线；对比最大似然法、神经网络法和支持向量机法3 种监督分类方法，选择提取地物效果最优者应用于其余数据。基于Google earth 在线地图及无人机实测数据构建验证点集，使用混淆矩阵进行精度评价。结果表明：谱间关系模型的水陆分离效果较优，提取海岛岸线的精确度有明显提升；支持向量机法的分类总体精度和Kappa 系数最高，分类结果能较好地反映研究区的真实地物分布；汇总三年数据的分类结果，发现用于发展工业的土地面积增长突出且处于持续增长趋势。谱间关系模型与支持向量机法分别实现了对东海岛岸线和地物类型的准确提取，得出近十年研究区的用地变化趋势，能为研究区的用地规划提供参考。     

海南岛的海涂土壤及其开发利用

根据调查资料和采样分析,作者划分海南岛海涂土壤类型,并就机械组成、养分含量、盐渍化程度、粘土矿物组成等方面阐述海涂土壤特征。根据海涂土壤的性质及其生态环境特征进行开发利用,宜以海水养殖和晒盐为主,其中海水养殖可分为8个区。     

南极乔治王岛早第三纪古气候

根据植物化石证据,在早第三纪早、中期,南极乔治王岛地区曾出现过温暖、潮湿的气候,作者认为,当时南半球各板块的相对位置以及由此而引起的洋流的变化,很可能是造成这种温暖气候的主要原因。     

Mid and late holocene diatoms from ‘Water Supply Lake’, Baffin Island,N.W.T., Canada

Diatom analyses from a 40 cm sediment core from Water Supply Lake, northeastern Baffin Island, reveal 67 taxa of primarily benthic forms, strongly dominated by small Fragilaria spp. No major stratigraphic changes are noted in the diatom floral record, which encompasses the last 7000 years. In the uppermost 2 cm, there are increases in: a) F. virescens var. subsalina, b) the ratio of symmetric: asymmetric valves of F. construens, and c) species richness. These are interpreted as reflecting anthropogenic modifications of the lake (chlorination and deepening) associated with its use as a source of water for the community of Pond Inlet since 1979.     

Soil water dynamics and water balance on a tropical coral island

Understanding soil water dynamics and the water balance of tropical coral islands is important for the utilization and management of their limited freshwater resources, which is only from rainfall. However, there is a significant knowledge gap in the influence of soil water on the water cycle of coral islands. Soil water dynamics and the water balance of Zhaoshu Island, Xisha Archipelago were thus investigated using soil moisture measurements and the Hydrus-1D model from October 2018 to September 2019. Over the study period, vegetation transpiration, soil evaporation, groundwater recharge and storage in the vadose zone were approximately 196, 330, 365 and 20 mm, occupying 22%, 36%, 40% and 2% of annual rainfall total (911 mm), respectively. For the wet season (from May to October) these values became 75, 202, 455 and 40 mm, occupying 10%, 26% and 59% and 5% of the seasonal rainfall total (772 mm), respectively. During the dry season (from November to April), a dry soil layer between 40 and 120 cm depth of the soil profile was identified that prevented water exchange between the upper soil layers and the groundwater resulting in the development of deep roots so that vegetation could extract groundwater to supplement their water requirements. Vegetation not only consumes all dry season rainfall (140 mm) but extracts water deeply from groundwater (90 mm) as well as from the vadose layer (20 mm). As such, the vegetation appears to be groundwater-dependent ecosystems. The research results aid us to better understand the process of water dynamics on coral islands and to protect coral island ecosystems.     

Early Permian supra‐subduction assemblage of the South Island terrane,Percy Isles,New England Fold Belt,Queensland

Ultramafic‐intermediate rocks exposed on the South Island of the Percy Isles have been previously grouped into the ophiolitic Marlborough terrane of the northern New England Fold Belt. However, petrological, geochemical and geochronological data all suggest a different origin for the South Island rocks and a new terrane, the South Island terrane, is proposed. The South Island terrane rocks differ from ultramafic‐mafic rocks of the Marlborough terrane not only in lithological association, but also in geochemical features and age. These data demonstrate that the South Island terrane is genetically unrelated to the Marlborough terrane but developed in a supra‐subduction zone environment probably associated with an Early Permian oceanic arc. There is, however, a correlation between the South Island terrane rocks and intrusive units of the Marlborough ophiolite. This indicates that the two terranes were in relative proximity to one another during Early Permian times. A K/Ar age of 277 ± 7 Ma on a cumulative amphibole‐rich diorite from the South Island terrane suggests possible affinities with the Gympie and Berserker terranes of the northern New England Fold Belt.     

加拿大纽芬兰岛Indian Head Range地块格林威尔期二长花岗岩年龄、Nd-Hf同位素特征——块体属性与演化新证据

加拿大阿巴拉契亚造山带纽芬兰岛Humber带基底地块属性及地壳生长演化是近年来关注的科学问题,尤其是岛内西南部的Indian Head Range地块,其年龄组成与同位素特征研究对区域基底构造属性划分与对比至关重要。本文对Indian Head Range地块内的二长花岗岩岩体进行了锆石U-Pb定年,得到其²⁰⁶Pb/²³⁸U加权平均年龄值为1 149±4 Ma,代表该岩体的侵位年龄。这一定年结果表明该岩体具有中元古代晚期的年龄,为该地块格林威尔期岩浆事件的存在提供了新的年龄证据。Nd-Hf同位素分析结果显示,该二长花岗岩岩体εNd值为-2.3,εHf值介于+1.93～+3.65之间,两阶段Hf模式年龄介于1.84～1.73 Ga之间。结合前人研究,我们认为Humber带内各地块发育约1.5 Ga、1.15 Ga和1.0 Ga的3期花岗质岩浆事件,它们具有相似的Hf模式年龄值,暗示它们均来源于古元古代新生地壳物质的再造。带内格林威尔基底地块均为原地基底,且与劳伦大陆远端东部边缘具有一致的岩浆-构造演化史。以上研究对Humber带内格林威尔基底...     

热带海南岛地表和地下化学风化：对全球碳循环及海水Sr 同位素演化研究的启示

热带地区火山岛/岛弧的化学风化对全球碳循环和海水的Sr同位素演化均有着重要的作用。文章对中国热带海南岛的玄武岩、花岗岩小流域和大河流域进行了河水、地下水、雨水以及基岩和沉积物的综合研究,分析了水样和固体样品的元素含量和Sr同位素比值。结果显示,河床沉积物的化学蚀变指数（CIA）与⁸⁷Sr/⁸⁶Sr之间存在着一定的变化关系,而这主要归因于沉积物的阶段性差异风化：风化早期阶段以黑云母占主导,⁸⁷Sr/⁸⁶Sr较高。此后斜长石开始风化,⁸⁷Sr/⁸⁶Sr逐渐下降。在风化程度中等阶段,斜长石大量分解后,各种富钾矿物风化加剧,⁸⁷Sr/⁸⁶Sr值升至最高点。在高风化程度阶段,随着富钾矿物逐渐减少,稳定的风化残余物质占据主导,⁸⁷Sr/⁸⁶Sr值逐渐下降。与年轻的活火山岛——加勒比海小安的列斯群岛和印度洋的留尼汪岛相比（其地下化学风化速率2~5倍于地表风化速率）,由于相对较低的降水量和老死火山低的孔隙度,海南岛地下水的流量和固溶物总量（TDS）要低的多,导致海南岛的地下化学风化速率低于地表风化速率,仅与高纬的俄罗斯堪察加活火山岛相近,为小安的列斯群岛和留尼汪岛的约6%~25%,属于全球地下风化贡献最低的区域之一。海南岛玄武岩区的地表化学风化和CO2消耗速率高于法国中央高原和西伯利亚,略低于夏威夷和德干,而显著小于东南亚的爪哇岛和 吕宋岛。在温度相近的条件下,径流量对化学风化速率有着非常明显的控制作用。由于较低的年径流量,热带区域的海南岛,其对大气CO₂的消耗能力只是处于一个全球平均的范围内。