Climate variability in central China over the last 1270 years revealed by high-resolution stalagmite records     

《Quaternary Science Reviews》2003,22(5-7):691-701

Oxygen and carbon isotopic variations in the upper section of a stalagmite (SF-1) from Buddha Cave (33°40′N 109°05′E) dated by ²³⁰Th/²³⁴U ²¹⁰Pb and lamination counting to a time resolution as fine as 1–3 years have recorded climate changes in central China for the last 1270 years. The changes include those corresponding to the Medieval Warm Period Little Ice Age and 20th-century warming lending support to the global extent of these events. The isotopic records also show cycles of 33, 22, 11, 9.6, and 7.2 years. The 33-year cycle could well represent the ∼35-year periodicity of climate fluctuations previously recognized in China and Europe. Cycles of 22, 11, and 9.6 years have often been associated with the Sunspot or lunar-orbit variations. The 7.2-year cycle was recently identified also in tree-ring records from an area close to Buddha Cave. These cycles suggest that external forcing (e.g. solar irradiance) may affect the summer monsoon over eastern China. The general consistency between the climate characteristics inferred from the stable isotope records of SF-1 and those from other proxy records underscores the value of stalagmites as recorders of paleoclimate.  相似文献   

Basalts of the Eastern Deccan Volcanic Province,India     

《Gondwana Research》2002,5(3):649-665

The Mandla lobe in the eastern part of the Deccan volcanic province represents an isolated lava pile having a thickness of ∼900 m. The large thickness of this lava pile and its spatial detachment from the western Deccan outcrop points to a plausible second source. The stratigraphic configuration of the central and eastern Deccan lava sequences and their possible stratigraphic correlation are primarily based on geology and chemical signatures of the lava flows. Based on variations in the incompatible element ratios, the lava sequences of Chindwara, Jabalpur-Seoni and Jabalpur-Piparia sections were classified into four informal formations showing similarity with the southwestern formations. Major and trace element abundances in fifteen lava flows of Jabalpur area are similar to that of the southwestern Deccan lava flows. It has been found that the Ambenali Fm. and a few Khandala and Bushe Fm. flows are present in the northeastern Deccan. The regional mapping and detailed petrographic studies coupled with the lateral tracing have enabled the recognition of thirty-seven physically distinct lava flows and is justified by their major-elemental chemistry. The ‘intraflow variations’ studied in some of the flows is very low for most of the major oxides. These thirty-seven lava flows are grouped into eight chemical types. The order of superposition in this sequence reflects that the older flows occur in the west of the outlier at the Seoni-Jabalpur-Sahapura sector whereas, the younger flows are confined to the Dindori-Amarkantak sector in the east. The spatial disposition of the lava flows suggests that the structural complexity in the lava flow sequence in the Mandla lobe lies between Jabalpur and Dindori. The juxtaposition of distinct groups of lava flows are observed near Deori (flows 1 to 4 abeted aginst flows 5 to 14) and Dindori areas. At Dindori and towards its south the distinct lava packages (flows 15 to 27 and flows 28 to 37) are juxtaposed along the course of Narmada river. The possible explanation for this could be the presence of four post-Deccan faults at Nagapahar, Kundam, Deori and Dindori areas. The vertical shift of chemically distinct lava packages at different sectors in the outlier contravenes the idea of small regional dip and favours the presence of four NE-SW trending post-Deccan faults. Major geochemical breaks, when traced out from section to section, exhibit shifting in heights by approximately 150 m near Nagapahar and 300 m near Deori and Dindori areas. The field, petrographic and major-oxide data sets considered in conjuction with the magnetic chron reversal heights, support the inference that four faults trending NE-SW are present in the Mandla lobe.A commonality in the mineralo-chemical attributes of the infra (Lametas)-/inter-trappean as well as weathered Deccan basalt further favours their derivation from Deccan basalt, implying the availability of Deccan basalt during the Maastrichtian Lameta sedimentation. This observation does not match with the models suggesting an extremely short duration of Deccan volcanism (<0.5 Ma) at the KTB, but is congruent with the models advocating a more prolonged Deccan volcanism.  相似文献   

江苏非物质文化遗产的时空分布及其影响因素   总被引：2，自引：0，他引：2  

韩顺法  徐鹏飞  马培龙 《地理科学》2021,41(9):1598-1605

以江苏为例,运用地理学相关方法将非遗的时空分布可视化,并探讨其分布的影响因素。研究表明：江苏非遗在时间上呈“迂回向南”发展轨迹,其数量和类型在不同阶段具有明显差异;在空间上呈聚集性分布,分别在苏州、扬州、南京、常州、镇江和南通形成6个高密度核心;通过地理探测器分析,得知河流水系、政策导向、历史文化和经济等因素对非遗的时空分布有较大影响。由此得出重视江苏大运河文化带建设、将非遗纳入文化生态系统内整体性保护、正视非遗与经济合理互动等启示。  相似文献   

Morphometry and Morphostructural Studies of the Parts of Gola River and Kalsa River Basins,Chanphi-Okhalkanda Region,Kumaun Lesser Himalaya,India     

Lal. Kumar  Joshi  G.  Agarwal  K. K. 《Geotectonics》2020,54(3):410-427

Geotectonics - Study of morphometric parameters such as stream length (Lu) and stream length ratios (Rl), bifurcation ratio (Rb), drainage density (D), form factor (Rf), circularity ratio (Rc),...  相似文献   

The Paleogene vegetation and petroleum system in the tropics: A biomarker approach     

《Marine and Petroleum Geology》2017

The present study investigates the biomarker signatures of sediments and crude oils to infer the paleovegetation from the two petroleum systems of Assam Basin, eastern India. They are classified as the Paleocene-middle Eocene and the middle Eocene-Oligocene petroleum systems. The sediments are oil and gas prone with an early catagenetic stage of thermal evolution. Here we report tricyclic diterpanes such as rimuane, pimarane, rosane and isopimarane along with tetracyclic diterpanes: ent-beyerane, phyllocladane, kaurane from Paleocene-Eocene coal-bearing sediments and crude oils. These diterpane biomarkers attest dominant contribution from conifers, possibly from Podocarpaceae and Araucariaceae. However, diterpanes are not detected in Oligocene sediments and oils. Crude oils from both Paleocene-Eocene and Oligocene reservoirs and organic rich sediments contain angiosperm biomarkers such oleanane and related triterpanes along with bicadinane, a biomarker specific for the Dipterocarpaceae family of angiosperms. The equatorial position of India during early Paleogene along with the presence of angiosperm signatures including Dipterocarpaceae and gymnosperms reflect the emergence of tropical rainforest elements in eastern India. Absence of diterpenoids in Oligocene samples and difference in angiosperm parameters from Paleocene-Eocene samples suggests a change in source vegetation and organofacies.  相似文献   

State studies of Earth's plasmasphere: A review     

A.K. Singh  R.P. Singh 《Planetary and Space Science》2011,59(9):810-834

The plasmasphere sandwiched between the ionosphere and the outer magnetosphere is populated by up flow of ionospheric cold (∼1 eV) and dense plasma along geomagnetic field lines. Recent observations from various instruments onboard IMAGE and CLUSTER spacecrafts have made significant advances in our understanding of plasma density irregularities, plume formation, erosion and refilling of the plasmasphere, presence of thermal structures in the plasmasphere and existence of radiation belts. Still modeling work and more observational data are required for clear understanding of plasmapause formation, existence of various sizes and shapes of density structures inside the plasmasphere as well as on the surface of the plasmapause, plasmasphere filling and erosion processes; which are important in understanding the relation of the process proceeding in the Sun and solar wind to the processes observed in the Earth's atmosphere and ionosphere.  相似文献   

黄海南部野生银鲳和鮸鱼的耳石元素微化学研究     

熊瑛  刘洪波  姜涛  刘培廷  汤建华  仲霞铭  杨健  吴磊  高银生 《海洋学报》2015,37(2):36-43

利用电子显微探针元素分析技术(EPMA)对黄海南部野生银鲳和鮸鱼的耳石进行了锶和钙沉积特征的初步分析。定量线分析结果表明,两种鱼类耳石的Sr/Ca之间存在显著的种间差异。银鲳耳石Sr/Ca比,在耳石核心及相邻处为低值区(5.86±0.92);3段Sr/Ca高值区分别为近核心部(7.88±1.28)、第1龄处(9.44±1.82)及耳石边缘(7.91±1.38);揭示银鲳孵化和早期发育应需要盐度适中的生境,当龄鱼在后期的生长中需洄游经过两段高盐生境(其中之一在第1龄时)。鮸鱼耳石Sr/Ca比波动表现为耳石核心处(7.72±0.97)高于其余部分,反映了鮸鱼孵化及初期发育阶段可能生活在高盐度生境,而当龄鱼随后阶段的生长和发育过程则会洄游至盐度有所降低的生境中进行。  相似文献   

红壳色文蛤选育子代各壳色的形态分化及养殖效果的比较   总被引：2，自引：0，他引：2  

吴杨平  姚国兴  陈爱华  张志伟  张曹进  张雨 《台湾海峡》2012,31(3):412-419,446

以红壳色为目标性状,于2009年进行了文蛤(Meretrix meretrix)的群体选育研究,建立了红壳色选系子一代(Fl),对子一代壳色种类、分布频率及其数量性状进行了统计、测量和分析,并对各壳色的形态、生长速度做了研究.结果表明,文蛤壳色具有多态性,红色、黄色、白双、黄双、波纹的分布频率分别为75.58%、8.55%、0.53%、14.83%、0.50%.红壳色亲本的子代中出现红色∶花色=3∶1,符合孟德尔遗传模式.聚类分析与欧氏距离矩阵结果表明,文蛤波纹与黄色遗传距离最近,白双与黄双遗传距离相近,与红壳色的遗传距离最远.主成分分析显示白双文蛤与黄双文蛤在空间分布上相对重叠,波纹文蛤与黄色文蛤具有较高的重叠率,而红壳色文蛤相对分散,从而进一步说明5种壳色文蛤的遗传距离关系.经过1a同池养殖,子代壳长多数已达到10～30 mm,红壳色文蛤的日生长率为0.20%,花壳色文蛤的日生长率为0.18%,且红壳色文蛤的相对比较生长速度比花壳色文蛤快10.41%.红壳色文蛤选育子代的壳长与壳宽、壳高、粒重存在一定的回归关系.红壳色文蛤壳长对壳宽、壳高、粒重的回归方程分别为:y1=0.502 4x1-0.556 0(R2=0.992 0)、y3=0.8103x3+0.620 0(R2=0.995 6)、y5=0.000 3x25.9029(R2=0.991 9),花壳色文蛤壳长对壳宽、壳高、粒重的回归方程分别为:y2=0.495 3x2-0.419 2(R2=0.990 9)、y4=0.798 5x4+0.793 5(R2=0.995 6)、y6=0.000 4x26.845 8(R2=0.993 4).研究结果为文蛤的红壳色定向选育奠定了理论基础.  相似文献   

欧氏聚类算法支持下的点云数据分割     

陈向阳  杨洋  向云飞 《测绘通报》2017,(11):27

欧氏聚类算法是多元统计中的一种重要分类方法,可以将其应用于测绘领域中点云数据的分割。本文首先计算点云数据中两点之间的欧氏距离,将距离小于指定阈值作为分为一类的判定准则;然后迭代计算,直至所有的类间距大于指定阈值,完成欧氏聚类分割。具体步骤为：①利用Octree法建立点云数据拓扑组织结构;②对每个点进行k近邻搜索,计算该点与k个邻近点之间的欧氏距离,最小归为一类;③设置一定的阈值,对步骤②迭代计算,直至所有类与类之间的距离大于指定阈值。试验证明,欧氏聚类算法对不同测量技术手段获取的点云数据均具有适用性,可以成功对点云数据进行分割,分割效果良好。  相似文献   

高校“地图学”课程思政元素挖掘与课堂融入     

黄翌  陈建伟  刘潇潇  王梦琦 《测绘与空间地理信息》2022,45(1):19-21

高校专业课的课程思政建设是高校思想政治工作的基本载体。“地图学”是测绘工程、遥感科学与技术、地理信息科学、地理科学等本科专业的基础课,在测绘、地理等学科的课程思政建设中具有基础性地位。本文依据教学实践,归纳了地图学课程中与课程思政相结合的知识点,并介绍了在教学中如何巧妙、潜移默化地融入思政元素,在地图学课程教学过程中做到能力培养和素质提升共同进步。  相似文献