Asian Hydroclimate Changes and Mechanisms in the Preboreal from an Annually‐laminated Stalagmite,Daoguan Cave,Southern China

One-year-resolved and annually-counted stalagmite multi-proxies(δ~(18)O, δ~(13)C, and layer width) from Daoguan Cave, Guizhou Province revealed detailed variability regarding the Asian Summer Monsoon(ASM) and local humidity across Bond events(BE) in the Preboreal. During BEs 8 and 7, 1.5‰ enrichments in δ~(18)O values were generally consistent with high-to low-latitude climate changes. In detail, the decadal-scale minor δ~(18)O oscillations in BE8 were broadly less than the mean value, in contrast to the significant changes in local soil moisture derived from the δ~(13)C values and layer records. In the mid-BE7, δ~(18)O variability was generally above the average level, and higher-amplitude variations were observed in the three proxy indicators. Wavelet analysis on the total δ~(18)O time series and across the specific time windows of BEs 8 and 7 identified periodicities of about 130, 60, and 20-a, respectively. Exceptionally strong in BE7, the 60-a cycle, pervasively observed in instrumental studies, became prominent starting at 11.4 kaBP. Thus, glacial background conditions are important for suppressing the ASM intensity in BE8, while during BE7, tropical hydrological circulations were potentially actively involved. Consequently, climate internal oscillations, analogous to modern conditions, might have occurred in the distant past once the link between the tropical ocean and atmosphere was established as occurs today.     

鄂尔多斯盆地中-晚三叠世事件沉积对印支运动Ⅰ幕的指示

中三叠世末的印支运动Ⅰ幕在华北板块东部明显地表现为中、上三叠统间的不整合,而西部鄂尔多斯盆地的三叠系内部一般为连续沉积,使得印支运动Ⅰ幕难以识别.本文通过观察延长组的钻井岩芯,分析了湖底扇、震积岩、凝灰岩和油页岩等事件沉积体的发育特征及时间序列,显示出它们发育的高潮期皆为长7油层组沉积初期,时间上与印支运动Ⅰ幕相耦合,...     

Paleoceanographic evolution and chronostratigraphy of the Aptian Oceanic Anoxic Event 1a (OAE1a) to oceanic red bed 1 (ORB1) in the Gorgo a Cerbara section (central Italy)

We performed a detailed study of the stratigraphic transition of Oceanic Anoxic Event 1a (OAE1a) to oceanic red bed 1 (ORB1) from the classic Gorgo a Cerbara section in the Umbria region of central Italy. We focused on a 25.5-m-thick stratigraphic succession, from which we analyzed 305 samples for total organic carbon (TOC), CaCO₃, magnetic susceptibility, diffuse reflectance spectrophotometry and the stable carbon and oxygen isotopic composition of both bulk samples and organic matter. In the Gorgo a Cerbara section, the Selli Level of OAE1a (∼1.81 m thick) consists of laminated to bioturbated dark gray to black mudstones and shales with medium to dark gray radiolarian-rich silty to sandy layers and a maximum TOC content of 20.22%. The carbon isotopic values show a negative excursion (C3 stage, ∼0.14 m) at the base of the Selli Level, followed by a stepwise positive excursion (C4–C6 stages, ∼1.67 m) in the upper part of the Selli Level. The transition from OAE1a to ORB1 (∼3.19 m thick) is characterized by bioturbated greenish gray cherty limestones and marly limestones with subordinate marls, corresponding to stable carbon isotopic C7 stage and lasts for ∼0.75 Ma. The ORB1 interval (∼13.15 m) consists of reddish marly claystones, dark-red marlstones, red marly limestones and red calcareous shales which indicate a highly oxic environment. Our results reveal a stepwise transition from a predominantly mesotrophic and dysoxic to anoxic environment at the time that the OAE1a black shales were deposited to an oligotrophic and oxic environment during the transitional interval and finally to highly oxic conditions during the ORB1 interval. The nannoconid crisis occurs at the top of the C2 stage, just 0.34 m below the negative excursion in δ¹³C isotopic values. The massive CaCO₃ dissolution phase occurs 0.25 m above the negative excursion; it persisted for 0.85 Ma and probably resulted from excess CO₂, ocean acidification, and carbonate compensation depth (CCD) shoaling. Deposition of massive black shales occurs at the base of the C6 stage and lasted for 0.4 Ma.     

黄土高原马兰黄土记录的MIS 3温湿气候

对位于关中盆地的大荔地区甜水沟和垣雷两个剖面末次冰期盐和有机质碳同位素组成、磁化率和频率磁化率进行了系统研究,初步讨论了MIS3后期(即MIS3a)的"高温大降水事件"对黄土高原南部气候和植被的影响.在40～30kaB.P.的MIS3a时期,大荔地区气候总体表现为湿润、温暖,植被覆盖程度高,植被中C4植物的相对含量增加,土壤发育较好.中国大陆黄土-古土壤序列在MIS3的磁化率较之末次冰期的其他时段均有所增加,但不同地区的增幅各不相同.     

The Triggering Mechanism for the largest Aftershock （ Ms = 6.3 ） of the Great Luhuo Event （ Ms =7.6） in 1973

INTRODUCTIONInrecentyears,thestudiesontemporaryandspatialfeaturesofaftershocksaroundepicentersandtheirmechanismhavebeenanimportantpartofseismology .Theaftershocksrelatedtothestateoffaultruptureofmainshockscouldbedistinguishedasthreetypes,theyare:(1)theaftershocksalongbro kenfaultsegments;(2 )theaftershocksontheborderoftherupturebelt;and (3)theaftershocksin ducedbymainshocksthatoccurredbeyondthemainruptures.Themechanismofthefirsttypemightbetheadjustmentoftheremnantasperityinthefaultplaneofm…     

辽东青城子矿集区大理岩碳—氧同位素组成及其对含矿层位对比及深部找矿的指示

辽东青城子矿集区金—多金属矿床严格受古元古代辽河群大石桥组大理岩及盖县组变质碎屑岩过渡带“硅—钙面”附近层间或近层间构造带控制,含矿层位的精确对比有助于区域及深部找矿预测。本文对青城子矿集区85件大理岩样品开展了碳—氧同位素测试,其中大石桥组中—下部厚层不含矿大理岩（普遍被古元古代基性岩床侵入）的??13CV-PDB为2. 1‰~6. 1‰,普遍具有明显的碳同位素组成正漂移,其原岩沉积于洛马贡迪—贾图利（Lomagundi—Jatuli）事件后期;而大石桥组上部中薄层含矿大理岩的??13CV-PDB为-6. 4‰至3. 0‰,碳同位素组成正漂移不明显,其原岩沉积于洛马贡迪—贾图利事件之后;矿区东南部原定的“南辽河群”“高家峪组”碎屑岩内大理岩夹层的??13CV-PDB为-2. 8‰至0‰,无明显碳同位素组成正漂移,与胶—辽—吉带北部“北辽河群”高家峪组大理岩强烈碳同位素正漂移特征明显不同,其原岩也沉积于洛马贡迪—贾图利事件之后。碳—氧同位素组成及岩性对比揭示,青城子矿集区东南部被认定为金—多金属矿体底板的“高家峪组”浅粒岩地层的层位与大石桥组上部地层相当,沉积时代晚于鞍山地区“北辽河群”高家峪组地层。结合前人研究及找矿勘查成果,认为林家三道沟、小佟家堡子、高家堡子—风银大地矿区深部可能存在有多个“硅—钙面”及含矿层位,具有很好的成矿潜力及找矿前景,深部勘探的终点应该到达大石桥组中—下部厚层大理岩段,即有变质基性岩床侵入、并具有碳同位素组成正异常的厚层状大理岩段。     

1997年1月事件行星际扰动在三维背景太阳风中传播的数值模拟

利用一个三维的MHD模式,从数值预报的角度出发,以1997年1月事件的有关太阳观测为依据,构造比较符合物理实际的边值条件,通过三维数值模拟得到了稳定的比较接近真实的太阳风背景场.结果显示此次事件太阳风背景场的磁场关于赤道面不对称,有较明显的倾斜和扭曲,同时磁场较弱;等离子体各参量相对于事件的太阳源为东西和南北不对称结构.本文数值模拟了磁场南北分量Bθ的不同取法对背景场的影响,结果表明在源表面磁场有明显倾斜的情况下,内边界处磁场南北分量不宜假设为零.在此基础上,初步数值研究了行星际扰动在三维背景场中的传播过程,并与WIND卫星的观测进行了对比.     

Planktonic foraminifera and sea surface temperature (SST) of the Xisha Trough, South China Sea since Last Glaciation

South China Sea is the largest marginal sea of the Western Pacific between the Pacific Ocean and Asia Continent. It has been influenced by both the Pacific Ocean and continental climate. Its continental margins are broad in north and south, narrow in west. There are many islands in east. A large amount of siliciclastic sediments derived from peri-continents and islands were trans-ported into the sea[1], in which significant information of paleoceanography and paleoclimate and paleoenvironm…     

全球数字地震台网事件带的文件和数据格式

全球数字地震台网所积累的大量地震波资料已经成为研究地震活动性、震源机制、地壳上地幔结构等最基本的数据源。为了使用全球数字地震台网事件带,必须了解其文件类型和内容以及数据格式。本文介绍了上述有关情况。特别是本文介绍了全球数字地震台网事件带中所包含的新的数据格式,弥补了这方面资料的不足。     

1989年3月13日武昌地区太阳耀斑事件效应的观测结果

1989年3月13日太阳耀斑事件产生了丰富的地球物理效应。耀斑激波和耀斑粒子流引起强烈地磁暴。在武昌地区,磁暴急始发生于地方时3月13日09h30min,其初相期持续10小时(3月13日09h30min—19h20min),主相期持续13小时(3月13日19h20min—3月14日08h20min),至3月16日05h20min始恢复平静(图1)。