末次水消期以来气候期划分的准确定位与定年     

覃嘉铭  袁道先  林玉石  张美良  章程  王华  冯玉梅  涂林玲  杨琰  程海  R.Lawrence.Edwards  冉景丞  陈会明 《地球学报》2005,26(Z1):209-212

对贵州荔波董歌洞D4石笋的再次高密度230Th测年及碳、氧同位素分析，在16 ka 以来的部分，平均分辨率达 18a 。研究表明，氧同位素记录除反映季风的强弱变化外，能更好地揭示 H1，BA，YD以及全新世中 9.1ka，8.2ka、4.6ka 气候突变事件。碳同位素记录和沉积速率则能更好地反映气候干湿的变化。石笋记录对气候期的正确划分及突变事件的准确定位及定年，可为全球变化其他记录的研究提供一个可靠时间系列的基准标尺。  相似文献   

福建省泉州市第四纪沉积物粒度特征及沉积环境分析   总被引：3，自引：0，他引：3       下载免费PDF全文

张璞  陈建强  田明中  朱金芳  黄宗林  江春亮 《盐湖研究》2005,13(2):25-33

对福建省泉州市钻孔,进行详细的第四纪沉积物粒度分析,同时结合地质背景、岩性等资料,得出了研究区第四纪以来沉积环境及其演变的认识。采用MS-2000型激光粒度分析仪进行测试,所测数据利用计算机整理,绘制出沉积物粒度频率曲线、概率累积曲线和粒度众数分布曲线图。根据曲线变化情况,进行沉积环境及其演变解释。区内第四纪沉积环境和沉积物的成因类型分为3个类型,晋江河道以冲积相为主,山前高地以洪冲积为主,盆地主体区域以海湾相为主。第四纪以来泉州盆地环境演化经历了:更新统中期龙海组洪积和洪冲积→更新统晚期东山组洪积和洪冲积→全新统长乐组海湾相沉积。  相似文献   

Refinement of three-dimensional multilayer models of basins and crustal environments by inversion of gravity and magnetic data   总被引：2，自引：0，他引：2  

Luis A. Gallardo  M.A. Prez-Flores  E. Gmez-Trevio 《Tectonophysics》2005,397(1-2):37

The sensitivity of gravity and magnetic data to deep structures and the broad availability of regional data sets and surveys of high resolution make them suitable for determining detailed three-dimensional (3D) models of the subsurface. However, the sole consideration of gravity and magnetic information cannot properly resolve heterogeneous 3D environments. Advocated to solve this problem, we present an automated refinement technique for three-dimensional multilayer models as conditioned by gravity and magnetic data and by meaningful geometrical and physical constraints. We construct our model by an aggregate of rectangular prisms and aim to estimate their bottom depths, which define the geological layers. We summarize mathematically our concept of refinement in an objective function that includes the misfit to the data, the similitude to an a priori geological–geophysical model, and the smoothness of the relief of the layers. Importantly, our objective function also includes inequality constraints that prevent the superposition of layers and integrate the surface and borehole geology with the multilayer deep model. The objective function is solved using quadratic programming in a stable iterative scheme. The resulting algorithm is tested on synthetic data and applied to crustal and sedimentary basin environments from southern Baja California, Mexico. The assimilation of the geological and geometrical constraints to the inversion process produces models that correlate with the surface geology and reveal the three-dimensional features of the subsurface.  相似文献   

L'Arenig–Llanvirn du Haut Atlas occidental et central (Maroc). Environnements sédimentaires,paléogéographie et contrôle de la sédimentation     

Choukri Chacrone  Naïma Hamoumi 《Comptes Rendus Geoscience》2005,337(12):1026-1034

The sedimentological study of Arenig–Llanvirn successions of Aït Lahsen (western High Atlas), Tizi-n-Tichka and Imini (central High Atlas) allow us to recognise two independent epeiric seas. In the western High Atlas, the sedimentation occurred in a wave- and storm-influenced delta, alimented by a source situated at the present-day location of the Argana corridor, under the control of sea-level fluctuations and subsidence. In the central High Atlas, the sedimentation occurred in an influenced tide and episodic storm delta, alimented by sources situated at the present-day location of the Siroua and Ouzellagh Massifs under the control of sea-level fluctuations and tectonics. To cite this article: C. Chacrone, N. Hamoumi, C. R. Geoscience 337 (2005).  相似文献   

北京清代“晴雨录”降水记录的再研究——应用多因子回归方法重建北京(1724～1904年)降水量序列   总被引：18，自引：3，他引：15       下载免费PDF全文

张德二  刘月巍 《第四纪研究》2002,22(3):199-208

本文对早期发表的《北京250年降水》资料进行复算,并讨论其复原方法。在此基础上进一步探讨清代“晴雨录”降水资料复原方法的改进问题。试作了两种多因子回归复原方案,经对比这些方案及其试算结果,认为以8因子的逐步回归方案效果最佳。将此结果与《北京250年降水》1)及同期的器测降水量记录等进行比较,给出新的北京1724～2000年降水量复原序列。  相似文献   

鄂尔多斯盆地胡尖山-耿湾地区延长组长4+5油层组沉积特征及有利相带预测     

肖玲  田景春  李君文  夏青松  王峰 《新疆地质》2007,25(3):291-294

以岩心观察为依据,结合储集层岩性、沉积构造和粒度分析等方法对鄂尔多斯盆地胡尖山—耿湾地区长4 5油层组进行沉积相分析.研究结果表明:研究区长4 5油层组为三角洲前缘沉积,水下分流河道、河口坝、分流间湾、远砂坝及前缘席状砂构成其主要沉积微相.长4 52期水下分流河道砂体之间交叉叠合连片,但水下分流河道、叠置水下分流河道分割性较强,随着湖盆短暂的扩张,长4 51期水下分流河道缩小,分流间湾进一步扩大.在沉积相研究的基础上对长4 52期进行有利相带预测,共预测出5个有利储集相带发育区,为该地区进一步勘探提供依据.  相似文献   

准噶尔盆地中S区西山窑组沉积微相与油气勘探   总被引：1，自引：0，他引：1  

罗洋  李德敏  蒋庆平  崔建伟  彭嘉 《新疆地质》2007,25(4):409-412

准噶尔盆地中部S区块是老油盆的新区块,其重点勘探层位西山窑组,已有工业性油气产出.综合分析了沉积微相与油气勘探的关系,采用"点-线-面"的立体空间研究思路,作出了三维的微相划分和相关的4种有利储层类型划分.中S区西山窑组沉积特征是,整体处于水退的环境中,兼有短期的水进,其中Y1井区主要经历了浅湖-湖沼-辫状河三角洲前缘-滨湖相,最有利微相是2砂组的辫状河三角洲前缘水下分流河道.  相似文献   

High-resolution climate variability of southwest China during 57-70 ka reflected in a stalagmite δ18O record from Xinya Cave     

LI TingYong  YUAN DaoXian  LI HongChun  YANG Yan  WANG JianLi  WANG XinYa  LI JunYun  QIN JiaMing  ZHANG MeiLiang  LIN YuShi 《中国科学D辑(英文版)》2007,50(8)

A 26-cm-long stalagmite (XY2) from Xinya Cave in northeastern Chongqing of China has been ICP-MS 230Th/U dated, showing a depositional hiatus at 2.3 cm depth from the top. The growth of the 2.3-26 cm interval determined by four dates was between 57 ka and 70 ka, with a linear growth rate of 0.023 mm/a.We have analyzed 190 samples for δ18O and δ13C, mostly in the 2.3-26 cm part. The δ18O and δ13C values between 57 ka and 70 ka reveal decadal-to-centennial climatic variability during the glacial interval of Marine Isotope Stage 4 (MIS4), exhibiting much higher resolution than that of the published Hulu and Dongge records during this interval. Speleothem δ18O in eastern China, including our study area can be used as a proxy of summer monsoon strength, with lighter values pointing to stronger summer monsoon and higher precipitation, and vice versa. Two decreases in the δ18O signature of XY2 record around 59.5 and 64.5 Ka are argued to correspond to the Dansgaard-Oeschger (D-O) events 17 and 18 respectively. The Heinrich event 6 (H6) can be identified in the record as a heavy δ18O peak around 60 ka, indicating significant weakening of the monsoon in Chongqing during the cold period.The XY2 δ18O record shows very rapid change toward to the interstadial condition of the D-O event, but more gradual change toward to the cold stadial condition. This phenomenon found in the Greenland ice core records is rarely observed so clearly in previously published speleothem records. According to SPECMAP δ18O record, the glacial maximum of MIS 4 was around 64.5 ka with the boundary of MIS 3/4 around 60 ka. Unlike the marine record, the speleothem record of XY2, China, exhibits much high frequency variations without an apparent glacial maximum during MIS 4. However, the timing of MIS 3/4 boundary seems to be around 60 ka when the H6 terminated, in agreement with the marine chronology.The growth period of sample XY2 during glacial times probably reflects a local karstic routing of water,rather than having climatic significance.  相似文献   

Response spectrum of seismic design code for zones lack of near-fault strong earth- quake records   总被引：1，自引：0，他引：1  

李新乐  窦慧娟朱晞 孙建刚 《地震学报(英文版)》2007,20(4):447-453

It was shown from the study on the recently near-fault earthquake ground motions that the near-fault effects were seldom considered in the existing Chinese seismic code. Referring to the UBC97 design concept for near-fault factors, based on the collected world-widely free-site records of near-fault earthquakes ground motions classified by earthquake magnitude and site condition, the attenuation relationship expressions of the acceleration spectrum demand at the key points within the long period and moderate period were established in term of the earthquake magnitude and the site condition. Furthermore, the near-fault factors’ expressions about the earthquake magnitude and the fault distance were deduced for the area lack of near-fault strong earthquake records. Based on the current Chinese Building Seismic Design Code, the near-fault effect factors and the modified design spectral curves, which were valuable for the seismic design, were proposed to analyze the seismic response of structures.  相似文献   

缺乏近断层强震观测资料地区抗震设计规范反应谱研究   总被引：1，自引：0，他引：1       下载免费PDF全文

李新乐  窦慧娟  朱晞  孙建刚 《地震学报》2007,29(4):419-425

根据最近几次的近断层地震观测记录研究显示，在现行结构抗震设计规范中很少考虑近断层效应的影响，对于缺乏近断层强震观测资料地区，抗震设计规范的改进方法及近断层效应的设计参数还没有统一结论. 本文基于UBC97近断层因子设计理念， 在收集世界范围内近断层观测记录的基础上，按场地和震级进行分类，建立了中长周期关键点处的加速度谱需求的衰减关系式，推导给出了缺乏近断层观测资料地区近断层影响因子的震级和断层距的关系式. 并以我国现行的建筑抗震设计规范为基础，建议了近断层影响因子的参考取值和修正后的反应谱曲线，为我国结构抗震设计提供了参考.   相似文献