Annealing behavior of alpha recoil tracks in phlogopite   总被引：1，自引：0，他引：1  

Wanming Yuan  Richard A. Ketcham  Shaokai Gao  Jinquan Dong  Zenkuan Bao  Jun Deng 《Chemical Geology》2009,266(3-4):343-349

In this study we present and interpret a new experimental data set documenting thermal annealing of alpha recoil tracks (ARTs) in phlogopite. Through improvements in experimental technique, difficulties in obtaining useable data from material with an uneven distribution of U and Th were overcome. The resulting annealing pattern was well organized on an Arrhenius plot, allowing construction of a simple, 3-parameter annealing model of parallel contours of constant annealing with a linear progression. Our data and model indicate that phlogopite ARTs anneal at very low temperatures on geological time scales. At the million-year time scale, full annealing requires a temperature of only 33 °C, and we infer closure temperatures from 26–37 °C for cooling rates of 10–100 °C/m.y. Phlogopite ART analysis is thus likely to be primarily useful in relatively young (<1 Ma) terrains featuring either recent volcanism or recent, fast exhumation. In such situations, however, it may provide unique information on the timing of the final stages of unroofing. Comparison of our results with previous studies on ART and fission-track annealing in phlogopite and biotite indicates that these two types of radiation damage anneal at disparate time and temperature conditions in biotite-series micas.  相似文献   

四川美姑发现侏罗纪恐龙足迹化石     

鄢圣武  巴金  邢立达  金灿海  毛胜军 《地质通报》2017,36(6):925-927

2016年8月,在位于西昌盆地边缘的四川美姑县中侏罗统沙溪庙组底部薄层粉砂岩之上,发现有恐龙足迹化石。恐龙足迹共3个,均与跷脚龙足迹相似。该发现对于古气候、古地理和地层对比都具有重要的意义,足迹详细分类有待进一步研究。  相似文献   

Cyclone life cycle characteristics over the Northern Hemisphere in coupled GCMs   总被引：4，自引：1，他引：3  

Ulrike Löptien  Olga Zolina  Sergey Gulev  Mojib Latif  Vladimir Soloviov 《Climate Dynamics》2008,31(5):507-532

Cyclone activity and life cycle are analysed in the coupled GCMs ECHAM5/OM and ECHAM4/OPYC3. First, the results for the present climate (1978–1999) are compared with ERA-40 and NCEP/NCAR reanalyses, showing a drastic improvement in the representation of cyclone activity in ECHAM5/OM compared to ECHAM4/OPYC3. The total number of cyclones, cyclone intensity, propagation velocity and deepening rates are found to be much more realistic in ECHAM5/OM relative to ECHAM4/OPYC3. Then, changes in extra tropical cyclone characteristics are compared between present day climate and future climate under the emission-scenario A1B using ECHAM5/OM. This comparison is performed using the 20-year time slices 1978–1999, 2070–2090 and 2170–2190, which were considered to be representative for the various climate conditions. The total number of cyclones does not undergo significant changes in a warmer climate. However, regional changes in cyclone numbers and frequencies are evident. One example is the Mediterranean region where the number of cyclones in summer increases almost by factor 2. Some noticeable changes are also found in cyclone life cycle characteristics (deepening rate and propagation velocity). Cyclones in the future climate scenario tend to move slower and their deepening rate becomes stronger, while cyclone intensity does not undergo significant change in a warmer climate. Generally, our results do not support the hypothesis of enhanced storminess under future climate conditions.  相似文献   

随机分布的小尺度涡旋场对台风路径影响的研究   总被引：2，自引：1，他引：1  

罗哲贤  邹立尧 《气象学报》2010,68(1):32-38

文中用正压原始方程模式和理想初始场研究了随机分布的小尺度涡度场对台风路径的作用.在模式初始场上,有一个理想的副热带高压脊、一个台风和一个随机生成的小尺度涡度场.设计实施两组试验,记为试验A和试验B,积分时间为56 h.每个试验的初始场上各有100个随机分布的小尺度涡.除了小尺度涡的空间位置不同以外,两组试验其余的试验条件全部相同.模式积分的结果指出:小尺度涡不同的空间分布可以引起台风外围水平风速的差异,进而改变台风环境引导流的强度.在24、36和48小时,试验A沿东西方向环境引导流分别为7.8、8.2和8.7 m/s,24-48小时平均值为8.2 m/s,沿南北方向环境引导流分别为0.9、1.8和2.5 m/s,24-48小时平均值为2.1 m/s;试验B沿东西方向分别为8.3、9.5和9.7 m/s,24-48小时平均值为9.5 m/s,沿南北方向分别为2.3、2.3和5.9 m/s,24-48小时平均值为3.4 m/s.环境引导气流强度的小同导致未来台风中心位置的不同.两组不同的初始随机涡度场可以引起48 h以后台风中心相距约120 km.副热带高压与台风相互作用的动力学表明:当初始台风位于副热带高压脊与赤道之间时,局域的绝对涡度梯度与台风传播的关系足南若干个不规则的散布点表征的.引进随机涡度场以后,副热带高压脊、台风和小尺度涡旋三者的共同作用使得绝对涡度梯度与台风传播之间的关系复杂化,除了会出现不规则散布点的特征外,还可显示出两者之间的高相关特征.  相似文献   

Thermochronological data from Sudan in the frame of the denudational history of the Nubian Red Sea margin     

M. L. Balestrieri  E. Abbate  G. Bigazzi  Omer El Bedri Ali 《地球表面变化过程与地形》2009,34(9):1279-1290

Low‐temperature thermochronology provides information on the timing of rifting and denudation of passive margins, and the Red Sea with its well‐exposed, young rift margins is a suitable setting for its application. Here we present new apatite fission‐track (AFT) data from Sudan northern hinterland and Red Sea coastal areas. From the former region we obtained ages between 270 ± 2 Ma ad 253 ± 53 Ma, and from the coastal belt between 83 ± 8 Ma and 39 ± 7 Ma. These data prompted a review and comparison with low‐temperature thermochronological data from the whole Nubian Red Sea Margin, and a discussion on their implication in assessing the margin evolutionary style. AFT data are available for Egypt and Eritrea as well as apatite (U‐Th)/He (AHe) ages for two transects transversal to the margin in Eritrea. Both in Egypt and Eritrea AFT data record a cooling event at about 20–25 Ma (Early Miocene) and an earlier, more local, cooling event in Egypt at about 34 Ma (Early Oligocene). The thermal modeling of the Sudan samples provides an indication of a rapid cooling in Miocene times, but does not support nor rules out an Early Oligocene cooling phase. The re‐assessment of new and existing thermochronological data within the known geological framework of the Nubian and conjugate Arabian margins favours the hypothesis that early rifting stages were affecting the whole Gulf of Suez–Red Sea–Gulf of Aden system since the Oligocene. These precocious, more attenuated, phases were followed by major extension in Miocene times. As to the mode of margin evolution, AFT age patterns both in Egypt and Eritrea are incompatible with a downwarp model. The distribution of AHe ages across the Eritrean coastal plain suggests that there the escarpment was evolving predominantly by plateau degradation. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

重庆綦江地质公园地质遗迹特征及其地质意义   总被引：1，自引：0，他引：1  

刘严松  何政伟  龙晓君  李晓琴  李能炯  龚黎明 《中国地质灾害与防治学报》2010,21(2):118-124

綦江地质公园发育木化石、恐龙足迹、恐龙骨骼化石、鱼化石、沉积构造、丹霞地貌等地质遗迹景观,木化石和恐龙足迹为园区的导向型景观。木化石分布在侏罗系中统沙溪庙组(J2s)上部砂岩层中,砂岩层含钙质结核,在约300×200m2的砂岩层内共埋藏有60多根木化石,其中一半木化石为钙化作用形成。恐龙足迹集中分布在白垩系上统夹关组(K2j)砂泥岩层中,岩层发育交错层理、波痕和泥裂。在夹关组的3个层位中共发现329个恐龙足迹,其分别属于甲龙类、鸟脚类和兽脚类。园区地质遗迹分布在一套河湖相沉积层中,其形成于内陆河湖网形成之时(如木化石),并随着四川盆地周围的湖泊系统解体而发展(如恐龙足迹),最终随着河流由堆积作用为主的阶段转变为以侵蚀作用为主的阶段而减弱(如丹霞地貌)。白垩纪上统夹关组的恐龙足迹群形成于干热的环境,多类型的恐龙足迹集中分布反映了白垩纪晚期(夹关期)恐龙种群的丰富,恐龙足迹的发现为区域内寻找白垩系地层的恐龙骨骼化石提供了依据。  相似文献   

山东诸城盆地下白垩统莱阳群的非鸟恐龙与鸟足迹化石组合   总被引：2，自引：1，他引：1  

邢立达  杰瑞德D.哈里斯  王克柏  李日辉 《地质通报》2010,29(8):1105-1112

中国山东省诸城盆地张祝河湾村下白垩统杨家庄组发现了非鸟恐龙(蜥脚类和鸟脚类)与古鸟类足迹。该足迹点的非鸟恐龙足迹深受水浸沉积物的影响,发生了强烈变形。蜥脚类足迹的前后足迹面积相近,造迹者行进缓慢。鸟脚类足迹属于禽龙-鸭嘴龙类型的足迹。古鸟类足迹并不类似于中国以往发现的中生代鸟类足迹,而类似于韩国滨水鸟类足迹的金东鸟足迹(Jindongornipes)。讨论了莱阳足迹(Laiyangpus)和拟跷脚龙足迹(Paragrallator,亦译为拟似鹬龙足迹),前者因模式标本遗失而不明确,后者可归入安琪龙足迹未定种(Anchisauripus isp)。这批足迹的发现大大增加了山东省东部恐龙的多样性。  相似文献   

Distinction between the Youngest Toba Tuff and Oldest Toba Tuff from northern Sumatra based on the area density of spontaneous fission tracks in their glass shards     

John A. Westgate  Nicholas J.G. Pearce  Emma Gatti  Hema Achyuthan 《Quaternary Research》2014

Determination of the area density of spontaneous fission tracks (ρ_s) in glass shards of Toba tephra is a reliable way to distinguish between the Youngest Toba Tuff (YTT) and the Oldest Toba Tuff (OTT). The ρ_s values for YTT, uncorrected for partial track fading, range from 70 to 181 tracks/cm² with a weighted mean of 108 ± 5 tracks/cm², based on 15 samples. Corrected ρ_s values for YTT are in the range of 77–140 tracks/cm² with a weighted mean of 113 ± 8 tracks/cm², within the range of uncorrected ρ_s values. No significant difference in ρ_s exists between YTT samples collected from marine and continental depositional settings. The uncorrected ρ_s for OTT is 1567 ± 114 tracks/cm² so that confusion with YTT is unlikely.  相似文献   

超强台风“梅花”(1109号)的转向原因与预报分析   总被引：1，自引：0，他引：1  

曹晓岗  王慧  刘晓波 《湖北气象》2013,(2):151-157

使用高空探测资料、FY-2C卫星云图、CIMSS气象卫星云图分析资料、历年台风路径、NCEP再分析资料,以及欧洲气象中心全球模式(EC)、日本气象厅全球模式(JMA)、国家气象中心全球模式(T639)、上海台风模式(SHTM)等预报资料,基于对2011年第9号台风"梅花"路径以及台风相似路径的预报等,分析影响台风"梅花"移动路径的环境系统演变,从中找出影响台风"梅花"移动转向的关键系统,分析和检验各数值模式对台风路径预报的结果;同时,研究台风路径相似预报方法。结果表明,位于日本的副热带高压南伸并与"梅花"东南侧的弱反气旋打通,引导气流中偏南风分量逐渐加大是"梅花"路径转向以致不在我国登陆的关键点;对数值模式预报的路径,应根据实况天气形势演变订正其预报误差;根据前期路径选多个关键区找台风相似路径更具参考性。  相似文献   

基于EPS2008航迹图制作     

姚明经  陈冲  史冬庆  王紫阳 《北京测绘》2014,(1):119-121,124

通航流量试验研究领导小组在三峡—葛洲坝两坝间组织开展大流量实船试航,我队承担本次任务航迹测量工作。本文提出了航迹数据自动处理流程,基于VB6.0开发航迹处理软件,并基于EPS2008,制作航迹符号。最后,通过实验数据,验证了数据处理的准确性和成图的快速性。  相似文献