Tidally dominated, rimmed-shelf facies of the Picún Leufú Formation (Jurassic/Cretaceous boundary) in southwest Gondwana, Neuquén Basin, Argentina     

Claudia Armella  Nora Cabaleri  Hctor A. Leanza 《Cretaceous Research》2007,28(6):961-979

A palaeoenvironmental model for the Picún Leufú Formation (Jurassic/Cretaceous boundary), which crops out in the Neuquén Basin, Argentina, on the southwestern margin of Gondwana, is presented in this paper for the first time. Detailed stratigraphic sections exposed along National Road 40 where it crosses the Picún Leufú Creek (type locality) and in the Cerrito Caracoles area, were examined and sampled. Based on a combination of the sedimentological data obtained (facies/microfacies analysis) and the relationship between benthic macrofaunas and their taphonomic attributes, it is concluded that the formation reflects a tidally dominated, rimmed-shelf setting characterized by prograding bars dissected by channels and thick lagoonal facies with shoal developments. In the Cerrito Caracoles area, where only the basal part of the formation is exposed, it is interpreted to have been deposited in a shallow subtidal marine environment in which shelf margin facies with patch reefs have been recognized.  相似文献   

用储层岩石抽提物的饱和烃色谱指纹识别油气层   总被引：12，自引：0，他引：12  

陈世加  黄第藩 《沉积学报》1998,16(4):149-152

利用储层岩石抽提物的饱和烃色 质总离子图的指纹特征判识储层的流体（油、气）类型。油层或油饱和的储层,饱和烃色 质总离子流图的特征是正构烷烃碳数分布宽,碳数分布在C₁₅～C₃₈之间,与原油样品的正构烷烃碳数分布相似;凝析气层的正构烷烃碳数分布略窄一些,碳数分布在C₁₅～C₃₅之间,低碳数（小于C₂₁）的正构烷烃相对于油层富集,高碳数（大于C₂₁）的正构烷烃丰度明显低于油层;干气层的正构烷烃碳数分布最窄,碳数分布在C₁₅～ C₂₈之间,只有低碳数的正构烷烃,高碳数的正构烷烃丰度极低。据此可用来识别油层、凝析气层和干气层,也可用于一些测井资料不全或测井质量差的老井的油气层复查、测井难以识别的火成岩油气层的识别,还可用于地层评价,为油气酸化层位的优选提供科学依据。  相似文献   

Accelerator mass spectrometry radiocarbon dating of 1994 Lake Winnipeg cores   总被引：1，自引：1，他引：0  

R. E. Vance  A. M. Telka 《Journal of Paleolimnology》1998,19(3):329-334

Conventional radiocarbon dating of Lake Winnipeg core samples has produced erroneously old ages due to the incorporation of pre-Quaternary carbon derived from carbonaceous rocks, soils and sediments in the watershed, as well as a hard-water effect resulting from leaching of calcareous rocks and soils. To circumvent these problems and develop a reliable chronology for the Lake Winnipeg core series, a total of 64 samples from the Lake Winnipeg core series were processed to isolate well preserved macrofossils suitable for Accelerator Mass Spectrometry (AMS) radiocarbon dating. Here we report six radiocarbon ages derived from plant macrofossils and ostracodes, and reconstruct aspects of the depositional environment of each sample based on the associated macrofossil assemblage.  相似文献   

四川南部珙县早侏罗世一新蜥脚类恐龙   总被引：3，自引：0，他引：3  

何信禄  王长生  刘尚忠  周凤云  刘图强  蔡开基  代兵 《四川地质学报》1998,(1)

简介在珙县下侏罗统自流井组东岳庙段中,发现的原始蜥脚类恐龙化石的一新属种石碑珙县龙。成年个体长约１４ｍ。化石材料相当丰富,除头骨不完全外,其他部分乃至全部均保存完好。它是早期的原始的蜥脚类,但又和蜥脚类有不少共同点。它对研究蜥脚类的起源和进化,具有重要意义  相似文献   

Modelling flow resistance in vegetated streams: review and development of new theory     

Julian C. Green 《水文研究》2005,19(6):1245-1259

Aquatic macrophytes are often the dominant factor influencing flow conditions within the channels they occupy. Existing knowledge of how stream plants affect the flow is outlined, and the different scales at which vegetation resistance operates are proposed. Resistance is shown to be a function of the size of the plants, their structural properties, location in the channel, and the local flow conditions. Current models to calculate this composite resistance effect are assessed in the light of theoretical considerations of the nature of vegetation resistance. New theory is also presented, which demonstrates the non‐linear relationship between channel resistance and the proportion of the channel occupied by vegetation. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Connections Between Different Types of El Ni~no and Southern/Northern Oscillation          下载免费PDF全文

PENG Jingbei  ZHANG Qingyun  CHEN Lieting 《Acta Meteorologica Sinica》2011,25(4):506-516

It has long been acknowledged that there are two types of El Ni(n)o events,i.e.,the eastern Pacific El Ni(n)o (EE) and the central Pacific El Ni(n)o (CE),according to the initial position of the anomalous warm water and its propagation direction.In this paper,the oceanic and atmospheric evolutions and the possible mechanisms of the two types of El Ni(n)o events were examined.It is found that all the El Ni(n)o events,CE or EE,could be attributed to the joint impacts of the eastward advection of warm water from the western Pacific warm pool (WPWP) and the local warming in the equatorial eastern Pacific.Before the occurrence of CE events,WPWP had long been in a state of being anomalous warm,so the strength of eastward advection of warm water was much stronger than that of EE,which played a major role in the formation of CE.While for the EE events,most contribution came from the local warming of the equatorial eastern Pacific.It is further identified that the immediate cause leading to the difference of the two types of El Ni(n)o events was the asynchronous variations of the Southern Oscillation (SO) and the Northern Oscillation (NO) as defined by Chen in 1984.When the transition from the positive phase of the NO (NO+) to NO- was prior to that from SO+ to SO-,there would be eastward propagation of westerly anomalies from the tropical western Pacific induced by NO and hence the growth of warm sea surface temperature anomalies in WPWP and its eastward propagation.This was followed by lagged SO-induced weakening of southeast trade winds and local warming in the equatorial eastern Pacific.These were conducive to the occurrence of the CE.On the contrary,the transition from SO+ to SO- leading the transition of NO would favor the occurrence of EE type events.  相似文献   

Processes Leading to Second-Year Cooling of the 2010-12 La Ni(n)a Event,Diagnosed Using GODAS     

FENG Licheng  ZHANG Rong-Hua  WANG Zhanggui  CHEN Xingrong 《大气科学进展》2015,32(3)

  相似文献   

Ion acceleration and Alfvén wave generation at the Earth’s bow shock     

E. G. Berezhko  S. N. Taneev 《Astronomy Letters》2007,33(5):346-353

The processes of ion acceleration and Alfvén wave generation by accelerated particles at the Earth’s bow shock are studied within a quasi-linear approach. Steady-state ion and wave spectra are shown to be established in a time of 0.3–4 h, depending on the background level of Alfvénic turbulence in the solar wind. The Alfvén waves produced by accelerated ions are confined within the frequency range 10^?2–1 Hz and their spectral peak with a wave amplitude βB ～ B comparable to the interplanetary magnetic field strength B corresponds to the frequency v = (2–3) × 10^?2 Hz. The high-frequency part of the wave spectrum (v > 0.2 Hz) undergoes damping by thermal ions. The calculated spectra of the accelerated ions and the Alfvén waves generated by them reproduce the main features observed in experiments.  相似文献   

大气折射指数的结构参数与北方5～9月降雨的强相关现象     

涂钢  支克广  支平  付光极  王建平 《地球科学进展》2010,25(11):1291-1295

基于中荷合作项目"建立关于荒漠化和粮食保障的中国能量与水平衡监测系统"(CEWBMS),在国家卫星气象中心和国家林业总局的支持下,乾安大孔径闪烁仪于1999年10月安装并正式运行.利用2000-2005年5～9月大孔径闪烁仪(LAS)观测的大气折射指数的结构参数Cn2,采用独立性检验,证实了Cn2的高低与未来32h是否出现降雨(晴雨)存在显著相关关系.结合乾安气象站的有关气象观测数据,初步选择Cn2白天值以及夜间值以Cn2的24 h变量作为预报依据,建立基于Cn2预报未来32h晴雨的预报流程;并利用2006年Cn2的观测数据,依照预报流程对2006年进行了回报预报试验,正确率为42/47.  相似文献   

西风爆发事件对暖池厄尔尼诺和冷舌厄尔尼诺的作用——一个概念模型得到的结果     

连涛  何海伦 《海洋学研究》2014,32(3)

本文通过1个概念模型讨论了西风爆发事件对暖池厄尔尼诺与冷舌厄尔尼诺两种事件的作用,并讨论了它们对应的物理机制。结果表明,由西风爆发所诱导的纬向平流异常和海洋波动对厄尔尼诺的多样性有着至关重要的作用。由于模型包含了最基本的海-洋与大气物理变量及其相互作用机制,本结果可为解释西风爆发事件对厄尔尼诺多样性影响研究提供最基本的框架。  相似文献