oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
塔里木盆地巴楚—麦盖提地区前寒武系不整合对基底古隆起及其演化的启示
Implications of Precambrian Unconformity to Basement Paleo-uplift and Its Tectonic Evolution of Bachu-Markit Area, Tarim Basin
 [PDF]

陈刚,汤良杰,余腾孝,郭颖,岳勇,李九梅,张旭光,龙禹,谢欣彤,
CHEN Gang
,TANG Liang-jie,YU Teng-xiao,GUO Ying,YUE Yong, LI Jiu-mei,ZHANG Xu-guang,LONG Yu, XIE Xin-tong

- , 2015,
Abstract: 摘要: 通过巴楚—麦盖提地区(巴麦地区)钻井和地震资料的详细分析,结合前寒武纪区域构造、沉积演化,将前寒武系顶面不整合划分为角度不整合、非整合、超覆不整合和平行不整合,这4类不整合分别揭示了裂谷、基底隆起、隆起斜坡和沉积坳陷等。进一步分析了不整合在平面上的分布特征,表明具有从非整合、超覆不整合向整合逐级过渡的分布规律。认为基底古隆起北缘以吐木休克断裂一带为界,南缘可能以铁克里克地区为界,其中基底古隆起的主体位于麦盖提地区和巴楚地区南缘,基底隆起的构造斜坡位于现今塔里木西南坳陷区、巴楚地区北部。基底古隆起演化上可分为前寒武纪平缓古陆阶段、前寒武纪末隆升加强阶段和早—中寒武世沉降埋藏阶段。总体上古隆起在前寒武纪具有南缓北陡特征,早—中寒武世具有南陡北缓特征,分别控制了南华纪—震旦纪和早—中寒武世地层发育和分布。
Abstract: An unconformity analysis method is provided to study the basement paleo-uplift of Bachu-Markit area, Tarim basin. On the basis of regional tectonic and sedimentary evolution of previous research, we divided the Precambrian top surface to angle unconformity, nonconformity, overlap unconformity and parallel unconformity through the recognition of well data and seismic data. The four types of unconformity reflect rift, basement paleo-uplift, slope and depression, respectively. Furthermore, the distribution of unconformity has a gradual transition pattern, which is arrangement from nonconformity, overlap unconformity to conformity. We consider that the north boundary of basement paleo-uplift is Tumuxiuke fault zone and that the south boundary is possibly Tiekelike zone. Therefore, it could be affirmed that the main part of paleo-uplift is located in Markit area and the southern Bachu area; that the slope of paleo-uplift is distributed in present southwestern Tarim depression and the northern Bachu area. The tectonic evolution of basement paleo-uplift can be divided into 3 stages, which are gentle Precambrian archicontinent stage, final Precambrian uplifting stage and Early-Middle Cambrian subsidence stage. As a whole, the paleo-uplift is gentle at the south and steep at the north in Precambrian; while it is contrary in Early-Middle Cambrian, which controls the strata development and distribution of Nanhuaian-Sinian and Early-Middle Cambrian
Precambrian organic matter
Chao Li,Ping’an Peng,Guoying Sheng,Jiamo Fu
Chinese Science Bulletin , 2000, DOI: 10.1007/BF02909757
Abstract: The late progress of the research on Precambrian organic matter in biomarkers, isotopes and relative analytical techniques is reviewed. The key problems in the research of Precambrian organic matter, such as indigenous test of soluble organic matter, are also discussed. At the end, the further work upon Precambrian organic matter is suggested.
Precambrian organic matter

LI Chao,PENG Ping&rsquo,an,SHENG Guoying,FU Jiamo,

科学通报(英文版) , 2000,
Abstract: The late progress of the research on Precambrian organic matter in biomarkers, isotopes and relative analytical techniques is reviewed. The key problems in the research of Precambrian organic matter, such as indigenous test of soluble organic matter, are also discussed. At the end, the further work upon Precambrian organic matter is suggested.
The records of the evolution of Precambrian lithospher: the evidences of petrology and geochemistry of basic rocks on Hainan island
海南岛前寒纪岩石圈演化的记录:基性岩类岩石地球化学证据

XU DeRu,LIN Ge,LIANG XinQuan,CHEN GuangHao,TANG HongFengChangsha Institute of Geotectonics,Chinese Academy of Sciences,Changsh,China,
许德如
,林舸

岩石学报 , 2001,
Abstract: The different characteristics of petrology and geochemistry for all kinds of basic rocks with different times record the tectonic setting and the evolutionary history of lithosphere at Precambrian era on Hainan Island. At the Paleo-Mesoproterozoic era, the meta-basic-ultrabasic rocks on eastern Hainan are oceanic low K arc tholeiite with the features of mafic-basaltic komatiite evidently, originated from highly depleted mantle and are formed under the tectonic setting of volcanic arc. Anyway, at the same time, in western Hainan, a kind of transitional basalt with low depleted mantle origination between MORBs and tholeiites is produced, the magma storeroom is a kind of partial melting mixture made up of mantle wedge located over old-diving depleted belt and crust material being involved into mantle wedge from depleted belt. Their tectonic setting is back-arc or inter-arc spreading basin. In Meso-Neoproterozoic era, the meta-basic-ultrabasic rocks in western Hainan have different petrological and geochemical compositions at the Paleo-Mesoproterozoic era in eastern Hainan, they are different rock types with different time, different origination and different tectonic setting. The meta-basic-ultrabasic rocks in western Hainan are mafic-ultramafic komatiite originated from highly depleted mantle and being formed under the setting of the edge of oceanic ridge. Hereby, we can speculate that the evolution of lithospher during Precambrian has undergone two events of the diving of paleoplate in the Paleo-Mesoproterozoic era and the rift of continent on Meso-Neoproterozoic era at least, following the appearence of ocean basin.
Precambrian glaciations and the evolution of the atmosphere  [cached]
J. H. Carver,I. M. Vardavas
Annales Geophysicae (ANGEO) , 2003,
Abstract: Precambrian glaciations appear to be confined to two periods, one in the early Proterozoic between 2.5 and 2 Gyears BP (Before Present) and the other in the late Proterozoic between 1 and 0.57 Gyear BP. Possible reasons for these broad features of the Precambrian climate have been investigated using a simple model for the mean surface temperature of the Earth that partially compensates for the evolution of the Sun by variations in the atmospheric CO2 content caused by outgassing, the formation of continents and the weathering of the Earth's land surface. It is shown that the model can explain the main changes in the Precambrian climate if the early Proterozoic glaciations were caused by a major episode of continental land building commencing about 3 Gyears BP while the late Proterozoic glaciations resulted from biologicallyenhanced weathering of the land surface due to the proliferation of life forms in the transition from the Proterozoic to the Phanerozoic that began about 1 Gyear BP.
Precambrian Lunar Volcanic Protolife  [PDF]
Jack Green
International Journal of Molecular Sciences , 2009, DOI: 10.3390/ijms10062681
Abstract: Five representative terrestrial analogs of lunar craters are detailed relevant to Precambrian fumarolic activity. Fumarolic fluids contain the ingredients for protolife. Energy sources to derive formaldehyde, amino acids and related compounds could be by flow charging, charge separation and volcanic shock. With no photodecomposition in shadow, most fumarolic fluids at 40 K would persist over geologically long time periods. Relatively abundant tungsten would permit creation of critical enzymes, Fischer-Tropsch reactions could form polycyclic aromatic hydrocarbons and soluble volcanic polyphosphates would enable assembly of nucleic acids. Fumarolic stimuli factors are described. Orbital and lander sensors specific to protolife exploration including combined Raman/laser-induced breakdown spectrocsopy are evaluated.
Pangea B: an artifact of incorrect paleomagnetic assumptions?
P. Rochette,D. Vandamme
Annals of Geophysics , 2001, DOI: 10.4401/ag-3582
Abstract: The detailed plate reconstruction within Pangea megacontinent has been an ongoing debate among the paleomagnetic community for decades. The Pangea B hypothesis, implying a 3500 km Triassic dextral megashear on the Gondwana-Laurussia limit, has been recently reinforced by new data, excluding Southern Alps sites. This configuration, at odds with geological evidence, does improve the coherency of paleomagnetic poles from Gondwana and Laurussia. However, the corresponding apparent latitudinal difference between the two supercontinents can be easily accounted for, without invoking this megashear, considering the effect of inclination error (or equivalent non-dipole field) on the site distribution used in the paleomagnetic study. Once northern hemisphere Southern Alps data are considered, Pangea B no longer holds. Large inclination errors (10°-30°) are to be expected in the Permo-Triassic continental sediments as demonstrated in the Esterel and possibly Argentina Permo-Triassic studies or in Neogene analogues such as the Siwalik or Catalan basin sequences. An overall discussion of the inclination error problem is given. Analysis of the database also suggests an age bias between the Gondwana and Laurussia reference poles at the Permo-Triassic boundary, partly responsible also for the latitudinal shift. Finally, Moroccan data are demonstrated to be irrelevant for computing a Gondwana early Triassic pole.
Neogene and Quaternary geodynamic evolution of the Italian peninsula: the contribution of paleomagnetic data
Antonio Meloni,Laura Alfonsi,Fabio Florindo,Leonardo Sagnotti
Annals of Geophysics , 1997, DOI: 10.4401/ag-4599
Abstract: Paleomagnetism has played an important role in the development of geodynamic models for the Italian peninsula. Paleomagnetic data from this area have been increasingly reported since the late 1960s, placing important constraints on geodynamics. A brief outline of the main concepts underlying a paleomagnetic study is provided in the first part of this paper. We also discuss the criteiia for the assessment of the reliability of paleomagnetic data. Finally,the data collected over the past 25 years in peninsular and insular Italy are synthetically reviewed, discussing the main implications for the geodynamic evolution of the Tyrrhenian - Apennines foreland system.
Short note: On the earliest human occupation in Europe: Paleomagnetic constraints  [PDF]
Josep M. Parés,Avto Goguitchaichvili
Geofísica internacional , 2001,
Abstract: We carried out a detailed paleomagnetic survey at the Dmanissi archeological site (Republic of Georgia, Caucasus) in order to clarify the relative position of the site in the Plio-Pleistocene chronologic framework. In total, 27 standard paleomagnetic cores were obtained across the profile at the locality where the human mandible was found. Fifteen characteristic remanent magnetization directions have been used to determine the magnetic polarity of the studied units. The presence of a strong normal overprint is evident in most of the samples and is usually removed at about 250 degrees Celsius. Judging from the paleomagnetic analysis, it seems that the sediments containing the hominid and stone tools all show reverse polarity magnetization. This points to Matuyama age (post-Olduvai) for the site, in disagreement with previous studies.
Wavelet analysis on paleomagnetic (and computer simulated) VGP time series  [cached]
S. Lorito,G. Giberti,A. Siniscalchi,M. Iorio
Annals of Geophysics , 2003, DOI: 10.4401/ag-3429
Abstract: We present Continuous Wavelet Transform (CWT) data analysis of Virtual Geomagnetic Pole (VGP) latitude time series. The analyzed time series are sedimentary paleomagnetic and geodynamo simulated data. Two mother wavelets (the Morlet function and the first derivative of a Gaussian function) are used in order to detect features related to the spectral content as well as polarity excursions and reversals. By means of the Morlet wavelet, we estimate both the global spectrum and the time evolution of the spectral content of the paleomagnetic data series. Some peaks corresponding to the orbital components are revealed by the spectra and the local analysis helped disclose their statistical significance. Even if this feature could be an indication of orbital influence on geodynamo, other interpretations are possible. In particular, we note a correspondence of local spectral peaks with the appearance of the excursions in the series. The comparison among the paleomagnetic and simulated spectra shows a similarity in the high frequency region indicating that their degree of regularity is analogous. By means of Gaussian first derivative wavelet, reversals and excursions of polarity were sought. The analysis was performed first on the simulated data, to have a guide in understanding the features present in the more complex paleomagnetic data. Various excursions and reversals have been identified, despite of the prevalent normality of the series and its inherent noise. The found relative chronology of the paleomagnetic data reversals was compared with a coeval global polarity time scale (Channel et al., 1995). The relative lengths of polarity stability intervals are found similar, but a general shift appears between the two scales, that could be due to the datation uncertainties of the Hauterivian/Barremian boundary.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.