Palaeomagnetism and Ar-40/Ar-39 age of a Pliocene lava flow sequence in the Lesser Caucasus: record of a clockwise rotation and analysis of palaeosecular variation
文献类型：期刊论文
| 作者 | Caccavari, Ana1; Calvo-Rathert, Manuel2; Goguitchaichvili, Avto1; He Huaiyu3; Vashakidze, Goga4; Vegas, Nestor5 |
| 刊名 | GEOPHYSICAL JOURNAL INTERNATIONAL
 |
| 出版日期 | 2014-06-01 |
| 卷号 | 197期号:3页码:1354-1370 |
| 关键词 | Palaeomagnetic secular variation Palaeomagnetism applied to tectonics Rock and mineral magnetism |
| ISSN号 | 0956-540X |
| DOI | 10.1093/gji/ggu097 |
| 文献子类 | Article |
| 英文摘要 | A palaeomagnetic and rock-magnetic investigation has been carried out on a Pliocene lava flow sequence in the Djavakheti Highland in the central Lesser Caucasus in the Republic of Georgia. In addition, a Ar-40/Ar-39 dating and electronic microscopic studies were performed on samples of this sequence, named the Saro section, which consists of 39 successive lava flows of doleritic basalts. A characteristic magnetization could be isolated in all studied 39 flows, yielding reverse-polarity directions in all cases, a mean direction D = 202.2A degrees, I = -60.6A degrees (N = 39, alpha(95) = 2.0A degrees, k = 138) being obtained. Thermomagnetic experiments (strong-field versus temperature curves) suggested low-Ti titanomagnetites and low Curie-temperature titanomagnetites with a rather high titanium content (x a parts per thousand 0.5-0.7) as the main carriers of remanence. Their domain structure is characterized by a mixture of single- and multidomain grains. Ar-40/Ar-39 dating yielded an age of 1.73 +/- 0.03 Ma, interpreted as the eruption age of the uppermost lava flow of the sequence. Analysis of palaeomagnetic results and radiometric data from the present and a previous study allows two different explanations about the time of emplacement of the section: (i) The lower 36 flows of the sequence might have been emitted between the normal-polarity Reunion and Olduvai chrons, and the upper three flows after the Olduvai chron, with a long hiatus in volcanic activity of more than 150 kyr or (ii) The whole sequence has been emitted between 1.778 and 1.73 +/- 0.03 Ma, after the Olduvai chron. Comparison of the palaeomagnetic results obtained in this study with the expected direction shows that while inclination values agree well, declination shows an eastward deviation of 19.2A degrees +/- 5.8A degrees. This discrepancy can be explained with a clockwise vertical-axis rotation of the sequence, which might have been produced by extensional structures with strike-slip component, which can be found in the study area. Virtual geomagnetic pole (VGP) scatter recorded in the sequence is somewhat lower than expected. To analyse this behaviour, VGP scatter of the sequence was first calculated with respect to the palaeomagnetic pole obtained from the Fisher mean of all VGPs. Then it was calculated with respect to the appropriate Eurasian palaeomagnetic pole from VGPs obtained after applying a 19.2A degrees counter-clockwise rotation of the sequence (i.e. undoing the observed vertical axis rotation). The observed scatter with both independent methods appeared to be very similar, allowing the deduction that secular variation is reasonably well averaged out from the mean of the Saro sequence and therefore it has experienced the observed clockwise rotation. As no differential vertical-axis rotation can be detected between the upper and lower parts of the section, the whole sequence must have experienced the 19.2A degrees +/- 5.8A degrees clockwise rotation between 1.73 +/- A 0.03 Ma and present. |
| WOS关键词 | GEOMAGNETIC POLARITY TRANSITION ; SOUTHERN GEORGIA ; MAGNETIC-PROPERTIES ; SECULAR VARIATION ; FIELD ; REVERSAL ; PALEOINTENSITY ; GEOCHRONOLOGY ; VOLCANISM ; HIGHLAND |
| WOS研究方向 | Geochemistry & Geophysics |
| 语种 | 英语 |
| WOS记录号 | WOS:000337041100006 |
| 出版者 | OXFORD UNIV PRESS |
| 资助机构 | Ministerio de Economia y Competitividad, Spain(CGL2012-32149) ; Ministerio de Economia y Competitividad, Spain(CGL2012-32149) ; Ministerio de Ciencia e Innovacion(CGL2011-23755 ; Ministerio de Ciencia e Innovacion(CGL2011-23755 ; CONACYT (Mexico)(257639) ; CONACYT (Mexico)(257639) ; CGL2010-14869) ; CGL2010-14869) ; Ministerio de Economia y Competitividad, Spain(CGL2012-32149) ; Ministerio de Economia y Competitividad, Spain(CGL2012-32149) ; Ministerio de Ciencia e Innovacion(CGL2011-23755 ; Ministerio de Ciencia e Innovacion(CGL2011-23755 ; CONACYT (Mexico)(257639) ; CONACYT (Mexico)(257639) ; CGL2010-14869) ; CGL2010-14869) ; Ministerio de Economia y Competitividad, Spain(CGL2012-32149) ; Ministerio de Economia y Competitividad, Spain(CGL2012-32149) ; Ministerio de Ciencia e Innovacion(CGL2011-23755 ; Ministerio de Ciencia e Innovacion(CGL2011-23755 ; CONACYT (Mexico)(257639) ; CONACYT (Mexico)(257639) ; CGL2010-14869) ; CGL2010-14869) ; Ministerio de Economia y Competitividad, Spain(CGL2012-32149) ; Ministerio de Economia y Competitividad, Spain(CGL2012-32149) ; Ministerio de Ciencia e Innovacion(CGL2011-23755 ; Ministerio de Ciencia e Innovacion(CGL2011-23755 ; CONACYT (Mexico)(257639) ; CONACYT (Mexico)(257639) ; CGL2010-14869) ; CGL2010-14869) |
| 源URL | [http://ir.iggcas.ac.cn/handle/132A11/86078]  |
| 专题 | 中国科学院地质与地球物理研究所 |
| 通讯作者 | Caccavari, Ana |
| 作者单位 | 1.Sede Michoacan UNAM, Lab Interinst Magnetismo Nat, Inst Geofis, Morelia 58990, Michoacan, Mexico 2.Univ Burgos, Dept Fis, EPS, E-09006 Burgos, Spain 3.Chinese Acad Sci, Inst Geol & Geophys, Beijing 100029, Peoples R China 4.I Javakhishvili Tbilisi State Univ, Alexandre Janelidze Inst Geol, Tbilisi, Rep of Georgia 5.Univ Basque Country, Dept Geodinam, E-48940 Leioa, Bizkaia, Spain |
| 推荐引用方式 GB/T 7714 | Caccavari, Ana,Calvo-Rathert, Manuel,Goguitchaichvili, Avto,et al. Palaeomagnetism and Ar-40/Ar-39 age of a Pliocene lava flow sequence in the Lesser Caucasus: record of a clockwise rotation and analysis of palaeosecular variation[J]. GEOPHYSICAL JOURNAL INTERNATIONAL,2014,197(3):1354-1370. |
| APA | Caccavari, Ana,Calvo-Rathert, Manuel,Goguitchaichvili, Avto,He Huaiyu,Vashakidze, Goga,&Vegas, Nestor.(2014).Palaeomagnetism and Ar-40/Ar-39 age of a Pliocene lava flow sequence in the Lesser Caucasus: record of a clockwise rotation and analysis of palaeosecular variation.GEOPHYSICAL JOURNAL INTERNATIONAL,197(3),1354-1370. |
| MLA | Caccavari, Ana,et al."Palaeomagnetism and Ar-40/Ar-39 age of a Pliocene lava flow sequence in the Lesser Caucasus: record of a clockwise rotation and analysis of palaeosecular variation".GEOPHYSICAL JOURNAL INTERNATIONAL 197.3(2014):1354-1370. |
入库方式： OAI收割
来源：地质与地球物理研究所
浏览0
下载0
收藏0
其他版本
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。