Paleomagnetic and paleointensity study of an Oligocene-Miocene lava sequence from the Hannuoba Basalts in northern China

doi:10.1016/j.pepi.2004.12.004

	Paleomagnetic and paleointensity study of an Oligocene-Miocene lava sequence from the Hannuoba Basalts in northern China
	Pan, YX ; Hill, MJ ; Zhu, RX
刊名	PHYSICS OF THE EARTH AND PLANETARY INTERIORS
	2005-07-15
卷号	151 期号:1-2 页码:21-35
关键词	Absolute Paleointensity Paleomagnetic Direction K-ar Dating Oligocene-miocene Hannuoba Basalts North China Block
ISSN号	0031-9201
DOI	10.1016/j.pepi.2004.12.004
文献子类	Article
英文摘要	A combined geochronologic, paleomagnetic and paleointensity investigation has been performed on a lava sequence from the Hannuoba Basalts in northern China. Potassium-argon (K-Ar) dating indicates that the lava sequence is of late Oligocene to middle Miocene age (similar to 24-15 Ma). Rock magnetic measurements of thermomagnetic curves, hysteresis properties, saturation isothermal remanent magnetization (SIRM) and back-field demagnetization on representative samples from each lava flow in conjunction with reflected light microscopy observations show the primary carriers of remanence to be fine-grained pseudo-single domain titanomagnetite with various titanium contents. Stepwise thermal and alternating field demagnetization successfully isolated stable characteristic remanent magnetization from 40 out of the 43 lava flows, which record 24 paleomagnetically independent directions. Data (excluding directions regarded as abnormal/transitional) yield a mean direction of DII= 6.8 degrees/56.3 degrees, with alpha(95) = 5.2 degrees and kappa = 51.6, corresponding to a paleomagnetic pole at 232.3 degrees E, 83.7 degrees N with dp = 5.4 degrees and dm = 7.5 degrees, consistent with previously published paleomagnetic poles for the North China Block. The modified Thellier method with systematic partial thermoremanent magnetization (pTRM) checks and pTRM-tail checks was conducted on 72 selected samples. Reliable paleointensity estimates from four lava flows yield a mean virtual dipole moment of (5.6 +/- 1.6) x 10(22) A m(2), suggesting moderately low intensity of the geomagnetic field. This is in good accord with reliable paleointensity datasets for the late Oligocene to middle Miocene (30-15 Ma), but lower than the average for middle Miocene to Pliocene age (15-2 Ma). It thus appears that at some point in the mid-Miocene there was a transition where the field intensity changes between these two states. although many more data are needed to confirm this. (c) 2005 Elsevier B.V. All rights reserved.
WOS关键词	GEOMAGNETIC-FIELD STRENGTH ; EARTHS MAGNETIC-FIELD ; CRETACEOUS NORMAL SUPERCHRON ; LONG-TERM VARIATIONS ; ABSOLUTE PALEOINTENSITY ; PALEOSECULAR VARIATION ; INNER-MONGOLIA ; POLAR WANDER ; SOUTH CHINA ; INTENSITY
WOS研究方向	Geochemistry & Geophysics
语种	英语
出版者	ELSEVIER SCIENCE BV
WOS记录号	WOS:000229670200002
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/65713]
专题	中国科学院地质与地球物理研究所
通讯作者	Pan, YX
作者单位	1.Chinese Acad Sci, Inst Geol & Geophys, Paleomagnetism Lab SKL LTE, Beijing, Peoples R China 2.Univ Liverpool, Dept Earth & Ocean Sci, Geomagnetism Lab, Liverpool L69 7ZE, Merseyside, England
推荐引用方式 GB/T 7714	Pan, YX,Hill, MJ,Zhu, RX. Paleomagnetic and paleointensity study of an Oligocene-Miocene lava sequence from the Hannuoba Basalts in northern China[J]. PHYSICS OF THE EARTH AND PLANETARY INTERIORS,2005,151(1-2):21-35.
APA	Pan, YX,Hill, MJ,&Zhu, RX.(2005).Paleomagnetic and paleointensity study of an Oligocene-Miocene lava sequence from the Hannuoba Basalts in northern China.PHYSICS OF THE EARTH AND PLANETARY INTERIORS,151(1-2),21-35.
MLA	Pan, YX,et al."Paleomagnetic and paleointensity study of an Oligocene-Miocene lava sequence from the Hannuoba Basalts in northern China".PHYSICS OF THE EARTH AND PLANETARY INTERIORS 151.1-2(2005):21-35.