| 江西信江盆地上白垩统风成红层的古地磁研究 |
| |
| 引用本文： | 罗希,李永祥,李祥辉.江西信江盆地上白垩统风成红层的古地磁研究[J].高校地质学报,2019,25(5):779. |
| |
| 作者姓名： | 罗希 李永祥 李祥辉 |
| |
| 摘 要： | 红层是古地磁学的重要研究对象之一。以往对河湖相红层的古地磁研究较多，而对于风成红层的研究较少。因
此，对于风成红层剩磁记录是否可靠等基本问题仍然缺乏清晰的认识。文章对江西信江盆地上白垩统圭峰群塘边组风成
红层和河口组河流相红层开展了古地磁研究，并通过对比风成红层与河流相红层的古地磁结果，探究风成红层剩磁记录
的可靠性及不同沉积过程对古地磁记录的影响。逐步热退磁实验结果显示仅有19% 的塘边组风成红层分离出稳定的特征
剩磁，而且其强度衰减曲线为凸形，表明特征剩磁为碎屑赤铁矿携带的原生剩磁。其平均方向为Ds=15.6 °, Is=28.9 °, n=
25, κ=13.0, α95=8.3 °；对应的古地磁极为Latitude=70.7 °, Longitude=245.6 °, A95=6.8 °。该古地磁极与赣州地区河湖相红层
的古地磁极及华南晚白垩世的古地磁极位置一致，表明风成红层的剩磁记录是可靠的。河口组河流相红层绝大部分样品
未能分离出稳定的特征剩磁。磁化率各向异性结果显示塘边组和河口组为沉积组构。岩石磁学结果表明，载磁矿物为赤
铁矿和磁铁矿。通过对塘边组风成红层的薄片观察和红度值比较等进一步研究表明，颗粒粒度和胶结程度可能对红层剩
磁记录的稳定性有一定影响。
|
| 关 键 词： | 古地磁 风成红层 晚白垩世 信江盆地 华南 |
Paleomagnetism of the Upper Cretaceous Aeolian Red Beds in Xinjiang Basin,Jiangxi Province,China |
| |
| LUO Xi,LI Yongxiang,LI Xianghui.Paleomagnetism of the Upper Cretaceous Aeolian Red Beds in Xinjiang Basin,Jiangxi Province,China[J].Geological Journal of China Universities,2019,25(5):779. |
| |
| Authors: | LUO Xi LI Yongxiang LI Xianghui |
| |
| Abstract: | Red bed is one of the important targets in paleomagnetic studies. Previous research has focused mainly on paleomagnetism
of lacustrine-fluvial red beds, while paleomagnetism of aeolian red beds has been rarely investigated. As a result, the reliability of
paleomagnetic data from aeolian red beds and the remanence acquisition in different depositional processes remain poorly understood.
In this study, we carried out a paleomagnetic study of the Upper Cretaceous aeolian red beds from the Tangbian Formation (Fm) and
lacustrine-fluvial red beds from the Hekou Fm of the Guifeng Group in Xinjiang Basin, Jiangxi Province, China. The purposes of this
study are to investigate the reliability of the paleomagnetic records of aeolian red beds and the influence of different depositional
processes on magnetic remanence acquisition by comparing the paleomagnetic data of aeolian red beds and those of lacustrine-fluvial
red beds. Stepwise thermal demagnetization of the samples shows that only 19% of the aeolian red beds samples of Tangbain Fm yield
stable characteristic remanent magnetizations (ChRMs) with convex intensity decay curves, indicating a primary origin of remanence
carried by detrital hematite grains. The mean of the ChRMs of the Tangbian Fm is Ds=15.6 °, Is=28.9 °, n=25, κ=13.0, α95=8.3 ° after
tilt correction, corresponding to a Late Cretaceous paleopole at Latitude=70.7 °, Longitude=245.6 °, A95=6.8 °. The new paleopole is
indistinguishable with the coeval paleopole from lacustrine-fluvial red beds of the Ganzhou area and the recently updated Late
Cretaceous paleopole of South China, suggesting that the aeolian red beds of the Tangbian Fm can carry reliable paleomagnetic records.
Most lacustrine-fluvial red bed samples from the Hekou Fm failed to yield stable ChRMs. The anisotropy of magnetic susceptibility
(AMS) data of the Tangbian Fm and the Hekou Fm indicate sedimentary fabrics. Rock magnetic results of representative samples show
that remanence are carried by hematite and magnetite. Further investigations of the Tangbain Fm aeolian red beds with thin section
observations and redness analysis indicate that particle size and degree of cementation may affect the stability of remanent
magnetization of aeolian red beds. |
| |
| Keywords: | paleomagnetism aeolian red beds Late Cretaceous Xinjiang Basin South China |
|
| 点击此处可从《高校地质学报》浏览原始摘要信息 |
| 点击此处可从《高校地质学报》下载免费的PDF全文 |
|
