气候变化领域集成服务门户(CCPortal): Paleomagnetism and rock magnetic cyclostratigraphy of the Ediacaran Doushantuo Formation; South China: Constraints on the remagnetization mechanism and the encoding process of Milankovitch cycles

CCPortal

DOI	10.1016/j.palaeo.2019.05.002
	Paleomagnetism and rock magnetic cyclostratigraphy of the Ediacaran Doushantuo Formation; South China: Constraints on the remagnetization mechanism and the encoding process of Milankovitch cycles
	Gong Z.; Kodama K.P.; Li Y.-X.
发表日期	2019
ISSN	0031-0182
起始页码	232
结束页码	246
卷号	528
英文摘要	South China provides exceptional and unique sedimentary archives of Earth's fundamental changes in Ediacaran time. However, the lack of robust geochronological constraints renders a poorly-defined chronostratigraphic framework for Ediacaran-aged strata in South China, thus making it difficult to understand Earth's critical changes during this time interval. Magnetostratigraphy and rock magnetic cyclostratigraphy turn out to be a few reliable methods in chronostratigraphic studies, especially in the Precambrian. Here, we present a detailed paleomagnetic and rock magnetic study of the Ediacaran Doushantuo Formation in the Huanglianba section, Guizhou Province, South China. The section consists of ~75 m thick carbonate succession and has a record of one of the largest carbon isotope excursions in the Earth history, known as the Shuram excursion. Stepwise thermal demagnetization of Doushantuo carbonates reveals single-component magnetizations that yield a paleomagnetic pole consistent with the Late Triassic segment of the apparent polar wander path of South China. The secondary origin of Doushantuo carbonates' magnetization is supported by their magnetic mineralogy based on various rock magnetic experiments and scanning electron microscopic analyses. We interpret that the secondary magnetization resides mainly in authigenic pyrrhotite that likely precipitated from the reducing fluids during the late stage of Indosinian orogeny in the Triassic. Interestingly, the companion high-resolution cyclostratigraphic study of a 4-m thick succession at the upper layers of the Doushantuo Formation in the Huanglianba section indicates that the Milankovitch cycles were encoded in the variation of magnetic susceptibility, immune from the influence of remagnetization. Variation of magnetic susceptibility is attributed to changes in the abundance of paramagnetic minerals which, by implication, means that the amount of terrestrial materials transported from the continent was regulated by Milankovitch cycles during the deposition of Doushantuo carbonates. Therefore, our results suggest that even though carbonates are prone to remagnetization, astronomical modulation of deposition could be encoded in rock magnetics of the remagnetized carbonates. As a result, rock magnetic cyclostratigraphy has potential in remagnetized carbonates for providing a floating astronomical timescale that can be applied to constrain sediment accumulation rates, estimate the duration of geological events, and construct high-resolution chronostratigraphies. © 2019 Elsevier B.V.
英文关键词	Chemical remanent magnetization; Chronostratigraphy; Paramagnetic minerals; Shuram carbon isotope excursion; Spectral analysis
语种	英语
来源期刊	Palaeogeography, Palaeoclimatology, Palaeoecology
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/150921
作者单位	Department of Geology and Geophysics, Yale University, 210 Whitney Avenue, New Haven, CT 06511, United States; Department of Earth and Environmental Sciences, Lehigh University, 1 West Packer Avenue, Bethlehem, PA 18015, United States; State Key Laboratory for Mineral Deposit Research, School of Earth Sciences and Engineering, Nanjing University, 163 Xianlin Avenue, Nanjing, 210023, China
推荐引用方式 GB/T 7714	Gong Z.,Kodama K.P.,Li Y.-X.. Paleomagnetism and rock magnetic cyclostratigraphy of the Ediacaran Doushantuo Formation; South China: Constraints on the remagnetization mechanism and the encoding process of Milankovitch cycles[J],2019,528.
APA	Gong Z.,Kodama K.P.,&Li Y.-X..(2019).Paleomagnetism and rock magnetic cyclostratigraphy of the Ediacaran Doushantuo Formation; South China: Constraints on the remagnetization mechanism and the encoding process of Milankovitch cycles.Palaeogeography, Palaeoclimatology, Palaeoecology,528.
MLA	Gong Z.,et al."Paleomagnetism and rock magnetic cyclostratigraphy of the Ediacaran Doushantuo Formation; South China: Constraints on the remagnetization mechanism and the encoding process of Milankovitch cycles".Palaeogeography, Palaeoclimatology, Palaeoecology 528(2019).