Controls on fossil pyritization: Redox conditions, sedimentary organic matter content, and Chuaria preservation in the Ediacaran Lantian Biota

doi:10.1016/j.palaeo.2016.05.013

	Controls on fossil pyritization: Redox conditions, sedimentary organic matter content, and Chuaria preservation in the Ediacaran Lantian Biota
	Guan, C. (关成国); Wang, W. (王伟（女）); Zhou, C. (周传明); A.D.Muscente; Wan B. (万斌); Chen Xiang; Yuan, XL (袁训来); Chen Z (陈哲); ouyang q (欧阳晴)
	2017
发表期刊	Palaeogeography, Palaeoclimatology, Palaeoecology
ISSN	0031-0182
卷号	474 页码:26-35
摘要	Pyritization represents a major taphonomic pathway for exceptional preservation of soft tissues. Although various Ediacaran Lagerstatten contain pyritized fossils, the controls on this taphonomic pathway prior to the Precambrian-Phanerozoic transition have only recently received significant attention, and no studies have yet thoroughly investigated environmental conditions facilitating exceptional preservation via pyritization in the early Ediacaran. Here, we investigate the preservational environments of macroscopic fossil Chuaria in the early Ediacaran Lantian Formation of South China using petrographic, electron microscopic, and geochemical data. Chuaria occur as pervasively pyritized (spheroid-shaped) globose and non-pervasively pyritized (disk shaped) subglobose fossils in different stratigraphic intervals. Although these different stratigraphic intervals are similar in terms of total sulfur (TS, similar to 5%), subglobose Chuaria shales have greater total organic carbon (TOC, similar to 7.9%) contents than globose Chuaria shales (similar to 3.6%). Additionally, petrographic observations and TOC-TS cross-plots suggest that, whereas globose fossils were preserved under suboxic bottom waters, the subglobose fossils were preserved in euxinic bottom waters. Overall, these results affirm that pyritization in the Precambrian was generally favored in organic-poor, reactive iron-rich, sulfate-rich environments probably with slow sedimentation rates. When organics were scarce and reactive iron was abundant, bacterial sulfate reduction (BSR) created hydrogen sulfide and reactive iron concentration gradients around fossils, which kinetically and thermodynamically favored rapid and pervasive pyritization, as observed in globose Chuaria. Conversely, when organics were abundant and reactive iron/sulfate availabilities were limited by widespread BSR, fossils were relatively rapidly buried beneath the BSR metabolic zone of sediment, where they were principally preserved as aluminosilicified carbonaceous fossils that were compacted into subglobose forms. Thus, preservational variations among pyritized fossils in the Ediacaran may reflect differences in sedimentary organic matter content and/or bottom water redox chemistry. (C) 2016 Elsevier B.V. All rights reserved.
关键词	Lantian Biota Chuaria Pyritization Taphonomy Black shale
DOI	10.1016/j.palaeo.2016.05.013
收录类别	SCI
语种	英语
WOS研究方向	Physical Geography ; Geology ; Paleontology
WOS类目	Geography, Physical ; Geosciences, Multidisciplinary ; Paleontology
WOS记录号	WOS:000399261500003
出版者	ELSEVIER SCIENCE BV
文献类型	期刊论文
条目标识符	http://ir.nigpas.ac.cn/handle/332004/12890
专题	中国科学院南京地质古生物研究所其他
通讯作者	Zhou, C. (周传明)
推荐引用方式 GB/T 7714	Guan, C. ,Wang, W. ,Zhou, C. ,et al. Controls on fossil pyritization: Redox conditions, sedimentary organic matter content, and Chuaria preservation in the Ediacaran Lantian Biota[J]. Palaeogeography, Palaeoclimatology, Palaeoecology,2017,474:26-35.
APA	Guan, C. .,Wang, W. .,Zhou, C. .,A.D.Muscente.,Wan B. .,...&ouyang q .(2017).Controls on fossil pyritization: Redox conditions, sedimentary organic matter content, and Chuaria preservation in the Ediacaran Lantian Biota.Palaeogeography, Palaeoclimatology, Palaeoecology,474,26-35.
MLA	Guan, C. ,et al."Controls on fossil pyritization: Redox conditions, sedimentary organic matter content, and Chuaria preservation in the Ediacaran Lantian Biota".Palaeogeography, Palaeoclimatology, Palaeoecology 474(2017):26-35.