期刊
EARTH AND PLANETARY SCIENCE LETTERS
卷 475, 期 -, 页码 160-168出版社
ELSEVIER
DOI: 10.1016/j.epsl.2017.06.054
关键词
Chengjiang; Burgess Shale type preservation; Cambrian; geochemistry; oxygen minimum zone; water column chemistry
资金
- Danish National Research Foundation [DNRF53]
- National Science Foundation [EAR-1046233]
- National Natural Science Foundation of China [NSFC 41440023]
- National Natural Science Foundation of China (Villum Foundation)
- National Natural Science Foundation of China (NSFC-Yunnan Joint Foundation) [U1302232]
- Villum Fonden [00016518] Funding Source: researchfish
The early Cambrian succession at Chengjiang contains the most diverse Cambrian fossil assemblage yet described, and contributes significantly to our understanding of the diversification of metazoans in the Cambrian explosion. The Cambrian Period occupies a transitional episode of global ocean chemistry, following the oxygenation of the surface ocean and of shallow marine environments during the Ediacaran Period, but prior to the establishment of a predominantly oxygenated deep ocean in the mid -Paleozoic. Despite recent attention, a detailed understanding of the chemical conditions that prevailed in early Cambrian marine settings and the relationship of those conditions to early metazoan ecosystems is still emerging. Here, we report multi-proxy geochemical data from two drill cores through the early Cambrian (Series 2) Yu'anshan Formation of Yunnan, China. Results reveal dynamic water-column chemistry within the succession, which progressively shifted from euxinic to oxic conditions during deposition of the Yu'anshan Formation. The Chengjiang biota occurs in strata that appear to have been deposited under an oxygen-depleted water column that may have supported denitrification, as in modern oxygen-minimum zones. The oxygenated benthic environments in which the Chengjiang biota thrived were proximal to, but sharply separated from, the open ocean by a persistent anoxic water mass that occupied a portion of the outer shelf. Oxygen depletion in the lower water column developed dynamically in response to nutrient availability and possibly at lower thresholds of productivity due to lower atmospheric oxygen concentrations in Cambrian. These findings suggest that the frequent development of oxygen-limiting conditions in continental margin settings provided an environmental barrier that may have affected biogeographic, ecological and evolutionary development of early metazoan communities. (C) 2017 Elsevier B.V. All rights reserved.
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