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Early Cambrian oxygen minimum zone-like conditions at Chengjiang

Hammarlund, Emma U. LU ; Gaines, Robert R.; Prokopenko, Maria G.; Qi, Changshi; Hou, Xian Guang and Canfield, Donald E (2017) In Earth and Planetary Science Letters 475. p.160-168
Abstract

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... (More)

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.

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published
subject
keywords
Burgess Shale type preservation, Cambrian, Chengjiang, geochemistry, oxygen minimum zone, water column chemistry
in
Earth and Planetary Science Letters
volume
475
pages
9 pages
publisher
Elsevier
external identifiers
  • scopus:85027106901
  • wos:000411167800015
ISSN
0012-821X
DOI
10.1016/j.epsl.2017.06.054
language
English
LU publication?
yes
id
ec3d0811-7dda-47c2-bc30-41b85f51fffc
date added to LUP
2017-08-31 16:36:11
date last changed
2018-04-08 05:00:15
@article{ec3d0811-7dda-47c2-bc30-41b85f51fffc,
  abstract     = {<p>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.</p>},
  author       = {Hammarlund, Emma U. and Gaines, Robert R. and Prokopenko, Maria G. and Qi, Changshi and Hou, Xian Guang and Canfield, Donald E},
  issn         = {0012-821X},
  keyword      = {Burgess Shale type preservation,Cambrian,Chengjiang,geochemistry,oxygen minimum zone,water column chemistry},
  language     = {eng},
  month        = {10},
  pages        = {160--168},
  publisher    = {Elsevier},
  series       = {Earth and Planetary Science Letters},
  title        = {Early Cambrian oxygen minimum zone-like conditions at Chengjiang},
  url          = {http://dx.doi.org/10.1016/j.epsl.2017.06.054},
  volume       = {475},
  year         = {2017},
}