Regional nutrient decrease drove redox stabilisation and metazoan diversification in the late Ediacaran Nama Group, Namibia
Abstract
The late Ediacaran witnessed an increase in metazoan diversity and ecological complexity, marking the inception of the Cambrian Explosion. To constrain the drivers of this diversification, we combine redox and nutrient data for two shelf transects, with an inventory of biotic diversity and distribution from the Nama Group, Namibia (~550 to ~538 Million years ago; Ma). Unstable marine redox conditions characterised all water depths in inner to outer ramp settings from ~550 to 547 Ma, when the first skeletal metazoans appeared. However, a marked deepening of the redoxcline and a reduced frequency of anoxic incursions onto the inner to mid-ramp is recorded from ~547 Ma onwards, with full ventilation of the outer ramp by ~542 Ma. Phosphorus speciation data show that, whilst anoxic ferruginous conditions were initially conducive to the drawdown of bioavailable phosphorus, they also permitted a limited degree of phosphorus recycling back to the water column. A long-term decrease in nutrient delivery from continental weathering, coupled with a possible decrease in upwelling, led to the gradual ventilation of the Nama Group basins. This, in turn, further decreased anoxic recycling of bioavailable phosphorus to the water column, promoting the development of stable oxic conditions and the radiation of new mobile taxa.
Citation
Bowyer , F T , Shore , A J , Wood , R A , Alcott , L J , Thomas , A L , Butler , I B , Curtis , A , Hainanan , S , Curtis-Walcott , S , Penny , A & Poulton , S W 2020 , ' Regional nutrient decrease drove redox stabilisation and metazoan diversification in the late Ediacaran Nama Group, Namibia ' , Scientific Reports , vol. 10 , 2240 , pp. 1-11 . https://doi.org/10.1038/s41598-020-59335-2
Publication
Scientific Reports
Status
Peer reviewed
ISSN
2045-2322Type
Journal article
Description
FB was funded by a NERC DTP (Grant award code NE/L002558/1), and RW and SWP by the NERC BETR Project (Grant award code NE/P013643/1). AS was funded by the School of GeoSciences, University of Edinburgh, and LA was funded by a Leeds Anniversary Research Scholarship. SWP acknowledges financial support from a Royal Society Wolfson Research Merit Award and a Leverhulme Research Fellowship.Collections
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