Oxygen minimum zones in the early Cambrian ocean

Guilbaud, Romain; Slater, Ben J.; Poulton, Simon W.; Harvey, Thomas H. P.; Brocks, Jochen J.; Nettersheim, Benjamin J.; Butterfield, Nicholas J.

doi:10.7185/geochemlet.1806

Cited by 46 publications

(28 citation statements)

References 25 publications

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“…At least some biotas throughout this interval were subject to upwelling incursions of oxygen deficient water, controlled by local changes in relative sea level and productivity (77).…”

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confidence: 99%

Integrated records of environmental change and evolution challenge the Cambrian Explosion

et al. 2019

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The 'Cambrian Explosion' describes the rapid increase in animal diversity and abundance, as manifest in the fossil record, between ~ 540 and 520 million years ago (Ma). This event, however, is nested within a far more ancient record of macrofossils extending at least into the late Ediacaran, ~571 Ma. The evolutionary events documented during the Ediacaran-Cambrian interval coincide with geochemical evidence for the modernisation of Earth's biogeochemical cycles. Holistic integration of fossil and geochemical records leads us to challenge the notion that the Ediacaran and Cambrian worlds were markedly distinct, and places biotic and environmental change within a longer-term narrative. We propose that the evolution of metazoans may have been facilitated by a series of dynamic and global changes in redox conditions and nutrient supply, which, together with potential biotic feedbacks, enabled turnover events that sustained phases of radiation. In this synthesis, we argue that early metazoan diversification should be recast as a series of successive, transitional radiations that extended from the late Ediacaran and continued through the early Palaeozoic. We conclude that while the Cambrian Explosion represents a radiation of crown-group bilaterians, it was simply one phase amongst several older, and younger, metazoan radiations.

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“…At least some biotas throughout this interval were subject to upwelling incursions of oxygen deficient water, controlled by local changes in relative sea level and productivity (77).…”

Section: ____________________________________________________________mentioning

confidence: 99%

Integrated records of environmental change and evolution challenge the Cambrian Explosion

et al. 2019

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“…SCFs appear to fulfil these criteria, at least during the latest Ediacaran and early Cambrian (Guilbaud et al . ; Slater et al . ; Slater & Willman ).…”

Section: Discussionmentioning

confidence: 99%

Cochleatina: an enigmatic Ediacaran–Cambrian survivor among small carbonaceous fossils (SCFs)

et al. 2020

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Conspicuously few body‐fossil taxa are known to span the Ediacaran–Cambrian boundary, a pattern usually taken to signal either a terminal Proterozoic mass extinction, or taphonomic failure. We draw attention to the emerging record of small carbonaceous fossils (SCFs), which exhibit continuous preservation spanning this critical interval. Here we focus on the enigmatic SCF Cochleatina, a morphologically complex coil‐shaped problematicum that ranges across the Ediacaran–Cambrian divide, and is potentially among the oldest fossil occurrences of metazoans. We report new material of Cochleatina canilovica from the Ediacaran of Estonia and Ukraine, which offers new characters for assessing its palaeobiology. Significantly, new specimens include sets of three‐alike triplets of Cochleatina adhering to organic sheets, suggesting a clustering habit, or grouping of elements within an individual during life; an important step in constraining the morphology and ecology of this Ediacaran–Cambrian problematicum. We present revised systematic descriptions for Cochleatina and C. canilovica, and critically evaluate previous biological interpretations, drawing comparisons with metazoan, algal and protistan analogues. We reject hypotheses supporting Cochleatina as a metazoan mouthpart, and suggest new grounds for viewing Cochleatina as a potential multicomponent predator that trapped protists among microbial mats. Most occurrences are from Baltica, but we synthesize sporadic reports of Cochleatina from other palaeocontinents, pointing to its global distribution during the latest ˜10 myr of the Ediacaran and majority of the earliest Cambrian Fortunian Stage. As a rare example of an ‘Ediacaran survivor’, Cochleatina highlights the broader significance of SCFs as a novel means of tracking evolutionary patterns through the Proterozoic–Phanerozoic transition.

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“…Indeed, ferruginous water column conditions have been recorded from shallow marine sediments deposited above fair weather wave base in the final 10 million years of the Ediacaran 5,6 . The observed variability in the local redox of late Ediacaran and early Cambrian marine environments may correspond to the relative distance from, and spatial extent of, oxygen minimum zones (OMZs) that developed in response to local productivity and resultant organic matter remineralization 10 . Spatially variable rates of primary production, in turn, are likely to reflect the provision of limiting nutrients, in particular phosphorus (P), which is commonly considered the ultimate limiting nutrient on geological timescales 11 .…”

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confidence: 99%

Regional nutrient decrease drove redox stabilisation and metazoan diversification in the late Ediacaran Nama Group, Namibia

Bowyer

Shore

Wood

et al. 2020

Sci Rep

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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.

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Oxygen minimum zones in the early Cambrian ocean

Cited by 46 publications

References 25 publications

Integrated records of environmental change and evolution challenge the Cambrian Explosion

Integrated records of environmental change and evolution challenge the Cambrian Explosion

Cochleatina: an enigmatic Ediacaran–Cambrian survivor among small carbonaceous fossils (SCFs)

Regional nutrient decrease drove redox stabilisation and metazoan diversification in the late Ediacaran Nama Group, Namibia

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