Extinction of Cloudina and Namacalathus at the Precambrian-Cambrian boundary in Oman

Amthor, Joachim E.; Grotzinger, J. P.; Schröder, Stefan; Bowring, Samuel A.; Ramezani, Jahandar; Martin, Mark W.; Matter, Albert

doi:10.1130/0091-7613(2003)031<0431:eocana>2.0.co;2

Cited by 471 publications

(325 citation statements)

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“…This distinctive early calcified biota of stem group Eumetazoa, Cnidaria and Bilateria, or Cnidaria (Wood, 2011) terminates globally at the Precambrian/Cambrian boundary at ~541 Ma (Amthor et al, 2003). A greater diversity of body plans and skeletal organisations, including recognizable stem-group members of extant bilaterian phyla, is subsequently recorded in the first 10 Myr of the Cambrian (Knoll, 2003).…”

Section: Page 8 Of 74mentioning

confidence: 99%

Dynamic redox conditions control late Ediacaran metazoan ecosystems in the Nama Group, Namibia

Wood

Poulton

Prave

et al. 2015

Precambrian Research

167

194

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A c c e p t e d M a n u s c r i p t 3 ABSTRACTThe first appearance of skeletal metazoans in the late Ediacaran (~550 million years ago; Ma) has been linked to the widespread development of oxygenated oceanic conditions, but a precise spatial and temporal reconstruction of their evolution has not been resolved. Here we consider the evolution of ocean chemistry from ~550 to ~541 Ma across shelf-to-basin transects in the Zaris and Witputs Sub-Basins of the Nama Group, Namibia. New carbon isotope data capture the final stages of the Shuram/Wonoka deep negative C-isotope excursion, and these are complemented with a reconstruction of water column redox dynamics utilizing Fe-S-C systematics and the distribution of skeletal and soft-bodied metazoans. Combined, these inter-basinal datasets provide insight into the potential role of ocean redox chemistry during this pivotal interval of major biological innovation.The strongly negative  13 C values in the lower parts of the sections reflect both a secular, global change in the C-isotopic composition of Ediacaran seawater, as well as the influence of 'local' basinal effects as shown by the most negative  13 C values occurring in the transition from distal to proximal ramp settings. Critical, though, is that the transition to positive  13 C values postdates the appearance of calcified metazoans, indicating that the onset of biomineralization did not occur under post-excursion conditions. Significantly, we find that anoxic and ferruginous deeper water column conditions were prevalent during and after the transition to positive  13 C that marks the end of the Shuram/Wonoka excursion. Thus, if the C isotope trend reflects the transition to global-scale oxygenation in the aftermath of the oxidation of a large-scale, isotopically light organic carbon pool, it was not sufficient to fully oxygenate the deep ocean. Page 4 of 74A c c e p t e d M a n u s c r i p t 4 Both sub-basins reveal highly dynamic redox structures, where shallow, inner ramp settings experienced transient oxygenation. Anoxic conditions were caused either by episodic upwelling of deeper anoxic waters or higher rates of productivity. These settings supported short-lived and monospecific skeletal metazoan communities. By contrast, microbial (thrombolite) reefs, found in deeper inner-and mid-ramp settings, supported more biodiverse communities with complex ecologies and large skeletal metazoans. These long-lived reef communities, as well as Ediacaran soft-bodied biotas, are found particularly within transgressive systems, where oxygenation was persistent. We suggest that a mid-ramp position enabled physical ventilation mechanisms for shallow water column oxygenation to operate during flooding and transgressive sea-level rise. Our data support a prominent role for oxygen, and for stable oxygenated conditions in particular, in controlling both the distribution and ecology of Ediacaran skeletal metazoan communities.Keywords: Oxygenation; Neoproterozoic; Biomineralisation; Metazoans; Ediacaran; Ecosystems Introductio...

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Section: Page 8 Of 74mentioning

confidence: 99%

Dynamic redox conditions control late Ediacaran metazoan ecosystems in the Nama Group, Namibia

Wood

Poulton

Prave

et al. 2015

Precambrian Research

167

194

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“…Fossils that can be reasonably interpreted as diploblastic-grade metazoans with biomineralized skeletons are represented by a few but locally abundant forms in the upper Ediacaran strata (Grant, 1990;Grotzinger, Watters & Knoll, 2000;Grotzinger, Adams & Schröder, 2005;Wood, Grotzinger & Dixon, 2002;Amthor et al 2003; online Appendix 1 at http://journals.cambridge.org/geo). There is also a variety of mineralized solitary and modular calcareous corallomorphs in the lower Cambrian (Debrenne, Lafuste & Zhuravlev, 1990).…”

Section: B Cnidariomorphs and Problematic Tubular Formsmentioning

confidence: 99%

“…The age of the Precambrian-Cambrian boundary, marked worldwide by a negative carbon isotope anomaly, is dated in the well-constrained section in Oman to 542 ± 0.3 Ma (Amthor et al 2003), later revised to 541 ± 0.13 Ma (Bowring et al 2007). An associated biotic crisis is inferred from the disappearance of the Ediacaran biota (e.g.…”

Section: Chronology Of Early Cambrian Biomineralizationmentioning

confidence: 99%

Chronology of early Cambrian biomineralization

et al. 2011

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-Data on the first appearances of major animal groups with mineralized skeletons on the Siberian Platform and worldwide are revised and summarized herein with references to an improved carbon isotope stratigraphy and radiometric dating in order to reconstruct the Cambrian radiation (popularly known as the 'Cambrian explosion') with a higher precision and provide a basis for the definition of Cambrian Stages 2 to 4. The Lophotrochozoa and, probably, Chaetognatha were first among protostomians to achieve biomineralization during the Terreneuvian Epoch, mainly the Fortunian Age. Fast evolutionary radiation within the Lophotrochozoa was followed by radiation of the sclerotized and biomineralized Ecdysozoa during Stage 3. The first mineralized skeletons of the Deuterostomia, represented by echinoderms, appeared in the middle of Cambrian Stage 3. The fossil record of sponges and cnidarians suggests that they acquired biomineralized skeletons in the late Neoproterozoic, but diversification of both definite sponges and cnidarians was in parallel to that of bilaterians. The distribution of calcium carbonate skeletal mineralogies from the upper Ediacaran to lower Cambrian reflects fluctuations in the global ocean chemistry and shows that the Cambrian radiation occurred mainly during a time of aragonite and high-magnesium calcite seas.

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“…10). Other carbonate dominated, Precambrian-Cambrian boundary successions that contain the N sC isotopic event include Oman (Amthor et al, 2003), China (Lambert et al, 1987), Mongolia (Brasier et al, 1996), and Morocco (Tucker, 1986). SB 4 is easily correlated into the Mackenzie Mountains.…”

Section: Global Correlationsmentioning

confidence: 99%

“…The age of this boundary (ca. 543 Ma) is based on U-Pb zircon dates from Namibia , Siberia (Bowring et al, 1993) and Oman (Amthor et al, 2003). Testing the timing of multiple, globally synchronous glacial events by radiometric dating has not been possible (Evans, 2000).…”

Section: Global Correlationsmentioning

confidence: 99%

Integrated Ediacaran chronostratigraphy, Wernecke Mountains, northwestern Canada

Pyle

Narbonne

James

et al. 2004

Precambrian Research

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Terminal Neoproterozoic (Ediacaran, ca. 600-543 Ma) strata of the upper part of the Windermere Supergroup are well-exposed in the Mackenzie Mountains and the Wernecke Mountains of northwestern Canada. Windermere strata in the Mackenzie Mountains contain an exceptional Ediacaran biostratigraphic and isotopic (C and Sr) record, while the sequence stratigraphic record is subtle throughout this predominantly deep-water succession. Coeval strata in the Wernecke Mountains can be correlated with the succession in the Mackenzie Mountains on a formational level. In contrast to the deep-water setting of the Mackenzies succession, the Werneckes succession preserves a predominantly shallow-water succession amenable to detailed sequence stratigraphy. Integrated lithostratigraphy, chemostratigraphy, biostratigraphy and sedimentology partitions the Wernecke Mountains succession into five depositional sequences and constrains correlation with strata in the Mackenzie Mountains. The siliciclastic and carbonate sediments, deposited along the margin of the proto-Pacific Ocean, record accumulation in continental slope, neritic, and terrestrial paleoenvironments. Distinctive temporal chemostratigraphic and biostratigraphic attributes allow these strata to be correlated with other Ediacaran successions worldwide. Integrating sequence stratigraphy with these attributes is a robust, yet under-utilized correlation tool and is a step toward erecting a more detailed working Neoproterozoic chronostratigraphy.

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Extinction of Cloudina and Namacalathus at the Precambrian-Cambrian boundary in Oman

Cited by 471 publications

References 11 publications

Dynamic redox conditions control late Ediacaran metazoan ecosystems in the Nama Group, Namibia

Dynamic redox conditions control late Ediacaran metazoan ecosystems in the Nama Group, Namibia

Chronology of early Cambrian biomineralization

Integrated Ediacaran chronostratigraphy, Wernecke Mountains, northwestern Canada

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