Sedimentology, diagenesis, and stratigraphic occurrence of giant ooids in the Ediacaran Rainstorm Member, Johnnie Formation, Death Valley region, California

Trower, Elizabeth J.; Grotzinger, J. P.

doi:10.1016/j.precamres.2010.03.007

Cited by 33 publications

(13 citation statements)

References 43 publications

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“…The influence of unusual seawater chemistry during this interval is further supported by examples of anomalously large carbonate skeletons, grains, and structures that exceed Cambrian equivalents by one to two orders of magnitude: (i) the skeletal taxa Namapokia in the Nama Group, Namibia, which reaches diameters of over 1 m [41], (ii) densely aggregating metazoan reefs with volumetrically significant syn-sedimentary cement more than 10 m in width [31], (iii) Suvorovella shell beds ca 1 km length, and (iv) widespread distribution of giant aragonite and high-Mg calcite ooids [42]. Generally, high alkalinity is also consistent with both the global dominance of carbonate lithologies in terminal Ediacaran successions [43] and the extremely high estimated carbonate sediment accumulation rates for this interval, e.g.…”

Section: The Role Of High Carbonate Supersaturationmentioning

confidence: 99%

First macrobiota biomineralization was environmentally triggered

2017

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Why large and diverse skeletons first appeared 550 Ma is not well understood. Many Ediacaran skeletal biota show evidence of flexibility, and bear notably thin skeletal walls with simple, non-hierarchical microstructures of either aragonite or high-Mg calcite. We present evidence that the earliest skeletal macrobiota, found only in carbonate rocks, had close soft-bodied counterparts hosted in contemporary clastic rocks. This includes the calcareous discoidal fossil similar to holdfasts of Ediacaran biota taxa previously known only as casts and moulds, as well as tubular and vase-shaped fossils. In sum, these probably represent taxa of diverse affinity including unicellular eukaryotes, total group cnidarians and problematica. Our findings support the assertion that the calcification was an independent and derived feature that appeared in diverse groups where an organic scaffold was the primitive character, which provided the framework for interactions between the extracellular matrix and mineral ions. We conclude that such skeletons may have been acquired with relative ease in the highly saturated, high alkalinity carbonate settings of the Ediacaran, where carbonate polymorph was further controlled by seawater chemistry. The trigger for Ediacaran biomineralization may have been either changing seawater Mg/Ca and/or increasing oxygen levels. By the Early Cambrian, however, biomineralization styles and the range of biominerals had significantly diversified, perhaps as an escalating defensive response to increasing predation pressure. Indeed skeletal hardparts had appeared in clastic settings by Cambrian Stage 1, suggesting independence from ambient seawater chemistry where genetic and molecular mechanisms controlled biomineralization and mineralogy had become evolutionarily constrained.

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Section: The Role Of High Carbonate Supersaturationmentioning

confidence: 99%

First macrobiota biomineralization was environmentally triggered

2017

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“…Ediacaran macrobiota biomineralization, including the first possible metazoan calcification, was probably facilitated by the high carbonate supersaturation and alkalinity suggested to have been present in Ediacaran shallow marine carbonate settings(56). This has been inferred due to the presence of anomalously large carbonate skeletons, cements, and ooids(32,56,57), as well as the global dominance of carbonate lithologies in terminal Ediacaran successions and high estimated carbonate sediment accumulation rates for this interval that exceed Cambrian equivalents by one to two orders of magnitude…”

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confidence: 99%

Exploring the drivers of early biomineralization

Wood

2018

Emerging Topics in Life Sciences

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points:  The first skeletons are known from protists, 810 Million years ago (Ma)  Large, putative metazoan, calcareous skeletons first appear in the terminal Ediacaran, ~550 Ma. Calcification was an independent and derived feature that appeared in diverse groups. The presence of a pre-existing organic scaffold, which provided the framework for interactions between extracellular matrix and mineral ions, can be inferred in many skeletal taxa. Calcareous biomineralization may have been favoured in the highly saturated, high alkalinity carbonate settings of the Ediacaran, where carbonate polymorph was further controlled by seawater chemistry. By the Early Cambrian, there is a marked increase in the diversity of skeletons as an escalating defensive response to increasing predation pressure, and biomineralization may have come under stronger biological control. The initial triggers for widespread biomineralization in the Ediacaran remain unclear. AbstractThe first biomineralised hard-parts are known from ~810 Million years ago (Ma), consisting of phosphatic plates of probable protists formed under active biological control. Large skeletons in diverse taxa, probably including total-group poriferans and total-group cnidarians, first appear in the terminal Ediacaran, ~550 Ma. This is followed by a substantial increase in abundance, diversity, and mineralogy during the early Cambrian. The biological relationship of Ediacaran to early Cambrian skeletal biota is unclear, but tubular skeletal fossils such as Cloudina and Anabarites straddle the transition. Many Ediacaran skeletal biota are found exclusively in carbonate settings, and present skeletons whose form infers an organic scaffold which provided the framework for interactions between extracellular matrix and mineral ions. Several taxa have close soft-bodied counterparts hosted in contemporary clastic rocks. This supports the assertion that the calcification was an independent and derived feature that appeared in diverse groups, that was initially acquired with minimal biological control in the highly saturated, high alkalinity carbonate settings of the Ediacaran, where carbonate polymorph was further controlled by seawater chemistry. The trigger for Ediacaran-Cambrian biomineralization is far from clear, but may have been either changing seawater Mg/Ca ratios that facilitated widespread aragonite and high-Mg calcite precipitation, and/or increasing or stabilising oxygen levels. By the Early Cambrian, the diversity of biomineralization styles may have been an escalating defensive response to increasing predation pressure, with skeletal hardparts first appearing in abundance in clastic settings by the Fortunian. This marks full independence from ambient seawater chemistry and significant biological control of biomineralization.

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“…Based on the giant ooid occurrences documented by Sumner and Grotzinger (1993), with the addition of occurrences described more recently (Batten et al, 2004;Day et al, 2004;Fromhold & Wallace, 2011;Macdonald, et al, 2009aMacdonald, et al, , 2009bPetrov, 2018;Srivastava, 2006;Thorie et al, 2018;Trower & Grotzinger, 2010), Neoproterozoic giant ooids range from 2 to 25 mm in diameter (D) ( Table 1). Within this range, D = 5 mm and D = 10 mm were chosen as representative grain sizes for which to assess characteristic Ω values-the former representative of a grain diameter observed in the majority of the giant ooid deposits and the latter a conservative representative of the largest ooids in these deposits (Table 1).…”

Section: Methodsmentioning

confidence: 99%