Ediacaran biota from Sonora, Mexico.

McMenamin, Mark A. S.

doi:10.1073/pnas.93.10.4990

Cited by 32 publications

(14 citation statements)

References 6 publications

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“…In any event, our data are consistent with those from other Neoproterozoic sections, in that there is only one negative excursion in the section that reaches values as low as -12‰, and the age of the excursion is Ediacaran. Assuming the Clemente oolite is correlative with the Johnnie oolite, then the occurrence of horizontal burrows and macroscopic body fossils below the Clemente oolite (McMenamin, 1996) would suggest that the excursion occurred after ca. 575 Ma (e.g., Knoll et al, 2004;Condon et al, 2005).…”

Section: Global Correlationsmentioning

confidence: 98%

“…Among other strong similarities between the two Ediacaran-Cambrian sections, the upper part of the Clemente Formation in Sonora contains the same lithostratigraphic triad characteristic as the Rainstorm Member in the Death Valley region (Stewart et al, 1984). The Ediacaran fossils were recovered from siltstones and fi ne sandstones from 10 to 75 m below the oolite horizon (McMenamin, 1996).…”

Section: Background Ediacaran Strata Of Southwest Laurentiamentioning

confidence: 99%

“…Extensive exposures of stratigraphically wellcharacterized, carbonate-bearing facies of these units occur in the Death Valley region of eastern California and southern Nevada (e.g., Stewart, 1970) but also include correlatives now exposed in northern Sonora, Mexico, that were tectonically displaced from the Death Valley region in Mesozoic time (Stewart et al, 1984;McMenamin , 1996).…”

Section: Introductionmentioning

confidence: 97%

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The Shuram and subsequent Ediacaran carbon isotope excursions from southwest Laurentia, and implications for environmental stability during the metazoan radiation

Verdel

Wernicke

Bowring

2011

Geological Society of America Bulletin

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Current understanding of secular changes in the carbon isotopic composition of midto late Ediacaran carbonates suggests a relatively long, steady recovery of the global ocean from the Shuram negative excursion, followed by a smaller negative excursion at the Precambrian-Cambrian boundary. New radiometric, stratigraphic, and carbon isotope data from thick exposures of the upper Johnnie Formation in the Panamint Range of eastern California, combined with data from carbonate-rich facies of the Stirling Quartzite in the Funeral Mountains, confi rm an Ediacaran age for these strata and provide a more complete record of isotopic variations during this time interval than previously determined from SW Laurentia and other key sections around the globe. A siltstone in the lower part of the Johnnie Formation yielded a detrital zircon grain with an age of 640.33 ± 0.09 Ma, lowering the maximum radiometric age constraint on the Johnnie Formation by >400 m.y., consistent with an Ediacaran age based on chemo-and biostratigraphic data. In contrast to previous C isotope compilations from this region, which were generally based on relatively thin portions of the Cordilleran miogeocline near its depositional hinge, the more basinward exposures exhibit a recovery from values near -12‰ to 0‰ within the upper part of the Johnnie Formation. Details in the shape of the chemostratigraphic profi le through the upper Johnnie Formation closely match those in profi les through the Wonoka Formation in South Australia (which lies above the basal Ediacaran global stratotype section and point) and the Shuram-Buah interval in Oman, confi rming temporal correlation and suggesting genesis through changes in the isotopic composition of the global ocean. The Shuram excursion in SW Laurentia is followed by at least three smaller Ediacaran to earliest Cambrian isotopic excursions recorded within, from oldest to youngest, the uppermost Johnnie Formation, the middle Stirling Quartzite, and the lower Wood Canyon Formation. These data indicate that the negative excursion associated with the base of the Cambrian is not a unique postShuram event, and that post-Shuram, preCambrian animal evolution occurred in an environment of repeated large-magnitude fl uctuations in the carbon isotopic composition of the global ocean.

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Section: Global Correlationsmentioning

confidence: 98%

Section: Background Ediacaran Strata Of Southwest Laurentiamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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The Shuram and subsequent Ediacaran carbon isotope excursions from southwest Laurentia, and implications for environmental stability during the metazoan radiation

Verdel

Wernicke

Bowring

2011

Geological Society of America Bulletin

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“…1). Previously reported fossils from these units, discussed below, were collected from nearby exposures in Cerro Rajón (McMenamin 1984, 1996; Stewart et al . 1984).…”

Section: Geologic Contextmentioning

confidence: 99%

“…Unit 1 is dominated by dolostone and sandy dolostone, with minor interbedded quartzite, shale and basalt; several occurrences of tubular microfossils have been reported (McMenamin et al . 1983, 1994; McMenamin 1996) and are thought to be internal molds of Cloudina (Grant 1990). Unit 2 is predominantly dolostone and sandy dolostone, and Unit 3 contains interfingering siltstone, quartzite, dolostone and basalt.…”

Section: Geologic Contextmentioning

confidence: 99%

Ediacaran and Cambrian Index Fossils From Sonora, Mexico

Sour-Tovar¹,

Hagadorn²,

Huitrón-Rubio³

2007

Palaeontology

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The Cambrian index fossil Treptichnus pedum is reported from the Puerto Blanco Formation near Pitiquito, Sonora, Mexico, and new occurrences of the Neoproterozoic index fossil Cloudina are reported from the underlying La Cié-nega Formation. Considered together, these fossils constrain the location of the Ediacaran ⁄ Cambrian boundary in Mexico. The suite of fossils in this sequence is important because it provides an independent biostratigraphic datum for constraining the position of Laurentia during the onset of metazoan diversification, for testing proposed lithostratigraphic correlations among western North American Neoproterozoic-Cambrian successions, and for testing regional tectonic paradigms such as the Mojave-Sonora Megashear hypothesis.

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