A potential GSSP for the base of the uppermost Cambrian stage, coinciding with the first appearance of <i>Lotagnostus americanus</i> at Wa'ergang, Hunan, China

Shanchi, Peng; Babcock, Loren E.; Zhu, Xiwen; Zuo, Jian‐Ping; Dai, Tao

doi:10.1080/11035897.2013.865666

Cited by 20 publications

(26 citation statements)

References 13 publications

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“…1, for zonal nomenclature). The occurrence of Lotagnostus is significant because this genus is under consideration as an index for the base of the youngest ‘Stage 10’ Cambrian deposits (Peng et al 2013); our collections amplify recent objections (Westrop, Adrain & Landing, 2011) to the use of species of Lotagnostus as global biostratigraphic indices.…”

Section: Geological Settingmentioning

confidence: 71%

Late Cambrian (middle Furongian) shallow-marine dysoxic mudstone with calcrete and brachiopod–olenid–Lotagnostusfaunas in Avalonian Cape Breton Island, Nova Scotia

Landing

Westrop

2015

Geol. Mag.

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The common belief that organic-rich mudstones formed in quiescent, distal settings is further weakened by study of an upper Cambrian (Leptoplastus – lower Peltura superzones) succession in the Chesley Drive Group in Avalonian Cape Breton Island that is comparable to Alum Shale successions in Baltica. Dramatic sea-level (likely eustatic) changes are now recognized by punctuation of deposition of shallow, wave-influenced black mudstone with brachiopod (Orusia lenticularis) and olenid trilobite-bearing limestones by offlap and formation of a subaerially cemented calcrete-clast conglomerate. Subaerial exposure was followed by transgression and accumulation of clastic pyrite sand and phosphatic granules with Leptoplastus Superzone (L. ovatus Zone) trilobite sclerites. Dynamic processes are shown by wave ripples in the mudstone and limestone, sorting and winnowing of fossil rudstones, and pre-compactional fracture of the conglomerate and rudstones. Orusia rudstones in the succession below the conglomerate are regarded as analogues of Eoorthis and Billingsella rudstones in the ‘biomere’ extinction intervals of the Laurentian basal Sunwaptan. The lowest Orusia-rich beds are no older than the P. spinulosa Zone but, as elsewhere in Avalonia, they range into the higher Leptoplastus (Cape Breton) and even the Peltura (Britain, New Brunswick) superzones. Rare agnostoid sclerites in lower Peltura Superzone (Ctenopyge tumida Zone) olenid rudstone resemble those traditionally assigned to Lotagnostus trisectus in Avalonian Britain and Sweden, and are distinct from Laurentian L. americanus. An L. americanus Zone cannot be identified in Avalonia or Baltica, and the first appearance datum (FAD) of purported ‘L. americanus’ is not suitable as a standard for the base of the highest Cambrian stage.

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Section: Geological Settingmentioning

confidence: 71%

Late Cambrian (middle Furongian) shallow-marine dysoxic mudstone with calcrete and brachiopod–olenid–Lotagnostusfaunas in Avalonian Cape Breton Island, Nova Scotia

Landing

Westrop

2015

Geol. Mag.

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“…Thus, this volcanic ash lies well above the base of Stage 10 with a base defined at the lowest occurrence of agnostoids termed Lotagnostus americanus in east Asia or Baltica (Peng et al, 2013(Peng et al, , 2015. Alternatively, this ash would lie just below a Stage 10 with its base defined at the lowest occurrence of Eoconodontus notchpeakensis (e.g., , see correlations in Westrop et al, 2011) (Fig.…”

Section: Figure 1 Terminal Cambrian and Earliest Ordovician Geochronomentioning

confidence: 96%

“…Informal Cambrian Stage 10 (e.g., Peng et al, 2013), or the formally proposed Lawsonian Stage (Landing et al, 2010Miller et al, 2011), comprises the highest part of the Cambrian System (Fig. 1).…”

Section: Late Late Cambrian Datementioning

confidence: 99%

“…Subsequently, L. trisectus (Salter) was synonymized with L. americanus (Billings) by Peng and Babcock (2005). Thus, the lowest occurrence of a seemingly morphologically plastic agnostoid arthropod termed Lotagnostus americanus by some workers has been proposed for the base of Stage 10 (e.g., Peng and Babcock, 2005;Peng et al, 2013Peng et al, , 2015; compare…”

Section: Late Late Cambrian Datementioning

confidence: 99%

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Improved Geochronologic Accuracy and Precision for the ICS Chronostratigraphic Charts: Examples from the late Cambrian–Early Ordovician

et al. 2015

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The utility of ICS International Chronostratigraphic Charts (ICS Charts) relies on the accuracy and precision of reported geochronologic dates and their relationship to the bases of global chronostratigraphic units. However, an examination of some early Paleozoic dates (i.e., Cambrian-Ordovician boundary and lowest Ordovician) on the ICS Charts shows that they differ from originally reported and late recalculated dates. Thus, they record a numerical precision that differs from these revised dates. The dates assigned to the bases of formal early Paleozoic chronostratigraphic units may be interpreted by the lay reader as precise determinations, although they are almost all estimates based on dated horizons that stratigraphically bracket a chronostratigraphic unit's base. The bases of informal Cambrian chronostratigraphic units (e.g., Stage 10, ~489.5 Ma) are also assigned relatively precise ages although consensus does not exist on the horizon that should define an informal unit's base, and several alternative GSSP horizons with differing ages may exist. The uncertainties of the ICS Chart's dates on stage bases within the traditional Upper Cambrian are so great that the tilde (e.g., "~500.5") indicating "about" might be replaced by question marks or an abbreviation for "estimated." A preferred alternative is to replace the age estimates on the bases of informal and almost all formal chronostratigraphic divisions in the Phanerozoic with precise dates that bracket the bases of the divisions. The ICS Chart should include (perhaps on-line) brief discussions on and references to the history and procedures of age determination, accuracy, and precision for each dated horizon. An even more accurate, precise, and informative ICS Chart would result from review by a new ICS subcommission on geochronology. The subcommission could evaluate proposed dates for the ICS Chart for accuracy, precision, and suitability for determining/bracketing the ages of chronostratigraphic unit bases and provide updated reviews of the procedures used to determine all ICS Chart dates.

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“…The Wa'ergang section in South China is one of the most continuous successions spanning the Cambrian Furongian Series (Peng, 1990 a , b , 1992; Lin, 1991; Peng et al 2001, 2014). Studies on lithology and biostratigraphy have been intensely performed on the Wa'ergang section (Peng, 1984, 1987, 1990 a , 1992; Lin, 1991; Peng et al 2001).…”

Section: Introductionmentioning

confidence: 99%

High-resolution C-isotope chemostratigraphy of the uppermost Cambrian stage (Stage 10) in South China: implications for defining the base of Stage 10 and palaeoenvironmental change

Zhang

Chen

et al. 2017

Geol. Mag.

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The Wa'ergang section in South China has been proposed as a potential Global Stratotype Section and Point (GSSP) for the base of Stage 10, the uppermost stage of the Cambrian System. In this study, high-resolution C-isotopic compositions are reported and we identified three large negative δ13C excursions, namely N1, N2 and N3, at Wa'ergang. The N1 is located just above the First Appearance Datum (FAD) of Lotagnostus americanus, corresponding to the possible base of the Proconodontus posterocostatus conodont Zone. The N2 was identified within the Micragnostus chuishuensis trilobite Zone and the Proconodontus muelleri conodont Zone. The N3 is located in the lowermost part of the Leiagnostus cf. bexelli – Archaeuloma taoyuanense trilobite Zone or Eoconodontus conodont Zone. The N1 and N2 can be correlated with the negative δ13C excursions preceding the Top of Cambrian Carbon Isotope Excursion (TOCE) observed globally. The N3 can be correlated with the TOCE or the HEllnmaria–Red Tops Boundary (HERB) Event. The inter-basinal correlation of N1 and L. americanus strongly supports that the base of Stage 10 may be best defined by the FAD of L. americanus. We also used a box model to quantitatively explore the genesis of the negative δ13C excursions from South China. Our numerical simulations suggest that weathering of the organic-rich sediments on the platform, probably driven by intermittent sea level fall and/or the oxygenation of the Dissolved Organic Carbon (DOC) reservoir in seawater, may have contributed to the generation of the negative δ13C excursions observed in the Stage 10 at Wa'ergang in South China.

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A potential GSSP for the base of the uppermost Cambrian stage, coinciding with the first appearance of Lotagnostus americanus at Wa'ergang, Hunan, China

Cited by 20 publications

References 13 publications

Late Cambrian (middle Furongian) shallow-marine dysoxic mudstone with calcrete and brachiopod–olenid–Lotagnostusfaunas in Avalonian Cape Breton Island, Nova Scotia

Late Cambrian (middle Furongian) shallow-marine dysoxic mudstone with calcrete and brachiopod–olenid–Lotagnostusfaunas in Avalonian Cape Breton Island, Nova Scotia

Improved Geochronologic Accuracy and Precision for the ICS Chronostratigraphic Charts: Examples from the late Cambrian–Early Ordovician

High-resolution C-isotope chemostratigraphy of the uppermost Cambrian stage (Stage 10) in South China: implications for defining the base of Stage 10 and palaeoenvironmental change

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