Proposed stratotype for the base of the Lawsonian Stage (Cambrian Stage 10) at the First Appearance Datum of Eoconodontus notchpeakensis (Miller) in the House Range, Utah, USA

Abstract

The name Lawsonian Stage is proposed as the highest stage of the Cambrian System (Stage 10). The base of the proposed Lawsonian Stage is at the First Appearance Datum (FAD) of the euconodont <i>Eoconodontus notchpeakensis </i>(Miller, 1969). That horizon, the base of the <i>E. notchpeakensis </i>Subzone of the <i>Eoconodontus </i>Zone, is 3mabove the base of the Red Tops Member of the Notch Peak Formation at the Steamboat Pass section in the House Range, western Utah, USA. The conodont fauna of the <i>Eoconodontus </i>Zone is widespread in North America and occurs in Asia, Australia, Europe, and South America in facies that include cratonic nearshore sandstones, shallow and intermediate-depth platform carbonates, deep-water ramp, continental slope deposits, and deep-ocean radiolarian chert. This horizon lies at or slightly below the top of the <i>Illaenurus </i>trilobite Zone of western North America and within the lower part of the <i>Saukiella junia </i>Subzone of the <i>Saukia </i>Zone in areas east of the Rocky Mountains. These trilobite and conodont faunas can be traced into slope deposits containing cosmopolitan trilobites. The horizon is nearly coincident with the boundary between the <i>Billingsella </i>and the <i>Finkelnburgia </i>calcitic brachiopod Zones; ranges of organophosphatic brachiopods also characterize the horizon. A high-amplitude, negative, carbon-isotope excursion, the HERB Event, occurs in the <i>Eoconodontus notchpeakensis </i>Subzone. This distinctive geochemical signal is known in western Utah, Australia, China, and in poorly fossiliferous slope deposits in Newfoundland, Canada. The proposed boundary fits between two closely spaced sequence-stratigraphic boundaries described from Utah and Texas, USA

Palaeoenvironmental changes in slope carbonates across the Late Cambrian–Early Ordovician in western Newfoundland

“…Variations in eustatic sea level do not influence only the redox conditions and organic productivity but also the input of terrigenous sediments and nutrients in ocean, which is reflected in the associated changes in the concentrations of trace elements in marine sediments (e.g., Arnaboldi & Meyers, 2007;Cowan & James, 1993;Dickson, Cohen, & Coe, 2011;Kimura, Azmy, Yamamuro, Zhi-Wen, & Cizdziel, 2005;Piper & Calvert, 2009;Śliwiński et al, 2010;Wignall & Twitchett, 1996). An earlier study (Azmy, 2018) documented a noticeable negative δ 13 C carb excursion (~3‰), associated with sea-level changes (Miller et al, 2011), that peaks at the base of the Wignall & Twichett, 1996). Al and Si reflect the influence of terrestrial input in oceans (e.g., Govin et al, 2012;Zhao & Zheng, 2014).…”

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

“…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).…”

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

“…E. notchpeakensis is a long-ranging species, extending from the base of the Eoconodontus Zone through the Lower Ordovician in Utah, the USA, the "stratotype" area of the "Lawsonian Stage" (Miller 1969, Miller et al 2011) and from the base of the Eoconodontus Zone through the upper part of the Cordylodus lindstromi (Iapetognothus fluctivagus) Zone of the Lower Ordovician in northwestern Hunan (Dong et al 2004). If E. notchpeakensis were to be selected as the principal guide fossil marking the base of Cambrian Stage 10, it would range through the entire stage, as well as into the succeeding stage, series and system.…”

“…In view of this set of facts, the horizon containing the FAD of L. americanus continues to stand out as a strong option for defining the base of Cambrian Stage 10. A conodont species, Eoconodontus notchpeakensis (Miller, 1969), has been proposed as an alternative to mark the base of provisional Stage 10 Miller et al 2011).…”

“…A new global stage, the Lawsonian Stage, was proposed Miller et al 2011) with the horizon containing the FAD of E. notchpeakensis coinciding with its base. E. notchpeakensis is a long-ranging species, extending from the base of the Eoconodontus Zone through the Lower Ordovician in Utah, the USA, the "stratotype" area of the "Lawsonian Stage" (Miller 1969, Miller et al 2011) and from the base of the Eoconodontus Zone through the upper part of the Cordylodus lindstromi (Iapetognothus fluctivagus) Zone of the Lower Ordovician in northwestern Hunan (Dong et al 2004).…”