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 JAMES F. MILLER, KEVIN R. EVANS, REBECCA L. FREEMAN, ROBERT L. RIPPERDAN & JOHN F. TAYLOR The name Lawsonian Stage is proposed as the highest stage of the Cambrian System (Stage 10). The base of the pro- posed Lawsonian Stage is at the First Appearance Datum (FAD) of the euconodont Eoconodontus notchpeakensis (Miller, 1969). That horizon, the base of the E. notchpeakensis Subzone of the Eoconodontus Zone, is 3 m above 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 Eoconodontus Zone is widespread in North America and occurs in Asia, Australia, Eu- rope, 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 Illaenurus trilobite Zone of western North America and within the lower part of the Saukiella junia Subzone of the Saukia 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 Billingsella and the Finkelnburgia calcitic brachiopod Zones; ranges of organophosphatic brachiopods also characterize the horizon. A high-amplitude, negative, carbon-isotope excursion, the HERB Event, occurs in the Eoconodontus notchpeakensis 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. • Key words: Cambrian, Furongian, Lawsonian, Stage 10, chronostratigraphy, conodonts, trilobites, brachiopods, carbon isotopes, HERB Event. MILLER, J.F., EVANS, K.R., FREEMAN, R.L., RIPPERDAN, R.L. & TAYLOR, J.F. 2001. 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. Bulletin of Geosciences 86(3), 595–620 (14 figures, 1 table). Czech Geological Survey, Prague. ISSN 1214-1119. Manuscript received January 1, 2011; accepted in revised form July 11, 2011; published on- line August 5, 2011; issued September 30, 2011. James F. Miller & Kevin R. Evans, Department of Geography, Geology & Planning, Missouri State University, Springfield, Missouri 65897, USA; jimmiller@missouristate.edu, kevinevans@missouristate.edu • Rebecca L. Free- man, Department of Earth & Environmental Sciences, University of Kentucky, Lexington, Kentucky 40506, USA; rebecca.freeman@uky.edu • Robert L. Ripperdan, 1417 Fairbroook Drive, Des Peres, MO 63131, USA; rob- ert.ripperdan@gmail.com • John F. Taylor, Geoscience Department, Indiana University of Pennsylvania, Indiana, Pennsylvania 15701, USA; jftaylor@.iup.edu The Subcommission on Cambrian Stratigraphy is progres- sing toward a long-term goal of dividing the Cambrian Sys- tem into four series and ten stages. The uppermost series of the Cambrian, the Furongian Series, is divided into the low- er Paibian Stage, the middle Jiangshanian Stage, and an un- named Stage 10 at the top of the Cambrian. The Subcom- mission made a decision to place the base of Stage 10 at the First Appearance Datum (FAD) of the trilobite Lotag- nostus americanus (Billings) or another fossil. At the 15 th Field Conference of the Cambrian Stage Subdivision Working Group, Landing et al. (2010) contended that the taxonomic status and global distribution of Lotagnostus americanus are too poorly understood to use that species for defining the base of Stage 10. They proposed, as a supe- rior alternative, that the FAD of the globally distributed eu- conodont Eoconodontus notchpeakensis (Miller, 1969) be used for defining the base of Stage 10. Three reports in this volume are outgrowths of the pre- sentation by Landing et al. (2010). Landing et al. (this vol- ume) document problems with using Lotagnostus 595 DOI 10.3140/bull.geosci.1255