Abstract
AbstractThe Emigrant Formation at Clayton Ridge, Nevada, consists of 420 m of variably interbedded shale, siltstone, and limestone representing an outer shelf environment. It ranges in age from the youngest portion of the Dyeran Stage (Laurentian Waucoban Series; Cambrian Stage 4, Series 2) to Skullrockian Stage (Ibexian Series; Tremadocian Stage, Lower Ordovician). Consequently, it is condensed compared to other localities. For example, the age-equivalent succession in the House Range and the Wendover Range of Utah and Nevada, respectively, is seven times thicker.The 100 m thick lower limestone and siltstone member of the Emigrant Formation at Clayton Ridge ranges in age from theBolbolenellus euryparia/Nephrolenellus multinodusZone (Laurentian Dyeran Stage) to theCedaria brevifronsZone (Laurentian Marjuman Stage; Drumian Stage; this study). The 40 trilobites described herein from two closely spaced sections of the lower member belong to theGlossopleura walcotti/Ptychagnostus praecurrensZone (Laurentian Delamaran Stage; Stage 5),EhmaniellaZone (Laurentian Topazan Stage; Stage 5), andCedaria selwynitoC.brevifronszones (Laurentian Marjuman Stage; Drumian Stage) zones. The lower Emigrant Formation is <10% as thick as age-equivalent age strata elsewhere in Nevada, California, and Utah. This condensed nature of the lower Emigrant Formation began with the flooding event at the beginning of theOryctocephalus indicusbiochron and the subsequent build-ups of the thick carbonate platforms to the south and northeast.New species arePagetia aspinosa,P.claytonensis, andSyspacephalus mccollumorum.
Published Version
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