ABSTRACT

A sequence of about 1,500 feet of limestone and shale, apparently gradational from Silurian into Devonian and representing Upper Silurian (Ludlovian) through upper Lower Devonian (Emsian), is present at the headwaters of Royal Creek, Yukon. Lower Devonian fossils which are abundant in parts of the sequence show affinities on the one hand to those of Nevada, and on the other hand to those of the Bohemia-Urals regions of the Old World. The Royal Creek succession falls into six more or less natural faunal units, each with a distinctive fauna, or with unique faunal elements, one or more of which is used to name the unit. The faunal units and their proposed ages are as follows: Monograptus nilssoni unit: Lower Ludlovian; Atrypella tenuis unit: possibly Middle or Upper Ludlovian; Gypidula cf. pelagica unit: Gedinnian; Spirigerina unit: Siegenian; Gypidula sp. 1--Biconostrophia unit, which falls within the Monograptus yukonensis Zone: Upper Siegenian and Lower Emsian; Nymphorhynchia pseudolivonica-Sieberella unit: Emsian.