As defined by Churkin and Carter (1996), unit consists of “* * * two more-or-less pure limestone members separated by a siltstone member of calcareous siltstone and sandy limestone.” Lower limestone is medium-dark-gray, medium-gray-weathering, well-bedded, thick- to thin-bedded, and has orange-weathering silty beds in upper half of member that form less than 50 percent of section, which is about 100 m thick. Siltstone member is about 200 m thick and is composed of very thin-bedded, cross-laminated, yellowish-orange-weathering, silty and sandy limestone and calcareous siltstone which contain occasional 3-m-thick pure limestone interbeds and rare argillaceous beds. Uppermost member is massive, indistinctly bedded to laminated, medium-dark-gray, finely crystalline limestone more than 100 m thick and contains minor lighter gray dolostone (Churkin and Carter, 1996). Unit is known from the McGrath quadrangle and correlative rocks are found in the Lime Hills quadrangle; the unit undoubtedly extends into the Talkeetna quadrangle, where is it included in unit DCd. Bundtzen and others (1997a) reported late Silurian to Late Devonian conodonts from unit, based on a report in Bundtzen and others (1994) where the reported conodont has an age range of middle Silurian to Early Devonian. Churkin and Carter (1996) interpreted the lower contact of the Barren Ridge Limestone with the underlying Terra Cotta Sandstone as a thrust fault and noted that rocks of latest Silurian age are not present