Publications

The type sections of the Gorge and overlying Highgate formations (redefined) at Highgate gorge on the Missisquoi River, northwestern Vermont, represent a condensed Upper Cambrian through Lower Ordovician ensialic continental slope package. Deposition of the Gorge Formation took place in relatively shallow water (ca. 90 m). The site of deposition lay northward of an easterly trending shelf margin considered to be an eastern continuation of the southern margin of the Ottawa-Bonnechere graben system. The sequence features three biostratigraphically resolvable disconformities marked by debris flows and a possible truncation surface. These disconformities are bracketed by 1) upper Dresbachian (Dunderbergia Zone) through middle Trempealeauan Saukiella pyrene or lower Saukiella junia Subzone faunas of the Saukia Zone, 2) middle Trempealeauan (Saukiella junia or Saukiella serotina Subzone) through lower Symphysurina Zone faunas and spanning the Cambrian-Ordovician (Olenidian-Tremadocian Series) boundary, and 3) middle Symphysurina Zone to lowest Leiostegium-Kainella (D) Zone faunas at the contact of the Gorge and Highgate formations. Conodont-based correlation of biostratigraphically problematical Hungaia trilobite assemblages at Highgate gorge indicates an upper Saukiella pyrene or lower Saukiella junia Subzone equivalency of the "lower zone" and an upper Saukiella junia or Saukiella serotina Subzone equivalency of the "main zone." Proconodontus Zone through lower Fauna B conodont faunas at Highgate gorge have an open oceanic character, lack a number of genera and species characteristic of the inner carbonate platform, have diverse and abundant proto- and paraconodonts, and low local range zones for Oneotodus? nakamurai Nogami, Cordylodus proavus Müller s.f., and C. oklahomensis Müller s.f. Evidence exists suggesting that several euconodont species evolved in outer shelf or slope facies and have an early first occurrence there. The lowest occurrence of C. proavus s.f. is demonstrated to be significantly diachronous in the Upper Cambrian, is significantly older than the base of the Tremadocian, and does not supply a criterion for correlation of the base of the Corylodus proavus Zone away from the North American carbonate platform. Thirty-six conodont taxa are described: Eoconodontus (Eoconodontus) alisonae n. subgen., n. sp., Hirsutodontus n. sp., and Drepanoistodus? cf. D. inaequalis (Pander) are documented. Nogamiconus Miller, 1980, represents elements of multielement Coelocerodontus Ethington, 1959, and, probably, Prosagittodontus Müller and Nogami, 1971, and is not considered to be a valid genus. Prodistacodus An, 1982, may be based on an element of Coelocerodontus cambricus (Nogami). Monocostodus Miller, 1980, and Teridontus Miller, 1980, can be regarded as congeneric and are referred to Oneotodus? Lindstrom, 1955.