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Acritarchs from the Hanford Brook Formation, New Brunswick, Canada: new biochronological constraints on the Protolenus elegans Zone and the Cambrian Series 2–3 transition

Published online by Cambridge University Press:  27 April 2016

TEODORO PALACIOS ,
SÖREN JENSEN ,
SANDRA M. BARR ,
CHRIS E. WHITE  and
RANDALL F. MILLER
TEODORO PALACIOS*
Affiliation:
Área de Paleontología, Facultad de Ciencias, University of Extremadura, 06006 Badajoz, Spain
SÖREN JENSEN
Affiliation:
Área de Paleontología, Facultad de Ciencias, University of Extremadura, 06006 Badajoz, Spain
SANDRA M. BARR
Affiliation:
Department of Earth & Environmental Science, Acadia University, Wolfville, NS, B4P 2R6, Canada
CHRIS E. WHITE
Affiliation:
Nova Scotia Department of Natural Resources, Halifax, NS, B3J 2T9, Canada
RANDALL F. MILLER
Affiliation:
New Brunswick Museum, 277 Douglas Avenue, Saint John, New Brunswick, E2K 1E5, Canada
*
†Author for correspondence: medrano@unex.es
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Abstract

Diverse and well-preserved acritarchs are reported from the type section of the Cambrian Hanford Brook Formation at Hanford Brook, southern New Brunswick. This section fills an important gap in acritarch studies by providing the first detailed picture of changing acritarch associations close to the traditional lower–middle Cambrian boundary in Avalonia. Acritarchs from the St Martins Member, at the base of the succession, include Skiagia ciliosa, Heliosphaeridium notatum, H. longum and Liepaina plana and suggest attribution to Cambrian Stage 4. Acritarchs from the Somerset Street Member, in the middle of the formation, include Eliasum llaniscum and Comasphaeridium silesiense. This information adds new biochronological context to an ash bed in the Somerset Street Member previously dated as c. 510 Ma or 508 Ma, and to the endemic trilobites from the same member, including Protolenus elegans. It also places absolute ages on the basal range of stratigraphically important acritarchs. Both the acritarch assemblage and the radiometric age are consistent with a position very close to the traditional lower–middle Cambrian transition and likely within Cambrian Stage 5. Acritarchs from the Long Island Member, at the top of the succession, include additional taxa demonstrating assignment to Cambrian Stage 5. Both the Somerset Street and Long Island members probably correlate with the Morocconus notabilis Zone. The new acritarch species Retisphaeridium striatum Palacios is described. New data are presented on acritarchs from the upper part of the Hell's Mouth Formation, Wales, and correlation proposed with the Long Island Member.

Keywords

New BrunswickWalesacritarchsmiddle CambrianCambrian Series 3
Type
Original Articles
Information
Geological Magazine , Volume 154 , Issue 3 , May 2017 , pp. 571 - 590
Copyright
Copyright © Cambridge University Press 2016 

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