Journal of Paleontology; September 2008; v. 82; no. 5;
p. 884-905; DOI: 10.1666/07-007.1
© 2008 Paleontological Society
Faunas and Cambrian Volcanism on the Avalonian Marginal Platform, Southern New Brunswick
Ed Landing1,
Susan C. Johnson2 and
Gerd Geyer3
1 New York State Museum, Madison Avenue, Albany, New York 12230, <elanding{at}mail.nysed.gov>
2 New Brunswick Department of Natural Resources, Geological Surveys Branch, Box 5040, Sussex, New Brunswick E4E 5L2, <Susan.Johnson{at}gnb.ca>
3 Am Rubenland 17, 97084 Würzburg, Germany, <gerd.geyer{at}lfu.bayern.de>
The Cambrian inlier at Beaver Harbour, southern New Brunswick, is now confidently referred to the marginal platform of the late Proterozoic–Early Paleozoic Avalon microcontinent. The sub-trilobitic Lower Cambrian Chapel Island and Random Formations are unconformably overlain by the mafic volcanic-dominated Wade's Lane Formation (new). Late Early Cambrian trilobites and small shelly taxa in the lowest Wade's Lane demonstrate a long Random–Wade's Lane hiatus (middle Terreneuvian–early Branchian). Latest Early–middle Middle Cambrian pyroclastic volcanism produced a volcanic edifice at Beaver Harbour that is one of three known volcanic centers that extended 550 km along the northwest margin of Avalon. Middle Middle Cambrian sea-level rise, probably in the Paradoxides eteminicus Chron, mantled the extinct volcanics with gray-green mudstone and limestone of the Fossil Brook Member. Black, dysoxic mudstone of the upper Manuels River Formation (upper Middle Cambrian, P. davidis Zone) is the youngest Cambrian unit in the Beaver Harbour inlier. Lapworthella cornu (Wiman, 1903) emend., a senior synonym of the genotype L. nigra (Cobbold, 1921), Hyolithellus sinuosus Cobbold, 1921, and probably Acrothyra sera Matthew, 1902a, range through the ca. 8 m.y. of the trilobite-bearing upper Lower Cambrian, and H. sinuosus and A. sera persist into the middle Middle Cambrian. Lapworthella cornu and H. sinuosus replaced the tropical taxa L. schodackensis (Lochman, 1956) and H. micans Billings, 1872, in cool-water Avalon.
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