• Medientyp: E-Artikel
  • Titel: Lower Cambrian (Branchian) trilobites and biostratigraphy of the Hanford Brook Formation, southern New Brunswick
  • Beteiligte: Westrop, Stephen R.; Landing, Ed
  • Erschienen: Cambridge University Press (CUP), 2000
  • Erschienen in: Journal of Paleontology
  • Umfang: 858-878
  • Sprache: Englisch
  • DOI: 10.1017/s0022336000033060
  • ISSN: 0022-3360; 1937-2337
  • Schlagwörter: Paleontology
  • Zusammenfassung: <jats:p>The Hanford Brook Formation, one of the classic Cambrian units of Avalonian North America, contains at least eight species of endemic trilobites, including <jats:italic>Berabichia milleri</jats:italic> Westrop n. sp., that are assigned to seven genera. The vertical succession of faunas is far more complex than has been recognized previously, with each member containing a lithofacies-specific assemblage. These are, in ascending order: a bradoriid-linguloid Association without trilobites in the nearshore St. Martin's Member, a <jats:italic>Protolenus</jats:italic> Association in dysaerobic siltstones and sandstones of the Somerset Street Member, and a <jats:italic>Kingaspidoides-Berabichia</jats:italic> Association in hummocky cross-stratified sandstones of the Long Island Member that overlie a parasequence boundary at Hanford Brook. Due to the breakdown of biogeographic barriers in the late Early Cambrian, two new species-based zones, the <jats:italic>Protolenus elegans</jats:italic> and <jats:italic>Kingaspidoides</jats:italic> cf. <jats:italic>obliquoculatus</jats:italic> zones, share trilobite genera with the Tissafinian Stage of Morocco. This generic similarity has been the basis for correlation of this upper Lower Cambrian interval on the Avalon continent with the West Gondwanan lowest Middle Cambrian. However, the clear facies control on the occurrence of genera in the Hanford Brook Formation and the presence of an abrupt faunal break and unconformity at the base of the Tissafinian in Morocco makes this correlation questionable. The Hanford Brook Formation may represent a late Early Cambrian interval unknown in Gondwana. Sequence-stratigraphic criteria even raise the possibility that the <jats:italic>Protolenus</jats:italic> Association is the biofacies equivalent of <jats:italic>Callavia broeggeri</jats:italic> Zone faunas of the Brigus Formation of Newfoundland, Nova Scotia and Massachusetts.</jats:p>
  • Beschreibung: <jats:p>The Hanford Brook Formation, one of the classic Cambrian units of Avalonian North America, contains at least eight species of endemic trilobites, including <jats:italic>Berabichia milleri</jats:italic> Westrop n. sp., that are assigned to seven genera. The vertical succession of faunas is far more complex than has been recognized previously, with each member containing a lithofacies-specific assemblage. These are, in ascending order: a bradoriid-linguloid Association without trilobites in the nearshore St. Martin's Member, a <jats:italic>Protolenus</jats:italic> Association in dysaerobic siltstones and sandstones of the Somerset Street Member, and a <jats:italic>Kingaspidoides-Berabichia</jats:italic> Association in hummocky cross-stratified sandstones of the Long Island Member that overlie a parasequence boundary at Hanford Brook. Due to the breakdown of biogeographic barriers in the late Early Cambrian, two new species-based zones, the <jats:italic>Protolenus elegans</jats:italic> and <jats:italic>Kingaspidoides</jats:italic> cf. <jats:italic>obliquoculatus</jats:italic> zones, share trilobite genera with the Tissafinian Stage of Morocco. This generic similarity has been the basis for correlation of this upper Lower Cambrian interval on the Avalon continent with the West Gondwanan lowest Middle Cambrian. However, the clear facies control on the occurrence of genera in the Hanford Brook Formation and the presence of an abrupt faunal break and unconformity at the base of the Tissafinian in Morocco makes this correlation questionable. The Hanford Brook Formation may represent a late Early Cambrian interval unknown in Gondwana. Sequence-stratigraphic criteria even raise the possibility that the <jats:italic>Protolenus</jats:italic> Association is the biofacies equivalent of <jats:italic>Callavia broeggeri</jats:italic> Zone faunas of the Brigus Formation of Newfoundland, Nova Scotia and Massachusetts.</jats:p>
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