Proposal of a reference section and point for the Cambrian Series 2–3 boundary in the Mediterranean subprovince in Murero (NE Spain) and its intercontinental correlation. (4th December 2011)

• Record Type: Journal Article
• Authors: Gozalo, Rodolfo; Álvarez, María Eugenia Dies; Vintaned, José Antonio Gámez; Zhuravlev, Andrey Yu.; Bauluz, Blanca; Subías, Ignacio; Chirivella Martorell, Juan B.; Mayoral, Eduardo; Gursky, Hans‐Jürgen; Andrés, José Antonio; Liñán, Eladio; Albanesi, Guillermo L.; Ortega, Gladys
• Is Part Of: Geological journal. Volume 48:Number 2/3(2013)
• Page Start: 142
• Page End: 155
• Publication Date: 2011-12-04
• Subjects: Geology -- Periodicals; 551
• DOI: 10.1002/gj.1330
• Languages: English
• ISSNs: 0072-1050

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p>The classical lower‐middle Cambrian boundary is approximately equivalent with the boundary of the Cambrian Series 2 and 3, which is now in the process of definition by the International Subcommission on Cambrian Stratigraphy. Currently, there are two oryctocephalid trilobite species first appearance data (FAD) that are suggested as possible markers of this level: <italic>Ovatoryctocara granulata</italic> Tchernysheva, 1962 and <italic>Oryctocephalus indicus</italic> (Reed, 1910), respectively. Until now neither of these two species has been recorded in the Mediterranean subprovince or Baltica. As a result, in these regions a level potentially correlating with either the FAD of <italic>Ovatoryctocara granulata</italic> or <italic>Oryctocephalus indicus</italic> has to be located using the available bio‐, isotope‐, and event‐stratigraphy data.</p> <p>Carbon isotope signatures reveal global oceanic perturbations adjacent to the Cambrian Series 2 and Series 3 (former lower‐middle Cambrian) boundary. This event, first called the Valdemiedes Event (it was defined in Murero, NE Spain; Liñán <italic>et al</italic>., 1993a), caused a noticeable extinction of trilobites, mostly olenellids and protolenids (which were replaced in some regions by paradoxidids), as well as an almost complete extermination of some other early Cambrian marine animals. Both isotope and palaeontological evidence show that the disappearance of olenellids in Laurentia, protolenids in Siberia and the appearance of the first <italic>Acadoparadoxides</italic> in Western Gondwana, Baltica, Avalonia, and Siberia, which was formerly thought to be a series of diachronous regional perturbations, were nearly contemporaneous events. Features of a global ecological crisis and faunal replacement being taken together with a pronounced global δ<sup>13</sup>C<sub>org</sub> negative excursion would serve as the best indicator of the lower boundary of the Cambrian Series 3 and Stage 5 in the Mediterranean subprovince and is correlatable with the <italic>Ovatoryctocara granulata</italic> FAD. Another δ<sup>13</sup>C<sub>org</sub> negative excursion followed by a positive shift occurs at a slightly younger level, which coincides with a transgression maximum and roughly is coeval with the <italic>Oryctocephalus indicus</italic> FAD, also proposed as a possible base of the Cambrian Series 3. Copyright © 2011 John Wiley & Sons, Ltd.</p> </abstract>