Biozonation of the furongian (upper Cambrian) alum shale formation at Hunneberg, Sweden

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The Furongian Alum Shale at Nygård, Hunneberg, Sweden, has been sampled for trilobites.
The section is ≥12.20 m thick and comprises a relatively thick Olenus superzone, overlain by more
condensed Parabolina, Leptoplastus, Protopeltura and Peltura superzones. The section is truncated low
in the Peltura superzone, presumably due to late Furongian uplift. The internal zonation of the sparsely
fossiliferous Olenus superzone is unsettled. Above that level, the Parabolina spinulosa, Leptoplastus
crassicornis–Leptoplastus angustatus, Sphaerophthalmus flagellifer, Ctenopyge similis, Ctenopyge
spectabilis, Ctenopyge tumida and Ctenopyge bisulcata zones are documented. The C. similis–
C. spectabilis zonal interval yielded a lower faunal assemblage with Ctenopyge (Mesoctenopyge) erecta,
Sphaeropthalmus modestus and Ctenopyge (M.) spectabilis and an upper assemblage with Ctenopyge
(M.) similis, Sphaeropthalmus angustus and Protopeltura planicauda. Hence, the FAD’s of C. (M.) similis
and C. (M.) spectabilis are opposite of the previously described pattern. We informally refer to the lower
assemblage as the S. modestus biozone and to the upper assemblage as the S. angustus biozone (believed
to be equivalent to the C. similis and C. spectabilis chronozones, respectively). It is possible that the true
range of the rare species C. (M.) similis has to date escaped recognition. Alternatively, if the existing
chronozonation is correct, this implies reworking and the discussed interval at Nygård must in that case
represent the C. spectabilis Zone. Ctenopyge (Ctenopyge) bisulcata, C. (M.) similis, C. (M.) spectabilis,
L. angustatus, L. crassicornis, Leptoplastus paucisegmentatus?, Peltura scarabaeoides scarabaeoides,
Peltura planicauda, Sphaerophthalmus alatus, Sphaerophthalmus drytonensis, S. modestus, Triangulopyge
humilis and Triangulopyge majusculus have not previously been reported from the locality.
Original languageEnglish
Issue number4
Pages (from-to)467-489
Number of pages23
Publication statusPublished - 2016

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