Stratigraphically significant acritarchs in uppermost Cambrian to basal ordovician strata of northwestern Algeria

Vecoli, M.; Playford, G.

Grana 36(1): 17-28


ISSN/ISBN: 0017-3134
DOI: 10.1080/00173139709362585
Accession: 009461411

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In Cambro-Ordovician transitional beds of the Hassi R'mel area, northwestern Algeria, three stratigraphically successive acritarch assemblage zones can be recognized: HM/A (uppermost Cambrian), HM/B (basal Tremadoc), and HM/C (lower Tremadoc; with associated graptolites of the Rhabdinopora flabelliformis sensu lato group). Thus, the boundary between assemblages HM/A and HM/B is considered to approximate to the Cambrian-Ordovician boundary in the study area. Six morphologically distinctive acritarch species that facilitate recognition of zonal boundaries are described. One genus and four species are newly instituted: Phenacoon imperfectum gen. et sp. nov., Impluviculus araneus sp. nov., Ladogella saharica sp. nov., and Multiplicisphaeridium attenuatum sp. nov. Revised circumscriptions of two other species-Acanthodiacrodium baculatum and Baltisphaeridium verutum-incorporate morphological details not previously available. P. imperfectum and L. saharica are abundant at the top of assemblage zone HM/A; A. baculatum characterizes the base of assemblage zone HM/B: and B. verutum, I. araneus, and M. attenuatum are characteristic components of the lower part of HM/C assemblage zone.