| Abstract |
Restudy of all available trilobites from the Atlas ranges, southern Morocco, allows an evaluation of the biostratigraphy of Cambrian Stage 4. Significant contrasts occur in species ranges between different sections and areas, which are explained by lateral changes in depositional environments, sampling biases, and disparities in preservational conditions. A refined biostratigraphic scheme for the Moroccan Atlas regions includes a vertical succession of trilobite assemblages: (1) an Antatlasia–Hebediscus assemblage of the Antatlasia hollardi–A. guttapluviae zones; (2) Bondonella–Neltneria–Marsaisia assemblage of the A. guttapluviae–lower Sectigena zones; (3) Longianda–Saukianda–Gigantopygus assemblage of upper A. guttapluviae–lower Sectigena zones; (4) Triangulaspis zirarii–Serrodiscus coloi–Brevitermierella–Andalusiana assemblage of the upper Sectigena Zone; and (5) Protolenus–Hamatolenus–Morocconus assemblages of the Hupeolenus and M. notabilis zones. Improved trilobite species ranges in the Atlas ranges contribute to a more detailed and precise correlation to other regions of West Gondwana, particularly the Iberian Peninsula, as well as allow a more detailed interregional correlation and provide the basis for a global Cambrian Stage 4 concept. This stratigraphic interval shows four “faunal bands” recognisable on several palaeocontinents by key trilobite genera and species for the middle and upper part of Stage 4. However, the lower part of Stage 4 is poorly defined and not precisely correlatable by trilobites globally. New proposed taxa are Atops antiatlasensis n. sp. and Imighzeria silena n. gen., n. sp. |
