Intercontinental, trilobite-based correlation of the Moroccan early Middle Cambrian

Abstract

Refined correlations of Lower-Middle Cambrian boundary strata and Middle Cambrian strata between Cambrian paleocontinents require an improved understanding of local stratigraphic ranges of well-defined trilobite genera and species. The conventional definition of the base of the Middle Cambrian in Spain (base of Acadoparadoxides mureroensis Zone) has led to problems even when correlations into other West Gondwanan regions (i.e., Moroccan) are attempted because Paradoxides (Acadoparadoxides) mureroensis and protolenid species from immediately underlying strata have been regularly misidentified. The A. mureroensis Zone is shown to correlate into strata above the base of the Moroccan Middle Cambrian, and paradoxidid trilobites, a guide to the Middle Cambrian, have a lower occurrence in Morocco. These correlations are strengthened by a reevaluation of higher Middle Cambrian trilobite genera and species in Morocco and their use in correlation into Spain and Baltica. Two new genera and eight new species of Middle Cambrian trilobites from the Moroccan High Atlas and Anti-Atlas are proposed. They areCondylopyge eli n.sp., Schistocephalus?ornatus n.sp., Paradoxides (Acadoparadoxides) nobilis n.sp., Parasolenopleura lemdadensis n.sp., Bailiella inconspicua n.sp., Bailiella dilatata n.sp., Atopiaspis tikasraynensis n.gen. and n.sp., and Cambrophatictor cataractis n.gen. and n.sp. Gigoutella atlasensis Hupé 1953 is described in detail for the first time. Gonzaloia n.gen. (type species Calymene holometopa Angelin 1851) is based on a well-known species from the Middle Cambrian of Baltica. The occurrences of the majority of the new Moroccan taxa clearly corroborate earlier interregional and intercontinental correlations by the author and refine and modify proposals by K. Sdzuy, which were largely based on generalized taxonomic assignments of G. atlasensis and the new species S.? ornatus and P. (A.) nobilis.