Early (Series 2) Cambrian archaeocyathan reefs of southern Labrador as a locus for skeletal carbonate production





Sara B. Pruss [spruss@smith.edu] Hannah Clemente [hannah.cle@gmail.com] Department of Geosciences, Smith College, Northampton, MA 01063; Marc Laflamme [laflammem@si.edu], Department of Paleobiology, Smithsonian Institution, Washington, DC 20560-0121, USA; manuscript received on 25/7/2011; manuscript accepted on 16/9/2011.


Pruss, S.B., Clemente, H. & Laflamme, M. 2012: Early (Series 2) Cambrian archaeocyathan reefs of southern Labrador as a locus for skeletal carbonate production. Lethaia, Vol. 45, pp. 401–410.

Archaeocyathan reefs, the first reefs produced by animals, are prominent, global features of early Cambrian successions. However, microbialites – the dominant reef components of the Proterozoic – were still abundant in most archaeocyathan reefs. Although such reefs were a locus for carbonate production, it is unclear how much carbonate was produced skeletally. This analysis of well-known early Cambrian archaeocyathan patch reefs of the Forteau Formation, southern Labrador, demonstrates that skeletal carbonate was abundantly produced in these archaeocyathan reefs, although only about half was produced by archaeocyathans. Trilobites, echinoderms and brachiopods contributed substantially to the total carbonate budget, particularly in grainstone facies flanking the reefs. Through point count analysis of samples collected from the reef core and flanking grainstones, it can be demonstrated that skeletal material was most abundant in grainstone facies, where animals such as trilobites and echinoderms contributed significantly to carbonate production. In contrast, microbial fabrics were more abundant than skeletal fabrics in the reef core, although archaeocyathan material was more abundant than other skeletal debris. Similar to modern reefs, these reefs created a variety of habitats that allowed for the proliferation of skeletal organisms living on and around the reef, thereby promoting skeletal carbonate production through ecosystem engineering. □Archaeocyatha, bioherms, carbonates, calcification, point count analysis