Late Ordovician–Early Silurian (Ashgillian–Llandovery) sea level curve derived from conodont community analysis, Anticosti Island, Québec

Abstract

Earlier workers have established sea level curves for the Ashgillian–Llandovery sequence on Anticosti Island, Québec, Canada, based on sedimentology and on brachiopod and reef communities. The complete Anticosti sequence has been collected for conodonts to provide a database of over 77 600 conodonts derived from 272 samples through the 800–1100 m sequence. This paper uses a statistical analysis of the database to establish the pattern of conodont communities and their interpreted water depths. This allows the establishment of a eustatic sea level curve for the sequence. This curve is in general agreement with those of the earlier workers, but is more detailed and better constrained stratigraphically given the large sampling program. The curve reflects more oscillating sea level changes for the whole sequence than those constructed earlier, and different water depths for certain intervals from those established earlier. The curve is valuable given that the Anticosti sequence is one of the most complete in the world for this interval, and its divergence from global eustatic curves for this interval is noted.