a1 School of Earth and Environmental Sciences, University of Portsmouth, Burnaby Road, Portsmouth PO1 3QL, UK
Charts are presented showing the correlation of graptolite biozonations for the Lower Ordovician to Lower Devonian, i.e. for the entire stratigraphical range of the planktonic graptoloid graptolites. Regions chosen are those for which the most detailed biostratigraphical studies have been undertaken. For Baltica, average graptolite zone (chron) duration appears to vary from c. 300000 years (Ludlow Epoch) to 2.4 Ma (Lochkovian Epoch).
(Received November 30 2010)
(Accepted April 05 2011)
(Online publication June 10 2011)