Acritarch assemblages from the Lower Silurian (Llandovery-Wenlock) in the Grötlingboborrningen 1 core, Gotland, Sweden

Nine collections, totally about 100 specimens, from Llandoverian and lowermost Wenlockian in the Grötlingboborrningen 1 core yielded 19 genera and 30 species of well-preserved acritarch taxa, obtaining a TAI-value of 1+. A comparison with the Närborrningen 1 core indicate an extended range for two acritarch species, as well as for the four species which have an earlier record in the Grötlingboborrningen 1 core. The major change of the acritarch assemblages is at the boundary of the Pterospathodus celloni and P. amorphognathoides conodont zones. Another change is within the P. amorphognathoides zone, and at the Ireviken Event. It is suggested that conodonts and acritarchs responded almost similarly to changing environmental conditions in early Silurian. Keywords: Acritarch assemblages, Llandovery, Silurian, Grötlingboborrningen 1, Gotland, Sweden