Age of the Kalana Lagerstätte, early Silurian, Estonia

The Kalana quarry in central Estonia is known for its exceptionally well-preserved non-calcified algal and other fossils. The interval with the fossil Konservat Lagerstätte in the Kalana section has previously been tentatively dated as early Aeronian. Recent findings of graptolites now enable more precise dating of these beds. The strata yielding the Lagerstätte are not older than the mid-Aeronian and correspond to the Pribylograptus leptotheca graptolite Biozone. In terms of conodont biostratigraphy they correlate with the middle of the Pranognathus tenuis conodont Biozone. It has also become evident that the uppermost Jõgeva Beds of the Nurmekund Formation, and probably also the uppermost Ikla Member of the Saarde Formation, are younger than previously thought and correlate with the Pribylograptus leptotheca graptolite Biozone. Our data additionally indicate that the conodont genus Aulacognathus had appeared by the mid-Aeronian.