Fifty-one kilograms of limestones and dolomites, roughly 35% from the outcrop, 8% from cores, and the remainder from glacial erratics scattered around the Åland Archipelago, have produced several thousand Ordovician conodonts. Erratic materials range in age from Arenigian (‘orthoceratite limestone’) to upper Caradocian (‘Baltic limestone’). Most of these erratics probably were derived very locally and thereby provide some additional information for geologic mapping of the adjacent floor of the Gulf of Bothnia. In situ sedimentary rocks in Lumparn Bay may be the only post-Cambrian stratiform Paleozoic deposits in Finland. Like most of the ‘Baltic limestone’ erratics, the conodont abundance in these Lumparn limestones is generally quite low, but the outcropping upper part of the more than 80 m of carbonates is quite productive and substantiates a late Caradocian (upperAmorphognathus superbusZone) age, at least in part. Its nearest age equivalents appear to be the Kullsberg and Slandrom limestones in Sweden and the Nabalan Stage in Estonia. The bulk of the samples are highly bioturbated and dolomitized micrites with few body fossils and a sparse conodont fauna dominated by distacodontids, chieflyPanderodus.Environmentally, these observations suggest deposition on a hyper- to schizohaline carbonate bank that may have been, in part at least, intertidal. Preservation of the Paleozoic section in Lumparn seems best explained by the Lumparn basin being a meteorite impact structure.