II.—The Lower Ordovician Rocks of Scandinavia, with a Comparison of British and Scandinavian Tremadoc and Arenig Rocks

Extract

Considering now the details of the various districts, we notice that in South Öland the basal beds are shaly and conglomeratic; the higher part is calcareous, and by increase in the proportion of matrix passes into a creamy-white limestone which is wonderfully fossiliferous (0 1 and C). The highest beds are again glauconitic, soft, and shaly. Northward the proportion of calcareous material diminishes, and a band of shale with Shumardia, whose lithology and fossil content agree with that of the Ottenby Ceratopyge shales below the unconformity, is interstratified with the limestone. This bed is quite inconstant, but in Central Öland another shale band containing Euloma occurs low down in the limestone. Beyond Borgholm (05 and 06) all limestone disappears, and only glauconitic shale separates the alternating of Dictyonema shale and Obolus conglomerate from the Orthoceras limestone above. In Central Öland the glauconite shales and Ceratopygekalk attain their maximum thickness of nearly seven feet, but in the north are again reduced to little more than one foot.