Orthocone nautiloid orientations in Arenig and Llanvirn limestones of Öland, Sweden

Orientations of the orthocone nautiloids on twenty-three bedding planes in Arenig and Llanvirn (Ordovician) limestones on Öland are analyzed. Nine bedding planes display a bipolar orientation indicating very shallow water. The other fourteen have polymodal orientations, although uniform distributions are rejected statistically. Clusters of orthocones with abnormal distributions are very common on Oland. Experimental data suggest that the clusters are reflecting irregularities on the sea bottom, the so called neighbour effect. The distribution on either side of the flow direction is probably a combination of the neighbour effect and the particle rotation between conch and sediment. The currents in the Ordovician sea around Öland flowed south and may have paralleled the depth contours. The closest land at that time was probably to the west.