Observation of ferromanganese deposit in the Gulf of Bothnia, Baltic Sea

The present experimental study is based on evidence obtained on land showing that in areas covered by ancient continental ice the drift is to a large extent of local origin so that the quality of the rock ground is determinable from the composition of the drift with a great degree of probability. A geological map based on the bottom sampIes has accordingly been sketched of the Bothnian Sea area. Echo sounding has been made use of in determining the quality of the bottom at the sample points as well as for the interpretation of the morphological picture of the sea bottom. In order to obtain a uniform interpretation basis as weIl as a statistically adequate amount of stone grains from each sampIe, 2-16 mm has been chosen as the grain size for the pebble counts.