Comparison between ground and airborne EM data in mapping acid sulphate soils and sulphide bearing clays in the river Kyronjoki valley, Western Finland

The acid sulphate soils, along the coastal plains in westem Finland, originate from the sulphide rich clays and silts that deposited during earlier, more extensive phase of the Baltic Sea. Conditions favorable for sulphide formation existed in shallow coastal bays where decomposing of organic matter resulted occasionally reducing conditions.