Pillow lava structures are found in the supracrustals south of Tjörn, south-western Sweden. The pillow lava grades into banded amphibolites, mostly with rapidly changing composition and some intermediate and acid intercalations. These amphibolites are part of the Stora Le-Marstrand formation, which is dominated by greywackes. Both pillow lavas and ordinary supracrustals are metamorphosed before the intrusion of the 1650 Ma Rönnäng tonalite. An island are continental margin environment of formation is suggested.