EOCENE TO MIOCENE BACK-ARC BASIN BASALTS AND ASSOCIATED ISLAND-ARC THOLEIITES FROM NORTHERN SULAWESI (INDONESIA) - IMPLICATIONS FOR THE GEODYNAMIC EVOLUTION OF THE CELEBES BASIN

Eocene BABB basalts intruded by tholeiitic and calk-alkalic island are magmatic rocks are reported from the north arm of Sulawesi (Indonesia ). Age and geochemical similarities between these basalts and those dr illed in the Celebes Sea indicate this North Sulawesi volcanic are was built on the same oceanic crust. The 250 late Neogene clockwise rotat ion of the north arm of Sulawesi following its collision with fragment s of Australia (Sula, Buton) is not sufficient to explain the assymetr ical magnetic anomalies in the Celebes basin. The North Sulawesi islan d arc could be interpreted as having progressively retreated northward on its own Celebes sea back arc basin, during an episode of Palaeogen e-early Neogene tectonic erosion along the trench.