Preliminary paleomagnetic and rock-magnetic results from Lago Azul (Azores archipielago, Portugal)

A paleomagnetic and rock magnetic study has been carried out in 4 sediment cores collected in Lake Azul (Azores archipielago) using a gravity corer from a UWITEC raft. The cores include three main lithological units (from base to top): volcaniclastic rocks (ash and lapilli), light grey laminated mud, and poor laminated light brown mud with frequent dark layers rich in terrestrial plant debris. Accelerator mass spectrometry (AMS) 14C dates, performed on pollen-concentrates, indicate that the cores span a time interval that includes approximately the last 650 years. Rock-magnetic data allow correlation of the sedimentary sequences and a refinement of the preliminary 14C age model. Mineral magnetic measurements indicate that pseudo single-domain magnetite is the major carrier of the remanence allowing the reliable determination of the characteristic remanent magnetizations from alternating field demagnetizations and principal component analysis. The results show that the paleosecular variation (PSV) records are consistent between cores and suggest that these sediments are reliable recorders of past geomagnetic field paleosecular variations in this region.