Optical luminescence dating of uplifted marine terraces along the Akatore Fault near Dunedin, South Island, New Zealand

The south Otago coast is characterised by a flight of marine terraces which have formed and been uplifted in Quaternary time. Optical luminescence dating along the recently active Akatore Fault has provided burial ages for beach sands resting upon a wave-cut platform in the upthrown block that are equal to or younger than 71 +/- 14 ka, and a burial age of c. 20 ka for the loess cap. The ages on beach sands clearly indicate that motion on this fault has been relatively limited since the last interglacial, while the loess date constrains the age of at least one faulting event on the Akatore Fault at this locality, and two events on the fault farther south, to be younger than 21 ka. The 6 m high (above high sea level) sand units in the terrace shown here to date from the late part of the last interglacial, suggest that sea levels at that time (oxygen isotope substage 5a) may not have been as low as -18 m, but rather closer to modem sea level. These applications of optical luminescence dating, using green light and infrared stimulation of quartz luminescence, constitute a new approach to studying tectonic rates on faults and paleo-sea levels.