Stratigraphy and sedimentology of the Orakei maar lake sediment sequence (Auckland Volcanic Field, New Zealand)

Abstract

Global paleo-climate reconstructions are largely based on observations from the Northern Hemisphere despite increasing recognition of the importance of the Southern Hemisphere mid-latitudes for understanding the drivers of the global climate system. Unfortunately, the required complete and high-resolution terrestrial records from the Southern Hemisphere mid-latitudes are few. However, the maar lakes in the Auckland Volcanic Field (AVF), New Zealand, are crucial in this regard as they form outstanding depositional basins due to their small surface-to-depth ratio, restricted catchment, and absence of ice cover since their formation, hence ensuring continuous sedimentation with anoxic bottom water. Significantly, the estimated age of the AVF of ca. 250 ka may allow development of a continuous sediment record spanning the last two glacial cycles. The Orakei maar lake sediment sequence examined in this study spans the Last Glacial Cycle (ca. 126 to ca. 9.5 ka cal BP) from the phreatomagmatic eruption to the crater rim breach due to post-glacial sea-level rise. Two overlapping cores of >100 m sediment were retrieved and combined to develop a complete composite stratigraphy that is presently undergoing a wide range of multi-proxy analyses.