Lichenometric dating of the ‘Little Ice Age’ maximum in Mt Cook National Park, Southern Alps, New Zealand

Abstract

Lichenometric dating studies using the yellow-green Rhizocarpon subgenus at the Eugenie, Hooker, Mueller and Tasman Glaciers in Mt Cook National Park, Southern Alps, New Zealand, reveal a ‘Little Ice Age’ maximum during the mid-eighteenth century (around AD 1725-1740). Lichenometric dating curves, constructed for Mueller Glacier in a preliminary study, were modified using local control points at the other glaciers. Modification was necessary because of variations in local ecological conditions. The ‘Little Ice Age’ chronology is similar for three out of the four glaciers studied. All except Tasman Glacier underwent a major glacier front oscillation directly following the ‘Little Ice Age’ maximum. After a slow but constant retreat during the second half of the eighteenth and the first half of the nineteenth centuries, the glaciers experienced major readvances during the second half of the nineteenth century (around AD 1860 and 1890/95), and during the early decades of the twentieth century. Tasman Glacier, as the exception, returned to its ‘Little Ice Age’ maximum frontal position during the late nineteenth century, overtopping pre-existing ‘Little Ice Age’ moraines, and therefore preventing detailed dating of these moraines. Differences in dating from previous lichenometric studies may be due to the different methods used.