THE KAMES OF ROHAN: LUMINESCENCE AGES OF ICE MARGINAL ACTIVITY IN MIDDLE EARTH (RANGITATA VALLEY, NEW ZEALAND) THROUGH THE LAST GLACIATION
The kame terrace surface sediments and associated buried stratigraphy document dramatic elevational fluctuations of the ice margin, here measured relative to the modern valley floor. Ice was 540 m thick ca. 63 ka and thinned to 50 m by ca. 37 ka. Ice then thickened to a near-maximum, 480 m above the valley floor by ca. 32 ka, before thinning again to 60 m by ca. 27 ka. The final ice re-expansion to middle elevations (230 m) occurred by ca. 26.5 ka, and ice subsequently thinned slowly through the period of the Northern Hemisphere last glacial maximum.
The kame terrace record is fully consistent with and complements published chronologies of glaciation in the study area, from lithofacies analysis and OSL dating and CRN dating (Shulmeister et al., 2018), and is similarly correlative with extensive CRN chronologies from the Mackenzie Basin (e.g., Putnam et al., 2013). However, the ca. 32-27 ka ice thickness decrease (425 m) confirms substantial ice volume depletion during the early portion of the “New Zealand glacial maximum,” and identifies substantial MIS 2 ice cover, represented in most New Zealand moraine chronologies, as a clear re-expansion of ice cover. Thus, the late MIS 3 and early MIS 2 advances can be viewed as distinct events.