Pleistocene uplift and palaeoenvironments of Macquarie Island: evidence from palaeobeaches and sedimentary deposits

Abstract

Macquarie Island (54°30′S, 159°00′E) is an emergent part of the Macquarie Ridge Complex. A number of landforms, including palaeobeaches now above sea level were formed by marine erosion during uplift of the island. Two lines of evidence are considered: direct dating of raised beaches by the thermoluminescence method, and cross-matching of the world sea-level sequence with the altitudinal sequence of beaches. An average rate of uplift for the island of 0.8 mma-1 is calculated. At this rate, 4000 m of Macquarie Ridge uplift would have taken about five million years and the top of the island may first have emerged some 700 to 600 ka. During the six Pleistocene glacial-interglacial cycles since then, there has been periglacial rather than glacial activity on cold uplands, but conditions suitable for vegetation of the present type persisted close to sea level.