Mauke, Mitiaro and Atiu: Geomorphology of Makatea Islands in the Southern Cooks

Abstract

Mauke, Mitiaro and Atiu are deeply eroded volcanic islands in the southern Cook Islands, south Pacific, each surrounded by a rim of elevated Cenozoic reef limestone (makatea). This paper presents the results of instrumental topographic surveys of each island. The maximum elevation of the volcanics is 24.4, 8.9 and 71.0 m on Mauke, Mitiaro and Atiu, respectively, and of the makatea 14.7, 10.9 and 22.1 m. The makatea is fringed on its seaward side and in places partially overlain by a sequence of late Pleistocene reef limestones which reach maximum elevations of 12.7, 7.8 and 12.2 m respectively. These exhibit varied reef facies as well as emergent reef topographies, especially groove- and-spur systems. Elevated notches, cliff-foot benches and emergent reef flats indicate higher Holocene relative sea-levels at up to at least 3 m above present. These data are compared with similar features on Mangaia, also in the southern Cooks, and the very different topographic and stratigraphic records on Rarotonga and Aitutaki, and the implications of the independent island histories thus revealed for previous discussions of lithospheric flexure and Pleistocene sea-level change are reviewed.