The imprint of cryosphere and mantle dynamics in the coral reefs of Australia

January 30, 2025

Andrea Dutton

Hosted by Pat Keys

Abstract

This is a tale of two coastlines. They share a common history of global sea level change on the same continent, yet there are distinct and telling differences in the sedimentary record that has been left behind. In one case, an uplifted margin gives us unprecedented insight into the
evolution of coral reef accretion along the west coast of Australia during the Last Interglacial. The exposed cliffs at Red Bluff provide clear sedimentary evidence of multiple episodes of exposure and inundation during the Last Interglacial sea level highstand (- 129 to 116 thousand years ago). These sea level oscillations point to a dynamic cryosphere during this past warm period. In the second case, evidence of high sea levels during the Last
Interglacial are notably absent above modern sea level in the Great Barrier Reef along the northeast margin of Australia. Instead, shallow water reef deposits from this time interval have been discovered at depth, beneath the Holocene reef, consistent with dynamic topography modeling that predicts subsidence in this region. In addition to explaining the present elevation of Last Interglacial reefs, we propose that long term mantle-driven subsidence played a central role in the development and longevity of the Great Barrier Reef, resulting in the largest modern
coral reef system on the planet.