Pleistocene sedimentary deposits on subantarctic Macquarie Island: Contribution to IGBP-Pages Pole Equator Pole Transect II

• Other Authors: SELKIRK, PATRICIA (hasPrincipalInvestigator), SELKIRK, PATRICIA (processor), Australian Antarctic Data Centre (publisher)
• Format: Dataset
• Language: unknown
• Published: Australian Antarctic Data Centre
• Subjects: climatologyMeteorologyAtmosphere; geoscientificInformation; PALEOSOLS; EARTH SCIENCE; PALEOCLIMATE; LAND RECORDS; TECTONIC LANDFORMS; SOLID EARTH; GEOMORPHIC LANDFORMS/PROCESSES; MACQUARIE ISLAND; MACQUARIE RIDGE; PALAEOBEACHES; PLEISTOCENE; RAISED BEACHES; SUBANTARCTIC; THERMOLUMINESCENCE DATING; UPLIFT; Paleo Start Date 340 ka; Paleo Stop Date 172 ka; PHANEROZOIC > CENOZOIC > QUATERNARY > OCEAN > SOUTHERN OCEAN; SOUTHERN OCEAN > GEOGRAPHIC REGION > POLAR; Southern Ocean; Macquarie Island
• Online Access: https://researchdata.ands.org.au/pleistocene-sedimentary-deposits-transect-ii/700339; https://data.aad.gov.au/metadata/records/ASAC_904; http://nla.gov.au/nla.party-617536

Macquarie Island is an emergent part of the Macquarie Ridge Complex composed of ocean-floor rocks of Miocene age now 4000 m above the ocean floor. A number of landforms, including palaeobeaches now above sea level (a.s.l.) on Macquarie Island, were formed by marine erosion during uplift of the island. During the last Pleistocene period of low sea level (c. 20 ka) the island was three times larger than now. Thermoluminescence (TL) dating of two palaeobeaches indicates Pleistonce ages: 172 plus or minus 40 ka for one at 100 m a.s.l. and 340 plus or minus 80 ka for another at 263 m a.s.l. Matching the altitude sequence of palaeobeaches on Macquarie Island with the pattern of peaks in world sea level determined from deep sea cores allows an independent estimate of beach ages. Comparison of the altitude and sea level sequences most plausibly places the 100 m palaeobeach in Oxygen Isotope Stage 5e (130-125 ka) and the 263 m palaeobeach in Stage 9 (340-330 ka), matching reasonably with the TL dates. Other palaeobeaches at about 50 m and 170-190 m a.s.l. then correlate with high sea levels. We calculate an average rate of uplift for the island of 0.8 mma-1. 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.