Ch. Stirling et al., TIMING AND DURATION OF THE LAST INTERGLACIAL - EVIDENCE FOR A RESTRICTED INTERVAL OF WIDESPREAD CORAL-REEF GROWTH, Earth and planetary science letters, 160(3-4), 1998, pp. 745-762
We report new mass spectrometric U-series ages for eight Last Intergla
cial fossil reefs along the continental margin of Western Australia. C
orals were selected in growth position from localities that are charac
terized by apparently low levels of diagenesis and relative tectonic s
tability so that the fossil reefs provide critical information on Last
Interglacial sea-levels without requiring corrections for tectonic mo
vements. In addition, we have improved the constraint on the timing of
onset of reef growth by recovering drill core coral from the base of
the reefs. Uranium and thorium isotopes were measured with high levels
of precision, leading to improvements in age resolution and allowing
samples which have undergone diagenetic exchange of uranium and thoriu
m to be more easily identified and discarded. These data supplement ou
r previous results for Rottnest Island and Leander Point, leading to m
ore than seventy mass spectrometric U-series ages from which constrain
ts can be placed on the timing, duration and character of the Last Int
erglacial sea-level highstand. Reliable ages show that reef growth sta
rted contemporaneously at 128 +/- 1 ka along the entire Western Austra
lian coastline, while relative sea-levels were at least 3 m above the
present level. Because Western Australia is located far from the forme
r Penultimate Glacial Maximum ice sheets and are not significantly eff
ected by glacial unloading, these data constrain the timing of onset o
f the Last Interglacial period to 128 +/- 1 ka, assuming reef growth s
tarted soon after sea-level approached interglacial levels. A unique r
egressive reef sequence at Mangrove Bay constrains the timing of termi
nation of the Last Interglacial period to 116 +/- 1 ka, The major epis
ode of reef building, however, both globally and locally along the Wes
tern Australian coast, is restricted to a very narrow interval occurri
ng from similar to 128 ka and similar to 121 ka, suggesting that globa
l ocean surface temperatures were warm and/or sea-levels were stable e
nough to allow prolific reef growth only during the earlier part of th
e Last Interglacial. (C) 1998 Elsevier Science B.V. All rights reserve
d.