Holocene relative sea-level changes in Cleveland Bay, north Queensland, Australia
Full understanding of sea level, ice sheet and earth interactions during the Holocene,
and the impact of current and future global sea-level rise requires observations of
Holocene relative sea-level change from both near- and far-field locations. North
Queensland is an ideal far-field location for testing models of mid/late Holocene global
meltwater discharge and the viscosity structure of the solid earth, despite problems
with indicators and gaps in its Holocene sea-level record.
This thesis addresses inadequacies in the record of Holocene sea-level changes in
North Queensland using for the first time a foraminifera-based transfer function, which
employs vertically zoned modern intertidal and shallow subtidal calcareous foraminifera
to reconstruct past water-level changes from fossil foraminiferal assemblages. This
technique provides reconstructions which are of equal or greater vertical precision than
reconstructions using mangrove mud or coral indicators on this coastline. AMS 14C
dated calcareous foraminifera provide intra-site correlation of environmental and sealevel
changes over the past 6000 calibrated years.
This thesis also highlights problems which limit the applicability of the transfer function
technique in this environment, including poor preservation of agglutinated foraminifera
in fossil sediments and reworking of Holocene intertidal and shallow subtidal sediments
which is not obvious from visual, bio- or litho-stratigraphical analysis.
By creating new sea-level index points and re-calibrating existing ones from other
indicators I infer the general form of the mid/late Holocene sea-level record in central
North Queensland as sea level rising above its present value prior to 6700 cal years
BP, with relatively stable sea level 1-2.3 m above present between 6700-5000 cal
years BP, and between 1-2.8 m above present between 5000-3000 cal years BP. This
is followed by sea-level fall to between 0.4-0.8 m above present until 1200 cal years BP
and subsequent slow fall to present. This sea-level data supports theories suggested
by geophysical models of a gradual end to global ice sheet melt, with melting ending
after 5000 cal years BP.