Sea level and paleotemperature records from a mid-Holocene reef on the North coast of Java, Indonesia |
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| Authors: | Karem Azmy Evan Edinger Joyce Lundberg Wilfredo Diegor |
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| Institution: | (1) Department of Earth Sciences, Memorial University of Newfoundland, St John’s, NL, A1B 3X5, Canada;(2) Department of Geography, Memorial University of Newfoundland, St John’s, NL, A1B 3X9, Canada;(3) Department of Biology, Memorial University of Newfoundland, St John’s, NL, A1B 3X9, Canada;(4) Department of Geography and Environmental Studies, Carleton University, Ottawa, ON, K1S 5B6, Canada |
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| Abstract: | Mid-Holocene age fossil-fringing reefs occur along the tectonically stable north coast of Java, Indonesia, presenting an opportunity
for sea level and paleoclimate reconstruction. The fossil reef at Point Teluk Awur, near Jepara, Central Java, contains two
directly superposed horizons of Porites lobata microatolls. Corals in the lower horizon, 80 cm above modern sea level, yielded Uranium series dates of 7090 ± 90 year BP,
while corals in the upper horizon at 1.5 m grew at 6960 ± 60 year BP. These dates match the transgressive phase of regional
sea-level curves, but suggest a mid-Holocene highstand somewhat older than that recorded on mid-Pacific islands. Paleotemperature
was calibrated using Sr/Ca and δ18O values of a modern P. lobata coral and the locally measured sea surface temperature (SST), yielding SST–Sr/Ca and SST–δ18O calibration equations T
Sr/Ca = 91.03–7.35(Sr/Ca) and
Td18 \textO T_{{\delta^{18} {\text{O}}}} = −3.77 to −5.52(δ18O)]. The application of the local equations to Sr/Ca and δ18O measurements on these corals yielded a range of temperatures of 28.8 ± 1.7°C, comparable to that of the modern Java Sea
(28.4 ± 0.7°C). A paleo-salinometer Δδ18O = ∂δ18O/∂T (
Td18 \textO T_{{\delta^{18} {\text{O}}}} − T
Sr/Ca)], re-calculated using the local parameters, also suggests Java Sea mid-Holocene paleosalinity similar to modern values. |
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