Sea level and paleotemperature records from a mid-Holocene reef on the North coast of Java, Indonesia.

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 $$ T_{{\delta^{18} {\text{O}}}} $$ = −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 ( $$ T_{{\delta^{18} {\text{O}}}} $$ − T_Sr/Ca)], re-calculated using the local parameters, also suggests Java Sea mid-Holocene paleosalinity similar to modern values. [ABSTRACT FROM AUTHOR]