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

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 d18 O values of a modern P. lobata coral and the locally measured sea surface temperature (SST), yielding SST-Sr/Ca and SST-

Source of diagenetic fluids from fluid-inclusion gas ratios

“…The nature of the sediments and diagenetic history have been well established through earlier studies of their detailed petrographic, microthermometric and geochemical attributes (e.g., Azmy et al, 2006;Knight et al, 2007;Azmy et al, 2008aAzmy et al, , 2008cEdinger et al, 2008;Knight et al, 2008;Conliffe et al, 2009;Azmy and Conliffe, 2010;Conliffe et al, 2010Conliffe et al, , 2012Conliffe et al, 2012). They include unaltered Modern aragonitic coral (A) from the Java Sea at Point Teluk Awur, near Jepara, Central Java (Azmy et al, 2008a;Edinger et al, 2008) and altered phases of marine carbonates, including lime mudstones (C1), late fracture-filling calcite (C3), dolomicrites (D1) of early diagenesis and late hydrothermal dolomites (D2 and D3, Table 1).…”

“…The detailed petrography of the carbonate samples is described by Azmy et al (2006Azmy et al ( , 2008aAzmy et al ( , 2008b) and summarized in Table 1. The crushed material, from each sample, was intentionally selected to contain only a single carbonate phase to avoid mixing of fluidinclusion gases released from different carbonates phases.…”

“…The analyzed samples cover a wide spectrum of carbonates (Table 1) including well-preserved marine carbonates (modern aragonitic coral), altered sediments at near surface conditions (e.g., lime mudstones and dolomicrite) and late hydrothermal (fracture-filling) dolomite (Azmy et al, 2006(Azmy et al, , 2008a(Azmy et al, , 2008b). The samples were globally selected from different sedimentary basins of different ages (Table 1) to examine the influence of age and burial conditions on the results.…”

“…They include unaltered Modern aragonitic coral (A) from the Java Sea at Point Teluk Awur, near Jepara, Central Java (Azmy et al, 2008a;Edinger et al, 2008) and altered phases of marine carbonates, including lime mudstones (C1), late fracture-filling calcite (C3), dolomicrites (D1) of early diagenesis and late hydrothermal dolomites (D2 and D3, Table 1). The altered phases (hosted in lime mudstones and dolomites) were collected from two sequences (Lower Ordovician St. George Group in western Newfoundland, Canada and Mesoproterozoic Vazante sequence in east central Brazil) of different ages and from different sedimentary basins (Azmy et al, 2006;Knight et al, 2007;Azmy et al, 2008aAzmy et al, , 2008bAzmy et al, , 2008cKnight et al, 2008;Azmy and Conliffe, 2010;Azomani et al, 2013).…”

“…However, no microthermometric measurements were obtained from the dolomicrites because of the crystal near-micritic size and submicron inclusions. Petrography of the investigated dolomites and their 2-phase fluid inclusions have been recently studied and discussed in detail by Azmy et al (2001Azmy et al ( , 2006Azmy et al ( , 2008aAzmy et al ( , 2008bAzmy et al ( , 2008c), Conliffe et al (2009Conliffe et al ( , 2010 and Azmy and Conliffe (2010), which makes these dolomites ideal candidates for a fluid-inclusion gas ratio investigation. Origin of dolomitizing fluids have been the focus of studies particularly because of the development of porosity associated with dolomites, which constitute a significant global hydrocarbon reservoirs.…”