Elsevier

Marine Geology

Volumes 311–314, 15 May 2012, Pages 57-62
Marine Geology

Letter
U/Pb dating of a terminal Pliocene coral from the Indonesian Seaway

https://doi.org/10.1016/j.margeo.2012.01.004Get rights and content

Abstract

Pristine detrital Platygyra corals were discovered in an exhumed package of syn-orogenic marine sediments on the island of Timor in the eastern Indonesian region and dated using U–Pb techniques. A single coral from the upper part of the sequence yields a 238U/206Pb–207Pb/206Pb concordia age of 2.66 ± 0.14 (2σ) Ma that is supported by coral 87Sr/86Sr chemostratigraphy and foraminiferal biostratigraphy from bounding strata. Minor U-series disequilibrium is best explained by U mobility within the last ~ 150 ka, as pore water chemistry was altered during exhumation, and is unlikely to have affected 238U/206Pb and the apparent sample age by more than 1–2%. The ability to date corals beyond the limits of 14C and U/Th techniques provides the opportunity to improve the temporal resolution of associated marine chronostratigraphic records. In this instance, we refine the timing of Timor's emergence from beneath the waters of the Indonesian Seaway (IS) and the initiation of turbiditic deposition at the study site to between ca. 3.35 and 2.66 Ma. These results have implications for the evolution of topography and IS oceanic pathways in the active orogenic belts along the northern fringes of the Australian Plate.

Highlights

► First ever U-Pb isochron for a coral of Pliocene age. ► First U-Pb age for coral from Indonesian region. ► U-Pb age supported by Sr chemostratigraphy, biostratigraphy and U-series. ► U-Pb age provides temporal constraints on topographic evolution of Timor.

Introduction

The tectonic opening and closing of oceanic pathways influence global thermohaline circulation (Berggren and Hollister, 1977), marine productivity (Schneider and Schmittner, 2006), and climate (Mudelsee and Raymo, 2005). Exhumed marine sequences in or adjacent to oceanic pathway systems (e.g., Central American seaway, Indonesian Seaway) provide opportunities to decipher tectonic, topographic, physical and chemical oceanographic pathway changes with relevance for marine faunal evolution (e.g. Jackson et al., 1996), salinity and temperature changes in adjacent oceans (e.g. Karas et al., 2009), major climate systems (e.g. von der Heydt and Dijkstra, 2011), and human evolution (Cane and Molnar, 2001). The ability to study these processes is partially limited by the difficulty in obtaining robust chronostratigraphy from marine sequences, due to factors including highly variable deposition rates, sediment reworking, lack of age-diagnostic fossils, lack of datable materials, and/or diagenetic alteration (Getty et al., 2001). U/Pb dating of detrital corals in exhumed marine sequences provides a novel and promising, albeit under-utilized, methodology to refine the chronostratigraphy of marine sequences under certain circumstances. Two prior successful attempts have been made in the Carribbean region, where U/Pb coral ages of 1.02 ± 0.07 Ma and 1.288 ± 0.034 Ma (Getty et al., 2001) and 5.52 ± 0.15 Ma (Denniston et al., 2008) were obtained. In this study, we make a first attempt to use U/Pb techniques to date pristine, detrital Platygyra corals from the syn-orogenic, marine Viqueque Megasequence (VM) presently exposed on the island of Timor in the eastern Indonesian region. Our results enable us to refine the chronostratigraphy of the VM and place finer temporal constraints on the onset of turbidite deposition and the emergence and vegetative colonization of the VM source region during a key time for IS evolution.

Section snippets

Geological setting

The NNE-directed voyage of the Australian continent at ~ 70 mm yr 1 relative to the Sunda Shelf (DeMets et al., 1994, see Fig. 1A) resulted in collision of the leading continental margin with the Banda Arc by the Miocene to early Pliocene (Audley-Charles, 2011, Rutherford et al., 2001). Tectonic processes including the accretion of the Banda Arc to the Australian continental crust (Bock et al., 2003, Nugroho et al., 2009) and the detachment of the downgoing slab from the Australia Plate lead to

Stratigraphy and foraminiferal biostratigraphy of the Viqueque Megasequence

The relatively undeformed VM overlies structurally complex older units. The VM Type and Northern Cuha sections are exposed in the Cuha River on the northern limbs of WNW-striking synclines near the town of Viqueque (Fig. 2). The base of the Type section unconformably overlies the synorogenic mélange and contains mudstone clasts probably derived from the mélange matrix. The basal carbonate chalk has foraminiferal assemblages indicative of a Zone N18 age (5.2–5.6 Ma) (Batu Putih Formation; Haig

Screening

Coral sample TL07 (Fig. 2e) was extracted from the upper conglomerate, subsampled and screened for signs of diagenetic alteration following the methods of Denniston et al. (2008). X-ray diffraction (XRD) revealed 100% aragonitic composition and scanning electron microscopy (SEM) revealed a primary aragonitic skeleton with delicate growth structures, original porosity and minimal aragonitic cement and interstitial mud (Fig. 3a). Measurement of 234U/238U and 230Th/238U can be a powerful

Discussion

As demonstrated by Getty et al. (2001) and Denniston et al. (2008), the U/Pb dating of primary coral aragonite is possible providing the original coral U-series chemistry is retained and unaltered by weathering, diagenesis, and/or contaminants such as marine cement and deritus. Such preservation requires an unusual set of circumstances; the sample must have experienced little if any subaerial exposure, which would promote the calcification of aragonite, and limited burial, which would promote

Acknowledgments

This work has profited from discussions with David Haig, Myra Keep and Eujay McCartain at the University of Western Australia and Jamie Shulmeister at University of Queensland. We thank ENI Pty Ltd, the University of Canterbury, and the Royal Society of New Zealand Marsden Research Council (Fast-start grant M1137) for financial support. We thank the Secretariat for Energy and Natural Resources (SERN) in Dili for their continuing support for our research in Timor Leste and Joao Edmundo dos Reis,

References (43)

  • D. Scholz et al.

    How precise are U-series coral ages?

    Geochimica et Cosmochimica Acta

    (2007)
  • L.J. Van Marle

    Bathymetric distribution of benthic foraminifera on the Australian–Irian Jaya continental margin, Eastern Indonesia

    Marine Micropaleontology

    (1988)
  • L.J. van Marle

    Late Cenozoic palaeobathymetry and geohistory analysis of Central West Timor, eastern Indonesia

    Marine and Petroleum Geology

    (1991)
  • J.J. Veevers et al.

    Timor trough and australia: facies show topographic wave migrated 80 km during the past 3 m.y

    Tectonophysics

    (1978)
  • J.D. Woodhead et al.

    U–Pb geochronology of speloethems by MC-ICPMS

    Quaternary Geochronology

    (2006)
  • M.G. Audley-Charles

    The Geology of Portugese Timor

    (1968)
  • M.G. Audley-Charles

    Rates of Neogene and Quaternary tectonic movements in the southern Banda Arc based on micropalaeontology

    Journal of the Geological Society

    (1986)
  • M.G. Audley-Charles

    Tectonic post-collision processes in Timor

  • Y. Bock et al.

    Crustal motion in Indonesia from Global Positioning System measurements

    Journal of Geophysical Research B: Solid Earth

    (2003)
  • M.A. Cane et al.

    Closing of the Indonesian seaway as a precursor to east African aridification around 3–4 million years ago

    Nature

    (2001)
  • D.J. Carter et al.

    Stratigraphical analysis of island arc-continental margin collision in eastern Indonesia

    Journal of the Geological Society of London

    (1976)
  • Cited by (11)

    • Mélange versus forearc contributions to sedimentation and uplift, during rapid denudation of a young Banda forearc-continent collisional belt

      2017, Journal of Asian Earth Sciences
      Citation Excerpt :

      The Viqueque Formation in the type area consists of a rhythmic succession of interbedded, normally graded sandstones and massive mudstones, punctuated by thick, lensoidal conglomerates and sandstones. The conglomerates attain thicknesses in excess of 70 m and commonly contain aragonitic detrital coral heads; a U-Pb age of a coral constrains the age of the top of the Northern Cuha section (Quigley et al., 2012) (Fig. 4c). Most of the paleoflow directions in Viqueque are toward the south and southwest and no tectonic rotation has been documented in the basin (Aben et al., 2014).

    • New constraints on the timing of flexural deformation along the northern Australian margin: Implications for arc-continent collision and the development of the Timor Trough

      2017, Tectonophysics
      Citation Excerpt :

      Microfossil assemblages from the northwestern Australian margin indicate that further ITF restriction occurred after 4 Ma (Gallagher et al., 2009). This timing corresponds with the rising of Halmahera and the islands of the eastern Banda Sea, including Timor Island, which started to emerge at 4.5 Ma and rapidly uplifted after 3 Ma (Haig, 2012; Quigley et al., 2012; Nguyen et al., 2013). Our data suggest that at ca. 3 Ma, the renewed flexure across the northern Australian margin associated with rapid subsidence in the Timor Trough would have shaped the modern bathymetry of the region and constrained the flow of the ITF to its current pathway north and south of Timor (Ombai Strait and the Timor Trough, respectively; Fig. 1).

    • Controls on the distribution and growth of isolated carbonate build-ups in the Timor Sea (NW Australia) during the Quaternary

      2015, Marine and Petroleum Geology
      Citation Excerpt :

      During the Pliocene, changes in position and geometry of inflow passage of ITF occurred (Fig. 21), due to northward advancement of New Guinea (Cane and Molnar, 2001). Rapid uplift of the Timor Island at around 3 Ma BP (Quigley et al., 2012; Nguyen et al., 2013) and the development of the Timor Trough may have caused major changes to the ITF paths and flow regime (Fig. 21). Biostratigraphic data from the southern North West Shelf of Australia suggests that the southwest flowing ITF activity fluctuated during the Pliocene and Quaternary (Gallagher et al., 2009) and reached a maximum intensity from 1.6 to 0.8 Ma BP, when the modern Leeuwin Current initiated (Holloway, 1995; Gallagher et al., 2009).

    View all citing articles on Scopus
    View full text