HR: 1340h
AN: PP13A-0585    [Abstracts]
TI: Documentation of Carbonate Platform Drowning During MIS 4 in the Huon Gulf, Papua New Guinea
AU: * Riker-Coleman, K E
EM: rike0003@tc.umn.edu
AF: Dept. of Geological Sciences, University of Minnesota Duluth, Duluth, MN 55812
AU: Gallup, C
EM: cgallup@d.umn.edu
AF: Dept. of Geological Sciences, University of Minnesota Duluth, Duluth, MN 55812
AU: Webster, J
EM: jwebster@mbari.org
AF: Monterey Bay Aquarium Research Institute, 7700 Sandholdt Rd, Moss Landing, CA 95039
AU: Cheng, H
EM: cheng021@umn.edu
AF: Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455
AU: Burr, G
EM: burr@u.arizona.edu
AF: NSF-Arizona AMS Facility, 1118 E 4th St, Tucson, AZ 85721
AU: Potts, D
EM: potts@biology.ucsc.edu
AF: Ecology and Evolutionary Biology, University of California, Santa Cruz, CA 95064
AU: Potts, D
EM: potts@biology.ucsc.edu
AF: Earth Sciences Department, University of California, Santa Cruz, CA 95064
AU: Silver, E
EM: esilver@emerald.ucsc.edu
AF: Earth Sciences Department, University of California, Santa Cruz, CA 95064
AU: Wallace, L
EM: l.wallace@gns.cri.nz
AF: Institute of Geological and Nuclear Sci., PO Box 30368, Lower Hutt, 6009 New Zealand
AU: Edwards, R L
EM: edwar001@umn.edu
AF: Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455
AB: In 2001 we used the ROV Jason to collect material from the tops of a series of carbonate platforms in the Huon Gulf, Papua New Guinea. The Huon Gulf represents an actively subsiding foreland basin that is the result of the collision of the South Bismarck plate with the northern Australian continental margin. Galewsky et al. (1996) modeled the coral reef development and suggested that the coral reefs are able to keep up with subsidence at a rate comparable with the subsidence rate, but that they would drown during major sea level rises. Wallace (2002) further constrained the simple model to include the all of the nine platforms we identified. We collected coral samples from the tops of the platforms because the model indicated that these corals should represent reef growth just prior to drowning. We measured the U-Th-(Pa) isotopic composition of eight distinct pieces of coral from the -250 m platform, the shallowest and best-preserved of the nine identified platforms. Corals measured represent four different species/genera: Galaxia astreata, Porites, Favia and Stylophora. Three of these four corals tend to have broad growth ranges, from 0-60 m water depth; Favia is the exception and grows in shallower water (0-20m). Three samples were clearly diagenetically altered showing either anomalously low uranium concentration or high 232Th. The remaining five produced the following ages: 57.7 (+/- 1.5) ka, 60.1 (+/- 0.4) ka (231Pa age of this sample: 59.5 (+/- 1.1) ka), 62.1 (+/- 0.9) ka, 65.9 (+/- 0.87) ka, and 67.4 (+/- 0.8) ka. All of the samples have d234U initial values within error of modern seawater and a check for protactinium concordancy on one sample passed, which suggests these are reliable 230Th ages. Sedimentary analyses of the samples indicate a clear signature of coral drowning, characterized by a vertical transition from corals typical of deep, fore-reef slope settings (30-60 m) to thick crusts of coralline algae indicative of deeper fore-reef slope setting (60-100 m). Uncalibrated C-14 ages for two samples of the algal crusts are 30.5 (+/- 0.4) KyrBP and 39.6 (+/-1.1) KyrBP. During this period of coral and algal growth, Greenland ice core data indicate millennial-scale climate change events, known as Dansgaard-Oeschger cycles, in the North Atlantic (Stuvier and Grootes, 2000). Coral data from Papua New Guinea link sea level rises of 10-15 m and 1000-2000 years duration to those events (Chappell, 2002). Our data are consistent with the coral drowning due to these millennial scale sea-level changes and/or to long-term subsidence. Galewsky et al., (1996) Geology v. 24, 819-822; L. Wallace (2002) PhD Thesis University of California; Stuvier and Grootes (2000) Quaternary Research v.3, 39-55; Chappell (2002) Quaternary Science Reviews, v.21, 1229-1240.
DE: 8155 Plate motions--general
DE: 4267 Paleoceanography
DE: 4556 Sea level variations
DE: 1035 Geochronology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting