The oldest Quaternary ooids and young reefs in the eastern Indian Ocean, evidence from the Northwest Shelf of Australia, IODP Expedition 356

Author(s): Gallagher, Stephen J.; Reuning, Lars; Himmler, Tobias; Henderiks, Jorijntje; De Vleeschouwer, David; Groeneveld, Jeroen; Fulthorpe, Craig S.; Bogus, Kara
Integrated Ocean Drilling Program, Expedition 356 Scientists, College Srtation, TX
Author Affiliation(s): Primary:
University of Melbourne, Parkville, Victoria, Australia
RWTH Aachen University, Germany
University of Bremen, Germany
Uppsala University, Sweden
University of Texas at Austin, United States
Integrated Ocean Drilling Program, United States
Volume Title: AGU 2016 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2016; American Geophysical Union 2016 fall meeting, San Francisco, CA, Dec. 12-16, 2016. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Modern reefs are common in the Indian Ocean off the west coast of Australia (south of 15°S) where the warm Leeuwin Current extends their modern distribution to 29°S. Two key features that distinguish these tropical from non-tropical carbonates are the presence of coral reefs and ooids. Coral reefs are generally confined to seawater >18°C. Ooids form at temperatures >20°C with salinities >37 ppm. Modern ooids are forming in the hypersaline Shark Bay and are well known from late Quaternary strata in the region. Globally, marine ooids have been interpreted to be direct evidence of physiochemical precipitation from seawater during periods of elevated alkalinity and supersaturation. Their occurrence in the subsurface of the Northwest Shelf of Australia (NWS) may be used as sea surface temperature, palaeobathymetry and aridity indices. However, the longer-term history of reefs and ooids is not well constrained in the NWS. IODP expedition 356 cored a series of sections down dip from the Houtman-Abrolhos (29°S) and Barrow Island reefs (22°S) and up dip from the Rowley Shoals (18°S) to determine their age and origin. The stratigraphy of the cored sections was mapped using regional seismic data to constrain the age of reef onset. Coring also yielded several horizons of pre-late Quaternary ooids. Our analyses reveals that reefs from 22°S to 30°S are younger than 600,000 years old and that ooids are present in strata up to 750,000 years old. We suggest stronger Leeuwin Current activity related to an enhanced Indonesian Throughflow and increased aridity triggered tropical carbonate expansion on the Northwest Shelf during the Middle Pleistocene Transition. Knowledge of the timing and circumstances that triggered tropical reef development in the Indo-Pacific in the past is critical if we are to understand the resilience of modern reefs with future climate change.
Year of Publication: 2016
Research Program: IODP2 International Ocean Discovery Program
Key Words: 24 Surficial Geology, Quaternary Geology; Anthozoa; Cenozoic; Cnidaria; Continental shelf; Cores; Expedition 356; Indian Ocean; International Ocean Discovery Program; Invertebrates; Marine sediments; Pacific Ocean; Quaternary; Sediments
Record ID: 2017062453
Copyright Information: GeoRef, Copyright 2018 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States

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