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Origin and timing of the Miocene-Pliocene unconformity in Southeast Australia

Julie A. Dickinson, Malcolm W. Wallace, Guy R. Holdgate, Stephen J. Gallagher and Lindsay Thomas
Origin and timing of the Miocene-Pliocene unconformity in Southeast Australia
Journal of Sedimentary Research (March 2002) 72 (2): 288-303


An unconformity is present close to the Miocene-Pliocene boundary in the onshore and nearshore portions of the Otway, Port Phillip-Torquay, and Gippsland basins of southeast Australia. The unconformity is angular (generally <1-5 degrees angularity), with the underlying Miocene units having been deformed (gentle folding and reverse faulting) and eroded prior to deposition of the Pliocene succession. The unconformity also marks a change from Oligocene-Miocene deposition of cool-water carbonate sediments and brown coal-bearing successions to the accumulation of more siliciclastic-rich sediments in Pliocene time. The Miocene-Pliocene boundary therefore represents an interval of significant regional uplift in the southeast Australian basins. The amount of section removed is greatest around the Otway and Strzelecki ranges in Victoria, where up to a kilometer of section may have been removed. In most onshore sections of the Victorian basins hundreds of meters of section have been eroded. In distal offshore locations the boundary becomes conformable. The timing of uplift and erosion is best constrained in the Otway and Port Phillip basins, where late Miocene (N16 approximately 10 Ma) sediments underlie the unconformity and earliest Pliocene ( approximately 5 Ma) sediments overlie it. This timing coincides with a change in the dynamics of the Australian plate, beginning at around 12 Ma. Southeast Australia is currently under a NW-SE compressional regime, and this has probably persisted since the late Miocene. In the basins (as opposed to the basement-dominated highland areas), the late Miocene uplift event is more significant than later Pliocene-Recent uplift.

ISSN: 1527-1404
EISSN: 1938-3681
Serial Title: Journal of Sedimentary Research
Serial Volume: 72
Serial Issue: 2
Title: Origin and timing of the Miocene-Pliocene unconformity in Southeast Australia
Affiliation: University of Melbourne, School of Earth Sciences, Melbourne, Victoria, Australia
Pages: 288-303
Published: 200203
Text Language: English
Publisher: Society of Economic Paleontologists and Mineralogists, Tulsa, OK, United States
References: 77
Accession Number: 2002-029884
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., 1 table, sketch maps
S39°00'00" - S38°00'00", E147°00'00" - E149°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 200211
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