Age and significance of the Platypus Tuff Bed, a regional reference horizon in the Upper Permian Moranbah Coal Measures, north Bowen Basin

Michaelsen, P., Henderson, R.A., Crosdale, P.J., and Fanning, M. (2001) Age and significance of the Platypus Tuff Bed, a regional reference horizon in the Upper Permian Moranbah Coal Measures, north Bowen Basin. Australian Journal of Earth Sciences, 48 (2). pp. 183-192.

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Abstract

The Platypus Tuff Bed in the Permian Moranbah Coal Measures provides a basin-wide marker horizon traceable for over 300 km along strike. The bed is a tephra event unit, the product of a large-scale volcanic eruptive episode involving a pyroclastic volume > 10 km^3. The relatively even thickness (∼1-1.5 m) of the tuff across the entire northern Bowen Basin (∼10 000 km^2) implies a distant source. The tuff is ash-rich and its original geochemistry has been compromised by diagenetic alteration. Crystal content (10-15%) is dominated by quartz, suggesting a rhyolitic association. SHRIMP U-Pb analysis of zircons indicates an age of 258.9 ± 2.7 Ma for the Platypus Tuff Bed, confirming the Late Permian age that has generally been assigned to the Blackwater Group. The age framework now apparent for the coal-bearing Blackwater Group suggests an average depositional rate ranging from ∼133 m/10^6 years for its eastern depocentre in the northern Bowen Basin to ∼70 m/10^6 years in more marginal settings to the west.

Item ID: 13103
Item Type: Article (Refereed Research - C1)
Keywords: Bowen Basin; geochronology; Moranbah Coal Measures; Permian; Platypus Tuff Bed; uranium-lead dating
ISSN: 1440-0952
Date Deposited: 11 Dec 2010 00:06
FoR Codes: 04 EARTH SCIENCES > 0403 Geology > 040311 Stratigraphy (incl Biostratigraphy and Sequence Stratigraphy) @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 100%
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