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Abstract

The Cottons Breccia is part of the upper Neoproterozoic (Ediacaran: 586–572 Ma) Grassy Group, exposed
on King Island, Tasmania. This formation has been widely interpreted as an unambiguous tillite, in support
of tectono-climatic models that invoke catastrophic latest Neoproterozoic global glaciation. However,
dissenting opinions interpret the Cottons Breccia as a tectonic breccia.
In this paper,we reviewthe tectonostratigraphy of the Cottons Breccia, and the enclosing Grassy Group.
We find no unambiguous evidence for a direct glacial origin, as postulated by some early workers. An
interpretation of the Cottons Breccia as a deposit within half-graben in the shoulder regions of an actively
developing latest Neoproterozoic volcanic rifted margin is consistent with all the available sedimentological,
structural, geochronological, and tectonic evidence.

Item Type:	Article
Authors/Creators:	Direen, NG and Jago, JB
Keywords:	Neoproterozoic glaciations Palaeogeography Tasmania Tectonostratigraphy Volcanic rifted margins
Journal or Publication Title:	Precambrian Research
ISSN:	0301-9268
DOI / ID Number:	10.1016/j.precamres.2008.05.008
Additional Information:	The definitive version is available at http://www.sciencedirect.com
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