6556 26 archive 379 disk0/00/00/65/56 2008-06-04 00:01:22 2008-07-18 11:00:07 2008-07-16 17:26:47 article show Clive.Burrett@utas.edu.au Bromfield KE Burrett CF Clive.Burrett@utas.edu.au Leslie RA Meffre S Sebastian.Meffre@utas.edu.au pub 260100 restricted andesite, Antarctica, dolerite, Jurassic, plants, Pteridophyta, Tasmania. The definitive published version is available online at: http://www.tandf.co.uk/journals Jurassic plants excavated from a 1265 m site, at Lune River, southern Tasmania, include an araucarian tree and numerous pteridophytes, belonging to the orders Osmundales, Filicales and Bennettitales. The fossils occur in 2 – 3 m of immature volcanilithic sandstone beds. The sandstone consists primarily of clasts from granitic basement rocks underlying much of southeast Tasmania and mafic clasts containing feldspathicmicroliths, and primary, phreatomagmatic quartz crystals. Detrital zircons from the sandstones are mostly Early Jurassic (Toarcian) in age (182+4 Ma) with minor Triassic (226 Ma), Devonian (380 – 360 Ma) and Proterozoic populations. Basaltic andesite, hereafter referred to as andesite, caps the volcanilithic units and displays similar ratios of fluid-immobile trace elements (e.g. Zr/Nb, Ti/V), to the Jurassic dolerite found in Tasmania, indicative of a common source. The andesites are correlated with the Jurassic Kirkpatrick Basalts (Trans-Antarctic Mountains, Antarctica) based on their field relationships with bounding strata, age, and distinctive similarities in major-element composition and fluid-immobile traceelement ratios. The andesite is interpreted as an extrusive equivalent of the Tasmanian dolerite. Importantly, drillcore from Lune River contains stoped clasts of andesite in fine-grained dolerite, indicating that the andesite pre-dates the dolerite. Thermal alteration index of microfossils (3 – 3.3) and reflectance of organic material within the sediments (0.54 – 0.77 Ro) resulted from contact metamorphism associated with the emplacement of this basalt. The sedimentology and stratigraphy of the depositional environment, plus the presence of hydrophilic pteridophytes and gymnosperms, indicates that the Toarcian environment was temperate to warm and humid, with an abundant supply of water. 2007-10 published Australian Journal of Earth Sciences 54 7 965-974 10.1080/08120090701488297 TRUE 0812-0099 http://dx.doi.org/10.1080/08120090701488297 5397 5 6556 1 application/pdf en staffonly cc_utas

51585.pdf

51585.pdf 1538515 http://eprints.utas.edu.au/6556/1/51585.pdf