TASMANITE OIL SHALE
Tasmanites is a long-ranging genus of marine microfossil (see
example; see
another example). Tasmanites fossils are organic-walled and
tiny (usually <0.1 to ~0.6 mm in size). Traditionally, their taxonomic
affinities have been uncertain, but most researchers now agree that Tasmanites
represent cysts of prasinophyte algae (Chlorophyta, Prasinophyceae).
Tasmanites is famously abundant in shales of the Lower Permian Quamby Mudstone in
Tasmania. The Tasmanites-rich shales are informally called Òwhite
coalsÓ. TasmaniaÕs white coals are actually a specific variety of oil
shale (kerogen shale/kerogenite) called tasmanite. They are very
rich petroleum source rocks that are not restricted to the Permian of Tasmania.
Published research indicates that Permian-aged
tasmanite oil shales in Tasmania were deposited in a shallow marine setting
dominated by sea ice and/or icebergs, representing a post-glacial sea level
rise and flooding of a still-glaciated landscape.
Stratigraphy: lower Quamby Mudstone, Lower Parmeener Supergroup, probably Sakmarian
Stage, lower Lower Permian.
Locality:
unrecorded locality at or near the town of Quamby Brook, northern Tasmania.
Tasmanite (7.0 cm across at its widest) from the Quamby Mudstone (Lower Permian)
of northern Tasmania.
Tasmanite (~2.1 cm across) from the Quamby Mudstone (Lower Permian) of northern
Tasmania. Each golden-brown structure is a Tasmanites
microfossil. The grayish material is the surrounding mudshale matrix.
Sample generously donated by the University of
TasmaniaÕs School of Earth Sciences.