79 Coal Geology (Posters)

Monday, 3 November 2003
8:00 AM - 12:00 PM

AN ALTERNATIVE PROPOSAL TO COAL GENESIS IN THE EARLY PERMIAN OF THE PARANÁ BASIN, BRAZIL

Program: Technical Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

According to Ager (1993), Pennsylvanian coal deposits in North America and Europe were formed in delta fronts, in relatively low latitudes, with heavy development of forests and low tonnage vegetation, and extended from the Southern Appalachians to the Donetz Basin in the Ukraine and Russia. Ager (1993) points to the rapid alternation of the marine seams in the coal's sedimentary cycles, through deltaic sandstones to coal seams, which suggests a short-duration process in the coal's genesis, even for thicker seams. The presence of standing trees, still preserved in life position, in coal measures, according to Ager (1993), can show how rapidly they were buried in a rapid rush of sediment. The proposal of an alternative genesis for the coal deposits considers Mutti et al.’s (1999) model, which links the turbidites from passive-margin basins to flows that originated in the continent during catastrophic floods. It is considered that, in human terms, almost every flood is catastrophic and the ones discussed by Mutti et al. (1999) have big proportions, in which energy liberated and tonnage of sediments are inconceivable with respect to Lyell's gradualism. Mutti et al. (1999), correlating turbidites and fluvial sediments as "fluvial-turbiditic sedimentation", consider catastrophic floods to be the main process in this kind of sedimentation. They studied many occurrences of hummocky cross stratification (HCS), interpreting them as generating shelf lobes, associated with catastrophic flood-dominated deltas.

Glasspool (2003), in his studies of seams near Ogies in the Witbank Basin, part of the Permian Ecca Group, South Africa, mentions the atypical profile of coal deposition, that appears to be allochtonously (or hypautochthonously) deposited, strongly suggesting aqueous transport. The linking of those ideas with the presence of HCS in the high ash yield Paraná Basin coal seams, which have a close association with diamictites, leads us to an alternative proposal to coal genesis for these coals. Petrographic analysis had shown a dominance of vitrinite plus inertinite (>90%), with rare sporinite (1%). Along with the other depositional evidence, this low percentage of sporinite supports an allochtonous origin for the Paraná Basin coals.