The Tommy L. Phillips coal ball collection at the University of Illinois contains a voluminous quantity of Carboniferous coal balls (permineralized peat) and coal ball peels from around the world, with the bulk hailing from the Illinois Basin. Contained in the collection are a variety of sample sets and maps, including 'vertical sections' where the collection locality was sampled vertically using visually determined coal ball zones as sampling levels. Observations of the derivative peels from these vertically stacked coal ball zones, reveals a variety of compactional and degradational state patterns, as well as cross-cutting relationships within individual coal ball specimens. Key points include, evidence of multiple compactional states within a single coal ball, compacted versus uncompacted root systems within various vertical sections, rare marine burrowing into the top of some coal ball masses, mine scale and outcrop distribution patterns that show map-scale variation ranging from linear and channel like accumulations to amorphous masses, and the lateral geometry of a single coal ball concretionary area showing small, individual sub-decimeter coal balls at the fringes, aggregating into larger lenticular masses towards the center. The cross-cutting relationships and various distribution patterns may help to provide broad constraints on the relative timing of coal ball formation for a given coal ball deposit, and additionally suggest possibly complex and/or a spectrum of geochemical histories for different coal ball localities.
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