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For three hundred years geologists and paleobotanists have been attempting to describe the process that deposited plant material that formed Carboniferous coal beds. Autochthonous and allochthonous explanations in the early Nineteenth Century showed how scientific methodology becomes involved in coal interpretation. Autochthonous modelers used the paleobotany-strata-petrology-environment method to argue that coal is a terrestrial swamp deposit. Allochthonous modelers used the petrology-strata-paleobotany-environment method to describe coal as a subaqueous deposit. The two methodologies are best displayed at the end of the Nineteenth Century in the consensus autochthonists versus the French School allochthonists. Three depositional models have been offered for the origin of coal: (1) peat swamp model, (2) drift model, and (3) floating mat model. Many paleobotany questions about lycopods and tree ferns had not been solved at the end of the Nineteenth Century, but the "floating mat model" offered a very robust path to direct research. Unfortunately, at the beginning of the Twentieth Century when the uniformitarian paradigm prevailed, the floating mat model was intentionally suppressed. Now new data from coal petrology indicate that Carboniferous coal is detrital having accumulated underwater, not as a terrestrial swamp deposit. New data and methodology from paleobotany (Sanders and Austin, 2018) show lycopsids and tree ferns were capable of forming living floating mats able to support the trunks. Paleobotany of coal plants should now be best understood as supporting a floating raft that deposited the detritus that now forms Carboniferous coal beds. We present here for the first time a three-hundred-year historical survey of the notion that coal accumulated from floating vegetation mats.

Exposed along the southeast fl ank of the Colorado Front Range are rocks that beautifully illustrate the interplay of sedimentation and tectonics. Two major rangebounding faults, the Ute Pass fault and the Rampart Range fault, converge on the Garden of the Gods region west of Colorado Springs. Cambrian through Cretaceous strata upturned by these faults reveal in their grain compositions, textures, and bedforms radically different styles of sedimentation. The Cambrian/Ordovician marine transgressive deposits appear to have come to rest on a passive and tectonically inactive craton. In contrast, coarse-grained Pennsylvanian/Permian marine deposits of the Fountain Formation and Lyons Sandstone reveal deposition by suspension and tractive currents in a very dynamic tectonic setting. These styles are contrasted with the alternating eustatics of the Western Interior Seaway which led to the local Cretaceous section. Finally, the powerful imprint of the Laramide orogeny is evident in the sandstone dikes of Sawatch Sandstone which are found within the hanging wall of the Ute Pass fault.

A review of the history of the debate on origin of Carboniferous coal shows the priority that autochthonists have placed on paleobotanical data and interpretation. New data and methodology are offered here for interpreting the paleobotany and paleoecology of dominant Carboniferous coal plants: tree lycopsids and the tree-fern Psaronius. Lycopsid and tree-fern anatomies are characterized by air-filled chambers for buoyancy with rooting structures that are not suited for growth into and through terrestrial soil. Lycopsid development included boat-like dispersing spores, establishment of abundant buoyant, photosynthetic, branching and radiating rhizomorphs prior to upright stem growth, and prolonged life of the unbranched trunk prior to abrupt terminating growth of reproductive branches. The tree fern Psaronius is now understood better than previously to have had a much thicker, more flaring, and further spreading outer root mantle that formed a buoyant raft. Its increasingly heavy leaf crown was counterbalanced by forcing the basally rotting cane-like trunk and attached inner portion of the root mantle continually deeper underwater. Lycopsids and tree-ferns formed living floating mats capable of supporting the trunks. Paleobotany of coal plants should now be best understood as supporting a floating raft that deposited the detritus that now forms Carboniferous coal beds.