Coal swamps

The mineral matter and the ash in coal have often been informally classified as inherent (stemming from the plant material in the coal swamp) or as adventitious (added after the deposition of the plant material in the swamp). This classification is misleading and difficult to apply, especially for those minerals that are contemporaneous with the peat swamp but were not incorporated by the plants. 

Sources of Sulfur in Coal and Oil. The major coal beds of eastern North America are of Pennsylvanian age. During that time, there was a constantly fluctuating sea level across flat lowlands over the North American interior. Coal was formed just before the onset of marine conditions, so that coal swamp forests occurred on broad lands along or near the sea shore. Thicker sections accumulated on the more rapidly subsiding Illinois and Forest City basins and in the Appalachia fireland basin (14). 

Western coals were formed during the Cretacious and Tertiary. During those time periods, the region was emergent land, so the coal swamps were in contact with fresh rather than saline waters. 

According to the autochthonous, in situ theory of coal formation, peat beds and subsequently coal were formed from the accumulation of plants and plant debris in place. According to the allochthonous theory, the coal-producing peat bogs or swamps were formed from plant debris that had been transported, usually by streams or coastal currents, to the observed burial sites. 

Coal, a black mineral of vegetable origin, is believed to have come from the accumulation of decaying plant material in swamps during prehistoric eras when warm, wet climatic conditions permitted rapid growth of plants. The cycles of decay, new growth, and decay, caused successive layers of plant material to form and gradually build up into vast deposits. The accumulation of top layers of this material and of sedimentary... 

The formation of mineral coal is not an instantaneous process, but is an extremely lengthy one, spread over an extended period. Millions of years ago, when the temperature was moderate and rainfall was heavy, vegetation was quite thick, especially in the low-lying areas of the Earth. Coal-forming plants probably grew in swamps, and as the plants died, their debris gradually formed a thick layer of matter on the swamp floor. Over a prolonged period, this matter hardened into a substance called peat. The peat deposits became buried under sand or other mineral matter. As the mineral matter accumulated, some of it turned... 

Spackman, W. Cohen, A. D. Given, P. H. Casagrande, D. J. "The Comparative Study of the Okefenokee Swamp and the Everglade s-Mangrove Swamp-Marsh Complex of Southern Florida, Field guidebook printed for Geol. Soc. Amer. Pre-convention field trip, 15-17 November 1974 (subsequently published by Coal Research Section, Pennsylvania State University, 1976), 403 pp. 

Methane is produced by bacteria under anaerobic conditions in wet environments such as wetlands, swamps and rice fields. It is also produced in the stomachs of cattle and by termites. Typical anthropogenic sources are from fossil fuels such as coal mining and as a byproduct in the burning of biomass. The latter sources are considerably heavier in C than the former. Recently, Keppler et al. (2006) demonstrated that methane is formed in terrestrial plants under oxic conditions by an unknown mechanism. The size of this methane source is stiU unknown but it might play an important role for the methane cycle. 

Hydrocarbons are obtained primarily from coal and petroleum, both formed when plant and animal matter decays in the absence of oxygen. Most of the coal and petroleum that exist today were formed between 280 and 395 million years ago. At that time, Earth was covered with extensive swamps that, because they were close to sea level, periodically became submerged. The organic matter of the swamps was buried beneath layers of marine sediments and was eventually transformed to either coal or petroleum. 

Coal is Interspersed as individual beds within other types of sedimentary rock beds, including sandstones, limestones, clays, shales, and mixtures of these materials. The plant material that ultimately became coal deposits was accumulated in upland bogs, coastal or near-coastal swamps, or della plains. It is envisioned that the conditions were somewhat similar to the conditions existing today in the Okefenokce Swamp in Georgia or the Everglades of Florida. These areas may have varied from a few acres in several hundreds of square miles (hectares/square kilometers). Hence, the variation in ihe occurrence of coal as we find it today. 

The plant precursors that eventually formed coal were compacted, hardened, chemically altered, and metamorphosed by heat and pressure over geologic time. It is suspected that coal was formed from prehistoric plants that grew in swamp ecosystems. When such plants died, their biomass was deposited in anaerobic, aquatic environments where low oxygen levels prevented their reduction (rotting and release of carbon dioxide). Successive generations of this type of plant growth and death formed deep deposits of unoxidized organic matter that were subsequently covered by sediments and compacted into carboniferous deposits such as peat or bituminous or anthracite coal. Evidence of the types of plants that contributed to carboniferous deposits can occasionally be found in the shale and sandstone sediments that overlie coal deposits. 

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