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Individual layers containing upright trees and individual buried forests occupy only a very small fraction of the total area of Yellowstone National Park.Geologists have recognized innumerable fossil soils (paleosols) throughout the strata containing upright fossils at Joggins in Nova Scotia, in the Yellowstone petrified forests, in the coal mines of the Black Warrior Basin of Alabama, and at many other locations.The layer immediately underlying coal seams, often called either "seatearth" or "underclay", typically either consists of or contains a paleosol.In river deltas and other coastal-plain settings, rapid sedimentation is often the end result of a brief period of accelerated subsidence of an area of coastal plain relative to sea level caused by salt tectonics, global sea-level rise, growth faulting, continental margin collapse, or some combination of these factors. This type of volcanism generates and deposits large quantities of loose volcanic material as a blanket over the slope of a volcano, as happened during the 1991 eruption of Mount Pinatubo.Both during and for years after a period of volcanism, lahars and normal stream activity wash this loose volcanic material downslope.
Upright fossils typically occur in layers associated with an actively subsiding coastal plain or rift basin, or with the accumulation of volcanic material around a periodically erupting stratovolcano. Rygel have argued that the rapid burial and preservation of polystrate fossil trees found at Joggins, Nova Scotia directly result from rapid subsidence, caused by salt tectonics within an already subsiding pull-apart basin, and from the resulting rapid accumulation of sediments.
Typically, this period of rapid sedimentation was followed by a period of time - decades to thousands of years long - characterized by very slow or no accumulation of sediments. The upright fossil trees of the Gallatin Petrified Forest in the Gallatin Range and the Yellowstone Petrified Forest at Amethyst Mountain and Specimen Ridge in Yellowstone National Park, occur buried within the lahars and other volcanic deposits comprising the Eocene Lamar River Formation as the result of periods of rapid sedimentation associated with explosive volcanism.
This term is typically applied to "fossil forests" of upright fossil tree trunks and stumps that have been found worldwide, i.e.
in the Eastern United States, Eastern Canada, England, France, Germany, and Australia, typically associated with coal-bearing strata.
Within Carboniferous coal-bearing strata, it is also very common to find what are called Stigmaria (root stocks) within the same stratum.