The word polystrate is not a standard geological term, and is found most often in creationist materials.
In geology, such fossils are referred to as upright fossils, trunks, or trees. Brief periods of rapid sedimentation favor their formation. Upright fossils are typically found in layers associated with an actively subsiding coastal plain or rift basin, or with the accumulation of volcanic material around a periodically erupting stratovolcano. 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. 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.[4] For example, geologists such as John W. F. Waldron and Michael C. Rygel have argued that the rapid burial and preservation of polystrate fossil trees found at Joggins, Nova Scotia was the direct result of rapid subsidence, caused by salt tectonics within an already subsiding pull-apart basin,[5] and resulting rapid accumulation of sediments. Contrary to the claims of creationists, these sedimentary basins are considerably smaller than the state of Texas. The specific layers containing polystrate fossils occupy only a very limited fraction of the total area of any of these basins.[6][7]
Polystrate fossil - Wikipedia
Geologists have also found that some of the larger polystrate trees found within Carboniferous coal-bearing strata show evidence of regeneration after being partially buried by sediments. In these cases, the polystrate trees were clearly alive when they were partially buried by sediments. The accumulated sediment was insufficient to kill the trees immediately because of their size. As a result, some of them developed a new set of roots from their trunks just below the new ground surface.[4] Until they either died or were overwhelmed by the accumulating sediments, these polystrate trees would likely continue to regenerate by adding height and new roots with each increment of sediment, eventually leaving several meters of former "trunk" buried underground as sediments accumulated.
Polystrate fossil - Wikipedia
And to be more thurough in the explenation
According to scientists, polystrate fossils are just fossils which were buried in a relatively short time span either by one large depositional event or by several smaller ones. Geologists see no need to invoke a global flood to explain upright fossils. This position of geologists is supported by numerous examples, which have been found at numerous locations, of polystrate, upright, trees completely buried within either late Holocene or historic sediments. These polystrate trees demonstrate that conventional geologic processes are capable of burying and preserving trees in an upright position such that in time, they will become fossilized.
Polystrate fossil - Wikipedia
Does this solve your un-informa-tism
Edited by frako, : No reason given.