Sunspots and wildfires: An ~300 m.y.a record of solar cycle effects in bituminous coal, Appalachian Basin
|Location||International Geological Congress,oslo 2008|
|Holding Date||29 September 2008|
Coal petrographic data collected at 0.33 mm depth intervals through the trimacerite-rich, Westphalian D Lower Clarion coal seam in western Pennsylvania indicate that marked periodicity exists within the distribution of inertite ("fossil charcoal") in the seam. Spectral analyses by Fast Fourier Transform demonstrate that three peaks in inertite distribution with depth are statistically significant. Using a peat-to-coal compaction ration of 3.6:1 (as calculated through microscope study of column samples), and an average peat accumulation rate of 2 mm per year, the dominant periodicity of the inertite data has been determined to occur on time scales ranging from 12 to 60 years.
Sea-level change, subsidence, compaction, climate and floral productivity variations have been considered as potential forcing mechanisms for the observed high frequency inertite distribution. The high frequency of inertite periodicity in the Lower Clarion coal seam is best attributed to periodic emergence and oxidation (probably combustion) of the original mire surface. Furthermore, emergence is best described as a function of climate variations, and appears to occur on time scales comparable to those established for solar activity/radiance fluctuations. Periodic drought-driven lower-than-normal water-table levels provided a setting within the original mire through which forest and wetland wildfires could easily combust peat.