Mixed-Layer Illite-Smectite in Pennsylvanian-Aged Paleosols: Assessing Sources of Illitization in the Illinois Basin

Mixed-layer illite-smectite (I-S) from a new set of Pennsylvanian-aged Illinois Basin underclays, identified as paleosols, are investigated to assess the impact (1) regional diagenesis across basin and (2) extent which ancient environments promoted illitization during episodes soil formation. Interpretations Reichweite Ordering ?° 2? metrics applied X-ray diffraction patterns suggest that most I-S in paleosols likely product burial diagenetic processes not formation processes. Acid leaching abundant coal units hydrothermal brines mechanisms may have impacted Pennsylvanian paleosols. These findings also shallowly buried basins (<3 km) such still promote clay mineral alteration through pathways if maximum occurred deep past remained within window for extended periods time. More importantly, since many pedogenic minerals been geochemically reset illitization, sources should be better understood paleosol utilized paleoclimate reconstructions.