DISRUPTED COAL AND CARBONATE FACIES WITHIN 2 PENNSYLVANIAN CYCLOTHEMS, SOUTHERN ILLINOIS BASIN, UNITED-STATES

Two cyclothems contain an unusual suite of disrupted fabrics. This stu dy's interdisciplinary integration of coal maceral and sedimentologica l information offers significant new interpretations of coal-limestone interchange, both depositionally and diagenetically. Disrupted fabric s within the Herrin Coal and Providence Limestone are interpreted as r epresenting previously undocumented interactive processes between coal s and limestones. The Herrin Coal contains brecciated beds that are th e result of marine transgression over a coastal-plain mire, representi ng high-energy conditions at the swamp-beach interface. This interface has rarely been documented in detail. Peat is inherently unstable pri or to its conversion to coal, and we document this by interpreting con glomeratic beds in overlying strata. Differential compaction of Herrin peats generated subaqueous debris flows in the overlying Providence L imestone. This mechanism for syndiagenetic and early diagenetic sedime nt deformation has not been previously recognized. In addition, near-s urface and surface processes produced other disrupted fabrics in the P rovidence Limestone, such as in situ mosaic breccias, nodular fabrics, and calcrete horizons. This study also documents that stratigraphical ly adjacent, alkaline carbonate sediments were further altered by unde rsaturated acidic pore waters, derived from compacting peats during ea rly diagenesis. Our interdisciplinary approach to distinguishing and i nterpreting all of these disrupted fabrics led to a new appraisal of t he importance of depositional and postdepositional interactions betwee n coal and limestone. The presence of mire deposits can have a signifi cant influence on the thickness, distribution, and fabrics in overlyin g strata. In cyclothems, climatic and eustatic changes may control ove rall depositional patterns, but peat compaction may determine certain facies.