The St. Meinrad Coal Member (Pennsylvanian)—Reference Sections from Spencer County, Indiana

Abstract

The purpose of this study is to (a) specify locations in Indiana that can serve as reference sections for the St. Meinrad Coal Member (Pennsylvanian) and (b) acquire more data to better correlate this coal with its equivalents in the Illinois Basin. The work focused on 1) a core from Indiana Geological and Water Survey drill hole (SDH) 537, latitude 38.180721 N, longitude 86.83895 W); and 2) an outcrop of the St. Meinrad Coal Member (latitude 38.147652 N, longitude 86.808903 W), both in Spencer County, Indiana. The borehole was drilled in November 2023 and the core is archived at the Indiana Geological and Water Survey Core Research and Teaching Repository, Bloomington, Indiana, USA. The St. Meinrad Coal Member was encountered at a depth of 44.25 to 48.45 ft (13.49 to 14.77 m), with a total coal thickness of 4.20 ft (1.28 m). On a whole-seam basis, the coal has an ash yield of 1.27 wt % and is 3.92 wt % in total sulfur. Petrographically, the coal consists of moderate amounts of vitrinite (77.12 vol %), liptinite (15.84 vol %) and inertinite (7.04 vol %). Palynologically, the coal is dominated by lycopsid tree spores (74.12 vol %), with reduced amounts of small lycopsid (13.4 vol %) and tree fern (6.14 vol %) spores. Small fern (0.9 vol %) and calamite (4.17 vol %) spores are uncommon to rare, as is cordaite pollen (0.96 vol %). The outcrop location has a coal thickness of 3.15 ft (96 cm). In outcrop, the coal is relatively clean in the middle part and is enriched in mineral matter at the top and bottom parts of the seam. The coal is underlain by claystone. Palynologically, the coal has similar spore assemblage to that documented from the core. The common occurrence of Endosporites globiformis and other stratigraphically diagnostic taxa in both locations warrant assignment of the St. Meinrad Coal Member to the early Atokan NG (Microreticulatisporites nobilis - Endosporites globiformis) miospore zone of the Illinois Basin, which correlates with the early Duckmantian strata of western Europe and Middle-Late Bashkirian strata worldwide. The palynologic data also indicate that, within the Illinois Basin, the St. Meinrad Coal Member is coeval with the Hawesville and Bell coal beds in western Kentucky.