Edited by James E. Palmer and Russell R. Dutcher - University of ...

- u w l' ' . WEBSTERFigure I L-18. Generalized distribution and thickness of Anvil Rock Sandstone in southern Illinois, southwestern Indiana, and westernKentucky. (From Hopkins, 1958, with additional data in Eagle VaEIey compiled by Trask.)sheet phase generally has gradational upper and lowercontacts.Hopkins (1 958) gives the following interpretationfor depositional environment of the Anvil Rock Sandstone.He thought that at least the lower part of thesheet phase was deposited first during a regressionwhen sand brought to the nearshore area was spreadlaterally by weak currents. During the regression,minor channels extended over the coastal plain. At theperiod of maximum regression, extensive erosion occurredwith development of the major channels anddowncutting into underlying coal. Transgression followingthis stage of downcutting caused the channelsto aggrade. The gradational contact with the overlyingshale beneath the Bankston Fork Limestone is interpretedby Hopkins to indicate slight reworking orintroduction of new sand during this later transgression.At this time the coal being produced at Eagle SurfaceMine of Peabody Coal Company is the Herrin (No.6) Coal Member of the Carbondale Formation (equivalentto part of the Westphalian D in Western Europe).This coal seam accounted for about 70 percent of the1977 coal production in Illinois; 25 percent came fromthe Springfield and Harrisburg (No. 5) Coal Members.The No. 6 Coal constitutes 42 percent of the total coalresources in the state. This coal occurs in and has beenmined in all but the westernmost part of the lllinoisBasin Coal Field. The No. 5 Coal also is present over awide area of the state, and in this area it occurs com-0 to 145 feet (27 to 44 m) below the No. 6Coal at this mine is generaliy 43 to 45inches (110 to 115 em) thick, and usually it can beseparated into three benches by two shale partings,each 0.75 to 1 inch (2 to 3 cm) thick. Commonly theupper parting is about 8 inches (28 cm) down from thetop of the seam, and the lower one is about 28 inches(70 cm) below the upper parting. In certain local areasin this vicinity, the seam is split by a clastic wedge ofsandy siltstone or mudstone commonly more than 2feet thick, and the beds are cornplex!y deformed.The coal is predominantly bright clarain, containingnumerous 0.1 to 0.15 inch (2 to 4 mm) layers ofvitrain and thinner fusain and other duller layers.Pyrite is conspicuous as nodules along the bedding andalong cleat surfaces representing 1 to 5 percent of theseam, depending on the location. The beds overlyingthe coal are typically gray or dark gray, thinly laminatedshale (Anna Shale Member) except where theyhave been cut on and replaced by the Anvil RockSandstone.Coal in lilinois is ranked as high-volatile bituminousin composition. Here in the Eagle Valley Syncline,the coal is of the highest rank of this group, highinous. Within a distance of 10 to 50km) from here, the coals are lower inrank, high volatile bituminous; beyond, they gradeFIELD TRIP 9/ROAD LOG