Deltaic and fluvial sedimentation processes are recognized as primary dispersal mechanisms that operated to contribute sediments to the Chesterian depositional area in Illinois, Indiana, and Kentucky.

As the fluvial cycle was initiated, erosion channels were incised into the underlying strata. Clastic sediments were delivered to the depositional area by the Michigan River system. The channel fill may be traced from its outcrop into the subsurface and across Kentucky more than 300 miles. The fill may be projected, with considerable success, into areas where few tests have been drilled. Successful projections have been accomplished by making isopachous maps of the channel fill. Once the distributary network is outlined, a direct relation is apparent between the channel system and hydrocarbon accumulation within the Bethel Sandstone. The recently discovered Midland, St. Charles, Barnsley, Luzerne, and Sharon School fields occur within the distributary network.

All of these fields are combination traps. They are restricted to the channel fill and are localized by subsequent structural deformation.

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