Trace fossils and depositional environment of four clastic units, Upper Pennsylvanian megacyclothems, north-east Kansas

Trace fossils were collected and studied from four elastic units (Rock Lake Shale, South Bend Limestone, Stull Shale, and Tecumseh Shale) within three different megacyclothems in northeast Kansas. Forty-one different types of trace fossils arc recognized. Thirty are identified as separate ichnogenera, and three of them are new ones. Eleven less distinct forms are also described. The depositional environment for each of these four elastic units is interpreted with the aid of their trace fossils. The Rock Lake Shale is a medium to light gray shale. Trace fossils arc preserved on thin beds of lenticular silts:one or fine-grained sandstone, which are interbedded with clay. Planolites, Asteriacites, Lockeia, Cochlichnus, Didymattlichnus, Isopodichnus, Rusophycus and other arthropod traces, Curvolithus, Conostichus, Microspherichnus Hakes, ichnogen. nov., Chevronichnus Hakes, ichnogen. nov., Tomaculum, Lingulichnus Hakes, ichnogen. nov., and resting impressions are the most common trace fossils. Body fossils are rare to absent. The South Bend Limestone overlies the Rock Lake Shale. The lower part of this limestone is a medium gray, fine-grained calcareous sandstone. The most abundant trace fossils are: Arenicolites, Diplocraterion, Margaritichnus, Chondrites, Planolites, and Rhiocorallium. Common body fossils are Orthomyalina and Avicrdopecten. Study of the ichnofauna from these two units indicates that marginal marine ( ?lagoonal) conditions existed during deposition of the Rock Lake Shale. Subsequent deposition of the South Bend Limestone (its lower elastic half) is interpreted to have occurred in a tmre normal i narine environment. Trace fossils are ccmmon in the lower part of the Stull Shale. Lithologies are thin-bedded, lenticular sandstone interbedded with clay. These sediments are also flaser and wavy bedded. Common trace fossils are Asteriacites, Teichichnus, Planolites, Didymaulichnus, and gastropod trails. Channels occur near the top of the unit with a coal above them. The Stull Shale is interpreted to have been deposited in a near-shore, shallow water environment, which underwent episodes of rapid sedimentation. A local transgression can be observed within the Tecumseh Shale by the study of trace fossils. In the lower part of the unit, Planolites, Lockeia, Aulichnites, and gastropod trails are common. These trace fossils are interpreted to represent shallow water, marine conditions. In the upper part of the unit, a change in the ichnofauna is readily visible. The appearance of Diplocraterion, Arenicolites, Tigillites, Nereites, Chondrites, Neonereites biserialis, and curved burrows suggests that marine conditions were less restricted (i.e., increased water agitation) than in the lower part. No coal unit was found in the Tecumseh Shale, and all trace fossils were preserved in thin-bedded sandstone.