Permian outliers in Western Kentucky W. John Nelson a , Scott Elrick a, ⁎, David A. Williams b a Illinois State Geological Survey, 615 East Peabody Drive, Champaign, IL 61821, United States b Kentucky Geological Survey, 1401 Corporate Court, Henderson, KY 42420, United States abstract article info Article history: Received 30 November 2012 Received in revised form 10 July 2013 Accepted 11 July 2013 Available online xxxx Keywords: Permian Stratigraphy Kentucky Two small, down-faulted outliers of latest Pennsylvanian to Early Permian rocks occur in western Kentucky. These are the youngest Paleozoic rocks in the Illinois basin and are approximately 550 and 750 km, respectively, from strata of comparable age in the Dunkard basin and Midcontinent. A continuous core, Gil 30, was drilled in the eastern (Cap Mauzy) outlier. Fusulinids (Leptotriticies beardi) from a depth of 59.4 m were originally used as evidence for Permian age, although this species is now considered to be latest Pennsylvanian. Ostracods from above the fusulinids support a Permian age. The upper 103.6 m of Gil 30 is assigned to the Mauzy Formation and contains intervals of bedded, micritic, nodular to brecciated limestone of probable lacustrine origin, alternat- ing with marine to brackish-water clastic intervals that tend to coarsen upward, a single upward-fining sand- stone interval, and a single 2 cm thick coal layer. Older strata contain much more coal and almost no bedded non-marine limestone. The Grove Center graben, 18 km west of Gil 30, is identified on the basis of an oil-test hole electric log and coal test holes. No core samples are available, but log comparison indicates that the Grove Center outlier contains at least an additional 67 m of younger strata than Gil 30, and is a prime target for further study. Regional coalification and oil-maturation trends, along with lack of evidence for syndepositional tectonic activity in Gil 30, indicate that the Permian rocks preserved in Gil 30, and by extension the Grove Center graben, are likely representative of strata that once occupied much of the Illinois basin, probably in continuity with the Midcontinent. The Kentucky outliers, therefore, provide a link between the Midcontinent and Dunkard basins and may be important in addressing long-standing problems, such as the age of the Dunkard, and paleoclimate reconstructions. © 2013 Elsevier B.V. All rights reserved. 1. Introduction 1.1. Background The youngest Paleozoic rocks in the Illinois basin are found approx- imately midway between comparably aged strata in the Dunkard basin and Midcontinent, a distance of 550 and 750 km, respectively (Fig. 1). Kehn (1975) mapped a graben near Cap Mauzy Lake in Union County, western Kentucky where the Desmoinesian (Middle Pennsylvanian) Springfield Coal is as deep as 760 m below the surface. Following up on Kehn's find, the Kentucky Geological Survey drilled a continuously cored test hole, Gil 30, to a depth of 1841 ft (561.1 m; see map, Fig. 2). Williams et al. (1982) published the entire log of Gil 30. In February 2011 we redescribed the Gil 30 core; both a generalized (Fig. 3) and de- tailed (Fig. 9) graphic logs, are reproduced here. Three boreholes close to Gil 30 provide very good stratigraphic con- trol. These are Peabody boreholes P47 and P49, both of which were con- tinuously cored; plus the Shouse oil test hole, which has an electric log (Fig. 2). Smith and Smith (1967) published descriptions of the two Peabody cores. These three boreholes provide depth intervals and strat- igraphic context to regionally mapped marker beds in the Carbondale Formation, which the Gil 30 core did not reach. 2. Age The age of Gil 30 strata has changed over time from its initial assess- ment, as biostratigraphic correlations have been refined, and perhaps still remain in flux. How Gil 30 and the Mauzy Formation relate to the Dunkard basin and the Midcontinent is generalized in Fig. 4. Fusulinids of genus Triticites were recovered from limestone at a depth of 195 ft (59.4 m) in the Gil 30 core (Kehn et al., 1982). Douglass (1987, p. 12) named these Triticites beardi, a new species, and stated, “This form rep- resents a developmental stage similar to forms described from rocks of Early Permian (Wolfcampian) age.” However, the international Carbon- iferous–Permian boundary subsequently has been moved upward. According to Gregory P. Wahlman (written communication, 4/9/13), “the new species was most similar to Dunbarinella eoextenta Thompson 1954, which would now be referred to the genus Leptotriticites. Leptotriticites eoextenta was described from the Americus Limestone Member of the Foraker Limestone at the base of the Council Grove Group [Kansas], which is below the currently recognized conodont- International Journal of Coal Geology xxx (2013) xxx–xxx ⁎ Corresponding author. Tel.: +1 217 333 3222. E-mail address: elrick@illinois.edu (S. Elrick). COGEL-02179; No of Pages 13 0166-5162/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.coal.2013.07.010 Contents lists available at SciVerse ScienceDirect International Journal of Coal Geology journal homepage: www.elsevier.com/locate/ijcoalgeo Please cite this article as: Nelson, W.J., et al., Permian outliers in Western Kentucky, International Journal of Coal Geology (2013), http:// dx.doi.org/10.1016/j.coal.2013.07.010