In 1964, Scott and Cobban, in their study of the Peck Creek section, noted that the top of bed 29 was "very smooth," a description not applied by them to any other bed in the Fort Hays Limestone succession. The top of bed 29 was also singled out by Barlow and Kauffman (1985, p. 201) as a distinctive surface, termed PNF-4, that could be "...traced as a regional marker..." and "...may mark a minor disconformity in the middle of the Fort Hays Limestone Member." Similarly, Kauffman and Pratt (1985, p. FRS-19, Field Reference Section) inferred that surface PNF-4 could possibly reflect "...a benthic re-circulation event and/or a regional hiatus." Our observations at Peck Creek simply confirmed that the top surface of bed 29 was unlike any other bedding surface in the Fort Hays succession, being not only very smooth, but characterized by a variety of circular depressions, of varying diameters and depths, and by oblique burrows that, in vertical section, have a spreite-like surface ornament and are filled with marl indistinguishable from the overlying bed. There is no indication that wall material from the burrow was mixed with more clay-rich material from the overlying bed. These pits and burrows were not observed by us on any other surface in the Fort Hays Limestone at Peck Creek, suggesting that it recorded an unusual geological event.
- Received 19 November 2015.
- Revision received 10 December 2015.
- Accepted 11 January 2016.