3 the Significance of the Union Chapel Mine Site

3 Buta, R. J., Rindsberg, A. K., and Kopaska-Merkel, D. C., eds., 2005, Pennsylvanian Footprints in the Black Warrior Basin of Alabama. Alabama Paleontological Society Monograph no. 1. THE SIGNIFICANCE OF THE UNION CHAPEL MINE SITE: A LOWER PENNSYLVANIAN (WESTPHALIAN A) ICHNOLOGICAL KONZENTRAT- LAGERSTÄTTE, ALABAMA, USA ADRIAN P. HUNT1, SPENCER G. LUCAS1, and NICHOLAS D. PYENSON2 1New Mexico Museum of Natural History and Science, 1801 Mountain Road NW, Albuquerque, New Mexico, 87104, USA 2Department of Integrative Biology & Museum of Paleontology, University of California, 1101 Valley Life Sciences Building, Berkeley, California 94720 USA ABSTRACT: The Union Chapel Mine site (Steven C. Minkin Paleozoic Footprint Site) is located in Walker County, Alabama. The fossil-bearing horizon is in the Mary Lee coal zone (above the Mary Lee coal bed) of the Pottsville Formation (Early Pennsylvanian: Westphalian A). It yields diverse and extensive vertebrate and invertebrate ichnofaunas as well as plant and arthropod body fossils. The significance of the tracksite can be evaluated based upon size, ichnotaxonomy, taphonomy, paleoecology, ichnofacies, geography, biogeography, stratigraphy, biostratigraphy, paleoenvironment, preservation, education, sociology and history. The Union Chapel site is globally significant in most of these categories. INTRODUCTION Mine site (Allen, 2005; Buta and Minkin, 2005; Atkinson et al., 2005). Another less significant, and slightly older The Union Chapel fossil site (now known as the locality is the Number 11 Mine of the Galloway Coal Steven C. Minkin Paleozoic Footprint Site) is a very Company near Carbon Hill (Aldrich and Jones, 1930). large fossil site in northern Alabama of Early Pennsyl- The track-bearing interval at the Union Chapel Mine vanian age. It yields an abundant fossil fauna that in- is in sandstone-shale couplets interpreted as tidal cludes tetrapod tracks (Minkin, 2000; Haubold et al., rhythmites (Pashin, 2003, 2005). Invertebrate ichnotaxa 2003, 2005), fish traces (Martin, 2003a), invertebrate in these strata include abundant xiphosuran trails trace fossils (Rindsberg and Kopaska-Merkel, 2003, (Kouphichnium), insect feeding traces (Treptichnus), 2005; Lucas and Lerner, 2005), plant megafossils burrows (Arenicolites), as well as less common arthro- (Dilcher et al., 2005) and arthropod body fossils pod walking and feeding traces (Rindsberg and Kopaska- (Atkinson, 2005). This site is obviously significant, but Merkel 2003, 2005; Lucas and Lerner, 2005; Uchman, how does it compare with other fossil sites of similar 2005). Fish swimming traces (Undichna) are also age and scope? The purpose of this paper is to answer present, as are the tracks of small amphibians that question. (Batrachichnus) and small captorinomorph reptiles The majority of the significant fossils from the Union (Notalacerta and Cincosaurus) (Haubold et al., 2003, Chapel Mine are tetrapod tracks. Therefore, we estab- 2005; Martin, 2003a). Indeed, tracks assigned to lish a set of categories by which the significance of tet- Cincosaurus so dominate the footprint assemblage that rapod tracksites can be assessed, and evaluate the Union local collectors refer to the track-bearing strata at the Chapel Mine against them. Union Chapel Mine as the “Cincosaurus beds” (e.g. , Minkin, 2005). Larger tetrapod tracks include UNION CHAPEL MINE LOCALITY Attenosaurus subulensis, Alabamasauripus aldrichi, and Dimetropus isp. (Hunt et al., 2004). Although the The partially abandoned Union Chapel Mine is lo- Union Chapel Mine also contains large (>15 cm long) cated in Walker County, Alabama, about 48 km north- and fragmentary plant debris and three body fossils of west of Birmingham (Fig. 1). The track-bearing hori- insects and arachnids (Dilcher et al., 2005; Atkinson, zon at the Union Chapel Mine is in the Mary Lee coal 2005), the site otherwise yields a fossil record that con- zone, just above the Mary Lee coal bed of the Pottsville sists entirely of trace fossils. There are also brachio- Formation (Early Pennsylvanian: Westphalian A) pods at the locality, but they probably derive from a (Pashin, 2005; Fig. 2)(Fig. 1). The majority of different stratigraphic horizon (Pashin, 2005). ichnofossil and other specimens were collected by mem- bers of the Alabama Paleontological Society and the Bir- UNION CHAPEL MINE AS A LAGERSTÄTTE mingham Paleontological Society on the surface of “spoil piles” that consist of rock from the overburden of the The term Lagerstätte was introduced by Seilacher Mary Lee coal bed. During an 18-month period, more to refer to fossil localities that display exceptional pres- than 1200 slabs containing both vertebrate and inverte- ervation in quality, quantity and diversity, after the Ger- brate ichnofossils were salvaged from the Union Chapel man word for “motherlode” (Seilacher, 1970; Seilacher 4 Lagerstätten are distinguished by the quality of preservation (Seilacher, 1990). The Union Chapel Mine has the characteristics of a Konzentrat-Lagerstätte because of the abundance of fossils, although we are not aware of this term having been previously applied to an ichnological assemblage. How- ever, the diversity of taxa of ichnofossils and body-fossils is relatively low, as is the overall representation of phyla. In addition, although there are instances of ex- quisite preservations, such as the insect wings (Atkinson, 2005), the majority of the fossils are invertebrate and tetrapod trace fossils, and these are dominantly undertracks, and, significantly, there is not extensive preservation of soft tissue (Seilacher, 1970, 1990; Hunt et al., 2004; Haubold et al., 2005). Thus, Union Chapel does not qualify as a Konservat-Lagerstätte. SIGNIFICANCE OF TERRESTRIAL ICHNOFOSSIL LOCALITIES Size Large sample sizes of any fossil are important for a variety of reasons. This is largely because the variabil- ity of the morphology of fossil species, and particularly FIGURE 1. Map of Alabama showing location of Union Chapel ichnospecies, is usually very poorly understood. A large Mine and generalized stratigraphy of the Pottsville Formation sample has implications for most of the following cat- showing location of Mary Lee coal zone and track horizon. egories, not only because of sample size (e.g., ichnotaxonomy, taphonomy) but also because of public impact (education, sociology). et al., 1985; Seilacher, 1990). This term has since been Ichnotaxonomy overused, and arguably only about a dozen fossil localities in the fossil record merit such designation (Selden Tracksites can, by virtue of large sample size or and Nudds, 2004). These would include famous sites significant individual specimens, provide for a greater such as the Jurassic Solnhofen quarries of Germany, understanding of existing ichnotaxa or reveal new the Cambrian Burgess Shale of British Columbia and ichnotaxa. The Robledo Mountain tracksites from the the Chengjiang Biota of Yunnan Province, China. Lower Permian of southern New Mexico acted as a However, there are a large number of Carbonifer- “Rosetta Stone” for the understanding of global Per- ous localities that have been “designated” as mian tetrapod ichnotaxonomy (Haubold et al., 1995; Lagerstätten, including the Gaskohle of Germany Hunt et al., 1995b; Lucas et al., 1995; Haubold, 1996). (Fritsch, 1899), Montceau-les-Mines in France (Rolfe The Robledo Mountain tracksites are important for et al., 1982), Granton “shrimp-bed” in Scotland (Briggs ichnotaxonomy because of their large sample sizes and et al., 1991) and the Castlecomer fauna of Ireland (Orr because they preserve a very large range of and Briggs, 1999). In North America, such Lagerstätten extramorphological variants, including transitional forms include the Bear Gulch Limestone of Montana (Grogan between “ichnotaxa.” In addition, in the Robledo Moun- and Lund, 2002), Buckhorn Lagerstätte of Oklahoma tains it is possible to collect a series of successive (Nutzel et al., 2000), Hamilton Quarry in Kansas underprints as well as the original tracks, which allows (Cunningham et al., 1993), Kinney Brick Quarry in New an understanding of the different morphologies displayed Mexico (Zidek, 1992), Carrizo Arroyo in New Mexico on different sedimentary layers. (Lucas and Zeigler, 2004), Joggins in Nova Scotia (Ferguson, 1988) and Mazon Creek in Illinois (Baird et Taphonomy al., 1985). Seilacher (1970) recognized two forms of The taphonomy of nonmarine ichnotaxa, particu- Lagerstätten: (1) Konzentrat-Lagerstätten (“concentra- larly tetrapods, is relatively little studied, with some tion mother lodes”) contain large numbers of fossils that notable exceptions (e. g., McKee, 1947), although there largely exclude the preservation of soft parts; these in- have been important advances in the past few years (e.g., clude shell beds and bone beds; and (2) Konservat- Gatesy et al., 1999; Gatesy, 2003; Manning, 2004). In- Lagerstätten (“conservation mother lodes”) are distin- dividual tracksites can provide information about un- guished by the preservation of soft parts and a diversity known or unstudied taphonomic contexts. For example, of taxa and include the Burgess Shale, and the German the Clayton Lake tracksite in the Lower Cretaceous of Posidenienschiefer. Thus, Konzentrat-Lagerstätten are northeastern New Mexico preserves tracks made in a distinguished primarily by quantity, whereas Konservat- very wet substrate, which produces apparently “webbed” 5 dinosaur tracks and multiple tail drags (Lockley and biochronology. Indeed, in some instances, trace fossils Hunt,

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