Webster and Hageman—Buenellus chilhoweensis n. sp. (lower Cambrian Chilhowee Group)
Appendix: Localities Little River Gap area,Walland, TN
Original locality of Walcott and Keith.—Walcott (1890) and Keith (1895) reported finding fossils on the east side of Little River Gap, which is a river gorge cut through Chilhowee Mountain near the town of Walland (Fig. 3.1). This site was subsequently referred to as “USNM Locality 17” by Resser (1938; the Little River Gap locality was also mentioned by Resser [1933, p. 746], but was erroneously stated to be in Virginia). The fauna definitely known from USNM Locality 17 consists of Buenellus chilhoweensis n. sp. (Fig. 4.8), the arthropod Isoxys chilhoweanus, the bradoriid Indota tennes- seensis, and the hyolith figured by Resser (1938, pl. 4, fig. 31). It is also possible that the brachiopods mentioned by Keith (1895) were sourced from this locality, although some of or all those specimens might have been collected from the Murray Gap area. The precise location of the original fossil-bearing site at
Little River Gap is not known. Labels on the specimens denote only that the locality was at “the east end of the Little River Gap, Chilhowee Mountain, Tennessee” (Neuman and Nelson, 1965, p. D29). This vagueness, combined with the failure of sub- sequent investigators to discover additional fossils in the area (e.g., King et al., 1952, p. 15), also led to uncertainty over the stratigraphic provenance of the original fossils. Although the fossils were stated to have been collected from the Murray Shale (Keith, 1895), King et al. (1952) described the roadside section at Little River Gap and noted that the Murray Shale has been cut out of the section by faulting. They (King et al., 1952, p. 15, 17, table 5) concluded that, at Little River Gap, the fossil-bearing “Murray Shale” of Keith (1895) is actually the Helenmode Formation. The same conclusion was reached by King and Ferguson (1960) and by Neuman and Nelson (1965, p. D28, D29). The classic Little River Gap roadcut (Fig. 3.1, Locality
LRG; GPS coordinates 35°43.914’N, 083°48.936’W) was examined by the present authors in 2016. Our observations are
congruent with the geologic map presented by King et al. (1952, fig. 5). The outcrop on the northeast side of the old road (on the east side of Little River) comprises an intermittently exposed stratigraphic section from the Cochran Formation to the Nebo Quartzite. The Hesse Quartzite is perhaps also exposed at the east end of the outcrop, but interpretation of the stratigraphy is complicated by a fault and by soil cover. The Nebo Quartzite contains several shale intervals, each about 20− 30cm thick, that resemble the lithology of the Murray Shale, but the Murray Shale itself appears to be absent from the roadcut. Trace fossils occur in thin-bedded shale-siltstone and fine sandstone beds of the Nebo Member, but no body fossils were observed. Given that all other occurrences of Buenellus chilhoweensis n. sp. and Isoxys chilhoweanus are in the Murray Shale (herein; Walcott, 1890), we conclude that the fossils assigned to USNM Locality 17 were sourced from the Murray Shale at a site on Chilhowee Mountain close to (but not at) the roadside exposure on the east side of Little River Gap.
New Localities on Chilhowee Mountain.—Several fossil- bearing exposures in the Chilhowee Group were discovered by
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SJH on Chilhowee Mountain to the northeast of the classic Little River Gap roadcut. This series of exposures is on privately owned land, maintained as the Three Sisters Conservation Area (managed by Blackberry Farm). We stress that access to the localities requires expressed permission from the landowners: the locality information presented here is published with their approval. The exposures are in the banks of an unmarked jeep trail that winds through several switchbacks to reach the summit ridgeline of Chilhowee Mountain (Fig. 3.1). The trail crosses over much of the Chilhowee Group stratigraphy, from the Cochran Formation (at the foot of the trail) to the Hesse Quart- zite (forming the summit ridgeline). The stratigraphically lowest exposure of interest is in the
Nichols Shale (Fig. 3.1, Locality CM1; GPS coordinates 35° 44.649’N, 083°48.892’W). Several person-hours of collecting and splitting of ~100 kg of bulk samples from the shale to silt- stone and fine-grained sandstone at this site yielded several trace fossils. The absence of macroscopic body fossils despite the suitable lithology for their preservation is consistent with assignment of the Nichols Shale to a pre-trilobite age (Begadean Series), in accord with previous studies (Hageman and Miller, 2016). This provisional age assignment could be tested with further collecting effort within this stratigraphic unit, particu- larly if acritarchs could be extracted. Further up the mountainside lie exposures of the ridge- and
cliff-forming Nebo Quartzite. Cross-bedding and Skolithos burrowing were observed within that unit, but no serious effort to look for body fossils was made due to the discouraging lithofacies. Higher still, several meters of shale within the low- ermost part of the Murray Shale are exposed in close juxtapo- sition to the top ledge of the Nebo Quartzite (Fig. 3.1, Locality CM2; GPS coordinates 35°44.817’N, 083°48.446’W). That shale yielded bradoriids, indeterminate carbonaceous filaments, and abundant trace fossils. The bradoriid specimens have yet to be identified, but their stratigraphic position within the lower few meters of the Murray Shale is consistent with the occurrence of Indotes tennesseensis at Murray Gap (Laurence and Palmer, 1963; Wood and Clendening, 1982). Seven specimens of Buenellus chilhoweensis n. sp. and
abundant hyoliths were recovered from an ~0.5m thick interval within the upper portion of the Murray Shale at an exposure located further east and up the hillside (Fig. 3.1, Locality CM3; GPS coordinates 35°45.076’N, 083°48.030’W). Cliffs of the cross-bedded, Skolithos-bearing Hesse Quartzite form the rid- geline summit above this locality. The exact stratigraphic dis- tance of the trilobite-bearing interval below the base of the Hesse Quartzite cannot be measured due to soil cover, but hill- side topography suggests that the distance is on the order of 10− 20 m. The lithology of the trilobite-bearing interval is a friable shale and siltstone that weathers into chips.
Murray Gap Area
Original locality of Walcott and Keith.—In his description of Isoxys chilhoweanus, Walcott (1890, p. 626) reported that some of the fossils were sourced from “near Montvale Springs” on Chilhowee Mountain. Keith (1895, p. 3) also noted “the crest of the mountain above Montvale Springs” as a source for fossils from the Murray Shale. This indicates that the fossils were
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