Sunday, July 11, 2021

The Short Life and Unnecessary Death of the Devils Lake Formation

Edward Oscar Ulrich was previously featured here as one of the main players in the brachiopod noir "The Great Brachiopod Caper of 1892", on the side of the "victors". Decades later, though, he seems to have come out on the short end with a formation he named from one of the more geologically notable areas in Wisconsin: Devil's Lake in the Baraboo Range. Devil's Lake itself is more than worthy of a post in its own right, but for the moment I'll just plant that seed for future reference.

A brief bit of exposition is in order, though. The Baraboo Range is an exhumed area of early Paleozoic topography, with a core of Proterozoic Baraboo Quartzite. The range is elliptical and oriented east-west, with a north range and a more complete south range; during the Cambrian and Early Ordovician, before it was buried, the range was oriented north-south instead of east-west. Similar to Taylors Falls, where basalt withstood the advancing seas, the ancient quartzite of the Baraboo Range formed islands in the Cambrian sea. Also like Taylors Falls, there is a conglomeratic sandstone that formed adjacent to the resistant Precambrian rocks, only in this case the conglomerate is composed of material shed from Baraboo Quartzite rather than Midcontinent Rift basalt. It is this flanking sedimentary unit, well-exposed near Devil's Lake, that Ulrich named the Devils Lake Formation.

The Devils Lake Formation first popped up in Ulrich (1920), as a name in a table. It did not get a proper description until Thwaites (1923), where it was described as a "more or less glauconitic sandstone" with quartzite pebble conglomerate. Ulrich (1924) added a little more, emphasizing the well-developed conglomerate found on the flanks of the quartzite ridges and noting its presence in nearby Parfrey's Glen. Never the subject of much discussion, the Devils Lake Formation was laid to rest in the literature following Wanenmacher et al. (1934). The authors regarded the formation as a geological chimera, because it was not coherent in terms of biostratigraphy. (It was also mixed up in Ulrich's doomed effort to establish the Ozarkian and Canadian periods between the Cambrian and Ordovician, which didn't help its reputation.) In light of the push to define formations by their rocks rather than their fossils that came about not long after Wanenmacher et al. (1934), this is a fatally flawed argument: formations live or die on the distinctiveness of their lithology, not because of how many trilobite zones they span. The Devils Lake Formation should have been expected to span multiple zones, because it represents unusual depositional conditions that persisted adjacent to the range beginning with the arrival of the Cambrian seas until the range was buried during the Ordovician. However, going back and resurrecting the Devils Lake Formation was not a high priority for anyone.

The plot thickened when in 1990 Clayton and Attig named a new formation, the Parfreys Glen Formation, for quartzite conglomerate and conglomeratic sandstone found adjacent to the quartzite ridges of the Baraboo Range. The new unit encompasses the same kinds of rocks as the Devils Lake Formation and is present in the same areas. It is hard to avoid the conclusion that the Parfreys Glen Formation is the Devils Lake Formation under a new name. Oddly, even though all of the papers mentioned above are referenced several times in the 1990 publication, nowhere is the term "Devils Lake Formation" used, not even to dismiss it. (This is not the only example of something about Devil's Lake geology going missing; for some reason the Cambrian fossils found near the lake are basically absent from the literature since Resser 1942. For a further "devilish" aspect, no two geologic maps of the area map the Cambrian rocks in exactly the same places around the lake; compare Wanenmacher 1932 [in Raasch 1935], Dalziel and Dott 1970, Clayton and Attig 1990, Baumann and Abrams 2013, and Stewart and Stewart 2021.)

Conglomerate in Parfrey's Glen; is it the Parfreys Glen Formation, or the Devils Lake Formation in disguise? Found on Wikimedia Commons, taken by user Wackybadger. CC BY-SA 3.0.


Baumann, S. D. J., and M. J. Abrams. Geologic map of Devils Lake, Sauk County, Wisconsin, United States, T11N R6E and R7E. Midwest Institute of Geosciences and Engineering, Chicago, Illinois. Publication M-072013-1A. Scale 1:12,000.

Clayton, L. and J. W. Attig. 1990. Geology of Sauk County, Wisconsin; with a section about the Precambrian geology by B. A. Brown and an appendix naming the Rountree Formation by J. C. Knox, D. S. Leigh, and T. A. Frolking. Wisconsin Geological and Natural History Survey, Madison, Wisconsin. Information Circular 67. Including geologic map, scale 1:100,000.

Dalziel, I. W. D., and R. H. Dott, Jr. 1970. Geology of the Baraboo District, Wisconsin: a description and field guide incorporating structural analysis of the Precambrian rocks and sedimentologic studies of the Paleozoic strata. Wisconsin Geological and Natural History Survey, Madison, Wisconsin. Information Circular 14. Scale 1:62,500.

Raasch, G. O. 1935. Paleozoic strata of the Baraboo area. Kansas Geological Society, 9th Annual Field Conference Guidebook:405–415.

Resser, C. E. 1942. Fifth contribution to nomenclature of Cambrian fossils. Smithsonian Miscellaneous Collections 101(15).

Stewart, E. K., and E. D. Stewart. 2021. Geologic map of the Baraboo 7.5-minute quadrangle, Sauk County, Wisconsin. Wisconsin Geological and Natural History Survey, Madison, Wisconsin. Open-File Report 2021-02. Scale 1:24,000.

Thwaites, F. T. 1923. The Paleozoic rocks found in deep wells in Wisconsin and northern Illinois. The Journal of Geology 31(7):529–555.

Ulrich, E. O. 1920. Major causes of land and sea oscillations. Journal of the Washington Academy of Sciences 10(3):57–78.

Ulrich, E. O. 1924. Notes on new names in table of formations and on physical evidence of breaks between Paleozoic systems in Wisconsin. Transactions of the Wisconsin Academy of Sciences, Arts and Letters 21:71–107.

Wanenmacher, J. M. 1932. The Paleozoic strata of the Baraboo area, Wisconsin. Dissertation. University of Wisconsin, Madison, Wisconsin.

Wanenmacher, J. M., W. H. Twenhofel, and G. O. Raasch. 1934. The Paleozoic strata of the Baraboo area, Wisconsin. American Journal of Science (5th series) 28(163):1–30.

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