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Geologic Unit: Bertram
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Map showing publication footprint
  • Usage in publication:
    • Bertram Formation
  • Modifications:
    • Revised
  • AAPG geologic province:
    • Iowa shelf
    • Wisconsin arch
Publication:

Witzke, B.J., Bunker, B.J., and Rogers, F.S., 1988, Eifelian through lower Frasnian stratigraphy and deposition in the Iowa area, Midcontinent, U.S.A., IN McMillan, N.J., Embry, A.F., and Glass, D.J., eds., Devonian of the World; proceedings of the 2nd international symposium on the Devonian System; Volume I, Regional synthesis: Canadian Society of Petroleum Geologists Memoir, 14, p. 221-250.


Summary:

Revised in that Bertram is assigned as the lower formation of the Wapsipinicon Group (rank raised). Lies on an eroded Silurian surface. Underlies [Coggon] Member of Otis Formation of Wapsipinicon. Is the most restricted formation of the group being limited to an area 35 to 45 km north of Plum River fault zone in east-central IA (Iowa shelf) and adjoining northwest IL (Wisconsin arch). Dominated by vuggy dolomite that can be laminated to sandy, and extensively calcitized. Sandy shale occurs commonly in basal part. Dolomite is locally fractured, brecciated, or conglomeratic. Deposited in a restricted aquatic to terrestrial environment. Age unknown. Shown on chart as early Middle Devonian, Eifelian age. Nomenclature chart. Graphic sections.

Source: GNU records (USGS DDS-6; Denver GNULEX).


For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.

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