Logan Formation

The Logan Formation is the name given to a Lower Carboniferous (early Osagean) siltstone, sandstone and conglomeratic unit exposed in east-central Ohio and parts of western West Virginia, USA.

Stratigraphy and paleoenvironment

The Logan Formation was named by Andrews (1870) and originally described as a "buff-colored, fine-grained sandstone" above the Waverly Formation and below the Maxville Limestone. Bork and Malcuit (1979) concluded that the Logan Formation was deposited on a shallow marine shelf in a generally transgressing sea. The age of the Logan Formation has been established as early Osagean (Tn3) by the occurrences of brachiopods, ammonoids, conodonts and miospores (Clayton et al., 1998; Matchen and Kammer, 2006).

References

• LoganConglomerateWooster.jpg

  Conglomerate in the Logan Formation exposed in Wooster, Ohio, USA.

• LoganBrachiopodsWooster.jpg

  Brachiopod internal and external molds in the Logan Formation in Wooster, Ohio.

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  The bivalve Aviculopecten subcardiformis from the Logan Formation in Wooster, Ohio (external mold).

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  Bivalves (Aviculopecten) and brachiopods (Syringothyris) in the Logan Formation in Wooster, Ohio.

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  Cross-bedding and scour in the Logan Formation of Jackson County, Ohio.

• Schizodus medinaensis.JPG

  Schizodus medinaensis; a bivalve from the Logan Formation in Wooster, Ohio (internal mold).

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  Syringothyris sp.; a spiriferid brachiopod from the Logan Formation in Wooster, Ohio (internal mold).

• Syringothyris bored Wooster Carboniferous.jpg

  Syringothyris external mold with borings; Logan Formation; Wooster, Ohio.

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  Helminthopsis ichnosp.; a trace fossil from the Logan Formation in Wooster, Ohio.

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  Crinoid calyx from the Logan Formation in Wooster, Ohio, with a conical platyceratid gastropod (Palaeocapulus acutirostre) attached.