National Geologic Map Database
Map showing publication footprint
  • Usage in publication:
    • Cedar Lake Formation
  • Modifications:
    • Areal extent
  • AAPG geologic province:
    • Williston basin

Megathan, E.R., 1987, Silurian Interlake Group; a sequence of cyclic marine and freshwater carbonate deposits in the central Williston basin, IN Fischer, D.W., ed., Fifth international Williston basin symposium; core workshop volume: North Dakota Geological Survey Miscellaneous Series, 5th International Williston Basin Symposium, Grand Forks, ND, June 14-17, 1987, no. 69, p. 59-88., Prepared in cooperation with North Dakota and Saskatchewan geol. societies


Is one of eight formations of Interlake Group. Name extended in subsurface from southern CN into the central Williston basin of ND where it consists of dolomite that may be barren to rich in skeletal marine fossils. Considered to be a thick sequence [but total thickness in report area not stated.] Fossils include massive, tubular, branching and bulbous stromatoporoids, solitary and colonial rugose corals, crinoids, bryozoans, brachiopods, mollusks. Dolomitization has masked the structure of many of the fossils. Bedding features include lamination, contortion, bioturbation, current bedding, and accretionary reef fabric. Overlies Guernsey Formation (extended into the basin from CN). Upper contact revised in that Cedar Lake is overlain by the newly named Grondale Formation of Interlake Group. History of stratigraphic nomenclature chart. Silurian age.

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

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

Asterisk (*) indicates published by U.S. Geological Survey authors.

"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).

Slash (/) indicates name does not conform with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005). This may be explained within brackets ([ ]).