USGS Visual Identifier

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GEOLEX database

Geologic Unit: Islesboro

Publication:
Rankin, D.W. (editor), Chiarenzelli, J.R., Drake, A.A., Jr., 
   Goldsmith, Richard, Hall, L.M., Hinze, W.J., Isachsen, Y.W., 
   Lidiak, E.G., McLelland, James, Mosher, Sharon, Ratcliffe, 
   N.M., Secor, D.T., Jr., and Whitney, P.R., 1993, Proterozoic 
   rocks east and southeast of the Grenville Front, IN Reed, 
   J.C., Jr., and others, eds., Precambrian; conterminous U.S.: 
   Geological Society of America, The Geology of North America, 
   The Decade of North American Geology (DNAG), v. C-2, p. 
   335-461.
Usage in Publication:
Islesboro Formation*

Modifications: Geologic Province: Dominant Lithology:
 Age modified
 New England province
 

Summary:
Islesboro Formation is of Late Proterozoic age. Consists of interbedded pelite, siltstone and sandstone, limestone and dolomite, conglomerate, rhyolite, and basalt. D.B. Stewart (1990, oral commun.) considers Islesboro to be distal facies of North Haven Greenstone, Ellsworth Schist and schist at Columbia Falls (eastern coastal ME).
Source: GNU records (USGS DDS-6; Reston GNULEX).


Publication:
Stewart, D.B., in press, Geology of northern Penobscot Bay, 
   Maine: U.S. Geological Survey Miscellaneous Investigations 
   Series Map, I-__.
Usage in Publication:
Islesboro Formation*

Modifications: Geologic Province: Dominant Lithology:
 Revised
 Age modified
 New England province
 

Summary:
Age of Islesboro Formation changed to Late Proterozoic(?) and Ordovician(?). Some carbonate rocks previously designated as Coombs Limestone Member are reassigned to Seven Hundred Acre Island Formation (new name). Because the carbonate sequences within Islesboro Formation have different stratigraphic positions, variable thickness and lithology along strike, and may resemble each other locally, continued regional use of the name Coombs Limestone Member is unwarranted.
Source: GNU records (USGS DDS-6; Reston GNULEX).