Mineral Resources On-Line Spatial Data
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|Name||Silurian - Ordovician Frontenac Formation|
|Geologic age||Silurian - Ordovician|
|Original map label||SOf|
|Comments||The Frontenac, since its naming, has been a subject of disagreement concerning its lithologic components, stratigraphic position, and structural presentation. The author and his colleagues (Bothner, Pollock, and Moench) consider the Frontenac to be Silurian and to lie beneath the Seboomook Group. Canadian geologists reverse the stratigraphic order and place the Frontenac in the Devonian and above units correlated with the Seboomook. The formation is informally divided into lower and upper portions. In most exposures the lower portion consists of thickly bedded, light bluish-gray to greenish gray, fine- to medium-grained, quartzofeldspathic, variably calcareous wacke. Wacke beds are typically interbedded with thinly bedded, dark gray mudstone slate. The upper portion, similar in bedding and composition to the lower portion, is generally non-calcareous and lacks, for the most part, the volcanic and hypabyssal intrusive rocks. Underlies Late Silurian and Early Devonian Ironbound Mountain Formation. (ME058) Unit description from USGS GEOLEX website (ME078). W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite GS - Greenschist facies Protolith Q - Interbedded pelite and sandstone|
|Primary rock type||graywacke|
|Secondary rock type||slate|
|Other rock types|
Sedimentary > Clastic > Sandstone > GraywackeW - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite GS - Greenschist facies Protolith Q - Interbedded pelite and sandstone
Metamorphic > Metasedimentary > Metaclastic > Slate (Bed)W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite GS - Greenschist facies Protolith Q - Interbedded pelite and sandstone
Digital bedrock data downloaded from Maine Office of GIS in September 2005 from http://apollo.ogis.state.me.us/catalog/catalog.asp?state=2&extent=cover#bedrock Bedrock units table (publication date 11/15/2002) downloaded from same site. Permission to redistribute these data granted by Dr. Robert Marvinney, State Geologist of Maine, in September 2006.
Osberg, P. H., Hussey, A.M., and Boone, G. M., 1985, Bedrock geologic map of Maine: Maine Geological Survey, Dept. of Conserv., scale 1:500,000.
|Geographic coverage||Oxford - Piscataquis - Somerset|
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