Ordovician - Cambrian Sawmill Formation

Ordovician - Cambrian Sawmill Formation
State Maine
Name Ordovician - Cambrian Sawmill Formation
Geologic age Ordovician - Cambrian
Lithologic constituents
Major
Sedimentary > Clastic > Mudstone (Bed)W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite; Protolith Q - Interbedded pelite and sandstone
Sedimentary > Clastic > Sandstone (Bed)W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite; Protolith Q - Interbedded pelite and sandstone
Comments Secondary unit description from USGS Geologic Names Lexicon (ref. ME078): Simplified stratigraphic column for the Islesboro-Rockport belt in eastern ME shows (ascending) Precambrian rocks of Gilkey Harbor, Islesboro Formation, Coombs Limestone, Cambrian Rockport Quartzite and Megunticook(?) Formation. Some question as to whether unit is correctly identified in this area and correlates with the type Megunticook in the St. Croix belt where unit consists of gray quartz-muscovite-biotite-andalusite-garnet schist and sparse beds of quartz-plagioclase-biotite granulite. Battie Quartzite forms a distinctive lens within the Megunticook. These rocks do not correlate with the Kendall Mountain and Woodland Formations in the Calais area, as previously thought. In St. Croix belt, underlies Penobscot Formation and unconformably overlies lower part of Jam Brook Formation; AA - Low rank amphibolite facies; AB - Medium rank amphibolite facies; AC - High rank amphibolite facies; GS - Greenschist facies; Protolith A - Pelite.
References

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.

NGMDB product
Counties Piscataquis