PRELIMINARY BEDROCK MAP AND GEOLOGY OF THE NORTH WHITEFIELD QUADRANGLE, MAINE

The North Whitefield quadrangle, located south and east of Augusta, is predominantly underlain by three northeasterly-trending belts of rock. From northwest to southeast these belts of rock are made up of the Nehumkeag Pond Fm., the Cape Elizabeth Fm. and the Bucksport Fm. A belt of complexly deformed felsic igneous rocks with subordinate amounts of metasedimentary rocks is located near the contact between the Bucksport and Cape Elizabeth Fms.

The Nehumkeag Pond Fm. is a lithologically heterogeneous unit dominated by biotite + plagioclase ± hornblende ± quartz ± garnet gneisses with subordinate amounts of sillimanite-bearing schist and epidote-bearing amphibolite. The contact between the Nehumkeag Pond Fm. and the Cape Elizabeth Fm. to the southeast is not well exposed. However, in one location a meter-scale lens of a dense, rusty-weathering garnet-biotite schist correlative with the Wilson Cove Fm. was found at the contact between these two units.

The Cape Elizabeth Fm. is a light to dark gray, medium to coarsely crystalline muscovite-biotite-quartz-feldspar granofels/gneiss interlayered with coarsely crystalline biotite-muscovite-feldspathic schist. Several small bodies of the Crummet Mountain member of the Cape Elizabeth Fm. are present within the map area. These rocks are moderately rusty weathering, medium to coarsely crystalline, graphitic, garnet-staurolite-andalusite schists with discontinuous, intensely folded quartz veins containing coarse, pink andalusite. The rocks in the Cape Elizabeth belt are variably mylonitic and contain kinematic indicators that suggest these rocks have undergone significant dextral shear.

The contact with the rocks of the Bucksport Fm. to the southeast is poorly exposed. The Bucksport is characterized by calc-silicate gneisses interlayered with biotite-plagioclase-quartz granofels and hornblende-plagioclase gneisses.

The rocks in the southeastern portion of the quadrangle are intruded by weakly to penetratively deformed, heterogeneous, felsic igneous rocks. These variably sheared igneous rocks contain numerous inclusions of elongate bodies of metasedimentary rocks of the Bucksport Fm. and K-feldspar megacrystic rocks of the Lincoln shonkinite. Similar complexly deformed rocks have been recognized along strike to the northeast.