The Precambrian Geology of the Reading 15' Quadrangle

1/2-minute quadrangle abundant Alsace Manor Antietam Lake appear areas augite beds biotite Birdsboro blende gneiss Boyertown quadrangle carbonate rocks chlorite clay coarse composition correlation crystalline rocks diabase dike east elongation of quartz exposed exposures feet feldspar feldspathic Feldspathic sandstone field relations fine-grained Fleetwood quadrangle float folds foliation Fraser Frush Valley gabbroic gneiss gneissic structure grains granules graphitic gray Hardyston Formation Hardyston ridge igneous indicated interpretation Irish Mountain jasper light-gray limbs lower conglomerate magnetic intensity metasediments microcline migmatites mile Miller Neversink Mountain northeast northern New Jersey occurs Oley Furnace Oley Valley orthoclase Orthoquartzite outcrops overthrust overturned pegmatite Penn percent perthite petrographic pinite plagioclase Precambrian Precambrian crystallines pyroxene quarry quartz and feldspar quartz diorite quartz diorite gneiss quartzite rangle Reading Hills Reading quadrangle sericite shales sheared slaty cleavage slightly feldspathic South Mountain Stony Creek Mills Stose and Jonas texture thrust typical granitic gneiss usually weathered xenoliths