01_pedlar_dike_4 Metabasalt dike in Pedlar Formation gneiss. Roadcut near Little Devils Staircase Overlook. This is a feeder dike that probably developed about 570 to 700 Ma ago when Rodinia was rifting and the Iapetus Ocean was developing. Magma that reached the surface contributed to the Catoctin Formation.
02_pedlar_granodiorite_gneiss_4 Granodiorite gneiss in roadcut near Little Devils Staircase Overlook. Granodiorite gneiss contains quartz with a higher concentration of plagioclase (calcium and sodium) feldspar than potassium feldspar and iron and magnesium minerals that make it darker than granite gneiss. Lichens cover the surface in areas. This was originally granodiorite that formed as plutonic rock at the base of the Greenville Mountains that formed during the formation of Rodinia. Pressure and heat deep in the Earth and under metamorphic forces associated with formation of Pangea melted the rock and altered it chemically and physically to its current form.
03_pedlar_dike_basalt_4 Wet metabasalt dike in roadcut near Little Devils Staircase Overlook. There are geologist bore holes. Samples were probably take for chemical analysis and radiometric aging.
04_pedlar_bandedgneiss_roadcut_16 Granite gneiss showing foliation. Granite gneiss contains quartz, high potassium feldspar and low concentration of iron and magnesium minerals. Foliation is easy to see. It is lighter in appearance than granodiorite gneiss. This is from the Skyline Drive road cut next to Bacon Hollow Overlook.
05_pedlar_granitegneiss_7 Highly weathered granite gneiss at Hazel Mountain Overlook.
06_pedlar_granite_gneiss_garnet_7 Close-up of highly weathered granite gneiss at Hazel Mountain Overlook. Foliation of the rock can be seen. The polygonal red structures with sharp borders are garnets. Garnets form after the original rock is under heat and pressure during metamorphism, and rock chemicals are modified to a more stable form.
