11 terms

VA Geology


Terms in this set (...)

5 Virginia Regions from Right to Left
Coastal Plains, Piedmont, Blue Ridge, Valley and Ridge, Appalachian Plateua
Ancient Pedlar Gneiss formed 1.1-1.2 BYA when Granite was metamorphosed during uplift when the continental plates collided forming the towering Grenville Mountains (now eroded away)
Volcanic Breccia from Little Stony Man
Miscellaneous Sedimentary Rocks including conglomeritic sandstone, brown sandstone, and black and red mudstones/shales. These sedimentary rocks are from other deposits in the Iapetus Ocean region that were uplifted into the present-day Blue Ridge Mountains when three major tectonic plate collisions happened over a long period of time from 250- 450 MYA.
Conglomeritic Sandstone: Notice the very small rounded pebbles mixed with sand that formed this sedimentary rock between layers of basalt. This means that sediments were deposited on an underwater magma flow and then were covered by another magma flow. You can see some basalt at the bottom of the photo.
Amygdaloidal Basalt formed when minerals (quartz and iron) filled the gas vesicles that were in the basalt, millions of years after the basalt solidified.
Basalt (Greenstone) Dike in Pedlar Gneiss when magma flowed into a vertical fault in the gneiss as the plates separated about 570 MYA
1-1.1 billion year old granite with white feldspar, gray quartz, and black hornblende and pyroxene
Tiny pink garnet crystals in the ancient Pedlar formation Gneiss
Polygonal Basalt (greenstone) Columns formed as magma cooled
Greenstone = Metamorphosed Basalt (by Mr. Chanania)