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Battle Mountain
Western slope Battle Mountain.jpg
The western slope of Battle Mountain, Castleton, Virginia
Highest point
Elevation1,162 ft (354 m)
Prominence762 ft (232 m)
Coordinates38°39′26″N 78°3′36″W / 38.65722°N 78.06000°W / 38.65722; -78.06000
Geography
Battle Mountain countour map based on NASA ASTER data.jpg
A digital contour plot of Battle Mountain and Little Battle Mountain, based on digital imagery data from the NASA ASTER satellite. Processed by Thomas A. Woolman, MSc, MSc, MBA in 2015.
LocationRappahannock County, Virginia, US
Parent rangeBlue Ridge Mountains
Topo mapUSGS Massies Corner, Va.
Geology
Age of rock704,000,000 years
Mountain typeStratovolcano
Volcanic beltRobertson River Igneous Suite
Last eruption704 Mya

Contents

GeologyEdit

 
Digital terrain model of the western slopes of Battle Mountain and Little Battle Mountain, generated with data from the NASA ASTER satellite by Woolman (2016).

Battle Mountain is an igneous mountain in Rappahannock County, Virginia. The eastern slope is generally considered to reside in the unincorporated town of Amissville, Virginia while the western slope is generally considered to be within Castleton, Virginia. The entire mountain including the summit lies within private property at an elevation of 1,162 ft (354.2 m).[1]

Tectonic emplacement and geochronologyEdit

It is an extinct volcano dating to the Neoproterozoic and is approximately 704 million years old (+/- 4 million years) as dated using the U-Pb zircon crystal geochronology method. It is a unit of the Robertson River Igneous Suite[2] and is located within the Blue Ridge anticlinorium. This volcanic formation was a result of crustal extensional rifting of the eastern Laurentian margin of the supercontinent Rodinia.[3] This was the beginning of a chain of events that ultimately gave birth to the precursor Atlantic, the Iapetus Ocean at 550 Ma during the EdiacaranCambrian transition.[4]

Geochemical evolutionEdit

The volcano is composed of alkali feldspar granitic rock of the Robertson River Igneous Suite. This includes felsic complex material such as biotite, hornblende-biotite, magnetite, and alkali granitic rock including rhyolite on the eastern slopes of Battle Mountain[5] and the adjacent (and geologically related) Little Battle Mountain (elevation 937 feet).

 
Theorized original appearance of Battle Mountain at 704 million years ago by Woolman (2016). Elevation shown in meters.
 
A typical large rhyolite outcrop on the eastern slope of Battle Mountain, at an proximate elevation of 850 feet. Emily J. Woolman (aged 4, 2014) is shown for scale.
 
The eastern slope of Battle Mountain, image taken approximately three kilometers from the base on Viewtown Road, Amissville, VA.
 
A large white quartz boulder near the base of Battle Mountain on Viewtown Road in Amissville, VA. The white coloration is indicative of an extremely high SiO2 gas content from highly viscous rhyolitic lava, generated prior to a theorized (Woolman, T.A., 2016) lateral explosion event which may have occurred at 704 Ma during the Cryogenian period.
 
Quartz boulder obtained from the eastern (predominately rhyolite) slope of Battle Mountain, Amissville, Virginia. Rock hammer shown for scale. The reddish-brown mineralization in the quartz is iron (Fe).

Paleaogeographic reconstructionEdit

A unique geological feature of Battle Mountain is that the western slope outcrops are composed entirely of alkalai feldspar granite, while the eastern slope up to and including the summit is entirely rhyolitic. This provides strong evidence of a theorized lateral explosive eruption event centered on the eastern slope at approximately 704 Ma as proposed by Woolman (2016). Further mathematical geology evidence which supports this theory includes a paleaogeographic reconstruction of the mountain by Woolman utilizing artificial neural networks and Markov chain geostatistical models including period climate condition-based soil erosion rates, Kirkby's hillslope movement evolution equations and recursive biogeochemical soil erosion rates in felsic granitic conditions. The result was the digital reconstruction image shown on the left, indicating what Battle Mountain may have looked like 704 million years ago on the western slope.

 
Battle Mountain (center) from approximately eight miles south, driving north on Eggbornsville Road, Rixeyville, Culpeper County, VA.

Only known volcanic mountains in Rappahannock County, VAEdit

Battle Mountain and Little Battle Mountain are the only mountains in Rappahannock County which are known to be volcanic in origin, and are among the oldest visibly intact extinct volcanoes in Virginia. White quartz boulders and smaller fragments are common on and around Battle Mountain, a result of molten silica that was contained in the rhyolite lava and granitic magma that formed the volcano. As quartz is extremely hard relative to feldspar granite and rhyolite, it tends to remain present on the surface while the softer granite it was embedded in wears away into the soil.

Panoramic image taken from a drone at an altitude of approximately 200 meters in September, 2014. Facing north, this shows the western side of Battle Mountain and Little Battle Mountain (units of the Robertson River Igneous Suite) on the right. Aaron mountain, composed of sandstone, is visible on the left. The Blue Ridge Mountains of Shenandoah National Park are visible on the horizon. Richmond Road is visible running up through the middle of this image.

AccessEdit

The nearest unincorporated town is Amissville, Virginia at approximately 4 miles away. Access to the mountain and the summit must be negotiated with local landowners first as the mountain, including all portions of the July 1863 battlefield exists entirely on private property.

ReferencesEdit

  1. ^ "Robertson River Igneous Suite; Battle Mountain Alkali Feldspar Granite – felsite". usgs.gov. Retrieved August 21, 2016.
  2. ^ Richard P. Tollo and Sara Arav (1992). "The Robertson River Igneous Suite (Blue Ridge Province, Virginia) — Late Proterozoic anorogenic (A-type) granitoids of unique petrochemical affinity". The Robertson River Igneous Suite (Blue Ridge Province, Virginia)—Late Proterozoic anorogenic (A-type) granitoids of unique petrochemical affinity. Basement Tectonics 8 (pp. 425–441). Proceedings of the International Conferences on Basement Tectonics. 2. Springer Netherlands. pp. 425–441. doi:10.1007/978-94-011-1614-5_29. ISBN 978-94-010-4703-6.
  3. ^ Richard P. Tollo, John N. Aleinikoff (November 1, 1996). "Petrology and U-PB geochronology of the Robertson River Igneous Suite, Blue Ridge province, Virginia – Evidence for multistage magmatism associated with an early episode of Laurentian rifting". American Journal of Science. 296 (9): 1045–1090. doi:10.2475/ajs.296.9.1045. Retrieved August 22, 2016.
  4. ^ Birthdate for the lapetus Ocean? A precise U-Pb zircon and baddeleyite age for the Long Range dikes, southeast Labrador
  5. ^ Thomas A. Woolman (April 1, 2016). "A Gallium Anomaly Utilized in Palaeogeographic Reconstruction of Battle Mountain, Rappahannock County, Virginia". Transactions of the Kansas Academy of Science. 119 (2): 155–172. doi:10.1660/062.119.0206.