# Boscobel complex

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{{Use mdy dates|date=December 2022}}
{{Infobox rockunit
| name           = Boscobel complex
| image          = Boscobel_complex_Luck_Stone_Quarry_pit_VGFC_2022.jpg
| caption        = Bottom of Luck Stone Quarry showing interfingering of gray gneiss and white leucogranite
| type           = [metamorphic](/source/Metamorphic_rock) and [igneous](/source/Igneous_rock)
| age            = Paleozoic
| period         = 
| prilithology   = granite
| otherlithology = gneiss
| namedfor       = Boscabel Ferry
| namedby        = Shaler and Woodworth, 1899<ref name=SW1899/>
| region         = [Virginia](/source/Virginia)
| country        = [United States](/source/United_States)
| coordinates    =
| unitof         =
| subunits       =
| underlies      = 
| overlies       =
| thickness      =
| extent         =
| area           =
| map            =
| map_caption    =
}}

The '''Boscobel complex''' (originally "Boscabel bowlder beds") is unit of interlayered [granite](/source/granite) and [gneiss](/source/gneiss) within [Goochland](/source/Goochland_County%2C_Virginia) and [Powhatan](/source/Powhatan_County%2C_Virginia) Counties, Virginia.  The area had been mapped as the ''Petersburg Granite'' in 1970 by B. K. Goodwin.<ref>Goodwin, B. K., 1970.  ''Geology of the Hylas and Midlothian quadrangles, Virginia''.  Virginia Division of Mineral Resources, Report of Investigations 23.  Map Scale: 1:24,000.</ref>

The complex is mapped in a single, fault-bound area ([horst](/source/Horst_(geology))) approximately 9 km long.  It lies on the west side of the [Richmond Basin](/source/Richmond_Basin), a Mesozoic [rift basin](/source/Eastern_North_America_Rift_Basins), and on the east margin of the ''Goochland Terrane'', a section of the [Piedmont](/source/Piedmont_(United_States)) of Virginia that is tectonically distinct from the surrounding rocks.  It is quarried for aggregate at the Boscobel Plant of the Luck Stone Corporation, near [Manakin](/source/Manakin-Sabot%2C_Virginia).<ref name=VGFC2022>David B. Spears, Nick H. Evans, Patrick C. Finnerty, and Katherine E. Lang, 2022. ''The Goochland Terrane Revisited – Insights from Recent Mapping, Geophysics, and Geochronology''.  The 52nd Annual Virginia Geological Field Conference, November 11–12, 2022.  (Fieldtrip guidebook)</ref><ref>{{Cite journal|last1=Bartholomew|first1=Mervin J.|last2=Tollo|first2=Richard P.|title=Northern ancestry for the Goochland terrane as a displaced fragment of Laurentia|journal=Geology|volume=32|issue=8|doi=10.1130/g20520.1|year=2004|page=669|bibcode=2004Geo....32..669B}}</ref>

== Description ==
The Boscobel complex's consists of two interfingered lithologies, a two-[mica](/source/mica) [gneiss](/source/gneiss) and a [leucogranite](/source/leucogranite).  The gneiss is foliated and quartzofeldspathic with [quartz](/source/quartz), [plagioclase](/source/plagioclase), [muscovite](/source/muscovite), [biotite](/source/biotite), and [chlorite](/source/chlorite), with some alkali [feldspar](/source/feldspar).  The leucogranite is primarily quartz and feldspar with some [garnet](/source/garnet).<ref>Spears, D. B. and Occhi, M. E., 2020, ''Geologic map of the Midlothian quadrangle, Virginia'': Virginia Division of Geology and Mineral Resources Open-file Report 2020-05, 1:24,000-scale map.</ref>

<gallery heights="200px" mode="packed">
Boscobel Complex sample VGFC 2022.jpg|Sample of the leucogranite
Boscobel Complex sample 2 VGFC 2022.jpg|Gneiss sample
</gallery>

== Exposures ==
The type section, originally called the "Boscabel bowlder beds" when the extent of the horst was unknown, was named from exposures at a Boscabel Ferry on the [James River](/source/James_River) near Manakin.<ref name=SW1899>Shaler, N. S., and Woodworth, J. B., 1899.  ''Geology of the Richmond Basin, Virginia'', Washington: Government Printing Office. [https://books.google.com/books?id=3XQuAAAAYAAJ Google Book]</ref>

The largest exposure is the quarry pit of the Boscobel Plant of the Luck Stone Corporation, near the type section.  An overlook above the quarry is available to the public.
[[File:Geology of the Richmond Basin 1899 Plate XXI.jpg|thumb|left|240px|1899 photograph of the type section along the [Southern Railway](/source/Southern_Railway_(U.S.))<ref name=SW1899/>]]

==References==
{{reflist}}

Category:Triassic geology of Virginia
Category:Geologic formations of Virginia
Category:Granite formations

{{Virginia-geologic-formation-stub}}

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Adapted from the Wikipedia article [Boscobel complex](https://en.wikipedia.org/wiki/Boscobel_complex) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Boscobel_complex?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.