Re: Fold nappe upside down limb
width
Not as large but beautifully exposed in 3D in a succession of
deep glaciated canyons is the Lamoille Canyon nappe in the
Ruby Mountains, Nevada. The nappe has a maximum overturned limb
width 9 km perpendicular to strike (length >22 km).
Structurally above it (with opposite vergence) is an example of a
small nappe derived by rotation of an initially upright fold: the
Soldier Creek nappe, the upright root of which is sheared out upward
into the sheath-shaped nappe where caught up in extensional
shear zone (overturned limb 4 km wide perpendicular to
transport).
The inverted limb of the basement-cored, thrust-floored
Scanlon nappe in the Mojave Desert of California tracks >45 km
along strike.
Keith
Howard, K.A., 1980, Metamorphic
infrastructure in the northern Ruby Mountains, Nevada,
in Crittenden, M.D., Jr., Coney, P.J., and Davis, G.H. eds.,
Cordilleran metamorphic core complexes: Geological Society of
America Memoir 153, p. 335-347.
Howard, K.A., 1987, Lamoille
Canyon nappe in the Ruby Mountains metamorphic core complex,
Nevada, in Hill, M.L., ed., Cordilleran section of the
Geological Society of America: Geological Society of America
Centennial Field Guide v. 1, p. 95-100.
MacCready, Tyler, Snoke, A.W.,
Wright, J.E., and Howard, K.A., 1997, Mid-crustal flow during Tertiary
extension in the Ruby Mountains core complex, Nevada: Geological
Society of America Bulletin, v. 109, p. 1576-1594.
Howard K.A., John, B.E., and
Miller, C.F., 1987, Metamorphic core complexes, Mesozoic ductile
thrusts, and Cenozoic detachments: Old Woman Mountains -
Chemehuevi Mountains transect, California and Arizona, in
Davis, G.H. and Vandendolder, E.M., eds., Geologic diversity of
Arizona and its margins: Excursions to choice areas:
Arizona Bureau of Geology and Mineral Technology Special paper 5, p.
365-382.
Howard, K.A., 2002, Geologic map
of the Sheep Hole Mountains 30' x 60' quadrangle, San Bernardino and
Riverside Counties, California: U.S. Geological Survey map
MF-2344, 2 sheets, http://pubs.usgs.gov/mf/2002/2344/,
(1:100,000).
--
Keith A. Howard
Scientist Emeritus
U.S. Geological Survey, MS 973
Menlo Park, CA 94025
U.S.A.
phone 1-650-329-4943
fax 1-650-329-5133
