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hleam&gnetie latitude of Paleocene volcanic K&S of
the Cantwell Pwmatim, central Alaska
The Cantwell basin in the central Alaska Range
consists of the Cantwell Formation, which include, in
its upper part, calc-alkaline volcanic rocks and intru-
slve rocks (the Teklanika Formation of Gilbert and
others, 1976). Figure 50 shows the present distribu-
tions of the voIcanic and sedimentary rocks of the
Cantwell Formetion. Potassium-argon ages deter
mined from the extrusive and intrusive rocks, which
range from 41.8 to 60.6 rn.y., are considered to be
minimum ages at least in part (Hickman, 1974; Gilbert
and others, 1976). These ages accord with the Paleo-
cene age of plant fossils in the Cantwell Formation
(Wolfe and Wahrhaftig, 1070; Wolfe, 1972). The entire
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Cantwell Formation has been extensively folded and
faulted, and local angular unconformities occur be-
tween the volcsllic and sedimentary rocks.
We collected paleomagnetic samples at 19 sites
(area 10, fig. 44; fig. 50); each site is a separate lava
flow or welded tuff and is represented by eight Sam-
pla. Except for site 17, which was completely remag-
netized by Lightning, the pdeornagnetic data are of
high quality. The structural dips at the various locali-
ties, which range from 21' to 54O, provide an excellent
test of whether the rnegnetfzation in the rocks was
acquired before thelr deformation. The angular stan-
dard deviation of the 18 mean onsite directions is;
29.4'; after restoration of the bedded rocks to the
original horizontal by rotation around the strike, this
angular standard deviation is reduced to 12.4'~ which
is a typical value representing geomagnetic secular
variation. We conclude that the natural magnetization
/ 0 25 KILOMETERS
4'
I I I 1 I I . / I
Volcanic rocks Contact-Approximately located
Cantwell Fornation -... fault-Dotted where concealed
Sedimentary rocks .15-19 Sample site and sample numbers
Plgure SO.--Cantwell besin area, showing locations of pleomagnetic sampling sites (dots) in volcanic rocks of
the Cantwell Formation. Pre-Tertiary and pat-Paleouene rocks we not differentiated. Geology from Jones and
others (1983).