USGS Professional Paper 1697 - Alaska Resources Library
USGS Professional Paper 1697 - Alaska Resources Library
USGS Professional Paper 1697 - Alaska Resources Library
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plates that exhibit magnetic anomalies 5 and 6. The spreading<br />
occurred after the marine-arc volcanism in this area that<br />
formed the Bowers (bw) and Shirshov (sh) Ridges in the<br />
middle Eocene and early Miocene.<br />
(7) Intense tectonic disruption occurred in the western part<br />
of Aleutian-Wrangell arc, along the western Aleutian megathrust<br />
(AL), as a result of the transform coupling between the<br />
Pacific and North American Plates (Geist and others, 1988). A<br />
complex array of strike-slip, extension, and rotation structures<br />
formed in this area (Scholl and others, 1992, 1994; Vallier and<br />
others, 1994). In the area of the Bering Sea, a thick sedimentary<br />
prism continued to form in the Aleutian-Bowers Basin<br />
(atb), which overlies a fragment of accreted Kula oceanic plate<br />
(Plafker and Berg, 1994; Scholl and others, 1992, 1994).<br />
(8) Tectonic escape (crustal extrusion) of terranes continued<br />
to occur along major dextral-slip faults, including the<br />
Denali (DE), Iditarod-Nixon Fork (NF), Kaltag (KA), and<br />
companion faults (Scholl and others, 1992, 1994). Dextralwrench<br />
basins continued to form in association with the<br />
dextral-slip faults and were rapidly filled with continental<br />
72<br />
168<br />
oa bs<br />
oc<br />
bs<br />
bs<br />
168<br />
BR<br />
km<br />
KY<br />
NY<br />
GD<br />
al<br />
156<br />
oa<br />
co<br />
KY<br />
om ia<br />
K KO<br />
yk<br />
km<br />
kw DE<br />
kw<br />
TG<br />
AP<br />
Arctic<br />
Ocean<br />
AL<br />
CG<br />
144<br />
co<br />
yk<br />
K<br />
km<br />
at<br />
at wr<br />
om kn<br />
KA<br />
TI<br />
om<br />
oa<br />
om<br />
cn DE<br />
BR<br />
kh CG<br />
at<br />
oa<br />
CO<br />
oa<br />
CG<br />
d<br />
PW<br />
PW<br />
132<br />
PW<br />
56<br />
AL<br />
oa<br />
52<br />
72<br />
Pacific<br />
Ocean<br />
FO<br />
gg<br />
YAK<br />
NAC<br />
om<br />
TE<br />
cn<br />
CG<br />
156 144<br />
Middle Tertiary Metallogenic Belts (20 to 10 Ma) (figs. 125, 126) 273<br />
PAC<br />
oa<br />
TI<br />
gg<br />
om<br />
sediments. Dextral displacement continued farther east along<br />
major dextral-slip faults such as the Denali (DF), Iditarod-<br />
Nixon Fork (NF), and Kaltag (KA) Faults. Estimates of total<br />
Cenozoic displacements along the Denali and Tintina faults<br />
are between 400 and 500 km each (Nokleberg and others,<br />
1985; Plafker and Berg, 1994; Monger and Nokleberg, 1996).<br />
These and companion dextral-slip faults probably extended<br />
into the area of the Bering Sea.<br />
(9) The Pacific oceanic plate (PAC) continued to move<br />
northwestward. Along the Aleutian megathrust (AL) plate<br />
convergence continued to vary from oblique-orthogonal in the<br />
east to oblique to transform in the west.<br />
(10) The Aleutian-Wrangell continental-margin arc<br />
was associated with mainly oblique subduction of the northern<br />
edge of Pacific oceanic plate (PAC) along the Aleutian<br />
megathrust (AL) to form the Prince William terrane (PW).<br />
During northward migration, the Yakutat terrane (YA) started<br />
to underthrust the Prince William terrane along the eastern part<br />
of the Aleutian megathrust. Forming in the Aleutian-Wrangell<br />
continental-margin arc in southern <strong>Alaska</strong> was the <strong>Alaska</strong><br />
cr<br />
om<br />
48<br />
cr<br />
QC<br />
FO<br />
sk<br />
bo<br />
NR<br />
PI<br />
cn<br />
0<br />
64<br />
tt<br />
kl<br />
cn<br />
oa<br />
cr<br />
NAC<br />
132<br />
MIDDLE TERTIARY THROUGH PRESENT<br />
METALLOGENIC BELTS<br />
AP - <strong>Alaska</strong> Peninsula & Aleutian Islands<br />
OC - Owl Creek<br />
PC - Pinchi Lake<br />
ns<br />
FS gg PA<br />
OC<br />
gg<br />
oa<br />
cr<br />
BR ns<br />
sb<br />
PR<br />
HO<br />
OC<br />
JFR<br />
56<br />
JF<br />
SZ<br />
cn<br />
WA<br />
cr<br />
cn<br />
ca<br />
800 km<br />
om<br />
ca<br />
oa<br />
0 800 mi<br />
Figure 126. Generalized map of major middle Tertiary through Present metallogenic belts, overlap assemblages, and tectonically<br />
linked subduction-zone or accretionary-wedge terranes for <strong>Alaska</strong>, Canadian Cordillera, and adjacent offshore areas. Refer to text<br />
for description of metallogenic belts. Adapted from Nokleberg and others (1997b, 1998). Refer to figure 62 for explanation.<br />
PC<br />
kl<br />
CC<br />
ns<br />
FO<br />
48
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