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Noatak Sandstom and is overlaln conformably by the
marine Lower Mississippian Kayak Shale (Brow6 and
Pessel, 1977; Mayfield and Taillew, 1978; Brosgdand
others, 1979a, b; Nelson and Grybeck, 1980). Where
the Noatak Sandstone, previously mapped as the
rnmlne basal sandstone member of the Kanayut Con-
glomerate, is missing, the Kanayut rests directly on
the marine Upper Devonian Hunt Fork Shale. The
Kanayut has been mapped together with the Noatak
Sandstone as an undivided Devonian and Mlsslssippian
unit as far west as the Misheguk Mountain quadrangle
and the south haLf of the National Petroleum Reserve
In Alaska (Mayfleld and others, 1978, 1982; ELlersieck
md others, 1978, 1082; Curtls and others, 1982). In
this area, it forms a major unit of the Brooks Range
alloehthon (Mayfield and others, 1982).
CHUKCHI
Figure 6.-Index [nap of nHusky Mountains1' and
Iulgrave Hills, western Brooks Ran , Alaska, showing
]cations of measured sections B (1 f and C (2) (see fig.
\
Although Martin (1970) applied the name
"Kanayut Conglomeraten to part of the Upper
Devonian and Lower Mississipplan sequence In the
westernmost Brooks Range, most workers have
described the sequence as consisting, in ascending
order, of the following marine units: the Hunt Pork
Shale or an unnamed fiiegrslned clastic unit, the
Noatak Sandstone, the Kayak Shale, and the Utukok
Formation (Dutro, 1953; Gryc and others, 1967;
Tailleur and others, 1967). However, as a result of our
work during the 1981 field seeson in the ''Husky
Mountains'' and Mulgrave Hills in the De Long Moun-
tains and Noatak quadrangles, we differentiate e non-
merine unlt above the Noatak Sandstone and below the
Kayak Shale that we assip to the Kanayut Conglom-
erate (fig. 7, cola A). We describe this unit hereh end
provide criteria for distinguishing it from overlying
and underlying clastic units. This assignment con firms
the transgressive-regressive conditions wlthln the
Endicoti Group noted by Tailleur and others (1967) in
the western Brooks Range and records a major offlap-
onlap cycle similar to that of the centrai and eestern
Brooks Range.
The Hunt Pork Shale, whlch crops out in the
Mullgrave Him and the "Husky Mountainsn in low hills,
consists primarily of brown phyllitic siltstone. The
162'
common presence of thin beds of ftne-grained to very
fine gcafned sandstone that are locally graded suggests
that they are thin-bedded turbidites deposited In Slope
or prodelta settings. Because of tectonic thickening
and thinning, low-grade metamorphism, and the
absence of any well-exposed complete sectiona, the
true thickness of the Hunt Pork is mown.
The Hunt Fork Shale grades upward Into the
Noatak Sandstone, whlch is probably more than 100 rn
thick. The Noatak oonsists of trough-cross-stratified
carbonate-cemented quartzase sandstone that contah
abundant red-orange-weathering carbonate concretions.
it is characterized by alternathg layera of
brown-weathering fine- to medlurn-grained sandstone
and oay-weathering commonly pebbly cmegralned
sandstone. EHoturbated silty intervals that contain
abundant mica and plmt fragments are locally present.
The sandstone beds are not organized into finingupwmd
cycles. We interpret the Noatak to represent
deposition in innershelf and shoreline environments.
The overlying Kanayut Conglomerate consists
mainly of thjnnlng- and fining-upward nuvial cycles of
conglomerate, sandstone, and shale (fig. 7, col. 3.
The lower parts of the cycles consist, in ascending
order, of channeled lightgray-weathering basal
massive or crudely parallel stratified congiomerete,
trough-rossstratified medium-bedded sandstone, and
thin-bedded fine-grained sandstone and slltstone char
acterlzed by abundant currentripple marks. The
upper parts of the cycles consist of red- or brownweathering
shale and siltstone that contain abundant
plant and root ~wlls, paleosols marked by oxidized
red, orange, or yellow horizons, and, locally, coal. The
lower, sandy pacts of the cycles, which average 5 to 7
m in thickness, represent channel, point-bar, and levee
deposlts of meandering streams; the upper, shaly parts
record deposition on adjacent flood plains. The cycles
are characterized by erosional truncation of underlying
shale and by upward fining of grain size, thlnnlng of
beds, and decrease In the amplitude of cross-strata.
The conglomerate contains clasts as large as 3 cm.
The sandstone is composed chiefly of detrital quartz
and chert grains, and has, in contrast with the Noatnk
Sandstone, a silica cement.
Local interdigitation of the Kanayut Corrglornerate
with the underlying Noatak Sandstone results in
composite cycles that contaln a middle marine unlt
which does not fine upward. Cycles I and 3 contain a
basal channeled conglomerate that is Incised lnto
underlgng shale and fines upward lnto trough-crossstratified
sandstone (fig. 7, col. g). The middle parts
of the cycles conslst of alternatmg carbonatecemented
coarser and finer layers with abundant
trough crossstratification that are identical to the
Noatak Sandstone. The upper parts of the cyclea fine
up ward from crossatratified silica+emented Pluvial
sandstone into ripple-marked siltstone and flood-plain
shale deposits containing paleosols. Cycle 2 shows a
slmllar composite cycle but lacks the basal finingupward
fluvial intervd. Cycle 4 is a typical Khnayut
fluvlal cycle. We believe that these composite cycles
represent mixed ftuvial and marine deposition, possibly
under estumine conditions, along the strandline.
The Kayak Shale, which is at least 40 rn thlck,
overlies the Kanayut Conglomerate. Its lower part
contains thin coarsening-upward cycles that consist of