Geologic Studies in Alaska by the U.S. Geological Survey, 1992

4 GEOLOGIC STUDIES IN ALASKA BY THE U.S. GEOLOGICAL SURVEY, 1992
(average 600 m) southeast of Teshekpuk Lake to the range
370 to 1,300 m (average 835 m) just west of the Ikpikpuk
River. Eastward to the Meade River the average dune
length decreases to 470 m. The longest dune observed in
the entire region is 2,500 m long. Most dunes are 15 to 40
m wide. Field observations suggest that most dunes are 1
to 3 m thick. The dunes commonly merge into the tundra,
and are generally marked by a change in color of the veg-
etation (fig. 2).
U.S. Weather Bureau records show east-northeast
(ENE) as the dominant wind direction at Barrow and west-
southwest (WSW) as the secondary maximum: Black
- 7 ARCTIC OCEAN
EXPLANATION
4 Site location
~ ~ r to in text) c M
Boundary between Ardic
coostrlp1.in(north)uNl
Atcric Foothillr (d)
Figure 1. Distribution of stabilized and longitudinal and
parabolic dunes and sites mentioned in text.
(1951, p. 93) stated that "numerous oriented lakes and
dunes throughout the coastal plain show that these maxi-
mum winds are just as consistent and effective inland and
that slightly more erosion is produced by the easterly (65"
to 80") than by the westerly winds (245" to 260°)." Mod-
em blowouts (deflation hollows on pre-existing dunes) in
the region also indicate a bimodal wind regime of ENE-
WSW, with the majority of the blowouts produced by east-
erly winds. Most stabilized parabolic and longitudinal
dunes are parallel to this trend and the parabolic dunes in-
dicate a westerly sand transport. This suggests that these
late Holocene dunes formed in a wind regime similar to
the present one.
Buried organic horizons (paleosols) in the dunes and
thin sand sheets temporally equivalent to the dunes are com-
mon throughout the study area. Rickert and Tedrow's (1967)
study of several buried soils near the Meade River showed
that dune profiles usually contained several buried organic ho-
rizons, with each horizon representing a period of surface sta-
bility. However, except for one radiocarbon age discussed
below for a buried organic horizon immediately beneath a sta-
bilized dune near the lkpikpuk River, Rickert and Tedrow pre-
sented no information about the age or paleoclimatic
significance of the soils in the Meade River area.
AGE OF EOLIAN SAND MOVEMENT
Stabilization and subsequent reactivation of eolian
sand on the Arctic Coastal Plain is recorded by thin, discontinuous
paleosols. Twelve radiocarbon ages on peat
and humic sand (paleosols) from nine locations suggest
that three periods of late Holocene landscape stability
separate four episodes of dune activity (table 1). Three
sites are described here to illustrate the stratigraphy of hurnic
paleosols and eolian sand. Minimal modern soil development
at each of these sites indicates that the dunes
have been stabilized only recently.
Site 1 is a thaw lake bluff about 50 m high composed
entirely of eolian sand. An amphitheater at the top
of the bluff cuts into a small longitudinal dune that is parallel
to the main bluff face (fig. 3). The dune is about 30
m wide and 480 m long, and its top is about 1.8 m above
the adjacent ground surface. The long axis of the dune
trends N. 60" E. A paleosol composed of cryoturbated
sandy humus 25 cm thick occurs about 2.8 m below the
top of the dune (fig. 4). A sample of humus from the
lower 15 cm of this paleosol yielded a radiocarbon age of
2,290~80 yr B.P. (table 1).
At site 2, a 10-m-high thaw lake bluff truncates a
small longitudinal dune (fig. 5). The dune rises 60 to
80 cm above the adjacent ground surface and its long
axis trends N. 65" E. The dune is approximately 920 m
long and 30 m wide. A sandy paleosol 25 cm thick
occurs about 80 cm below the surface of the dune.