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Eugene Cecil LaFond.

Oceanographic measurements from the USS Nereus on a cruise to the Bering and Chukchi seas, 1947 online

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with lead. Because the small size (0.25 inch) of the wire used
to lower the coring device necessitated limiting the weight of
the sampler to less than 150 pounds, only short cores were
obtained (minimum length = 8.5 inches, maximum length = 70
inches, average length = 30 inches).

Since most of the cores taken in the Bering Sea were very
short, sandy cores, the nature of the sediment is known for
only an unfortunately short distance below the sea bottom.
These Bering Sea cores suggest a change in sedimentation
in comparatively recent times. The appearance of the upper
1 to 3 inches of the core is usually higher in color and more
loosely packed. Other texture changes from silty sand to
silt take place at varying distances below the bottom in a
number of cores. In core NEL 502 (54 fathoms), the change
occurs at about 30 inches below the bottom; in core NEL 508
(32 fathoms), the change takes place gradually at about 7 inches;
and in core NEL 513 (19 fathoms), a sharp change occurs at
10 inches. Core NEL 504 is probably too short to show any
change, and core NEL 506 shows very little change. The cores
taken at the entrance to Norton Sound show changes to coarser
sediment at about 10 to 12 inches below the bottom, then to
finer sediment below 14j inches.



In the Chukchi Sea, three of the six cores display changes
to coarser sediment from 10 to 46 inches below the sea floor.
The core taken in Kotzebue Sound shows a change to coarser
material taking place about 6 inches below the bottom. A de-
scription of the core samples is given in table III.

Bottom Photography. An attempt was made to obtain a
number of bottom photographs with the underwater camera
at almost every station occupied by the USS NEREUS. How-
ever, at only two stations were photographs obtained in which
the bottom was clearly discernible. In the Chukchi Sea near
snapper sample NEL 520, a photograph (fig. 8) showed the
bottom to be composed of sand, gravel, and minor amounts
of silt. In the Bering Strait near snapper sample NEL 557,
a photograph (fig. 9) showed the bottom to be composed of
shells, gravel, and rock. Abundant bottom-living organisms
are present. It is noteworthy that both of these photographs,
and the sediment samples obtained close by, showed a coarse
bottom in these localities. At all other stations, the bottom
water was too turbid for the camera to penetrate even when
placed only three feet from the sea floor.

Constant checking of the equipment showed that improper
functioning did not contribute to the inability to obtain good
bottom photographs. The fact that this inability was caused
by the turbid nature of the bottom water was further sub-
stantiated by lowering the equipment with the camera focused





Figure 8. Bottom photograph taken in the Chukchi Sea at
station N13 (latitude 70° N, longitude 169° W), showing coarse
and poorly sorted bottom material. Note abundant bottom-
living organisms including crab in lower center portion of the
photo.



Figure 9. Bottom photograph taken in the Bering Strait, show-
ing stony bottom with abundant bottom-living organisms. Shell
fragments are abundant, and the large pelecypod valve in
center of the photo has a sponge growing in it.



TABLE III

ARCTIC CORE SAMPLES



NEL

Sample
No.



Latitude Longitude
North West



Depth
(fathoms)



Length of

Dry Core

(inches)



Description



502 South of Pribilof Island

504 North of Pribilof Island

506 North of Pribilof Island

508 East Bering Sea

513 North Bering Sea

518 North of Bering Strait

525 North Chukchi Sea

527 North Chukchi Sea

529 North Chukchi Sea

531 North Chukchi Sea

533 North Chukchi Sea

535 East Chukchi Sea

543 Kotzebue Sound

544 Kotzebue Sound
547 Kotzebue Sound



67° 35'


169° 03'


31


20


71° 02'


168° 51'


24


24


72° 07'


169° 00'


31


70



56° 54' 170° 36' 54 32 Grey-green, well-sorted sandy silt, becoming

a little finer toward base. Molluscan fragments
scattered throughout.

57° 21' 170° 44' 43 15 Grey-green, moderately well-sorted sandy

silty sand. Molluscan fragments scattered
throughout.

58° 23' 170° 20' 37 32 Grey-green, moderately well-sorted, silty sand.

Molluscan fragments common in top 8 to 9
inches, but rarer toward bottom.

59° 21' 169° 53' 32 31 Grey-green silty sand in top 7 inches, grading

into finer grained sandy silt. Occasional mol-
luscan fragments near top of core.

63° 57' 168° 20' 19 13 Grey-green slightly silty fine sand containing

molluscan fragments in top 10 inches; changes
abruptly to dark sandy silt in basal 3 inches
of core.

Coarse greenish-grey silt containing little clay
and a few scattered molluscan fragments.

Slightly sandy coarse greenish-grey silt con-
taining minor amounts of clay.

Grey-green clayey fine-grained silt containing
a few scattered Foraminifera and molluscan
fragments.

71° 54' 168° 40' 29 49 Grey-green clayey fine-grained silt, containing

a small amount of fine sand which increases
in basal 3 inches of core.

72° 14' 168° 35' 30 20 Greenish-grey clayey silt, containing several

small and several irregular fine-to-medium
sand partings near base; occasional small mol-
lusks, Foraminifera, and fragments of uniden-
tifiable organic material.

71° 41' 168° 20' 29 40 Greenish-grey clayey silt, occasional rounded

to subrounded pebbles, and sand grains scat-
tered throughout; organic remains common,
including fragments of wood and shells, fish
scales, and occasional foraminiferal tests.

70° 39' 167° 39' 29 25 Greenish-grey sandy silt, separated 5 inches

from top by somewhat sandier parting, then
grading again to sandy silt 9Vi inches from
top, where it grades into silty sand becoming
coarser toward bottom; medium sand and peb-
bles common in basal 15 inches.

67° 50' 166° 32' 29 8Vi Greenish-grey, poorly sorted silty sand, con-

taining minor amounts of gravel, becoming
coarser toward the base; wood fragments at
bottom.

67° 07' 164° 40' 17 8Vi Greenish-grey, poorly sorted silty sand, con-

taining minor amounts of gravel, becoming
coarser toward base.

66° 21' 162° 43' 6V2 14 Greenish-grey, fine sandy silt containing oc-

casional foraminiferal tests and molluscan
fragments.



261



TABLE III (continued)
ARCTIC CORE SAMPLES



NEL

Sample
No.



Latitude

North



Longitude
West



Depth
(fathoms)



Length of
Dry Core

(inches)



Description



549 Kotzebue Sound



551 Entrance to Kotzebue Sound 67° 03' 165° 40'



562 Port Clarence



565 Entrance to Norton Sound



566 Entrance to Norton Sound



66° 43' 163° 35' 13 12 Grey sandy silt, grading 6 inches from the

top into fine to medium sand; molluscan shells
common at base of core.

16 20 Poorly sorted sand, with sizable silt and gravel

fractions grading 8 inches below top into
finer, better-sorted sand, then rapidly into
silty sand, and finally to sandy silt near the
bottom of the core; 4 inches from the top
a pebble 20 mm. in diameter occurs.

65° 18' 166° 28' 25 67 Clayey fine silt, containing occasional rounded

pebbles including one more than 6 mm. in
diameter at 2% inches from top; organisms
include mollusks, shallow water forams, and
ophiurids (6 inches and 10 inches from top).

64° 17' 165° 19' 11 12 Sandy silt, with occasionally siltier or sandier

partings in upper part, becoming progressively
sandier 10 inches from top; includes occasional
scattered molluscan fragments and foraminif-
eral tests.

64° 25' 166° 30' 14 20 Fine sandy silt, with prominent medium-to-

coarse sand partings at 5 inches and 11 inches
from top, with less prominent partings be-
tween 11 inches and HVi inches; laminations
resemble faint bedding below 11 inches; below
14Y2 inches sediment becomes finer and clay
fraction becomes noticeable.



on an object at the lower portion of the camera support and
making exposures at various levels from the surface to the
bottom. This experiment clearly showed that the transparency
of the water decreased with depth and that a highly turbid
layer was present along the bottom.

Surface-water transparency readings were obtained at
each station by recording the depth to which a white disc
30 centimeters in diameter (Secchi disc) could be seen (see
Transparency Measurements, below). Readings obtained
varied from 9 to 50 feet, average depths for coastal water.
There appeared to be no correlation between the surface
water transparency and bottom water transparency but,
wherever the snapper samples showed the bottom to consist
of fine sand or mud, a turbid layer was present near the
bottom. Thus, although phytoplankton may largely account
for the opacity of the surface water, the turbidity of the bottom
water must be due to sediment in suspension.



Mineralogy and Petrology. The mineral grains and rock
fragments were identified in a general way, using only a
binocular microscope. For this reason no attempt was made
to distinguish between the ferromagnesian minerals or, in
most instances, between the feldspars. The minerals and
rocks identified are listed in table IV.

Of the minerals identified, quartz and feldspar are almost
ubiquitous. However, they are most abundant in the north
Bering Sea and the Chukchi Sea. Pyriboles (pyroxenes and
amphiboles) and olivine are most common in the south Bering
Sea near the volcanic rock source in the Pribilof and Aleutian
Islands, but they were noted also in most of the other samples.
Of the micas, biotite is the most common, especially in the
north Bering Sea and the Chukchi Sea and near Joneau, Alaska.
A white amphibole common in the Juneau area has been iden-
tified as tremolite. Noteworthy is the abundance of magnetite
in the snapper sample NEL 567 taken just south of Unimak
Island in the Aleutians. At this location, magnetite is the
most abundant constituent of the sand comprising the bottom.
As might be expected, basalt grains are common in the
south Bering Sea, becoming less common toward the north
where they are mixed with grains of granite and quartzite.
Volcanic glass is a common constituent in the Chukchi Sea,
into which it has possibly been carried by north-setting cur-
rents from the more volcanic areas of the Bering Sea. In
many of the samples taken from the Kodiak area, pumice is
the most prominent constituent. In the Juneau area meta-
morphic rock fragments and pebbles are common, including
slate, schist, and gneiss.

Authigenic minerals such as glauconite and phosphorite
are practically absent from these sediments. This finding
suggests that rapid deposition is taking place on the shelves
of the Bering and Chukchi Seas, since such authigenic min-
erals tend to form under conditions of very slow or no depo-
sition. Unweathered mineral grains of species which are
subaerially unstable, such as olivine, biotite, and the pyri-
boles, are abundant.

Diatoms. Diatom frustules are not abundant either as to
numbers or species in the bottom sediments. In all cases
they represent less than one per cent of the sample. The
identifications of the diatoms (see table V) were made by
Mr. Brian Boden of the Scripps Institution of Oceanography.
Diatoms are most abundant in the sediments of the south
Bering Sea and to a lesser extent in Kotzebue Sound. Cosci-
nodiscus centralis Ehrenberg is the dominant species, being
found in nearly all the samples; Coscinodiscus curvatulus



28



TABLE IV

MINERALS AND ORGANISMS IN ARCTIC BOTTOM SEDIMENTS



NEL


LIGHT MINERALS


HEAVY MINERALS


ROCKS




ORGANISMS




Sample






































No. Quartz Feldspar Mica


Pyriboles


Others




Siliceous


Calcareous


Chitinous


501


A


C


b; m


?


ol


qtzte; bas; si


Di(A)


F


Cr


503


C


C


m(R)


hyp


ol(C)


qtzte; bas


Di(A)


F




505


C


C


m; b


hyp; hbl; aug ol


bas


Di


F




507


C


C


m; b


(P)


ol(?)


si; bas


Di


F




509


C


C


m; b


(P)


ol


bas


Di


F


wm; Cr


510


C


C


m; b


hyp; hbl


ol


bas


Di


F




511


A


C


m; b


hbl


ol


bas; qtzte


Di(R)


F




512


A


C


m; b(R)


hbl; aug(?)


ol


si; qtzte




F; Ostr; Moll




514


A


C


m; b


hbl(?); aug


ol


bas; qtzte




F; Moll; Ostr


Cr


515


A


C


m; b


hbl


ol


bas; v. gl


Di


F




516


A


C




hbl(R)


ol


bas


Di


F; Moll; Ech




517


A


C


m(C); b


(P)


ol(R)


bas


Di


F; Ostr




519


C


C


m; b


(P)




bas


Di


F; Ostr




520


C


C


m(R)


(P)


ol


qtzte; v. gl; bas


Di


F


Alg


521


C


C


m(R); b(R)


(P)


ol


qtzte; v. gl; bas


Di


F




522


P


A


m(R)


(P)


ol


v. gl; si; bas


Di


F




523


P


A


m(R)


(P)


ol


v. gl; si; bas


Di


F




524


C


C


m; b


(P)




v. gl; bas; qtzte


Di


F




526


A


C


m; b


(P)


ol


bas




F




528


A


C


m; b


(P)




v. gl; bas(R)


Di


F; Moll frags


Alg


530


A


C


m; b


(P)




qtzte; v. gl; bas


Di(R)


F




532


A


c


m; b


(P)




qtzte; v. gl; bas


Di


F; Ostr; Moll


Alg


534


A


c


m; b


(P)




qtzte; v. gl; bas


Di


F; Moll frags




536


C


c


m; b(R)


(P)






Di


F




537


C


c


in rocks


in rocks




gr; gn; sch; si




Moll frags




538


P


p


m(C); b


(R)




pum


Di


F


Alg


539


C


c


m(C); b


(P)




v. gl; bas




F


Alg


540


C


c


m(C); b


(P)




v. gl; bas


Di


F; Moll frags


Alg


541


C


c


m; b


(P)




qtzte; bas


Di


F; Moll frags




545


C


c


m(C); b


(P)




v. gl; bas; qtzte


Di(R)


F


Alg


546


C


c


m(C); b


(P)




bas




F


Alg; f. sc


546A


C


c


m(C); b


(P)




bas




F


Alg; f. sc


548


C


c


m; b


(P)




qtzte; bas; sch


Di(R)


F; Moll frags;
Ostr


Alg


550


A


c


m; b(R)


(P)




bas; qtzte


Di; sp spic


F; Bra; Ech sp;
Moll frags


Alg


552


A


c


m; b


(P)




bas; sch; si




F; Ostr; Moll
frags; Ech sp


Alg


553


C


c


m & b(R)


(P)




qtzte; v. gl(R); bas




Ostr; Bra; Moll


Alg


555


A


c


m & b(R)


(P)




qtzte; bas


Di(R); sp spic F; Ostr; Moll


Alg


















frags




556


R










qtzte




F; Bry


Alg


557












qtzte




Moll; Bry


sp; Cr


558












gab




Alg; Bry




559


C


c


m; b


(P)


9


qtzte; gab; bas


Di(R)


F; Ostr; Moll
frags


Alg


560


C


c


m; b


(P)




qtzte; bas; si;
sch; gab




F


Alg


561


A


c


m; b(C)


(P)




gr; qtzte; bas




F; Ostr; Moll
frags


Alg


563


C


c


m(C); b


(P)




bas




F; Ostr; Moll


Alg; Cr


564


A


c


m(C); b


(P)




bas




F; Ostr; Moll
frags


Alg


567


R


A




(C)


mag; ol


bas




F; Ostr


Cr


569


P


A


m(R); b


(C)


mag; ol


v. gl


sp spic


F; Ech sp; Ostr
Moll frags


Cr



TABLE IV (continued)

MINERALS AND ORGANISMS IN ARCTIC BOTTOM SEDIMENTS



"NET"
Sample



LIGHT MINERALS



HEAVY MINERALS



ROCKS



ORGANISMS



No.


Quartz Feldspar


Mica


Pyriboles


Others




Siliceous


Calcareous


Chitinous


571


R


R


b(R)










F; Ech sp; Moll
frags




589


C


C


m(R); b


(R)


v. gl


qtzte; gr; bas; sch




F; Bra


Alg


590


P


P


m; b


(R)


ol(?)


qtzte; sch; bas; v. gl




F; Ostr; Moll


Alg


594


C


C


m(R); b(C)


(P)




qtzte; gn; sch; bas




F


Alg


596


R


VR


B(R)


(R)




sch; pum; bas


Di(R)


F


Alg


600












sch; v. gl; pum




F(R)




601












sch; v. gl; pum(A)




Moll


Cr(R); Alg(R)


605


P










qtzte; sch; bas; v. gl




F; Ostr


Alg(R)


607












sch




Moll frags




608












sch; v. gl; pum




F(R); Moll


Alg(R)


609


A


C


m; b(C)


hbl; etc(P)


tr; mag






F(R)


Alg


610


C


C


m; b(C)


(P)


tr; mag


pum


Di(C)


F; Moll


Alg; wm; wood


612


P


R


b


(R)


tr; mag


sch(C)


Di


F; Ostr


Alg


615












si; sch; gn




Moll; Alg; Bry





ABBREVIATIONS:

Alg Algae

aug augite

b biotite

bas basalt

Bra Brachiopoda

Bry Bryozoa

Cr Crustacea

Di Diatoms

Ech Echinoids

F Foraminifera

frag fragment

f.sc fish scales

gab gabbro

gn gneiss

gr granite

hbl hornblende



hyp hypersthene

m muscotite

mag magnetite

Moll Mollusca

ol olivine

Ostr Ostracoda

pum pumice

qtzte quartzite

sen schist

si slate

sp sponge

spic spicule

spin spine

tr tremolite

v.gl volcanic glass

wm worm trails or tubes



FREQUENCY SYMBOLS: A Abundant C Common P Present

R. . . .Rare If no frequency symbol is used, item is considered as present



Grunow is present in most of the Bering Sea samples; and
Melosira sulcata (Ehreriberg) was identified in all the Kotzebue
Sound samples.

There is little correlation between the abundance and type
of living diatoms obtained from the overlying water in net
hauls by Phifer 10 and the number and species present in the
bottom sediment. For example, Coscinodiscus centralis ,
although widely distributed, is found in net haule in only
relatively small numbers. Many diatoms which are abundant
in the water are completely absent from the sediments. These
are generally the filamentous forms whose frustules are



TABLE V

DIATOMS IN ARCTIC BOTTOM SEDIMENTS




readily comminuted and dissolved. Also these frustules are
probably transported off the shelf and into the oceanic basins
by even the weakest of currents.

Foraminifera. Foraminifera are not abundant in the
bottom sediments of the Bering and Chukchi Seas. However, a
few were separated from most of the samples by floating them
off with carbon tetrachloride. The fauna was quite uniform
from sample to sample so that there was little to be gained
from considering each sample separately. The great abundance
of arenaceous tests as compared with calcareous forms is
noteworthy. Some of the species are probably new species.



The following is a composite list of species identified from
3 bottom samples by M. L. Natland of the Richfield Oil
Corporation.

Cassidulina sp.

Elphidium cf. articulatum (d'Orbigny)

Elphidium cf. hughesi Cushman and Grant

Eponides frigida Cushman

Haplophragmoides sp.

Lagena gracilis Williamson

Lagena striata var. strumosa Reuss

Martinotiella sp.

Nonion labradoricum (Dawson)

N onion cf. scapha (Fichtel and Moll)

Nonionella turgid a var.?

Reophax excentricus Cushman

Textularia sp.

Verneuilina advena Cushman

Virgulina cf. bramletti Galloway and Morrey

Trocbammina sp.

Vvigerina juncca Cushman and Todd

Although the assemblage is boreal, many of the species
are commonly found off southern California at depths similar
to the depth at which they are found in the Bering and Chukchi
Seas. The arenaceous species Verneuilina advena is noted by
Natland as being very abundant. This is especially significant
because he has found this species abundant in the Gulf of
Panama. Apparently some factor other than temperature,
such as depth or character of the sea floor, controls the
distribution of this species.

Bacteria. Aseptic mud samples from various portions
of the core samples from the Bering and Chukchi Seas were
extracted by Fred Sisler of the Scripps Institution of Oceanog-
raphy in order to study the bacterial flora. The detailed re-
sults of this study are being reported separately by ZoBell
and Sisler. Among other things, this study showed the usual
presence of anaerobic hydrogen-consuming heterotrophes
(bacteria which utilize organic matter as a source of energy)
and the complete absence of anaerobic hydrogen-consuming
autotrophes (bacteria which utilize inorganic matter as a
source of energy).

Distribution of Shelf Sediments . At first view, the sediment
distribution in the Bering and Chukchi Seas, as shown in
figures 2 and 5, requires some explanation. There is no
support for the often-stated belief that sediments are coarse
near shore and become progressively finer with depth and
distance from shore; such a belief is based upon wind wave
action alone and grossly fails to consider the many other
processes at work. However, the grade-size distribution of



sediments is largely explainable when the following factors
are considered: (l) the depth; (2) the topography of the bot-
tom; (3) the distance from a source of sediments such as the
shore or a river mouth; (4) the exposure of the bottom to
currents related to internal waves, the tide, semipermanent
currents, or surface waves. Tidal currents are an especially
important cause of bottom erosion because both theory and
actual measurement show that they extend to the sea floor
with little loss of velocity except that caused by frictional
drag against the bottom. Currents in general reach maximum
velocities wherever the flow is constricted, either horizon-
tally or vertically, such as in narrow bay entrances, over
submarine hills, in straits, over sills, or at breaks -in-slope.

On the shelves of the Bering and Chukchi Seas, rocky,
stony, and coarse sandy areas appear to be largely confined
to topographic highs on the bottom, to the vicinity of the
break-in-slope between the shelf and the continental slope
of the Bering Sea, and to bottoms swept by strong semi-
permanent currents. A zone of coarse sand appears to lie
along the margin of the shelf of the Bering Sea near the break-
in-slope. According to Trask, 14 coarse sediment is also
found down to a depth of 1,080 fathoms (2,000 meters) on this
continental slope. The presence of coarse sediment near the
break-in-slope appears to be a characteristic of most conti-
nental shelves. Stetsonll recorded coarse sediment at the
edge of the shelf off the eastern United States. He ascribed
this finding to vigorous wave action during lower Pleistocene
sea levels which washed out the mud, and suggested that since
that time fine material from shore has been deposited before
reaching the break-in-slope. The authors of this report,
however, are inclined to ascribe the coarse sediment along
the margin of the shelf to the stronger currents, especially
tidal currents, which winnow out the mud. Fleming and
Revelle 5 have shown theoretically that such a concentration
of currents must take place. Currents moving onto the shelf
from the open ocean are greatly speeded up because the verti-
cal cross-sectional area of the ocean is reduced.

The stony and rocky bottom present in the Bering Strait
is undoubtedly related to the strong scouring action of the
north-setting current which funnels through this strait. The
USS NEREUS measured a surface velocity of 2 knots at the
time of her passage (see Dynamic Topography and Currents,
below). This strong current continues northward along the
Alaskan coast toward Point Barrow and probably accounts
for the coarse sediments found at stations 22 and 26 outside
of Kotzebue Sound (fig. 5).



$RESTIUGTE«ft



No topographic highs were encountered on the track of
the USS NEREUS, but it is likely that any which exist are
rocky or stony areas. This is especially true of topographic
highs which are also shoals, but such highs, regardless of
depth, are invariably covered with at least coarse sand. For
this reason, it is likely that the bottom in the vicinity of
Herald Shoal is coarse grained.

The bottom of the Bering Sea is largely covered by fine
sand, whereas the somewhat shoaler Chukchi Sea has typically
a mud bottom. This condition is probably related to stronger
bottom currents which oceanographic conditions show must
exist in the Bering Sea. In the Chukchi Sea, moreover, the
tides are smaller than in the Bering Sea; the small tide that
does exist (at Point Barrow the mean tide change is only
l/Z foot) is caused by the Atlantic tidal wave traversing the
Arctic Ocean. Throughout most of the year the Chukchi Sea
is ice-covered, promoting quiet bottom conditions. Surface
waves of more than a short period are almost entirely absent,
and these have little effect on the bottom because waves only
generate appreciable bottom currents to a depth equal to
one-half their wave length. There is also a large amount
of fine sediment carried into the Chukchi Sea by rivers, ice
rafting, and currents through the Bering Strait. All these
factors probably account for the muddy character of the
Chukchi Sea floor.

Ice Rafting. The most striking method of transportation


1 3 5 6 7 8

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