If ron do not need this publication after it has served your purpose, please return it to the 

Geological Survey, using the official mailing label at the end

UNITED STATES DEPARTMENT OF THE INTERIOR

GEOLOGY AND BIOLOGY OF 

NORTH ATLANTIC DEEP-SEA CORES

PART 8. ORGANIC MATTER CONTENT

GEOLOGICAL SURVEY PROFESSIONAL PAPER 196-E

UNITED STATES DEPARTMENT OF THE INTERIOR 

Harold L. Ickes, Secretary

GEOLOGICAL SURVEY 

W. C. Mendenhall, Director

Professional Paper 196-E

GEOLOGY AND BIOLOGY OF

NORTH ATLANTIC DEEP-SEA CORES

BETWEEN NEWFOUNDLAND AND IRELAND

PART 8. ORGANIC MATTER CONTENT

BY

P. D. TRASK, H. W. PATNODE, J. L. STIMSON 

AND J. R. GAY

UNITED STATES

GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1942

For sale by the Superintendent of Documents, Washington, D. C. ------ - Price 20 cents

CONTENTS

	Page 

Outline of the complete report_________________________________________________________________________________ v

Summary of the complete report____________________ __________________________________________________________ vn

Foreword, by C. S. Piggot.___---__-_-_-----___-__--__--_-_-___-_____-___-_-_____-_______--__-_____-__-______-_- xi

General introduction, by W. H. Bradley---___--_------_-------_-_____---__-_____-_---__-__--_______-___-_____--_- xm

Significance of the investigation.____________________________________________________________________________ xm

Location of the core stations.________________________________________________________________________________ xiv

Personnel and composition of the report._____________________________________________________________________ xiv

Methods of sampling and examination______________________________________________________________________ xiv

Part 8. Organic matter content, by P. D. Trask, H. W. Patnode, J. L. Stimson, and J. R. Gay________________________ 135

Introduction. ______________________________________________________________________________________________ 135

Methods of study________________________________________________-_.___________--___-____-_______._-.-_ 135

Nitrogen content.__---__--_---_-_----___--_____.____________________-________-_-_-_-_____-_-______-__- 135

Reduction number.--___-----__--___-_____-_-_-_-___________________________-__-__-____-____________--_ 136

Nitrogen-reduction ratio.._______________________________________________________________________________ 137

Description and location of samples._________________________________________________________________________ 138

Results...._____________________________________________________________________________________________ 139

Basic data_____________________________________________________________________________________________ 139

Relationships __ ______________________________________________________________________________________ 142

Surface layers.-----______---_______--__-__________________________________-_..__-_-_-_-_-_-_--_---- 142

Subsurface layers._________________________________________________________________________________ 142

Temperature-__________ ___________________________________________________________________________ 144

Texture.____.___._____..___._-_.___________....______.______._____.__-.-_-_-_-.._.___.___... 145

Comparative organic content______________________________________________________________________ 145

Rate of deposition of organic matter.__-___-_________________________________---__-_-_-____--____---- 147

Nitrogen-reduction ratio.___________________________________________________________________________ 147

Foraminifera_ _---__..__--__________--_---___________:___________________________--__-______-__------ 148

Calcium carbonate-________________________________________________________________________________ 149

Index._______________________________________________________________________________________________________ xvu

ILLUSTRATIONS

Page 

PLATE 1. Bathymetric chart of a part of the North Atlantic Ocean showing the location of the core stations._____________ xv

2. Longitudinal sections of the air-dried cores._______________________________________-____--_-_--_--_--_---_ xv

FIGURE 1. Profile across the North Atlantic Ocean bottom along the line of the numbered core stations____--_______--_- xiv

23. Relation of nitrogen content to reduction number in the samples studied.__________________________________ 137

24. Location of samples in cores.._________________________________________________________________________ 139

25. Chart showing areal and vertical distribution of nitrogen in sediments in cores 3 to 13.______________________ 141

26. Chart showing areal and vertical distribution of reduction number in sediments in cores 3 to 13_______________ 141

27. Vertical profiles across the North Atlantic Ocean about latitude 49° N., between Grand Banks, Newfoundland, 

and Lands End, England, showing relation of submarine topography to nitrogen content, reduction number, 

and nitrogen-reduction ratio of sediments.________________---__-___-.--___ __________________________ 143

28. Relation of reduction number of sediments to temperature of surface water as indicated by the pelagic Foraminifer*

in the sediments._--_-_______-_____-_-_-_______________________-_________-__-__---_-_---._-_____--- 144

29. Relation of reduction number to texture of sediments__-_-_-_-_--------_-----_----------.._________-___-__ 145

30. Relation of reduction number to percentage of Foraminifera in sediments__________________________________ 148

TABLES

Page 

TABLE 1. Geographic location, length of cores, and depth of the water from which they were taken.______-__.___-___-__ xiv

30. Average values of the nitrogen content, reduction number, and nitrogen-reduction ratio._____________________ 139

31. Average reduction number of warm and cold zones__--____._______.__-___________-_--_---__. _____.____--_ 144

32. Comparative organic content of the se'diments______. __________-______________-____-___--_-_---------_--- 146

33. Relative rate of deposition of organic matter per zone._________________._-_-________----.-----___-____----- 147

in

OUTLINE OF THE COMPLETE REPORT

Foreword, by C. S. Piggot.

General introduction, by W. H. Bradley.

PART 1. Lithology and geologic interpretations, by M. N. Bramlette and W. H. Bradley.

2. Foraminifera, by Joseph A. Cushman and Lloyd G. Henbest.

3. Diatomaceae, by Kenneth E. Lohman.

4. Ostracoda, by Willis L. Tressler.

5. Mollusca, by Harald A. Rehder.

6. Echinodermata, by Austin H. Clark.

7. Miscellaneous fossils and significance of faunal distribution, by Lloyd G. Henbest.

,8. Organic matter content, by Parker D. Trask, H. Whitman Patnode, Jesse LeRoy Stimson, and John R. Gay. 

9. Selenium content and chemical analyses, by Glen Edgington and H. G. Byers.

SUMMARY OF THE REPORT

In May and June 1936 Dr. C. S. Piggot of the Geophysical 

Laboratory, Carnegie Institution of Washington, took a series of 

11 deep-sea cores in the North Atlantic Ocean between the 

Newfoundland banks and the banks off the Irish coast. These 

cores were taken from the Western Union Telegraph Co.'s cable 

ship Lord Kelvin with the explosive type of sounding device 

which Dr. Piggot designed. In the fall of that year he invited a 

group of geologists of the United States Geological Survey to 

study the cores and prepare a report. Biologists of the United 

States National Museum, the University of Buffalo, and chemists of the United States Department of Agriculture cooperated 

in the investigation and contributed to the report.

The westernmost core of the series (No. 3) was taken in the 

blue mud zone, but all the others were taken in parts of the ocean 

where the bottom is blanketed with globigerina ooze. The 

shortest cores are No. 8, taken on the mid-Atlantic ridge in 1,280 

meters of water, and No. 11, taken where the core bit struck 

volcanic rock. The cores range in length from 0.34 to 2.93 

meters and average 2.35 meters. They were taken at depths 

ranging from 1,280 to 4,820 meters.

Lithology and geologic interpretations.—In about 20 representative samples from each core the percentages of calcium carbonate, 

clay and silt, and sand were determined and plotted, and the 

relative abundance of Foraminifera, coccoliths, and diatoms was 

estimated. Material between these guide samples was examined 

microscopically, especially in certain critical zones.

Two zones were noted in which silicic volcanic ash (refractive 

index near 1.51) is common. The upper ash zone was found in 

all the cores except No. 11, but the lower one was found only in 

the lower part of cores 4 to 7. In core 3 the upper ash zone is 

represented by shards scattered very sparsely all through the 

core, as this core, despite its length of 2.82 meters, apparently did 

not reach the bottom of the ash zone. The upper ash zone, 

together with other adjacent lithologic zones, serves to correlate 

the cores, and the lower ash zone, found west of the mid-Atlantic 

ridge, helps to confirm the correlation.

Besides the zones of volcanic ash four other zones distinctive in 

lithologic character were found. These zones are characterized 

by a relative abundance of sand and pebbles, by a smaller 

percentage of calcium carbonate, and by a sparsity of Foraminifera and coccoliths. They are distinctive also in texture. The 

pebbles are subrounded to angular and include a wide variety of 

rock types—sandstone, gneiss, soft shale, and limestone—of 

which limestone is the most common. Some of the pebbles are 

as much as 2 centimeters across. These zones are interpreted as 

glacial marine deposits formed during the Pleistocene glacial 

epoch, when continental glaciers were eroding the land. Drift 

ice from the continental glaciers apparently transported consideraable quantities of rock debris far out into the ocean basin.

Between the glacial marine zones found in the North Atlantic 

cores the sediments consist chiefly of foraminiferal ooze or marl, 

much like that which is forming today in the same area.

The uppermost glacial marine zone is represented in ail the 

cores except Nos. 3 and 11 and lies just below the upper volcanic 

ash zone. In cores 4 to 7 the glacial zones are relatively thin and 

are spaced at approximately equal intervals; between the third 

and fourth glacial zones (in descending order) is the lower volcanic 

ash. East of the mid-Atlantic ridge only the uppermost glacial

zone has been identified. Other glacial marine deposits are 

recognizable but their correlation is less certain.

Three interpretations are offered as possible explanations of 

the four glacial marine zones. The first is that each glacial 

marine zone represents a distinct glacial stage of the Pleistocene 

and that each zone of foraminiferal marl separating two glacial 

marine zones represents an interglacial stage. This interpretation seems least probable of the three. The second interpretation 

is that the upper two glacial marine zones and the intervening 

sediment may correspond to the bipartite Wisconsin stage, 

whereas the lower two represent distinct glacial stages of the 

Pleistocene separated from each other and from the zone representing the Wisconsin stage by sediments that represent interglacial epochs no greater in length than postglacial time. This 

interpretation seems to imply too short a time for most of the 

Pleistocene epoch. The third interpretation, which is favored 

by the authors, is that each of the four glacial marine zones 

represents only a substage of the Wisconsin stage. This implies 

that the North Atlantic at approximately 50° north latitude for 

comparatively long periods of time alternately contained an 

abundance of drift ice and then was quite, or nearly, free of ice, 

while on land a continental ice sheet persisted, though it alternately waned and grew.

In the four cores in which the postglacial sediments are 

thickest the pelagic Foraminifera, according to Cushman and 

Henbest, reveal an interesting condition. These organisms 

indicate that during the middle part of the postglacial interval 

the temperature of the surface water in that part of the North 

Atlantic was somewhat higher than prevails today.

On the assumptions that the top of the uppermost glacial 

marine zone represents the beginning of the postglacial epoch as 

defined by Antevs, and that this was probably as much as 9,000 

years ago, the postglacial sediment in these cores accumulated 

at a rate of about 1 centimeter in 265 years; but, because the sea 

probably cleared of detritus-laden drift ice long before the land 

in the same latitude was cleared of the retreating continental 

ice sheet, the average rate of accumulation may have been as 

low as 1 centimeter in 500 years.

Coarse-grained sediment on the tops of ridges and fine-grained 

sediment in the deeper basins indicate that currents move across 

these ridges with sufficient velocity to winnow out the finer 

particles and sweep them into deeper basins beyond.

The fact that the glass shards in the volcanic ash zones have 

been reworked and distributed without any gradation in size 

through many centimeters of the overlying sediments leads us 

to believe that mud-feeding animals are continually working over 

these shards and other particles of sand and silt so that they are 

redistributed at successively higher levels. The shards and other 

particles may also be reworked by gentle bottom currents that 

move the material from mounds and ridges on the sea floor and 

drift it about over the adjacent flatter areas.

Several layers in the cores are sharply set off by the coarser 

grain size of the sediment or by a regular gradation in grain size 

from coarsest at the base to fine at the top. These may be a 

result of submarine slumping.

The term globigerina ooze is used loosely in this report to 

designate sediment, half or more than half of which, by weight, 

consists of Foraminifera. This usage accords more closely with
VIII SUMMARY OF THE REPORT

the usage adopted by Correns in the Meteor reports than with 

the usage of Murray and Chumley in the Challenger reports, 

which was based solely on the carbonate content. Limy muds 

containing a lesser but still conspicuous number of Foraminifera 

are referred to as foraminiferal marl. The carbonate content 

of the globigerina ooze in these cores ranges from 46.6 to 90.3 

percent and averages 68.2 percent. In 191 samples representing 

all the lithologic types, the carbonate content ranges from 10.0 

to 90.3 percent and averages 41.3 percent. Coccoliths are 

abundant in many parts of the cores, but by reason of their small 

size they rarely make up as much as 10 percent of the sediment. 

Pteropods are rather numerous in parts of the cores taken on the 

mid-Atlantic ridge and on the continental slope off the Irish 

coast.

Most of the calcium carbonate in these sediments consists of 

the tests and comminuted fragments of calcareous organisms. 

The finest particles of carbonate are of indeterminate origin, but 

their irregular shape and range in size suggest that they are 

largely the finest debris of the comminuted organisms rather 

than a chemical precipitate. Clusters or rosettes of calcium 

carbonate crystals were found in many samples, but they are not 

abundant. They evidently formed in the mud on the sea floor.

No conclusive evidence of an increase in magnesium carbonate 

with depth was found, though some of the data suggest it. The 

magnesium carbonate is somewhat more abundant in the glacial 

marine zones than elsewhere, but its concentration in those zones 

is probably accounted for by the presence of clastic grains and 

pebbles of dolomite.

Diatom frustules, radiolarian skeletons, and sponge spicules 

are the most common siliceous organic remains found in the 

cores, and these generally form less than 1 percent of the sediment. One notable exception is the sediment in the middle part 

of core 9, just east of the mid-Atlantic ridge, which contains 50 

percent or more of diatoms.

Ellipsoidal and elongate or cylindrical pellets that appear to 

be fecal pellets are plentiful in the mud at the tops of cores 10 

and 12, taken in the eastern part of the North Atlantic, but 

were not found elsewhere. No attempt was made to identify 

them further.

The sand-size material showed no marked variation in the 

mineral composition of the clastic grains at different horizons 

within individual cores and no conspicuous lateral variation 

from core to core. The mineral grains in the sand-size portions 

were not separated into light and heavy fractions, but simple 

inspection showed that grains of the heavy minerals are somewhat more common in the glacial marine deposits than elsewhere. Well-rounded sand grains are sparsely scattered through 

all the cores, but they are rather more plentiful in the glacial 

marine zones. These grains, which range in diameter from about 

0.1 to 1.0 millimeter and average 0.5 millimeter, have more or 

less frosted surfaces. They may have been derived from the 

reworking of glacial marine deposits or they may have been 

rafted by seaweeds. Little was done with the clay minerals 

other than to note tha*t most of them have the optical properties 

of the beidellite or hydrous mica group?.

Six samples were tested with a 10-inch spectograph, which 

revealed the presence of appreciable amounts of barium and 

somewhat less of boron in each sample. All the samples gave 

negative tests for antimony, beryllium, bismuth, cadmium, germanium, lead, silver, tin, and zinc.

The original porosity of several samples in core 3 was calculated from the porosity of the dried samples. The original 

porosity plotted against depth in the core seems to indicate that 

fine-grained blue muds buried to a depth of 2 or 3 meters in the 

ocean floor are appreciably compacted.

Partial mechanical analyses of nearly 200 samples were made 

and plotted, but only four complete mechanical analyses were

made. The complete analyses were made by the sedimentation 

method and include four distinctive types of sediment.

Pumiceous fragments and smaller shards of basaltic volcanic 

glass (index of refraction near 1.60) are scattered throughout all 

the cores, but are somewhat more common east of the mid-Atlantic ridge than west of it. Unlike the alkalic volcanic ash it 

shows no conspicuous concentration in zones. Most of the basaltic glass and pumice has a thin surface alteration film of palagonite. The films are thickest on fragments in cores taken from 

ridges where oxygen-bearing waters had free access to the sediments. Two varieties of palagonite are recognized.

Core 1L represents only 34 centimeters of the sea floor because 

the core bit encountered deeply altered olivine basalt. About 

15 centimeters of globigerina ooze rests on and within irregular 

cavities of the upper surface of a mass of clay that is apparently 

altered basalt. This clay is impregnated with manganese and 

contains nodular lumps of altered basalt. Part of the basalt 

near the base of the core is less altered. The clay contains scattered grains of sand and foraminiferal shells in which the original 

calcium carbonate has been replaced by a zeolite resembling phillipsite. This core may have penetrated the upper, deeply altered 

part of a submarine lava flow, but the evidence is not conclusive.

Core 10 contains two rather thick beds of distinctive clayey 

mud. About half of this mud is a beidellite or hydrous mica 

type of clay and the other half is made up of silt-size particles of 

basaltic glass, magnetite, augite, and calcic plagioclase. It 

contains very little common clastic material and exceedingly 

few Foraminifera. The composition and texture suggest that 

this mud was derived largely from a submarine volcanic eruption 

that threw into suspension clay particles perhaps partly from the 

normal sediment and from deeply altered basalt. A complete 

chemical analysis of this mud is given.

Foraminifera.—From these cores 184 samples representing 

every lithologic zone were examined for calcareous fossils. All 

but five samples contained Foraminifera. As in existing oceans 

deeper than several hundred meters, pelagic Foraminifera greatly 

outnumber the bottom-dwelling forms, though in variety of form 

and in number of genera and species the bottom forms greatly 

exceed the pelagic. Several zones of relatively pure globigerina 

ooze were found, and many in which the ooze was clayey or sandy. 

Though variations in temperature were reflected by faunal 

changes, the general bathymetric facies of the faunas appear to be 

rather uniform throughout each core. The bottom faunas are 

least varied and prolific in cores from the deepest water, whereas 

in cores from the shallowest water they are by far the most 

varied and prolific. Cores from intermediate depths contain 

faunas of intermediate bathymetric facies. These relations to 

depth are, in general, characteristic also of faunas in the existing 

oceans. A few scattered specimens of Elphidium or Elphidiella 

were found. These genera thrive in shallow water, but in these 

cores the shells are so rare, so erratically distributed, and in some 

so poorly preserved that it seems probable they were rafted in by 

seaweeds or ice and therefore have no significance as indicators of 

depth. No species peculiar to the Miocene or Pliocene were 

found. It appears, therefore, that all the sediments penetrated 

by the cores are younger than Pliocene. Alternation of faunas 

that are characteristic of the warm and cold climates of the 

present day indicates great climatic changes during the time 

represented by these cores. The foraminiferal facies characteristic of cold and warm climates correlate with the alternating 

sequence of glacial-marine and warmer-water sediments indicated 

by the lithology. This correlation suggests that all the sediments in these cores are of Recent and Late Pleistocene age.

Diatomaceae.—Fifty-two species and varieties of diatoms were 

found in these cores. A large percentage of the species are neritic, 

warm-water forms that are foreign to the region today. Several
SUMMARY OF THE REPORT IX

alternations of warm-water and cold-water diatom floras occur 

in most of the cores, but their position in the cores is not in 

accord with the alternations of temperature inferred from lithology and foraminiferal facies. It is suggested that this disagreement may be due to the much longer settling time of the diatoms 

and that allowance should be made for it. The time equivalent 

of this difference of phase, as calculated from the vertical displacement necessary for the best approximation to agreement 

between the foraminiferal and lithologic data on the one hand 

and the diatom data on the other is of the order of 23,000 years. 

This figure appears absurdly high and a figure of several hundred 

years, based on extrapolation of experimentally timed settling 

in a relatively small vessel, is considered more reasonable. The 

action of cold and warm currents, some surficial and some deep 

seated, is suggested as the possible cause of the apparently erratic 

distribution of the diatoms. The possibility that the phase difference of 23,000 years mentioned above is related to shifts of 

ocean currents caused by advances and recessions of drift ice is 

offered as a speculation. Of 52 species and varieties illustrated, 

2 species and 1 variety are described as new.

Ostracoda.—In preparing a series of samples from the cores for 

the study of the Foraminifera about 175 specimens of Ostracoda 

were found. These belong to 13 genera and 27 species, all living 

forms, though 12 of the species are known also as fossils. Most 

of the ostracodes were found in three cores that were taken in 

tbe shallowest water (1,280 to 3,230 meters). One of these cores 

(No. 8) was from the top of the mid-Atlantic ridge and tbe other 

two (Nos. 12 and 13) were from the continental slope southwest 

of Ireland. In the cores from deeper water (3,250 to 4,820 

meters) ostracodes were scattered very sparsely. Like most 

marine ostracodes, all the species found in the cores are bottom 

dwellers. Most of the species are decidedly cold-water forms 

that are found in tropical waters only at great depth, where the 

temperature is near freezing. Northern forms predominate; only 

2 of the species have not previously been known from northern 

waters, and 10 species are definitely Arctic forms. A few species 

that have a wider temperature range live not only in cold waters 

but also in the deep warm water of the Mediterranean.

The predominance of distinctly cold-water ostracodes and the 

prevalence of Arctic forms suggest that the temperature of the 

water in this part of the North Atlantic was formerly somewhat 

lower. But, as might be expected from the fact that all the 

species in these cores are bottom dwellers, their distribution in 

the cores shows no evident relationship to the cold and warm 

zones indicated by the composition and texture of the sediments 

and by the pelagic Foraminifera.

Mollusca.—The mollusks recovered from these cores can be 

divided into two groups, the pteropods and the other gastropods 

and pelecypods. The pteropods are by far the more numerous. 

All the specimens of the pelecypods and gastropods, other than 

pteropods, are representatives of deep-water species that are now 

living in the same boreal or cold-temperate waters. Also, the 

fragments that could not be identified specifically belong to forms 

that have congeners now living in these waters. The fauna of 

these cores, even that taken from the lower parts of the cores, 

shows no appreciable difference from that now living in the same 

localities. Among these mollusks no evidence of shallower or 

considerably deeper water is demonstrable. Molluscan remains, 

other than those of pteropods, are too scarce to attempt to 

differentiate cold- and warm-water facies, as was done with the 

foraminiferal faunas.

The Pteropoda, which are far more abundant in the cores than 

the other mollusks, belong to two genera and three species. One 

of the species is new. The geographic distribution of the pteropods is limited more by the temperature of the surface water 

than by any other factor. Nevertheless, as one species is cosmopolitan, one boreal, and one a new species thought to be the

401264—42———2

northern analogue of a more southern species, and as all three 

species occur together, they have no significance for differentiating cold- and warm-water facies. These organisms are pelagic 

and their shells have a rather wide distribution, but, as they are 

found on the sea floor at depths ranging from 247 to 3,750 meters, 

they are of little aid as indicators of depth of the ocean at the 

time these deposits were laid down.

Echinodermata.—The remains of 9 species of Echinodermata 

were found in the cores. These include 1 ophiuroid, 7 echinoids, 

and 1 crinoid. No remains of asteroids were found. All the 

echinoderms found belong to species now living in that part, or 

adjacent parts, of the North Atlantic. Echinoderm remains are 

rather uniformly distributed among the cores, but they are most 

numerous in core 8, which was taken in 1,280 meters of water 

on the crest of the mid-Atlantic ridge. By far the commonest 

species is Pourtalesia miranda, remains of which were found in 

nearly two-thirds of the 82 echinoderm-bearing samples and in 

all the cores except 8 and 11.

Because the association of species in the cores is closely 

similar to the association of living species in that part of the 

North Atlantic and because the association of species within each 

core is independent of the distance below the top of the core it 

appears that neither the distribution nor the composition of the 

echinoderm fauna has changed significantly during the interval 

represented by these cores. No evident relationship was found 

between the distribution of the various species of echinoderms 

and the cold- and warm-water facies of the sediments indicated 

by both the Foraminifera and the lithology.

Miscellaneous fossils and significance of faunal distribution.— 

The principal fossil groups represented in the cores, listed in 

order of abundance, are foraminifers, diatoms, echinoids, siliceous 

sponges, radiolarians, ophiuroids (spines and plates), ostracodes, 

and pteropods. Remains of barnacles, brachiopods, pelecypods, 

holothuroids, bryozoans, gastropods, and teleost fishes (otoliths) 

were also found, but all these are rare. The foraminifers, diatoms, ostracodes, echinoderms, pelecypods, and gastropods were 

studied separately by specialists. The other groups are briefly 

noted and illustrated for the sake of the record. The most 

varied and prolific faunas were found in the three cores that 

were taken from the shallowest water and the least varied and 

least prolific were found in those from the deepest water. The 

bottom-living faunas throughout each core have a broadly similar bathymetric facies, and the bathymetric facies of each core 

appears to correspond to that of the fauna now inhabiting that 

locality. Faunas having the characteristics of very shallowwater marine faunas are either absent or, if present, are so rare 

and erratically distributed that they appear to be foreign in 

origin rather than indigenous. Ostracodes and pteropods are 

locally abundant in the cores from the shallower water, but are 

absent or rare at all horizons in those from the deeper water. 

The distribution and bathymetric facies of the faunas weigh 

heavily against the hypothesis of extreme changes in ocean 

level during the later part of the Pleistocene.

Organic matter content.—The content of organic matter, as 

determined from 123 samples, ranges from 0.1 to 1.0 percent of 

the total weight of the sec iments, and the average is about 0.5 

percent. As in near-shore sediments, it is influenced by the 

configuration of the sea bottom. It is small on ridges and large 

in the deeps. It is particularly large in the sediments at the 

base of the east slopes of ridges, owing in part, probably, to 

material washed from the vicinity of the ridges by eastwardsweeping ocean currents. The organic matter content of the 

upper layers of the sediments in the abyssal deeps is greater 

for a few hundred miles east of the mid-Atlantic ridge than it 

is for a similar distance west of the ridge. The organic content 

does not vary consistently with depth except in core three, 

taken at the foot of the continental slope east of the Grand
X SUMMARY OF THE REPORT

Banks, where it seems to decrease about 25 percent in the first 

1.5 meters. The organic matter content of the sediments tends 

to be greater in the warm zones, than in the cold zones, and in 

general it is slightly greater in sediments which, according to 

Cushman's determination of the Foraminifera, were probably 

deposited in areas in which the surface water was relatively 

warm. The organic content is rather closely related to the 

texture, and increases with increasing fineness of the sediments. 

The rate of deposition of organic matter is greater east of the 

mid-Atlantic ridge than west of it, presumably owing in part 

to a greater supply of plankton and in part to a slower rate of 

decomposition of the organic matter after it is laid down in the 

sediments. The slower rate of decomposition within the sediments is inferred from the greater state of reduction of the 

sediments, which is indicated by the nitrogen-reduction ratio. 

The nitrogen-reduction ratio suggests a slight increase in state 

of reduction with increasing depth of burial in the upper part 

of the deposits, but indicates no significant change in the lower 

part. The percentage of organic content tends to increase as 

the percentage of Foraminifera in the sediments decreases, but 

it shows no relationship to the calcium-carbonate content.

Selenium content and chemical analyses.—As a part of a comprehensive investigation of the distribution of selenium in marine

sediments and soils derived from them complete fusion analyses 

were made of 20 samples from the suite of 11 cores. These 

samples were taken from the tops of the cores and at intervals of 

approximately 1 and 2 meters below the top. In addition, 1 

core taken on the continental shelf off Ocean City, Md., and 3 

cores from the Bartlett Deep were sampled and analyzed, making 

a total of 31 analyses. The results of the analyses include all 

the normal analytical data obtained in a so-called complete soil 

analysis by the fusion method, and, in addition, determinations 

of organic matter, nitrogen, chlorine (in all but 12 analyses), 

hygroscopic water, and selenium. All the samples were analyzed 

with the entrained sea salts. The core from the continental 

shelf off Ocean City contained the most selenium—at the top 

0.6 part per million, at 1 meter 1.0, and at 2 meters 2.0 parts per 

million. The samples from the North Atlantic cores showed a 

selenium content ranging from 0.06 to 0.8 part per million. Of 

the samples from the Bartlett Deep one contained 0.2 part per 

million of selenium, but all the others contained less than 0.08 

part per million. No evidence was found of a relation between 

the selenium content and volcanic activity.

The silica-sesquioxide and silica-alumina ratios are tabulated 

and their significance as means of comparing the analyses is 

discussed.
FOREWORD

By C. S. PIGGOT '

During the last cruise (1927-29) of the nonmagnetic 

ship Carnegie of the Department of Terrestrial Magnetism of the Carnegie Institution of Washington a 

number of samples of the deep ocean bottom were 

obtained by means of the telegraph snapper. The 

Geophysical Laboratory determined the radium content 

of these samples and found that they contained a concentration of radium 2 as astonishingly high as that 

reported by Joly 3 and Pettersson 4 from similar samples 

taken by the Challenger and Princess Alice II. This 

high radium concentration in the surface layer of the 

ocean bottom, which constitutes 72 percent of the surface of the globe, raises questions of great significance 

to both oceanography and geophysics. An obvious 

question is whether radium in so high a concentration is 

present down through all deep-sea sediments or only 

at the surface.8 If the first hypothesis is correct it 

indicates the presence of uranium throughout the sediments, whereas the second indicates the existence of 

radium itself, presumably separated out from the sea 

water. The study of this question requires samples of a 

type analogous to the cores so extensively used in subsurface exploration on land. Inquiries among oceanographic organizations established the fact that although 

some cores a meter or more in length had been obtained 

from relatively shallow water, many of them were much 

distorted by the time they reached the laboratory, and 

none as long as 1 meter had been obtained from a depth 

of 4,000 meters or more.6 Those engaged in such research 

emphasized the need of apparatus capable of obtaining 

undistorted cores from great depths. In 1933 the 

Council of the Geological Society of America approved a 

grant for the development of such apparatus.7 Fortunately, cooperation was obtained from several special

' Geophysical Laboratory, Carnegie Institution of Washington.

1 Piggot, C. S., Radium content of ocean-bottom sediments: Am. Jour. Sci., 5th 

ser., vol. 25, pp. 229-238, 1933.

' Joly, J., On the radium content of deep-sea sediments: Philos. Mag., vol. 16, pp. 

190-197, 1908.

1 Pettersson, Hans, Teneur en radium des depots de mer profonde: Resultats de 

Oampagnes Scicntiflques par Albert I « Prince Souverain de Monaco, vol. 81, 1930.

• Piggot, C. S.. op. cit., p. 233.

«Since these inquiries were made D. Wolansky has published her review in the 

Geologische Rundschau (Band 24, Heft 6, p. 399,1933), in which she refers to the work 

of A. D Archanguelsky in the Black Sea (Soc. Naturalistes Moscow Bull., new ser., 

vol. 35. op. 264-281, 1927). Wolansky mentions cores 3 to 4 meters long from depths 

of 2,237 meters. See also Wiss. Ergeb. Deutschen Atlantischen Exped. Meteor, 

1925-27, Band 3, Teil 2, Lief. 1, pp. 4-28,1935.

7 Piggot, C. 8., Apparatus to secure core samples from the ocean bottom: Geol. 

Soc. America Bull., vol. 47, pp. 675-684,1936.

agencies, particularly the Burnside Laboratory of the 

E. I. du Pont de Nemours, whose ballistics expert, Dr. 

B. H. Mackey, offered fundamental suggestions and 

made many essential calculations and tests; also the 

United States Bureau of Lighthouses, from whose lightship tender, the S. S. Orchid, many experimental soundings were made. Several forms of the apparatus were 

developed and tested, and in August 1936 14 satisfactory 

cores were obtained from the canyons in the continental 

shelf off New Jersey, Delaware, and Maryland, and 

another from the ocean floor below 2,500 meters of 

water.8 This first deep-sea test was made possible by 

the cooperation of the Woods Hole Oceanographic 

Institution and was carried out in connection with an 

investigation of the submarine canyons by H. C. Stetson 

of that institution. This test demonstrated the feasibility of the apparatus as built but suggested some 

minor changes in design. These were incorporated in 

another apparatus, which was put aboard the cable ship 

Lord Kelvin at Halifax, Nova Scotia. Through the 

courtesy of Mr. Newman Carlton, Chairman of the 

Board of Directors of the Western Union Telegraph Co., 

the Carnegie Institution of Washington was invited to 

have a member of its staff accompany the Lord Kelvin 

while that ship was engaged in making repairs to the 

North Atlantic cables, in order to test the apparatus in 

deep water. This offer was gladly accepted, and in 

May and June of 1936 I was on board the Lord Kelvin 

with the apparatus.

Because of the personal interest and cooperation of 

the commanding officer, Lt. Com dr. Bredin Delap, 

Royal Navy, retired, the undertaking was more successful than had been anticipated, and a suite of 11 

excellent cores was obtained, extending from the Grand 

Banks of Newfoundland to the continental shelf southwest of Ireland.

All but two of these cores (Nos. 8 and 11) are more 

than 2.43 meters (8 feet) long, and all contain ample 

material for study. Of the two short cores, No. 8 WHS 

taken from the top of the Faraday Hills, as that part 

of the mid-Atlantic ridge is known, where the material 

is closely packed and more sandy and consequently 

more resistant; No. 11 came from a locality where the

' Cushman, J. A., Henbest, L. G., and Lohman, K. E., Notes on a core sample from 

the Atlantic Ocean bottom southeast of New York City: Geol. Soc. America Bull., 

vol. 48, pp. 1297-1306, 1937.

XI
XII FOREWORD

apparatus apparently landed on volcanic rock that may 

be part of a submarine lava flow. Soundings at the 

localities where the cores were taken show depths ranging from 1,280 meters at the top of the Faraday Hills to 

4,820 meters in the deep water between the mid-Atlantic 

ridge and the continental shelf.

The thorough test made possible by the interested 

cooperation of everyone on board the Lord Kelvin fully 

demonstrated the capacity of the apparatus and produced material from strata of oceanic sediments deeper 

than have ever before been available.

In order that this pioneer material might be examined to the best advantage and an adequate estimate 

made of the potentialities of cores of this type,^,groupof 

investigators representing various fields of science was 

invited to examine them. Efforts have been made to 

arrange the sequence of these investigations in such a 

way that the maximum information may be obtained 

with the minimum destruction of the samples.

The cores are now at the Geophysical Laboratory of 

the Carnegie Institution of Washington, where they and 

others that.may be obtained by this laboratory will be 

held available for further research.
GENERAL INTRODUCTION

By W. H. BRADLEY

SIGNIFICANCE OF THE INVESTIGATION

The long cores of deep-sea sediment considered in 

this report represent a longer span of the earth's late 

geologic history, as recorded in abyssal sediments, than 

has been heretofore accessible. In a measure, therefore, this study has been exploratory. Because of that exploratory aspect we have not only presented the observations but also have deliberately speculated upon various 

possible interpretations of the features observed in the 

cores and upon their relations with one another. Because the cores are few in number and widely spaced, 

we offer many of the interpretations not as definite 

conclusions but rather as suggestions to be tested by 

whatever coring may be done in the future in that part 

of the North Atlantic.

From this investigation it appears that glacial marine 

deposits may prove to be sensitive indicators of the climatic changes that caused the growth and decay of 

continental ice sheets during the Pleistocene. In particular, it seems that the glacial marine record may 

throw light on the climatic fluctuations that determined substages of the Pleistocene. The marine 

record was the result of a continuously operating series 

of causes such that the deposits of each glacial substage 

were separated from one another by the deposits of the 

intervening warmer substage. The record of each 

substage has remained intact and was not obliterated 

by readvances of the ice. As the equatorward extent 

of the glacial marine deposits implies a corresponding 

expansion of continental ice sheets, the extent of the 

deposits may be used as a measure of the intensity of 

the climatic changes, and their thickness may be used 

as a rough indicator of the duration of glacial substages. 

Similarly, the thickness and poleward extent of tongues 

of nonglacial sediment—the foraminiferal marl—are 

measures of deglaciation. The areal extent of these 

tongues of sediment can be determined by additional 

cores taken at properly located stations.

When the glacial marine record is more fully known 

it should provide a basis for correlating the Pleistocene 

history of Europe and North America.

Cores taken along the meridians in series extending 

from the Arctic regions into the tropical parts of the 

Atlantic should make it possible to map the southern 

limits of pack ice in the sea during successive glacial 

maxima, at least for the later part of the Pleistocene.

As the pelagic Foraminifera in these abyssal sediments 

are reliable indicators of surface-water temperatures in 

the Recent and Pleistocene epochs, it should be possible 

to trace southward into the tropics layers or beds of 

foraminiferal ooze that are the time equivalents of 

glacial marine zones. Such layers of foraminiferal ooze 

could then be correlated with the layer of globigerina 

ooze in the tropics that Schott 9 identified as a relatively cold-water deposit that probably represents the 

last glacial epoch of the Pleistocene.

The study of climatology as well as geology may be 

advanced by the information to be derived from long 

sea-bottom cores. Significant evidence bearing on postglacial climatic changes may be obtained from minutely 

detailed study of the Foraminifera in cores taken in 

parts of the ocean where postglacial sedimentation has 

been comparatively rapid, as, for example, near the 

seaward edge of the blue-mud zone. On the assumption that such sediment accumulates at an essentially 

uniform rate, climatic fluctuations may be located approximately in time within the postglacial interval and 

may be correlated from place to place along the ocean 

margins from the Arctic to temperate or even tropical 

latitudes and perhaps also from continent to continent.

Archeology, also, might profit from the knowledge 

of a relatively tuned and correlated sequence of climatic changes, for such changes may well have made a 

significant impress on the habits and migrations of 

peoples, particularly those that dwelt in regions where 

small changes in either temperature or rainfall were 

critical. As I have pointed out in an earlier paper, 10 

students of archeology and early history, particularly in 

the Mediterranean region, might profit much from 

detailed studies of long cores of the sediment in the 

deep basins of the Mediterranean. In cores from that 

sea, as elsewhere, changes in the foraminiferal faunas 

would indicate climatic changes, and the sediments 

would yield, in addition, evidence of volcanic eruptions 

and earthquakes. The time when the Sahara became 

a desert should also be recorded in the Mediterranean 

sediments by wind-blown sand. Such a change might 

conceivably be integrated with the wealth of archeo-

• Schott, W., Die Foraminiferen in dem aquatorialen Teil des Atlantischen Ozeans: 

Wiss. Ergeb. Deutschen Atlantischen Exped. Meteor, 1925-27, Band 3, Tell 3, Lief. 1, 

pp. 120-128, 1935.

10 Bradley, W. H., Mediterranean sediments and Pleistocene sea levels: Science 

new ser., vol. 88, pp. 376-379, 1938.

XIII
XIV GENERAL INTRODUCTION

logical records of the region, and the later volcanic 

eruptions and earthquakes might be correlated with 

early history.

Some of the problems sketched so briefly here are 

touched upon in the several chapters of this report, 

but most of them must be left for future investigators. 

Nevertheless, methods by which such problems may 

be attacked are described and discussed at considerable 

length, particularly in the chapters on "Lithology and 

geologic interpretations" and "Foraminifera."

LOCATION OF THE CORE STATIONS

The cores were taken along a slightly irregular line 

between the easternmost part of the Newfoundland 

Banks and the banks off the southwest coast of Ireland, 

as shown in plate 1. Each core obtained by the Piggot 

coring device is numbered to correspond with the station 

number of the cable ship Lord Kel/in. Stations 1 and 

2 were trial stations at which preliminary tests were 

made to familiarize the crew with the apparatus, and 

no cores were preserved. The 11 cores studied are 

numbered consecutively, 3 to 13. The relation between

M. N. Bramlette, J. A. Cushman, L. G. Henbest, K. E. 

Lohman, and P. D. Trask. As the biologic phase of 

the work progressed it became evident that other 

organisms than the foraminifers and diatoms should be 

studied. Accordingly Mr. Henbest invited Dr. Willis 

L. Tressler, of the University of Buffalo, to examine the 

ostracodes, .Dr. Austin H. Clark of the United States 

National Msueum, to examine the echinoderms, and 

Dr. Harald A. Rehder, also of the United States 

National Museum, to examine the mollusks.

The organic matter content of the sediments was 

studied by Mr. Trask in collaboration with Messrs. 

H. Whitman Patnode, Jesse LeRoy Stimson, and John 

R. Gay, all members of the American Petroleum 

Institute.

As part of a comprehensive research project on the 

distribution of selenium in marine sediments and the 

soils derived from them Dr. H. G. Byers and Mr. Glen 

Edgington, of the Bureau of Chemistry and Soils, 

United States Department of Agriculture, made complete chemical analyses of 20 samples from these deepsea cores. These analyses, together with analyses of

w.

ST JOHNS 

NEWFOUNDLAND 

Meters

MID-ATLANTIC RIDGE 

" FARADAY HILLS" 

6 789

E.

LANDS END 

ENGLAND

FIGURE 1.—Profile across the North Atlantic Ocean along the line of the numbered core stations shown on plate 1.

the core stations and the submarine topography is 

shown in figure 1, which is a profile along the dashed 

line in plate 1 that connects the stations and extends 

from St. Johns, Newfoundland, to Lands End, England. 11

TABLE 1.—Geographic location, length of the cores, and depth of 

the water from which they were taken

Core number

3.-.....— ...........................

I...................... .. .

5................................ ...

6...-..-...-.....— ................

7... ............ ......................

8............................. ...

9 ...................................

10... .................................

n......... ............. .

12... ...._.___ ........... ...

13............................... .

Depth 

of water 

(meters)

4,700

3,955

4,820

4,125

3,250

1,280

3,745

4,190

4,820

3,230

1,955

Length 

of core 

(meters)

2.81

2.71

2.82

2.90

2.62

1.24

2.76

2.97

.34

2.43

9 91

Lat. N.

46°03'00"

48°29'00"

48°38'00"

49°03'30"

4Q°39'ftft"

49°36'00"

49°40'00"

49°45'00"

48°38'00"

49°37'00"

dQWKz'nn''

Long. W.

43°23'00"

35°54'30"

36°01'00"

32°44'30"

9Q°91 'OH"

98° Wflfl"

98° 90' On"

23°30'30"

17°09'00"

13°34'00"

i Qooo'nfl"

PERSONNEL AND COMPOSITION OF THE REPORT

At the request of Dr. C. S. Piggot, of the Geophysical 

Laboratory of the Carnegie Institution of Washington, 

the following six members of the United States Geological Survey undertook a systematic study of the 11 

deep-sea cores from the North Atlantic: W. H. Bradley,

11 Data for plate 1 and figure 1 were taken from International Hydrographic Bureau, 

Carte Generate Bathymetrique des Oceans, 3d ed.. sheets A-l and B-l, copies of 

which were furnished by the U. S. Hydrographie Office.

samples from several other deep-sea cores and a discussion of the occurrence of selenium, are included in 

the chapter on "Selenium content and chemical 

analyses."

METHODS OF SAMPLING AND EXAMINATION

The Piggot coring device 12 takes the cores in brass 

sampling tubes that have an inside diameter of 4.9 cm. 

As soon as a core is taken, the tube is cut off at the 

approximate length of the core and sealed. The cores 

here discussed were opened under Dr. Piggot's direction 

at the Geophysical Laboratory of the Carnegie Institution of Washington. A longitudinal cut was made 

along one side of each brass core barrel by means of a 

milling cutter so adjusted that it did not cut quite 

through the wall of the tube. The thin strip remaining 

was then ripped out without letting brass chips get 

into the core. After allowing the mud cores to dry 

somewhat, but not enough to shrink away from the 

tube walls, the cores and core barrels were cut in half 

longitudinally with a metal-cutting band saw. In this 

cutting, the milled slot was held uppermost so t^hat the 

saw cut only the lower wall of the core barrel and 

threw the cuttings downward, away from the core.

" Piggot, C. S., Apparatus to secure core samples from the ocean bottom: Qeol. 

Soc. America Bull., vol., 47. pp. 675-684,1936.
GENERAL INTRODUCTION XV

Each half core then remained undisturbed in its half 

cylinder cradle of brass core barrel. (See pi. 2.)

As several months elapsed between the time the cores 

were opened and the time this investigation began, the 

mud had dried thoroughly when Mr. K. E. Lohman 

took a succession of overlapping photographs of each 

core, about one fifth natural size. These photographs 

were then assembled as a key chart upon which were 

marked the parts from which samples for all phases of 

the investigation were taken. The dried segments of 

mud shifted somewhat from their original places each 

time samples were removed, though care was taken

to see that during sampling the segments kept their 

original order and orientation. By reference to this 

photographic key the findings of all the investigators 

have been correlated.

Most of the material was hard enough to be sawed 

into blocks with a hack saw, but a few of the most 

friable parts were sampled with small channel-shaped 

scoops of sheet metal after the loose material on the 

surface had been brushed away.

Samples for ah1 phases of this investigation were 

taken from only one half of each core, the other half 

being held intact in the Geophysical Laboratory.

GEOLOGICAL SURVEY

60° (Follows p. XV) PROFESSIONAL PAPER 196 PLATE 1 10°

60C

40°

Sea level to 

500 meters

500-2,000 

meters

2,000-4,000 

meters

4,000-6,000+ 

meters

BATHYMETRIC CHART OF A PART OF THE NORTH ATLANTIC OCEAN.

The numbered circles indicate the core stations. The dashed tine connecting them is the line of the profile shown in figure 1. The light dotted line along the coasts is the 200-mete depth contour. The usual limit of drift ice is shown by the heavy dotted line. The small triangles indicate the position of icebergs reported far beyond their normal rang during the period January 1900 to July 1916, according to information compiled by J. T. Jenkins (A Textbook of Oceanography, fig. 14, London, Constable & Co., 1921).

U.S. GOVERNMENT PRINTING OFFICE : 1940—O-22S324

GEOLOGICAL SURVEY PROFESSIONAL PAPER 19G PLATE 2

6 a 9 10

w.

2 J

Meters

LONGITUDINAL SECTIONS OF THE AIR-DRIED CORES. 

Half of the core barrel was removed from core 11, but the core itself was not cut. Photograph by Geophysical Laboratory, Carnegie Institution of Washington.

GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES 

BETWEEN NEWFOUNDLAND AND IRELAND

PART 8. ORGANIC MATTER CONTENT

By P. D. TRASK, H. W. PATNODE, J. L. STIMSON, and J. R. GAY

INTRODUCTION

This report presents the results of a study of the 

organic constituents of samples of deep-sea sediments 

collected in 1936 in the North Atlantic Ocean by Dr. 

C. S. Piggot of the Geophysical Laboratory of the 

Carnegie Institution of Washington with his gun core 

sampler. The investigation was undertaken at the 

request of the Geological Survey and is the joint work of 

the Geological Survey and the American Petroleum 

Institute. Mr. Trask is a member of the staff of the 

Geological Survey, and Messrs. Patnode, Stimson, 

and Gay, at the time the investigation was made, were 

members of the staff of American Petroleum Institute 

Research Project 4 on the Origin and Environment of 

Source Sediments of Petroleum.

Mr. Trask wrote the report and, with Mr. Patnode, 

organized the general program of work. Mr. Patnode 

compiled the data and prepared the charts and tables. 

Messrs. Stimson and Gay made the chemical analyses. 

The chemical work was done in a laboratory placed at 

the disposal of Project 4 by the Division of Industrial 

Farm Products Research of the Bureau of Chemistry 

and Soils of the United States Department of 

Agriculture.

METHODS OF STUDY

This investigation is based on the determination of 

the nitrogen content and reduction number, as defined 

later, of 123 samples from 11 cores. Owing to the program of the regular work of Project 4 at the time the 

samples were being studied time and facilities did not 

permit a detailed study of the organic content of 

these samples, and the work was therefore limited to the 

determination of the nitrogen content and reduction 

number. Neither the nitrogen content nor reduction 

number is an exact measure of the quantity of organic 

matter in sediments; at best these properties are only 

crude approximations. Their significance with respect 

to the organic content is discussed elsewhere. 1

1 Trask, P. D., Inferences about the origin of oil as indicated by the composition 

of the organic constituents of sediments: U. S. Geol. Survey Prof. Paper 186-H pp. 

149-154, 1937; Organic content of recent marine sediments, in Recent marine sediments, pp. 428-453, Am. Assoc. Petroleum Geologists, Tulsa, Okla., 1939.

A final report by P. D. Trask and H. W. Patnode embodying the results of the 

extensive research program carried out by the American Petroleum Institute and the 

United States Geological Survey is being prepared for publication by the American 

Association of Petroleum Geologists under the title "Source beds of petroleum."

401264—42——

NITROGEN CONTENT

Nitrogen was determined by a slight modification of 

the Kjeldahl-Arnold-Gunning method,2 which consists 

of converting the nitrogen compounds to ammonia by 

digestion with sulfuric acid, making the solution alkaline with sodium hydroxide, distilling, catching the 

ammonia in hydrochloric acid, and titrating with sodium 

hydroxide. All the determinations were duplicated 

and many were made in triplicate. The results are 

presented in terms of the arithmetic average or mean 

of the results obtained. They are given to two significant figures, but the second figure is of doubtful value. 

The average (median) deviation of individual determinations from the means, which are reported in table 30, 

is 0.0012 percent of the total weight of the sediments. 

As the average nitrogen content is 0.022 percent of the 

weight of the sediments, the average deviation of the 

individual samples from the mean is 0.0012/0.022, 

or 5.5 percent. When averages of several samples are 

considered this quantity is reduced approximately as the 

inverse of the square root of the number of samples 

considered. Thus the probable error of an average 

based on 10 samples is 5.5/VlO or 1.7 percent, which, 

for the purpose of this investigation, is a relatively insignificant quantity.

The nitrogen content in some ways seems to be a more 

suitable index of the organic content of sediments than 

is the reduction number, but on the whole it probably 

is not materially superior. The main advantage of 

nitrogen is its restriction almost entirely to the organic 

constituents, whereas the reduction number is influenced to some extent by the inorganic substances. 

Nitrogen, however, represents only a small part of the 

organic matter, thus necessitating the use of a large 

factor for estimating the organic content. Moreover, 

the percentage of nitrogen in the organic constituents 

of different sediments varies, thus introducing errors in 

the calculation of the organic content when a constant 

factor is used.

The nitrogen content of the organic constituents of 

recent marine sediments has not yet been studied adequately, but the available evidence seems to indicate

2 Official Methods, Assoc. Official Agr. Chem., 2d ed., p. 81, 1925. Trask. P. D., 

and Patnode, H. W., Source beds of petroleum (see footnote 1).

135
136 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

that on the average nitrogen forms about 5.5 percent of 

the weight of the organic matter and in most sediments 

ranges between 4.5 and 7 percent; however, in some 

deposits it may be as low as 3 percent and in others 

as high as 10 percent.3

If nitrogen forms 5.5 percent of the organic matter, 

the organic content of the sediments would be 100/5.5, 

or 18 times the nitrogen; that is, the organic content 

could be estimated by multiplying the nitrogen content 

by a factor of 18. Similarly nitrogen contents of 4.5 

and 7.0 percent correspond to factors of 22 and 14, 

respectively, and contents of 3 and 10 percent are 

equivalent to factors of 33 and 10, respectively. Thus, 

if a single factor of 18 is used for determining the organic 

content, for most sediments the figure obtained will be 

within %8 or about 20 percent of the true quantity, but 

for some sediments it may be in error by as much as 50 

percent.

The significance of the organic content as estimated in 

this way, therefore, must be interpreted with due consideration of the degree of reliability of the data. Small 

differences in nitrogen content, such as 5 percent or less, 

without supporting evidence from another source, cannot be considered as indicating any distinctive difference in organic content, but if the difference in nitrogen content between two or more sediments is considerable, that is 30 percent or more, the organic content of the sediments in all probability is different. If 

the averages of several sediments are considered, the 

chance for anomalous interpretations decreases more 

or less inversely as the square root of the number of 

sediments averaged. Therefore, if the chance for error 

is 20 percent for an individual sediment, it would be of 

the order of 20/VlO, or 6.3 percent, for an average 

based on 10 samples; also, if the averages of two series 

of 10 samples differ by as much as 10 percent the chances 

are greatly in favor of their content of organic matter 

being different. However, in view of the uncertainty 

as to the actual factor to use for estimating the organic 

content from nitrogen, the variations in organic matter 

have been discussed in this paper in terms of variations 

in nitrogen content (or reduction number, which varies 

in essentially the same way as the nitrogen content), 

rather than in terms of variation in organic content. 

Only when the differences between the nitrogen content 

or reduction number of individual sediments or groups 

of sediments are distinctly different have the results 

been interpreted as suggesting real differences in 

organic content.

REDUCTION NUMBER

The reduction number, like the nitrogen content, is 

only a crude index of the organic content. The reduction number is defined as the number of cubic 

centimeters of 0.4 normal chromic acid that can be 

reduced by 100 milligrams of dried sediment under

8 Trask, P. D., Organic content of recent marine sediments, p. 431,1939.

certain standard conditions of heating.4 Formerly it 

was called the reducing power, but in view of the fact 

that it is a relative rather than an absolute measure of 

the reducing power of the sediments it subsequently 

was designated as the reduction number.5

The method of determination is a modification of the 

Schollenberger 6 method of chromic acid titration for soil 

organic matter. It consists of adding a known amount 

of 0.4 normal chromic acid to a given quantity of sediment, heating it at such a rate that the temperature 

within the mixture of chromic acid and sediment reaches 

145° C. at the end of 6 minutes, cooling, and titrating 

with 0.2 normal ferrous ammonium sulfate.7 In the 

present investigation, samples of 0.5 gram were used 

for the determination of the reduction number. The 

method, when the time and rate of heating are controlled, gives results that can be duplicated readily. 

The average deviation of duplicate samples from the 

mean of the determinations for individual samples 

studied for this report is .0069. As each drop of ferrous 

ammonium sulfate used in the titration corresponds 

to .005 unit of reduction number, this deviation for 

duplicate samples amounts to only a little more than 

one drop in the titration, which- indicates that the 

results as expressed to two significant figures are reliable insofar as errors in the method of determination 

are concerned. Since the average reduction number of 

the sediments is 0.25, the mean deviation of individual 

samples from the mean is 0.0069/0.25, or 2.7 percent.

Each unit of reduction number in recent marine 

sediments seems to be equivalent to approximately 2 

percent organic matter. This relation of reduction 

number to organic content in recent sediments has been 

investigated relatively little, but in the experience of 

the writers each unit of reduction number on the 

average corresponds to approximately 1.1 percent of 

organic carbon in the sediments.8 As the average ratio 

of organic matter to carbon in recent marine deposits 

seems to be about 1.8,9 it follows that the percentage 

of organic matter in the sediments would be roughly 

equivalent to two times the reduction number. The 

ratio of organic matter to carbon in such deposits, 

however, is not constant. Moreover, the figures of 1.8 

for the ratio of organic matter to carbon, and of 1.1 

for the ratio of reduction number to carbon may not be 

correct. In addition, the ratio of carbon to reduction 

number is known to be variable. These variations in 

the ratio of carbon to reduction number are caused by 

the fact that the quantity of organic matter in the 

sediments is not the only factor influencing the reduction

4 Trask, P. D., and Patnode, H. W., Means of recognizing source beds: Am. Petroleum Inst., Drilling and Production Practice, 1936, p. 369,1937.

6 Trask, P. D., and Patnode, H. W., Source beds of petroleum (see footnote 1).

• Schollenberger, C. J., A rapid approximate method for determining soil organic 

matter: Soil Science, vol. 24, pp. 65-68,1928; The determination of soil organic matter: 

Soil Science, vol. 31, pp. 483-480,1931.

'Trask, P. D., and Patnode, H. W., Source beds of petroleum (see footnote 1).

8 Trask, P. D., Organic content of recent marine sediments, in Recent marine 

sediments, pp. 430-433, Am. Assoc. Petroleum Geologists, Tulsa, Okla., 1939.

'Idem., p. 430.
PART 8. ORGANIC MATTER CONTENT 137

UJ 

§.040

or

o 

<

.020

of chromic acid during the process of determining the 

reduction number. Chromic acid is reduced by certain 

inorganic constituents, such as iron sulfide; the extent 

to which the organic substances are oxidized by the 

chromic acid during the process of analysis varies among 

different sediments; and the degree of oxidation or 

nature of the organic material affects the reduction of 

chromic acid. If the organic substances are in a high 

state of oxidation, relatively little chromic acid is 

reduced and if they are in a low state of oxidation, that 

is, have a high degree of reduction, relatively much chromic acid is reduced.

In ancient or lithified sediments, three 

factors, the quantity of oxidizable inorganic substances, the degree of completeness of combustion by the chromic acid, 

and the state of oxidation of the organic 

matter, cause the majority of sediments 

to deviate 20 percent or less from the 

average ratio of carbon to reduction 

number, though in some sediments they 

may cause variations of as much as 50 

percent. 10 Presumably similar variations 

apply to recent deposits, as is attested by 

the similarity in relationship of nitrogen 

and reduction number shown by figure 23. 

Both the nitrogen content and reduction 

number are independent measures of the 

organic content, yet when one is plotted 

against the other a moderately constant 

relationship is observed. Consequently, 

it seems to follow that the reduction number is of about the same order of reliability as an index of the organic content 

as is nitrogen; namely, only a crude approximation, which for most samples is 

probably within 20 or 25 percent of the 

true figure, but in some samples may 

deviate as much as 50 percent from the correct figure. 

Estimation of the quantity of organic matter in the 

sediments by the use of the reduction number, therefore, should be interpreted with due consideration of 

the uncertainties involved.

The foregoing discussion of the probable error of the 

determination of the organic content by multiplying 

the reduction number by a factor of 2, refers to calculations based on individual samples. When groups of 

samples are considered, the probable error is reduced. 

However, certain basic uncertainties are still involved, 

namely, the correctness of the ratio of organic matter to 

carbon, and of the ratio of carbon to reduction number. 

Therefore, in view of these uncertainties, the variations 

of reduction number among the different sediments 

studied in this report, wherever practicable, have been 

discussed in terms of reduction number, which is an 

empirical quantity, rather than in terms of organic

10 Trask, P. D., and Patnode, H. W., Source beds of petroleum (see footnote 1).

content, which is an interpretation. Nevertheless, 

when averages of groups of samples show similar and 

consistent differences for both nitrogen content and 

reduction number, the inference is strong that the 

quantity of organic matter in the groups of sediments is

different.

NITROGEN-REDUCTION RATIO

The ratio of the nitrogen content to the reduction 

number of ancient sediments, which is called the nitrogen-reduction ratio, has been interpreted as a crude index

tr

UJ 

Q.

.20 .40

REDUCTION NUMBER

FIGURE 23.—Relation of nitrogen content to reduction number in the samples studied.

of the state of reduction of the organic constituents of 

the sediments. 11 The line of reasoning that leads to 

this conclusion is based on the inferences that the nitrogen content is a rough measure of the organic content of 

the sediments and the ratio of the organic content to the 

reduction number is a crude index of the state of reduction of the organic substances. If the organic constituents are in a high state of oxidation they can reduce 

relatively little chromic acid, and the reduction number 

will be comparatively small. As the reduction number 

forms the denominator of the nitrogen-reduction ratio, 

a small reduction number would make the quotient 

relatively large. If the state of oxidation is low, the 

reduction number would be high and the ratio of organic 

matter to reduction number would be low. That is, 

large numbers would indicate a high state of oxidation, 

and low numbers would indicate a low state of oxidation.

11 Trask, P. D., and Patnode, H. Vf., Means of recognizing source beds: Am. Petroleum Inst., Drilling and Production Practice, 1936, p. 371,1937.
138 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

The relationship, however, is not as definite as the 

above line of reasoning would seem to indicate. The 

nitrogen content is not an exact measure of the organic 

content, because, as already indicated, the proportion 

of nitrogen varies in different sediments. Moreover, 

the effect of oxidizable inorganic substances in the sediments and the effect of the completeness of combustion 

by the chromic acid upon the reduction number have 

not been considered. The influence of these three 

factors upon the significance of the nitrogen-reduction 

ratio as an index of the state of reduction of the organic 

matter has been discussed in detail in another publication, and the conclusion was reached that, in general, 

their effect is not large. 12 Insufficient data are at hand, 

however, to warrant any definite statement as to the 

actual magnitude of their effect; moreover, the influence of these factors on recent marine sediments has 

been studied relatively little, but presumably it is not 

materially different from what it is in ancient deposits. 

In view of the uncertainties involved, the significance 

of the nitrogen-reduction ratio of recent sediments 

must, therefore, be interpreted with caution. About 

all that is safe to infer is that relatively low ratios suggest a low state of oxidation of the sediments and relatively high ratios suggest a high state of oxidation.

DESCRIPTION AND LOCATION OF SAMPLES

A proper description of the results of the work should 

include an account of the general nature of the samples, 

but as this subject has been discussed in detail in other 

parts of this professional paper only a brief summary is 

included here. The samples were collected in the 

spring of 1936 by C. S. Piggot (see Foreword, pp. 

xi-xn) with his gun sampler, which can take cores as 

much as 10 feet in length. Samples were obtained at 

fairly regular intervals along a nearly straight line about 

latitude 49° N., between the Grand Banks, Newfoundland, and Lands End, at the southwest end of England. 

The actual locations are indicated in plate 1 of the 

introductory chapter. Their general position is also 

indicated on the profile shown in figure 27 of this report. 

Eleven cores were obtained. They were taken in water 

that ranges from 1,280 to 4,800 meters* (700 to 2,640 

fathoms) in depth. Most of them came from water 

more than 3,000 meters deep, but one, number 8, was 

procured from the crest of the mid-Atlantic ridge, in 

water only 1,280 meters deep. The core material 

obtained ranged from 30 to 300 centimeters in length. 

At locality 10, the coring device buried itself in the 

mud, and an unknown quantity of the sediment was 

lost through the water ports at the top of the device.

As indicated by the work of Bramlette and Bradley 

on the lithologic character and geologic interpretations 

of the cores (see pt. 1, pi. 3), the samples are nearly 

all rich in calcium carbonate, and many are classified 

as foraminiferal marl and globigerina ooze. One core,

12 Trask, P. D., and Patnode, H. W., Source beds of petroleum (see footnote 1).

number 3, taken from near the edge of the Grand Banks, 

contains considerable terrigenous debris, and another, 

number 11, encountered altered basalt at a depth of 30 

centimeters below the top of the core. West of the 

mid-Atlantic ridge, two volcanic ash horizons were 

recognized, one at a depth that ranged between 10 and 

50 centimeters beneath the surface of the deposits and 

the other at a depth of about 2 meters. East of the 

mid-Atlantic ridge only the upper of these two ash 

horizons has been recognized. These ash zones are 

particularly helpful in correlating the sediments in the 

different cores.

In addition to the ash horizons noted, pebbles and 

rock fragments are present in definite zones of sandy or 

silty sediment that contains relatively little carbonate. 

Bramlette and Bradley have recognized four such zones 

and regard them as of glacial or ice raft origin. Gushman and Henbest record (see pt. 2, figs. 11-21) the 

occurrence of cold-water Foraminifera in these pebbly 

zones, and this corroborates the concept of glacial origin. 

These zones, characterized by pebbles, rock fragments, 

sand, and silt, are designated in this paper as cold zones. 

The zones between the cold zones are called warm zones. 

These zones have been recognized in all the cores west 

of the mid-Atlantic ridge, but east of the ridge only the 

uppermost cold zone has been recognized. In core 3, 

near the edge of the Grand Banks, the uppermost cold 

zone has not been reached even at the bottom of the 

core at a distance of nearly 3 meters beneath the surface 

of the deposits. For convenience, the zones are 

numbered consecutively from the top downward. (See 

table 31.)

The general distribution of these cold zones is indicated on figure 24. The consistency with which they 

may be traced from core to core affords a means of correlating sediments of similar age and thus aids in the 

investigation of the lateral variation in the deposits 

at different depths.

The sediments in general contain about 50 percent 

calcium carbonate, though the quantity ranges from 

10 to 90 percent. Some of the samples are sandy, particularly those from^core 8 on the crest of the midAtlantic ridge.

The positions of the samples that were selected for 

study are shown in figure 24. In all, 123 samples were 

chosen. Samples were procured first from places near 

the top, middle, and bottom of each core, except the 

one (core 11) that penetrated the basalt. The results 

of the analyses of these first samples did not indicate 

any consistent trend with depth, but by the time they 

were analyzed the temperature zones had been recognized. Consequently, it seemed worth while to analyze 

samples in each core from each of the 9 temperature 

zones. Also, it was desirable to ascertain whether or 

not there was any change with depth in the individual 

warm and cold zones. Accordingly, an attempt was 

made to procure at least two samples from each of the
PART 8. ORGANIC MATTER CONTENT 139

CO 

K 

UJ

H

UJ

2

/IS

/ 18

FIGURE 24.—Location of samples in cores. Vertical columns represent the numbered cores. (For location of cores see pi. 1 and fig. 1.) Black rectangular blocks represent 

position of samples studied; numbers opposite these blocks are the numbers of the samples. Diagonally ruled bands extending across the figure represent cold zones. 

Warm zones lie between the cold zones.

nine stratigraphic zones. However, by this time considerable material had already been removed from certain parts of the cores, and it was not possible to obtain 

some of the samples desired. Special effort was made 

to procure samples from the surface of the sediments 

in each core. However, top material could be obtained 

only from cores, 4, 7, and 8. In all other cores, except 

cores 3 and 10, the uppermost sample came from within 

10 centimeters of the top of the core. In core 3 the 

first sample was taken 20 centimeters below the top, 

and in core 10 an unknown amount of the uppermost 

part of the core had been lost at the time the core was 

taken.

RESULTS

BASIC DATA

The results of the analyses are presented in table 30. 

This table contains the average of the determinations 

of tbe nitrogen and reduction number of each sample 

and the nitrogen-reduction ratios based on these 

average values. The table includes two forms of 

averages for the samples for each of the 11 cores, 

namely, the mean and median. The mean represents 

the sum of the determinations for the individual 

samples divided by the total number of samples. 

The median represents the middle determination with 

respect to all samples considered for the individual 

cores. Half the samples in any individual core have 

values larger than the median, and half have values 

smaller than the median. The median is particularly 

significant for ratios, such as the nitrogen-reduction 

ratio, and also for size distributions in which most of

the samples have about the same average value, but a 

few are very much larger or smaller than the others.la

TABLE 30.—Average values of the nitrogen content, reduction 

number, and nitrogen-reduction ratio

Core 3

Sample number

T-l

T. 2

T-3

T-4____________-___-_____

T-5

T-6 _

T-7

T-8

Median. __

Nitrogen 

(percent)

0 051 

054 

044 

042 

035 

034 

031 

034 

041 

039

Reduction 

number

0 43 

50 

52 

51 

43 

40 

35 

45 

45 

44

Nitrogenreduction 

ratio

11.8 

10.8 

8.5 

8.2 

8. 1 

8. 5 

8.9 

7.6 

9. 1 

8.5

Core 4

T-9

T-10— „ — - — --- — ------

T-ll

T-12___________--________

T-13- — -----------------

T-14__ ___________________

T-15- — -----------------

T-16____ — - — ---- — — — --

T-17__ —— -_ —— -------

T-18__ — ---------------

T-19—— -----------------

T-20____ — -_ — — — - — — — T-21

T-22

T-23—— ------- ---------

0 014 

021 

013 

020 

035 

023 

017 

025 

024 

014 

039 

031 

036 

017 

021 

023 

021

0 23 

24 

16 

25 

31 

22 

16 

24 

24 

17 35- 

32 

40 

25 

23 

25 

24

6. 1 

8.7 

8. 1 

8.0 

11.3 

10. 5 

10. 6 

10.4 

10.0 

8. 2 

11. 1 

9. 7 

9.0 

6. 8 

9. 1 

8.9 

9. 1

i 3 For further details on the respective values of the mean and median, see any text 

book of statistics, such as Chaddock, R. E., Principles and methods of statistics, 

pp. 81-124, New York, Houghton Mifflin Co., 1925.
140 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

TABLE 30. — Average values of the -nitrogen content, reduction 

number, and nitrogen-reduction ratio — Continued

Core 5

Sample number

T-24

T 25——— ----------------

T-26

T-27

T-28—— ..-----.-__--_--

T-29——— ----------------

T-30- —— ----------------

T-31 __ --_-_----________

T 32

T-33——— ----------------

T-34— _ -----------------

T-35_——— ---------_-____

T-36 -_ -__

T-37—— _ ---------------

T-38— ------------------

«

Nitrogen 

(percent)

0. 029 

.024 

. 014 

.010 

.020 

.024 

.022 

.011 

.021 

. 018 

. 017 

. 021 

. 021 

.018 

.015 

. 019 

.020

Reduction 

number

0. 25 

. 26 

. 18 

. 13 

. 30 

.32 

.25 

. 16 

.26 

. 17 

. 21 

.29 

. 26 

.26 

.20 

.23 

.25

Nitrogenreduction 

ratio

11. 6 

9. 2

7. 8 

7.7 

6. 7 

7.5 

8. 8 

6.9 

8. 1 

10. 6 

8. 1 

7.2 

8. 1 

6.9 

7. 5 

8.2 

7. 8

Core 6

T-39 __ __-_-_---___-_--__

T-40

T-41

T-42

T-43_——— __ — ——— _ — __-

T-44

T-45— _ — -_ — — - — .—— T-46

T-47

T-48- — _----_-_---_---..

T 4.Q

T-50

T-51— ------------------

T-52 --------

Mean _ .__

0.028 

. 022 

.028 

. 030 

.028 

. 010 

. 024 

.021 

.009 

.026 

.031 

. 025 

. 019 

. 023 

.023 

. 025

0. 25 

.25 

.26 

.37 

. 32 

. 17 

.27 

. 29 

. 18 

.30 

. 37 

. 26 

. 24 

. 19 

. 26 

. 26

11. 2 

8. 8 

10. 8 

8. 1 

8.7 

5. 9 

8. 9 

7.2 

5.0 

8.7 

8.4 

9.6 

7.9 

12. 1 

8.7 

8.7

Core?

T-53—— ------------------

T-54

T-55— _„ --- —— __-_-

T-56—— --------__----__-

T-57 -._ _ _ _

T-58

T-59——— —— — __- — — -

T-60— ------------------

T-61 __-_-_--__-

T-62 -----

T-63— ------------------

T

C A

T- fi*i

T-66-. -----------------

T fi7

l\^o/4i OTi

0.018 

.018 

.019 

. 021 

. 013 

. 014 

. 007 

. 019 

.019 

. 025 

. 014 

. 007 

. 009 

.008 

.014 

.015 

. 014

0. 17 

.20 

. 24 

. 21 

. 16 

.23 

. 13 

. 17 

. 19 

. 28 

. 19 

. 14 

. 16 

. 14 

. 19 

. 19 

. 19

10. 6 

9.0 

7.9 

10. 0

8. 1 

6. 1 

5.4 

11.2 

10. 0 

8.9 

7.4 

5.0 

5.6 

5.7 

7.4 

7.9 

7.9

CoreS

T-68— ------------------

T-69— ------------------

T-70— _-_-_-_--_---_----

T-71-— -----------------

T-72 -___

T-73 - --.

T-74

T-75— ___-_-__--_---__--

T-76-— ---__-_-__-----__

0. 009 

.005 

. 008 

. 005 

.008 

.011 

.008 

. 017 

.007 

.009 

. 008

0. 17 

. 10 

. 11 

. 11 

. 12 

. 12 

. 10 

. 15 

.07 

. 12 

. 11

5.3 

5.0 

7.3 

4.5 

6.7 

9.2 

8. 0 

11.3 

10.0 

7.5 

7.3

TABLE 30. — Average values of the nitrogen content, reduction 

number, and nitrogen-reduction ratio — Continued

Core 9

Sample number

T-77

T-78——— -_-_-_- — — — —

T-79

T-80

T 81 -

T-82 -

T-83

T-84— __ — _-- ———— _ — __

T-85

T-86

T-87—— -----------------

T-88

Mean

Nitrogen 

(percent)

0.037 

. 026 

. 031 

.024 

.051 

. 019 

.028 

.030 

.025 

.029 

.025 

.032 

.030 

.029

Reduction 

number

0. 49 

. 54 

. 41 

.45 

.53 

.49 

. 54 

.57 

. 53 

.45 

.45 

.40 

.49 

.49

Nitrogenreduction 

ratio

7.5 

4. 8 

7. 6 

5.3 

9. 6 

3.9 

5.2 

5. 3 

4. 7 

6.4 

5. 6 

8.0 

6.2 

5. 5

Core 10

T 89

T-90

T 91

T-92——— _-_--__----__---

T-93

T 94

T-95——— --_---_-----_-_-

T-96— ----__---_-__-___-

T-98——— -_ — _- — — —— __

T 99

0. 032 

. 023 

. 026 

. 024 

.021 

.032 

. 012 

. 020 

.029 

. 030 

.029 

.025 

. 026

0. 43 

.48 

.43 

.28 

.35 

. 31 

. 19 

.35 

. 27 

.47 

.38 

.36 

.35

7.4 

4. 8 

6.0 

8. 6 

6.0 

10. 3 

6.3 

5.7 

10. 7 

6.4 

7. 6 

7.3 

6.4

Core 11

T-100— ----------------- 0.019 0.26 7.3

Core 12

T-101

T-102—— ----------------

T-103— -----------------

T 104— -----------------

T 105— -----------------

T-106-- ----------------

T-107— -----------------

T 108

T 1DQ

T 1 10

T 111

"]\TQQ f~t

Median

0. 029 

. 050 

.053 

.032 

.035 

.049 

. 036 

. 040 

.038 

. 027 

. 032 

. 038 

. 036

0. 24 

.35 

. 51 

. 36 

.49 

.48 

. 38 

.39 

.34 

.25 

.22 

.36 

.36

12. 1 

14.3 

10.4 

8. 9 

7. 1 

10.2 

9. 5 

10. 2 

11.2 

10.8 

14. 5 

10.8 

10.4

Core 13

T-112— -----------------

T-113—— ----------------

T-114 _ -__

T-115——— - — — _- — — _

T 116

T-117

T

1 1 C

T-119- ——— --------------

T-12U——— __ — — _ — __- —

T-121

T 199

T-123

General mean __

General median _-__

0.019 

.021 

.022 

.015 

.020 

.018 

.014 

. 015 

.020 

.017 

. 018 

.014 

.018 

-.018

.023 

.022

0. 11 

. 18 

. 21 

. 13 

. 14 

. 14 

. 12 

. 11 

. 14 

. 14 

. 15 

. 12 

. 14 

. 14

/.28 

.25

17.3 

11.7 

10.5 

11.5 

14.3 

12.9 

11.7 

13. 6 

14. 3 

12. 1 

13.0 

11.7 

12.8 

12. 1

8.7 

8. 6
PART 8. ORGANIC MATTER CONTENT 141

The areal and vertical distribution of the data are 

indicated graphically in figures 25 and 26. All the 

samples contain little organic matter. The nitrogen 

content ranges from 0.005 to 0.054 percent, and the 

reduction number ranges from 0.07 to 0.57. The 

median nitrogen content is 0.022 percent, and the 

median reduction number is 0.25. The respective 

means are 0.023 and 0.28. These data indicate that the

organic content of the sediments ranges from about 0.1 

percent to 1.0 percent, and the average is approximately 

0.5 percent. These quantities of organic matter are of 

the same order of magnitude as previously reported 

from deep-sea deposits 14 but are much less than for

14 Trask, P. D., Origin and environment of source sediments of petroleum: pp. 116- 

118, Houston, Texas, Gulf Publishing Co., 1932. Correns, C. W., Die Sedimente des 

ftquatorialen Atlantischen Ozeans: Wiss. Ergeb. Deutschen Atlantischen Exped~. 

Meteor, 1925-27, Band 3, Tell 3, Lief. 2, p. 236, 1937.

8 10 12 13

ID

=3

Zl

(O

o:

UJ

lu

13

H

^\

Zl

Zl

9

3 L

Zl

Z]

Zl

.IOO PERCENT

FIGURE 25.—Chart showing areal and vertical distribution of nitrogen in sediments in cores 3 to 13. Unshaded horizontal rectangular blocks indicate nitrogen content of 

samples. Position of these blocks indicates the respective location of samples in the cores. Vertical shading in core column represents limits of cold zones as determined by Bramlette and Bradley (see pt. 1 of this professional paper, pp. 2-7). Warm zones lie between the cold zones.

8 10 12 D"

co 

a: 

u

H 

Ul

=1

Zl

a

Zl 

zn

Zl

1.0 UNIT

FIGURE 26.—Chart showing areal and vertical distribution of reduction number in sediments in cores 3 to 13. Unshaded horizontal rectangular blocks represent the

reduction number of the samples. See figure 25 for description of other features of figure.
142 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

sediments deposited near shore, which ordinarily contain from 1 to 7 percent and have an average organic 

content of about 2.5 percent. 16

RELATIONSHIPS

SURFACE LAYERS

The organic content of the sediments nowiorming on 

the sea floor as indicated by the uppermost samples 

procured from each core is clearly related to the configuration of the sea bottom (fig. 27). The sediments on 

exposed places on the sea floor, such as the sediments in 

core 8 on the mid-Atlantic ridge, and in core 13, on the 

edge of the ridge near the east end of the profile, contain 

distinctly less organic matter than the sediments in cores

3. 9, and 12, from the abyssal deeps. The organic 

content of the sediments on the ridges is 0.2 to 0.3 

percent, compared with 0.3 to 1.0 percent in the deeps. 

Organic matter is relatively buoyant and is easily transported by currents. Consequently, if currents cross 

these ridges the sediments may be agitated, with the 

result that organic and fine-grained inorganic constituents will tend to be carried away and deposited in 

areas of quiet water. Evidence has been obtained from 

many other areas to the effect that sediments on ridges 

and exposed places on the sea floor, regardless of depth 

of water, are relatively coarse-grained and contain comparatively little organic matter, 16 The organic content 

of the sediments on the ridges in the Atlantic Ocean is 

small compared with that in the adjacent deeps.

The organic content of the sediments in the abyssal 

deeps varies somewhat, but owing to the small number 

of cores and to inadequate information on the submarine 

topography little can be inferred about the relation of 

the organic content to the configuration of the bottom 

along the part of this profile that represents the abyssal 

deeps. The sediments for a few hundred miles east of 

the mid-Atlantic ridge, however, seem to have a greater 

organic content than those for a similar distance to the 

west. The average nitrogen content of the uppermost 

samples contained from cores 9 and 10, east of the ridge, 

is 0.036 percent, compared with 0.022 percent for cores

4. 5, 6, and 7, west of the ridge. The corresponding 

averages for the reduction number are 0.46 and 0.23. 

The apparently greater organic content east of the 

ridge may perhaps be due to a greater supply of organic 

matter in the water.

SUBSURFACE LAYERS

The organic content of the sediments does not show 

any consistent decrease with depth of burial. In fact, 

as illustrated by table 30 and figures 25 to 27, the organic content is more or less constant throughout the 

length of the individual cores, except for core 3, in which 

it appears to diminish slightly with depth. These 

observations are not in accord with the common con15 Trask, P. D., op. cit., pp. 118-120.

i» Trask, P. D., op. cit., pp. 83-95, 110-172.

cept that the organic content of sediments decreases 

with the length of time the deposits have been buried. 

Loss of organic matter in the upper layers of sediments 

results mainly from decomposition caused by animals 

and microorganisms, which require a supply of oxygen 

in order to live. The source of oxygen is the water overlying the sediments. The more the sediments become 

removed from the overlying water by burial, the less 

is the supply of oxygen in the deposits. The available 

oxygen is probably used up rather rapidly in the surface 

layers of the sediments and at an increasingly slower 

rate with increasing depth of burial. Consequently, 

most of the loss in organic content due to microorganisms and animals seems to take place in the upper few 

inches of the deposits; in fact, observations on a considerable number of core samples of Recent near-shore 

sediments from many parts of the world suggest that 

the average loss in organic content is about 15 percent 

in the upper 12 inches (30 centimeters) of the deposits. 17

The deep-sea sediments studied in this report, with 

the possible exception of core 3, were deposited so 

much more slowly than most near-shore sediments 

that in order to detect any decrease in organic content 

it probably would be necessary to analyze several 

samples from the upper few centimeters or millimeters 

of the deposits. As most of the samples considered 

in this report were taken at intervals of several centimeters, perhaps no detectable decrease in organic 

content should be expected. Moreover, the problem 

of loss in organic content with burial is complicated 

by the uncertainty as to how much organic matter was 

in the sediments at the time they were deposited. The 

different subsurface layers may have had different 

organic contents at time of deposition.

The sediments in core 3, as described below, probably 

accumulated at a more rapid rate than the others, and 

the apparent decrease in organic content may actually 

represent loss with burial. A decrease in organic content with depth in core 3, though suggested, is not certain, even granting that the organic content of all the 

layers of sediment was the same at time of deposition. 

The nitrogen content decreases from 0.051 percent in 

sample T-l, near the surface of the deposits, to 0.035 

percent in sample T-5, about the middle of the core, 

below which it is more or less constant. The reduction 

number, on the other hand, varies irregularly between 

samples T-l and T-5 and does not indicate a consistent 

decrease. Both the nitrogen content and reduction 

number are rough measures of the organic content, 

and one can take his choice as to which he thinks is the 

more significant. The nitrogen content, as mentioned 

above, is affected less by the inorganic constituents 

and possibly is the more reliable.

Though the sediments do not seem to show any general change for depth of burial, the organic content of 

the sediments in cores 8 and 13, taken near the crests

" Trask, P. D., op. cit., pp. 205-208.
PART 8. ORGANIC MATTER CONTENT 143 ^1 6

LJ a ° 

« S ® »*

on oo 

oo

o> oo <M 10 

o o

I Q w

h- 

|c- o Z

Ip8

ox tr

loo in 

|5q Z 

UJ

cr

UJ l**l

CM =3O

in to O

<M <NI UJ ' ' QC.

g£

CC

2 N Q

!* S

I"of s

tod'£ O

•§

T3 S03 I1 WSdW

o S

(0

UI

_l Zo

t

co T) J

T)S03

E RS

SCALE

wfoundland,

*~ g. ^

ui ui

H J2

< d

z s §

° i S « d

-1 0. 03

0. _£ < o

fl

- 1!>"S

Xi £

CO•^

0 a.

S2

.2S

§ £8101gda

<o

> o

•ii

X!

the andnum%0>s

"o

d 

.SS

""

ft 1

<x> ft£

_dI~

g

1 

.d

03

g 

<x>

X!

S2

O)

X!|Oa

<x>

,dSS03

I 

'•31

<D

O>

.g

"o h1S

8 ftft

ninu

<ubeoM

'3

"o

<D

be 

o3fl"8

D.

T)iI11 o

a Sa aD5

+•*

"S

Ai

S2 I1Sft ftD

o> AOO

umber rati on ddo

reducti "er to?t4

S-i

•2sa§1p< aD1_

oT i&13d0

1sT3

nitrogen-re e A-^>o&"S

t4 1

X! Dd

§3 ftftD

o>

ftoi

> '-3 « 3

..3 « „

to co fl

« 2

"3 o .2 ® >• S

o3 53 .S S1 '-S <c

^3 03 co a) g 43

I a. ui

s oc < o

V) O

fc S d § s f

oi a) '^2 i! d B

-d ^ d *^ co

« d « "g « co to S M ? ® & S g> £ ^ '-S -a 

o ^ §"03 S S o3 •« fc< d M o3

O CQ 03 co OT

^ T) § » ^ S

ll^tS 5Bll|2 ri ii: +^> CQ Q^ o

S -9 si _ x! °

« S i- s

S3

NHOP 'is I
144 GEOLOGY AND BIOLOGY OP NORTH ATLANTIC DEEP-SEA CORES

of ridges, is consistently lower throughout the cores 

than it is in adjacent cores taken in deeper water. The 

older sediments in the cores, therefore, seem to have 

the same relationship to the submarine configuration as 

do the sediments near the surface of the deposits. 

Accordingly, it appears as if the mid-Atlantic ridge and 

the ridge west of Lands End, England, have been in 

existence during the deposition of the sediments, which, 

according to Bramlette and Bradley (see pt. 1 of this

PRESENT

CONDITIONS

*

• • 

*

'"« . ' .

• • •• •

9 '

. .

0 .20 .40

REDUCTION NUMBER

FIGURE 28.—Relation of reduction number of sediments to temperature of surface water as indicated 

by the pelagic Foraminifera in the sediments. The grades of temperature that form the ordinates 

of the figure represent relative deviations from the temperature of the surface water at the present 

time, as indicated by the types of Foraminifera in the sediments. These grades are based on data 

given by Cushman and Henbest (see pt. 2 of this professional paper, figs. 11-21).

professional paper, pp. 10, 11), probably represents a 

considerable part of Quaternary time.

TEMPERATURE

Although depth of burial does not seem to affect the 

organic content of the sediments appreciably, the different temperature zones apparently do have a slight effect. 

The average reduction number of the five warm and

four cold zones encountered in the cores is given in table 

31. The average (mean) of the five warm zones is 0.28 

and of the five cold zones 0.25. As some of the temperature zones are not represented in the cores the means 

of the individual zones in cores 4, 5, 6, and 7, which 

penetrated all nine zones, were also determined. The 

average of the warm zones on this basis is 0.25 and of 

the cold zones 0.22. A compilation of the nitrogen content shows similar results.

This difference is hardly great enough to 

be distinctive, but it suggests a slight tendency for higher organic content under warm 

conditions. In order to test this possible 

relationship in another way, the reduction 

number was plotted against the temperature of the surface water as indicated by the 

pelagic Foraminifera found in the samples. 

The results of this compilation are shown 

in figure 28 and indicate that the organic 

content, as indicated by the reduction number, seems to increase as the temperature of 

the surface water increases. The scatter of 

data on the chart, however, is great and the 

relationship at best is slight.

The relationship perhaps is contrary to 

what some might expect, because decomposition of organic matter is likely to progress 

at a more rapid rate in relatively warm water 

than in relatively cold water. Consequently 

less organic matter might be deposited in 

warm zones than in cold zones. However, 

even though the actual amount of organic 

matter deposited in a given unit of time may 

be less in the warm zones, the amount of inorganic 

material laid down in the cold zones may be so 

much greater than that deposited in the warm zones 

that the proportion of organic matter deposited in 

the cold zones may be less than what accumulates 

in the warm zones. The cold zones discussed in 

this paper contain relatively large amounts of material that seem to be of glacial or ice-raft origin. 

Consequently, the supply of inorganic debris during the

TABLE 31.—Average reduction number of warm and cold zones

1st warm zone_ _...._.

1st cold zone__ .. .

2d warm zone.

2d cold zone_. . _

3d warm zone. _ .

3d cold zone _ .

4th warm zone.

4th cold zone ___

5th warm zone

Median warmMedian cold

Mean warm

Mean cold___

Core number

4

0 24 

24 

22 

16 

24 

17 

34 

40 

24 

24 

21 

26 

24

5

0 25 

22 

25 

16 

26 

17 

25 

26 

23 

25 

20 

25 

20

6

0 25 

32 

32

17 

28 

18 

34 

26 

22 

28 

22 

28 

23

7

0 19 

24 

21 

16 

23 

13 

18 

28 

17 

19 

20 

20 

21

8

0 17 

10 

11

11 

12 

11 

15 

07 

11 

12 

11 

12

9

0. 51 

.43

. 51 

.43 

. 51 

.43

10

0.45 

. 28 

. 37

. 41 

. 28 

.41 

.28

12

0. 37 

.43 

.30

. 34 

.43 

. 34 

.43

13

0. 11 

. 18 

. 17 

. 14 

. 13 

. 12 

. 14

. 14 

. 14 

. 14 

. 15

Mean

0 28 

27 

24 

16 

21 

15 

23 

27 

19 

27 

25 

28 

25

Median

0 25 

24 

24 

16 

24 

15 

17 

26 

22 

24 

21 

26 

23

Mean 

4-7

0 23 

26 

25 

16 

25 

16 

28 

30 

22 

24 

21 

25 

22
PART 8. ORGANIC MATTER CONTENT 145

deposition of the sediments in the cold zones should be 

much greater than during the formation of the warm 

zones, especially as the sediments are so far from land. 

The apparently slightly greater organic content of the 

warm zones may possibly be due to such a cause. The 

sediments of the cold zones, moreover, are coarser than 

those in the warm zones and therefore may contain 

less organic matter, owing to the prevalence of conditions that favored the deposition of relatively coarse 

sediments. In fact, the organic content of all the 

sediments considered in this report seems 

to be related to the texture. 100

TEXTURE

The relation of the organic content to 

the texture of the sediments is illustrated 

by figure 29. In this figure the reduction 

number has been plotted against the percentage of material in the sediment finer 

than 74 microns, which corresponds 

roughly to the silt and clay content. 

This method of representing the texture 

is crude, but in general the greater the 

percentage of silt and clay in a sediment 

the finer is the texture. The data as 

plotted in this way exhibit a very definite 

increase in organic content as the percentage of clay and silt increases. The general trend is indicated by the heavy line 

through the samples. The scatter of the 

points on each side of this line is considerable, but the relationship of organic 

matter to texture is obvious.

The relationship between the texture 

and organic content probably is not one

texture, 18 but the large percentage of calcium carbonate 

in these deep-sea deposits and the lack of adequate 

data on the texture complicate the application of such 

a factor to them. It seems more practicable to calculate the reduction number upon a carbonate- and sandfree basis. The estimate of the organic content as 

calculated in this way can conveniently be designated 

as the "comparative organic content," because it is a 

measure of the organic content compared with the 

percentage of fine-grained constituents in sediments

.20 .40

REDUCTION NUMBER

of Cause and effect. Instead they both FIGURE 29.—Relation of reduction number to texture of sediments. The texture is represented by the

. i , AT- i percentage of silt and clay in the sample. The data on the silt and clay content of the sediments are

Seem tO Vary With respect to Some third taken from Bramlette and Bradley (see pt. 1 of this professional paper, pi. 3).

factor, which presumably is the movement of water in which the sediments are deposited. 

If currents are relatively strong, little organic matter 

and few fine particles can accumulate, and if currents 

are weak, the content of organic matter and fine particles is apt to be high. In order to ascertain from the 

organic content what the relative supply of organic 

matter in the overlying water was at the tune the sediments were deposited, it is, therefore, necessary to have 

a means of comparing the organic content of sediments 

of the same texture; that is, to have some way of ascertaining whether the sediments of any given texture, 

such as silts or clays, contain more or less organic 

matter than other sediments of the same texture. In 

this way, the effect of the motion of the water on the 

deposition of the organic matter is largely counterbalanced.

In near-shore sediments, this organic content relative 

to the fineness of the sediments has been determined 

by dividing the reduction number by a factor for the

that are deposited under conditions similar to those for 

organic matter.

To illustrate the method of calculation on this basis, 

take a sample in which the reduction number is 0.3, 

the carbonate content is 50 percent, and the percentage of sand is 10 percent. The percentage of noncalcareous fine-grained constituents would therefore be 

100— (50+10), or 40 percent, and the reduction number 

divided by this fine fraction would be 0.3/0.4, or 0.75.

COMPARATIVE ORGANIC CONTENT

The comparative organic content of the sediments 

in the nine temperature zones, as calculated in this 

way, is given in table 32. The main features indicated 

by this table are the general uniformity in organic 

content throughout the areal extent of the individual 

zones, the general decrease downward from the surface 

to the second cold zone, and the greater content for

is Trask, P. D., and Hammar, H. E., Organic content of sediments: Am. Petroleum 

Inst., Drilling and Production Practice, 1934, p. 120, 1935.
146 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

the warm zones compared with the cold zones. The 

effect of the ridges is largely eliminated. Nevertheless, 

the comparative organic content of core 9, just east 

of the mid-Atlantic ridge, as determined in this way, 

is distinctly greater than that of core 8, on the crest 

of the ridge. This greater comparative organic content of core 9 perhaps might be due to a greater production of organic matter in the overlying water but 

is probably due to enrichment from material swept 

off the ridge to the west.

The uppermost samples in cores 7, 8, and 9, in the 

vicinity of the mid-Atlantic ridge, have a relatively 

large comparative organic content. Though this may 

be due to a greater production of organic matter, it 

might also represent improper compensation for the 

texture. Core 11, in the eastern part of the basin, 

likewise has a relatively high content, which, coupled 

with the richness of core 9, suggests that the rate of 

production of organic matter is greater east of the midAtlantic ridge than west of it, but core 10, between

cores 9 and 11, has a relatively low content. The 

coring device at this locality buried itself in the mud, 

and an unknown amount of the upper part of the core 

was lost. The sediments encountered, therefore, represent material some distance beneath the surface, and 

the lower content in the upper part of this core might 

possibly be due to a decrease in organic content while 

the sediments have been buried. On the other hand, 

according to Bramlette and Bradley (see pt. 1, pp. 

32-34), the upper and lower parts of core 10 are anomalous and consist of a mixture of basaltic debris and clay, 

perhaps derived from a submarine volcanic vent. 

Furthermore, the comparative organic content is too 

indefinite a measure of the supply of organic matter 

in the overlying water to be considered very seriously. 

All that can be inferred is that the data for the uppermost zone suggest that the supply of organic matter 

in the eastern part of the Atlantic Ocean might be 

greater than in the western part.

TABLE 32.—Comparative organic content of the sediments

Core number

1st warm zone . _

1st cold zone _ _

2d warm zone.. - •

2d cold zone. .

3d cold zone ._.___ . .

4th warm zone _

4th cold zone

Mean of warm zones. - 

Mean of cold zones. ..

3

0. 86

. 86

4

0 83

48

39

32

54

37

67

62

44

57 

45

5

0 63

47

46

33

43

33

44

33

93

58 

37

6

0 86

54

49

30

49

40

61

40

57

60 

41

7

1 10

59

39

36

38

27

44

46

65

59 

42

8

1. 13

. 33

.42

.42

.39

.47

.49

.20

.53 

.40

9

1. 35

. 79

1. 35 

.79

10

0. 65

. 64

. 51

. 58 

. 64

11

1. 30

1. 30

12

0. 71

. 65

.57

. 64 

.65

13

0 31

33

53

28

41

24

40

.41 

.28

Mean

0 89

52

47

32

45

33

51

46

56

57

41

Similarly, it is hard to explain the decrease in comparative organic content from the surface downward 

through the first four temperature zones. This decrease may represent a smaller supply of organic matter 

at the time the deeper sediments were deposited; it may 

represent a loss of organic matter while these sediments 

are buried; it may be only an apparent decrease resulting from the method of compensating for the texture; or 

it may reflect the influence of the calcium carbonate 

content. The sediments in the cold zones contain less 

carbonate than those in the warm zones; consequently, 

as the calcium carbonate is not considered in the method 

of calculation, the organic content might be proportionately greater in samples that have a large carbonate 

content. However, if calcium carbonate is the cause, 

it is difficult to understand why the organic content 

should be less in the second warm zone than in the overlying first cold zone. Moreover, as shown below, the 

organic content does not seem to have any general 

relationship to the carbonate content.

The same difficulties arise in trying to account for the 

greater comparative organic content of the warm zones 

compared with the cold zones. The mean of the four 

cold zones is 0.41 and of all five warm zones is 0.57. If 

the first warm zone is not considered, the mean of the 

other four warm zones is 0.50 This slight difference 

between the warm and cold zones, considering the method 

of calculation, probably is not large enough to be distinctive, but it does suggest that the organic content 

when compensated for the texture is greater in the 

warm zones than in the cold zones. As mentioned 

above, the organic content of the entire sediment tends 

to show the same relationship to the temperature zones. 

Perhaps the supply of organic matter actually is greater 

during the deposition of the warm-zone sediments.

The most noteworthy thing about the comparative 

organic content, however, is the uniformity throughout 

the individual zones. The consistency, except for the 

upper zone, seems too striking to be accidental. The 

rate of sedimentation differs in different areas, yet the
PART 8. ORGANIC MATTER CONTENT 147

comparative organic content is essentially the same. 

Therefore, in order for the quantity of organic matter per 

unit of silt and clay to be the same for sediments deposited at different rates, either the supply of organic 

matter must differ in different areas, or in places where 

deposition is slow the decomposition of organic matter 

must be somewhat greater.

RATE OF DEPOSITION OF ORGANIC MATTER

In order to ascertain the actual quantity of organic 

matter that was deposited in given units of time in 

different areas, the average quantity of organic matter in 

each zone in each core was multiplied by the number 

of cubic centimeters of sediment in each zone. The 

organic matter was calculated on the basis of the entire 

sediment, and the deepest zone penetrated in each core 

was neglected in the computations, as the thickness of 

that particular zone in each core is unknown. The 

results are presented in table 33. On the assumptions 

that the correlation of the zones is correct, that the 

averages indicate the proper organic content, and that 

the thickness of the zones represents the true thickness, 

the data represent relative measures of the quantity of 

organic matter that accumulated in each zone. However, as the length of time represented by the different 

zones is different, it is not possible to compare the 

rates of deposition of organic matter in one zone with 

that in other zones, unless the interval of time represented by each zone is known.

TABLE 33.—Relative quantity of organic matter per zone, indicating relative rate of its deposition

Total of first seven

Core number

3

240

4

13 

25 

16 

3

14 

4 

37 

18

112

5

15 

14 

39 

2

10 

2 

14

7

96

6

26

28 

22 

3 

18 

1 

36 

4

134

7

11 

12 

13 

3 

11 

2 

12 

3

64

8

5 

0.5 

1 

0.2? 

4 

0.4 

9 

5

20

9

180 

42

10

69 

33

88

12

52 

70 

64

13

5 

3 

16 

3 

11 

11 

20

69

The data presented in table 33 indicate definitely 

that the rate of deposition of organic matter is greatest 

at the foot of the east slope of the ridges, as indicated 

by the first warm zone in cores 3 and 9. On the other 

hand, the rate is low on the ridges, as illustrated by 

cores 8 and 13. The organic content of sediments in 

the basins just east of the ridges, therefore, seems to be 

enriched at the expense of organic matter derived from 

the vicinity of the ridges. The rate of deposition of 

organic matter in the basin is greater for several hundred 

miles east of the mid-Atlantic ridge than for a similar 

distance west of it. According to table 33, the average 

for the first warm zone for cores 9, 10, and 12, east of 

the ridge, is 100 units, compared with 16 units for cores 

4, 5, 6, and 7, west of the ridge. Even if the enrichment of organic matter in core 9 is discounted, the rate 

of accumulation is greater east of the ridge, as the 

average of cores 10 and 12 is 60, which is much greater 

than the average of cores 4 to 7, inclusive. Similarly, 

the rate of accumulation in the subsurface zones is 

greater east of the ridge than west of it.

This greater accumulation of organic matter east of 

the mid-Atlantic ridge could be caused by a greater 

supply of organic matter in the water, by a slower rate 

of decomposition, by a combination of these two factors, 

or by a smaller supply of inorganic detritus. The 

quantity of organic matter in the water is related to 

the supply of plankton. However, as adequate data 

on the plankton content of the water along this profile 

in the North Atlantic are not available, it is impossible 

to estimate the extent to which the rate of accumulation 

of organic matter in the sediments is affected by the 

supply of organic matter in the water. The rate of 

accumulation is so much greater east of the ridge than 

west of it that the greater content of organic matter 

in the individual zones probably cannot all be due to 

a slower rate of decomposition of the organic matter 

after it reaches the sediments. The nitrogen-reduction 

ratio of the deposits, which is discussed below, tends 

to be lower east of the ridge and, therefore, suggests a 

higher state of reduction of the sediments. If the 

sediments are more reduced, the rate of decomposition 

probably would be slower,19 but whether or not it is 

sufficiently slow east of the ridge to account for the 

greater preservation of organic matter in the sediments 

is problematical. It seems probable that the greater 

rate to the east is partly due to a greater supply of 

plankton. Future oceattographic investigations will 

determine whether this is so or not.

NITROGEN-REDUCTION RATIO

The nitrogen-reduction ratio suggests that the sediments east of the mid-Atlantic ridge are more reduced 

than those west of it. As mentioned above, this ratio 

is a rough measure of the state of reduction or oxidation 

of the organic compounds. The results of the determination of the ratio are given in table 30 and in figure 

27. As illustrated by figure 27, the nitrogen-reduction 

ratio of the uppermost samples in the cores near the 

surface of deposits in general is lower east of the midAtlantic ridge than west of it. This lower ratio on the 

east side suggests a greater degree of reduction. The 

ratio, however, is low in core 6, west of the ridge, and 

is high in cores 12 and 13, near the east end of the 

profile on the continental slope; consequently the relationship is not entirely definite. As indicated by 

table 30, the ratio in the abyssal deeps in general also 

tends to be lower east of the ridge in the individual 

stratigraphic or temperature zones. The state of reduction of the sediments, therefore, may have been

» Trask, P. D., Inferences about the origin of oil as indicated by the composition 

of the organic constituents of sediments: U. S Qeol. Survey Prof. Paper 186-H, pp 

148-149,1937.
148 GEOLOGY AND BIOLOGY OF NQETH ATLANTIC DEEP-SEA COEES

greater east of the ridge during and since the later part 

of the Pleistocene.

This apparently greater state of reduction of the 

sediments east of the ridge could be caused by a lower 

degree of saturation of the deep water with oxygen. 

Data on the oxygen content of the water along this 

profile across the North Atlantic, however, are not 

available, but by analogy with determinations from 

other areas in the North Atlantic it seems probable 

that the oxygen content of the deep water east of the 

ridge is lower than that west of the ridge along this 

profile.20

The nitrogen-reduction ratio indicates few other 

relationships. It seems to be slightly larger in the 

uppermost sample in the individual cores than in the 

samples just below, which suggests an increase in

favorable environment for the decomposition of the 

nitrogen compounds, but if so, then one would expect 

a similar decomposition at the site of core 13. The 

relations of the nitrogen-reduction ratio in cores 8 and 

13 at best seem anomalous.

FORAMINIFERA

In order to ascertain whether or not the organic content 

might be related to the quantity of Foraminifera in the 

sediments, the reduction number of each sample was plotted against the percentage of Foraminif era in the samples. 

The results are indicated in figure 30. This figure indicates that the sediments having the greatest organic 

content contain the fewest Foraminifera. However, 

for any given percentage of Foraminifera the organic 

content varies widely. In all probability therefore, 

the organic content is not derived mainly 

from the Foraminifera. The inverse relationship to the Foraminifera presumably 

is caused largely by the relatively great 

bulk per unit of weight of the Foraminifera 

shells in the sediments. If sediments are 

composed largely of remains of Foraminifera, they contain relatively few fine ingredients, with which the organic matter 

generally is associated, but if they contain 

a small percentage of Foraminifera the proportion of fine ingredients is .high, with 

the result that the organic content likewise 

should be comparatively high. However, 

even when the organic matter is compensated for the effect of Foraminifera, a uniform organic content is not obtained. For 

example, the average (median) reduction

FIGURE 30.—Relation of reduction number to percentage of Foraminifera in sediments. Percentage of number of Samples Containing from 10 to

15 percent Foraminifera is 0.38. If none 

of the organic matter is assumed to be in 

the foraminiferal shells, then this 0.38 unit occurs in the 

nonforaminiferal constituents, or in 88 percent of the 

sediment. That is, these nonforaminiferal substances 

have a reduction number of 0.38/0.88 or 0.43 unit. 

Similarly, the average (median) reduction number of 

the nonforaminiferal constituents in the sediments that 

contain between 40 and 45 percent Foraminifera is 

0.16/0.58, or 0.28 unit. Thus, even after the effect of 

the Foraminif era shells has been discounted, the organic 

content of the sediments is greater for sediments that 

contain few Foraminifera than it is for those that contain many, provided, of course, the two examples that 

were chosen indicate the general trend. This line of 

reasoning, too, suggests even more strongly than was 

indicated above that the organic content of the sediments is not related to the percentage of Foraminifera 

hi the sediments, and hence presumably is not derived 

to any considerable extent from Foraminifera. However, Foraminifera tend to be plentiful in samples that 

contain the most sand. Consequently, the low organic

cc

llj 

u.

2 RO

CC

o

u.

fe

III

^ 9C

Z

UJ

0

cc

Q.

•

•

'. • '.

* •* •

9

.

9

y

. •*

." B .

. B •

* s • • * ' •

• • * • •

*

0

" . "" •" *" •

0 .20 , .40

REDUCTION NUMBER

Foraminifera is based on data given by Bramlette and Bradley (see pt. 1 of this professional paper, 

pi. 3).

degree of reduction a short distance beneath the surface 

of the deposits. The ratio does not seem to have any 

relationship to the warm and cold zones.

The sediments in core 13, on the ridge near the east 

end of the profile, have a relatively high ratio, and 

according to Bramlette and Bradley (see pt. 1, p. 15), 

the sediments are stained with iron oxide, which suggests oxidizing conditions. The sediments on the midAtlantic ridge likewise are stained with iron oxide, but 

the nitrogen-reduction ratio is low. The rusty color 

of the sediments seems a more reliable measure of the 

state of oxidation than the nitrogen-reduction ratio. 

Consequently, the low ratio of the sediments on the 

mid-Atlantic ridge is probably due to some cause other 

than the state of oxidation of the sediment, such as a 

relatively low percentage of nitrogen in the organic 

matter. The position of the sediments on a comparatively exposed place on the top of this ridge might be a

20 Wattenberg, H., Die Durchluftung des Atlantischen Ozeans: Internat. Council 

Exploration of the Sea Jour., vol. 4, No. 1, pp. 68-69,1929.
PART 8. ORGANIC MATTER CONTENT 149

content of those samples that are richest in Foraminif era 

perhaps may be due more to the physical conditions of 

sedimentation than to whether or not the organic matter 

is derived to a significant extent from Foraminif era.

The nitrogen content exhibits the same inverse relationship to the percentage of Foraminifera as does the 

reduction number. The nitrogen-reduction ratio, however, when similarly plotted, shows no relationship.

CALCIUM CARBONATE

The calcium carbonate content of the sediments does

not seem to be related to the organic content or to the 

nitrogen-reduction ratio. The reduction number, when 

plotted against the calcium carbonate content of these 

sediments, gives a random distribution in which no 

definite trends are apparent. The nitrogen content 

and nitrogen-reduction ratio, when similarly plotted 

against the calcium carbonate, give equally random 

distributions. The inference follows that the organic 

content of the sediments is not related to the carbonate 

content.

INDEX

Page 

Acknowledgments for aid—--_ — -___-— — — ———— — — — — — — —_ n, xiv

Apeof sediments....— — — —— —— — — — ———— — _ — _ —_..__.______.. vm

Analyses, chemical.- — ----__-—--___-______--_________-_ — _ — — — — ——— x

mech anical - — — — — — — — — - — — — — — — — — — — — _ — — — ___—_ — _____ vra

Archeology, significance of core study for__ — — — . — — — — — ___.__.._____ xm-xrv

Ash, volcanic, composition and distribution.. — — — — — — — — —— — — — __. vn

Barium, in sediments_— — — — — —— -._ — — _ — — ____ — . — _ — _ — _ vm

Basaltic glass, occurrence and character of.................................... vra

Boron, in sediments— — — — — — — — — — ———_ ——.._ — ..................... vra

Bottorn currents, evidence of.___ — — — — __.—_____._ —.___ ———__ —__. vn, 145

Bradley, W. H., introduction by.-.-.— —— — — —— — — ——— — —__ xm-xv

Carbonate, insediments————— — — — —— ._ ——— — — — _____ —_ vra, 149

Carnegie Institution of Washington, work on deep-sea cores by. — ___ vn, xi, xrv 

Climate, relation of sediments to.._— — - — — — _ — — — __ — _..... vn, vra, x, xra

Cold zones, organic content of__..........._........_...______.... 144

Core samples, analyses of—........... — .........— — __._____......._. 139-140

description of.— — — — .. — _______________ — . — . — .—................._ 138-139

methods used in obtaining_. — - — --.. — .. — ......— _ — — _ — — ._.— xrv-xv

Core stations, location of.- — — ___ —..... — ....... — ..... — . — . — — —....... xrv, 138

Correlation of zones represented in the cores...................... — . — ....... vn

Crinoids, in sediments.-. —... — ...... —....:. — —.______.____...........__ ix

Currents, bottom, evidence of. _ — _ — — — — ______ — ____ —.................... vn

Diatomaceae.——— — — — . —— _-, — — — — — ——— — — — ___ — — — — ____ vra-ix

Diatoms, distribution of, in sediments...— — — — — —— _ — ___._ —— — .__-. — _ vn-ix

Echinodermata...--..--..-.--. — — — . — .—.. — —............ — ..........___.. ix

Echinoids, association of-.--..-- — ----- — --............................... — .. ix

Elphidiella...--.. —— ----- — — — ...-.„...........-----. vra

Elphidium..............._...————-—.—..—..—...........—_........ vra

Farraday Hills, features of—....- — ... — . — ................. — — . — — ._.... xrv

Faunas, distribution of-.----..- — ---.-- — -..-...-.....-...................... ix

Fecal pellets, evidence of, in sediments. — — __..._._. — ....„...........„... vni

Foraminifera, age and correlation of..__ — _—._ — ._._______.—......._____... vra

distribution and environmental significance of...... —. — . — — — — ..... vn-vni

relation of, to organic content of sediments.- — — — — — — — — ——— — ——— 148-149

Foraminiferal marl, meaning of term_ __ _ _______ _ ____________ _......... vn-vm

Fossils, miscellaneous, distribution of—— — — . — — —— — — _--_ — . — - — _ ix

Gastropods, environment of..... —— . — . — — — — — —. — — .. — —— .- — .._ ix

Glacial marine deposits, age of— — .— — . — .. — — — — — — — —___. — —_ — — — .__ vn

features of-. ——— — — ______ — — . — — .. —— . — — . — — — — — . — .... vn

Glass shards, occurrence and character of... — — — — — — — — — — — — — _ — __ vm

Globigerina ooze, meaning of term— — — — — —— — — „_. —___ — — ———_ — __ vii-vra

Grain size of sediments......................——————...... —— .. — .... vm

Introduction to complete report— - — — — — — — — — — — _ — . — — — — xm-xv

Lithologic zones in cores, correlation of——......_-.- — — — _ — _ — ...... — — .. vn

Lithology and geologic interpretations.. — .---- — . — .--. —.............—... vn-vra

Location ot region studied.............. — — — .„ — — — — — _.._:.. vn, xi, xiv,143

Marl, foraminiferal, meaning of term.................. —.... — .. — . — .—... vn-vra

Mediterranean Sea, sediments in, significance of_._ ——— — — — — — — — . xui-xiv

miranda, Pourtalesia..---....------..-. — — .. — .. —............ — .. — . — _.... ix

Mollusca.. -._....____. — __ — - — — __ — -_ — — — . — — — . — _—. — — — ____ ix

Mud-feeding organisms, role of............ ........—-....................... vn

Nitrogen, determination of, in sediments-.. — — — — — ——— — — . — .__ 135

distribution of, in sediments.__._.. — .. ———..... —— ...„ — ___ 141-142

relation of, to organic content of sediments_ — — — ——— — — — — ___ 135-136

Nitrogen-reduction ratio, significance of-—.--.--.--- 137-138,139-140,147-148

Page 

Ophiuroids, association of_.____..——....... ————.———————.. ix

Organic content of sediments, methods of study of— — —..... —.... ——— 135-138

relation of calcium carbonate to__._.__._-......„-————...... 149

relation of configuration of sea floor to____.-..-----.-.--.-.. ——... 142,143

relation of depth of burial to...___- — ....... — .—.......—.——.. 142-144

relation of Foraminifera to_-------------------------- 148-149

relation of nitrogen to___..._____———— ———__.__——„ 135-136

relation of reduction number to..-------------------- 136-137,139-140

relation of temperature to___.___..___..._......._ 144-145,146-147

relation of texture to—_.._—————.. —..-- — . —..... — —....... 145

Organic matter, percentage of, in sediments. „ — .... —...——. — - - ix-x, 141-142

rateof deposition of—.--——-——--- —.... — . —.. ————.. — ....-.--— 147

Ostracoda.------------ —...-....--. ————— — — — — — — — — — ——— — -... ix

Outline of completereport— ——— — ——— —- — — -— ——......--- —— -... v

Palagonite, character and occurrence of------- ——— — — — ----------------- vra

Pelecypods, environment of___ — — ——.—— — — —.—— ——-- — —.— ix

Piggot, C. S., coring device designed by.....—._ — ——— ------- —.— vn, xrv-xv

foreword by__.--...-_-.--- ———— -— ———_.— —.....-..--...---.. xi-xn

Plankton, relation of, to organic content. — ——— — —— - — ------—————— x

Porosity of the sediments,..__.__...——. ——.. —. — - —.. ——..—— vni 

Pourtalesia miranda--- ——. — ........ — . —... —. —...———. —... —— - ix

Pteropod shells, distribution of-..-—--------- ——....--........ —. — . — ... vra,ix

Radium, concentration of, on ocean bottom-..—.--.--.------- — -.--------.--- xi

Eare elements, spectroscopic tests for.--. — — — — — — — — — — — — — vni

Eeduction number, determination of, insediments—- — — — — - —— — — — — — 136

distribution of, insediments--_------__- — --.. — — ----_ — . — -- ——. 141

relation of organic content of sediments to——----------------- 136-137,139-140

Eeduction of sediments, state of._..„._—...___. —..__----------- 147-148

Eegion sampled, extent of—-._----- ——— ..„. — — --. — — „ — -----.——.. vn, xi

Sampling and examination of cores, method of..--------------------------- xiv-xv

Sediments, age and correlationof- — — —— — — — --- —- — — — -- — -——- vni

grain size of...-----------------------------------------------------——.- vm

nitrogen in, distribution of______ _— -_____ — — — - — — -- — — — — ——— 141-142

organic constituents of, relation of nitrogen-reduction ratio to...———.. 137-138 

organic content of—. — -_-_ — - — — — - — — — — - — — — -- — — — ix-x, 141-142

methodsofstudyof——---------------------------------------- 135-138

relation of calcium carbonate to—-------------.--- — -- — --- — -- — -.- 149

relation of configuration of sea floor to—— — — — — - — — . — — — 142,143

relation of depth of burial to—— — — —— — —-- — — - — -- 142-144

relation of Foraminifera to---------------------------------------- 148-149

relation of nitrogen to.— — - — — ———— — — — — — — - 135-136

relation of reduction number to———— — — —— — — 136-138,139-142

relation of temperature to.—------------------------------ 144-145,146-147

relation of texture to..------------------------------------------------ 145

reduction of, state of------------------------------------------ —— --— 147-148

Selenium content of sediments — — — — — — — — — — — — ______-_-_ — ———- x

Spectroscopic tests of sediments—— — — — —— — — — —— — ———— vni

Summary of completereport..--------------------------------------- —— --.- vra-x

Temperature, relation of organic content of sediments to. — — - — — 144-145,146-147 

relation of type of sediment to.-----__------------------------------ vn,vra, x

Texture of sediments, relation of, to organic content— — — — — — — — -._- . x, 145

Uranium, in ocean sediments— — — — — — —- — — - — — — — — - — - xi

Volcanic ash, composition and distribution of— — — — — — — — — — — — — — — vn

Volcanic glass, occurrence and character of-. — — — — — — — ——— — — — vin

Warm zones, organic content of_ — —.- — — — - — - — - — — .- — — - — - 144

Zones represented in the cores, correlation of. — — — — — — — — — — — vn, 141

XVTI

The use of the subjoined mailing label to return

this report will be official business, and no

postage stamps will be required

UNITED STATES 

DEPARTMENT OF THE INTERIOR

GEOLOGICAL. SURVEY

PENALTY FOR PRIVATE USE TO AVOID 

PAYMENT OF POSTAGE. $30O

OFFICIAL BUSINESS

This label can be used only for returning 

official publications. The address must not 

be changed.

GEOLOGICAL SURVEY,