Organic Extracts 

From JOIDES Cores 

Off Northeastern Florida 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 581-C 

Prepared in cooperation with the Woods Hole 

Oceanographic Institution and the Joint 

Oceanographic Institutions' Deep Earth 

Sampling Program 

Organic Extracts 

From JOIDES Cores 

Off Northeastern Florida 

By E. E. BRAY and E. D. EVANS 

DRILLING ON THE CONTINENTAL MARGIN OFF FLORIDA 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 581-C 

Prepared in cooperation with the Woods Hole 

Oceanographic Institution and the Joint 

Oceanographic Institutions' Deep Earth 

Sampling Program 

A study of organic extracts from deep core 

samples from the continental shelf, the 

Florida-Hatteras Slope, and the Blake Plateau 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1969 
UNITED STATES DEPARTMENT OF THE INTERIOR 

WALTER J. HICKEL, Secretary 

GEOLOGICAL SURVEY 

William T. Pecora, Director 

For sale by the Superintendent of Documents, U.S. Government Printing Office 

... Washington, D.C. 20402 - Price 25 cents (paper cover) 
DRILLING ON THE 

CONTINENTAL MARGIN 

OFF FLORIDA 

Drilling on the continental margin off Jack- · 

sonville, Fla., in 1965 was the first project 

undertaken by the Joint Oceanographic Institutions' Deep Earth Sampling (JOIDES) Program, sponsored by the National Science Foundation. The U.S. Geological Survey cooperated 

with the Oceanographic Institutions in this 

undertaking and is publishing the results of 

these investigations in a series of professional 

papers. 

CONTENTS 

Page 

Abstract ----------------------------------------------------------------- C1 

Introduction ------------------------------------------------------------- 1 

Acknowledgments --------------------------------------------------------- 1 

Analyses of samples ------------------------------------------------------- 1 

Discussion --------------------------------------------------------------- 4 

Summary and conclusions ------------------------------------------------- 7 

References --------------------------------------------------------------- 7 

ILLUSTRATION 

Page 

FIGURE 1. Index map for JOIDES drill sites ------------------------------- C2 

TABLES 

Page 

TABLE 1. Identification ·of samples from JOIDES core holes ________________ C3 

2. Analytical data on organic extracts in samples from JOIDES core 

holes ------------------------------------------------------- 5 

3. Organic carbon, hydrocarbon, calcium carbonate, and EOM contents in samples from JOIDES core holes ______________________ 6 

v 

DRILLING ON THE CONTINENTAL MARGIN OFF FLORIDA 

ORGANIC EXTRACTS FROM 

JOIDES CORES OFF NORTHEASTERN FLORIDA 

By E. E. BRAY 1 and E. D. EVANS 1 

ABSTRACT 

Extracts of samples from cores of Tertiary strata at six 

sites off the Atlantic coast of northern Florida and across 

the Blake Plateau contained very meager quantities of 

hydrocarbons and other soluble organic material. 

Eleven samples forming a group with the least carbonate 

content from the shelf and continental slope were available 

for hydrocarbon analyses. In five of these samples from 

depths less than 25 meters below the ocean floor, the smaller 

molecular sizes, ranging from C12 to C20, averaged 22.1 percent of the saturated hydrocarbons (Ct:.;-Cao), whereas in 

the remaining six samples from greater depths, this fraction 

averaged 36.5 percent. 

INTRODUCTION 

A suite of samples from cores beginning at the 

ocean floor and extending to great depths is potentially valuable for observing chemical changes in 

organic material within sediments as a function of 

burial and time at crustal temperatures. An opportunity to acquire a suite of these samples was 

afforded early in 1965 by the Joint Oceanographic 

Institutions' Deep Earth Sampling (JOIDES) Program (1965). 

Six holes were drilled across the continental shelf 

and slope off the Atlantic coast of northern Florida 

and across the Blake Plateau at the positions indicated in figure 1 and table 1. 

Water depths at the drill sites ranged from 25 to 

1,036 meters, and penetrations into the bottom sediments ranged from 178 to 320 meters. Positions 

were determined by loran A. Two of three core holes 

drilled on the Blake Plateau penetrated into Paleocene strata, and thus sediments from most of the 

Cenozoic strata were sampled; the third core hole 

(J-3) penetrated strata of early Eocene age. On 

the continental shelf and slope, Cenozoic sediments 

were thicker, and the maximum penetration was 

into strata of middle Eocene age. 

The core samples, preserved by freezing at the 

collection site, were received late in 1965. Samples 

1 Mobil Research and Development Corp., P.O. Box 900, Dallas, Tex. 75221. 

were very small, averaging about 40 grams of dry 

sediment ; but in spite of the sample sizes, some 

useful information about the hydrocarbons and lipids 

was retrieved and is herein placed on record. 

ACKNOWLEDGMENTS 

We wish to thank R. H. Meade, John M. Hunt, and 

Vernon E. Swanson for their constructive suggestions and K. 0. Emery and his associates at the 

Woods Hole Oceanographic Institution, whose efforts 

and counsel were important factors in the initiation 

and execution of this study. We also thank the 

National Science Foundation for its grant to Lamont 

Geological Observatory, on behalf of JOIDES, to 

finance the drilling of the six offshore holes, and we 

are indebted to the Mobil Research and Development Corp. for providing the support for analyses 

. of the samples and preparation of the report. 

ANALYSES OF SAMPLES 

An objective in studying the distribution of\ 

organic molecular species in sediments from near the 

ocean floor downward to great depths is to follow 

the transformation of organic material to hydrocarbons. In this particular set of very small samples, 

the n-paraffins were so sparse as to be beyond the 

reach of our analytical techniques. However, other 

parameters we:re examined which were within reach 

analytically. These parameters included concentrations of extractable organic material (EOM), concentrations of heavy hydrocarbons ( c18+) in the 

sediment, percent of heavy hydrocarbons in the 

EOM, and the amount of saturated hydrocarbons in 

the C12-C:!o molecular size range relative to those 

in the total C12-Cao fraction. The analytical results 

for concentrations of he~vy hydrocarbons (C18+) 

in the sediment are approximately comparable to 

data in the literature (Baker, 1962; Gehman, 1962; 

Hunt, 1961; and Philippi, 1957). · 

C1 
C2 DRILLING ON THE CONTINENTAL MARGIN OFF FLORIDA 

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FIGURE 1.-JOIDES drill sites, Atlantic Ocean. (Modified from Joint Oceanographic 

Institutions' Deep Earth Sampling Program, 1965.) 

The samples were air dried at 38°C, pulverized 

to pass a 14-mesh sieve, and extracted by ball milling 

in the presence of a solvent for 4 hours to yield 

reproducible values of EOM. One or two milliliters 

of mixed solvent (10 parts benzene, 1 part methanol) 

per gram of dried sediment was used in the extraction process. Distilled water was then added to aggregate the pulverized sediment so that it could be 

separated from the solvent. The solvent was decanted and the insoluble solid material removed by 

filtering. A measured portion of the extract was 

stabilized by forced evaporation of the solvent at 

40°C. The amount of EOM was determined by 

weighing and also by dissolving the residue in cs2 

for an infrared ( IR) absorption spectrogram, from 

which measurement of the C-H bond stretching 

fundamental (3.42 microns) provided an estimate of 

the amount of organic extract. A large discrepancy 

between the weighed amount of residue and the 

amount determined by IR absorption measurement 

provided a clue for the presence of elemental sulfur. 

In event of discrepancy, the residue was treated to 

remove sulfur. 

The stabilized extract residues were dissolved 

and chromatographed on activated silica gel by using 

in sequence, as eluting agents, n-heptane, carbon 

tetrachloride, benzene, and methanol. The n-heptane 

fraction {F-1) contained the heavy saturated hydrocarbons (Cls+) which were present. The carbon 

tetrachloride fraction (F-2) and the benzene fraction {F-3) were predominantly heavy aromatic 

hydrocarbons, though some oxygen-bearing impurities were present. The methanol fraction {F-4) was 

composed of asphaltic (nonhydrocarbon) compounds. The eluting solvents were removed by forced 

evaporation at 40°C, and the amount of residue in 

each of the fractions was determined by weighing. 

The noneluted fraction remaining on the silica gel 
ORGANIC EXTRACTS FROM JOIDES CORES OFF NORTHEASTERN FLORIDA C3 

was determined by weight loss and designated as 

F -5. IR spectra were obtained for each of the chromatographic fractions dissolved in cs2 in order to 

characterize the material and observe the purity of 

the fractions. The solvents were carefully distilled 

to contain less than 0.2 microgram per milliliter of 

impurities that would be recovered with the sample 

and eluates. The silica gel was 100-200 mesh, grade 

923, Davison Co. silica gel which was activated prior 

to use, at 425°C for 6 hours. The chromatographic 

columns (10 mm ID by 360 mm long) each contained 

9 grams of the freshly activated silica gel. Column 

charges were adjusted to contain not more than 20 

milligrams of asphaltic materials so as not to exceed 

the retention capacity of the silica gel. 

The loss of saturated hydrocarbons in the C12-C2o 

molecular size range was avoided by use of a second 

method applied to a measured portion of the original 

extract. This portion of extract was concentrated 

to 10 milliliters to which 10 milliliters of n-heptane 

was added. The solution of extract and n-heptane 

was then concentrated to approximately 5 milliliters. 

During these concentration steps, the original benzene solvent had been largely removed, leaving the 

sample dissolved in the less volatile solvent, n-heptane. The saturated hydrocarbons were then isolated 

by adsorption chromatography. The separation was 

made using a 9-gram column of activated silica gel 

and eluting the saturated-hydrocarbon content of 

the sample with n-heptane. The effluent was then 

concentrated for gas chromatographic characterization. 

Gas chromatographic analyses were made on a 

10-foot column, one-eighth inch outside diameter, 

containing 4 percent silicone gum rubber (SE-30) 

on 60-80 mesh chromosorb W. Linear programming 

from 75° to 300°C was used with hydrogen flame 

detection. Although the samples were too small to 

allow separation and measurement of n-paraffin 

distributions, molecular size distributions ranging 

from C12 to C30 in the total saturated hydrocarbons 

were estimated from the chromatograms. From summations of peak areas in the gas chromatographic 

data, the relative amounts of hydrocarbons were 

estimated in the C12 to C2o (low-boiling fraction) 

and C20 to C30 molecular size ranges. These analytical 

techniques did not quantitatively assay for hydrocarbons lighter than C12· Column "bleeding" interfered with determining molecular sizes larger than 

C3o· 

The samples analyzed are indentified in table 1 ; 

core-hole number, location, depth, geologic age, and 

lithologic description are given. 

TABLE !.-Identification of samples from JOIDES core holes 

[Data from Schlee and Gerard, 1965] 

0 

Core 

depth 

(meters) Geologic age Sample description 

Core hole J-1 (lat 30°33' N., long 81 °00' W.)-water depth, 25 meters 

Post-Miocene____________ Sand, fine- to medium-grained, well-sorted, shelly, unconsolidated; quartz, clear to cloudy; 

pelecypod shells abundant; dark minerals scarce. 

15.2 ____ do__________________ Sand, fine- to medium-grained, silty, quartz, calcareous, massive, unconsolidated; HzS 

odor; foraminifers abundant. 

22.8 Late Miocene____________ Silt, coarse-grained, sandy, calcareous, quartz, phosphatic, compacted; HzS odor. 

30.5 ____ do __________________ Silt, quartz, micaceous, slightly calcareous, phosphatic, massive, plastic to compacted; 

strong HzS odor. 

62.2 Early Miocene___________ Clay, silty, phosphatic, massive- to thin-bedded, compacted to plastic; moderate HzS odor. 

92.9 ____ do__________________ Clay, silty, phosphatic, plastic. 

Core hole J-2 (lat 30°21' N., long 80°20' W.)-water depth, 42-46 meters 

0 Post-Miocene____________ Sand, coarse-grained, mode~ately sorted, quartz, shelly, unconsolidated; subangular to 

subrounded. 

101.2 Early Miocene___________ Clay, silty, massive to faintly laminated, plastic to partly compacted; foraminifers scarce 

to abundant. 

150.6-153 . 6 Late Eocene_____________ Ooze, fine-grained, 30 percent carbonate, biogenic, calcilutaceous, sandy to clayey, massive, 

unconsolidated to compacted; foraminifers abundant; pellets abundant; glauconite 

common. 

183.5 ____ do __________________ Limestone, packstone to wackestone; silty matrix, glauconitic, massive, firm to compacted, 

oily odor, scattered shell and foraminifer fragments. 

213.9 ____ do__________________ Limestone, biogenic, wackestone, silty, massive, firm to compacted; foraminifers common. 

257.5 ____ do__________________ Limestone, biogenic, calcarenite, medium-grained, glauconitic, carbonaceous, massive, 

firm to hard; oily odor; carbonaceous black oily flake; algae; shells. 

275.8 ____ do _____________ ----- Limestone, biogenic, silty packs~ one, massive, firm to compacted; slight HzS odor, glauconitic 

lumps of very fine grained aggregates. 
C4 

Core 

depth 

(meters) 

DRILLING ON THE CONTINENTAL MARGIN OFF FLORIDA 

TABLE !.-Identification of samples from JOIDES core holes-Continued 

Geologic age Sample description 

Core hole J-3 (lat; 28°30' N., long 77°31' W.)-wat;er depth, 1,036 meters 

15.2 Late Miocene____________ Ooze, biogenic, calcareous, silty to sandy; foraminifers; faint bedding to massive, uncon0 

18.3-24.4 

30.8-36.6 

69.2-72.5 

82.0-85.3 

133. 5-136.5 

152.7-155.7 

168.2 

solidated. 

Core hole J-4 (lat 31°02' N., long 77°43' W.)-water depth, 890 meters 

Post-Miocene____________ Sand, biogenic, calcarenitic; foraminifers; massive, unconsolidated. 

Early Miocene____ _ _ _ _ _ _ _ Sand, biogenic, calcarenitic. 

____ do __________________ Sand, silty, foraminifers. 

Oligocene___________ _ _ _ _ _ Sand, unconsolidated. 

Early Eocene____________ Ooze, greater than 30 percent carbonate, silty, massive, unconsolidated. 

Paleocene_______________ Interbedded clay and siliceous limestone. 

____ do__________________ Limestone, siliceous wackestone, hard; scattered foraminifers; clay, calcareous, slightly 

silty. 

____ do__________________ Clay, slightly silty, calcareous, massive, compacted, hard; grades downward to impure 

limestone. 

Core hole J-5 (lat 30°23' N., long 80°08' W.)-water depth, 190 meters 

0 Post-Miocene____________ Silt, sandy to clayey, slightly calcareous, unconsolidated; broken shell fragments; foraminifers. 

10.7 ____ do __________________ Sand, biogenic, calcarenitic; very coarse grained to fine gravel, moderately sorted, phosphatic, unconsolidated; broken shell fragments, foraminifers, pteropods; silt matrix, 

pellet-phosphate. 

19.8 ____ do __________________ Sand, silty, biogenic, calcarenitic; strong HzS odor; 60 percent foraminifers; quartz scarce. 

30.5 ____ do __________________ Silt, biogenic, calcilutaceous, poorly sorted; massive with scattered mottles; foraminifers 

abundant; shell fragments common; quartz, very fine grained. 

61.3 ---_do__________________ Sand and silt, calcarenitic, silty, porous, plastic to firm; foraminifers abundant. 

124.0 Oligocene________________ Clay and limestone, interbedded silty calcilutite; wackestone and silty plastic massive clay. 

198.1-200.5 ____ do__________________ Ooze and limestone, interbedded; ooze, silty, calcareous; massive to faintly bedded, plastic 

to partly compacted; and limestone, silty calcilutite, packstone to wackestone, massive. 

Core hole J-6 (lat 30°05' N., long 79°15' W.)-water depth, 805 meters 

7. 6 Oligocene________________ Ooze, silty, calcilutaceous, massive, unconsolidated to partly compacted; scattered volcanic shards. 

15.2 ____ do__________________ Ooze, silty, calcilutaceous, massive, unconsolidated to partly compacted. 

22.8 ____ do__________________ Ooze, silty, calcilutaceous, impure, massive, unconsolidated to partly compacted. 

30.5 ____ do__________________ Ooze, calcilutaceous, silty; massive to faint bedding, unconsolidated to partly compacted. 

60.9 Late Eocene_____________ Ooze, calcilutaceous, biogenic, clayey to silty, massive bedded to faint laminations, unconsolidated to compacted; calcareous lumps. 

91. 5 Middle Eocene___________ Ooze, silty, calcareous; foraminifers; massive, unconsolidated. 

The small quantities of EOM obtained from many 

of the individual samples made it necessary to combine two or more samples to form a larger sample 

for analysis. Selection of samples for the composites 

was restricted to single core sites and guided by 

depth sequence and lithologic similarity. Compositing resulted in 30 samples which were analyzed 

by the above procedures. Seven of these 30 samples 

were omitted from consideration because they w~re 

suspected of being contaminated during drilling by 

lubricating grease such as pipe-joint lubricant. Evidence for contamination consisted of excessive percentages (in excess of 30 percent) of heavy saturated hydrocarbons (C:!o+) in the extract without 

parallel increases of hydrocarbons in the lower ( CI2-

C2o) molecular size range. Analytical data for the 

remaining 23 samples are given in table 2; composite 

samples are indicated by braces. 

DISCUSSION 

It may be noted in table 2 that heavy hydrocarbon 

(Cis+) concentrations range from 4.0 to 37.5 ppm 

(parts per million) with a median of 11 ppm, which 

is in contrast to median values of 100 ppm for sediments in general (Gehman, 1962). 

If the sediments represented are judged by the 

criteria of Philippi (1957) and Hunt and Meinert 

(1958), the small quantities of hydrocarbons in these 

sediments indicate poor prospects for source rock 

of petroleum. Samples at 183.5 and 257.5 meters 

from core hole J-2 were reported to have an oily 

odor (table 1). The hydrocarbon content of the composite sample containing these samples was 4.0 

ppm, indicating little or no oil staining. 

Heavy hydrocarbon (Cis+) content, as percent 

of total organic carbon within ancient sediments, 
ORGANIC EXTRACTS FROM JOIDES CORES OFF NORTHEASTERN FLORIDA C5 

TABLE 2.-Analytical data on organic extracts in samples from JOIDES core holes 

[Analysts: E. D. Evans and G. M. Williams. F-1 =n-heptane fractions; F-2 =carbon tetrachloride fractions; F-3 = benzene fraction; 

F-4 =methanol fraction; F-5 =noneluted fraction. See page C2-C3 for the type of organic extract contained in each fraction. 

EOM =extractable organic material] 

Heavy Percent Percent 

hydro- c18+ C1z-C2o 

carbons Silica gel chromatographic fractions hydro- in 

Core (Cts+) in (percent organic extract) carbons saturated 

depth EOM sediment in hydro-

(meters) (ppm) (ppm) F-1 F-2 F-3 F-(4+5) EOM carbons 

Core hole J-1 

0 64.0 6.3 3.3 3.3 3.3 90.1 9.9 13.6 

15.2 58.0 5.6 3.2 3.2 3.2 90.4 9.6 19.6 

22.8 253.0 15.2 2.0 2.0 2.0 94.0 6.0 38.8 

30.5 332.0 14.9 .8 .8 2.9 95.5 4.5 48.2 

62.2 296.0 25.8 2.9 2.9 2.9 91.3 8.7 44.5 

92.9 293.0 37.5 6.4 2.1 4.3 87.2 12.8 28.3 

Core hole J-2 

0 10.0 

101.2 300.0 26.1 2.9 2.9 2.9 91.3 8.7 42.6 

150.6-153.6 183.0 10.8 2.0 1.9 2.0 94.1 5.9 36.0 

183.5, 213.9, 257.5, 275.8 23.0 4.0 8.7 4.3 4.3 82.7 17.3 32.3 

Core hole J-3 

15.2 14.0 

Core hole J-4. 

0 26.0 

18.3-24.4 20.0 

30.8-36.6 31.0 

69.2-72.5 28.0 

82.0-85. 3, 133. 5-136. 5, 

152.7-155.7, 168.2 47.2 10.5 14.8 3.7 3.7 77.8 22.2 34.5 

Core hole J-5 

0 280.0 11.7 1.4 0.7 2.1 95.8 4.2 20.7 

10.7, 19.8, 30.5 62.0 9.1 11.8 2.9 2.9 82.4 17.6 17.7 

61.3 126.0 11.6 5.3 1.3 2.6 90.8 9.2 25.7 

124.0 255.0 22.9 4.6 1.5 3.0 91.0 9.0 29.9 

198.1-200.5 142.0 6.5 1.3 1.3 1.3 96.1 3.9 39.4 

Core hole J-6 

7.6, 15.2, 22.8, 30.5 49.5 11.1 16.1 

60.9, 91.5 22.5 7.5 16.7 

is generally much higher in carbonates than in shales 

and clays (Hunt, 1961; Gehman, 1962). This relation 

suggests that clay and carbonate provinces should 

be separated when considering hydrocarbon and 

organic-matter content of sediments. 

Carbonate and total organic carbon data were 

obtained by Hulsemann (1968) on splits (fractions) 

of the samples described in table 1. HUlsemann's 

carbonate data expressed as percent CaC03 (table 3) 

indicate two general groupings of the samples. 

The samples containing more than 77 percent 

carbonate minerals form a group in contrast to those 

3.2 3.2 77.5 22.5 22.7 

8.3 8.3 66.7 33.3 18.5 

containing less than 70 percent carbonate. Samples 

from the Blake Plateau (J-3, J-4, J-6, fig. 1 and 

table 3) were predominantly in the high-carbonate 

group, whereas samples from sites J-1 and J-5 were 

predominantly in the low-carbonate group. 

It may be noted from table 3 that samples from 

greater depths beneath the shelf and slope belong 

to the high-carbonate group. 

The average heavy hydrocarbon ( C1s+) content, 

as percent of total organic carbon, for the highcarbonate samples was greater than that for the 

low-carbonate samples as anticipated (table 3). 
C6 DRILLING ON THE CONTINENTAL MARGIN OFF FLORIDA 

TABLE 3.-0rganic carbon, hydrocarbon, calcium carbonate, 

and EOM contents in samples from JOIDES core holes 

[Organic carbon and calcium carbonate contents from Hulsemann, 1968, table 1] 

Organic 

carbon 

Core (percent 

depth dry 

(meters) weight) 

0 0.11 

15.2 .71 

22.8 1.03 

30.5 .90 

62.2 1.04 

92.9 1.20 

101.2 1.10 

150.6-153.6 1.20 

183.5, 213.9, 

257.5, 275.8 1.30 

15.2 0.04 

0 0.11 

18.3-24.4 .11 

30.8-36.6 .21 

69.2-72.5 .09 

82.0-85.3, 

133. 5-136. 5, 

152.7-155.7, 168.2 I .31 

0 0.91 

10.7, 19.8, 30.5 1.38 

61.3 .93 

124.0 1.18 

198.1-200.5 1.13 

7.6, 15.2, 22.8, 30.5 10.09 

60. 9, 91. 5 I. 05 

1 Average organic carbon. 

2 Average carbonate. 

Heavy 

hydrocarbons 

(CtS+) 

as percent 

of organic 

carbon 

Core hole J-1 

0.57 

.08 

.15 

.17 

.25 

.31 

Core hole J-2 

0.24 

.09 

.13 

Core hole J-3 

Core hole J-4 

.34 

Cole hole J-5 

0.13 

.24 

.12 

.19 

.05 

Core hole J-6 

1.23 

1.50 

Calcium 

carbonate 

(CaCOs) 

in percent 

dry 

weight 

19.2 

68.2 

46.1 

2.9 

20.0 

59.7 

62.9 

83.6 

2 85.9 

87.6 

95.6 

86.8 

80.5 

88.7 

2 55.9 

65.1 

2 69.3 

60.8 

66.1 

78.1 

2 89.7 

2 83.8 

EOM 

as percent 

of organic 

carbon 

5.8 

.8 

2.5 

3.7 

2.8 

2.4 

2.7 

1.5 

.8 

3.5 

2.4 

1.8 

1.5 

3.1 

1.5 

3.1 

1.4 

1.4 

2.2 

1.3 

5.5 

4.5 

However, the quantity of hydrocarbons relative to 

the amount of organic carbon was very low when 

compared with ancient rocks in general. Heavy hydrocarbons (Cl~'+), as percent of total organic carbon, ranged from 0.05 to 1.50 with an average of 

0.6 for the high-carbonate samples and from 0.08 

to 0.34 with an average of 0.23 for the low-carbonate 

samples. These values compare with approximate 

averages of 11.7 percent for ancient carbonates in 

general and 4 percent for ancient shales in general 

(Hunt, 1961). These sparse amounts of hydrocarbons seem even more unusual when it is observed 

that the total amounts of organic carbon are nearly 

normal for both the sediments that have a high percentage of carbonate and those that have less carbonate. The average quantity of organic carbon for 

the high-carbonate samples is 0.33 percent of the dry 

sediment, which is not far from the average of 0.29 

percent reported for ancient carbonates in general 

(Hunt, 1961; Gehman, 1962). A similar analogy 

may be drawn for the low-carbonate province which 

contains an average quantity of 0.81 percent of organic carbon in the dry sediment as compared with 

a median value near 1.2 percent for shales in general 

(Hunt, 1961; Gehman, 1962). 

The geographic province and the carbonate content were used to group samples that were compared for differences in hydrocarbon content of sediments as a function of depth. Sufficient data were 

not available for either the Blake Plateau or the 

shelf and slope to compare shallow and deep samples 

in the high-carbonate group. However, there were 

11 samples in the low-carbonate group from the 

shelf and continental slope. Five of these samples 

were from depths less than 25 meters below the 

ocean floor, three being from the shelf and two from 

the continental slope. Six of the 11 samples were 

from depths greater than 25 meters below the ocean 

floor, four being from the shelf and two from the 

continental slope. The saturated hydrocarbons with 

molecular sizes ranging from C12 to C2o averaged 

22.1 percent of the total saturated hydrocarbons 

(C12-C:w) for the five samples above 25 meters 

depth, whereas in the remaining six samples from 

greater depths, this fraction averaged 36.5 percent. 

The samples at greater depth thus contain saturated 

hydrocarbons enriched in the smaller molecular sizes 

relative to those at shallower depths. 

Average values for the heavy hydrocarbons 

( C1s+), as percent of total organic carbon, are not 

significantly different for the two sample groups. 

This average for samples at depths less than 25 

meters below the ocean floor is 0.234 percent, whereas the average for the deeper samples is 0.228 percent. 

SUMMARY AND CONCLUSIONS 

Extracts of samples representing corings of Tertiary strata at six sites off the coast of northern 

Florida and across the Blake Plateau contained 

very meager quantities of hydrocarbons and other 

organic material soluble in organic solvents. Heavy 

hydrocarbon (C18+) values ranged from 4.0 to 37.5 

ppm with a median of 11 ppm. This median compares 

with a 100 ppm median for sediments in general. The 
ORGANIC EXTRACTS FROM JOIDES CORES OFF NORTHEASTERN FLORIDA C7 

small quantities of hydrocarbons do not suggest 

that these sediments are a source for petroleum. 

The C12-C2o molecular size range averages 22.1 

percent of the total saturated hydrocarbons at depths 

less than 25 meters and 36.5 percent at depths below 

25 meters beneath the sea floor in sparse sampling 

of the low-carbonate sediments on the shelf and 

slope. This relation indicates a likelihood of finding 

larger proportions of the lighter hydrocarbons in 

deeper samples. 

REFERENCES 

Baker, D. R., 1962, Organic geochemistry of Cherokee group 

in southeastern Kansas and northeastern Oklahoma: Am. 

Assoc. Petroleum Geologists Bull., v. 46, no. 9, p. 1621-

1642. 

Gehman, H. M., Jr., 1962, Organic matter in limestones: 

Geochim. et Cosmochim. Acta, v. 26, p. 885-897. 

Hiilsemann, Jobst, 1968, Calcium carbonate, organic carbon, 

and nitrogen in sediments from drill holes on the continental margin off Florida: U.S. Geol. Survey Prof. 

Paper 581-B, 10 p. 

Hunt, J. M., 1961, Distribution of hydrocarbons in sedimentary rocks, in Symposium on the chemical approaches 

to the recognition of petroleum source rocks: Geochim. 

et Cosmochim. Acta, v. 22, p. 37-49. 

Hunt, J. M., and Meinert, R. ~. 1958, Petroleum prospecting: 

U.S. Patent 2,854,396. 

Joint Oceanographic Institutions' Deep Earth Sampling 

Program, 1965, Ocean drilling on the continental margin: 

Science, v. 150, no. 3697, p. 709-716. 

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U. S. GOVERNMENT PRINTING OFFICE : 1969 0 - 334-790