GEOLOGICAL SURVEY CIRCULAR 750

Geological Studies on the

COST No. B-2 Well,

U.S. Mid-Atlantic

Outer Continental Shelf Area
Geological Studies on the

COST No. B-2 Well,

U.S. Mid-Atlantic

Outer Continental Shelf Area

P. A. Scholle, Editor

GEOLOGICAL SURVEY CIRCULAR 750

1977
United States Department of the Interior

CECIL D. ANDRUS, Secretary

Geological Survey

V. E. McKelvey, Director

Library of Congress catalog-card No. 77-72294

Free on application fo Branch of Distribution, U.S. Geological Survey 

1200 South Bads Street, Arlington, Va. 22202
CONTENTS

Page

Abstract ___________________ 1

Introduction ______________________ 1

Acknowledgments _________________ 3

Geologic setting, by R. E. Mattick ________ 4 

Data summary and petroleum potential, by

P. A. Scholle ___________________ 8

Lithologic descriptions, by E. C. Rhodehamel __ 15

Techniques ______________________ 15

Sand, shale, and carbonate content ______ 15

Sandstone porosities, by E. C. Rhodehamel __ 23

Sandstone petrography, by P. A. Scholle ___ 32

Composition _______________._____ 32

Diagenesis and cementation __________ 32

Conclusions ______________________ 34

Foraminiferal biostratigraphy, by C. W. Poag _ 35

Pleistocene _____________________ 35

Pliocene ______________________ 35

Miocene _______________________ 35

Eocene ________________________ 36

Paleocene _______________________ 36

Cretaceous __________________ 36

Paleoecology ____________________ 36

Nannofossil biostratigraphy, by P. C. Valentine_ 37

Pleistocene through Miocene ___________ 37

Oligocene ________________________ 37

Oligocene through Eocene ____________ 37

Nanofossil bios-tratigraphy Continued

Eocene _ _____

Eocene through Paleocene ________________

Cretaceous _ -

Palynomorph biostratigraphy, by R, A. Scott

and E. I. Robbins 

Results ___ ________ _ 

Paleoecology __ 

Conclusions _ ______

Geothermal gradients, by E. I. Robbins _ 

Organic geochemistry, by G. E. Claypool, C. M. 

Lubeck, J. P. Baysinger, and T. G. Ging____

Results and conclusions ________________

Geochemical measurement and interpretation 

a comparison __ _______

Color alteration of visible organic matter, by

E. I. Robbins ______ ____________

Data ________ ________ _ __

Conclusions _____ 

Geophysical studies, by D. J. Taylor, R. E.

Mattick, and K. C. Bayer ________________

Seismic stratigraphy _______________________

Lithologic information _ _________________

Amplitude anomalies _ _ _________

Conclusions __ _____________

References cited __ __

ILLUSTRATIONS

FIGURE 1.

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Page

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Locality map _____________________.______________ _ - - 

Generalized cross section of Atlantic Continental Shelf, Slope, and Rise ____________

Interpretive profile of part of USGS Line 2. ___._______________ 

Generalized lithology and depositional environments.______________ - 

Comparison of log and core porosity-permeability data _ - 

Comparison of various measures of thermal maturity as a function of depth _______________

Sand, shale, and carbonate content as a function of depth ______________

Density and sonic-log porosity as a function of depth 

Geothermal gradient for COST No. B-2 well ____.___ _ 

Temperature of maximum pyrolysis yield as a function of depth ______________ _ 

Calibration of temperature of maximum pyrolysis yield with respect to coal rank _____________

Gas-chromatographic analysis of saturated hydrocarbons: 3,040-3,070 feet ________ 

Gas-chromatographic analysis of saturated hydrocarbons: 3,580-3,610 feet __________________

Gas-chromatographic analysis of saturated hydrocarbons: 11,260-11,290 feet __________________

Gas-chromatographic analysis of saturated hydrocarbons: 12,160-12,190 feet ______

Gas-chromatographic analysis of saturated hydrocarbons: 15,900-16,030 feet _________________

Summary and comparison of analyses of richness of sediments in the COST No. B-2 well r 

Summary and comparison of analyses of type of organic matter in COST No. B-2 well samples 

Summary and comparison of analyses of maturity of organic matter in the COST No. B-2 well __ 

Maturation, abundance, and types of sapropel, abundance of organic matter, and weight percent

organic carbon as a function of depth ________.________________ ___ -

Seismic travel time (two-way) as a function of depth from the COST No. B-2 well sonic logs __ 

A computer model of possible lithologies and physical parameters determined from amplitude

anomaly or "bright spot" on seismic-reflection profile (fig. 3) between shotpoints 630 and 750 __

Page 

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in
TABLES

Page 

TABLE 1. Comparison of biostratigraphic analyses from the COST No. B-2 well _____________________ 10

2. Sedimentation rates of stratigraphic units of Berriasian to Pleistocene age in the COST No. B-2

well ________________________________________. _ ___ __ 11

3. Depositional environments determined from lithologic associations in COST No. B-2 well sediments _ ____ -_____ 16

4. Lithologic log of the COST No. B-2 well ______-_ __ _ 16

5. Sand, shale, and carbonate content in the COST No. B-2 well 21

6. Comparison of porosity (<t>) values determined from electric log and core measurements on

COST No. B-2 well samples . 25

7. Petrography of sandstone from the COST No. B-2 well ___________________________________ 33

8. Preliminary age determinations of COST No. B-2 samples on the basis of calcareous nannofossils 38

9. Circum-Atlantic offshore geothermal gradients _ - _______________ 44

10. Organic content of sediments from the COST No. B-2 well, obtained by combustion and thermal-analysis/pyrolysis __ ________ . 47

11. Summary of chloroform extraction yields, column chromatographic separation of CW hydrocarbon fractions, and estimate of carbon preference index (CPI) by gas chromatography from

12. COST No. B-2 well samples . 49

Ci-C7 hydrocarbon analyses of selected samples from the COST No. B-2 well ________________ 54

IV
Geological Studies on the COST No. B-2 Well, 

United States Mid-Atlantic Outer Continental Shelf area

P. A. Scholle, Editor

ABSTRACT

The COST No. B-2 well is the first deep stratigraphic 

test to be drilled on the United States Atlantic Outer 

Continental Shelf (AOCS) area. The well was drilled 

on the eastern flank of the Baltimore Canyon trough to 

a total depth of 16,043 feet; it penetrated a section 

composed almost entirely of sand and shale with subordinate amounts of limestone, coal, and lignite. Biostratigraphic studies have shown that the uppermost 

5,000 feet is of Tertiary and Quaternary age and was 

deposited in nonmarine to deep marine environments. 

The Upper Cretaceous section is about 3,000 feet thick 

and is of dominantly shallow marine origin. The basal 

8,000 feet of sediment has been tentatively determined 

to be entirely of Early Cretaceous age, the basal sediments being dated as Berriasian. This Lower Cretaceous 

section is primarily nonmarine to very shallow marine 

in origin.

Examination of cores, well cuttings, and electric logs 

shows that thick potential reservoir sands are found 

through much of the section. However, porosity and 

permeability decrease strikingly in the deeper parts of 

the Lower Cretaceous section as a result of compaction 

and cementation. Most of the sands are quite feldspathic, 

and progressive decomposition of feldspar stimulates 

authigenic clay and silica formation.

Studies of color alteration of visible organic matter, 

organic geochemistry, and vitrinite reflectance show 

that although many units have high organic-carbon contents, moderately low geothermal gradients may have 

retarded thermal maturation. This, in conjunction with 

the scarcity of marine-derived organic matter in the 

lower part of the section, suggests a relatively low potential for the generation of liquid hydrocarbons. However, the overall combination of source beds, reservoirs, 

seals, structures, and thermal gradients may be favorable for the generation and entrapment of natural gas. 

Furthermore, the presence of reservoir rocks, seals, and 

trapping structures may indicate a significant potential 

for entrapment of either natural gas or petroleum that 

was generated deeper in the basin and then migrated 

either laterally or vertically.

INTRODUCTION

Until recently, all information on the stratigrapMc framework of the United States Atlantic Outer Continental Shelf (AOCS) had 

come from onshore wells, offshore bottom 

sampling or shallow coring, geophysical surveys, and extrapolation from Canadian offshore wells. Between December 14, 1975, and 

March 28, 1976, however, the first deep stratigraphic test well was drilled on the U.S. AOCS 

by Ocean Production Company acting as operator for a group of 31 petroleum companies, the 

Continental Offshore Stratigraphic Test 

(COST) Group. This hole, des-gnated the 

COST NO. B-2 well, was drilled on the outer 

part of the AOCS about 91 miles east of Atlantic City, N.J., at lat 39°22'31.972" N. and 

long 72°44'03.871" W. (fig. 1). The well was 

drilled using the semisubmersible rig 

SEDCO-J. Water depth at the site is 298 feet, 

and drilling continued to a depth of 16,043 feet 

below the Kelly Bushing (or to 15,953 feet below sea level). The well is adjacent to the area 

offered for leasing on Aug. 17, 1976, as part 

of Lease Sale No. 40, shown on figure 1. The 

granting of federal leases within 50 miles of 

tbe drill site on Sept. 1, 197.6, has made possible the publication of detailed information 

a^out the geolog'cal findings from the COST 

No. B-2 well, because Lease Stipulation No. 4 

provides for public disclosure by the U.S. Geological Survey (USGS) of all geological information on the well 60 days after such leasing.

Considerable basic lithologic and stratigraphic data, most of it derived from industry 

reports, has been released (Smith and others, 

1976). This circular summarizes some of that 

data and adds information from other USGS 

studies. It is by no means an exhaustive or 

completed program, but because the COST No. 

B-2 well has such immediate interest for both
38° N

40°N 42°N 74° W

36°N NEW YORK

\

NORTH

CAROLINA

\VIRGINIA 

\

MARYLAND \/ PENNSYLVANIA

\

FE

WA

OU

USGS Nantucket well 

74° W 36° N

72°W 38"N 70°W 40°N 

FIGURE 1. Locality map showing site of COST No. B-2 well in relation to Baltimore Canyon trough, Lease Sale N
the petroleum industry and academic workers, 

we believe that publication of preliminary results is justified.

The publication is divided into separately 

authored sections on geological, geochemical, 

and geophysical topics. Environmental or operational details are not included, as these 

have been amply described by Smith and 

others (1976). Several diagrams are provided 

in the section, "Data Summary and Petroleum 

Potential," to compare the analytical results of 

USGS work with the industrial data summarized by Smith and others (1976).

All work reported on in this paper has been 

done using rotary drill cutting rather than conventional or sidewall cores. Electric logs and 

core descriptions were available, however, to 

aid in checking the accuracy of sample depth 

assignments. The cuttings, in conjunction with 

electric logs, thus provided a useful picture of 

the complete spectrum of lithologic variation 

within a given interval and were sometimes 

more useful than the spot samples provided by

sidewall coring. All depth references in this 

report for electric log, core, or cuttings data 

are based on depth below the Kelly Bushing 

(KB.) which is 90 feet above mean sea level 

and 388 feet above the sediment-water interface.

ACKNOWLEDGMENTS

Technical assistance in the preparation of 

this report is gratefully acknowledged from 

the following USGS personnel: Norman 0. 

Fredriksen for examining Tertiary pollen, 

Fred E. May for examining dinoflagellates, 

and Robert H. Tschudy for examining megaspores. Zoe Ann Hamlin, Peter Stinger, Lois 

Tomlinson, and Sandra Wortman helped 

greatly in sample preparation and analysis. 

Early versions of this paper were reviewed by 

Richard Q. Foote, Oswald W. Girard, Jr., Raymond Christopher, Harlan R. Bergquist, and 

Robert E. Miller. We are indebted to them for 

their many helpful suggestions.
Geologic Setting

By R. E. Mattick

The COST No. B-2 well is near the axis of 

the Baltimore Canyon trough, an elongate, 

northeast-trending structural depression in 

continental basement rocks filled with more 

than 40,000 feet of sediment (fig. 1). The 

trough, a possible offshore extension of the 

Salisbury embayment, extends from about 

Long Island, N.Y., southwestward to the vicinity of Cape Hatteras, N.C. A diagrammatic 

cross section of the Baltimore Canyon trough 

is shown in figure 2. This seaward-thickening 

sedimentary wedge is built over a deeply buried 

fault zone which may represent a transition 

between continental and oceanic basement 

rocks. A seismic profile (fig. 3) shows that 

Jurassic and Cretaceous sedimentary rocks, 

which are gently dipping throughout most of 

the Baltimore Canyon trough area, are warped 

upward by a large basement intrusion on the 

Continental Shelf off New Jersey.

On the basis of magnetic and gravity data, 

early authors proposed that a volcanic or basement ridge, which may have acted as a sediment dam during Jurassic and Early Cretaceous time, is buried about 15,000 feet beneath 

the outer shelf and slope (Drake and others, 

1959). Later, Mattick and others (1974) suggested that the main part of the Batlimore 

Canyon trough, the part underlying the midshelf area, is a broad graben to which is 

coupled a large horst, buried at a depth of 

about 25,000 feet beneath the shelf edge. 

Whether or not crystalline rocks or highvelocity sedimentary rocks are present deeper 

than about 20,000 feet at the shelf edge has 

not been determined from available seismic 

data. Schlee and others (1976) have speculated 

that the rocks are sedimentary and that the 

shelf edge is underlain by a deeply buried carbonate platform with reef deposits that formed

atop a block-faulted margin after separation 

of the African and North American plates.

By analogy with the Coastal Plain, the basement beneath the Baltimore Canyon trough 

area is inferred to consist of Paleozoic and 

Precambrian (?) metamorphic rocks similar to 

those exposed in the Applachian Piedmont 

province (Perry and others, 1975). Downfaulted grabens in the basement probably are 

present locally and may be filled with Triassic 

rocks consisting of nonmarine arkosic sandstones, shales, basaltic lava flows, and diabase 

intrusions. Seismic evidence indicates that as 

much as 45,000 feet of sediments unconformably overlies the Triassic and pre-Triassic 

basement rocks (Mattick and others, 1975).

The basal part of the sedimentary section 

may contain Paleozoic and marine Triassic 

sediments. Seismic velocities of sedimentary 

rocks deeper than about 25,000 feet are in excess of 20,000 feet/sec.; these high velocities 

may indicate a thick section of chiefly Jurassic 

carbonate rocks underlain by evaporites (Mattick and others, 1976). By analogy with well 

data from the Scotian Shelf (Mclver, 1972), 

we infer that these carbonate rocks are overlain by several thousand feet of Jurassic sands 

and shales.

According to Minard and others (1974), 

Lower Cretaceous sediments constitute a major 

deltaic sequence in the emerged Coastal Plain. 

The results from the COST No. B-2 well, which 

penetrated approximately 8,000 feet of Lower 

Cretaceous rocks that have a high percentage 

of massive sandstone, indicate that these deltaic 

sediments extend seaward across much of the 

Continental Shelf. However, on the basis of 

seismic-reflection velocities, Mattick and others 

(1975) believe that basal Lower Cretaceous 

rocks at the shelf edge are chiefly carbonate 

rocks.
WEST f

ATLANTIC CITY, N.J. 

SEA LEVEL

Baltimore Canyon Trough

COST No. B-2 WELL

ATLANTIC OCE

T.D.-16,043 FT (KB)

SEDIMENTARY ROCKS

OCEANIC BASEMENT CONTINENTAL

TRANSITIONAL 

BASEMENT

VERTICAL EXAGGE

DISTANCE FROM SHORELINE

200 

i

16,000-

50 

i_

100 

I

200 MILES

FIGURE 2. Generalized cross section of the U.S. Atlantic Continental Shelf, Slope, and Rise. Section line is an extens

large basement intrusion and location of COST No. B-2 well.
REFLECTION TIME (TWO-WAY), IN SECONDS

60

I

CO

o

CO

p

1ft

i

I

SQNOD3S Nl UVM-OMl) 3WI1 NOIlD31d3a
At the B-2 site, the Upper Cretaceous section is approximately 3,000 feet thick, and the 

Tertiary section is about 5,000 feet thick. On 

the basis of seismic correlation, these thicknesses appear to remain relatively constant over 

most of the AOCS area.

Some of the highest bonus bids of Lease Sale 

No. 40 involved lease blocks over a basement 

intrusion in the central Baltimore Canyon 

trough area (West, 1976). Figure 3 is a schematic diagram of a seismic-reflection record 

that crosses this feature. Jurassic (?) and 

Lower Cretaceous beds appear to have been 

arched several thousands of feet across an area 

approximately 15 miles wide. A seismic horizon 

slightly below the Lower Cretaceous-Upper 

Cretaceous boundary represents a marked unconformity at which at least 1,300 feet of sediment was removed by erosion.

The unconformity just below the Lower 

Cretaceous-Upper Cretaceous boundary probably dates the last major upward movement of 

the intrusive body. However, arching, thinning, 

and minor faulting of Upper Cretaceous beds, 

and slight thinning of lower Tertiary beds 

above the intrusive body could reflect later 

movement.

Other Cretaceous tectonic activity may be 

illustrated by growth faults along the shelfslope break (Mattick and others, 1974). Emery 

and others (1970) reported that diapiric salt 

structures may be present along the Continental Slope and Rise off Nova Scotia. Sheridan 

(1974) extended this province southward and 

reported the possibility of salt diapirism in the 

Baltimore Canyon trough area.
Data Summary and Petroleum Potential

By P. A. Scholle

The COST No. B-2 well penetrated 15,655 

feet of Mesozoic and Cenozoic section. Lithologic and paleoenvironmental studies, summarized in figure 4, indicate that the upper 2,000 

feet of section has very sandy shallow marine 

to nonmarine deposits. Below that, to a total 

drilling depth of about 6,000 feet, a deeper 

water, finer grained section is present. From 

that level to the base of the well, the section 

consists of alternating sandstones and shales 

of shallow marine to nonmarine origin. This 

deeper part of the section contains many coal 

and lignite seams.

Biostratigraphic work completed to date 

(and summarized in table 1) shows general 

agreement between the various workers on 

most stage and series boundaries. The Cretaceous-Tertiary boundary is placed between 

5,000 and 5,600 feet by different workers, and 

the Lower Cretaceous-Upper Cretaceous boundary is very close to the 8,200-foot level. Although the basal part of the section might well 

be Jurassic, the consensus now favors a Berriasian (Early Cretaceous) age for these sediments.

The rates of sedimentation of various stratigraphic units in the B-2 area were quite variable, as shown in table 2. For discussion purposes, the Miocene to Pleistocene rates have 

been taken as average; relative to these, the 

entire interval from Campanian to Oligocene 

had low rates of sedimentation. This corresponds generally with the time interval of 

deepest water sedimentation in this area. Albian to Santonian time was characterized by 

shallower water deposition and generally average sedimentation rates; Berriasian to Aptian 

time was marked by very shallow marine to 

nonmarine deposition and average to very high 

rates of sedimentation.

A major part of the Cretaceous section (that 

is, the section between 5,000 and 16,000 feet)

consists of relatively thick sandstone units, 

some of which have significant reservoir potential. The reservoir quality of this sandstone, 

however, deteriorates consistently as depth increases. The relationship between depth and 

petrophysical characteristics determined from 

electric logs as well as from cores is shown in 

figure 5. The porosity loss below 12,000 feet is 

largely related to compaction effects and to 

progressive breakdown of feldspar accompanied 

by growth of authigenic clay and silica cement. 

Generation of calcite cement is also important, 

especially in zones that contain marine fossils 

or limestone. As seen on figure 5, these porosity 

losses, especially, the formation of authigenic 

clay, have a drastic effect on permeability. 

Thus, in the section below 12,000 feet few sandstones have more than 1 millidarcy (md) permeability.

Geochemical studies of the COST No. B-2 

well have shown that the area not only has a 

relatively low geothermal gradient today but 

that apparently it has been that low or even 

lower throughout the Cretaceous to Holocene 

history. Data from color alteration of visible 

organic matter, pyrolytic-decomposition temperatures, carbon-preference index, and vitrinite reflectance are summarized in figure 6.

All methods indicate that the section down 

to at least 8,000 feet is thermally immature and 

is unlikely to have yielded hydrocarbons other 

than biogenically generated methane. Below 

8,000 feet there is some disagreement in interpretation between the various analytical 

techniques. The techniques based on observations of visible organic matter indicate moderate to full thermal maturity in the 8,000- to 

16,000-foot depth range. For example, vitrinitereflectance values of 0.45 to 0.50, found at about 

8,000 feet in the COST No. B-2 well, are generally taken as marking the earliest onset of 

possible liquid-hydrocarbon generation (Bar8
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TABLE 2. Sedimentation rates of stratigraphic units of Berriasian to Pleistocene age in the COST No. B-2 well

Unit

Pleistocene and Pliocene __________

Miocene __________________ , _

Oligocene ___ _ ______________

Eocene _____________________

Paleocene ______________________________

Maestrichtian and Campanian ____________

Santonian and Coniacian _________________

Turonian __ _ _________________________

Cenomanian ____________________________

Albian __________________________

Aptian ____________ ___________

Barremian, Hauterivian and Valanginian _ 

Berriasian _______________ ____

Total ____________________________

Sediment 

thickness 

(ft)

KOO

2

coc

/ICC

QQO

oc

736

1 °.91

553

520

770

1,100

2,000 

4,042

15,654

Duration 

(millions 

of 

years) 1

5

1R

15

14

11

10

6

7

16 

4

133

Percent 

of 

total sediment

17

5

<1

5

5

7

12 

25

Percent 

of 

total 

time 1

4

 to

11

10

10

6

4

6

6

5

12 

3

Relative 

sedimentation 

rate

Average

A T7OY*Q O^

Low

Low

High

Average

Average

High

Average 

Very high

Absolute sedimentation 

rate 

(ft/m.y.)

104

149

32

63

3

56

165

92

65

96

157

125 

1,011

iFrom Berggren (1972) and Van Hinte (1976).

tenstein and Teichmiiller, 1974; Hood and 

others, 1975; Vassyoevich and others, 1970). 

Likewise, vitrinite-reflectance values of 0.6 to 

0.7, and sapropel-maturation values of 2.5 to 

3.0 found below 12,000 feet in the COST No. 

B-2 well, mark the peak rate of liquid-hydrocarbon formation. Thus, on the basis of such 

data, the present temperature profile in the 

well, and provided that sediments containing 

suitable organic matter are present, significant 

liquid hydrocarbons should have been generated.

Geochemical analyses of disseminated organic matter yield a different picture, however. 

Studies of extractable organic matter presented 

by Claypool and others (this volume), Geochem Laboratories (1976), and Smith and 

others (1976) have indicated that none of the 

sediments penetrated in the COST No. B-2 

well are mature with respect to liquid-hydrocarbon generation. Indications are that minor 

amounts of liquid and significant amounts of 

gaseous hydrocarbons may have been generated, but large amounts of liquid-petroleum 

hydrocarbons have not yet been generated.

These differences in apparent maturity found 

by means of visual and geochemical techniques 

are not easily explained. Considerable disagreement still exists about the exact time-temperature relations needed for oil formation and the 

effect of type of organic matter and other factors upon rates of formation (for example, 

Tissot and others, 1974). Thus, the noted discrepancies may be due to incorrect extrapolation of maturity versus oil-generation values 

from other basins. Indeed, recent workers have 

tended to place the main phase of oil generation 

at greater and greater depths and temperatures 

(for example, Hood and Castano, 1974). On the 

basis of such work there is little discrepancy 

between visual and geochemical analyses; both 

would indicate only marginal maturity with 

respect to liquid-petroleum-hydrocarbon generation at the base of the COST No. B-2 well.

The type as well as the amount of organic 

matter present in the sediments plays a major 

role in the determination of the hydrocarbon 

potential of the section. In the COST No. B-2 

well, some of the highest organic carbon contents (as much as 12 percent) are present between 3,000 and 6,000 feet and 9,500 and 14,000 

feet. The lower of these two intervals has a 

very significant amount of coal, especially between 9,500 and 11,300 feet and 12,400 and 

14,000 feet. The dominance of terrestrial over 

marine-derived organic matter in this interval 

strongly reduces the probability of generation 

of economic amounts of liquid-petroleum hydrocarbons but allows a high potential for generation of wet or dry gas. Furthermore, significant potential exists for lateral or vertical 

migration of liquid or gaseous hydrocarbons 

from structurally or stratigraphically deeper 

parts of the section.

Some supporting evidence for the presence of 

natural-gas deposits may come from Hole No. 

6021-C of the USGS Atlantic Margin Coring 

Project (fig. 1), which was drilled at lat 

38°57.92' N., long 72°49.20' W. The upper

11
Density log porosity 

(percent)

Core porosity 

(percent)

25 50 75

Permeability 

(millidarcies)

s

FIGURE 5. Comparison of density log curve of porosity (from Rhodehamel, this volume) with measured core 

porosities and empirically determined permeabilities from Core Laboratories as given by Smith and others 

(1976).

1,000 feet of sediment was penetrated at this 

site and contained significant amounts of the 

light hydrocarbons (methane, ethane, and propane). Although R. E. Miller and D. M. 

Schultz (written commun., 1976) believe that

the methane is dominantly biogenic in origin, 

some leakage from deeper natural-gas sources 

may exist. Several samples of gas-bearing mud 

from this borehole have been analyzed for 

stable carbon-isotopic composition of the

12
Temperature of rrraximum pyrolytic

Degree of thermal alteration decomposi tfon (degrees Celsius) Carbon preference index 

SQSQPQP o m c» ._

Vitrinite reflectance

(Ro percent)

o c

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2.0 

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4.0

5.0

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8

FIGURE 6. Comparison of various measures of thermal maturity as a function of depth in COST No. B-2 well. 

Degree of thermal alteration is from Robbins (this volume); pyrolitic decomposition data are from Clay pool 

and others (this volume); carbon-preference index and vitrinite-reflectance data are from Geochem Laboratories and Superior Oil Co., respectively, as reported in Smith and others (1976).

methane. These preliminary results (813CPDB= 

-35 to -45 per mil) may indicate seepage from 

deeper parts of the section. However, because 

of the extremely small quantities of gas obtained and analyzed, the results should not be

interpreted as unequivocal support for a thermogenic origin of the methane (G. E. Claypool, 

written commun., 1976).

Further indication of possible gas deposits 

comes from bright-spot analysis of USGS Line

13
2 (discussed in the section on Geophysical 

studies). A major amplitude anomaly, a considerable distance landward of the COST No. 

B-2 well site, has been tentatively interpreted 

as a natural-gas deposit.

Essentially five major factors are involved in 

the origin and entrapment of hydrocarbons: 

(1) source rocks, (2) temperatures sufficient to 

generate gas or oil, (3) reservoir rocks, (4) 

seals, and (5) trapping structures. Indications 

from the B-2 well are that rocks of high organic-carbon content are present from 3,000 

to 6,000 feet and 9,000 to 14,000 feet and that 

some of these rocks are capable of generating 

considerable amounts of hydrocarbons. Temperatures may have been too low in much of 

this section to have generated liquid hydrocarbons, but they appear to have been sufficient for 

gas generation. Reservoir rocks are abundant 

throughout most of the COST No. B-2 well 

section, although the reservoir quality of most

of the sandstone units degrades rapidly at 

depths greater than 10,000 to 12,000 feet. Seals, 

in the form of shale, are present in much of 

the section. Finally, as shown in the section 

"geologic setting," large structures are available for hydrocarbon entrapment in areas adjacent to the COST No. B-2 well. These structures may also enhance vertical migration of 

hydrocarbons along fractures from deeper parts 

of the section.

Data from the COST No. B-2 well indicate 

a higher potential for natural gas than for 

liquid petroleum. Moving in the direction of a 

more marine section would give a higher potential for oil generation, lower feldspar content (and thus less cementation at depth), and 

more shale seals. Likewise, moving to possible 

areas of higher paleogeothermal gradients 

would improve the potential for either oil or 

gas generation.

14
Lithologic Descriptions

By E. C. Rhodehamel

The COST No. B-2 well penetrated sediments deposited in environments ranging from 

nonmarine to deep water (table 3) and ranging in age from Holocene to earliest Early 

Cretaceous; basement rock was not penetrated. 

Although significant amounts of carbonate 

sediments are present in the lower Tertiary 

and Upper Cretaceous intervals, sandstone and 

shale predominate. The detailed lithologic log 

(table 4) includes tentative stratigraphic intervals provided by other investigators (Smith 

and others, 1976).

TECHNIQUES

Well cuttings (samples) were collected at 30- 

foot intervals between 610 and 4,620 feet and 

at 10-foot intervals between 4,620 and 16,043 

feet. In this preliminary study, samples were 

analyzed at sampling intervals of 90 feet down 

to 4,620 feet, and intervals of 30 feet below 

that depth. Intervening samples were examined 

where initial sample volume was adequate. In 

addition to the well cuttings, four conventional 

cores were examined. These cores were taken 

at 5,030 to 5,090 feet with 1.5 feet of recovery; 

at 8,238 to 8,268 feet, with 28.4 feet of recovery; at 9,280 to 9,330 feet with complete 

recovery; and at 13,420 and 13,471 feet with 

34.5 feet of recovery. More than 800 sidewall 

cores were taken; these cores were not directly 

examined in this study, but the core descriptions (Core Laboratories, 1976) were checked 

against lithologic picks from cuttings and logs.

Because of variations in drilling rate, mud 

circulation time, mudcake failures, hole washouts, and other operational factors, the lithologic samples for specified intervals often do 

not adequately represent the actual material 

penetrated; contamination and mixing from 

above are also factors. Furthermore, the samples were washed so that the natural muds and 

fines were lost while the drilling mud was being

removed. Accordingly, it was necessary to rely 

heavily upon the various geophysical logs. The 

logs used most frequently were the spontaneous-potential (SP) and dual-induction logs 

(DIL), the formation-density compensated log 

(FDC), the simultaneous compensated neutron 

and formation-density logs (CNL-FDC), the 

natural gamma-ray log (GR), the borehole 

compensated sonic log (BHC), and the caliper 

log. These logs, along with the available washed 

well-cutting samples were the primary data 

sources for the assembly of the lithologic log 

presented below. The observations from 300 to 

610 feet were made entirely from the gammaray log.

Summary lithologic descriptions have been 

provided by Smith and others (1976). The 

lithologic log presented here is a bed-by-bed 

description (unit lithologic description) of significant sedimentary layers. The general lithology is presented with only enough detail to indicate the rock type and some general qualifiers. The described lithology when assessed in 

its overall sediment context appears to provide 

rough but reasonable inferences as to the gross 

environments of deposition, especially when 

these assessments are combined with analyses 

of sedimentary structures from core slabs. 

These depositional environments are tentatively listed in table 3, and the lithologic log 

is given in table 4.

Zones of high radioactivity are found at 

8,399, 8,655, 9,315, 9,585, 9,990, 12,223, 12,276, 

13,292, and 13,331 feet. These horizons often 

contain phosphatic pebbles and glauconite and 

may represent hiatus surfaces.

SAND, SHALE, AND CARBONATE CONTENT

Compilation of the lithologic log provides a 

means of evaluating depth-related variations in 

the relative percentages of common rock types 

such as sandstone, shale (including siltstone

15
TABLE 3. Depositional environments determined from lithologic associations in COST No. B-2 well sediments

[?, uncertain determination]

Depositional environment

Approximate 

depth 

(feet)

300- 940 ______________

940- 3,700 ______________

3,700- 3,955 ______________

3,955- 5,010 ______________

5,010- 5,298 ______________

5,298- 5,315 ______________

5,315- 5,700 ______________

5,700- 5,900 ______________

5,900- 6,850 ______________

6,850- 7,020 ______________

7,020- 7,500 ______________

7,500- 7,680 ______________

7,680- 8,220 ______________

8,220- 8,970 ______________

8,970- 9,420 ______________

9,420-10,050 ______________

10,050-16,043 ______________

NONMARINE

TransiTerrestrial tional, 

(fluvial, (lagoonal, 

glacial, estuarine, 

aeolian) tidal 

inlet)

______ X

______ __ X

______ __ X

______ __ X

______ X X

___ X X

Nearshore 

(beach, 

bar, 

tidal 

flat)

xxxxxx! x!!!xxxx

MARINE

Open marine

Inner

X 

X

;*;

X 

X

X

Neritic

Middle

"x 

"x

"x

X 

7

"x

X

"x

Outer

X 

~X

~X 

~X

Bathyal 

(shallow 

upper 

slope)

"x

TABLE 4. Lithologic log of the COST No. B-2 well

Depth 

(in feet) Unit lithologic description

300- 550 Sand and gravel (?) (clean?).

550- 590 Sand and gravel (?) clayey.

590- 820 Sand becoming more clayey with 

depth.

820- 830 Clay.

830- 945 Sand, clayey.

945- 1,090 Sand, clean. 

1,090- 1,100 Sand, clayey.

At 1,100 Approximate base of Holocene and

Pleistocene and approximate top of 

Pliocene and Miocene. 

1,100- 1,150 Sand, clean. 

1,150- 1,180 Clay, sandy.

At 1,172 Identifiable middle Miocene. 

1,180- 1,190 Clay and sand streaks. 

1,190- 1,223 Clay. 

1,223- 1,228 Sandstone layers. 

1,228- 1,298 Sand containing intercalated clay

layers.

1,298- 1,345 Clay containing sand layers. 

1,345- 1,375 Sand, silty. 

1,375- 1,400 Clay, sandy. 

1,400- 1,420 Sand, clayey. 

1,420- 1,765 Sand, clean. 

1,765- 1,785 Sand, silty. 

1,785- 1,835 Sand, clean. 

1,835- 1,840 Sand, clayey. 

1,840- 1,920 Sand, clean. 

1,920- 2,000 Clay. 

2,000- 2,410 Sand, clean. 

2,410- 2,448 Clay. 

2,448- 2,460 Sand, silty and clayey. 

2,460- 2,470 Clay, silty. 

2,470- 2,500 Sand or sandstone, fine-grained,

silty. 

2,500- 2,505 Sand or sandstone, fine-grained,

silty.

2,505- 2,520 Sandstone, fine-grained. 

2,520- 2,535 Sandstone, fine-grained, containing

clay beds. 

2,535- 2,750 Clay and (or) claystone (mudstone).

TABLE 4. Lithologic log of the COST No. B-2 wett 

 Continued

Depth 

(in feet)

2,750- 2,775

2,775- 2,810

2,810- 2,945

2,945- 3,005

3,005- 3,055

3,055- 3,065

3,065- 3,085

3,085- 3,162

At 3,162

3,162- 3,195

3,195- 3,210

At 3,211

3,212- 3,220

3,220- 3,235

3,235- 3,240

3,240- 3,255

3,255- 3,278

3,278- 3,280

3,280- 3,500

3,500- 3,535

3,535- 3,546

3,546- 3,547

3,547- 3,645

At 3,596

Unit lithologic description

Sandstone, fine-grained, micaceous.

Clay and (or) claystone.

Sandstone, fine-grained, silty and

clayey, micaceous.

Clay and (or) claystone, buff-colored.

Salt and clay and (or) claystone.

Sandstone very fine, silty.

Siltstone and claystone becoming

fine- to medium-grained sandstone

as depth increases.

Sand and sandstone, medium-grained,

clean, detrital lignite.

Sandstone, calcareous and (or) limestone, very sandy.

Sand and (or) sandstone, mostly

medium-grained, becoming coarsegrained in places.

Claystone and siltstone.

Limestone, very sandy and (or) sandstone, very calcareous.

Sandstone.

Clay (probably calcareous claystone,

siltstone, or shale) , very sandy

limestone at 3,230 to 3,231 feet

Sandstone.

Clay and (or) claystone, silty.

Sandstone, fine, medium- to coarsegrained and silty.

Limestone, sandy and silty or sandstone, silty, very calcareous.

Siltstone, claystone, somewhat sandy.

Sandstone, fine-grained, silty and

clayey.

Claystone and (or) siltstone, sandy.

Limestone, dark-grayish-brown,

clayey, also siltstone, dark and

calcareous.

Claystone or shale, calcareous.

Base of Miocene.

16
TABLE 4. Lithologic log of the COST No. B-2 wett 

Continued

Depth 

(in feet) Unit lithologic description

3,645- 3,655 Sandstone, somewhat calcareous and 

silty.

3,655- 3,720 Claystone and siltstone, sandy,

especially from 3,700 to 3,720 feet.

3,720- 3,930 Sand, clean, containing many silty 

sand intervals.

3,930 3,955 Claystone and silty clay, calcareous, 

dark-grayish-brown to brown, 

possibly somewhat dolomdtic.

3,955- 4,050 Clay or claystone, silty, calcareous 

at the top, becoming fine- to 

medium-grained sandstone at about 

4,000 feet.

4,050- 4,965 Calcareous mud (marl and possible 

chalk), light-gray to buff-colored, 

much calcareous sand. 

At 4,082 Base of Oligocene. 

At 4,964 Base of Eocene.

4,965- 5,000 Limestone, sandy or calcareous sandstones, sandstone at 4,975 feet. 

At 5,000 Base of Paleocene.

5,000 5,170 Sandstone, coarse, becoming finer and

more silty with depth. 

At 5,100 Base of Maestrichtian.

5,170- 5,200 Sand, fine-grained, silty; possibly

calcareous sandstone. 

At 5,200 Limestone bed (thin).

5,200- 5,296 Cay, sity, (siltstone and claystone)

dark-grayish-brown to gray, some 

mica present.

At 5,296 Limestone bed, thin, light-gray, slightly clayey.

5,297- 5,300 Sand, fine- to very fine grained, poorly 

sorted, clayey, gypsiferous, containing pyrite fragment (water worn), 

glauconite, lignite, fossil fragments, 

some limestone fragments.

5,300- 5,400 Siltstone and claystone, dark-grayishblack to brown, micaceous.

5,400- 5,685 Clay and (or) siltstone and claystone 

containing some calcareous clay 

zones and occasional beds of sandstone and calcareous sandstone, 

fossiliferous.

5,685- 5,796 Sandstone, very silty, becoming much 

more sandy with depth, micaceous, 

slightly calcareous. 

At 5,736 Base of Campanian.

5,796- 5,825 Sandstone, silty and containing calcareous sandstone layers at 5,798 to 

5,825 feet.

5,825- 5,920 Sandstone, silty, becoming less silty 

and slightly more calcareous with 

depth, a sandy limestone at 5,918 

feet.

5,920- 5,930 Sandstone.

5,930- 5,950 Siltstone and claystone, calcareous; 

sandy limestone bed at 5,932 feet.

5,950- 5,975 Sandstone, fine- to coarse-grained and 

silty.

5,975- 6,060 Sandstone, silty, micaceous and calcareous; very sandy limestone beds 

at 5,960 and 5,990 feet.

6,060- 6,075 Claystone, sandy.

6,075- 6,082 Sandstone, clean and porous, shell 

fragments.

6,082- 6,098 Claystone, sandy and calcareous, lightgray.

6,098- 6,118 Sandstone, fine- to coarse-grained, 

very clean; thin detrital lignite bed 

at 6,110 to 6,111 feet.

TABLE 4. Latlwlogic log of me (juai wo. v-z weu 

 Continued

Depth 

(in feet)

6,118- 6,122

6,122- 6,165

6,165- 6,172

6,172- 6,240

6,240- 6,263

6,253- 6,270

6,270- 6,282

6,282- 6,338

6,338- 6,345

6,345- 6,478

At 6,478

6,478- 6,500

6,500- 6,502

6,502- 6,512

6,512- 6,580

6,580- 6,595

6,595- 6,605

6,605- 6,615

6,615- 6,655

6,655- 6,715

6,715- 6,770

6,770- 6,795

6,795- 6,805

6,805- 6,825

6,825- 6,835

6,835- 6,840

6,840- 6,847

6,847- 6,850

6,850- 6,980

6,980- 6,995

6,995- 7,005

7,005- 7,018

Unit lithologic description

Claystone, light-gray, calcareous, lignitic fragments, limonitic and hematitic staining .

Sandstone, clean, porous, lignitic, pyritic, calcareous, with fossil fragments.

Limestone, gray, clayey, sandy, somewhat less calcareous at the base,

glauconite, micas, pyrite nodules,

and lignitic, limonitic, and aragonitic

fragments.

Sand, some very porous (clean) .

Sandstone, fine-grained, silty, and calcareous; abundant lignitic and cgaly

fragments at 6,245 to 6,250 feet.

Sandstone, very porous at 6,262 feet.

Sandstone, silty, calcareous, containing

some very impure limestones and

dolomitic limestones, chert, glauconite,

lignite, and hematite.

Sandstone, clean, micaceous, lignitic,

pyritic; very porous from 6,300 to

6,315 feet.

Clay, calcareous, micaceous, sandy,

gray, some pyrite and detrital lignite.

Sandstone, calcareous, especially at

6,345 feet and from 6,383 to 6,408

feet, clean, porous and coarse

grained from 6,410 to 6,460 feet.

Limestone very clayey, gray, containing lignitic fragments.

Sandstone, very calcareous, and (or)

limestone, very sandy.

Clay, calcareous, possibly a calcareous

shale, gray.

Sand, porous.

Shale, and (or) mudstone, sandy, calcareous, dark-gray, micaceous; very

calcareous from 6,512 to 6,540 feet.

Sand or sandstone, calcareous.

Clay or shale, very calcareous.

Sandstone, porous, very slightly calcareous.

Clay or shale, sandy and calcareous.

Sandstone, calcareous; gray, silty, calcareous beds at 6,661, 6,684, and

6,713 feet.

Clay and silt, gray to buff, sandy, and

very calcareous; shell fragment near

the base.

Sandstone, calcareous at 6,775 feet and

at 6,791 to 6,795 feet.

Clay or shale, light-gray, sandy, and

very calcareous.

Sandstone, slightly calcareous at the

top, becoming very porous toward

base; lignitic (?) zone at 6,818 feet.

Clay or shale, dark-gray, calcareous.

Sandstone, porous.

Clay or shale, sandy, calcareous, darkgray.

Sandstone, silty, calcareous.

Clay or shale, dark-brownish-gray to

gray, calcareous, sandy, gradually

becoming very calcareous near the

base, detrital lignite, mica.

Sandstone, porous, calcareous; detrital

lignite(?) at 6,980 feet.

Silt or siltstone, gray, calcareous.

Clay or shale, light-gray, silty, micaceous, sandy, and calcareous.

17
TABLE ^. Lithologic log of the COST No. B-2 well 

Continued

Depth 

(in feet) Unit litholcgic description

7,018- 7,022 Silt and (or) siltstone, sandy, very 

calcareous.

7,022- 7,500 Shale, claystone, siltstone and finegrained sandstone section, gray, very 

calcareous, some porous sandstone 

beds, fossiliferous, micaceous, carbonaceous, and pyritic. 

At 7,057 Base of Santonian-Coniacian.

7,500- 7,675 Sandstone, silty, gray, very calcareous 

from 7,620 to 7,670 feet, some 

brown vuggy dolomite interbedded 

with porous sand and siltstones. 

At 7,610 Base of Turonian.

7,675- 7,780 Siltstone and shale, sandy, very calcareous, containing intercalated 

limestone beds, light-gray from 7,730 

to 7,745 feet, fine-grained, calcareous, glauconitic siltstone.

7,780- 8,160 Sandstone and sand, fine-grained, 

some micaceous siltstones, darkgray and brown, very calcareous 

throughout, buff-colored limestones, 

slightly dolomitic, especially from 

7,770 to 7,830 feet, from 7,900 to 

7,915 feet, and from 8,010 to 8,055 

feet.

At 8,130 Base of Cenomanian (base of Upper 

Cretaceous).

8,160- 8,222 Siltstone and shale, sandy, very calcareous, many limestone beds 

throughout.

8,222- 8,260 Sandstone, very clean, porous, calcareous, especially at 8,222 and 8,255 

feet.

8.260- 8,282 Silts'-one-sandstone, very calcareous.

8,2«2- 8,295 Sandstone, clean, porous.

8.295- 8,305 Siltstone and shale, calcareous.

8,305- 8,445 Sandstone, locally calcareous, very 

porous at 8,375 to 8,385 feet, highly 

radioactive sandstone at 8,399 feet, 

possibly glauconite or phosphate 

pebble zones.

8,445- 8,452 Sandstone, shalv and calcareous, very 

calcareous at 8,450 feet.

8,452- 8,470 Sandstone, clean, porous.

8.470- 8.495 Sandstone, shaly, slightly calcareous.

8.495- 8.505 Siltstone, calcareous.

8.505- 8.522 Sandstone, calcareous.

8 522- 8.528 Siltstone and shale, calcareous.

8,528- 8,635 Sandstone, very slightly calcareous, 

thin limestone bed at 8,581 feet.

8,635- 8,655 Limestone, shaly and (or) calcareous 

shale.

8,655- 8,665 Sandstone, clean, porous. Vehlv radioactive sandstone at 8.fi55 *(*>t. DOSsibly a glauconite or phosphate pebble zone.

8.R65- 8.710 Limestone, shaly.

8-710- 8.735 Sandstone, clean, verv porous.

8,735- 8,770 Shale and siltstone. calcareous: th;n 

carbonaceous shale(?) at 8,745 

feet.

8 770- 8.775 Sandstone, clean, porous.

8,775- 8,840 Shale, verv calcareous, containing 

some thin sandstone beds.

8,840- 8,875 Sandstone, verv porous at base: abundant carbonate reduces porosity at 

top.

8,875- 8,900 Shale, very calcareous or a shaly limestone. 

At 8.900 Base of Albian.

8,900- 8,970 Sandstone, verv clean, porous, slightly 

calcareous at base.

TABLE 4. Lithologic log of the COST No. B-2 well 

Continued

Depth 

(in feet) Unit lithologic description

8,970- 8,995 Shale, very cacareous; probable lignite or coal bed at 8,993 feet.

8,995- 9,035 Sandstone, very porous.

9,035- 9,048 Shale, very calcareous.

9,048- 9,085 Sandstone, clean, very porous, somewhat calcareous at base.

9,085- 9,110 Shale, calcareous and sandy.

9,110- 9,142 Sandstone, calcareous.

9,142- 9,144 Shale, sandy, calcareous.

9,144- 9,170 Sandstone with limestone beds.

9,170- 9,180 Limestone.

9,180- 9,190 Sandstone, calcareous.

9,190- 9,220 Sandstone, calcareous, especially at 

9,200 feet.

9,220- 9,235 Limestone, shaly.

9,235- 9,255 Sandstone, calcareous.

9,255- 9,270 Shale, sandy and calcareous.

9,270- 9,280 Sandstone, clean and porous at base.

9,280- 9,295 Shale, siltstone and sandstone intercalations, sandy, and calcareous.

9,295- 9,305 Sandstone.

9,305-9,315 Shale, and siltstone, calcareous (?); 

strongly radioactive zone at 9,315 

feet, possibly a glauconite or phosphate pebble zone.

9,315- 9,345 Sandstone, calcareous especially at 

9,335 feet.

9,345- 9,355 Shale and limestone.

9,355- 9,365 Sandstone.

9,365- 9,372 Shale, rather calcareous.

9,372- 9,422 Sandstone, very porous, clean.

9,422- 9,428 Shale, calcareous.

9,428- 9,431 Shale, washout zone, coal bed at 9,428 

feet

9,431- 9,442 Sandstone.

9,442- 9,450 Shale, washout zone, coal bed at 9,448 

feet.

9,450- 9,462 Sandstone, calcareous and shaly.

9,462- 9,487 Sandstone, becoming more porous with 

depth.

9,487- 9,495 Shale, sandy, very calcareous.

9,495- 9,518 Sandstone, calcareous.

9,518- 9,530 Shale, very calcareous.

9,530- 9,610 Sandstone, clean, highly porous; very 

radioactive sandstone at 9,585 feet, 

possibly phosphatic or glauconitic.

9,610- 9,620 Shale, calcareous, sandy.

9,620- 9,680 Sandstone, calcareous at 9,630 feet.

9,680- 9,725 Shale, sandy, very calcareous from 

9,708 to 9,725 feet.

9,725- 9,748 Sandstone, porous, interbedded with 

less porous, carbonate-cemented 

zones.

9,748- 9,775 Shale, very calcareous throughout.

9,775- 9,790 Sandstone, porous.

9,790- 9,820 Shale, very calcareous, somewhat 

sandy at 9,798 feet.

9,820- 9,853 Sandstone, porous, becoming more carbonate cemented toward base.

9,853- 9,945 Limestone, shaly and sandy.

9,945- 9,958 Sandstone, high porosity.

9,958-10,000 Limestone, shaly and sandy, containing 

thin beds of sandstone; high radioactivity at 9,900 feet, possibly in 

glauconitic or phosphatic sandstone. 

At 10,000 Base of Aptian. 

10,000-10,025 Sandstone, high-porosity. 

10,025-10,050 Limestone, shaly, some calcareous

shales. 

10,050-10.055 Sandstone.

18
TABLE l. Lithologic log of the COST No. B-2 well 

 Continued

Depth 

(in feet) Unit lithologfic description

10,055-10,230 Limestone, shaly and (or) calcareous 

shale; washout zo*ne from 10,060 to 

10,200 feet probably because of dark 

carbonaceous shale and coal.

10,230-10,246 Sandstone.

10,246-10,248 Coal.

10,248-10,253 Limestone.

10,253-10,303 Sandstone, very porous.

10,303-10,306 Coal and dark shale, iron-oxidestained.

10,306-10,325 Shale, very calcareous, and (or) shaly 

limestone.

10,325-10,430 Sandstone, very porous.

10,430-10,450 Shale, calcareous, washout; probably 

a coal seam present.

10,450-10,456 Sandstone or siltstone.

10,456-10,480 Shale, calcareous, washout; probably a 

coal seam present.

10,480-10,530 Sandstone, very porous.

10,530-10,540 Shale, calcareous, and shaly limestone 

layer.

10,540-10,565 Sandstone.

10,565-10,582 Shale, calcareous; sandy, probably carbonaceous shale at 10,578 feet.

10,582-10,610 Sandstone.

10,610-10,755 Shale, calcareous; a few thin shaly 

limestones interbedded with thin, 

fine-grained sandstone; washout at 

10,710 and 10,720 feet; coal seams 

and rounded limestone concretions at 

10,732 feet.

10,755-10,800 Sandstone, porous; washout at 10,800 

feet may indicate thin coal seam.

10,800-10,805 Shale, very carbonaceous.

10,805-10,820 Sandstone, fair porosity.

10,820-10,835 Shale, slightly calcareous and (or) 

shaly limestone.

10,835-10,847 Sandstone, porous.

At 10,848 Washout, suggests shale containing 

thin coal seam.

10,849-10,894 Shale, some sandstone, slierhtly calcareous, especially at 10,876 feet. 

At 10,895 Coal seam.

10.895-10,906 Sandstone.

10,906-10,955 Shale, calcareous (especially at 10.919 

feet); coal seam at 10,927 to 10.928 

feet, FezO.1 staining; coal at 10,945 

feet.

10,955-10.985 Sandstone, high-porosity.

10,985-11,058 Shale containing shalv limestone hp*1s, 

especially at 10.993 feet; nrohable 

coal seams at 11.000 and 11,042 feet.

ll.05*-11,122 Sandstone, verv high porosity.

11.122-11.135 Shale, calcareous.

11,135-11,240 Sandstone, porous; calcarmns, nonporous sandstorm at 11,200 feet; 

coal seam at 11,139 feet.

11,240-11,245 Dolomite(?) or dolomitic limestone (?).

11,245-11,338 Sandstone, porous, but also tierht, 

containing somp calcareous beds, 

esneciallv at 11.2RO and 11.300 feet.

11,338-11,428 Shale, sandv, calcareous; some limestone, sandv and shalv.

11,428-11,445 Sandstone, siltstone, dense.

11,445-11,473 Shale, calcareous, carbonaceous, sandy, 

and shaly.

11,473-11,500 Sandstone, clean, porous.

11,500-11,550 Limestone, shaly to clean, possible 

dolomitic limestone layers present.

11,550-11,575 Sandstone, clean, porous, becoming 

denser at the base.

TABLE 4. Lithologic log of the COST No. B-2 well 

Continued

Depth 

(in feet) Unit lithologic description

11,575-11,605 Limestone, in part dolomitic and

sandy. 

11,605-11,620 Sandstone, porous; calcareous layer

at 11,615 to 11,617 feet.

11,620-11,635 Shale, very calcareous to shaly limestone. 

11,635-11,655 Sandstone, calcareous, slightly porous.

careous sandstone. 

11,655-11,765 Limestone, shaly, alternating with

calcareous sandstone. 

11,765-11,835 Sandstone, very porous; calcareous

zone at 11,800 feet.

11,835-11,870 Limestone and (or) shaly limestone. 

11,870-11,880 Sandstone. 

11,880-11,925 Limestone and dolomite (?) at 11,895

feet.

11,925-11,940 Sandstone, porous to nonporous, calcareous.

11,940-11,975 Limestone, shaly, and calcareous shale. 

11,975-12,030 Sandstone containing coal bed at

11,980 feet; calcareous at 12,012

feet.

At 12,000 Base of Valanginian. 

12,030-12,045 Limestone, and calcareous shale. 

12,045-12,060 Sandstone, very porous from 12,048 to

12,056 feet. 

12,060-12,100 Limestone, shaly, and calcareous

shale; thin sandstone at 12,008 feet. 

12,100-12,112 Sandstone, calcareous. 

12,112-12,140 Limestone, dolomitic. 

12,140-12,168 Sandstone, calcareous. 

12,168-12,210 Limestone, shaly. 

12,210-12,240 Sandstone; high radioactivity at 12,-

223 feet, possibly because of glauconitic or phosphatic zone.

12,240-12,274 Limestone, shalv containing conspicuous limestone bed at 12,263 to 12,266

feet. 

12,274-12,282 Sandstone, high radioactivity at 12,276

feet. 

12,282-12,322 Limestone, shalv; dolomitic limestone

at about 12.311 feet.

12,322-12.332 Sandstone, calcareous. 

12,332-12,334 Coal and carbonaceous shales. 

12,334-12,355 Sandstone, calcareous, slightly porous. 

12,355-12,402 Shale, calcareous. 

12,402-12 418 Sandstone, porous. 

12.418-12,420 Coal. 

12,420-12,430 Sandstone, calcareous, changing to

sandy limestone as depth increases. 

12,430-12,440 Limestone, dolomitic. 

12,440-12,462 Shale, sandy, calcareous; limestone

layers at 12,452 to 12,453 feet;

sandstone layer at 12,441 feet. 

12,462-12.464 Shale and coal. 

12,464-12,482 Shale, sandy and somewhat calcareous,

becoming more arenaceous as depth

increases.

12.482-12,492 Shale, sandy, calcareous. 

12,492-12,500 Limestone shaly, slightly dolomitic. 

12.500-12,520 Shale, calcareous, sandy near the base. 

12,520-12,575 Shale, calcareous. 

12,575-12,579 Coal, some shaly beds. 

12.579-12,595 Shale, sandy and calcareous. 

12.595-12,621 Sandstone, porous. 

12.621-12,623 Coal. 

12,623-12,633 Sandstone, slightly porous. 

12,633-12,670 Shale, carbonaceous, some coal. 

12.670-12,708 Shale, very calcareous. 

12.708-12.715 Sandstone, calcareous lavers. 

12.715-12,845 Limestone and dolomitic limestone. 

12,845-12.856 Coal and carbonaceous shale. 

12,856-12,872 Shale, very calcareous.

19
TABLE 4. Lithologic log of the COST No. B-2 well 

Continued

Depth 

(in feet) Unit lithologic description

12,872-12,890 Limestone and shale; conspicuous limestone beds at 12,875 to 12,882 ieet.

12,890-12,916 Sandstone, calcareous. 

At 12,916 Shale, sandy, carbonaceous.

12,917-13,003 Limestone, dolomitic, alternating with 

calcareous sandstone.

13,003-13,007 Coal.

13,007-13,075 Alternating calcareous sandstone and 

limestone beds; limestone becomes 

more dolomitic as depth increases.

13,075-13,090 Sandstone and arenaceous limestone.

13,090-13,100 Sandstone and limestone beds; high radioactivity and limestone at 13,090 

feet, possible glauconite or phosphate pebble zone.

13,100-13,138 Alternating calcareous sandstone and 

limestone.

13,138-13,140 Coal bed.

13,140-13,160 Sandstone and limestone.

13,160-13,170 Sandstone.

13,170-13,190 Shale, carbonaceous, coal at 13,179 

feet.

13,190-13,200 Sandstone, tight, slightly calcareous.

13,200-13,280 Sandstone, clean, porous except at 13,- 

208, 13,225, and 13,270 feet where 

calcite cement is especially abundant.

13,280-13,294 Shale, sandy, calcareous.

13,294-13,302 Sandstone or siltstone, high radioactivity at 13,292 feet.

13,302-13,330 Shale, calcareous, carbonaceous at 13,- 

314 feet.

13,330-13,350 Sandstone, clean, porous, high radioactivity at 13,331 feet.

13,350-13,375 Shale, carbonaceous siltstone.

13,375-13,429 Sandstone, porous.

13,429-13,440 Shale, carbonaceous, some siltstone.

13,440-13,443 Coal.

13,443-13,449 Shale and siltstone, carbonaceous, calcareous(?).

13,449-13,452 Coal and carbonaceous shale.

13,452-13,500 Alternating calcareous shale, siltstone, 

and sandstone; limestone at 14,492 

feet.

13,500-13,520 Sandstone, siltstone, probable siliceous 

cement.

13,520-13,524 Coal(?) and carbonaceous shale.

13,524-13,528 Shale.

13,528-13,538 Siltstone.

13,538-13,555 Limestone, sandy; dolomite or dolomitic limestone at 13,543 and 13,- 

548 feet

13,555-13,565 Sandstone, moderately porous, shaly.

13.565-13,572 Siltstone.

13,572-13,574 Coal seam.

13,574-13,605 Shale, carbonaceous, alternating with 

noncalcareous sandstone.

13,605-13,630 Sandstone, porous, somewhat calcareous at top.

13.630-13,642 Sandstone, calcareous,

13.642-13,655 Sandstone, slightly calcareous.

13,655-13,730 Shale, noncalcareous; calcareous at 

13,677 feet.

13,730-13,758 Shale, becoming IPSS calcareous and 

more sandy with depth.

13,758-13,825 Sandstone, clean, porous: limestone 

beds at 13,759 to 13,760 feet and 

at 13,808 to 13,810 feet.

13,825-13,890 Shale, carbonaceous; some siltstone 

and sandstone layers.

13,890-13,922 Sandstone, limestone bed at 13,912 

to 13,920 feet

13,922-13,925 Shale, carbonaceous.

TABLE 4. Lithologic log of the COST No. B-2 well 

Continued

Depth 

(in feet) Unit lithologic description

13,925-13,940 Siltstone.

13,940-14,010 Shale and sandstone. -

14,010-14,055 Sandstone; limestone at 14,011 and 

14,045 feet

14,055-14,070 Sandstone or siltstone.

14,070-14,098 Sandstone, noncalcareous.

14,098-14,185 Alternating calcareous and noncalcareous sandy shale and siltstone; 

limestone at 14,111 and 14,133 feet.

14,185-14,195 Sandstone.

14,195-14,235 Shale, sandy, in places slightly calcareous; siltstone, noncalcareous, at 

14,235 feet

14,235-14,270 Sandstone, porous to tight, calcareous (especially at 14,255 feet).

14,270-14,360 Shale and siltstone, sandy, mostly

noncacareous; calcareous at 14,286, 

14,296, and 14,310 feet, 14,314 to 

14,318 feet.

14,360-14,408 Sandstone, clean somewhat calcareous; impure limestone bed at 14,378 

feet.

14,408-14,544 Shale and siltstone, sandy, calcareous at 14,430 feet

14,544-14,546 Coal seam, thin, and fissile shale 

and siltstone.

14,546-14,570 Sandstone, clean, slightly calcareous at 14,548 feet.

14,570-14,608 Shale and siltstone; impure limestone bed at 14,606 to 14,608 feet; 

shaly sandstone at 14,598 to 14,602 

feet

14,608-14,625 Sandstone, noncalcareous.

14,625-14,668 Sandstone, porous and clean, calcareous from 14,638 to 14,645 

feet.

14,668-14,697 Shale and siltstone, dense, sandy,

very slightly calcareous; highly carbonaceous at 14,670 feet.

14,697-14,703 Sandstone, micaceous.

14,703-14,715 Shale and siltstone, sandy.

14,715-14,745 Sandstone, calcareous.

14,745-14,753 Shale and siltstone, sandy.

14,753-14,775 Sandstone, calcareous.

14,775-14,885 Shale and siltstone.

14,885-14,890 Sandstone, probably fine grained, 

silty, calcareous.

14,890-14,943 Shale and siltstone.

14,943-14,968 Sandstone containing very calcareous 

beds at 14,943 and 14,960 feet.

14,968-15,030 Shale and siltstone.

15,030-15,085 Shale and siltstone. arkosic to sub- ^

arkosic, micaceous, angular; cal*itecemented sandstone beds at 15,030 

feet.

15,085-15.108 Sandstone, calcareous.

15,108-15,205 Shale and siltstone. orasionallv *andv; 

calcareous at 15,110 to 15 120 feet; 

dolomitic limestone at 15,136 to 

15,140 feet

15,205-15,245 Sandstone beds, calcareous and 

noncalcareous, very coarse to 

medium-grained.

15,245-15,325 Shale and siltstone, some sandy 

claystone.

15,325-15,362 Sandstone, clean, very coarse, slightly calcite cemented; some beds 

quartz cemented.

15,362-15,443 Shale and siltstone; sandstone beds 

at 15,375 and 15.418 feet.

15,443-15,476 Sandstone, moderately porous, mostly noncalcareous,

15,476-15,482 Shale, carbonaceous, and coal.

20
TABLE'4. Lithologic log of the COST No. B-2 well 

Continued

Depth 

(in feet) Unit lithologic description

15,482-15,515 Sandstone, mostly noncalcareous.

15,515-15,595 Shale, siltstone.

15,595-15,610 Shale, sandy, and shaly sandstone.

15,610-15,687 Shale and siltstone, probably several 

thin coal seams.

15,687-15,705 Sandstone, sparse to abundant calcareous cement.

15,705-15,805 Shale, siltstone, and claystone, interbedded with occasional thin sandstone beds.

15,805-15,865 Sandstone, calcareous, coarse-grained 

sand to gravel.

15,865-15,882 Shale and siltstone.

15,882-15,895 Sandstone, slightly calcareous, coarsegrained,

15,895-15,950 Sandstone, calcareous and noncalcareous (alternating).

15,950-15,997 Shale, siltstone, and sandy siltstone; 

interbedded with sandstone, at 

15,978 feet.

15,997-16,043 Sandstone, low porosity in places

but vuggy and fairly porous elsewhere, very coarse to mediumgrained, calcareous to noncalcareous, some siliceous* cement.

and claystone), and carbonate rocks. Groupings 

of these rock types (table 5) are made to provide an insight into the amounts of reservoir

rock available. Certain parts of the shaly section above 9,100 feet and of the sandstone section below 9,100 feet, are very calcareous and 

have low porosity and high density; these particular calcareous shales and sandstones are 

classified with the limestone and dolomite 

grouping. Figure 7 is a graph showing the various measured, adjusted, and combined percentages of these three groupings of rock types 

penetrated in 1,000-foot intervals.

The dominance of sandstone and shale in the 

Baltimore Canyon trough is apparent. In fact, 

significant numbers of sandstone reservoirs and 

impermeable capping shales exist throughout 

the rock column, except perhaps for the 7,100- 

8,100-foot interval. Most of the sandstone beds 

are thicker than 10 feet, and some sandstone 

sections are more than 100 feet thick (see table 

4). Table 5 shows that a major part of the 

section below 5,100 feet (essentially the Cretaceous section) is composed of sandstone. However, as shown in the following discussion dealing with sandstone porosities, a significant percentage of this sandstone has low porosity.

TABLE 5. Sand, shale, and carbonate content in the COST No. B-2 well

[Values in parentheses are the actual measured values of shale and (or) sand lithology before subtraction of calcareous units, values in

percent]

Interval (feet)

1 100- 2,100 _____________ .

2,100- 3,100 ___________ .

3,100- 4,100 ___________ .

4,100- 5,100 ___________ .

5,100- 6,100 _ _ _ _ 

6,100- 7,100 ___________ .

7,100- 8,100 ___________ .

8,100- 9,100 ___________ .

9,100-10,100 ___________ .

10,100-11,000 ___________ .

11,100-12,100 ___________ .

12,100-13,100 ___________ .

13,100-14,100 ___________ .

14,100-15,100 ___________ .

15,100-16,043 ___________ .

Sand 

sandstone

. __ 75.5 (75.5)

. ______ 42.5 (42.5)

. ___ 35.5 (35.5)

. ______ 10.0 (10.0)

_____ 51.5 (51.5)

. ______ 65.5 (65.5)

. ______ 20.3 (25.8)

. ______ 28.6 (33.5)

. ______ 50.3 (58.8)

. ______ 41.5 (47.5)

. ______ 24.5 (60.5)

8.2 (30.0)

. ______ 41.8 (50.5)

. __ ___ 23.5 (26.5)

. ______ 24.0 (26.0)

Major lithologies

Clay, shale 

siltstone and claystone

24.5 (24.5)

61.5 (61.5)

61.5 (64.5)

88.5 (90.0)

46.5 (48.5)

33.3 (34.5)

74.2 (74.2)

61.6 (66.5)

32.2 (41.2)

52.5 (52.5)

39.5 (39.5)

70.0 (70.0)

49.5 (49.5)

73.5 (73.5)

74.0 (74.0)

Limestone, dolomite, 

calcareous shale, 

and (or) sandstone 1

0

0

3.0

1.5

2.0

1.2

5.5

9.8

17.5

6.0

36.0

21.8

8.7

3.0

2.0

1 Dense (low-porosity) calcareous zones are subtracted from the shale categories in most footages above 9,100 feet. Below 9,100 

feet, the dense calcareous zones are subtracted from the sandstone column.

21
Geologic age

Pleistocene(?) 

and Pliocene

V 

c 

o 

u 

o

is

Oligocene

Eocene

Paleocene

Cretoceous Lote 

3 

O

! <u

u

b

Depth, in feet 

(XI 000)

1.0- 

2.0- 

3.0- 

4.0- 

5.0- 

6.0- 

7.0- 

8.0- 

9.0- 

10- 

11- 

12- 

13- 

14- 

15-

Sand or sandstone

I

I >

"

"

1 1

(*

(«

o«

o«

1 * 

T *

(»

Ci

<> 

-lay, c aystone, 

shole, or si tstone

1

C>

C 1

C 

(

"

<

( 1 '

c >

<»

«'

Ci

{

'

.imestone, dolomite, and dense (limy) 

andstone or shale

(

::

r c

-

T

 True value (measured) 

o Adjusted value 

x Combined value

0 50 0 50 0 50 100

Percent (by volume)

FIGURE 7. Sand, shale, and carbonate content as a function of depth. Carbonate 

column includes dense, calcareous sandstones or shales. True values refer 

to the actual amounts of sand or shale measured; adjusted values are those 

derived by subtracting strongly calcareous units; combined values are given 

where the total carbonate amount as a combination of limestones, limy 

shales, and calcareous sands.

22
Sandstone Porosities

By E. C. Rhodehamel

Sandstone-porosity (0) values were derived 

from the BHC (sonic), FDC (density), and 

CNL (neutron) logs. Rather good agreement 

exists between porosity values determined from 

theisonic (fa), and density (fa) logs. However, 

the CNL-FDC (neutron and density) log 

showed that the neutron porosities (fa) were 

generally 2 to 30 percent higher than the fa 

values. Because the fa was calculated on the 

basis of sandstone densities, the calcareous 

zones, and particularly the dolomitic zones, 

tended to provide apparently low fa values. On 

the other hand, the neutron log tends to measure true porosity as long as the major source 

of hydrogen is in the form of water or oil. 

When other sources of hydrogen (that is, lignite, coal, or bound waters in shale, gypsum, 

and cristobalite) are present, the neutronporosity log measures inordinately high porosities. The presence of natural gas, on the other 

hand, leads to incorrectly low fa values. The 

disparity between fa and fa-is therefore accentuated in these zones. As the fa values were 

judged to be too high throughout much of the 

section, these porosities were not tabulated.

Figure 8 shows the plots of fa and fa versus 

depth. These data are taken on the average of 

about 200-foot intervals from the more extensive tabulations of fa and fa given in table 6.

The values of fa and fa are in reasonably good 

agreement throughout the entire section, fa 

values range from 68 percent at about 2,000 

feet to 2 percent at 16,007 feet. fa values range 

from 55 percent in a poorly consolidated section at about 1,400 feet to 6 percent at about 

15,000 feet. Both logs show decreasing porosity

as depth increases. Reduction in porosity with 

depth is to be expected in mineralogically immature sediments because of sediment compaction resulting from overburden pressure increase, as well as progressive cementation. 

Table 6 also presents porosity values determined by Core Laboratories (Smith and 

others, 1976). The porosity values were directly measured on conventional and sidewall 

cores. Corresponding permeability values (fig. 

5) were calculated from a plot of the grain 

size, shaliness, and permeability relationships 

of Gulf Coast samples.

The conventional core analyses (table 6) 

show a decrease in porosity with increased 

burial depth very similar to that noted in the 

log values; the permeabilities show a correspondingly rapid decrease with depth. The sidewall-core porosity values, on the other hand, 

show less of a decrease with progressive burial, 

and at the base of the well, these values were 

considerably higher than porosities determined 

by log analysis.

The section "Lithologic Description" notes 

that about 50 percent of the Cretaceous section 

in the B-2 well consists of rather thick sandstone units. These units have porosities ranging 

from about 41 percent at 5,700 feet (near the 

top of the Cretaceous) to about 4 percent near 

the base of the test hole. However, as shown 

by the data in table 6, the major part (as much 

as 75 percent) of the Cretaceous sandstone section has less favorable reservoir characteristics 

(porosities less than 10-15 percent), especially 

in deeper parts of the well.

23
FDC Density Log (<f>D ) and BHC Sonic Log

0 25 50 75 100%

1 I I I

FIGURE 8. Density and sonic log porosity as a function 

of depth.

24
TABLE 6. Comparison of porosity (<f>) values determined from electric log and core measurements on COST No.

B-2 well samples 

[Core 0 data from Core Laboratories, Inc. (Smith and others, 1976). Asterisk denotes determination from sidewall core samples]

Depth 

(in feet)

318 - 336 .... 

775 - 800 ....

990 - 1,025 __ 

1,228 - 1,298 .... 

1,275.0 _.___.......

1,345 - 1,360 ____

1,550 - 1,570 .... 

1,842 ______ _

1,750 - 1,762 .... 

2,009.0 ._._..._____

2,036 ____________

2,089.0 _.._.___..__

2,311.0 _...._.__.__

2,334.0 ...________.

2,448.0 ____________

2,480 - 2,500 .... 

2,509.0_ _ __.__.__

2,760 - 2,770 ____ 

3,056.0 ______ __

3,070 - 3,100 .... 

3,095 - 3,100 __ 

3,161.5.. 

3,165.0_. _ _

3,230.5 _...._.____

3,262.0 ____________

3,508 - 3,522 ____ 

3,545 ____________

3,645 - 3,652 ____ 

3,746 - 3,756 ____ 

3,800 - 3,900 ____ 

3,860 - 3,870 ____ 

4,040 __ ________

4,410 - 4,418 ____ 

4,975 - 4,985 ____ 

5,003 - 5,030 ____ 

5,030 - 5,070 __ 

5,030.2 ____________

5,031.0 ____________

5,031.4 ____________

5,070 - 5,150 ____ 

5,072.0 ____________

5,096.0 ______ __

5,100 - 5,150 ____ 

5,140.0 ____________

5,520 - 5,540 ____ 

5,615 - 5,620 __ 

5,680 - 5,700 ____ 

5,695 - 5,795 ____ 

5,750 - 5,775 __ 

5,920 - 5,930 __ 

5,920 - 5,931 __ 

5,964.0 ________

5.991.0 ____________

6,015.0 ___________

6,033 - 6,045 ____ 

6,079.0 ____________

6,102.0 ____________

6,107.0 ____________

6,125.0 ____________

6,136.0 ____________

6,157.0__ _________

6,185 - 6,206 ____ 

6,186.0 ____________

6,204.0 ____________

6.235.0 ____________

6,264.0 ____________

6,300 - 6,315 ____ 

6,301.0 ____________

6.329.0 __________

6,351.0 ___________

6,372.0 ____________

FDC 

(density 

log) 0a

45? 

41? 

40?

6~0"

68

53

52

49

59

46 

55 

48

28~~ 

32

32

 

2~2~~ 

22~

31

33

___

BHC 

( sonic

log) 0s

45"

55

49

45

48.5

44

44 ~

52 

51

52 

50

<5~0" 

38

31 

<12

3~3~~

 

38

35 

39 

41

29 " 

3~4~"

37

34

32

Core 0

28.4*

oq n*

29.0*

34.2*

34.0*

29.6*

3~3~9*

3~£5*

24.9*

26.6

26.7*

32.2*

____

24~.7~

30.9*

7.7

24.4*

32.6*

3~0~6*

2~6~1*

32.4*

33.2*

3"l.2*

28.6*

28.9*

33.1*

29.0*

32.8*

3Y.4*

25.4*

25.8*

30.0*

sire*

31.0*

31.2*

19.1*

Remarks

> Values probably too low.

Calcareous cement.

Rather poor definition.

25
TABLE 6. Comparison of porosity (0) values determined from electric log and core measurements on COST No.

B-2 well samples Continued

Depth 

(in feet)

6,418 - 

6,420 - 

6,421.0 

6,489.0 

6,507.0 

6,563.0 

6,572.0 

6,655 - 

6,669.0 

6,693.0 

6,785.0 

6,808.0 

6,818 __

6,819 __

6,953.0 

6,980 - 

6,991.0 _

6,992 __

7,555 __

7,560 - 

7,565.0 

7,574.0 

7,575 

7,659.0_

7,795 

7,975.0

8,225 - 

8,225 - 

8,230.0 

8,238.3 

8,239.5__

8,240.7 _

8,241.2 

8,242.5 

8,243.5 

8,244.0.

8,244.5-

8,245.8 

8,246.9-

8,247.8 .

8,248.8_.

8,249.6-

8,250.6-

8,251.4 .

8,252.4_.

8,253.0_.

8,253.7_.

8,254.5 .

8,255.5_.

8,256.5 _.

8,257.3_.

8,258.2_.

8,258.9_.

8,259.9_.

8,260.5_.

8,261.1 .

8,261.8_.

8,262.8_.

8,263.1 _.

8,264.9_.

8,289.0_.

8,321.0_.

8,325 - 

8,375.0_.

8.375 - 

8,399.0_.

8,410 - 

8,411.0

8,454 - 

8,479.0-

8,530 - 

8,533.0.

6,430 __ 

6,430 __

6,680 __

6,995 __

7,580 __

8,255 __ 

8,265 __

8,340 __

8,385 __

8,420 __

8,480 __

8,560 __

FDC 

(density 

log) 0d

33~

38 ~

22~

15 

17 ~

20""

BHC 

(sonic

log) (j>s

33

s'o"

2l"

29

29 

lY"

 

2"2~" 

22.5

22 "

26"

Core 0 Remarks

2~6~1*

28.7* 

31.8* 

24.5* 

23.3*

26.6* 

32.0* 

22.7*

2~2~2f* 

28.5*

21.T*

2~5".l* 

23.7*

25~4* 

2"5"6*

2~4~4* 

17.4 

16.2 

26.5 

18.6 

28.1 

18.4 

23.3* 

19.7 

19.2 

18.5 

20.7 

18.6 

11.7 

17.4 

18.2 

18.4 23.2* 

18.4 

20.8 

16.9 

12.6 

15.7 

16.8 

13.2 

9.7 

6.8 

13.1 

4.3 

3.6 

26.3 

28.7 

29.3 

30.7*

2~4~.8* 

2~8~.3* 

3~0"2* 

26.6* 

27~6*

26
TABLE 6. Comparison of porosity values determined from electric log and core measurements on COST No. 

B-2 well samples Continued

Depth 

(in feet)

8,559.0 ____________

8,580.0 ____________

8,587.0 ____________

8,606.0 ____________

8,659.0 ____________

8,715 - 8,730 ____ 

8,715 - 8,735 ____ 

8,730 - 8,738 ____ 

8,770 - 8,775 ____ 

8,849.0 ____________

8,870.0 ____________

8,910 - 8,950 ____ 

8,917.0 ____________

8,956.0 ____________

8,995 - 9,035 ____ 

9,065 - 9,380 ____ 

9,110 - 9,140 ____ 

9,147.0 __ ________

9,173.0 ____________

9,187.0 ____________

9,207.0 __ ________

9,236.0 ____________

9,280 - 9,330 ____ 

9,280.3 ____________

9,280.7 ___ _____

9,281.2 ____________

9,282.5 __ _______

9,283.2 __ _______

9,382.5 __ ________

9,283.8 ____________

9,284.7 ______ __

9,285.3 __ __ __

9,286.5_. ___ __

9,287.6 _________

9,288.5. ___ ____

9,289.5 __ _____

9,291.3 ____ _

9,292.5' . __

9,293.0 _________

9,293.3 ____ ___

9,294.5 __ _ __ _

9,295 __ _ _______

9,295.6 __ _______

9,296.3 ____________

9,297.2 ____________

9,297.5 ____ _ . .

9,298.8 ______ __

9,299.3 ____ ____

9,300.3 _________

9,302.2_ __ ___ _

9,302.7 .. ._ .

9,303.7 __ .. ____

9,304.4 __ __ __

9,305.4 __ __ __ _

9,306.3 __ __

9,306.6 ___ ______

9,307.7- __ __

9,308.4 ___ ______

9,309.2. ____

9,309.7 _ __ _

9,310.4 ____________

9,310.8 __ __ ____

9,311.5 ____________

9,312.5 ____ _____

9,313.4 _______ _

9,313.7 ____________

9,314.2__ _______

9,315.2 ____ ____

9,317.8 ___ ______

9,318.6 ____________

9,323.3 ____________

9,324.5 ____________

9.325.6 ____________

FDC BHC 

(density (sonic 

log) 0d log) </>s

21 

25 

23 

28

23

28 

10-14

17

23

Core 0 Remarks

30.6*

27 5*

29.6*

28.2*

27.2*

2~9~4*

29.4*

2~8~.l*

24.2*

 Averaged over the interval. 

Calcareous. 

25.8*

20.8*

27.2*

25.2*

30.5*

18.B"

15.1

13.6

13.8

11.3

18.4

17.9

12.0

6.1

8.7

5.5

25.7

25.3

7.9

15.8

27.8*

13.4

9.7

5.3

9.7

17.2

8.1

5.9

8.2

7.2

27.4

19.8

17.4

23.7

28.1

15.8

23.7

22.4

27.3

7.1

24.8

24.3

8.5

9.5

15.8

18.6

12.2

16.6

14.7

8.3

8.4 Fractured.

9.9

13.2

21.3

27
TABLE 6. Comparison of porosity (<f>) values determined from electric log and core measurements on COST No. 

B-2 well samples Continued

Depth 

(in feet)

9,326.4- __ _____

9,327.6 ___ ______

9,328.4 ____________

9,329.6 ____________

9,357.0 ___ __ _

9,362 - 9,412 ____ 

9,402 - 9,415 ____ 

9,467.0 __ ________

9,530 - 9,610 ____ 

9,534.0 __ ______

9,539.0_ __ __ _

9,545.0 __ ______

9,550 - 9,580 ____ 

9,569.0 ____________

9,597.0 ___ __ _

9,623.0 ____ ___

9,635.0 ___ __

9,655 - 9,660 ____ 

9,659.0 ___ ____

9,728.5_

9,748.0 __ ___

9,770 - 9,778 ____ 

9,773.0 ____ ____

9,778.0- __ __ __

9,779 __ __ ____

9,820 - 9,835 ____ 

9,825.0- __

9,882 ___ ____

9,918.0 ____________

9,953.0- ____ __

9,978 _ ____ _

10,000 -10,025 ____ 

10,007.0- __ __ _

10,051.0- ____ __

10,230 -10,245 ____ 

10,253 -10,303 ____ 

10,255 -10,290 ____ 

10,256.0- __ __ _

10,325 -10,428 ____ 

10,346.0- ___ ___

10,350 -10,430 ____ 

10,409.0 ___ _ _ _

10,429.0 __ _____

10,490 -10,530 ____ 

10,499.0_ __ ____

10,555.0_ __ __ ___

10,582 -10,610 ____ 

10,595 -10,610 ____ 

10,770 -10,780 ____ 

10,791.0. _ ________

10,805 -10,820 ____ 

10,817.0 ____ ____

10,899.0 __ ________

10,960 -10,980 ____ 

10,967.0 __ ________

11,035 _____ ___

11,037.0 ___ ______

11,058 -11,122 ____ 

11,060 -11,115 ____ 

11,064.0 ____ _____

11,102.0 __ ._ ____

11,115 -11,130 ____ 

11,141.0 ____________

11,173.0 ____ _____

11,205 -11,230 ____ 

11,216.0 ____________

11,255 -11,265 ____ 

11,257.0 ____________

11,280 -11,295 ____ 

11,310 -11,320 ____ 

11,384.0- __ ______

11,385 ____________

FDC 

(density 

log) 0d

24

21

 

 

 

13

16

17.4 

20

16

 

 

16

18

 _

12

13

 

 

 

 

BHC 

(sonic

log) 0s

23~5

___

22.5

>19

OO K

8

32.5

^ Q

19.5

___

<18

>20

>20~~ 

>20

 

20

<18~~

<12

<12

<12

12 

19

11

Core 0 Remarks

23.2

20.8

17.9

24.4

27.0*

~9~8*

2~6~8*

23.7*

27.3*

2~8~5*

9.9*

19.3*

27.5*

28~2*

2Q Q*

27.8*

9.0 

20.4*

22.5*

2~7~8*

30.1*

22.8*

27.0*

24.4*

22.4*

91 7*

20.8*

21.8*

sin Q*

179*

26.5*

oq Q*

24.7*

91 K*

22.7*

24~.b*

99 ft*

9ft 3*

1Q K*

25.0*

24.4*

20*7*

28
TABLE 6. Comparison. porosity (<f>) values determined from electric log and core measurements on COST No. 

B-2 well samples Continued

Depth 

(in feet)

11,424 -11,434 ____ 

11,435.0 ____________

11,476 -11,496 ____ 

11,483.0 _______ _

11,537.0 ____________

11,559.0 ____________

11,607.0 __ ________

11,635 -11,652 ____ 

11,638 -11,655 __ 

11,780 -11,800 ____ 

11,870 -11,880 ____ 

11,873.0 _ _ _____

11,928 -11,938 ____ 

11,975 ___ ______

11,980 -12,002 ____ 

11,981.0 ____________

11,984 -12,028 ____ 

11,999.0 ___ ______

12,021.0. __ _____

12,050 -12,055 ____ 

12,107 _ __ _

12,135 -12,150 ____ 

12,139.0 ____ ____

12,155 -12,165 ____ 

12,157.0 __ ________

12,214 -12,220 ____ 

12,215 -12,245 ____ 

12,218.0 __ __ ____

12,234 _ _________

12,289.0 __ __ _

12,400 -12,420 ____ 

12,402 -12,417 ____ 

12,515.0- __ ______

12,595 -12,620 ____ 

12,597.0 ____________

12,600 -12,615 ____ 

12,627.0 ___________

12,705 -12,720 ____ 

12,711.0 ____________

12,984 -12,989 ____ 

13,070 -13,095 ____ 

13,075 ______ __

13,083.0 ____ _____

13,085 __ _______

13,094 ____________

13,150 -13,170 ____ 

13,165.0- _________

13,195 -13,260 ____ 

13,200 -13,280 ____ 

13,217.0 ___________

13,243.0 ____________

13,295 -13,300 ____ 

13,349.0 ____________

13,380 -13,440 ____ 

13,390 -13,400 ____ 

13,409.0 __ _______

13,410 -13,430 ____ 

13,420 -13,440 ____ 

13,420.2 _____ ___

13,421.6 __ ______

13,422.4 ____________

13,423.3- __________

13,424.3 ____________

13,425.0-13,425.4 ____ 

13,425.8 ___ __ _

13,425.9-13,426.0 ____ 

13,426.8 _____ _ _

13,427.6 ____________

13,427.0-13,428.0 ____ 

13,428.3 _____ __

13,428.0-13,429.0 ____ 

13,429.3 _____ ____

FDC 

(density 

log) 0d

 

13

6

10 

14

11

 

 

___

10

8

12 

10

8

4

8

8"

___

9.2

f~

 

 

___

 

BHC 

(sonic 

log) 0s

19

___

lT.5 

12

12

20

<12

19

<12"

12

 _

11.5

11

8"

10

<15._

<n

<12"

<11.

 

 

 

 

Core 0

18~8*

22~8*

OA 9*

919 3*

18.3*

20.7*

189"

1~6~.5*

12.6*

1Q 1 *

179*

1~8~0*

15.4*

11.6*

20~4*

19 K*

1Q 7*

91 9*

91 1 *

23.6*

189*

99 1 *

91 ft*

198

1 q i

in Q

12.5

14.0

13.7 

12.5

16.0 

13.6

11.4

12.7 

13.9

16.4 

11.5

Remarks

Pinpoint fluorescence, weak odor.

Pinpoint fluorescence, weak odor.

Pinpoint fluorescence, weak odor.

Pinpoint fluorescence, weak odor.

29
TABLE 6. Comparison of porosity (<t>) values determined from electric log and core measurements on COST No. 

B-2 well samples Continued

Depth 

(in feet)

13,429.0-13,430.0 ____ 

13,430.3 __ __ _

13,430.0-13,431.0 ____ 

13,431.2 _______

13,431.0-13,432.0 ____ 

13,432.6 __ _ _ __

13,432.0-13,433.0 ____ 

13,433.2__ ___ __

13,433.6 __ ___

13,434.3 ______ __

13,434.6 _ _ __ __

13,435.4 __ __ _

13,436.5 __ ____

13,437.7 ____ _ __

13,438.7 __ ____

13,439.7 _ __ __ 

13,440.5__ __ ____

13,441.5 __

13,453.7 __ __ _

13,454.6 ____________

13,479.0 ____________

13,518.0 __ _____

13,603 -13,630 ____ 

13,610 -13,640 ____ 

13,614.0 _ _ _ _

13,758 -13,825 ____ 

13,770 -13,820 ____ 

13,905 -13,915 ____ 

13,906.0 __ __ __

13,931.0 __ ___

13,987.0 _

14,020 -14,050 ____ 

14,070.0 ______

14,092.0__ __

14,240 -14,270 ____ 

14,252.0 ___ ______

14,375 -14,400 ____ 

14,380 -14,405 ____ 

14,384.0_ ____ __

14,550 -14,570 ____ 

14,562.0_ _________

14,608 -14,627 ____ 

14,610 -14,625 ____ 

14,619.0 _ _ __

14,650 -14,665 ____ 

14,654.0- __ ______

14,720 -14,745 ____ 

14,755 -14,775 ____ 

14,781.0 __________

14,789.0 __ ______

14,890 __ _ _______

14,945 -14,965 ____ 

14,948 -14,958 ____ 

14,950 _ ___ _

14,960.0 ____

15,095 -15,100 ____ 

15,205 -15,245 __ 

15,205 -15,250 ____

15,242.0_ __ _

15,324.0. __' ______

15,326 -15,330 ____

15,345 -15,360 ____ 

15,346.0__ _ ______

15,375.0 ___________

15,417.0___ __ _ _____

15,443 -15,465 ____ 

15,445 -15,458 ____ 

15,447.0 _ __ _

15,458 -15,472 ____ 

15,506.0 __ ___ __

15,602 -15,610 ____

15,690 -15,695 ____

FDC BHC 

( density ( sonic 

log) 0a log) <}>s

 

 

 

10

11

III 11.5

<9

9

9

<11

7.6

10

8 

3.5

11

5.7

9 

5.4

6.5 

6.5

8.6

<6

7 

<6

Co.,

15.3 

4.9

11.3 

11.6

14.1 

10.6

14.1 

10.6

4.1

7.0

7.5

4.0

3.2

3.5

5.8

4.5

5.6

7.0

4.7

7.7

21.0*

17.6*

18.5*

lY.9*

15.9*

17 Q*

20.8*

91 ^*

-\a q*

q fl*

17.5*

1Q Q*

U.7*

ib"6*

7.6*

137*

17.7*

lY.4*

1Q Q*

l¥.4*

14.4*

1 7 Q*

lY.4*

15.0*

Remarks

Pinpoint fluorescence, weak odor.

Pinpoint fluorescence, weak odor.

Pinpoint fluorescence, weak odor.

Pinpoint fluorescence, weak odor.

30
TABLE 6. Comparison of porosity (<f>) values determined from electric log and core measurements on COST No. 

B-2 well samples Continued

Depth 

(in feet)

15,695 -15,702 ____ 

15,703 -15,710 ____ 

.15,803 -15,808 ____ 

15,805 -15,865 ____ 

15,813 -15,844 ____ 

15,854 -15,874 ____ 

15,875 -15,898 ____ 

15,883 __ _ ______

15,890.0 ____

15,905 -15,910 ____ 

15,922 ____________

15,948 -15,956 ____ 

15,954.0 ___ __ __

15,968 -15,976 ____ 

15,995 -16,015 ____

FDC 

(density 

log) <{>A

¥.3

5

 

T

BHC 

(sonic 

log) 0 S

6.5 

6

7 

8

 

>7

7

Core 0 Remarks

10~8*

11.0*

10~5*

12.3*

31
Sandstone Petrography

By P. A. Scholle

Sandstone chips were handpicked from rotary drill cuttings at 72 levels below 8,000 feet. 

Sandstone at these depths was judged likely to 

have the greatest overall reservoir potential 

and diagenetic complexity. One or more thin 

sections were cut for each interval, and from 

4 to 10 chips representative of each interval 

were used. The sections were stained for potassium feldspars and were examined by means 

of a standard petrographic microscope. The results are shown in table 7.

The grain-size columns merely indicate the 

coarseness of the material examined petrographically and do not necessarily reflect the 

average grain size of sand in that interval. 

Coarser sand and gravel commonly would disaggregate into individual constituent grains, making- examination of representative rock textures 

impossible. This petrographic analysis, therefore, emphasizes the finer grained and more 

lithified units in the section. Nevertheless, the 

overall changes in rock composition, fabric, and 

diagenesis described in the selected samples are 

probably representative of the whole section.

COMPOSITION

The entire section from 8,000 to 16,000 feet is 

feldspathic, and most sandstone is classed as 

subarkose. From 8,000 to about 12,800 feet, 

potassium feldspar (orthoclase and microcline) 

predominates, plagioclase is quite subordinate 

or absent. From about 12,800 feet to the bottom 

of the well, plagioclase feldspar increases in 

abundance and constitutes a significant rockforming element. The change in feldspar composition most likely reflects changes in provenance rather than selective interstratal destruction of plagioclase because, whenever present, 

plagioclase is less altered than the potassium 

feldspar.

Rock fragments are present throughout the 

section although they are never a major rockforming element. Both sedimentary (shale and 

limestone) and metamorphic (slate, phyllite, 

schist, and gneiss) rock fragments were noted 

at many levels, and no particular evidence of 

progressive unroofing of source areas was 

seen.

Most of the sediment from 8,000 to 9,740 

feet contains glauconite of both pelletal and 

vermicular types. Some trace of glauconite is 

found to depths of about 10,100 feet; virtually 

none is present below that depth. The glauco^- 

nite, in conjunction with the calcareous fossils 

and abundance of limestone noted in between 

8,000 and 10,140 feet, indicates dominantly 

marine depcisitional conditions.

Sandstone throughout the 8,000-16,000-foot 

section is micaceous and pyritic, although at 

some intervals the pyrite has undergone partial 

alteration to iron oxide. Lignitic inclusions are 

present, especially near 10,000 feet, 11,000 feet, 

12,600-13,000 feet, and 13,900-15,100 feet. 

Heavy minerals are present but were not specifically studied in this initial investigation. 

The occurrence of authigenic overgrowths on 

detrital tourmaline in the 15,260-foot sample 

indicates that marine incursions are present 

even in this part of the section because the 

boron of marine waters is needed to produce 

such overgrowths.

DIAGENESIS AND CEMENTATION

The loss of porosity as a function of burial 

depth in the COST No. B-2 well is noted in 

the section "Sandstone Porosities" and in direct laboratory measurements of petrophysical 

properties of the sidewall and conventional 

cores (Smith and others, 1976). The causes of 

this depth-related porosity loss are complex but 

are decipherable from petrographic analysis.

32
Depths given in feet and represent 30-foot

sampling intervals from stated depth

downward; X = common; XX=very common; t=trace; ? = possible 

Grain size:

S = Silt

Fi = Fine to very fine sand

M = Medium sand

C = Coarse sand and gravel 

Constituents:

Q=Quartz

K=K-Feldspar

P = Plagioclase

RF=Rock fragments

GL = Glauconite

PY=Pyrite

TABLE 7. Petrography of sandstone from the COST No. B-2 well

MI=Mica

LI =r Lignite 

Diagenesis

Fr = Fresh unaltered feldspar

Al = Altered (sericitized, vacuolized, or 

calcitized) feldspar

Co = Compaction features

Or = Grain orientation 

Cement

Qo = Quartz overgrowths

CL = Clay (authigenic) 

CA = Calcite

DO = Dolomite

SI=Siderite 

Rock name (Classification from Folk, 1968)

Q A=Quartzarenite

FQA=Feldspathic quartzarenite 

SA = Subarkose 

A = Arkose 

Mst=Mudstone 

Miscellaneous 

F = Fossil if erous 

Ls = Limestone 

Oo = Oolite 

Sc=Sericite 

Chl = Chlorite

MRF = Metamorphic rock fragments 

SRF = Sedimentary rock fragments 

CF = Calcitized feldspar 

PC = Poikilitic calcite 

To = Tourmaline overgrowths

Depth

8,030

8,210

8,250

8,290

8,390

8,420

8.480

8,510

8,570

8,700

8,780

8,870

8,980

9,080

9,170

9,260

9,380

9,410

9,510

9,620

9,710

9,740

9,860

9,950

10,010

10,070

10,140

10,330

10,420

11,320

11,530

11,620

11,740

11,830

11,920

12,000

12,130

12,250

12,340

12,600

12,740

12,830

12,980

13,100

13,220

13,370

13,570

13,660

13,810

13,910

14,050

14,140

14,210

14,270

14,300

14,420

14,670

Grain size 

S Fi M

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

C Q

X

X

X X

X X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X X

X

X X

X X

X X

X

X

K

X

X

X

X

X

X

X

X

X

X

X

t

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

t

X

X

X

X

X

X

X

X

X

X

Constituents 

P RF GL PY

X

t

X

X

X

X

X

t X

t X

t X

t

X

X

t X

?

t

t

X

X

X

X

t X

X X

t X

X

X t

X

t X

X X

X X

X

X

XX

X

X

X

X

X

t

t

X

X

t

t

X

X

XXX

X

X

X

X

X

X

X t

X X

X

X

t

X

t

X

t

X

t

X

X

X

X

X

XX

X

X

t

X

t

X

X

X

t

X

X

X

X

X

X

X

X

X

X

X

t

t

X

X

X

X

X

MI

X

X

X

X

X

t

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Diagenesis 

LI Fr Al Co Or

X X

X

X

X t

X X

? X

X

X

X X

X

X X

X

X

X X

X

X X

t X

XX X

X

X

X XX

X XX

X X

X X

X

X X

X X

X

X

X

X

X X

X X

X X

X XX

X

t

X t X

X

t X

X X

X X

X

X X

XX X

X

X XX

X X

X X

X

t

XX X

Qo

t

t

t

t

t

X

t

X

t

t

X

X

t

X

X

X

X

X

X

t

X

X

X

Cements 

CL CA DO

X

X

t

X

X

X

X

?

?

X

X

X

X

X

X

X

X

X

X

t

t

X

X

X

X

t

X

t

X

t

X

X

XX

X

X

X

X

XX

X

X

X

X

XX

XX

XX

XX

XX

XX

X

XX

X

XX

X X

X

X ?

X X

X

XX

XX

X

XX ?

X

X

XX

XX

XX

XX

X

X

X

XX

X t

X

X

X

XX

X

X

X

XX

X

X ?

X

t

t

t

X

X

XX

t

X

Rock 

81 name

FQA-SA

FQA

SA

FQA-SA

SA

FQA

SA-A

SA

FQA-SA

QA-SA

FQA-SA

QA

? FQA

SA-Mst

SA-A

SA-A

X SA

X SA

FQA

SA-A

SA

SA

SA-A

FQA-SA

SA-A

QA-SA

? SA-Mst

X SA-QA

SA-Mst

SA-Mst

SA-QA

t A-SA

SA

FQA

SA

A-SA

SA

SA-QA

QA-SA

t QA

SA-A

X SA-QA

QA-SA

X SA-QA

SA

A-SA

X SA

FQA-SA

A-SA

SA-A

SA-A

A-SA

A-QA

SA

SA-A

QA-SA

SA

Miscellaneous

F, Ls

F, Ls, PC

F, Ls

F, Ls, SRF

F, Ls, PC

F, Ls, PC

SRF, PC

PC

Ls

Chl-Sc

F, Ls, SRF

F, Ls

F, Ls

F

F, Ls, MRF

F, Ls

F, PC, MRF 

SRF

SRF, MRF, 

PC

PC, Ls, SRF

F, Ls

F, Ls

F

F, Ls, Ser, 

MRF

Ls, Sc, PC, 

SRF

Ls, F

Ls

F

PC, F, Oo

Oo, F, Ls 

SRF

PC, SRF

SRF

F, PC, SRF

SRF, Sc

PC, Oo, F

PC, SRF, 

CF

SRF, MRF, 

Ls

SRP, Ls

SRF, Sc

Sc

SRF, Sc

Sc

SRF

SRF

CF, SRF

PC, CF

MRF+SRF

33
TABLE 7. Petrography of sandstone from the COST No. B-2 well Continued

Grain size Constituents Diagenesis Cements Rock MisDepth S Fi M C Q K P RF GL PY MI LI Fr Al Co Or Qo CL CA DO SI name cellaneous

14,750 XXXXt X XX QA-SA SRF, CF

14,810 XX XXXt XXX XX tXX QA-SA

14,870 XXXXtt X tXX QACF

14,930 XX XXXX XX X XXXX QA-SA SRF

14,990 XXXtXXX XX XX QA SRF

15,140 X XXXX Xt XX SAPC

15,260 XXX X XX XXX SA To

15,380 XXXXX XXXX SA

15,470 XXXXX XX XXX QA-SA

15,530 XXXXXX XXXX QA SRF

15,650 XX XXXX Xt XXt SA

15,740 XXXXX X X ? QA CF

15,800 X XXXX X X?X FQA SRF

15,950 XXXXX X XX QA

16,040 XXXX X X ? QA-SA

In the depth interval examined, compaction effects are significant. Crushing of relatively soft

grains (such as glauconite or mica), reorientation of elongate grains, and shattering or

twinning of brittle minerals are commonly

noted. Grain interpenetration through pressure-solution embayment was less commonly

found. Thus, mechanical compaction resulting

from increased subsurface lithostatic pressures has played an important role in porosity

loss.

Perhaps even more important, however, are

the chemical effects of mineral alteration and

cement precipitation. Starting at 12,600 feet

or earlier, alteration of feldspar (both potassium feldspar and plagioclase) becomes progressively more important as burial depth increases. This alteration takes the form of

sericitization, kaolinization, vaeuolization, or

calcite replacement and varies from one unit to

the next. However, the general increase in

feldspar alteration with depth can be correlated

with the increasing . importance of authigenic

clay minerals and quartz overgrowths as cementing agents. In many of the samples from

13,000 feet downward, kaolinite, illite, sericite,

or authigenic silica produce almost complete

obliteration of primary porosity.

Calcite is also extremely important as a cementing agent. In the depth range from 8,000

to 13,000 feet, calcite is clearly the major cement. Below 13,000 feet it remains important

but begins to be overshadowed by clay and

silica cement. The abundance of calcareous fossils, limestone, and limestone clasts in the parts

of the section containing the greatest amounts

of calcite cement indicates that at least some

of the cement may be derived by in situ dissolution of calcareous material and reprecipitation as cement. The common poikilitic textures

of the calcite cement indicate that the presence

of carbonate skeletal or rock fragments is a

factor in the nucleation of calcite cement.

Other calcareous cement, including dolomite,

ankerite, and siderite, is occasionally observed

but is rarely of major importance. The only

zones containing significant siderite cement are

at 9,300-9,500 feet, 10,330 feet, and between 

12,800 and 13,600 feet.

The predominance of arkosic sediments

throughout the section coupled with their

burial-related decomposition leads to significant

porosity loss in the deeper part of the section

in the COST No. B-2 well. In addition, zones

containing significant marine fossils, limestone,

or associated calcareous shale have the greatest

amounts of carbonate cement. Prospects for

improved porosity at equivalent or greater

depths at other sites are relatively unfavorable

unless a significantly less arkosic section is

found or unless some other factor such as geo>-

pressuring or oil saturation has retarded the

breakdown of feldspar.

34
Foraminiferal Biostratigraphy

By C. W. Poag

Upper Tertiary sediments in the COST No. 

B-2 well were deposited in shallow marine or 

nearshore subaerial environments. During the 

early Tertiary, however, especially during the 

Eocene, carbonate rocks were deposited at Continental Slope water depths. Most of the Upper 

Cretaceous strata are fully marine, containing 

diagnostic planktonic and benthic fossils that 

indicate shelf conditions of deposition. In contrast, during the Early Cretaceous, many of the 

beds accumulated under subaerial conditions, 

as shown by the lack of marine fossils and the 

abundance of terrestrial palynomorphs. The 

age of the oldest strata penetrated was not established in this foraminiferal study.

The following discussion of foraminifers is 

based on preliminary analyses of samples from 

rotary cuttings taken at widely spaced intervals, ranging from 100 to 500 feet. The conclu*- 

sions are tentative and are subject to revision 

upon further detailed study.

PLEISTOCENE

The youngest sample examined came from 

610 feet and contained an abundant benthic 

fauna of Pleistocene species, most of which 

have living representatives off New Jersey 

today. Diagnostic forms include Elphidium orbicular e, E. clavatum, Cibicidoides lobatulus, 

Epistominella vitrea, Nonionella atlantica, and 

Bulimina aculeata. Similar assemblages are 

present to 790 feet and contain scattered occurrences of reworked Eocene species.

PLIOCENE

At 880 feet, the first significant change in 

species composition occurs. Particularly diagnostic is Buliminella gracilis, which is abundant in the Miocene and extends in fewer numbers into the Pliocene. Its sparsity and its association with a meager planktonic fauna of

Globigerina bulloides and Globigerinoides trilobus appear to indicate a Pliocene age for this 

sample.

MIOCENE

The first examined sample containing significant numbers of typical Miocene species was at 

1,090 feet. Buliminella gracilis is abundant and 

is accompanied by Lenticulina spinosa, Florilus 

pizzarensis, and abundant specimens of Uvigerina sp. and Cibicidoides sp. No diagnostic 

planktonic species are present. From 1,090 feet 

to 1,480 feet, similar but sparser faunas dominated by B. gracilis are present.

At 1,510 feet is the first indication of middle 

Miocene age. Turborotalia siakensis, which becomes extinct in Zone N. 14 (Blow, 1969), is 

rare in this sample. Buliminella gracilis is still 

the predominant taxon. The Miocene section 

above 1,510 feet, therefore, is placed in the 

upper Miocene.

Similar shallow-water faunas dominated by 

B. gracilis, which is often the only taxon present, are present throughout the interval between 1,510 feet and 2,710 feet. Turborotalia 

siakensis occurs sparsely in scattered samples 

throughout this interval. At 2,710 feet, the 

foraminiferal association is the same, but diatoms begin to appear in significant numbers. 

At 2,800 feet, among an abundance of diatoms, 

T. peripheroacuta appears, indicating a middle 

Miocene age, no younger than Zone N. 12 and 

no older than N. 10. At 2,890 feet, diatoms are 

still abundant, along with B. gracilis. Occasional specimens of T. siakensis and T. peripheroacuta are found and radiolarians are 

present occasionally.

The next major faunal change takes place 

at 3,880 feet, where B. gracilis is no longer 

predominant, and where Globigerinita ciperoensis and Turborotalia continuosa indicate an 

early Miocene age, no younger than Zone N. 6.

35
EOCENE

At 4,200 feet, the first rich late Eocene 

fauna is found. Typical planktonic species include Turborotalia cocoaensis, T. cerroazulensis, T. pomeroli, T. ampliaperatura, Globigerinatheka index, Hantkenina alabamensis, and 

PseudoJiastigerina micra. The rich benthic 

fauna includes Bulimina jacksonensis, Sigmoidella plummerae, Anomalina alazanensis, and 

Lenticulina subpapillosa. This assemblage is no 

younger than Zone P. 17 (Blow, 1969).

Middle Eocene species are present* in the 

sample at 4,500 feet. Diagnostic forms include 

Acarinina densa, Truncorotaloides topilensis, 

Morozovella aragonensis, and Acarinina penta~ 

camerata. These forms represent Zones P. 11 

to P. 8.

The sample at 4,800 feet is of early Eocene 

age, containing Planorotalites chapmani, Pseudohastigerina wilcoxensis, Subbotina frontosa, 

and S. inaequispira.

PALEOCENE

At 5,110 feet, the presence of Acarinina uncinata, A. soldadoensis, Morozovella velascoensis, M. kolchidica, and M. aequa suggests a late 

Paleocene age, probably Zone P. 5. A few reworked Cretaceous species also begin to appear.

An unusual association of shallow-water agglutinated foraminifers, abundant plant fragments, and gypsum crystals at 5,300 feet cannot be dated by means of foraminifers; it suggests restricted environmental conditions that 

might exist in a lagoon or estuary.

CRETACEOUS

The first sample examined containing abundant Late Cretaceous species came from 5,600 

feet. Diagnostic forms include Globotruncana 

fornicata, G. elevata, G. area, Rugoglobigerina 

rugosa, Cibicidoides micheliniana, Planulina 

texana, Kyphopyxa christneri, Lenticulina 

pondi, and Pseudogaudryinella capitosa. This 

assemblage appears to be of Campanian or 

Early Maestrichtian Age. At 5,900 feet, the 

first Bolivinoides was observed, appearing to 

be B. miliaris, a late Campanian and early 

Maestrichtian species.

From 5,900 feet to 7,100 feet, the faunas ap^ 

pear to be largely cavings from younger Tertiary beds. Few, if any, indigenous Cretaceous 

species are present. At 7,100 feet, however, the 

presence of Globotruncana Helvetica, and G.

imbricata indicates sediments of Turonian Age. 

G. Helvetica is still abundant at 7,400 feet.

At 7,700 feet, Cenomanian species are present. They include Rotalipora cushmani, Praeglobotruncana stephani, and P. cf. turbinata.

The Lower Cretaceous strata (Albian) begin 

at approximately 8,200 feet, marked by Favusella washitensis.

Below this point, the foramdniferal faunas 

are sparse and appear to be primarily composed 

of cavings from the younger beds. Few, if any, 

indigenous specimens occur.

PALEOECOLOGY

During the Early Cretaceous, the B-2 area 

apparently was a coastal region in which primarily continental deposits accumulated, as 

shown by the sparsity of marine fossils and 

the abundance of terrestrial plant remains, coal 

beds, and nonmarine sand and clay. At some 

time during the Albian, however, a shallow 

marine sea occupied the B-2 site, and deposited 

marine microfossils and nannofossils. The generally shallow marine environment persisted 

throughout most of the Late Cretaceous. The 

notable exceptions are represented by the sediments from approximately 7,100 feet to 6,200 

feet, in which no marine fossils are present, 

and the sample at 5,300 feet, which may have 

accumulated in estuarine conditions.

During the Paleocene, shallow shelf conditions again were predominant. During the 

Eocene, however, the water depth increased to 

the equivalent of that on today's Continental 

Slope; the richest faunal remains in the B-2 

well accumulated during this period.

During the Miocene and Pliocene, the environment fluctuated frequently from inner- to 

outer-shelf depths, and occasionally subaerial 

erosion took place marked by oxidation and 

abrasion of fossil remains. The rich diatom 

floras of the middle Miocene reflect a specialized environment of high nutrient content, 

brought about, perhaps, by cool waters upwelling along the shelf edge. The Late Miocene 

faunas are of very low diversity and are foufrid 

amidst sandy beds in what appear to have been 

prograding deltas. The Pleistocene was a time 

when coarse glacial sand and gravel accumulated in shallow marine waters and in terrestrial coastal-plain environments. No obvious 

cyclicity of glacial-interglacial sequences was 

noted during the preliminary analysis.

36
Nannofossil Biostratigraphy

By P. C. Valentine

This preliminary study is based on an analysis of samples from rotary cuttings spaced at 

100-foot and 300-foot intervals. Discrete rock 

fragments representing each of the major lithologic units present in a single sample were 

selected and processed. The oldest assemblage 

identified in a sample was considered to indicate the age of the strata at that level. As many 

as five subsamples were studied from a single 

10- to 30-fcot-interval sample. Settling techniques were used to concentrate the sample for 

study of the calcareous nannofossils. Zonal data 

are summarized in table 8.

PLEISTOCENE THROUGH MIOCENE 

(^700 FEET TO s-3,730 FEET)

Strata of Pleistocene through Miocene age 

are present to a depth of approximately 3,800 

feet. The highest sample available for study 

was from 700 to 730 feet, in which calcareous 

nannofossils are rare and tentatively indicate 

a Pleistocene age. Samples from 790 feet 

through 3,520 feet are essentially barren. Diatoms, however, are particularly abundant from 

2,890 feet through 3,520 feet; this interval has 

been dated as middle Miocene on the basis of 

a study of the foraminifers. Recent studies 

have shown that this sequence of mainly shallow-water terrigenous clastic sediment is 

characteristic of this age interval elsewhere on 

the Continental Shelf north of Cape Hatteras.

Calcareous sediments of early Miocene age 

are found from 3,580 feet to 3,730 feet. Two 

samples (3,580-3,610 feet and 3,700-3,730 

feet) were investigated from this interval and 

found to contain the following assemblage, 

which is representative of the upper part of 

the Triquetrorhabdulus carinatus Zone of 

Bukry (1973, 1975) : Coccolithus eopelagicus, 

C. pelagicus, Coronocyclus nitescens, Cyclicargolithus abisectus, C. floridanus (abundant),

Discoaster adamanteus, D. deflandrei, D. 

druggi, D. saundersi (common), D. variabilis, 

Discolithina spp., Helicosphaera euphratis, H. 

intermedia, H. recta, Reticulofenestra cf. R. 

scissurus of Bramlette and Wilcoxon (1967), 

Sphenolithus capricornutus, S. dissimilis, S. 

moriformis, and Triquetrorhabdulus carinatus.

OLIGOCENE 

(s-3,790 FEET TO ^4,050 FEET)

Calcareous strata of late Oligocene age are 

found in the interval bounded by samples from 

3,790 to 3,820 feet and 4,030 to 4,050 feet. 

These sediments contain the following assemblage, characteristic of the Sphenolithus ciperoensis Zone of Bukry (1973, 1975): Chiosmolithus altus, Coccolithus eopelagicus, C. pelagicus, Cyclicargolithus abisectus (abundant), 

C. floridanus (abundant), Dictyococcites bisectus, Discoaster deflandrei, D. rufus, D. saundersi, Discolithina spp., Helicosphaera bramlettei, H. euphratis, H. intermedia, H. wilcoxoni, Reticulofenestra cf. R. scissurus of 

Bramlette and Wilcoxon (1967), Sphenolithus 

dissimilis, S. moriformis, S. ciperoensis, and 

Zygrhablithus bijugatus.

OLIGOCENE THROUGH EOCENE 

(^4,080 FEET TO s-4,320 FEET)

Calcareous strata of earliest Oligocene to 

latest Eocene age are present in the interval 

bounded by samples from 4,080 to 4,110 feet 

and 4,290 to 4,320 feet. These sediments contain the following assemblage, indicative of the 

Coccolithus subdistichus and Isthmolithus recurvus Subzones of Bukry (1973, 1975) : Chiasmolithus oamaruensis, Coccolithus eopelagicus, 

C. pelagicus, C. sarsiae of Bybell (1975), C. 

subdistichus (common), Cyclicargolithus floridanus, Cyclococcolithina formosa, C. kingii,, 

Dictyococcites bisectus, D. scrippsae, Discoli37
Age

Quaternary

Pliocene

Miocene

4> 

c 4> u 

o 

ac

O

Eocene

Paleocene

1 Cretaceous

Boundary Calcareous Nannofossil

(m.y.) zone subzone

n ^ Emiliania buxleyi

' Gepbyrocapsa 

09 oceanica

. ' , Crenalithus 1.6 - , ... 

, o dorontcotdes

Discoaster 

2*e brouweri

\ n

 *' Reticulofenestra 

->.' pseudoumbilica

4.4 - Ceratolitbus

5.0 tricorniculatus

Discoaster 

quinqueramus

', Discoaster 

11 0 neobamatus

I 20 Discoaster 

' hamatus

" Catinaster coalitus

,i~4 Dtscoflsfer 

!4 o exi/r's

Ceratolitbus cristatus

Emiliania ovata

Gepbyrocapsa caribbeanica

Emiliania annul a

Cyclococcolitbina macintyi

Discoaster pentaradiatus

Discoaster surculus

Discoaster tamalis,

Discoaster asymmetricus

Sphenolitbus neoabies

Ceratolitbus rugosus

Ceratolitbus acutus

Triquetrorbabdulus rugosus

Ceratolitbus primus

Discoaster berggrenii

Discoaster neorectus

Discoaster bellus

Catinaster calyculus

Helicopontosphaera kamptn

Discoaster kugleri

Coccolitbus miopelagicus

, C'Q Sphenolitbus heteromorphus

ti'X Hellcopontospbaera ampltaperta

io*X Sphenolithus belemnos

21.0 -Triquetrorbabdulus

_e o Sphenolitbus 

i/e ciperoensis

Discoaster drugii

Discoaster deflandrei

Cvclicareolitbus abisectus

Dictyococcites bisectus

Cyclicargolithus floridanus

''o'o Sphenolitbus distentus

MO Spbenolitbus predistentus

34.5 -Helicopontosphaera

37.0 - reticulata 

10 r>

, _ Dtscoaster 

/-,"» barbadiensis

,t Reticulofenestra 

44.0 - , ... 

., . umbtltca

46.5 - Nannotetrina 

47.0 - quadrat a 

48.0 - . 

49 o O'scoasfer

,_', sublodoensis

Reticulofenestra hillae

Coccolithus formosus

Coccolitbus subdistichus

Istbmolitbus recurvus

Cbiasmolitbus oamaruensts

Discoaster saipanensis

Discoaster bifax

Coccolithus staurion

Cbiasmolitbus gigas

Discoaster strictus

Rhabdosphaera inflata

Discoasteroides kuepperi

- Discoaster lodoensis

c-i° 0 Tribracbiatus orthostylus

S7 e - D *scoaster 

' diastypus

^ ^ Discoaster 

' multiradiatus

Discoaster binodosus

Tribracbiatus contortus

Campy losphaera eodela

Cbiasmolitbus bidens

--'- Discoaster nobilis

z-f'n Discoaster mobleri

58 0 Heliolitbus kleinpellii

Fasciculitbus tympaniformis

. ' Cruciplacolitbus tenuis

)j

(m.y.) Age

Maestrichtian

Campanian

Santonian

Coniacian 86 

Turonian 91 - : 

Cenomanian

1 rt/1^ Albian

COST No. B-2 well 

(depth in feet)

ei 

eri

 3580-3730

 3790-4050

II 4080-4320

H 4500-4620

 4900-4910

 5000-5020

 1 5110-6010

 1 7300-7610

 

7900-8210 

8500-8810

1^ t

38
 STABLE 8. Preliminary age determinations of COST 

No. B-2 samples on the basis of calcareous nannofossils

[Samples below 8,810 feet were barren. Depths are in feet below 

Kelly Bushing. Calcareous nannofossil zones and subzones and estimated time relations are taken from Bukry (1975, fig. 3 and table 

2). Black bars indicate range of determinations for given sample 

depths.]

thina spp., Helicosphaera compacta, Isthmolithus recurvus, Lanternithus minutus, Neococcolithes dubius, Reticulofenestra hillae, R. reticu~ 

lata, R. cf. R. scissurus of Bramlette and Wilcoxon (1967), R. umbilica, Transversopontis 

obliquipons, and T. zigzag.

EOCENE 

(=-4,500 FEET TO =-4,910 FEET)

Two samples (from 4,500 to 4,530 ft and 

4,590 to 4,620 ft) contain calcareous sediments 

of middle to late Eocene age. The assemblage 

identified in these samples is characteristic of 

the Reticulofenestra umbilica Zone of Bukry 

(1973, 1975): Chiasmolithus grandis, C. solitus, C. titus, Coccolithus eopelagicus, C. pelagicus, Cyclicargolithus fioridanus, Cyclococcolithina formosa, Discoaster barbadiensis, Helicosphaera lophota, H. semimdum, Neococcolithes dubius, Reticulofenestra hillae, R. reticulata, R. samodurovi, R. umbilica, Sphenolithus moriformis, and Zygrhablithus bijugatus.

The sample from 4,900 to 4,910 feet, also 

calcareous, yielded an assemblage of early to 

middle Eocene age; it is placed in the Discoaster lodensis Zone and Discoasteroides 

kuepperi Subzone of Bukry (1973, 1975): 

Blackites creber, Campylosphaera dela, Chiasmolithus grandis, Coccolithus crassus (abundant), C. pelagicus, Cyclococcolithina kingii, 

Discoaster lodoensis, D. binodosus, Discoasteroides kuepperi, Helicosphaera seminulum, Lophodolithus mochlophorus, L. nascens, Markalius 

inversus, Marthasterites tribrachiatus, Neococcolithes dubius, N. protenus, Prinsius bisulcus, 

Sphenolithus radians, Transversopontis obliquipons, and T. pulcher.

EOCENE THROUGH PALEOCENE 

(=-5,000 FEET TO =-5,020 FEET)

The interval bounded by the samples from 

5,000-5,010 feet and from 5,010-5,020 feet is 

composed of calcareous sediments of earliest 

Eocene to latest Paleocene age. On the basis of 

the following assemblage, these strata are 

placed in the Discoaster multiradiatus and Discoaster diastypus Zones of Bukry (1973,1975): 

Campylosphaera dela, Cepekiella lumina, Chiasmolithus solitus, Coccolithus jugatus of Proto 

Decima and others (1975), C. pelagicus, C. 

petrinus, Cyclococcolithina formosa, C. gammation, Discoaster barbadiensis, D. binodosus, D. 

distinctus, D. elegans, D.-lenticularis, D. multiradiatus, Discoasteroides kuepperi, Ellipsolithus distichus, Fasciculithus involutus, Helicosphaera lophota, H. seminulum, Markalius inversus, Neococcolithes dubius, Transversopontis fimbriatus, T. obliquipons, T. pulcher, and 

Zygrhablithus bijugatus.

The Eocene section in the COST No. B-2 

well, is considered to be 1,000 feet or more 

thick. Future, more detailed investigations may 

reveal the existence of a fairly complete record 

of the Eocene in this well.

CRETACEOUS 

(FROM =-5,110 FEET)

The Tertiary-Upper Cretaceous boundary is 

at approximately 5,110 feet in this well. In 

contrast to the carbonate rocks of the Paleogene sequence, the sample from 5,110 to 5,140 

feet is composed of terrigenous clastic sediments containing rare but well-preserved calcareous nannofossils of Campanian Age. Other 

fossiliferous strata from the Cretaceous in this 

well are appreciably more calcareous. In general, however, these older rocks have a terrigenous aspect, and much of the section is of 

nonmarine origin.

The interval from 5,390 feet to 6,010 feet 

(samples from 5,390-5,400 feet, 5,510-5,520 

feet, 5,800-5,810 feet, and 6,000-6,010 feet) 

contains the following assemblage, considered 

to represent the Campanian (Broinsonia parca, 

a Campanian and early Maestrichtian marker, 

was observed in samples from 5,800 to 5,810 

feet and 6,000 to 6,010 feet.) : Ahmuellerella 

octoradiata, Arkhangelskiella cymbiformis, 

Biscutum blackii, Braarudosphaera bigelowii, 

Broinsonia parca, Chiastozygus amphipons, C. 

plicatus, Corollithion achylosum, C. signum, 

Cretarhabdus conicus, C. crenulatus, Cribrosphaerella ehrenbergii, Eiffellithus eximius, E. 

turriseiffeli, Gartnerago costatum, Kamptnerius magnificus, K. percivalii, K. punctatus, 

Lucianorhabdus cayeuxii, Manivitella pemmatoidea, Microrhabdulus decoratus, Micula staurophora, Parhabdolithus embergeri, Percivalia 

porosa, Podorhabdus orbiculofenestrus, Predis39
cosphaera cretacea, P. spinosa, Tetralithus 

obscurus, Vagalapilla elliptica, V. imbricata, V. 

matalosa, Watznaueria barnesae, Zygodiscus 

acanthus, Z. compactus, and Z. diplogrammus.

The beds from 6,010 feet to 7,300 feet were 

examined at 300-foot intervals and were found 

to be barren of calcareous nannofossils.

Strata thought to be of Turonian Age are 

present in the interval between 7,300 feet and 

7,610 feet (samples from 7,300-7,310 feet and 

7,600-7,610 feet). Kamptnerius magnificus, Lucianorhabdus cayeuxi, and Microrhabdulus 

decoratus are not recorded from below 6,010 

feet. Eiffellithus eximius, Gartnerago costatum, 

and Micula staurophora are not formed below 

the sample from 7,300 to 7,310 feet, and 

Ahmuellerella octoradiata and Gartnerago segmentatum are not found below the sample 

from 7,600 to 7,610 feet. The following assemblage was identified in this interval: 

Ahmuellerella octoradiata, Arkhangelskiella 

cymbiformis, Braarudosphaera bigelowii, Chiastozygus amphipons, C. plicatus, Corollithion 

signum, Cretarhabdus conicus, C. crenulatus, 

Cribrosphaerella ehrenbergii, Eiffellithus eximus, E. turriseiffeli, Gartnerago costatum, G. 

segmentatum, Lithastrinus ftoralis, Manivitella 

pemmatoidea, Micula stan-rophora, Prediscosphaera cretacea, Tetralithus obscurus, Vagalapilla elliptica, Watznaueria barnesae, Zygodiscus acanthus, Z. compactus, Z. diplogrammus.

Sediments from the interval bounded by samples from 7,900 to 7,910 feet and 8,200 to 8,210 

feet contain a calcareous nannofossil assemblage characterized by long-ranging species.

Many species that evolved during the Turonian 

and were recorded in higher samples from the 

COST No. B-2 well are absent. The presence 

of Prediscosphaera cretacea indicates that 

these sediments are no older than Albian, and 

they are tentatively assigned an age of Cenomanian and Albian: Biscutum blackii, Chiastozygus amphipons, C. plicatus, Corollithion 

achylosum, C. signum, Cretarhabdus conicus, 

C. crenulatus, Eiffellithus turriseiffeli, Lithastrinus floralis, Manivitella pemmatoidea, Parhabdolithus angustus, P. asper, P. embergeri, 

Podorhabdus orbiculofenestrus, Prediscosphaera cretacea, Watznaueria barnesae, Zygodiscus acanthus, Z. compactus, and Z. diplogrammus.

Samples from 8,500 to 8,510 feet and 8,800 

to 8,810 feet also contain many long-ranging 

species. Prediscosphaera cretacea is present, a 

species restricted to Albian and younger strata, 

and the occurrence in these two samples of 

Rucinolithus irregularis, a species recorded 

only from the Albian and Aptian, points to an 

Albian Age for the sediments of this interval: 

Chiastozygus plicatus, Corollithion achylosum, 

C. signum, Cretarhabdus conicus, Eiffellithus 

turriseiffeli, Lithastrinus ftoralis, Manivitella 

pemmatoidea, Markalius circumradiatus, Parhabdalithus embergeri, Prediscosphaera cretacea, Rucinolithus irregularis, Vagalapilla matalosa, Watznaueria barnesae, and Zygodiscus 

diplogrammus.

The strata from depths below 8,810 feet, 

examined at 300-foot intervals, were found to 

be barren of calcareous nannofossils.

40
Palynomorph Biostratigraphy

By R. A. Scott and E. I. Robbins

Brenner (1963), Wolfe and Pakiser (1971), 

Sirkin (1974), Bobbins and others (1975), 

Wolfe (1976), and Doyle and Robbins (in 

press) have reviewed the development of a 

palynological zonation for the sequence of both 

exposed and subsurface Cretaceous beds along 

the Atlantic Coastal Plain from South Carolina 

to Rhode Island. These informal zonations have 

been established primarily for the Barremian 

and younger strata of the emerged Coastal 

Plain. The striking record of the entry and 

evolution of the angiospermous pollen in Cretaceous strata forms the basis for clarifying 

many stratigraphic relationships among beds 

that have been difficult to separate on litho>- 

logic grounds.

Some evidence about the composition of 

earlier Cretaceous (Neocomian) floras of the 

region is furnished by spore assemblages from 

lower depths, for example, below 5,401 feet in 

the E. G. Taylor well (Accomack County, Va.) 

and below 5,612 feet in the J. D. Betha'rds well 

(Worcester County, Md.) (see Doyle and Robbins, in press), as well as both spore and, dino^- 

flagellate assemblages of Hauterivian to Berriasian Age in DSDP hole 105 (Habib, 1976, 

and in press). Palynological evaluations at the 

Cretaceous-Jurassic boundary have been made 

elsewhere in North America (Pocock, 1962; 

Williams, 1974; Norris and others, 1975) and in 

Europe (Norris, 1970).

The purposes of this preliminary report are 

threefold: (1) to discuss the palynomorph 

biostratigraphy of sediments present in the 

COST No. B-2 well; (2) to determine Whether 

the hole penetrated beds older than Cretaceous; 

and (3) to present a broad-based paleoecological framework. Fifty-four samples were selected at intervals of approximately 300 feet. 

At least a few palynomorphs were present in 

almost every sample, although the number of

forms and their preservational quality varied 

greatly among the samples. Although the cuttings were washed carefully, there is evidence 

of at least slight contamination by rare dicotyledonous pollen grains in deep levels of the well.

RESULTS

Pollen from the interval from 5,200 to 5,230 

feet is regarded as Eocene in age (Norman 

Fredericksen, oral commun., 1976). Furthermore, F. E. May (written commun., 1976) identified the following Tertiary dinoflagellates: 

Deflandrea phosphoritica, Hystrichokolpoma 

rigaudae, Thalassiphora delicata, T. pelagica, 

Wetzeliella clathrata, and W. symmetrica. The 

age of the sample would appear to be Eocene 

on the basis of the presence of the two species 

of Wetzeliella. However, the interval could 

range as low as early Maestrichtian on the 

basis of the presence of the triaperturate 

angiospermous pollen C3B-3 (Wolfe, 1976, pi. 

3) and MPD-1 (Wolfe, 1976, pi. 4).

The interval from 5,410 to 5,830 feet contains pollen indicative of a Maestrichtian to 

Santonian Age, as shown by the following 

Normapolles genera: Plicapollis sp., Praebasopollis sp., and Pseudoplicwpollis sp. On the 

basis of the presence of the dinoflagellate cysts 

Paleohystrichophora infusorioides and Phoberocysta ceratioides, a Campanian or Santonian 

Age is confirmed (F. E. May, written commun., 

1976). F. E. May located the Tertiary-Cretaceous boundary, on the basis of dinoflagellates, 

at from 5,230 to 5,410 feet.

From 6,120 to 7,330 feet, Zone V (Santonian 

to Turonian?) pollen is recognized on the basis 

of the association of Group 13, Krutzsch 

(1957), Pseudoplicwpollis sp. and Triatriopollenites sp.

Zone IV pollen, which is present from 7,620 

to 7,630 feet (lower Turonian? to middle

41
Cenomanian), is recognized on the basis of the 

occurrence of Complexiopollis, Tricolpites vulgaris, and many unidentified tricolporates.

Zone III is identified in the interval from 

7,920 to 7,930 feet on the'basis of the association of Straitopollis sp. B of Doyle and Robbins 

(in press), Tricolporoidites bohemicus, and 

"Tricolporopollenites" distinctus. This zone has 

been dated as early Cenomanian.

From 8,220 to 8,840 feet, the association is 

suggestive of Subzone II C (upper Albian), as 

indicated by the association of Rugubivesiculites rugosus, Granulatisporites daily 1(1), 

Lycopodiumsporites triangular us, and "Tricolporopollenites" distinctus. The sample is too 

contaminated by Late Cretaceous and Miocene 

pollen to yield a confident correlation.

In the interval from 8,520 to 8,530 feet, the 

association of Rugubivesiculites reductus, R. 

rugosus, Cicatricosisporites subrotundus, and 

Taurocusporites spackmani with the angiosperm species Clavatipollenites tenellis, "Peromonolites" peroreticulatus, Tricolporoidites 

subtilis, and "Tricolporopollenites" triangulus 

suggests that the sample is late Albian in age 

(Subzone II C). This assemblage also includes 

dinoflagellates of this age.

The sample from 8,820 to 8,830 feet contains 

the following Subzone II B (uppei* to middle 

Albian) species of angiosperms: Clavatipollenites tenellis, aff. "Foveotricolpites" concinnus, cf. Liliacidites sp. D of Doyle and Robbins 

(in press), two unidentified species of Liliacidites, "Retitricolpites" prosimilis, "R." vermimurus, and Tricolpites georgensis.

Varying quantities of pollen and spores in 

the interval from 9,120 to 11,890 feet can be 

correlated with Zone I (lower Albian to Barremian). Important species include: Cicatricosisporites aralica, C. dorogensis, Concavissimisporites variverrucatus, Gleicheniidites 

apilobatus, Klukisporites pseudoreticulatus, 

Parvisaccites amplus, as well as the angiosperms Clavatipollenites hugesii, aff. C. tenellis, and Retimoncolpites dividuus.

Dinoflagellates occur intermittently in the 

interval from 9,120 to 11,890 feet; for example, 

at 11,560 to 11,590 feet, 11,260 to 11,290 feet, 

10,020 to 10,030 feet, and 9,720 to 9,730 feet. 

Study of the dinoflagellate assemblages will undoubtedly provide a record of fluctuating marine incursions. F. E. May (written commun., 

1976) believes that the dinoflagellates in the

interval 11,260 to 11,290 feet are of Barremian 

Age.

The intervals between 12,160 to 16,030 feet 

contain a typical pre-Zone I assemblage (preBarremian). Some species identified from the 

interval include: Parvisaccites sp., Podocarpidites potomacensis, Vitreisporites pallidus, Appendicisporites sp., Deltoidospora sp., Leptolepidites sp., Lycopodiacidites sp., abundant 

Pilosisporites trichopapillosus, Taurocusporites 

sp., Todisporites sp., and Trilobosporites sp.

In the deepest sample, from 16,020 to 16,030 

feet, the following taxa were recognized: 

Alisporites sp., Podocarpidites sp., Classopollis 

sp., Ephedripites multicostatus, Eucommiidites 

troedssonii, Cicatricosisporites sp., and Concavissimisporites sp.

Although the presence of Appendicisporites 

sp. suggests an Early Cretaceous age for these 

basal samples, the occurrence of Ephedripites 

multicostatus in the basal sample allows a correlation with the Ephedripites multicostatus 

Zone (Hauterivian to Berriasian) of Habib 

(1976, and in press) from DSDP hole 105.

The presence of megaspores in several 

samples, including the lowest one (16,020- 

16,030 feet), reinforces an Early Cretaceous 

age for the base. The megaspores have been 

examined by R. H. Tschudy (oral commun., 

1976), who found no taxa that have been recognized in North America below the upper Lower 

Cretaceous; little information is available from 

lower Lower Cretaceous beds. None of the 

megaspores described from the Upper Jurassic 

of Greenland (Harris, 1935) or of England 

(Murray, 1939) was present among forms 

found in this well.

Thus, there appears to be only a slight possibility, implicit in the incompleteness of the 

dating of assemblages from elsewhere in North 

America and northern Europe, that Jurassic 

beds are present in the COST No. B-2 well.

PALEOECOLOGY

Study of the palynomorphs, as well as plant 

fragments, algae and fungi, the type of sapropel, and the presence of pyrite crystals in 

samples prepared for sapropel studies (see section "Color Alteration of Visible Organic Matter") has also yielded paleoenvironmental 

information, indicating the following environmental conditions: 610 to 3,790 feet, alternating nearshore marine, brackish, and 

nonmarine; 3,790 to 4,880 feet, open-marine;

42
4,880 to 6,430 feet, nearshore; 6,430 to 8,530 

feet, alternating nonmarine and marine. In the 

interval from 8,530 to 11,290 feet, the organic 

matter is largely nonmarine and primarily oxidized or degraded by bacteria. From 13,330 

feet to the bottom of the well, the organic 

matter is largely terrestrially derived.

CONCLUSIONS

In summary, palynomorphs were obtained 

from most of the cuttings studied between 

1,030 and 16,030 feet from the COST No. B-2 

well. The Tertiary-Cretaceous boundary, determined on the basis of dinoflagellates, is 

found between 5,230 and 5,410 feet. Late 

Cretaceous dicotyledonous pollen, equivalent to

Zones V, IV, and III in the Atlantic Coastal 

Plain informal pollen zonation, is present between 5,410 and 7,930 feet in the COST No. B2 well. An Early Cretaceous spore assemblage 

equivalent to Subzones II C, II B, Zone I, as well 

as the Ephedripites multicostatus Zone of Habib (1976, and in press) extends to the lowest 

level sampled, 16,020 to 16,030 feet. Early Cretaceous megaspores are present in the lowest 

samples, including the lowest one examined. 

Evidence at hand indicates that the COST No. 

B-2 well bottoms in Lower Cretaceous beds 

and thus penetrates at least 9,000 feet of 

Cretaceous sediments. However, the possibility 

that some Upper Jurassic is present in the 

basal samples cannot be excluded.

43
Geothermal Gradients

By E. I. Robbins

Present-day subsurface temperatures can be 

used to give an approximate idea of the depth 

range of maximum hydrocarbon generation 

(liquid petroleum window) in a basin. This can 

be particularly useful when other studies are 

performed to determine whether the modern 

temperatures are the highest to which the section has been subjected.

For the COST No. B-2 well, 29 geothermal 

values have been plotted (fig. 9) using approximate equilibrium temperatures calculated from 

the five available temperature logs. A linear 

regression was completed using these points; 

it shows a systematic increase in temperature 

with depth (correlation coefficient = 0.98). The 

geothermal gradient is calculated to be 1.3°F/ 

100 ft with a surface intercept of 75.7°F. A 

geothermal gradient of 1.3°F/100 ft is rather 

typical for basins around the North Atlantic 

Ocean (table 9). An alternative method of calculating geothermal gradients, by using the 

present-day mean annual surface temperature 

(52°F) and the bottom-hole temperature, 

yields a thermal gradient of 1.5°F/100 ft 

(Smith and others, 1976).

The liquid petroleum window is based largely 

on empirical observation and generally is considered to have a lower limit of about 150°F 

and an upper limit of 270° to 300°F (Pusey, 

1973; Harrison, 1976). The upper temperature 

limit may be significantly higher if heating 

times are short. Using the present geothermal 

gradient, the liquid petroleum window (fig. 9) 

would be expected to occur between 5,700 and 

17,000 feet, provided these temperatures are 

maintained over a significant period of time. 

Work on vitrinite reflectance, visual analysis 

of color alteration of organic matter, and organic geochemistry all suggest that similar or 

slightly lower geothermal gradients may have 

prevailed in the past. However, most reconstructions of the geologic history of the area 

(Bott, 1971; Sleep, 1971, Falvey, 1974) would 

predict considerably higher geothermal gradients in the past, particularly during Triassic 

and Jurassic rifting events. Thus, some conflict remains between the direct thermal analyses of the COST No. B-2 well sediments and 

both present and inferred past geothermal history. Certainly, the thick sedimentary section 

that underlies the rocks penetrated by the 

COST No. B-2 well may have been influenced 

by higher geo'thermal gradients.

TABLE 9. Circum-Atlantic offshore geothermal gradients

Basin Gradient

("F/l&O ft) Reference

Scotian Shelf basin __ 

Southern North Sea __ 

Baltimore Canyon basin 

Niger Delta shelf ______

South Pass, La. ________

Offshore Louisiana __.

1.2 Robbins and Rhodehamel, 1976.

1.7 Harper, 1971.

1.3 This paper.

1.4 Nwachukwu, 1976.

1.2 Pusey, 1973.

1.3 Jam and others, 1969.

44
TEMPERATURE,IN DEGREES FAHRENHEIT

o o o o

>o 00 O (N

2.0

4.0

6.0

8.0

:- 10

o.

LU 

O

12

14

16

18

FIGURE 9. Geothermal gradient for COST No. B-2 well. Data points are resting temperatures derived from five avai
Organic Geochemistry

By G. E. Claypool, C. M. Lubeck, J. P. Baysinger, and T. G. Ging

Thirty-four samples of unwashed cuttings 

have been analyzed by combustion and thermal 

analysis/pyrolysis-FID techniques to evaluate 

petroleum source-rock potential. In addition, 

six of the samples were analyzed for light hydrocarbon (d-C7 ) content, and five samples of 

washed, handpicked cuttings were analyzed for 

extractable hydrocarbons by solvent extraction, 

column chromatography, and gas chromatography. The thermal analysis technique was 

the same as that described by Claypool and 

Reed (1976), except that the rate of heating 

was 104°F/min (40°C/min) instead of 

82°F/min (28°C/min). The flame-ionization 

response was converted to an equivalent weight 

of hydrocarbons by using an empirical calibration based on secondary standards analyzed by 

Fisher assay. The organic carbon and solventextraction techniques were adopted from those 

described by Baker and Claypool (1970).

The following criteria are used in this section to evaluate petroleum source-rock potential:

1. Organic richness Sedimentary rocks must 

contain a sufficient quantity of organic 

matter that can be or that,has been converted to petroleum hydrocarbons. Measurements used to indicate sufficient 

organic richness for petroleum sourcerock potential are either (a) -pyrolytic oil 

yield in excess of about 0.2 to 0.3 percent; 

or (b) extractable hydrocarbon concentrations in excess of about 100 to 500 

ppm.

2. Maturity The conversion of organic matter to petroleum hydrocarbons takes place 

by temperature-dependent chemical reactions. Sedimentary rocks that are rich in 

organic matter and in which the petroleum-generating reactions have not advanced to a degree sufficient to expect 

expulsion and accumulation of petroleum are called immature. The principal criteria used to determine the extent 

of petroleum-generating reactions are the 

molecular composition and the relative 

concentration of indigenous extractable 

hydrocarbons. When the extractable hydrocarbons are chemically indistinguishable from petroleum and are present at 

levels in excess of about 1 to 2 percent 

of the total organic carbon, the rock is 

mature. When a rock is known to be 

capable of generating petroleum hydrocarbons (for example, by pyrolysis) but 

contains a relatively low concentration of 

largely biochemically derived hydrocarbons, then the hydrocarbon-generating 

reactions are not sufficiently advanced, 

and the rock is immature. 

By using these criteria of maturity and richness in organic matter, we can distinguish the 

following categories of petroleum source rocks: 

Potential source rock A sedimentary rock 

that is rich in organic matter and that is 

immature. This is a potential source rock 

in the sense that hydrocarbon generation 

may have taken place in laterally equivalent strata, if higher temperatures prevailed (for example, deeper burial); however, it is not practical to wait for the 

sedimentary section in question to realize 

its hydrocarbon-generating potential. 

Possible source rock A sedimentary rock that 

is rich in organic matter and that is mature. This rock has realized its potential 

for generating hydrocarbons (that is, it 

contains petroleumlike hydrocarbons). 

Many other chemical and physical measurements relate to the interpretation of richness in

46
organic matter and, especially, maturity. However, these properties or observations are indirectly related to petroleum occurrence or 

generation. For purposes of petroleum sourcerock evaluation, the direct measurement of 

the approximate degree of completion of hydrocarbon-generating reactions (where possible) is preferable to an inference based on 

indirectly related properties.

RESULTS AND CONCLUSIONS

Although potential source rocks are present 

in the lower part of the COST No. B-2 well, 

the presence of fully mature oil source rocks 

was not confirmed. The organic matter in all 

samples analyzed appears to be immature in 

greater or lesser degree with respect to the 

degree of liquid-petroleum-hydrocarbon generation required for expulsion and economic 

occurrence of petroleum. This conclusion is 

based primarily on the nonpetroleum characteristics of the saturated-hydrocarbons, that is,

the predominance of n-paraffins containing an 

odd number of carbon atoms (nC27 to nC.,i) 

in the five samples analyzed. Additional support for this conclusion is provided by the 

relatively low temperatures of maximum 

pyrolysis yield, indicating coal rank in the 

subbituminous to high-volatile bituminous 

range. Although the deepest rocks that are 

rich in organic matter appear not to be fully 

mature, the hydrocarbon-generating reactions 

are definitely in progress. Moreover, the rocks 

below 14,000 feet in this well contain such 

small quantities of organic matter that geochemical methods for evaluation of maturity 

are of questionable applicability. If rocks of 

sufficient organic richness were present, they 

might well be fully mature at, or just below, 

the bottom of the well.

The results of the combustion and thermal 

analysis/pyrolysis FID measurements are 

given in table 10. The trend of increasing temperature of maximum pyrolysis yield as a funcTABLE 10. Organic content of sediments from the COSTNo. B-2 well, obtained by combustion and thermal analysis/pyrolysis

Thermal analysis

Depth interval (feet)

Organic

carbon

(weight

percent)

Pyrolytic 

hydrocarbon

yield 

(weight 

percent)

Oil

content 

(ppm)

Temperature

maximum

yield

1,120- 1,150 _________ __________ 0.1 0.04 54 835 446

1,300- 1,330 __________________________ .2 .09 81 864 462

1,480- 1,510 _________________________ .1 .04 53 873 467

1,660- 1,690 ______________ _______ <.l .01 20 810 432

2,050- 2,080 ______________________ .3 .13 67 864 462

2,330- 2,350 _______________________ <.l .02 37 849 454

2,330- 2,350 _____________ __ __ .5 .21 85 876 469

3,040- 3,070 ____ _ ____ _ 1.4 .53 320 864 462

3,580- 3,610 _ _ _________ 2.4 1.5 200 867 464

3,850- 3,880 _____ _ 2.8 1.9 180 896 480

4,110- 4,140 __ __ _ .9 .48 100 871 466

4,690- 4,700 ____ _____ 1.0 .41 300 871 466

4,990- 5,000 ______________________ .9 .05 33 858 459

5,200- 5,300 _______________________ .3 .12 43 860 460

5,410- 5,420 .5 .23 46 871 466

6,720- 6,730 ______________________. .2 .10 100 878 470

8,220- 8,240 ______________________ 2.1 1.8 9,600 876 469

8,850- 8,860 _______________________ .5 .021 30 878 470

9,720- 9,730 _______________________ .6 .30 240 878 470

10,870-10,910 _______________________ 2.2 .50 520 842 450

11,260-11,290 ________________________ 2.6 2.1 1,300 867 464

12,160-12,190 ______________________ 6.0 2.9 3,100 874 468

12,750-12,760 _______________________ 2.0 .30 320 860 460

13,020-13,030 _______________________ 11.5 5.1 5,600 907 486

13,020-13,030 (Black shale) _____________ 6.0 1.6 1,500 891 477

13,410-13,420 _______________________ 2.0 .30 260 887 475

13,920-13,930 _______________________ 1.1 .17 66 900 482

14,520-14,530 _______________________ <.l .03 60 878 470

14,820-14,830 _______________________ .6 .04 86 910 488

15,120-15,130 _______________________ <.l .11 130 896 480

15,420-15,430 _______________________ <.l .04 94 882 472

15,720-15.730 _______________________ <.l .03 72 896 480

15,840-15,850 _______________________ .3 .01 10 896 480

15,900-16.030 ______________________ .2 __ __

16.020-16030 ________________________ <.l .10 110 907 486

47
TEMPERATURE MAXIMUM YIELD, IN DEGREES CELSIUS

§ 8

LU 

LU

1 10

QLU 

Q

12

14

16

440

I 

450

I 

460

I 

470 480

I 

490

\

\

x . \

\

\

\

\ \

\ \

\ \

\

Hand-picked

black shale V

\

\

\

\

XX X

\

\

500

Immature Transitional Possibly mature

FIGURE 10. Temperature of maximum pyrolysis yield as a function of depth.

48
tion of depth is shown in figure 10 for the 

COST No. B-2 well; it is superimposed on the 

tentative calibration based on analysis of standard coals, shown in figure 11.

Samples from depth intervals of about 3,000 

to 4,000 feet and about 8,000 to 14,000 feet are 

relatively rich in organic matter (greater than 

2.0 percent organic carbon). Samples from the 

shallowest interval (3,040-3,070 feet and 

3,580-3,610 feet) contain relatively low 

amounts of hydrocarbons (80 to 78 ppm, respectively) and have a marked odd carbonnumber predominance in the normal paraffins. 

These samples also show a relatively high 

conversion of organic matter to hydrocarbons 

upon pyrolysis (0.5 and 1.5 percent, where 0.3 

percent is about the minimum value for rocks 

considered to be potential source rocks).

The samples at 8,220 to 8,240 feet and those 

in the range of 10,000 to 14,000 feet contain 

large amounts of volatile or thermally extractable organic matter, in addition to high contents of total organic carbon. In the sample 

from 8,220 to 8,240 feet, the material appears 

to be nonindigenous (oil staining or possible 

contamination) because the quantity of volatile 

organic matter is out of proportion to the total 

organic carbon content of the sample. However, 

the samples analyzed from 10,000 to 14,000 

feet, especially the sample from 12,160 to 

12,190 feet, contain high concentrations of apparently indigenous, solvent-extractable organic matter. The high concentrations of hydrocarbons are probably related to abundant 

coaly material in this part of the section, and 

the richness-in-organic-matter criteria for petroleum source-rock evaluation of shales are 

not strictly applicable.

More detailed analyses were performed to 

determine whether the section rich in organic

matter between approximately 10,800 and 

14,000 feet contains an assemblage of indigenous, petroleumlike hydrocarbons generated 

from the solid organic matter (that is, to determine whether the section is mature with 

respect to liquid-petroleum hydrocarbon generation). The results of the solvent-extraction 

analyses are summarized in table 11. The 

sample from 12,160 to 12,190 feet has 2,680 

ppm hydrocarbons and 6.0 percent organic 

carbon for a hydrocarbon-to-organic-carbon 

ratio of 4.5 percent. The other two samples 

from the deeper part of the section have hydrocarbon-to^organic-carbon ratios of 1.7 percent 

(11,260-11,290 feet) and 1.3 percent (15,900- 

16,030 feet). These ratios are in contrast to 

values of 0.6 and 0.3 percent for the shallower 

samples (3,040-3,070 feet and 3,580-3,510 feet, 

respectively). Ratios in excess of 1 percent 

usually suggest that hydrocarbon generation 

has taken place. However, the more important 

question is whether or not this process is sufficiently advanced in the sections of this well 

that are rich in organic matter for expulsion 

and accumulation of liquid petroleum to have 

taken place.

The results of detailed analyses of the 

saturated hydrocarbons by gas chromatography are summarized in figures 12-16. The 

tendency for the odd-numbered n-paraffins to 

predominate over the neighboring evennumbered n-paraffins is summarized by the 

carbon preference index (CPI). A definite 

trend of CPI values approaches 1 as depth in 

the hole increases. This trend also indicates 

that some degree of hydrocarbon generation 

has taken place. However, the deepest samples 

analyzed that contain sufficient organic matter 

to be considered a potential petroleum source 

rock (12,160-12,190 feet, fig. 15) have a CPI

TABLE 11. Summary of chloroform extraction-yields, column chromatographic separation of Cia+ hydrocarbon fractions, and estimate of carbon preference index (CPI) by gas chromatography from COST No. B-2 well samples

Extractable hydrocarbons

Depth interval 

(feet)

3,040- 3,070 ___

3,580- 3,610 __ _____ .

11,260-11,290 ___ ______

12,160-12,190 ____ __

15,900-16,030 __ _.

CHCls-soluble 

bitumen 

(ppm)

. ____ _ 311

272

893

. ______ 5,747

77

Saturated 

(heptane eluate) 

(ppm)

21 

30

115 

710 

9

Aromatic 

(benzene eluate) 

(ppm)

60 

48 

315 

1,970 

16

Total 

(sum) 

(ppm)

81

78 

430 

2,680 

25

CPP

3.4 

-3.4 

1.5 

1.2 

1.2

Hydrocarbons 

total organic 

C

0.6 

0.3

1.7 

4.5 

1.2

nCa+nCsr+nC29 + nCsi 

nCaa + nCas + nCso + nCs2

+

nC28 + nCsi

nC24 + nCaH- nCas+nCa

49
Coal Rank

PEAT

LIGNITE

SUBBITUMINOUS

HIGHVOLATILE

BITUMINOUS

MEDIUM

VOLATILE

LOW

VOLATILE

BITUMINOUS

SEMIANTHRACITE

ANTHRACITE

Vitrinite

Reflectance

(Ro percent)

0.25-

0.3 -

0.4 -

0.5 -

0.7 -

1.0 -

1 "5 

i . «?

2.0 -

2.5 -

COST NO. B-2 

WELL SAMPLES

EXPLANATION 

Standard coal series analysis

Cost No. B-2 well profile

HYDROCARBON PRODUCTION (COAL

MAXIMUM LIQUID PETROLEUM PRODU

- MAXIMUM GAS PRODUCT

400 500 

TEMPERATURE, IN DEGREES CELSIUS

600 

FIGURE 11. Calibration of temperature of maximum pyrolysis yield with respect to coal rank, based on analysis of sta

Position of COST No. B-2 samples determined by range of maximum pyrolysis yields, temperatures, and averag

tance, reported by Superior Oil (written commun., 1976).
Carbon number

TEMPERATURE

FIGURE 12. Gas-chromatographic analysis of saturated hydrocarbons, COST 

No. B-2 well, sample from 3,040 to 3,070 feet. Analysis on 20-mm X 

1.8-m columns packed with 3.0-percent GCSE-30 on 100-120-mesh Gas 

Chrom Q; the flow was 40mL/min. Column temperature was 80° C at 

injection and was programmed to rise 12°C/min for 10 min, then 10°C/ 

min for 12 min to a final temperature of 320° C.

Carbon number

TEMPERATURE *- 

TIME »-

FIGURE 13. Gas-chromatographic analysis of saturated hydrocarbons, COST 

No. B-2 well, sample from 3,580 to 3,610 feet Conditions same as analysis shown in figure 12.

51
Carbon number

TEMPERATURE

FIGURE 14. Gas-chromatographic analysis of saturated hydrocarbons, COST 

No. B-2 well, sample from 11,260 to 11,290 feet. Conditions same as 

analysis shown in figure 12.

Corbon number

24 26 30 32 34 36

TEMPERATURE 

TIME 

FIGURE 15. Gas-chromatographic analysis of saturated hydrocarbons, COST 

No. B-2 well, sample from 12,160 to 12,190 feet. Conditions same as 

analysis shown in figure 12.

52
27 ^Carbon number

TEMPERATURE 

TIME »

FIGURE 16. Gas-chromatographic analysis of saturated hydrocarbons, COST 

No. B-2 well, sample from 15,900 to 16,030 feet. Conditions same as in 

the analysis shown in figure 12.

value of 1.5; pristane is the most abundant 

single compound in the mixture. These are still 

the chemical characteristics of subbituminous 

coals (Brooks and Smith, 1967), whereas the 

principal phase of oil formation takes place at 

the high-volatile bituminous stage (Vassoye^ 

vich and others, 1970). At this latter stage, the 

mixture of saturated hydrocarbons resembles 

mature petroleum in having little or no oddcarbon-predominant n-paraffins and much 

smaller predominance of pristane in the total 

mixture.

Another analysis was performed on pieces 

of black shale handpicked from the interval 

13,020 to 13,030 feet. The sample was heated 

in two stages from room temperature to 

680°F (360°C) and then from room temperature to 1,382°F (750°C) and the volatile and 

pyrolysis products produced during the two 

separate heating periods were analyzed by gas 

chromatography. Two different hydrocarbon 

mixtures are evident, indicating that the volatile organic matter was not produced by 

thermal alteration of the solid organic matter. 

In addition, the gas-chromatographic analysis 

of the pyrolysis products indicates liquid-hydrocarbon-generating potential (as opposed to 

gas only).

Six samples from the interval 8,850 to 15,850

feet were analyzed for light hydrocarbons in 

the headspace gas of a blender containing the 

cuttings and distilled water at 198°F (92°C). 

The results are shown in table 12. The cyclic 

isomers in the C6 to C7 range are predominant, 

which is consistent with immaturity. The 

measured quantity of Ci to C7 hydrocarbons 

was in the range of 10"6 to 10~5 grams per gram 

of organic carbon. In mature petroleum-generating sediments, the corresponding range is 

10"3 to 10~2 . However, these samples were 

bagged cuttings that had been opened prior to 

analysis so that the quantities of gaseous and 

gasoline-range hydrocarbons measured are 

minimum values. Sample 13,410 to 13,420 feet 

had the highest content of Ci to C7 hydrocarbons and a significant proportion (51 volume 

percent) of permanent gases (methane, ethane, 

propane). As these samples were not collected 

and handled in a manner that would insure retention of dissolved or absorbed gases, this gas 

was probably released from the rock when the 

cuttings were disaggregated in the blender.

Although experimental evidence suggests 

that virtually the same temperatures are needed 

for gas- or liquid-hydrocarbon formation, an 

extensive body of empirical evidence shows that 

wet or dry gas is present and may form before 

crude oil, probably at temperatures starting

53
TABLE 12. Ci to C7 hydrocarbon analyses of selected samples from the COST No. B-2 well

[Values in volume percent of Ci to CT hydrocarbons normalized to 100 percent]

Hydrocarbons

___________________Depth interval (in feet)____________________ 

8,850- 10,870- f2,760^13,410- 14,820- 16,840- 

8,860 10,910 12,760 13,420 14,830 15,850

Methane+ethane ______________ 0.0 2.6 2.8

Propane _____________________ .0 9.5 24.9

Isobutane ___ - _____ _______ . .0 5.2 9.1

n-Butane ____________________ .0 6.2 2.7

Isopentane __ - _______________ .0 8.5 12.9

n-Pentane ___ __________ .0 4.8 10.7

2.2-Dimethybutane __________ .0 .0 .0

Cyclopentane __ _ __ _____ __ _ .0 1.2 1.8

2.3-Dimethylbutane _ _ _ __ _ ______ .0 .6 .4

2-Methylpentane _______________ .0 6.5 3.5

3-Methylpentane ______________ .0 2.6 2.3

n-Hexane __________ _ _________ .0 1.9 2.3

Methylcyclopentane _____________ .0 9.3 6.8

2,2-Dimethylpentane ____________ .0 .0 .0

Benzene _ ___ _________ __________ 55.0 6.6 .9

2,4-Dimethylpentane ___________ __ .0 .0 .0

2,2,3-Trimethylbutane ____________ .0 .0 .0

Cyclohexane __ ____________ 45.0 9.9 4.7

3,3-Dimethylpentane _____________ .0 .0 .0

1,1-Dimethylcyclopentane ___ ______ .0 .0 .1

2-Methylhexane ________________ .0 .9 .5

2,3-Dimethylpentane __ _________ .0 .7 .2

l,Cis-3-dimethylcyclopentane _______ .0 1.6 .8

3-Methylhexane _______________ .0 .8 .6

l,Trans-3-dimethylcyclopentane _____ .0 1.2 .8

l,Trans-2-dimethylcyclopentane ___ _ .0 2.9 1.4

3-Ethylpentane ________________ .0 .0 .1

2,2,4-Trimethylpentane ___________ .0 .0 .0

n-Heptane ___________ _ _______ .0 1.4 .6

l,Cis-2-dimethylcyclopentane _______ .0 .0 .1

Methylcyclohexane ______________ .0 15.1 8.8

Ci to Cr hydrocarbons, total :

g/g sediment ______________ 6x10^ 7x10^ 2x10-°

g/g organic carbon ____________ IXlO'8 SxlO"6 SxlO'5

25.8 

25.4

4.7 

12.7

4.8

3.8 

.0 

.4 

.1

2.0 

.8 

.8

1.8 

.0

4.8 

.0 

.0

6.5 

.0 

.0 

.2 

.0 

.3 

.3 

.4 

.5 

.0 

.0 

.4 

.0

3.5

IxlO'8 

5xlO'5

7.1

7.1 

.0

3.6 

.9

1.8 

.0 

.0

5.3 

.0 

.0 

.0 

.0 

.0

21.1 

.0 

.0

53.1 

.0 

.0 

.0 

.0 

.0 

.0 

.0 

.0 

.0 

.0 

.0 

.0 

.0

SxlO"8 

5xlO-8

37.5

8.0

4.0

4.7

.0

2.2

.0

.0

.0

4.5

.0

.0

.0

.0

12.5 

.0 

.0

26.6 

.0 

.0 

.0 

.0 

.0 

.0 

.0 

.0 

.0 

.0 

.0 

.0 

.0

4xlO-B

about 125°F (Evans and Staplin, 1970). Biogenically generated dry gas can form only at 

low temperatures (Claypool and Kaplan, 1974). 

Thus, the types of sediments in the COST No. 

B-2 well, although still somewhat immature 

with respect to liquid^hydrocarbon generation, 

may have been significant sources of dry and 

possibly wet gas.

The data also do not rule out generation of 

gas or oil in deeper, more thermally mature 

horizons, coupled with lateral and (or) vertical 

migration into favorable traps.

GEOCHEMICAL MEASUREMENT AND 

INTERPRETATION-A COMPARISON

The samples from the COST No. B-2 well 

were analyzed by a contract service-research 

laboratory (Geochem Laboratories) and by research laboratories of some participating major 

oil companies (including Superior, Amoco, and 

Phillips) prior to and in addition to ttye analyv 

ses done by the USGS. The reports of these 

private companies are on file for public inspection at the offices of the USGS, Washington,

D.C. It is interesting to compare the results and 

interpretations of different laboratories on samples from this well.

These analyses are compared with respect to 

the properties of the sedimentary organic matter they are intended to measure: richness, type 

(oil versus gas potential), and degree of maturity. These analyses are summarized for comparison in figures 17, 18, and 19.

In figure 17, organic-carbon measurements 

done by Geochem Laboratories (1976) are compared with those done by the USGS. In general, 

the agreement on these analyses are excellent. 

Both sets of measurements, performed on independently selected samples, clearly show that 

the main intervals that contain rocks rich in organic carbon (>1 percent) are from about 

3,000 to 6,000 feet and from about 10,000 to 14,- 

000 feet. The USGS data show a sample containing 2.1 percent organic carbon at 8,220 to 

8,240 feet, whereas all the samples analyzed by 

Geochem Laboratories in this same general 

interval are less than 1 percent.

54
ORGANIC CARBON C4 -C7

CONTENT C15 + EXTRACTION DATA HYDROCARBON CONTENT

(percent) (ppm by weight) (PP111)

0.0 1.0 2.0 3.0 0 2000 4000 6000 0 100 1000 1QOOO 10QOOO

2^

i

3-j

;

4 1

^

5-

-

«j

i

7^

 j

:

-_

10-=

;

1 1~

:

121

;

:

13-

:

14-

3

i

I

16-5

:

\

o

 o

 1

U C

 c

 c

o

MHM»

e

 MB* 

 MM*

MHMMH 

MMl^

J2

O

MMMMJ

MMMMi

 

> 

 O

1

)

i

o'

M>

'

i

|MMM

- c

C

e 

o 

 ©

)

5.10

o

6.0

|

D '

u2-

3-

4-

5-

i

1

6-

7-

8-

i

9-

5.45

10-

11-

12-

4.92

) 13-

6.53

14-

15-

( 16-

17-

T 

5

3

e

z

7

D _

b

y

5^^

 

___

___

T

-

o

 

u

 

 

 i 

O

O

s 

D

D

}

b

k

MB

M»

MMI

o

-

MM.

MMM-

-

'

9600 

C

O

u1-

2- 

3- 

4- 

5- 

6- 

7- 

8- 

9-

10-

11-

12-

13-

14-

15- 

16-

17 

^Zl

"""" ^

I^MIB 

 ^^ ^

 ^ M^M 

^ ^^

____^^

1

 ^^-1

o^^ d 

 

___^_

M^^H^^ 

 

1

 MMH^

 

 1

i^_^_l 

 

 

 1

ll

^ MB^^

 

 >__^ 

_____M

 _^_»

_ -^

^i^^^^ 

____

, 

P

P

-

w

r 

C 

.

k_

 

L 

IMVV 

) 

1 

^ MM

V

MB

H»

 

. .......

0.0 1.0 2.0 3.0 2000 4000 6000 100 1000 1QOOO 10QOOO

FIGURE 17. Summary and comparison of analyses of richness of sediments 

in the COST No. B-2 well. Geochem Laboratories (1976) data are 

shown as bars, whereas USGS data are shown as circles.

55
In figure 17, a comparison also is shown between the GIS+ extraction data of Geochem 

Laboratories (1976) and organic compounds 

volatilized at less than 680°F (360°C) during 

thermal analysis by the USGS; both are expressed in parts per million by weight basis. 

These two different methods for estimating richness of organic matter are in fair agreement. 

The differences present are probably partly due 

to the effect of the different analytical techniques used, although both are inferred to measure the same constituents. The extraction 

technique depends on volatility to remove 

organic compounds from the rock. The thermal-analysis technique will detect light hydrocarbons that are lost in the isolation and 

gravimetric d5 + -extractable determination. 

The solvent-extraction technique will remove 

very heavy (mostly asphaltic) compounds that 

are either nonvolatile or that are not transported from the furnace to the detector through 

lines maintained at 482°F (250°C). Where the 

GIS +-extraction yields are significantly higher 

than the 86° to 680°F (30°-360°C) thermalanalysis yield, it is generally for samples that 

have especially high NSO+ asphaltine content. 

The 86° to 680°F (30°-360°C) thermal-analysis yields are higher than extraction yields for 

the interval (12,000-14,000 feet) where the 

highest C4 to C7 hydrocarbon contents were 

detected by Geochem Laboratories (1976) in a 

separate analysis, (fig. 17).

The extractable organic matter present at 

relatively high concentrations in the interval of 

about 9,000 to 14,000 feet was concluded by the 

USGS to be unlike petroleum, on the basis of 

gas-chromatographic analysis of the saturated 

hydrocarbons and by comparison of thermally 

extracted material with that generated by pyrolysis. Geochem Laboratories (1976, p. 2) had 

earlier arrived at the same conclusion, that is, 

that " this interval has only generated methane gas and C2-C4 'wet gas' hydrocarbons. 

This fades has not generated any petroleumrelated liquids and it is unlikely that any oil will 

be found in the immediate area of this well."

Four measurements that are sensitive to the 

type of organic matter in the COST No. B-2 

well are summarized for comparison in figure 

18. The first column shows a direct measurement of kerogen type and relative abundance, as 

determined in miciroscopic examination. The 

next three columns of figure 18 show the yield

of pyrolytic hydrocarbons as a percentage of 

organic carbon, the atomic ratio of hydrogen to 

carbon in the kerogen, and the stable carbon 

isotopic composition of various fractions of the 

organic matter. These latter three techniques 

give an indirect indication of the type of organic matter and are also influenced by the 

state of diagenesis or degree of thermal maturation. The pyrolytic hydrocarbon yield as a 

percentage of organic carbon and the atomic 

hydrogen-carbon ratio of the kerogen are both 

related to the structure and liquid-hydrocarbongenerating potential of the kerogen. A fairly 

good correlation exists between these two measurements in the COST No. B-2 well, as shown, 

in columns two and three of figure 18.

The stable carbon-isotope ratio, 13C/12C, is 

shown in figure 18 as parts per thousand (per 

mil) deviations from the 13C/12C ratio of the 

PDB marine carbonate standard. 813C values 

are reported for kerogen (the fraction of the 

organic matter insoluble in benzene-methanol) 

for the total extract (the soluble fraction), and 

for the saturated or paraffin-napthene hydrocarbons that are separated from the total extract. The carbon-isotope ratio primarily 

reflects the nature of the source material or the 

environment in which the organic matter was 

generated by photosynthesis. In addition, the 

difference in 813C between the kerogen and totalhydrocarbon extract may indicate the extent to 

which possible petroleumlike constituents have 

been generated from the solid organic matter.

In the COST No. B-2 well, the 81SC values of 

the kerogen appear to reflect the zonation seen 

on the basis of other organic geochemical characteristics, as described by Geochem Laboratories (1976). This fact probably reflects the 

abundant coaly material in Zone B. In general, 

a spread of about 2.5 per mil or mofre is 

found between the saturated hydrocarbon (or 

the extract) and the kerogen. This spread indicates that the materials probably have largely 

unrelated origins and that these lipid materials 

have not been generated from the kerogen by 

thermal diagenesis.

Figure 19 shows five different indicators of 

organic metamorphism or maturation the numerical index (CPI) of the predominance of 

odd-numbered n-paraffin in the saturated hydrocarbons, the visual kerogen thermal-alteration index, vitrinite reflectance, temperature of 

maximum pyrolysis yield, and pelrcent carbon

56
Relative kerogen Pyrolitic

type ond abundance hydrocarbon/organic carbon

(percent) (percent)

0 50 100 _Q___50_ 100

5^

6^:

8-3:

io-3i

12-3

13-3

14-3

15-3

16-3

7-3

11-3

12-3

13-3

15-3

16-3

17-

o o

1-3

2-3

10-3

13-3

15-3

17-

Atomic H/C ratio

0 4 .6 .8 1.01.21.4

6 Cpp, (permil)

-28 -27 -26 -25 -24 -23

3-3

10-3

14-3

 oo -

o -

- 

O-i

O Saturated hydrocarbon Kerogen 

 Total extract

FIGURE 18. Summary and comparison of analyses of type of organic matter in COST No. B-2 well samples. Data 

in the first column are from Geochem Laboratories (1976) ; second column, from this volume; third column, from 

Amoco Production Company (J. A. Momper, written commun., 1976); and the last column, from Phillips Petroleum Company (J. G. Erdman, written commun., 1976).

57
fC P I index A 

Geochemi stry J £ p | in jex g e

\JJ SG S CPl ®

Visual Ice

-HVitrinite reflectance 

(Ko percent)

 3 .4 .5 .6 .7 .8 .91.0

Temperature maximum pyrolysis yield

(degrees Celsius) 

430 440 450 450 470 480 490 65 75 85

FIGURE 19. Summary and comparison of analyses of maturity of organic matter in the COST No. B-2 well. Data 

in first column are from Geochem Laboratories (1976) and Claypool (this volume); in second column, from 

Geochem Laboratories (1976); in third column, from Superior Oil Co. (W. G. Dow, written commun., 1976); 

in fourth column, from Claypool (this volume); in fifth column, from Amoco Production Company (J. A. Momper, written commun., 1976).

in the kerogen. All these indicators show significant change as depth increases in the COST 

No. B-2 well. Although agreement is excellent 

among the different measurements, there are 

some apparent differences in interpretation of 

the significance of these measurements with 

respect to the generation of hydrocarbons. The

interpretation of the vitrinite reflectance data 

by Superior Oil Company (W. G. Dow, written 

commun., 1976) stated that, "Although both 

oil and gas begin to be formed at maturities of 

about 0.45 R0 (6,800 feet in the subject well), 

maximum generation and expulsion occur only 

below the top of the peak generation zones. On

58
the basis of these criteria, effective oil source 

rocks (those which have both generated and 

expelled oil) could be present bqlow 11,300 feet 

if organic matter capable of conversion to oil is 

present." The diagram accompanying this report shows "peak generation" at R0 value of 0.6 

percent, which takes place at 11,300 feet in this 

well.

The report on elemental analyses by Amoco 

Production Company (J. A. Momper, written 

commun., 1976), referring to the degree of 

carbonization of the kerogen, stated that, "The 

diagenesis level below 10,000 feet is equivalent 

to the peak stage for oil generation." This report also emphasized that the elemental data 

must be considered with the geochemical data 

of Geochem Laboratories (1976) and the vitrinite reflectance data of Superior Oil Company 

(W. G. Dow, written commun., 1976).

These reports of "peak generation" in the 

lower part of the section penetrated in the 

COST No. B-2 well seem to many observers to 

be in conflict with the interpretation by Geochem Laboratories (1976, p. ii) that, "These 

sediments (9,500±feet to 14,000±feet) have 

experienced an insufficient geothermal (timetemperature) history to have generated any 

petroleum-related liquids in the immediate 

vicinity of the COST No. B-2 well," or our interpretation that the organic matter in all samples analyzed appears to be immature in greater 

or lesser degree with respect to the degree of 

liquid-petroleum-hydrocarbon generation required for expulsion and economic occurrence 

of petroleum.

These apparent inconsistencies are due to 

the difficulty of inferring the extent of hydrocarbon-generating reactions from the nature of 

the solid organic matter. The decrease in CPI 

with depth shows that hydrocarbon generation 

began as depth increased in the COST No. B-^2 

well. A greater change is shown for the USGS 

CPI data because the gas-chromatographic 

analysis was performed on SE-30-packed 

columns rather than on eutectic-salt-packed 

columns. The odd-carbon predominance is usr 

ually most pronounced in the n-C29 legion, and 

these compounds are partially oxidized during 

analysis on the eutectic column. This means 

that the CPI values given by Geochem Labora-f 

tories (1976) are minimum values and in particular do not reflect the degree of immaturity

at shallow depths (less than 6,000 feet) in the 

COST No. B-2 well. Regardless of differences 

in the analytical technique, CPI decreases significantly between 3,000 feet and 12,000 feet. 

This undoubtedly reflects some degree of hydrocarbon generation. However, both the molecular composition of the saturated hydrocarbons 

in samples at 12,000 feet and the remaining 

hydrocarbon-generating potential shown by pyrolysis of samples at 13,000 feet indicate that 

the "principal phase of oil formation" has not 

yet taken place in this well.

The terms "peak generation" or "the top of 

the peak generation zone," as indicated by vitrinite reflectance and kerogen carbonization, 

are apparently used to designate upper depth 

limits, below which effective oil source rocks 

may occur and above which they cannot occur. 

Therefore, additional evidence is required before rocks at a specific depth in a well can be 

properly considered effective or possible oilsource rocks.

Another apparent contradiction lies in the 

interpretation of the geochemical data with regard to the gas- or wet-gas-source capabilities 

of the sediments penetrated in the COST No. 

B-2 well. Geochem Laboratories (1976), on the 

basis of measurement of d to C7 hydrocarbons, 

indicated that'the interval from 9,500 to 14,000 

feet has undergone good to excellent gas and 

wet-gas generation. However, the report by 

Superior Oil Company (W. G. Dow, written 

commun., 1976) concluded that "If only wet-gas 

source beds are present, they would be effective 

only below about 19,000 feet. . . ." The report 

by Amoco Production Company (J. A. Momper, 

written commun.,1976) implied a similar interpretation, in that a diagenesis level equivalent 

to peak generation for oil was considered early 

generation to early peak generation in sediments containing kerogen with potential only 

for wet-gas or gas generation. This interpretation is probably based on the fact that the main 

stage of gas production during coalification is 

after the stage of maximum liquid-hydrocarbon 

production (Teichmiiller and Teichmiiller, 

1968). Sediments having an unusually high organic carbon content might be effective source 

rocks at a level of maturation less than the 

standard "peak generation" for either gas or 

oil. This may be the case for gas generation 

from the 9,500-to-14,000-foot interval of the 

COST No. B-2 well.

59
Color Alteration of Visible Organic Matter

By E. I. Robbins

Color alteration of visible organic matter as 

a function of burial depth, especially when used 

in conjunction with vitrinite reflectance and organic geochemistry, can provide an indication 

of the probable maximum burial temperatures 

reached by the sediments and has strong beaming on the potential for hydrocarbon generation.

The sapropel fraction of organic matter is 

the amorphous breakdown product of living 

tissue. If the definition of Staplin and others 

(written commun., 1974) is used, this sapropel 

fraction is any amorphous matter present in 

aquatic sediments (in soil it is named humus) 

that has been created in relatively anoxic environments of deposition. Microscopically, it is 

seen as two forms: wispy, which was believed 

by Staplin and others (written commun., 1974) 

to form in higher energy environments; and 

fluffy, which accumulates in low-energy and 

more reducing environments.

The type of sapropel, as well as total organic 

matter, is important from the viewpoint of the 

type of hydrocarbon that will be generated 

(Mclver, 1967; Burgess, 1974). The endpoint 

of the disseminated wispy sapropel and terrestrial organic matter is predominantly methane. 

The endpoint of the oil-shale type, the fluffy 

sapropel, can be liquid petroleum.

Most of the organic matter responds to temperature increases in the following manner: As 

volatile matter and oxygen are driven off, car-* 

bon is enriched, and the organic matter and its) 

breakdown products become darker. On the 

basis of this response, a thermal-alteration scale 

has been prepared (Staplin, 1969; Evans and 

Staplin, 1970; Burgess, 1974). Because the petroleum-generating stage (the onset of browns) 

and the end of petroleum generation (black) 

are clearly recognizable, the technique is useful

for determining the interval of probable liquidpetroleum generation.

The method of treatment is important as it 

determines the final interpretation of the organic matter (Bostick, 1971). Samples for the 

study of the sapropel fraction were composed 

of 100-foot composited intervals every 500 feet. 

Sample preparation included treatment in 10- 

percent HC1 (overnight) to eliminate carbonates and 50-percent HF (24 hours) to eliminate 

silicates.

DATA

Figures 6 and 20 are compilations of data 

collected on the degree of thermal alteration of 

the organic matter, relative sapropel abundance, and maturity. The terms for the degree 

of maturation in figure 20 have been taken from 

Evans and Staplin (1970) and refer to the 

maturity of the hydrocarbons. Immature sediments should contain yellow sapropel, mainly 

Ci gas, few gasoline-range hydrocarbons, and 

abundant heavy nonhydrocarbon compounds 

(mainly containing N, S, and 0). Mature facies 

should contain orange to brown sapropel, significant C$ to C4 gases, and abundant gasolinerange and heavy hydrocarbons.

Figure 20, shows an overall systematic increase in maturity of the sapropel as depth increases. However, from 5,510 to 6,090 feet, an 

anomalously sharp increase in maturity is indicated. From 14,510 to 15,600 feet there is a 

slight anomalous decrease in maturity.

Reworking, bacterial degradation, and oxidation are important processes that can be recognized and that must be differentiated from 

thermal alteration. Reworking is indicated by 

samples containing organic matter that has the 

whole spectrum of natural and alteration colors

60
Sapropel Abundance ot sapropel Abundance of all organics

maturation . . . n

barren little some abundant barren little some abundant 0

Organic carbon

(weight percent)

1 2 3

Sapropel type

. mixed.. ., 

4 wispy Hurry

Immature

Mature?

§

X

H 

LU

z

Immature

Mature

T T

6.0

10

11

12

13

14

15 -

16 -

FIGURE 20. Maturation, abundance, and types of sapropel, abundance of organic matter, and weight percent organic 

carbon as a function of depth. Weight percent organic carbon taken from report by Claypool and others (this 

volume).

 black, orange, brown, and yellow. Reworked 

organic grains are present in COST No. B-2 

well samples from 1,600 to 1,630 feet, 6,420 to 

6,430 feet, 6,320 to 6,330 feet, and 14,510 to 

14,580 feet. Degraded organic matter, which 

suggests bacterial breakdown, is found in the 

following intervals (in feet) : 4,290 to 4.320, 

6,000 to 6,090, 7,010 to 7,100, 7,500 to 7,590, 

8,220 to 8,240, 9,100 to 9,130, (9,430 to 9,440?), 

(10,960 to 10,990?), 11,260 to 11,290, 11,560 to

11,590, 11,860 to 11,890, 12,160 to 12,190, 12,- 

460 to 12,490,13,010 to 13,080,13,300 to 13,330, 

15,120 to 15,130, and 15,720 to 15,730. Oxidized 

zones are common from 9,500 to 15,730 feet but 

also are found from 3,010 to 3,100 feet, 3,520 to 

3,610 feet, 4,000 to 4,100 feet, and 4,500 to 

4,620 feet.

The part of the stratigraphic section that has 

reached thermal maturity and that has the 

highest weight-percent organic carbon also

61
contains dominantly wispy sapropel (fig. 20). 

This type generates mainly methane and not 

liquid petroleum. Thus, the potential of these 

lower intervals in the COST No. B-2 well is 

highest for gas generation, a conclusion substantiated by the organic geochemical data 

presented in this report.

CONCLUSIONS

The organic matter in the COST No. B-2 well 

shows an overall systematic increase in maturity with depth. In the depth range from 9,300 

feet to the bottom of the well, temperatures apparently have been sufficient for generation of 

hydrocarbons. However, in the intervals with 

high weight-percent organic carbon, the sapropel is of the type more likely to yield natural 

gas than liquid petroleum. Deeper parts of the 

section, not penetrated by the COST No. B-2 

well, are likely to be even more thermally mature and could have acted as gas or liquidhydrocarbon sources, depending on the type 

and amount of organic matter they contain.

62
Geophysical Studies

By D. J. Taylor, R. E. Mattick, and K. C. Bayer

Figure 3, an interpretive profile of seismicreflection data from USGS Line 2, summarizes 

much of the geophysical data obtained in the 

Baltimore Canyon trough. Line 2, a 12-fold, 

common-depth-point (CDP), stacked section, 

was shot and processed by Digicon, Inc., in 

1973. The location of the seismic line on the 

New Jersey shelf is shown dn figure 1; the 

COST No. B-2 well and the onshore USGS Island Beach No. 1 well are projected into the 

line of section. Correlation of seismic reflectors 

with geologic units in the COST No. B-2 well is 

based on the work discussed earlier in this report together with velocity data derived from 

sonic logs recorded in the B-2 well (fig. 21). 

The correlation with the Island Beach well is 

based on the stratigraphic work of Perry and 

others (1975), pollen analyses of Doyle (written commun., 1974), and velocity analysis of 

the seismic-reflection data of Line 2.

SEISMIC STRATIGRAPHY

The age horizons determined from the COST 

No. B 2 well are illustrated in figure 3 to show 

their subsurface configuration. Previous determinations of the Neogene-Paleogene and 

Teritary-Cretaceous boundaries (Mattick and 

others, 1974) are in reasonable agreement with 

the revised interpretations made using COST 

No. B-2 well data.

The foreset bedding seen in the upper Tertiary section of seismic Line 2 has been interpreted by Garrison (1970) to represent a seaward progradation of deltaic sediments across 

the shelf during Tertiary time. As shown in 

figure 3, sediments from the base of the 

Pleistocene to the top of the Eocene thicken in 

a seaward direction from the Island Beach well, 

whereas Eocene and Paleocene beds remain

relatively uniform in thickness across the seismic record section. According to Smith and 

others (1976), the lower Tertiary rocks produce strong seismic reflections having reflection 

coefficients +0.3 and -03.

Upper Cretaceous strata are rather uniform 

in thickness from the USGS Island Beach No. 1 

well to the edge of the Continental Shelf along 

Line 2. Again, however, thinning is evident 

over the intrusion. The COST No. B-2 well 

data have significantly raised the Upper Cretaceous-Lower Cretaceous boundary relative to 

earlier estimates by Mattick and others, 

(1974). Previously, Lower Cretaceous sediments were thought to begin at 2.4 seconds at 

shotpoint 1203 (where the COST No. B-2 well 

is projected into the section). This determination was based on extrapolation of onshore well 

data into the regional dip.

Lower Cretaceous rocks clearly thicken significantly from the Island Beach well to the 

northwest flank of the basement intrusion 

(shotpoint 900). Seaward of the intrusion, the 

Lower Cretaceous is again thought to be thick, 

although perhaps thinning seaward over possible reefs in Jurassic strata under the presentday Continental Slqpe. A seismic horizon 

slightly below the top of the Lower Cretaceous 

represents a prominent unconformity where at 

least 1,300 feet of sediment was removed by 

erosion. Jurassic strata apparently were not 

found in either the Island Beach well or the 

COST No. B-2 well; thus, correlation of the 

top of the Jurassic is difficult.

Near shotpoint 600, strong reflectors appear 

on the seismic record section at a depth of 4.0 

seconds. Interval velocities in the seismic time 

section between 4 and 5 seconds in this area 

may range from 16,000 ft/sec to more than 

20,000 ft/sec. These high interval velocities are

63
MEANO 

SEA 

LEVEL

1.0 

2.0 

3.0 

4.0 

5.0 

6.0 

7.0 

8.0

~ 9.0 

x

£ 10 

z

t " 

iti

Q

12

13

14

15

16

17

0.5

SEISMIC TIME (TWO-WAY), IN SECONDS 

1.0 1.5 2.0 2.5 3.0 3.5

1.0

2.0

o 

m TJ -H

Z

3.0 5 

o 

m 

m

4.0

5.0

FIGURE 21. Seismic travel time (two-way) as a function of depth from the COST No. B-2 well sonic logs.

interpreted to represent a thick Jurassic and 

(or) Triassic sedimentary section.

Acoustic basement is thought to appear as a 

distinctive diffraction pattern at a depth of 

1.65 seconds on the northwest end of Line 2, 

which correlates with crystalline basement 

rocks in the Island Beach well. According to 

Mattick and others (1975) and Schlee and 

others (1976), this horizon deepens to more 

than 45,000 feet and appears at approximately

7 seconds (reflection time) in the vicinity of 

shotpoint 800. Near shotpoint 500, the basement horizon is underlain by a series of more 

steeply dipping reflectors. These have been interpreted by Mattick and others (1976) as 

representing Triassic or Paleozoic marine sediments. According to Schlee and others (1976), 

these reflectors may indicate layering within 

metasedimentary rocks thought to underlie the 

Baltimore Canyon trough.

64
Between shotpoints 900 and 1,100, sedimentary rocks, which are otherwise gently dipping, 

are warped upward. In this area, Taylor and 

others (1968) have mapped a 500-gamma magnetic high interpreted as a basement intrusion 

that may be in a zone of weakness near the 

intersection of two fault systems, one parallel 

to the Continental Shelf and a second oblique 

to the shelf edge. Although depth to basement 

in the vicinity of the intrusion cannot be determined from the seismic record section, John 

C. Behrendt (written commun., 1976), has 

indicated that the depth to magnetic basement 

at shotpoint 1,000 is between 12,000 and 13,000 

feet.

Another smaller piercement structure is seen 

in the vicinity of shotpoint 725. As reflectors 

seem to continue through the structure, we assume it to be out of the plane of section.

LITHOLOGIC INFORMATION

The sedimentary section in the Baltimore 

Canyon trough, previously inferred from seismic response and now confirmed by COST No. 

B-2 well information is composed primarily of 

sand and shale. The relative percentages of 

each lithology and their degree of diagenetic 

alteration have been unknown until now.

As evident from the COST No. B-2 well, the 

upper Tertiary, from the upper Pliocene to 

about the middle Eocene, consists mainly of 

sandstone, shale, and mudstone that have been 

compacted to varying degrees. Seismic evidence 

suggests that this is true throughout the basin, 

the degree of compaction increasing below the 

lower Miocene. Relatively low interval velocities, computed along seismic-reflection Line 2 

indicate that upper Tertiary rocks may remain 

relatively unconsolidated across the entire 

shelf. From middle Eocene to Late Cretaceous 

time, COST No. B-2 well information reveals 

a relatively dense, calcareous shale and sandstone sequence. These calcareous units are apparently limited to the seaward part of the 

basin, as indicated by a decrease in velocity in 

this interval as one moves toward shore. Velocity in this interval increases significantly over 

the basement intrusion perhaps because of increased compaction over this feature or higher 

sand content in the sediments.

In the Upper Cretaceous strata, the seismic 

signals and the velocity data suggest a predominantly sandstone and shale section. COST 

No. B-2 well data substantiate this and show 

that some limestone beds are also present in 

this interval. Interval velocities decrease in a 

shoreward direction, suggesting a decrease in 

the carbonate content in nearshore areas.

The seismic-reflection signatures and velocity 

information suggest that the lithologies found 

in the Lower Cretaceous section in the B-2 well 

(mainly sandstone and shale) extend throughout much of the basin. Increases in velocity in 

the basal Lower Cretaceous sediments seaward 

of the COST No. B-2 well suggest an increase 

in the amount of interbedded limestone. Velocities in the Lower Cretaceous interval over the 

intrusion (and above the unconformtiy) do not 

indicate a strong increase in compaction.

Although Jurassic strata apparently were 

not penetrated in the COST No. B-2 well, a 

significant thickness of Jurassic sediments is 

thought to exist in the deeper parts of the basin. 

Seismic evidence suggests a more calcareous 

lithology for the Jurassic (?) section than for 

the overlying section. According to Maher 

(1971), a 100-foot carbonate sequence was 

found in the Esso Hatteras Light No. 1 well 

(North Carolina) at the top of the Jurassic or 

base of the Cretaceous. The interval contains 

oolitic limestone, porous granular dolomite, and 

anhydrite. Dip rates projected from onshore 

well data suggest that Jurassic beds thicken in 

an offshore direction. On the basis of a refraction survey shot by Hersey and others (1959), 

Gibson (1970) suggested that a thick layer of 

rocks, which appears to onlap crystalline base-, 

ment, offshore from the Hatteras well, represents a seaward extension of the Jurassic 

limestone, dolomite, and anhydrite.

Carbonate rocks of Jurassic age (Abenaki 

Formation) have also been reported beneath the 

Scotian Shelf off Canada (Mclver, 1972). In 

addition, information from DSDP hole 105 indicates that east of the Baltimore Canyon 

trough, near the base of the Continental Rise, 

about 2,000 feet of Neocomian, Tithonian, Kimmeridgian, and Oxfordian limestone overlies 

oceanic basement (Hollister and others, 1972).

On the basis of a velocity inversion below 

40,000 feet, Mattick and others (1976) have 

speculated that Lower Jurassic evaporites may 

overlie basement rocks in the Baltimore Canyon 

trough area. Other evidence of evaporites on 

the Atlantic margin comes from well data on

65
SHOT POINT 

630

O5 

Oi

3.0 n i i

TRACES AT WHICH PARAMETERS CHANGE

2.65 1.615 1.0 100 

Gas zone 

Wet zone

5.085 2.65 1.615 1.0 0.610 .2 70 30 

5.085 2.65 1.615 1.0 0.610 .2 100 

SHALE VELOCITY AND DENSITY VARIATIONS AS INDICATED

FIGURE 22. A computer model of possible lithologies and physical parameters determined from amplitude anom

on seismic-reflection profile "(fig. 3) between shot points 630 and 750. Modeling was done by Brad Pitney 

symbols used are as follows: Vm , matrix velocity in ft/sec; pm, matrix density in g/cm8 ; Vw, water velocity 

density in g/cms ; Vhc , hydrocarbon velocity in ft/sec; PUC , hydrocarbon density in g/cms ; Sw, percent w

percent hydrocarbon saturation; dash, value not estimated; 4>, porosity in percent; V, velocity in ft/sec, d

gas content; p, density in g/cms, disregarding fluid and gas content. Note layer 7 gas saturation is estima
the Canadian shelf. The Shell Argo F-38 well, 

on the south flank of the Orpheus basin north 

of Nova Scotia, drilled through approximately 

2,600 feet of relatively pure halite. In addition, 

on the basis of seismic data, Emery and others 

(1970) have suggested that diapiric salt structures are present along the Continental Slope 

and Rise off Nova Scotia. Similar structures 

may exist in the Baltimore Canyon trough area. 

Jurassic strata are not thought to lye present 

over the intrusion along Line 2; whether or not 

Jurassic is present seaward of this feature is 

speculative. If present, its lithology is inferred 

to be mainly carbonate rocks containing little 

salt.

AMPLITUDE ANOMALIES

True amplitude processing of Line 2 revealed 

an amplitude anomaly between shotpoints 640 

and 760. Depth to the anomaly is 0.75 to 0.80

seconds, corresponding roughly to 3,700 to 

3,800 feet. Projection from the COST No. B-2 

well and from the Island Beach No. 1 well indicates that these sediments are of late Oligocene age and are composed predominantly of 

shale and claystone containing a few beds of 

coarse-grained sandstone.

Seismic modeling or "bright-spot" analyses 

indicates that the amplitude anomaly could be 

caused by a gas sand trapped between shale 

beds. As modeled (fig. 22), the sand is in a 

foreset sequence; updip migration of gas is 

blocked by an impermeable shale barrier. A 

water drive is indicated on the low side of the 

sand body. Maximum reservoir-sand thickness 

is calculated to be about 100 feet near shotpoint 

680. Porosity in the gas sand was modeled as 

ranging from 26 percent to 28 percent. Saturation of water and gas were calculated as 70 percent and 30 percent, respectively.

67
Conclusions

1. The COST No. B-2 well penetrated nearly 

16,000 feet of sediment in the Baltimore 

Canyon trough of the AOCS. The age of 

the sediments (determined through the 

examination of Foraminifera, calcareous 

nannofossils, and palynomorphs) is Cenozoic down to about 5,000 feet. From 5,000 

to 8,100 feet, the sediments are Late Cretaceous in age, and from 8100 feet to the 

base of the well, they are Early Cretaceous. Although no positive indications of 

Jurassic sediments were found in this 

well, a Jurassic age cannot be ruled out 

for the basal 1,000 to 2,000 feet of section.

2. Early Cretaceous depositional environments 

in the B-2 area were apparently primarily 

nonmarine; occasional shallow marine incursions took place. The Late Cretaceous 

environments were generally shallow marine, with the exception of a nonmarine 

interval during the Coniacian and Santonian. During the Eocene, water depths 

were similar to those found on present 

continental slopes; later Tertiary sediments were deposited in outer- to innershelf environments.

3. The dominant lithologies found were sandstone and shale and minor limestone, coal, 

and lignite. Sand-shale ratios vary with 

depth but generally are 25 to 65 percent.

4. Porosities and permeabilities in the sandstone and shale section decrease rapidly 

as depth increases, so that below 12,000

feet, most sandstones have less than 15 

percent porosity and 1 millidarcy permeability.

5. Petrographic analysis indicates that most 

of the sandstone is feldspathic. Much of 

the porosity loss seen at depth is due to 

breakdown of feldspar and the generation 

of authigenic clay and silica cement. Calcite cement is also very important, 

especially in zones having primary calcareous components.

6. The present geothermal gradient in the 

COST No. B-2 well is 1.3°F/100 feet.

7. Organic geochemistry and color alteration 

of visible organic matter, in conjunction 

with vitrinite reflectance, indicate either 

immaturity or low thermal maturity for 

most of the section down to at least 12,000 

feet. Furthermore, although many units 

have very high organic carbon contents 

(as much as 12 percent), most of the 

sediments in the most thermally mature 

zones have terrestrially derived organic 

matter.

8. The combination of all the above factors 

indicates a relatively low potential for 

liquid-hydrocarbon generation and a relatively high potential for natural-gas generation. Deeper parts of the section 

(below 16,000 feet) or other parts of the 

Baltimore Canyon trough may have the 

potential to generate oil or gas, depending 

on the amount and character of their contained organic matter.

68
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