GEOLOGICAL SURVEY CIRCULAR 833 

Geological Studies of the 

COST No. B-3 Well, 

United States Mid-Atlantic 

Continental Slope Area 

Geological Studies of the 

COST No. 8-3 Well, 

United States Mid-Atlantic 

Continental Slope Area 

By Peter A. Scholle, Editor 

GEOLOGICAL SURVEY CIRCULAR 833 

1980 
United States Department of the Interior 

CECIL D. ANDRUS, Secretary 

Geological Survey 

H. William Menard, Director 

Free on application to Branch of Distribution, U.S. Geological Survey, 1200 South Eods Street, Arlington, VA 22202 
CONTENTS 

Page 

Abstract--------------------------------------------------------------------- 1 

Introduction----------------------------------------------------------------- 3 

Acknowledgments-------------------------------------------------------------- 3 

Geologic setting and hydrocarbon exploration activity, by Robert E. 

Mattick and Kenneth c. Bayer----------------------------------------------- 4 

Data summary and petroleum potential, by Peter A. Scholle-------------------- 13 

Lithology, by Barry M. Pollack----------------------------------------------- 20 

Sandstone petrography, by Barry M. Pollack----------------------------------- 24 

Computer well-log analysis, by Ching H. Wu and Renny R. Nichols-------------- 26 

Foraminiferal stratigraphy, paleoenvironments, and depositional 

cycles in the outer Baltimore Canyon trough, by c. Wylie Poag-------------- 44 

Calcareous nannofossil biostratigraphy, paleoenvironments, and postJurassic continental margin development, by Page c. Valentine-------------- 67 

Organic geochemistry, by R. E. Miller, D.M. Schultz, G. E. Claypool, 

M. A. Smith, H. E. Lerch, D. Ligon, D. K. Owings, and c. Gary-------------- 85 

Geophysical studies, by David J. Taylor and Robert c. Anderson--------------- 105 

Seismic stratigraphy in the vicinity of the COST No. B-3 well, by 

John s. Schlee and John A. Grow-------------------------------------------- 111 

Deep structure and evolution of the Baltimore Canyon trough in the 

vicinity of the COST No. B-3 well, by John A. Grow------------------------- 117 

Conclusions------------------------------------------------------------------ 125 

References cited------------------------------------------------------------- 126 

Figure 1. 

2. 

3. 

4. 

5. 

6. 

8. 

g. 

10. 

11-14. 

15-19. 

ILLUSTRATIONS 

Page 

Locality map----------------------------------------------------- 2 

Isopach map of sediment thickness in the Baltimore Canyon 

trough area---------------------------------------------------- 5 

Geological cross section of Baltimore Canyon trough-------------- 6 

Correlation chart of Cretaceous strata of the mid-Atlantic 

Coastal Plain-------------------------------------------------- 7 

Generalized stratigraphic section in the Baltimore Canyon 

trough---------------------------------------------------------

Map showing locations of deep exploratory wells drilled 

in Baltimore Canyon trough-------------------------------------

Generalized lithologies and depositional environments for 

COST No. B-3 well----------------------------------------------

Porosities and permeabilities as a function of depth-------------

Comparison of various geochemical and thermal parameters 

as a function of depth-----------------------------------------

Generalized lithologic plot--------------------------------------

Comparison of measured and computed porosities for the 

interval: 

11. From 9,921 to 9,935 ft (3,024-3,028 m)-------------------

12. From 11,010 to 11,060 ft (3,356-3,371 m)-----------------

13. From 12,573 to 12,587 ft (3,832-3,836 m)-----------------

14. From 13,773 to 13,786 ft (4,198-4,202 m)-----------------

Results of computer well-log analysis (SAM7): 

15. 8,200 to 10,300 ft (2,499-3,139 m)-----------------------

16. 10,300 to 12,400 ft (3,139-3,779 m)----------------------

17. 12,400 to 14,100 ft (3,779-4,297 m)----------------------

18. 14,100 to 15,810 ft (4,297-4,818 m)----------------------

19. 15,700 to 15,810 ft (4,785-4,818 m)----------------------

Ill 

9 

11 

14 

16 

17 

21 

28 

28 

29 

29 

30 

32 

34 

36 

38 
Figure 20-21. 

22. 

23. 

24. 

25. 

26. 

27. 

28. 

29. 

30. 

31. 

32. 

33. 

34-36. 

Page 

Results of computer well-log analysis (CAM7): 

20. 12,400 to 14,100 ft (3,779-4,297 m)---------------------- 40 

21. 14,100 to 15,810 ft (4,297-4,818 m)---------------------- 42 

Index map of stratigraphic drill sites and USGS seismic 

lines in the outer part of the Baltimore Canyon trough--------- 45 

Biostratigraphic column, foraminiferal biozones, and 

paleoenvironments for the COST No. B-3 well-------------------- 46 

Revised biostratigraphic column, foraminiferal biozones, 

and paleoenvironments for the COST No. B-2 well---------------- 46 

Geologic cross section along USGS Seismic Line 25---------------- 50 

Paleoenvironmental cross section along USGS Seismic 

Line 25-------------------------------------------------------- 56 

Lithology, foraminiferal biostratigraphy, and geophysical 

log characteristics for the COST No. B-3 well------------------ 58 

Comparison of sediment accumulation rates at the COST 

Nos. GE-l, B-2, and B-3 well sites----------------------------- 61 

Comparison of global sea-level changes, paleobathymetry, 

and sediment accumulation rates for the COST Nos. GE-l, 

B-2, and B-3 well sites---------------------------------------- 64 

Calcareous nannofossil biostratigraphy and paleoenvironments 

of the COST No. B-3 well--------------------------------------- 68 

Summary of organic-richness analyses on c15+ hydrocarbon 

ext rae tables-------------------------------------------·-------- 90 

Gas-chromatographic analyses of saturated paraffin-napthene 

hydrocarbons of Tertiary rocks--------------------------------- 92 

Summary of light-hydrocarbon analyses---------------------------- 93 

Gas-chromatographic analyses of saturated paraffin-napther~ 

hydrocarbons of: 

34. Upper Cretaceous rocks----------------------------·------- 95 

35. Lower Cretaceous rocks----------------------------------- 97 

36. Jurassic rocks------------------------------------------- 99 

37. Summary profile of indicators of types of organic matter 

present as a function of depth--------------------------------- 100 

38. Maturity profiles of organic matter as a function of 

depth---------------------------------------------------------- 101 

39. Gas-chromatographic analyses of additives to the mud 

drilling system------------------------------------------------ 103 

40-42. Filtered and unfiltered reflection-coefficient traces 

constructed: 

40. From interval-transit-time and density logs-------------- 106 

41. ysing only velocity data from interval-transittime log----------------------------------------------- 106 

42. Using only density data---------------------------------- 107 

43. Synthetic seismograms constructed from velocity and 

density data--------------------------------------------------- 107 

44. Two-way travel time as a function of average velocity 

and root-mean-square velocity---------------------------------- 108 

45. Two-way travel time as a function of depth----------------------- 108 

46. Filtered reflection coefficient trace projected into a 

portion of USGS seismic Line 25-------------------------------- 109 

47. Interval velocity as a function of depth below sea level 

and two-way travel time---------------------------------------- 110 

48. Index map of seismic lines and drill holes in the 

vicinity of the COST No. B- 3 well-----------------------·------- 112 

49. Annotated depth section of a portion of USGS Seismic 

Line 25, between shotpoints 2600 and 3400---------------------- 113 

50. Major reflectors distinguished on USGS Seismic Lines 25, 

34, and 35; keyed to relative sea level curve, 

generalized lithology, and biostratigraphic ages--------------- 114 

51. Interpretation of USGS Seismic Line 25 depth profile 

between shotpoints 1900 and 3900------------------------·------- 115 

52. Time section of USGS Seismic Line 34 between shotpoints 

800 and 1600-------------------------------------------·------- 115 

IV 
Figure 

Page 

53. Time section of USGS Seismic Line 35 between shotpoints 

500 and 1300--------------------------------------------------- 116 

54. Map of continental margin off New Jersey with locations 

of primary s-tructural features and seismic profiles 

discussed------------------------------------------------------ 117 

55. Structural cross section along USGS Seismic Line 25 

between shotpoints 1900 and 3600------------------------------- 119 

56. Annotated multichannel depth section (migrated) for USGS 

Seismic Line 25 with associated magnetic anomalies------------- 120 

57. True-amplitude display (time section) of USGS Seismic 

Line 25-------------------------------------------------------- 121 

58. Multichannel seismic section (Line 2) over the Great 

Stone Dome-----------------------------------------------------

59· Multichannel seismic section (Line 14) over inferred salt 

diapir---------------------------------------------------------

60. Multichannel seismic section (Line 15) showing two small 

domes inferred to be salt intrusions---------------------------

61. Schematic cross section through Baltimore Canyon trough 

approximately along Seismic Line 25----------------------------

Plates 1 and 2.--Light micrographs of selected nannofossils from 

122 

122 

123 

124 

the COST No. B-3 well----------------------------------- 80,82 

Table 1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

TABLES 

Comparison of biostratigraphic analyses from the COST 

NO. B-3 well---------------------------------------------

Petrography of selected sandstones from the COST No. B-3 

well-------------~---------------------------------------

Input data for LOGCALC log analysis program----------------

Lithologic descriptions of samples used for organic 

geochemical analysis-------------------------------------

Organic carbon and extractable organic matter--------------

Organic-carbon and thermal-analysis data-------------------

Analytical data for extractable organic matter in drilling 

mud additives used in the COST No. R-3 well--------------

Correlations between the COST No. ~-3 well and USGS 

Seismic Line 25------------------------------------------

v 

Page 

18 

25 

27 

87 

89 

94 

103 

110 

Geological Studies of the COST No. B-3 Well, 

United States Mid-Atlantic Continental Slope Area 

By Peter A. Scholle, Editor 

ABSTRACT 

The COST No. B-3 well is the first deep 

stratigraphic test to be drilled on the 

Continental Slope off the Eastern United 

States. The well was drilled in 2,686 ft (819 

m) of water in the Baltimore Canyon trough area 

to a total depth of 15,820 ft (4,822 m) below 

the drill platform. It penetrated a section 

composed of mudstones, calcareous mudstones, and 

limestones of generally deep water origin to a 

depth of about 8, 200 ft ( 2, 500 m) below the 

drill floor. Light-colored, medium- to coarsegrained sandstones with intercalated gray and 

brown shales, micritic limestones, and minor 

coal and dolomite predominate from about 8,200 

to 12,300 ft (2,500 to 3,750 m). From 12,300 ft 

(3,750 m) to the bottom, the section consists of 

limestones (including oolitic and intraclastic 

grainstones) with interbedded fine- to mediumgrained sandstones, dark-colored fissile shales, 

and numerous coal seams. 

Biostratigraphic examination has shown that 

the section down to approximately 6,000 ft 

(1,830 m) is Tertiary. The boundary between the 

Lower and Upper Cretaceous sections is placed 

between 8,600 and 9,200 ft (2,620 and 2,800 m) 

by various workers. Placement of the JurassicCretaceous boundary shows an even greater range 

based on different organisms; it is placed 

variously between 12,250 and 13,450 ft (3, 730 

and 5,000 m). The oldest unit penetrated in the 

well is considered to be Upper Jurassic 

(Kinnneridgian) by some workers and Middle 

Jurassic (Callovian) by others. The Lower 

Cretaceous and Jurassic parts of the section 

represent nonmarine to shallow-marine shelf 

sedimentation. Upper Cretaceous and Tertiary 

units reflect generally deeper water conditions 

at the B-3 well site and show a general 

transition from deposition at shelf to slope 

water depths. 

Examination of cores, well cuttings, and 

electric logs indicates that potential 

1 

hydrocarbon-reservoir units are rresent 

throughout the Jurassic and Cretaceous 

section. Porous and moderately permeable 

limestones and sandstones have been found in the 

Jurassic section, and significant thicknesses of 

sandstone with porosities as high as 30 percent 

and permeabilities in excess of 100 md have been 

encountered in the Cretaceous interval from 

about 7,000 to 12,000 ft (2,130 to 3,650 m). 

Studies of organic geochemistry, vitrinite 

reflectance, and color alteration of visible 

organic matter indicate that the Tertiary 

section, especially in its upper part, contains 

organic-carbon-rich sediments that are good 

potential oil source rocks. However, this part 

of the section is thermally immature e~d is 

unlikely to have acted as a source rock anywhere 

in the area of the B-3 well. The Cretaceous 

section is generally lean in organic carbon, the 

organic matter which is present is gen~rally 

gas-prone, and the interval is thermally 

immature (although the lowest part of this 

section is approaching thermal maturity). The 

deepest part of the well, the Jurassic se~tion, 

shows the onset of thermal maturity. The lower 

half of the Jurassic rocks has high organiccarbon contents with generally gas-prone organic 

matter. This interval is therefore considered 

to be an excellent possible gas source; it has a 

very high methane content. 

The combination of gas-prone source rocks, 

thermal maturity, significant gas shows in the 

well at 15,750 ft (4,801 m), and porous 

reservoir rocks in the deepest parts of tl~ well 

indicate a considerable potential for gas 

production from the Jurassic section in tl~ area 

of the COST No. B-3 well. Wells drilled farther 

downslope from the B-3 site may encounte:r more 

fully marine or deeper marine sections tl .'!t may 

have a greater potential for o'il (rather than 

gas) generation. 
EXPLANATION 

C;:J LEASE SALE NO. 49 

0 LEASE SALE NO. 40 

o SELECTED DRILL HOLES 

U ·S G S SEISMIC LINES 

0 25 50 100 KM 

2 

AM COR 

0 6020 

"'(S.DSDP 107 

ASP 15 ..... ,, .......... ............ ...... 

... , 
<J 

INTRODUCTION 

Until the completion of the COST 

(Continental Offshore Stratigraphic Test) No. B3 well, the first deep-penetration well to be 

drilled on the u.s. Atlantic Continental Slope, 

information about this region was extrapolated 

from onshore wells, offshore bottom sampling or 

shallow coring, geophysical surveys, or the COST 

No. B-2 well (Scholle, 1977), located more than 

32 statute miles (52 km) north of the B-3 site 

(fig. 1). The COST No. B-3 well was drilled 

between October 9, 1978, and January 25, 1979, 

in 2,686 ft (819 m) of water to examine the 

petroleum potential of the section seaward of 

the B-2 well. The well was drilled using the Ben 

Ocean Lancer, a dynamically positioned drill 

ship, and Chevron USA, Inc. acted as the 

operator for an 11-company COST-well group. The 

hole was drilled on the present-day Continental 

Slope, approximately 93 statute miles (150 km) 

southeast of Atlantic City, N.J. at lat 38° 55' 

00.655"N. long 72° 46' 22.578"W. (fig. 1). The 

well reached a total depth of 15,820 ft (4,822 

m) below the Kelly Bushing (KB), equivalent to a 

penetration of 13,092 ft (3,990 m) of section 

below the sea floor. The well is located offstructure but directly adjacent to the area 

offered for leasing on February 28, 1979, as 

part of Lease Sale No. 49. The granting of 

Federal leases within 50 nautical miles (93 km) 

of the B-3 drill site on May 1, 1979, has made 

possible the publication of detailed information 

about the geological findings from the COST No. 

B-3 well. Leasing stipulations provide for 

public disclosure by the u.s. Geological Survey 

(USGS) of all geological information on the well 

60 days after such leasing. 

Considerable basic operational, lithologic, 

stratigraphic, and geochemical data, most of it 

derived from industry reports, have been 

released previously (Amato and Simonis, 1979). 

This circular summarizes some of that data and 

adds information from other studies conducted by 

the USGS. It is by no means an exhaustive or 

completed program, but because the COST No. B-3 

well has such immediate interest for both the 

petroleum industry and academic workers, we 

believe that publication of such preliminary 

results is justified. 

The publication is divided into sep~rately 

authored sections on geological, geoch~mical, 

and geophysical topics. Environmental or 

operational details are not included af' these 

have been amply described by Amato and Simonis 

(1979). A brief synthesis of all available data 

is presented in the section ''Data Summary and 

Petroleum Potential." Much of the basic data 

will also be available in chart form (Scholle 

and others, 1980). 

All results reported in this pap~r were 

based on analysis of rotary-drill cuttings, 

supplemented in only a few cases by conventional 

or sidewall cores. Electric logs ard 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 commonly 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 KB, which was 42 ft 

(12.8 m) above mean sea level and 2,728 ft (831 

m) above the sediment-water interface. 

ACKNOWLEDGMENTS 

Technical assistance in sample prero:~.ration 

was provided by Frederick Zihlman. Other 

technical help came from Denise Irlan~o, Kim 

Schwab, Peggy Hempenius, Patty Forrestel, and 

Doris Low. Raymond E. Hall assisted in analysis 

of the Neogene planktic faunas, and William H. 

Abbott analyzed the diatom biostratigraphy and 

paleoecology in several core holes. William 

Fairchild and Rod Pickett kindly arran<:>:ed for 

the examination of the foraminiferal assemblages 

from sidewall cores of the COST No. B-3 well. 

Clyde Kelly and Robert Hohman of Geophysical 

Services, Inc. provided assistance during all 

stages of the advanced processing of Line 25, 

and William Patterson served as tte USGS 

representative during most phases of the 

acquisition and processing of these data. Page 

Valentine, John Schlee, c. Wylie Poag, and John 

Grow read various chapters and provided valuable 

suggestions. Michael Arthur and Richard Q• 

Foote reviewed the entire manuscript, an 

undertaking for which they are greatly thanked. 

Figure 1.--Location of selected wells, u.s. Geological Survey seismic-reflection grid, and the 

lease blocks involved in Oil and Gas Lease Sales No. 40 and 49 in the Baltimor~ Canyon 

trough area. Abbreviations used for wells, but not explained in the text, are as 

follows: DSDP (Deep Sea Drilling Project), ASP (Atlantic Slope Project), and AMCOR 

(Atlantic Margin Coring Project). 

3 
GEOLOGIC SETTING AND HYDROCARBON 

EXPLORATION ACTIVITY 

Robert E. Mattick and Kenneth c. Bayer 

'lbe COST No. B-3 well is located offshore 

from New Jersey on the present-day Continental 

Slope at a water depth of 2,686 ft (818.7 m) 

(fig. 1). 

In this area, basement rocks have subsided 

to depths of 12 mi (20 Ian) within an elongated, 

seaward-opening basin called the Baltimore 

Canyon trough (fig. 2). Analyses of seismic 

data indicate that maximum subsidence in the 

Maryland-Delaware-New Jersey offshore area 

occurred beneath the Outer Continental Shelf and 

Slope offshore from New Jersey (fig. 2). 

According to Schlee and others (1979), 

irregularities in the isopach pattern toward 

Long Island, N.Y., and Cape Hatteras, N.C. 

reflect a block-faulted basement surface where 

the basin merges with the Long Island Platform 

to the northeast and the Carolina Platform to 

the southwest. 

Figure 3 shows a cross section from the 

Coastal Plain of New Jersey to the COST No. B-3 

well. On the Coastal Plain of Virginia, 

Maryland, Delaware, and New Jersey more than 

6,500 ft (2,000 m) of Mesozoic through Cenozoic 

sedimentary rocks have been penetrated in 

numerous wells. These sedimentary rocks lie 

with marked unconformity on Paleozoic and 

Precambrian(?) metamorphic rocks and Triassic 

redbeds, basalts, and intrusives. The oldest 

post-Triassic sediments drilled on the Coastal 

Plain north of North Carolina are thin, 

unfossiliferous conglomerates, arkosic sandstones, and red claystones and shales. The age 

of these arkosic sandstones and redbeds is 

contToversial (Perry and others, 1975), but they 

were identified by Brown and others (1972) as 

being Jurassic. 

The Cretaceous stratigraphy of the Coastal 

Plain sediments is shown in figure 4. In the 

Island Beach well (fig. 3), Lower Cretaceous 

sedimentary rocks consist almost entirely of 

fluvial facies containing angular to subangular 

sandstones, siltstones, and silty claystones of 

the predominantly nonmarine Potomac Group (Perry 

and others, 1975). Upper Cretaceous sediments 

penetrated in the Island Beach well belong to 

the Raritan and Magothy Formatiors and the 

Matawan and Monmouth Groups (fig. 4). The 

Raritan Formation is chiefly of marine origin 

along coastal New Jersey (Owens and Sohl, 

1969). Unconformably overlying the Raritan 

Formation is the Magothy Formation, which 

consists of coarse beach sands and interbedded 

marine and lagoonal deposits (Owens and others, 

1968; Owens and Sohl, 1969; Spoljaric, 1972; 

Perry and others, 1975). The overlying Matawan 

and Monmouth Groups consist of a cyclic sequence 

of nearshore-marine deposits (Perry and others, 

1975). 

Eocene and Paleocene sedimentary rocks on 

the Coastal Plain of Maryland, Delaware, and New 

Jersey consist of a sequence of claystones and 

sandstones of shallow-marine origin (Poag, 

1980). In the Island Beach well (fig. 3), 

Oligocene sediments are missing below a major 

middle Tertiary unconformity (M~ttick and 

others, 1975). Recent field work, h~wever, has 

revealed that upper Oligocene sediments crop out 

along the Pamunkey and Chicahoming Rivers in 

Virginia (Poag, 1980). Miocene sediments 

consist of shelly sand interspersed with clay 

beds of shallow- or marginal-marine origin, and 

post-Miocene strata consist chiefly of coarse to 

fine, shelly sand and silty clay deposited in 

nonmarine and marginal-marine e,vironments 

(Poag, 1980). 

Comparison of onshore well data with the 

data from the COST Nos. B-2 and B-3 wells 

indicates a major thickening, in ~n offshore 

direction, of time equivalent rock units--

especially Upper Jurassic sediment~ that are 

less than 250 ft (80 m) thick in the Island 

Beach well and may be more than 4,000 ft (1,200 

m) thick in the COST No. B-2 well (fiq. 3). The 

seaward increase in section is b~lieved to 

reflect subsidence of basement rocks along a 

Figure 2.--Isopach map showing total thickness of sedimentary rocks from sea floor to acoustic [> 

basement in the Baltimore Canyon trough region. Contour interval is 3,28(' ft (1,000 

m). Locations of the seismic lines, used in compiling the map, are shown in figure 1. 

4 
EXPLANATION 

--200m-- I so bath shown for 200 and 2000 m 

0 Well location. See Figure 1 for 

well names. 

0 25 50 lOOkm I I I I I I 

5 
U .S.G.S. 

#1 

ISLAND BEACH 

TO 

63 K m 

~CONGLOMERATE~CALCAREOUSCLAY ~ ~ (MARL) 

OsANDSTONE 

r=;=!SHAL Y 

~SANDSTONE 

~SILTSTONE 

~CLAY 

~MUDSTONE 

5)sHALE 

.COAL 

•

INDURATED 

SHALE 

i&SHALY 

DOLOMITIC 

LIMESTONE 

~LIMESTONE 

~OOLITIC 

~LIMESTONE 

~SHALY 

~LIMESTONE 

~FOSSIL! FEROUS 

~LIMESTONE 

lfa7l DOL OMI Tl C 

tm:.tJ LIMESTONE 

~DOLOMITE 

~ANYHDRITE 

r-:::::JIGNEOUS 

~BASEMENT ~ASS. 

R.I. .,.../'\._ 

CONN , ~~ .1 

/ 

9/ 

1/ IN DE X MAP I 

ATLANTIC/OCEAN 0 20 40 60 80 100km (\,./ I I I I ft I 1 I e I I 

,.J 

) ---Water depth ( 200 m) 

I 

I 

I 

6 

COST COST 

B-2 20 Km B-3 

TO 16,043 ft. 

DEPTH 

METERS 

-1000 

-500 

-2000 

-3000 

-1000 

-.cooo 

-5000 -1500 

-6000 

-2000 

-7000 

-8000 

-2500 

-9000 

-3000 

-1 0,000 

-11,000 

-3500 

-12,000 

-1 3,000 -4000 

-14,000 

-4500 

-1 s,ooo 

-5000 
hinge zone located near the coast (Mattick and 

others, 1974). The greatest subsidence probably 

occurred during Jurassic time as a hot, young 

Atlantic rift margin cooled to nearly presentday temperatures. 

Time-equivalent rock units, in general, 

become more marine in an offshore direction. 

Miocene sands and clays of shallow-marginalmarine origin on the Coastal Plain become part 

of a shelf progradational sequence deposited 

under deltaic and near-deltaic environments at 

the B-2 drill site (Poag, 1978). Oligocene 

deposits, absent on most of the Coastcl Plain, 

are represented by claystones deposited in outer 

shelf environments at the B-2 site (Poag, 

1977). Although Eocene and Paleocene deposits 

reflect a shallow-marine environment in the 

Island Beach well, Eocene deposits fro~ the B-2 

well consist of limestone deposited in water 

depths equivalent to those of the pr~sent-day 

GULF EUROPEAN SERIES INFORMAL MARYLAND & DELAWARE NEW JERSEY COAST POLLEN LONG ISLAND 

UNITS AND STAGES ZONATION SOUTH NORTH SOUTHWEST NORTHEAST 

llllll llilllll u llll ~AESTRICHTIAN lll!J-l--' J...- Red Bonk Sand '"'"" '''" 

I-- - Navesink Formation Monmouth Group 

Navarre Group Moomo~ ( un divide d) 

( undi vi de d) Mount Laurel Sand z UPPER ~ _____.s:- Wenonah Formation 

z 1\. M orsholl town F ormoti on Mot,1won Group .., ~ 

Taylor Marl ::::> a.. 1\ Eng I i shtown Formation 

C/) ( un divide d) 0 ~ Woodbury Clev UJ w ~ LOWER 

a: u u I\ ················ 1\ Merchantville Formation UJ ~ ZONE VII Cliffwood C/) 

lllllllllllllll 1-

w ~ . B~~~g~"ndBeds z 0::: 1'- Mogothy Formotoon . <( u SANTONIAN 1'-?-r-1'-r- Amboy Stoneware Cloy Member Mogot"yFormohon 

u: 0::: r- r-.-1'-r-r-,QI.!, Bridge Sand Member ....J Austin Chalk w ::> a.. ....... -? ...... l TI.~.h! 1~.~ u c!JWlli <!) a.. CONIACIAN 

11 fHlT ITm 1TI ::::> ? 

Eagle Ford ......... ?····· .. 

Shale ~~NIAN s.,, .. nle~,..!..,. ?__/ ZONE V 

··············· Woodbridge "'-?- . l£!.2l:. Member _r7 Rofl ton '• Woodbine Formation ZONE IV Farrington 

Formation CENOMANIAN I(_ 0 Sand Member -7- ················ ....J..o-V'""' '----~---1--------

Woshite ZONE Ill ~v'--- "Rantan fire clay" 

················ '?.....,._a-.... Group c ~'? ....... C/) 

UJ ····· V' a: Fredericksburg POTOMAC UJ Group (/) ZONE II B 

z ALBIAN Petopsco Formation <( ... UJ .., A I ::::> 

u 0 ················· z w ("""A run dell <( Trinity Group u ZONE I ? Formation ? 

~ ~ 

1- 0 w u 0::: 

u Patuxent 

0::: Formation w 

~ APTIAN 

0 

z /~ Nueve Leon ...1 

<CCI) Group 7 ::::!UJ 

::>-

III: 

<(UJ 

0(/) Duren go NEOCOMIAN 

u Group 

Figure 4.--Correlation chart of outcropping and shallow-subsurface Cretaceous stratigraphic units 

in Maryland, Delaware, New Jersey, and Long Island, N.Y. From Perry and others (1975). 

<] Figure 3.--Geological cross section of the Baltimore Canyon trough. Modified from Adinolfi and 

Jacobson (1979, pl. 4). 

7 
Continental Slope (Smith and others, 1976). 

Upper Cretaceous nearshore shales, beach 

sandstones, and shales deposited in estuarine to 

shallow-water environments change to generally 

marine shales and mudstones (Poag, 1977) 

deposited in outer shelf environments (Smith and 

others, 1976) in the direction of the B-2 

well. The Potomac Group is represented by 

fluvial sandstones on the Coastal Plain; 

however, during Albian and Aptian time a shallow 

sea occupied the B-2 site (Poag, 1977). 

Onshore, basal Lower Cretaceous and Upper 

Jurassic sedimentary rocks are represented by 

continental deposits of arkosic sandstones and 

redbeds. Apparently, during this time, much of 

what is now the Continental Shelf was at or 

above sea level and was only intermittently 

submerged. According to Poag (1977), basal 

Lower Cretaceous and Jurassic beds at the B-2 

site consist primarily of continental deposits, 

as evidenced by the rare occurrence of marine 

fossils, abundance of coal beds and terrestrial 

plant remains, and presence of nonmarine 

sandstone and shale beds that accumulated under 

subaerial conditions. 

Comparison of data from the COST No. B-3 

well with data from the COST No. B-2 well by 

Amato and Simonis (1979, P• Ill) indicates that 

the entire section is more marine at the COST 

No. B-3 well site. Below about 12,400 ft (3,780 

m) in the COST No. B-3 well, Upper Jurassic 

sandstone, limestone, shale, and coal were 

deposited in nearshore-tidal-flat to outer shelf 

environments (Amato and Simonis, 1979, P• 

111) • The uppermost part of the sequence also 

contains oolitic limestone thought to have been 

deposited in a tidal-bar environment (Schlee, 

Mattick, and others, 1979, P• 8). During 

Jurassic time, therefore, the Continental Shelf 

must have extended farther seaward than the 

present-day shelf. On the basis of seismic 

data, Mattick and others (in press) show the 

Jurassic shelf edge located about 20 mi (30 km) 

seaward of its present position. 

The pre-Upper Jurassic stratigraphy of the 

Baltimore Canyon trough is inferred from seismic 

data (Mattick and others, 1975; Sheridan 1976; 

Schlee and others, 1976; Mattick and others, 

1978; Schlee, Mattick, and others, 1979; Bayer 

and Mattick, 1980) and by analogy with the 

Continental Shelf off Nova Scotia on which 

exploration wells have penetrated Middle 

Jurassic strata (Mciver, 1972; Jansa and Wade, 

1975; Given, 1977; Adinolfi and Jacobson, 

1979). On the basis of Common Depth Point (CDP) 

seismic velocities, the Upper Jurassic clastic 

sequence penetrated at the bottom of the COST 

Nos. B-2 and B-3 wells is thought to overlie a 

thick sequence of Lower Jurassic (or Triassic?) 

to Middle Jurassic interbedded limestone, 

dolomite, and evaporite (including salt) in the 

basal part of the section. The Houston Oil and 

Minerals 676-1 wildcat well penetrated salt at a 

depth of about 12,500 ft (3,810 m) in the 

vicinity of a basaltic(?) intrusion in the 

8 

central Baltimore Canyon trough area where a 

thick, uplifted section of Upper Jurassic rocks 

was removed by erosion. The carbonate-evaporite 

sequence would correspond lithologically and 

chronostratigraphically to the Iroquois 

Formation and the salt to the Argo Formation 

(Adinolfi and Jacobson, 1979). Beth of these 

formations have been drilled on the Continental 

Shelf, offshore from Nova Scotia, Canada. 

According to Jansa and Wade (1975) and Given 

(1977), the salt (Argo Formation) w~s deposited 

in restricted basins of rift-valley origin, and 

the dolomite-evaporite sequence (Iroquois 

Formation) represents a marine transgression 

prior to the opening of the Atlantic. Bayer and 

Mattick (1980), however, speculate that the 

evaporites in the Baltimore Canyon trough were 

deposited in a narrow, shallow, early Atlantic 

sea. Internal velocity data s·•ggest that 

shoreward of the COST No. B-2 well, the 

limestone, dolomite, and evaporite sequence 

grades into a clastic sequence of sa~dstones and 

shales. This Lower Jurassic (Triassic?) to 

Middle Jurassic clastic sequence would be 

equivalent to Mohican Formation p€netrated on 

the Nova Scotia shelf. 

Basement rocks underlying the sedimentary 

wedge in the Baltimore Canyon trough area are 

thought to be of two types: continental and 

oceanic. The juncture of these rcr.k types is 

believed to be represented by the East Coast 

Magnetic Anomaly (Grow and Klitgora, in press, 

fig. 24), which parallels the Continental Shelf 

margin in the central Baltimore Cenyon trough 

area; the COST No. B-2 well (fig. 1) lies on or 

very close to this juncture. Oceanic basement 

rocks (basalts) were presumably emplaced as the 

African and North American continental plates 

separated during Triassic or Early Jurassic 

time. Continental basement rocks e-re probably 

metamorphic rocks of Paleozoic age. Paleozoic 

rocks, moderately to strongly metamorphosed, 

occur east of the Blue Ridge Mount a ins, in New 

England, Nova Scotia, and locally in the 

crystalline Piedmont south of New York. In 

addition, generally flat-lying Paleozoic 

sedimentary rocks showing little or no 

metamorphism are present beneath the Coastal 

Plain south of Cape Hatteras, Nor':h Carolina 

(Applin, 1951). The continental baF~ment rocks 

are believed to have been broken up into a 

~er~es of horsts and grabens during initial 

phases of rifting, and nonmarine "re~ beds" were 

deposited locally in resulting low-standing 

areas. In outcrop onshore, these r~d beds are 

represented by a heterogeneous mixture of stream 

and lake deposits plus intrusive an1 extrusive 

volcanic rocks. 

A columnar section that summ~rizes the 

geology of the Outer Continental Shelf and Slope 

in the Baltimore Canyon trough area is shown in 

figure s. Of special interest for tre petroleum 

geologist are possible Mesozoic shelf-edge reef 

deposits associated with a Jurassic-Lower 

Cretaceous carbonate bank buildup. Shelf-edge 
~~·· . ·~ ~· • • • • 

·~~·~· . . . . . 

... ~ ·~ . . ~ . . . . 

• • • 

• • • 

• 

• 

+ 

++ 

+t+ 

+++ 

+-+++++++ 

Tertiary (chiefly Miocene);900 m thick in COST B-2 well; deltaic 

sand of shelf progradational sequence in mid-shelf area; shale i[] 

outer shelf and slope deposited under outer shelf and upper slope 

environments • 

Lower Tertiary and Upper Cretaceous transgressional sequence; 

1,400 m thick in COST B-2 well; chiefly shale, calcareous claystone, and limestone deposited under outer shelf and slope 

environments. 

Lower Cretaceous; 1,100 m thick in COST B·3 well; interbedded ~andstone and shale, shale increasing seaward; represents an influx of 

sand and mud that built prograding deltaic wedges • 

Upper and Middle Jurassic; minimum thickness is 1,400 m as penetrated 

in bottom of COST B·2 well; chiefly nonmarine sandstone and shale 

containing lignite beds; changes seaward to limestone and dolomite,, which 

represent carbonate-bank buildup beneath present outershelf anc slope; 

coralgal reef material at paleoshelf margin located 20·30 km seaward 

of present shelf edge. 

Middle and Lower Jurassic; by analogy with the Scotian Shelf (Given, 

1977) this sequence consists of sandstone grading seaward to dolomite 

and evaporite facies (deposited in a sabkha environment) to dolomitized, 

oolitic and pelletoidal grainstone facies. 

Lower Jurassic salt of unknown thickness beneath middle and outer 

shelf area; probable time equivalent of Argo Salt of the Scotian Shelf. 

Triassic(?) nonmarine lake and swamp deposits of unknown thickness; consists of red shale, siltstone, sandstone, and fanglomerate 

deposited in downdroppcd grabens. Continental and oceanic base• 

ment rocks having gradational contact that underlies outer-shelf 

in Baltimore Canyon Trough. 

Figure s.--Generalized columnar section showing lithologic units present and inferrerl to be 

present in the Baltimore Canyon trough. Section below the Upper Jurassic is based on 

geophysical interpretation and analogy with the Continental Shelf offshore from Nova 

Scotia. Basement intrusions at the shelf margin have been inferred by Schlee, Mattick, 

and others (1979) on the basis of magnetic interpretation. Other authors have inferred 

a shallow basement surface at the shelf margin. 

9 
carbonate buildups were predicted by Mattick and 

others (1978) on the basis of seismic data. The 

increase in amount of limestone and dolomite 

from the B-2 to the B-3 well appears to confirm 

the interpretation that the Mesozoic shelf 

margin was dominated by carbonate rocks 

(Simonis, 1979, P• 104). Petroleum could have 

been generated in organic-carbon-rich Mesozoic 

basin facies and have migrated essentially 

updip, but possibly down section, to reefal 

reservoir rocks of the Mesozoic shelf margin. 

Mattick and others (1978) compared the Mesozoic 

shelf-margin complex to the productive back-reef 

facies of the Cretaceous Edwards Limestone of 

Texas and the reef and fore-reef trend of the El 

Abra-Tamaulipas Formation of the Golden Lane and 

Poza Rica trends in Mexico. However, Simonis 

(1979, P• 105) noted that this comparison must 

be tempered by the lack of discoveries in the 

Upper Jurassic Abenaki Formation (carbonate 

unit) of the Scotian Shelf in Canada and by the 

fact that oolitic limestone penetrated in the 

COST No. B-3 well had porosities of less than 8 

percent and permeabilities of less than 0.1 md. 

Wildcat drilling in the Baltimore Canyon 

trough, which started in March 1978, has been 

concentrated in the vicinity of the Great Stone 

Dome (fig. 2) and in a narrow strip along the 

shelf edge. The Great Stone Dome, a large domal 

structure (fig. 2) inferred to be associated 

with an Early Cretaceous mafic intrusion, 

appeared to be the largest and most promising 

single structure on the shelf. Six wells (fig. 

6) were drilled on the structure, and all were 

plugged and abandoned with no oil or gas shows 

reported. 

Fifteen additional wells, including the two 

COST wells, have been completed along the 

shoreward edge of the Continental Shelf (fig. 

6) • Hydrocarbon shows have been reported from 

four of these wells. The first discovery was 

made by Texaco on Block 598. In initial tests, 

the Texaco 598-1 well flowed natural gas at the 

rate of 7.5 million ft3 (210,000 m3) per day 

from a 38-ft (11.6-m) interval below 14,000 ft 

(4,270 m); and a second interval of 40 ft (12.2 

m), below a depth of 13,000 ft (3,960 m), flowed 

natural gas at the rate of 9.4 million ft3 

(270,000 m3) per day (J. c. Hathaway, u.s. 

Geological Survey, written communication, 

1979). A confirmation well, Texaco's 598-2, 

located about 1 mi (1.5 km) west was reported as 

dry. In May 1979, Tenneco, referring to their 

642-2 well, announced that natural gas flowed 

from a 14-ft (4.3-m) interval in Jurassic 

sandstone at about 13,190 ft (4,020 m); the 

initial flow rate was 12 million ft3 (340,000 

m3) of natural gas and 100 barrels of condensate 

per day. Another zone at about 12,650 ft (3,860 

m) flowed natural gas at the daily rate of 1 

million ft3 (28,000 m3) and 500 barrels of salt 

water. An additional zone at about 8, 315 ft 

( 2, 5 35 m) flowed 48. 4 ° API gravity oil at the 

rate of 630 barrels per day from a thin Lower 

Cretaceous sandstone. In reference to the 642-1 

10 

well, Texaco announced (October, 15'79) that it 

flowed natural gas at a rate 5.5 million ft3/day 

(156,000 m3/day) and condensate at a rate of 18 

barrels per day from an interval below 15,480 ft 

(4,720 m). Two additional zones, at 12,720 ft 

(3,879 m) and 12,990 ft (3,962 m), were tested 

in November 1979. The resfective dail3 flow 

rates were 18.9 million ft (536,000 m ) and 

14.2 million ft3 (402 ,000 m3) of nat·~ral gas. A 

show of natural gas was reported f1·om the COST 

No. B-3 well in the interval fron · 15,744 ft 

(4,798.8 m) to 15,752 ft (4,801.2 m) (Scholle, 

this volume). 

Although natural gas shows to date have 

been significant, a commercial fielc has yet to 

be announced. Crawford (19 78) has estimated 

that it would require a daily flow of about 200 

million ft3 (5. 7 million m3) and reserves of 

about 1.2 trillion ft3 (34 billion m3) of 

natural gas to establish a profit-yielding 

commercial field in the Baltim':lre Canyon 

trough. Oil companies may be disappointed by 

their initial lack of success in the u.s. 

Atlantic. In August 1976, during the first East 

Coast offshore sale, industry bid 1.1 billion 

dollars for the rights to explore 93 (fig. 1) 

tracts offshore from New Jersey (fig. 1). In 

February 1979, however, industry bid only 41.7 

million dollars on 44 of 109 (fig. 1) tracts 

offered for lease in the same area. 

Sparce seismic data indicate that the 

Texaco discovery (598-1) is associated with 

closure above a pillow (salt?) structure located 

on the downthrown block of a large growth 

fault. The strata at discovery depths are 

complexly faulted. According to Mattick and 

others (1980), local salt movement on the shelf 

could be related to movement along growth faults 

which are oriented parallel to the Continental 

Shelf and which are common on the shelf 

margin. Two wells (Exxon's 684-1 and 684-2, 

fig. 6), drilled on a similar pillow (salt?) 

structure 9 mi (15 km) southwest of the Texaco 

discovery, however, were plugged, abandoned, and 

reported as dry holes (J. c. Hat;away, u.s. 

Geological Survey, written communication, 1979). 

A summary of the petroleum geolcgy prior to 

the drilling of the COST No. B-3 well is as 

follows: Results from seismic aralysis and 

exploratory drilling have indicated that the 

shelf margin, as compared to the mid-shelf area, 

offers better possibilities for further 

exploratory work. Traps are expected to involve 

relatively complex structures. Analyses of data 

from the COST No. B-2 well indicate that 

conditions for the generation and entrapment of 

natural gas in Jurassic sediments are favorable 

(Scholle, 1977, P• 14). On the Continental 

Shelf, Lower Cretaceous and Jurassic sandstones 

offer the best reservoir possibilities. The 

sandstone porosity values are small below 12,000 

ft (3,700 m) because of a breakdown of feldspar 

and generation of calcite cement (Sch':llle, 1977, 

P• 8); but, locally, thin porous sandstone 

layers persist to depths of at least 16,000 ft 
40°00' 

1 Dry 

500-1 0 

544-1 -<>- 590•1 

632-1 -¢- -¢-

718-1-<>- -¢-676·1 

EXPLORATORY WELLS 

-¢- DRY HOLE 

Q SHOW OF GAS 

• SHOW OF OIL AND GAS 

0 DRILLING WELL 

0 10 20 30 km 

I I I 

73 ° 00' 

Figure 6.--Locations of deep exploratory wells drilled in the Baltimore Canyon trough. 

11 
(4,900 m) and these have flowed natural gas in 

at least two wells. Seismic data suggest that 

Jurassic carbonate rocks, which could be 

potential reservoirs, exist at depth on the 

Continental Slope. Although comparison with the 

Abenaki Formation (Middle to Late Jurassic age) 

of the Scotian Shelf would suggest that these 

carbonate units are usually tight, the Shell 

Demascota G-32 well, drilled as a shelf-edge 

test on the Scotian Shelf, penetrated 551 ft 

(168 m) of porous dolomites and limestone 

(including coralgal reef carbonates) with 

porosity values as large as 14 percent in the 

limestone and fracture porosities of unknown 

12 

magnitude in the dolomite (Given, 1977, P• 

74). In addition, on the Scotian Shelf, a 

variety of porosity types exist in the Iroquois 

dolomite (Early to Middle Jurassic) with values 

as large as 15 percent and oil staining reported 

in several wells (Given, 1977, P• 71). Whether 

or not such reservoirs are located on the 

paleoshelf margin in the Baltimore Canyon trough 

near the lower part of the present slope and 

whether those reservoirs could have been charged 

with liquid hydrocarbons generatrd in nearby 

basin facies are not known. The discovery of 

oil in the Tenneco 642-2 well, however, lends 

some weight to these possibilities. 
DATA SUMMARY AND PETROLEUM POTENTIAL 

Peter A. Scholle 

The COST No. B-3 well penetrated 13,092 ft 

(3,990 m) of Tertiary to Jurassic section. 

Lithologic, biostratigraphic, and paleoenvironmental studies, summarized in figure 7 

and table 1, indicate that the section from 

3,810 ft (1,161 m) (the shallowest sample 

recovered in this well) to about 6,000 ft (1,830 

m) consists of Miocene to Eocene calcareous 

clays, chalks, and shales. The entire interval 

represents deep-water sedimentation at outermost 

shelf to lower slope water depths. 

Nevertheless, significant hiatuses are present 

below the Eocene, within the Oligocene, and 

within or at the base of the Miocene. These 

presumably reflect submarine rather than 

subaerial erosional events. 

Below a major unconformity at 6,020 ft 

(1,835 m) at which the entire Paleocene and part 

of the Maestrichtian were missing, Upper 

Cretaceous sediments are present down to a depth 

of about 9,000 ft (2, 750 m). This section 

contains calcareous mudstones, glauconitic 

sandstones, and dolomitic limestones; it shows a 

progressive change in paleoenvironments of 

deposition from outer shelf or upper slope 

depths at the top to inner shelf or middle-shelf 

depths at the base. Unconformities have been 

reported from several horizons within the lower 

part of this section. The exact placement of 

the base of the Upper Cretaceous varies among 

workers. Poag (this volume) places the boundary 

at 9,170 ft (2,795 m) on the basis of studies of 

foraminifers; Valentine (this volume) places it 

at 8, 900 ft (2, 713 m) on the basis of 

nannofossils; and Steinkraus (1979) placed it at 

8,690 ft (2,649 m) on the basis of a suite of 

microfloral and microfauna! studies (table 1). 

Conformably underlying the Upper Cretaceous 

section is a thick interval of Lower Cretaceous 

sediments. These sediments contain interbedded 

sandy shales, sandstones, and micritic 

limestones with small amounts of coal, all 

deposited mainly in inner shelf to marginalmarine conditions. One hiatus has been 

recognized between the Hauterivian and Barremian 

sections, and it may have involved subaerial 

exposure (Poag, this volume). The base of the 

Lower Cretaceous is placed at 12,400 ft (3, 780 

m) by Steinkraus (1979); at 12,260 ft (3,737 m) 

13 

by Poag (this volume); and at 13,450 ft (4,100 

m) by Valentine (this volume). Thus, in the B-3 

well, as in most wells along the Atlantic w~rgin 

of the United States, considerable disagreement 

exists about the exact placement of the 

Jurassic-Cretaceous boundary. 

The underlying section, to the base cf the 

well at 15,820 ft (4,822 m), is considered to be 

Jurassic. This interval contains shales and 

sandy shales with interbedded limestones, 

subordinate sands tones, and coal beds. 

Deposition was apparently in nonmarin?. to 

shallow-marine, inner shelf conditions. 

Steinkraus (1979) and Valentine (this vclume) 

identified the entire section to the base of the 

well as Upper Jurassic, but Poag (this vclume) 

has recognized a Callovian(?) fauna ir the 

interval from 15,390 to 15,820 ft (4,691 to 

4,822 m) and thus considers the well to l,"lttom 

in the Middle(?) Jurassic. 

The biostratigraphic results for the COST 

No. B-3 well, summarized in table 1, indicate 

close agreement between all workers or. the 

placement of the Cretaceous-Tertiary bot·ndary 

and the series boundaries within the Tertiary. 

The disagreement on the placement of other 

boundaries increases, however, with increasing 

geologic age. Thus, there is a spread of about 

500 ft (150 m) in the interpretation of the 

Lower Cretaceous-Upper Cretaceous boundary and a 

spread of nearly 1,200 ft (365 m) for the 

Jurassic-Cretaceous boundary. Better biostratigraphic standards and further studies are 

needed to reduce such differences. 

Sedimentation rates of v~rious 

stratigraphic units are discussed by Poag (this 

volume). Jurassic rates range from 2.1 to 3.1 

in./1,000 yrs (5.4 to 7.8 cm/1,000 yrs). Rates 

for the Lower Cretaceous sediments V9.ried 

between 0.8 and 1.5 in./1,000 yrs (2.1 and 3.8 

cm/1 ,000 yrs), except in the Valanr:inian 

interval which had rates of 2.8 to 3.2 in./1,000 

yrs (7.0 to 8.1 cm/1,000 yrs). Upper Cret?ceous 

sediments were deposited at rates that V9.ried 

from as low as 0.5 in./1,000 yrs (1.3 cm/1,000 

yrs) in the Maestrichtian to as high as 4.1 

in./1,000 yrs (10.5 cm/1,000 yrs) in the 

Turonian. Tertiary rates at B-3 range from 0.4 

to 1.5 in./1,000 yrs (1.0 to 3.9 cm/1,000 yrs), 
SERIES 

MIOCENE 

OLIGOCENE 

EOCENE 

>-

(!) 

0 

....J 

0 

:r: 1-

:J DESCRIPTION 

Gray to wh1te calcareous 

claystone. 

i-.--'--r-..L-,.-'-~--1 L1ght gray to wh1te calcareous 

._,::C...,..d'~=l claystone w/locally abundant 

glaucon1te Layers of l1ght 

6f;:;b~~ to wh1te often very fossiliferous 

limestone 

Dark brown, purple and gray 

calcareous mudstone Interbedded 

P'-""'~..::.:;:..,~1 w1th glaucon1t1c sandstone and 

1-'--,---.,;--o-.;--;-e:,-;1 dolom1t1c l1mestone 

UPPER 

CRETACEOUS~~~~ 

LOWER 

CRETACEOUS 

UPPER 

JURASSIC 

Wh1te, quartz sandstone, m1nor 

shale 

Brown to off wh1te. oollt1c 

lli!!~liiillii 7;,~=~~e~~:ds:~: ~~~=~~one and 

m~nor sandstone Coal locally 

abundant 1n th1n layers 

:r:1-

l-ti1 

fuLL 

0~ 

14 

(/) 

I a: 1-w a..l- wW 

0~ 

~ 

50 

1000 

1500 

POAG 

this volume 

I 

r ... 

PALEOBATHYMETPY 

VALENTINE 

this volume 

\, 

r--

STEINKRAUS 

(1979) 
with a significant pulse in the middle Miocene 

of 3.2 in./1,000 yrs (8.0 cm/1,000 yrs). 

The porosity and permeability values of 

conventional and sidewall core samples from the 

COST No. B-3 well are shown in figure 8. 

Porosities of units in the Tertiary and Upper 

Cretaceous section, down to about 8,200 ft 

(2,500 m), vary between 20 and 32 percent. 

Corresponding permeabilities in these relatively 

fine-grained rocks are small, however. Only 

about 200 ft (60 m) of reservoir-quality 

sandstone was noted in this interval (Amato and 

Simonis, 1979). 

The Cenomanian and Lower Cretaceous 

interval between about 8,200 and 11,630 ft 

(2,500 and 3,550 m) contains many more sandstone 

units, and more than 1,000 ft (300 m) of 

sandstones with porosities of 16-24 percent have 

been reported for this interval (Amato and 

Simonis, 1979). 

The Lower Cretaceous and Upper Jurassic 

section from 11,630 ft (3,550 m) to the base of 

the well at 15,820 ft (4,822 m) contains thin 

sandstone units as well as numerous potential 

limestone reservoirs. Log analysis has defined 

an interval of approximately 140 ft (43 m) of 

sandstone with porosity values greater than 8 

percent (Amato and Simonis, 1979). Analysis of 

sidewall cores has shown even higher porosity 

values for sandstones in this section, averaging 

about 20 percent. Corresponding permeabilities, 

however, are quite small, averaging less than 10 

md., a reflection of probable diagenetic 

alteration of these units involving authigenic 

clay formation and possible secondary-porosity 

generation. Carbonate rocks in this basal 

interval of the well have moderately low 

porosities, generally below 10 percent, and 

permeabilities generally below 1 md. 

Impermeable beds, which could act as seals 

for hydrocarbon entrapment, are present 

throughout the section. The thick sequence of 

calcareous claystones, shales, and chalks from 

3,800 to about 6,200 ft (1,161 to 1,890 m), as 

well as thinner shale and impermeable limestone 

beds throughout the penetrated section, is the 

best potential seal. Furthermore, the 

significant differences in section between the 

B-3 and B-2 COST wells indicate that 

considerable lateral interfingering of 

sandstones and shales (on the landward side) and 

limestones (on the seaward side) is to be 

expected in this area. Thus, stratigraphic 

traps with updip permeability barriers are quite 

likely in this region. 

Temperature logs were not run on the B-3 

well, and so no precise value can be given for 

the present-day geothermal gradient in this 

area. Temperature data, taken from head~rs of 

other electric logs (fig. 9) run in this well, 

show an average geothermal gradient of 

1.26°F/100 ft (22.8°C/km) (Amato and Simonis, 

1979), which is similar to the value of 

1.30°F/100 ft (23.7°C/km) obtained for the 

nearby COST No. B-2 well (Scholle, 1977). This 

relatively low present-day geothermal gradient 

is also reflected in the rather low rate of 

thermal maturation of organic matter wit~ depth 

in the B-3 well. Two maturation :l'.ndices 

(vitrinite reflectance and visual kerogen) are 

presented in figure 9, and both show that the 

onset of thermal maturity occurs in the deepest 

part of the well, below about 15,000 ft (4,575 

m). 

In general, organic geochemical studies 

have shown that the Tertiary section in tl'~ COST 

No. B-3 well, down to approximately 6,000 ft 

(1,825 m), contains high concentrati0ns of 

organic matter (as much as 3 percent, ~'ith an 

average of about 1.5 percent) (Mill~r and 

others, this volume) • The kerogens in this 

interval are primarily marine, hydrogen-rich, 

oil-prone types that would indic~te a 

significant potential for oil generation. 

However, the very low degree of thermal 

maturation of organic matter in this interval 

(vitrinite reflectance values of o. 26 to o. 35 

percent, and thermal alteration index (TAl) 

values of 1.2 to 1.5; fig. 9) indicates that 

this sediment is not likely to act as an actual 

source rock unless it is much more deeply 

buried. The shallow gas occurrence in this well 

at about 4, 000 ft (1, 220 m) was predominantly 

methane of probable biogenic origin. 

The Cretaceous interval from approximately 

6,000 to 12,400 ft (1,841 to 3,780 m) contains 

dominantly humic, hydrogen-lean, gas-prone, 

exinite- and vitrinite-type kerogens with atomic 

hydrogen-to-carbon ratios of 0.6 to 0.8 (Miller 

and others, this volume). Total-organic-carbon 

contents are moderate, averaging under 1 

percent. An average carbon preference index 

(CPI) value of 1.5, a total hydrocar~on-toextractable-organic-matter ratio of 0.30 to 

0.52, low thermal-pyrolysis values (generally 

below 436°C), TAl values of 1.51, and vitrinitereflectance values of o. 35 to o. 39 percc.mt all 

indicate moderate thermal immaturity for this 

interval and poor hydrocarbon source pote~tial. 

The Jurassic interval from about 12,400 ft 

( 3, 780 m) to the base of the well has organicrichness characteristics that indicate mrlderate 

to good source-rock potential. The interval 

below 14,300 ft (4, 359 m), in particulEr, has 

<] Figure ].--Generalized plot of lithologies and comparison of depositional-environment assignments 

of sediments in the COST No. B-3 well. Environmental designations are as follow~: NM, 

nonmarine; IS, inner shelf; OS, outer shelf; USL, upper slope; MSL, middle slope; LSL, 

lower slope. Age assignments are from Amato and Simonis (1979); lithologic data from 

Pollack, this volume. 

15 
CORE FOROSITY (percent) PERMEABILITY (millidarcies) 

§ 

r 

10 

15 

- - 0 

0 0 ,... 0 

0 X ,... 20 - X • • • (/} 

- a: 

1- w 

w 1-

• w • w • • u. • ~ • • • • • ~ 25 

z •• • • • z 

• • • 

J: • J: • • 1- 1-

a.. • a.. 

w w 

Q '·' •• 30 Q 

• • • • • 

• • • 

• • )( .x • •• • • • • 35 • • 

• • , )( )( 

40 

• 

• • II( • l( ~ • 45 

• X •" " X. 

I X • 

)( X 

16 
high organic-carbon contents (some values in 

excess of 2 percent). The kerogens in this 

interval are predominantly gas-prone, hydrogenpoor, exinite and vitrinite types. "Below 

14,900 ft (4,542 m) the c 15+ liquid-hydrocarbongas chromatograms show a systematic decrease in 

the magnitude of the unresolved envelope and a 

relative increase in the concentration of the 

lower molecular weight, resolved, saturated 

paraffin-napthenes" (Miller and others, this 

volume). These factors, coupled with a 

significant increase in the concentration of c 1 

to c4 light hydrocarbons, increased gas-wetness 

values, and TAI values and vitrinite-reflectance 

percentages as high as 2.2 and 0.54, 

respectively, at the base of the well, all 

indicate that incipient thermal maturity is 

likely to have been reached in the basal section 

in this well. Indeed, the vitrinite-reflectance 

data reported by Core Laboratories (1979) for 

this well represent minimum values (based on 

cuttings). Vitrinite-reflectance studies of an 

in-situ coal from 15,570 ft (4,746 m) yielded R0 values of between 0.83 and 1.13 percent, values 

well within the range normally interpreted as 

indicating thermal maturity. The interval from 

about 15,000 ft (4,572 m) to 15,820 ft (4,822 m) 

is therefore considered to be an excellent 

potential gas source which is at or very near 

thermal maturity. The discovery of a 

"significant" gas show in the interval from 

15,744 to 15,752 ft (4,799 to 4,801 m) during 

the drilling of the B-3 well serves to confirm 

this evaluation. 

The presence of a thick column of 

sedimentary strata below the total depth of the 

B-3 well, coupled with the low geothermal 

gradient in the area and the marginal thermal 

maturity, indicates the possiblity of a thick 

section of rocks with petroleum-source 

possibilities below 16,000 ft (4,875 m) in this 

region. 

Essentially, five major factors are 

involved in the origin and entrapment of 

hydrocarbons: (1) source rocks, ( 2) 

temperatures sufficient to generate liquid or 

gaseous hydrocarbons, (3) porous reservoir 

rocks, (4) impermeable seals, and (5) structural 

and (or) stratigraphic traps. Indications from 

the B-3 well are that rocks of high organiccarbon content are present in the uppermost and 

lowermost parts of the total section 

penetrated. The upper interval is oil-prone; 

the lower is gas-prone. Rocks between these 

sections have lower organic-carbon contents and 

lower oil- or gas-generation potentials. 

Temperatures appear to have been sufficient 

for possible hydrocarbon generation in the 

deeper, gas-prone interval, below 15,000 ft 

~ .! 

.... 

w 

~ 

~ 

I 

.... 

Q. 

w 

0 

11 

16 

ORGANIC 

CARBON 

CONTENT 

(weoght percent) 

. ' ... .. 

. . . 

;· 

.• . 

.:· 

.. .. 

~ .. 

... '· i . 

"'• .. 

.. . 

PRIMARY 

VITRINITE 

REFLECTANCE 

(R 0 percent) 

. . 

~. 

TEMPERATURE 

("C) 

#U 

(OF) 

~ ~Iii~ i 

VISUAL 

KERC<:'\EN 

MATUR~TION 

I NO': X 

\ 

~ .! 

Ul 

0: 

w 

.... 

w 

~ 

~ 

I 

.... 

Q. 

w 

0 

Figure 9.--Comparison of various geochemical and 

thermal parameters as a function of 

depth in the COST No. B-3 well. 

Organic carbon content, primary 

vitrinite reflectance, and visual 

kerogen maturation data are frcm Core 

Laboratories (1979); well-bore 

temperature values are from Amsto and 

Simonis (1979). 

(4,572 m). The shallower, oil-prone interval is 

thermally immature and is not likely to have 

acted as a source rock. 

Potential reservoir rocks, particularly for 

gas deposits, are distributed throughout the 

lowe~ half of the section in the B-3 well. 

These rocks, sandstones and possibly also some 

limestones, have high porosities and moderate to 

low permeabilities. Reservoir units are present 

both within and immediately above the interval 

of maximum gas-generation potential (below 

15,000 ft; 4,572 m). Presumably, sandstone 

<J Figure B.--Porosities and permeabilities measured using conventional and sidewall cores from the 

COST No. B-3 well as a function of depth (data from Amato and Simonis, 1979). When 

numerous core measurements were available for short depth intervals, plotted values are 

averages and are shown by an X symbol. All other (nonaverage) values shown as d~ts. 

17 
0 

5· 

0• 

5 

0 

(/J 2 

a: 5 

w 

1-

w 

::!: 

~ 

J: 

li: 

w 

0 30 )• 

35 ;. 

40 ,_ 

45 -

Table I.--Comparison of biostratigraphic analyses from the COST No. B-3 well 

STEINKRAUS 

(1979) 

------------------- MIDDLE 

MIOCENE 

LOWER 

OLIGOCENE 

UPPER 

MIDDLE 

EOCENE 

LOWER 

LOWER MAESTRICHTIAN I CAMPANIAN 

SANTONIAN 

UPPER 

CONIACIAN 

CRETACEOUS 

l TURONIAN 

CENOMANIAN 

ALBIAN 

APTIAN I LOWER 

BARREMIAN 

CRETACEOUS 

HAUTERIVIAN 

BERRIASIAN 

TITHONIAN I 

UPPER 

JURASSIC 

KIMMERIDGIAN 

POAG 

(this volume) 

SEDIMENT-WATER INTERFACE 

~------~-----------

MIDDLE MIOCENE 

LOWER 

UPPER OLIGOCENE 

EOCENE 

MAESTRICHTIAN 

I 

CAMPANIAN 

SANTONIAN 

CONIACIAN UPPER 

CRETACEOUS 

TURONIAN 

CENOMANIAN 

ALBIAN I APTIAN 

BARREMIAN LOWER 

HAUTERIVIAN CRETACEOUS 

VALANGINIAN 

BERRIASIAN 

TITHONIAN I 

UPPER 

JURASSIC 

KIMMERIDGIAN 

CALLOVIAN(1) MIDDLE(?) JURASSIC 

18 

VALENTINE 

(this volume) 

-------------~----

MIOCENE 

OLIGOCENE 

EOCENE 

MAESTRICH IAN I CAMPANIAN 

SANTONIAN 

AND 

UPPER CONIACIAN 

CRETACEO'JS 

TURONIAN 

~?...,.....,..... 

CENOMANIAN 

ALBIAN 

APTIAN 

AND 

LOWER 

BARREMIAN 

CRETACEOUS 

HAUTERIVIAN 

AND 

VALANGINIAN 

BERRIASIAN 

l 

UPPER 

JURASSIC 

l 

0 

1- 10 

... 20 

"" 30 

1-40 

50 

.._, 60 

7 0 

0 

0 

8 0 Q 

~ 

1-

w 

w 

u. 9 0 ~ 

J: 

1-

a. 

w 

0 

f-1 0 

l-11 

l-1 

1-1 3 

l--14 

15 

16 
reservoir rocks with adequate porosity and 

permeability are also present below the depths 

penetrated by the B-3 well. 

Seals, in the form of shales, are present 

throughout the B-3 section. In addition, 

impermeable limestone beds, which may act as 

seals, are also present in the deepest parts of 

the well. 

Although the availability of structures for 

hydrocarbon trapping cannot be evaluated from a 

single well intentionally drilled off-structure, 

regional geophysical studies indicate the 

presence of structures associated with JurassicCretaceous shelf-margin carbonate buildups as 

19 

well as block faulting in the area of the B-3 

well. Furthermore, the rapid facies c~anges of 

sandstones, shales, and limestones in the lower 

parts of the COST Nos. B-2 and B-3 wells, 

combined with the expected facies changes 

between the B-3 well and the Jurassic-Cretaceous 

bank-margin carbonate buildup, indicate that the 

potential for significant stratigraphic traps is 

high in this area. 

In total, then, the potential for economic 

gas accumulations in this area is righ; the 

potential for oil accumulations is significantly 

lower, however. 
LITHOLOGY 

Barry M. Pollack 

Drill cuttings from the COST No. B-3 well 

were obtained and microscopically examined at 

30-ft (9.14-m) intervals between 3,810 and 5,790 

ft (1,160 and 1,765 m) and at 10-ft (3.05-m) 

intervals between 5,790 and 15,820 ft (1,760 and 

4,822 m) total depth (TD). References to the 

types of microfossils present are from 

Steinkraus (1979). 

Lachance (1979) has divided the 

stratigraphic sequence penetrated by the COST 

No. B-3 well into four major lithologic units. 

1~e major divisions of Lachance have been 

followed with only minor differences in reported 

depths. These minor variations probably reflect 

a difference in sample interval and the fact 

that the contacts between most of the units are 

gradational. The stratigraphic sequence 

penetrated by the COST No. B-3 well is shown in 

a columnar section in figure 10. Unit I, 

between 3,810 and 6,150 ft (1,160 and 1,870 m), 

is of Tertiary age and consists primarily of 

calcareous clay with minor amounts of sand and 

limestone. Unit II, between 6,150 and 8,250 ft 

(1,870 and 2,510 m), is of Late Cretaceous age 

and consists primarily of mudstone and siltstone 

with some glauconitic sandstone and dolomitic 

limestone. Unit III, between 8, 250 and 12,300 

ft (2,510 and 3,750 m), is of Early to Late 

Cretaceous age and consists primarily of 

sandstone and shale with some minor amounts of 

carbonate. Unit IV, between 12,300 and 15,820 

ft (3,750 and 4,822 m), is chiefly of Late 

Jurassic age and consists primarily of shales. 

UNIT I (3, 810-6,150 ft; 1,160-1,870 m) 

This unit is divided into subunits IA and 

IB on the basis of abundant layers of limestone 

below a depth of about 5,100 ft (1,550 m). 

Subunit IA (3,810-5,100 ft; 1,160-1,550 m) 

consists primarily of dark-gray to white, 

calcareous clay. It contains minor amounts of 

quartz sand and shell fragments. '!he sand is 

fine to medium grained, is relatively clean, and 

has angular to rounded grains. The shell 

fragments and microfossils are primarily 

Foraminifera; there are, howe...,er, some 

palynomorphs and nannofossils. Glauconite is 

present as rounded individual grains and in 

botryoidal aggregates in amounts r~nging from 

traces to locally abundant in the sandier 

portions of the subunit. Gypsum is present in 

sparse to locally abundant amounts in the form 

of authigenic, thin to thick, tabular crystals, 

which are sometimes aggregated in a micritic 

matrix. Mica is present in varying amounts 

throughout the subunit. Other tra~e constituents include pyrite in subhedral to euhedral 

crystals, argillaceous limestone, and ooliths 

with quartz nucleii. 

Subunit IB (5,100-6,150 ft; 1,550-1,870 m) 

consists of light-gray to white claystone, which 

is locally very calcareous, and ha~ some thin 

layers of white microcrystalline, fossiliferous 

limestone. Similar micritic calcite appears to 

be present in the calcareous claystone. 

Glauconite ranges from trace amounts in' the 

claystone and limestone to locally abundant in 

sand lenses. The glauconite is ust·ally in the 

form of botryoidal masses but has a few 

individual rounded grains. The sand~ are clean, 

fine to medium grained, and angular to well 

rounded; they contain clear to fr<'~ted quartz 

grains. Other trace constituerts include 

massive and euhedral pyrite; gypsum in thin and 

thick tabular crystals; buff-colored, dense, 

blocky dolomite; and satin spar gypsum. 

Microfossils include Foraminifera, nannofossils, 

and palynomorphs. 

UNIT II (6,150-8,250 ft; 1, 870-2,510 m) 

This unit consists primarily of purple to 

gray and brown, locally very calcarecus mudstone 

interbedded with glauconitic sandstone and 

dolomitic limestone. This lithology grades 

downward into a dark-gray calcareou~ claystone 

at about 7, 810 ft (2, 380 m). The sandstone is 

composed of fine to coarse, angular to 

subrounded, clear to gray, opaque quartz sand 

Figure 10.--Generalized plot of lithologies based on examinations of cuttings from the COST No. B- C> 

3 well. The biostratigraphic relationships are based on Steinkraus (197") and work 

conducted by International Biostratigraphers, Inc. (written communication, 1979). 

20 
PERIOD 

>- 0:: 

< 

~ 

0:: 

w 

.... 

V) 

:::) 

0 

w 

~ .... 

w 

0:: 

u 

u 

~ < 0:: 

:::) 

., 

EPOCH AGE LITHOLOGY 

MIOCENE 1-------E:=::=..:::=::1 _£ __ _ 

MIDDLE MIOCENE ~----­ ::-z.._-_*_-_-_ 

DESCRIPTION LITH DEPTH FEET 

UNIT METERS 

< 

H 

1000-

500 

2000-

3000-

1-1000 

4000-

Dark-gray 1o white,calcareous clay with 

----..ll...-_ locally abundant forams, shell fragments, 

EARLY MIOCENE ~..,.-....r.:-:-2C: glauconite,and gypsum. Small amounts of 

r~-ll_IGOC ___ E_N~l~E:~A·~~-E~o~1~uo~~;~~;N~~\~t~~~~-~--[-~-~~~~-f-iqJu~ar~t~z~a~n~dis~a~nd~.~~~~~~~~;;--t---l 15005000- 1 LATE EOCENE ~1 I 1~ Light-gray to white1often calc. claystone 

I-.:M~I~D~D~L~E~E~O:,::C:,:E:,:N:=E-tll~X~J:~:C:JC:1 w/locally abundant glauconite correspond· 

EOCENE [:Jx-:_ -.J..L~- ing w/local abundance of cleon qtz~ sand. 

V) 

:::) 

0 

w 

u 

< 

.... 

w 

0:: 

u 

w 

.... 

< 

_J 

V) 

:::) 

0 

w 

u 

< 

.... 

w 

0:: 

u 

>-

_J 

0:: 

< 

w 

u 

v; 

V) 

< 0:: 

:::) 

., 

w 

.... 

< 

_J 

EARLY EOCENE 

CONIACIAN 

CENOMANIAN 

-,14-.;-~­

~-A..oo'-..V 

/ / 

Layers of light-gray to white,often very 

fossiliferous limestone. 

Dark-brown, purple, and gray, calcareous 

muds1one interbedded with glauconitic 

sandstone and dolomitic I imestone. Darkgray and purple calcareous claystone 

near bottom of unit, with trace of quartz 

sand, shell fragments,and glauconite. 

~~-:=:-'t:- Brown to dark-gray, sandy shale interbedded 

with sandstone, shaley sandstone,and white 

micritic limestone. Trace amounts of coal 

ana pyrite. One thin bed of blocky, brown 

ALBIAN .............. 

-;-...!.:....... •••• 

~ :-.......... :.· .. : .......... ~.· 

7..::...... __ ··-·· APTIAN 

BARREMIAN 

z 

< HAUTERRIVIAN U.¥.!-~WL -··-··-· ~ VALANGINIAN'"--··- .. 

u 

0 

w 

z 

·.·.·::·::,'::=::·:: 

-:- .. L L 

BERRIASIAN ;:: •. •• :·. < 

TITHONIAN 

KIMMERIDGIAN 

····:-:·.·· .... ·.·. 

-----

0 0 

-:-::: .. : . .;.:.~.·.·.: 0 

~__:::_~_ 

~.:::::::::.~.:.: 

0 

~·· 

~· ·~...: 

to greeni sh·brown dolomite. 

21 

Brown to off-white oolitic limestone inter• 

b~dded with sands1one, shale,and sandy 

shale. 

Shale and sandy shale interbedded with 

limestone and minor sands1one. Coal 

often locally abundant in thin layers, 

often coinciding with local abundance 

of pyrite. 

6000-

1-2000 

7000-

9000-

3000 

10000-

11000-

3500 

12000-

13000-

4000 

14000• 

I 

I 

4500 - 15000 

I 
grains. The glauconite is present in trace 

amounts in the mudstone, is abundant in the 

sanstone, and is primarily in the form of 

botryoidal aggregates. The limestone occurs in 

very thin layers and is a gray to buff-colored 

micrite with small amounts of hard, dense, 

blocky, brown dolomite. Other trace cons tituents include massive nodular and euhedral 

pyrite and microfossils. The microfossils 

include Foraminifera, palynomorphs, and 

nannofossils. 

The claystone, 7,810-8,250 ft (2,380-2,510 

m), contains traces of clear quartz which is 

fine to medium grained, angular to well rounded, 

and, in a few cases, in the form of polycrystalline aggregates. Other trace constituents include nodular, massive, and euhedral 

pyrite and botryoidal aggregates of 

glauconite. Mica is present in trace amounts 

throughout the unit. 

UNIT III (8,250-12,300 ft; 2,510-3,750 m) 

This unit can be divided into subunits IliA 

and IIIB on the basis of the greater amount of 

clean quartz sandstone above 9,000 ft (2,740 m). 

The upper subunit, IliA (8,250-9,000 ft; 

2,510-2,740 m), contains clean quartz sandstone, 

interbedded shale, and minor amounts of 

limestone. The sandstone is light gray to 

white, is noncalcareous to slightly calcareous, 

and has clay and (or) silica cement predominating. It is moderately sorted, well 

consolidated, and very fine to medium grained; 

the grains are angular to subrounded and clear 

to gray-opaque (locally with frosted grains). 

Glauconite ranges from trace to sparse amounts, 

usually in the form of botryoidal masses with a 

few individual grains. The glauconite is more 

abundant in the sandstone than in any other 

parts of the subunit. Other trace constituents 

include pyrite in euhedral crystals and nodular 

masses, mica (disseminated throughout the 

subunit), and marine microfossils. The shale is 

primarily medium to light gray, noncalcareous to 

moderately calcareous (micrite), with small 

amounts of coal. Pyrite, usually in massive 

form with some euhedral crystals, is present in 

trace amounts and is slightly more abundant in 

coal-bearing strata. 

The carbonate material is primarily in the 

form of white to off-white laminae in the 

shale. It is nonfossiliferous to slightly 

fossiliferous, soft, dense, and micritic, and 

contains trace amounts of clean sand which is 

fine-grained and angular to rounded. Microfossils in this subunit include Foraminifera, 

palynomorphs, and nannofossils. 

Subunit IIIB (9,000-12,300 ft; 2, 740-3,750 

m) is predominantly sandy shale interbedded with 

sandstone, shaley sandstone, and limestone. 

Near the top and bottom of this subunit, the 

ratio of sandstone to shale shows a significant 

increase. Apparently on the basis of this 

change in the sandstone/shale ratio, Lachance 

22 

(1979) subdivided the interval fro~ 9,000 to 

12,300 ft (2,740-3,750 m). 

The shale in Subunit IIIB is brown to dark 

gray to locally black and chiefly nor~alcareous, 

but some samples contain large amounts of 

sand. The sand, mostly in the form of fine- to 

medium-grained quartz, is clear to frosted and 

angular to subrounded. Other trace ~onstituents 

include massive pyrite associated with coal; 

glauconite in botryoidal masses (more abundant 

in the sandier portions of the shale); hard, 

dense, brown, blocky dolomite, crystalline 

calcite; and microfossils. The s10mdstone is 

light gray to brownish gray to buff colored, 

slightly to moderately calcareous, and poorly to 

moderately sorted; it contains angular to 

subangular, clear to gray and brown opaque 

grains. It is generally fine to moderately 

coarse grained. Trace constituents include 

botryoidal masses of glauconite, nodular pyrite, 

and microfossils. 

The two thick sandstone beds ir the middle 

of this subunit (at 10,000 ft and 10,600 ft; 

3,050 and 3,230 m) are fairly clean, white, very 

fine to fine grained, with calcare.,us cement. 

The grains are subrounded to rounded and clear 

to frosted. Trace constituents include 

glauconite in botryoidal masses ( wlich is more 

abundant here than in other parts of the 

subunit), coal, and microfossils. 

Microfossils in this subunit include 

palynomorphs, nannofossils, and For~~inifera to 

a depth of about 9,530 ft (2, 900). 

UNIT IV (12,300-15,820 ft; 3,750-4,822 m [TD]) 

This unit is divided into two st,bunits (IVA 

and IVB) on the basis of a predominance of sandstone and limestone above 14,000 ft (4,270 m). 

The upper subunit (IVA 12,300-14,000 ft; 

3,750-4,270 m) consists primarily of interbedded 

sandstone, shale, sandy shale, ~nd oolitic 

limestone. The sandstone is generally white to 

light gray, well consolidated, fine to 

moderately coarse grained, poorly t~ moderately 

sorted, with angular to subroun~ed grains. 

Trace constituents include glauconite, pyrite, 

and coal. The glauconite is more al 'mdant here 

than in other parts of the sul: ~mit. It 

generally occurs as botryoidal aggregates, 

although there are a few individual subrounded 

grains. The pyrite occurs as massive nodules 

concentrated around pieces of coal. 

The shale is light to dark grey, commonly 

sandy, and moderately calcareous. Micrite, 

which is present in varying amounts, gives the 

shale its calcareous nature. n~ sand is 

primarily clean, fine to moderately coarse 

grained, clear to opaque, with angular to 

subrounded grains. Trace constituents include 

glauconite, pyrite, and coal. The glauconite 

occurs as botryoidal aggregates in tl~ sand. 

The carbonate is brownish gray to off white 

and ranges from a soft micrite to a l~rd, dense, 

somewhat argillaceous, finely crystalline 
limestone. Ooliths range from sparse to very 

abundant; they are most abundant in the micrite 

where they make up a significant percentage of 

the rock. The micrite acts as matrix around the 

ooliths which have quartz nuclei!. Trace 

constituents include botryoidal aggregates of 

glauconite, massive-nodular pyrite, and coal. 

Microfossils in this subunit include 

palynomorphs to a depth of 13,220 ft (4,050 m); 

palynomorphs and nannofossils from 13,220 to 

13,960 ft (4,050 to 4,250 m); and palynomorphs, 

nannofossils, and Foraminifera from 13,960 to 

14,000 ft (4,250 to 4,270 m). 

The lower subunit (IVB, 14,000-15,820 ft; 

4,270-4,822 m, [TD]) consists of sandy shale 

interbedded with limestone and minor amounts of 

sandstone. The shale is light to dark gray 

(locally black near the bottom of the well), 

ranges from somewhat calcareous to very calcareous, and is locally very sandy. Micrite, in 

places acting as matrix, gives the shale a 

calcareous nature. The sandstone is primarily a 

clean quartz sand, fine to medium grained, clear 

to frosted, angular to moderately well 

rounded. Trace constituents include glauconite 

in botryoidal aggregates (more abundant in the 

sandier parts of the section), nodular-massive 

pyrite, coal, and microfossils. The pyrite is 

closely associated with the coal. The limestone 

ranges from soft and micritic to hard, dense, 

and finely crystalline. It is generally light 

gray to white and slightly argillaceous. 

Ooliths with quartz nucleii range fro"ll. trace 

amounts in the crystalline limestone to locally 

abundant in the micritic limestone, where the 

micrite acts as matrix. Trace constituents 

include nodular-massive pyrite and microfossils. The sandstone ranges from predominantly white to light gray and buff colored. 

It is slightly calcareous to very calcareous and 

is locally consolidated with micritic matrix and 

(or) carbonate cement. Although the sandstone 

is usually well consolidated, a zone of poorly 

consolidated sandstone occurs between 15,750 and 

15,780 ft (4,800 m and 4, 810 m), the reported 

gas zone. In the gas zone, the sande-tone is 

clean, white, and moderately sorted. Coal 

varies from trace to locally abundant, and the 

more abundant coal zones are usually associated 

with a noticeable increase in the abundance of 

pyrite. Other trace constituents include 

glauconite in the form of botryoidal masses; 

hard, dense, blocky, brown, cryptocry3talline 

dolomite; and microfossils. There is a notable 

lack of glauconite in the gas-bearing sand zone 

(15,750 to 15,780 ft; 4,800 to 4,810 m). 

23 
S~~DSTONE PETROGRAPHY 

Barry M. Pollack 

Rotary drill cuttings of sandstone were 

chosen at 27 levels from 8, 300 ft (2, 530 m) to 

15,780 ft (4,810 m) for petrographic analysis. 

Thin sections were made of samples from each 

interval and stained to show potassium 

feldspar. The thin sections were examined by 

means of a standard petrographic microscope; the 

results of this analysis are shown in table 2. 

During drilling, coarse sand and gravel 

tend to disaggregate into individual constituent 

grains, making examination of representative 

rock textures impossible. Therefore, the grainsize columns of the table merely indicate the 

coarseness of the material examined and do not 

necessarily reflect the average grain size of 

sand in that interval. Thus, the finer grained 

and more lithified units in the section are 

emphasized in this analysis. 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 8,300 ft (2 ,530 m) 

to 15,780 ft (4, 810 m) is quartzofeldspathic, 

and most sandstone is classed as quartz 

arenite. Part of the sandstone (about one 

third) is sufficiently feldspathic to be classed 

as subarkose. Although there is a marked 

decrease in the ratio of potassium feldspar 

(orthoclase and microcline) to plagioclase 

feldspar below 11,100 ft 0,383 m), plagioclase 

is subordinate to the other feldspars throughout 

the section. The decrease in the amount of 

potassium feldspar below 11,100 ft (3,383 m) 

probably reflects changes in provenance, as the 

potassium feldspar is not observed to be 

drastically altered. 

Rock fragments are present throughout the 

section, although they never constitute a major 

rock-forming element. The rock fragments noted 

were primarily of sedimentary origin ~hale, 

limestone, and sedimentary quartzite). 

Most of the sediment in the section 

contains glauconite (of both pelletal and 

vermicular form) in varying amounts. Below 

15,740 ft (4,798 m), however, glauconite is 

notably lacking. The glauconite, in conjunction 

with calcareous microfossils and limestone, 

indicates 

conditions. 

dominantly marine de:nositional 

The sandstones are slightly mic~ceous and 

somewhat pyTitic throughout the 8,300-ft (2,530-

m) to 15, 740-ft (4, 79&-m) section; in some 

intervals pyrite is quite abundant. Lignitic 

inclusions are commonly present, especially 

between 10,300 and 10,800 ft (3,139 and 3,292 m) 

and between 15,760 and 15,780 ft (4,804 and 

4,810 m). 

DIAGENESIS AND CEMENTATION 

Malinowski (1 97 9) has shown that: the mean 

porosity of the sediaents in the COST No. B-3 

well decreases slightly with depth. This is to 

be expected in mineralogically immature 

sediments because of sediment compaction 

resulting from an increase of overburden 

pressure as a function of depth, as well as from 

progressive cementation. However, in the depth 

intervals examined, there are no o~servable, 

significant compaction effects such as crushing 

of relatively soft grains (glauconite and mica), 

orientation of elongate grains, and shattering 

or twinning of brittle minerals. Grain 

interpenetration through pressure solution was 

observed in a few places in the section. This 

is seen primarily in polycrystalline quartz 

grains with interlocking boundaries. The 

scarcity of these grains seems to indicate that 

the pressure-solution effects occurre~ prior to 

deposition in this particular section. There is 

little indication that mechanical compaction 

resulting from increased subsurface lithostatic 

pressure has played a major role in loss of 

porosity in these sediments. 

The chemical effects of mineral alteration 

and cement precipitation, although not large in 

scale, are more important in porosity reduction 

than are compaction effects. Starting at about 

11,000 ft (3,353 m), alteration of potassium 

feldspar and plagioclase feldspar (although of 

relatively small extent) becomes more important 

with increasing burial depth. This alteration 

takes the form of sericitization, kaolinization, 

or calcite replacement; it varies in form and 

intensity from one unit to the next. Although 

the increase in feldspar alteration may be 

correlatable with a slight increase in 

24 
Table 2.--PetPO(Jr>aphy of sel.ected sandstones fpom tl1e (!08T No. R-3 weU 

Depths represent 30-ft (9-m) sampling 

intervals from stated depth downward; 

x=common; a=abundant; t=trace; s=scarce; 

?=possible. 

K=K-Feldspar 

P=Plagioclase 

GL=Glauconite 

PY=Pyrite 

Diagenesis: 

CO=Compaction features 

FR=Fresh unaltered feldsp~r 

AL=Altered (sericitized or 

Grain size: 

S=Silt 

FI=Fine to very fine sand 

M=Medium sand 

MI=Mica 

LI=Lignite 

OR=Organic matter 

RF=Rock fragments 

kaolinized) feldspar 

Rock name: 

SA=Subarkose 

C-Coarse sand and gravel Cement: 

CA=Calcite 

QA=Quartzarenite 

FQA=Feldspathic quartzare~ite 

FLA=Feldspathic litharenite 

Constituents: CL=Clay (authigenic) 

Q=Quartz 

Depth Grain Size 

S FI M C 

Constituents Cements 

CL CA 

Diagenesis 

CO FR AL 

Roc1<: type 

Feet Meters Q K P GL PY MI LI OR RF 

8,330 

8,350 

8,400 

8,450 

8,500 

8,550 

8,600 

9,000 

10,000 

10,100 

10,200 

10,300 

10,400 

10,610 

10,700 

10,800 

10,900 

10,990 

11' 100 

13,800 

14,500 

14,610 

14,700 

15,750 

15,760 

15,770 

15,780 

2,530 

2,545 

2,560 

2,576 

2,591 

2,606 

2,621 

2,743 

3,048 

3,078 

3,109 

3,139 

3,170 

3,234 

3,261 

3,292 

3,322 

3,350 

3,383 

4,206 

4,420 

4,453 

4,481 

4,801 

4,804 

4,807 

4,810 

t X 

X 

X 

X 

t X X t 

X 

X X 

X t 

t X 

t X t 

S X t 

t X t 

X t 

X X t 

t X 

S X 

X t 

S X 

t X t 

X 

X t 

X t 

t X t 

X X 

X X 

X t 

X X 

a x t x 

a s t x 

a x t s 

){ ){ s t 

a a t s 

X S t 

X X S 

X t 

X S t 

X S t 

X S t 

X X t 

a a t 

X S t 

X S 

s 

s 

s 

s 

s 

t 

t 

s 

){ 

s 

X X X 

X t t 

X X t t 

X X t t 

X t 

X t t 

X t t 

X t 

X t t 

X t t 

X t 

X t t 

t 

t 

s 

t 

t 

X 

s 

t 

){ 

s 

s 

X 

s 

s 

X 

s 

s 

s 

t 

t 

t 

t 

t 

t 

t 

authigenic clay minerals as cementing agents, 

the general trend appears to be one of 

consistent calcite cementation with occasional 

occurrences of clay matrix. Calcite is clearly 

the most important cement throughout the 

section. Below 13, 800 ft (4, 206 m) the amount 

of authigenic clay increases, but calcite 

cementation still predominates. In the more 

fossiliferous units, the calcite cement displays 

poikilitic textures. This seems to indicate 

that, at least in these units, the presence of 

skeletal grains or carbonate rock fragments 

played a significant role in the nucleation of 

calcite cement. In the reported gas zone from 

15,750 to 15,780 ft (4,801 to 4,810 m), there is 

a noticeable decrease in the cementation of the 

t 

t 

t 

t 

t 

t 

t 

t 

t 

t 

t 

t 

t 

t 

t 

s 

s 

t 

t 

t 

t 

t 

t 

25 

s 

s 

s 

t 

t 

t 

t 

s 

X 

s 

t 

t 

t 

t 

t 

s 

t 

t 

s 

s t s 

X X t 

X S, S 

X X 

X X t 

X S 

t s 

t s 

t t X 

s 

S X S 

s s 

t X 

S X 

X X 

X 

X 

){ 

X t 

t X 

X 

X 

X 

t X 

X 

X 

X 

X 

X 

X 

X 

X 

t X 

t X 

X 

X 

X 

X 

t X 

S X 

s 

s 

t 

t 

s 

s 

t 

s 

t 

t 

t 

s 

t 

t 

X 

s 

X 

X 

X 

s 

X 

t 

t 

X 

t 

t 

s 

t 

X t 

X t 

X S 

s t 

s s 

s 

t 

s 

s 

t 

X 

s 

X 

s 

t 

t 

t 

t 

t 

t 

t 

t 

SA 

QA 

SA 

SA 

FQ4,SA 

QA 

SA 

QA 

QA 

QA 

QA 

SA 

FQ~ ,SA 

QA 

QA 

SA 

QA 

SA 

FLA 

QA 

QA 

QA 

QA 

QA 

QA 

QA 

QA 

sandstone. What cement is present in that 

interval, however, is primarily calcite. 

CONCLUSIONS 

The loss of porosity with de"lth (as 

described by Malinowski, 197 9) is largely the 

result of calcite cementation rather than of 

compaction or feldspar alteration. The 

prospects for improved porosity at equivalent or 

greater depths at other sites are relatively 

unfavorable unless some factor has significantly 

retarded or halted the in-situ produrtion of 

calcite cement. Even if this cementation does 

not occur at other sites, compaction or 

alteration effects might be more significant in 

such areas. 
COMPUTER WELL-LOG ANALYSIS 

Ching H. Wu and Renny R. Nichols 

Well logs from the COST No. B-3 well weie 

analyzed using a computer program--LOGCALC • 

The well logs were recorded on a Schlumberger 

LIS tape as well as on analog papers. Only the 

following logs were used in the computer 

analysis: Dual-induction spherically-focused log 

(DISFL), Long-spaced sonic log (LSS), Compensated neutron formation density log (CNL/FDC), 

and Compensated formation density log (FDC). 

Briefly, the computer well-log analysis was 

performed as follows: 

1. Selected intervals for log analysis on the 

basis of lithology and depositional 

environments. 

2. Determined the formation-water resistivity 

of each interval using recorded spontaneous 

potentials. 

3. Determined log parameters for LOGCALC 

analysis; executed LOGCALC programs to 

obtain preliminary results. 

4. Analyzed LOGCALC outputs and determined log 

paramete~s from crossplots. 

5. Used LOGCALC to process intervals when core 

data were available. 

6. Compared core and computed porosity data; 

then made necessary corrections on FDC. 

7. Made LOGCALC runs to obtain the final loganalysis results. 

Only two large intervals were selected for 

computer well-log analysis because of time and 

cost constraints. The first interval ranges 

from 8,200 to 12,400 ft (2,499 to 3,779 m), 

corresponding to the Lower Cretaceous deltaic 

sand-shale sequences. The second interval 

ranges from 12,400 to 15,810 ft (3,779 to 4,818 

m), corresponding to the Upper Jurassic 

carbonate and interbedded sandstone sequences 

deposited in marine to nonmarine environments. 

Because a different set of lithologic and log 

parameters was used for each of the two large 

intervals, computer-analysis results should be 

considered as qualitative. Extreme caution is 

advised and other reference materials should be 

considered when using the log-analysis results. 

Two well-log-analysis models were used in 

the log analysis. Because the formations from 

8,200 to 12,400 ft (2,499 to 3,779 m) are mainly 

sand-shale sequences, the interval wa:l analyzed 

using a sand-shale log-analysis mod~l (SAM7). 

On the other hand, as the formations from 12,400 

to 15,810 ft (3,779 to 4,818 m) £Ore mainly 

composed of carbonate rocks interbedded with 

sandstones, the interval was analyzed using both 

a sand-shale (SAM7) and complex lithology (CAM7) 

model. 

The interval from 8,200 to 15,A10 ft (2,499 

to 4,818 m) was logged in two separate runs. 

The bit sizes, mud weights, and assumed rock 

matrices were different below and abr>ve 12,688 

ft (3,867 m). In addition, the lithology 

changed from a sand-shale sequen--.e to a 

carbonate-dominated sequence below 12,400 ft 

(3, 779 m). Therefore, the entire interval was 

divided into three sections for comp•1ter welllog analysis. The input data and log-analysis 

models are shown in table 3. 

Three computer runs (passes) wer,.~ made for 

each section using a log-analysis model (SAM7 

and (or) CAM7). Pass 11 prints out ra··' data and 

histograms of log responses that provide the 

range of each log variable and infornation for 

log-response calibrations. 'Pass 22 makes 

borehole corrections, mud corrections, response 

conversions, and cross-plot analyse~. These 

factors provide some log parameters, as listed 

in table 3, for pass-33 analysis. Pass 33 

performs the well-log analysis, whicl' provides 

formation and lithology information. 

Figures 11 through 14 show comparisons of 

well-log-analysis and core-analysis data. 

Figure 11 shows a comparison of core (measured) 

and log (computed) porosities for the sandstone 

interval from 9,921 to 9,935 ft (3,024 to 3,028 

m). The computed results were obtained after 

the density log was multiplied by a correction 

factor of 0.99 based on the calibration infor1

Purchased from the Scientific Software Corporation and installed 

in Honeywell Multics computer at Denver Federal Center, Denver, 

Colorado. 

26 
Table 3.--Input &zta foro WGCALC anatysis 

[(-) indicates no data. For all intervals, constant a for Humble 

equation=0.62, constant m for Humble equation=2.15, compaction 

factor=!. 0, bottom-hole temperature=238°F, and approximate annual, 

mean sea-level temperature=lS. 2°F] 

Intervals in feet------------ 8, 200-12,400 

Intervals in meter----------- 2, 499- 3, 779 

Models----------------------- SAM7 

Clean matrix gamma ray 

(API unit)-----------------

Cl7:? c:~~ ~=~-~~~~==~--------­

Re~=~~=~) ~~=~=~-~~~~==~------ Sandstone transit time 

( ~s/ft) --------------------

Limestone transit time 

( ~ s/f t) --------------------

Dolomite transit time--------

Anhydrite--------------------

Formation-water resistivity 

at 75°F (ohm-m)------------

Fluid density (g/cm3)--------

Re~=~~=~) ~=~=~-~~~~=:: ______ _ Fluid transit time (~s/ft)--­

Shale resistivity (ohm-m)----

Shale gamma ray (API unit)---

~~:~: ::~~~~n d~~:~~~t~g~~~§~= 

Shale sonic porosity (pct)----

Clay neutron porosity (pct)---

Clay density porosity (pct)---

Mud weight (lbs/gal)----------

Bit size (in.)----------------

28 

2.65 

2.65 

52 

.us 

1.0 

1.0 

189 

2.5 

150 

34 

30.5 

so. 3 

4.9 

9.8 

12.3 

12,400-12,668 

3,779- 3,867 

SAM7 CAM7 

18 18 

2.65 2.71 

2.65 2.65 

51.3 51.3 

·159 

1.0 

1.0 

189 

7.0 

l19 

25 

30.5 

50.3 

4.9 

9.8 

12.3 

.159 

1.0 

1.0 

189 

7.0 

119 

25 

2.6 

12,688-15,810 

3,867- 4,818 

SAM7 CAM7 

18 

2.65 

2. 71 

51.3 

47.6 

43.5 

so.o 

.159 

1.0 

1.0 

189 

7.0 

l19 

25 

30.5 

50.3 

4.9 

11.7 

8.5 

18 

2. 71 

2. 71 

51.3 

47.6 

43.5 

so.o 

.159 

1.0 

1.0 

189 

7.0 

119 

25 

2.6 

ll. 7 

8.5 

mation. The effective porosity is calculated by 

considering corrections due to shale content. 

As shown, the core and computer-calculated 

porosities are comparable. Fig~re 12 shows the 

comparison of core and computed porosities for 

the sandstone interval from 11,010 to 11,060 ft 

(3,356 to 3,371 m). Figure 13 shows that for 

the limestone section from 12,573 to 12,580 ft 

(3,832 to 3,834 m), CAM 7 provides porosity 

values comparable with those from core 

analysis. Although the density porosity is 

comparable with core porosity for the sandstone 

section from 12,583 to 12,587 ft (3,835 to 3,836 

m), the effective porosity is set at zero owing 

to the high shale content. Figure 14 shows that 

in the sandstone section from 13,773 to 13,785 

ft (4,198 to 4,201 m), SAM7 calculated porosity 

values comparable to those measured in cores. 

However, below 13,785 ft (4,201 m), the borehole 

effect becomes significant, as seen on the 

caliper, so the porosity is set at zero. From 

the above comparisons, it is clear that computer 

well-log analysis, when proper inpu~ is 

supplied, can provide qualitatively satisfactory 

porosity information. 

Figures 15 and 16 show SAM7 analysis 

results for the section from 8,200 to 12,400 ft 

(2,499 to 3, 779 m). Plots such as those shown 

on figures 15 and 16 yield useful preliminary 

information for scanning through a large s~ratigraphic interval for correlation, foruation 

evaluation, and lithology determination. Information from other sources and further, more 

detailed, well-log-analysis data should b~ used 

to verify the present log-analysis results. 

Figures 17 and 18 show SAM7-analysis 

results for the interval from 12,400 to 15,810 

ft (3,779 to 4,818 m). Because significiant 

amounts of gas were detected by the mud-logging 

unit during drilling through the interval from 

15,751 to 15,786 ft (4,800 to 4,810 m), the log 

analysis results from the interval b?.tween 

15,700 and 15,810 ft (4, 785 and 4,819 tr) are 

enlarged and shown in figure 19. It a':'pears 

that the gas show is most likely to havr. come 

from the intervals from 15,743 to 15,755 ft 

(4,798 to 4,802 m) and (or) from 15,767 to 

15,775 ft (4,806 to 4,808 m), both havf-ng an 

average porosity of 12 percent and an a'•erage 

water saturation of 29 percent. However, from 

further investigation of the paper logs, it can 

be seen that an SP deflection occurs from 15,742 

to 15,754 ft (4, 797 to 4,801 m) and that a 

crossover of the FDC and the CNL exists from 

15,745 to 15,753 ft (4,798 to 4,800 tr), in 

conjunction with the higher resistivity which 

clearly indicates a gas zone. 

In order to provide more lith<'~logic 

information, the interval from 12,400 to 15,810 

ft (3, 779 to 4,818 m) was also analyzed using 

CAM7. Results of CAM7 analysis are shown on 

figures 20 and 21. Track 5 shows the ccmputed 

quartz, calcite, and dolomite contents. E~cause 

of time limitations, lithological comparison 

with cuttings and core descriptions was net made 

in this study. 

In summary, computer well log-analysis can 

provide valuable preliminary informaticn for 

correlation, formation evaluation, and lit.hology 

determination. Results of these computer welllog analyses must be verified using information 

from other sources and from more detailed welllog analysis on smaller subintervals. 

2Below 11,010 feet (3,350 m), the correction factor for the density log is 

0.98, which provides density porosity that matches the core porosity. 

27 
1-

w 

w 

u. 

z 

:c 

1-

a.. 

w 

0 

9920 .------,....-

SAM? 

<I> 0 = Density porosity 

<I> e = Effective porosity 

9936~---------L--------~--------~ 

r 

I 

f 

r 

I 

I 

\ 

J 

\ 

t 

y 

1 

0 10 20 30 2.6 2.7 2.8 2.9 10 12 14 16 18 

POROSITY, IN PERCENT GRAIN DENSITY, CALIPER, 

IN G/CM3 IN INCHES 

rn 

a: 

w 

1-

w 

~ 

~ 

I" 

b: 

w 

0 

Figure H.--Comparison of measured (core) and computed (log) porosities for the interval from 

9,921 to 9,935 ft (3,024 to 3,028 m). 

11,010 0 

~ 3356 

y 

0 

I 

0 

11,020 I 

0 

I 

0 

I 

0 3360 ' 0 rn I 

0 a: 

1- I w 

w 11,030 0 1-

w I w 

u. 0 ~ 

z I 

0 ~ 

I I 

0 I 

1- I 1- a.. 0 a.. w SAM? I w 0 11,040 0 <I> 0 = Density porosity 0 

I <l>e= Effective porosity 0 

I 

0 

I 

0 

I 

11,050 0 3368 cl 

\ 

0 

I I 

0 fo I 

11,060 ~~ 0 

0 20 30 2.6 2.7 2.8 2.9 10 12 14 16 18 

POROSITY, IN PERCENT GRAIN DENSITY, CALIPER, 

IN GRAMS/CM3 IN INCHES 

Figure 12.--Comparison of measured (core) and computed (log) porosity for the interval from 11,010 

to 11,060 ft (3,356 to 3,371 m). 

28 
tw 

w 

u.. 

~ 

:i 

to.. 

w 

0 

12,572 .---------r-------,-------. I I I 

0 - 3832 

-

' 0 

I 

0 

I - 0 - I 

0 

f- I 

I 

0 

I - f- 0 

3834 

I 

0 

ICAM? I ' 0 

,___ I 

0 cJ> 0 = Density porosity 

I 

f- I 

I - 3836 

Cl>e =Effective porosity 

0 

12,588 ,___ 

12,590 L__ ____ _L_ ____ --....! ____ __J I I I -

0 10 20 30 2.6 2.7 2.8 2.9 10 12 14 16 18 

POROSITY, IN PERCENT GRAIN DENSITY, 

IN GRAMS/CM3 

CALIPER, 

IN INCHES 

en 

a: 

w 

tw 

~ 

z 

:i 

1-

a.. 

w 

0 

Figure 13.--Comparison of measured (core) and computed (log) porosity for the interval from 12,573 

to 12,587 ft (3,832 to 3,836 m). 

tw 

w 

u.. 

z 

:I: 

ta.. 

w 

0 

13,770 ..---------.-------.----------. 

13,772 

13,776 

13,778 

cJ> core 

SAM? 

Cl>o= Density porosity 

Cl>e= Effective porosity 

10 20 

POROSITY, IN PERCENT 

30 2.9 

GRAIN DENSITY, 

IN GRAMS/CM3 

T T T -4197 

~l - 4198 

I (/) 

~\ c: 

LU 

~-

LU 

- 4199 :::: 

f- ~ 

" --

·~ a.. f- w 0 -4200 0 ! ,___ I 

\ 0 

f- f 4201 

I I l 

10 12 14 16 18 

CALIPER, 

IN INCHES 

Figure 14.--Comparison of measured (core) and computed (log) porosity for the interval from 13,773 

to 13,786 ft (4,198 to 4,202 m). 

29 
~ 

WELL NUMBER 

8-3 

DEPTH I o GRCD 

(met 

s 

s 

c 

4oEPTHI 

(feet} o.o2 

CD 

I') 

0 

0 

CD 

~ 

0 

0 

CD 

.. 

0 

0 

CD 

en 

0 

0 

CD 

en 

0 

0 

CD 

-.J 

0 

0 

CD 

CD 

0 

0 

CD 

(D 

0 

0 

(D 

0 

0 

0 

(D 

-0 

0 

(D 

I') 

0 

0 

(D 

~ 

0 

0 

PLOT OUTPUT FROM LDGCALC 

12/21/?9 22:44:20 

0.2 RT 

,-···--··---·-·····-·-

RWA 200 2 fN 

2000 

20000 I •o PHIE 0 0 Y&H 
(..) 

~ 

2900 

3000 

3100 

(D 

• 0 

0 

(D 

en 

0 

0 

(D 

en 

0 

0 

(D 

...J 

0 

0 

(D 

a) 

0 

0 

(D 

(D 

0 

0 

0 

0 

0 

0 

-0 

-

0 

0 

-0 

~ 

0 

0 

0 -

C.t) 

Q 

0 

Figure 15.--Results of computer well-log analysis for the Cost No. B-3 well (SAM7): 8,200-10,300 

ft (2,499-3, 139 m). 'The corrected gamma ray (GRCO) and caliper (CAL) values are 

plotted on track 1. The apparent water resistivity (RWA) is in track 2, true 

formation resistivity (RT) and neutron formation resistivity factor (FN) are in track 

3, effective porosity (PHIE) is in track 4, and shale content (VSH) is in track s. 
u-

...JO 

cz: •• uo 

e ... C) •• 

...J ..... 

N z: 

C) 

0:: 

~ 

~ 

::) 

IL 

~en 

:)I" 

C)' 

~0 "' C)' 

...JN 

ILIJHJ)U 

0:: 

I&J 

ID 

z: It') ::) 

z I 

m ...J 

...J 

I&J 

:a: 

i 

> 

• 

• 

.... 

11-4 

J: 

L 

t 

0 

0 I .. •• • .. 

~ z 

- ~ 

"! 

D .. 

I 

.. 

cz: 

:a: 

IIC 

~ 0 

t • 10300 ~ : 10400 10500 10600 10700 10800 10900 11000 11100 11200 11300 11400 

I ~ .. 

C) 

u ...J 

~ cz: 

u 

0 • 

% .. 

.. t: : .... • 0 ! 

32 
~ 

-en 

c 

c 

--

CJ) 

c 

c 

--..,J 

c 

c 

--C» 

c 

c 

--

CD 

c 

c 

N 

-

c 

c 

c 

-N 

- 3700~ t~ I 

c 

c 

I.=-

N -

N 

c 

c 

-N 

1.1) 

c 

c 

-N 

~ 

c 

c 

Figure 16.--Results of computer well-log analysis for the COST No. B-3 well (SAM7): 10,300-12,400 

ft (3,319-3, 779 m). The corrected gamma ray (GRCO) and caliper (CAL) values are 

plotted on track 1. The apparent water resisitivity (RWA) is in track 2, true 

formation resistivity (RT) and neutron formation resisitivity factor (FN) are in track 

3, effective porosity (PHIE) is in track 4, and shale content (VSH) is in track s. 
~ 

WELL NUMBER s PLDT DUTPUT FRDN LDGCRLC s B-3 c 12121/19 21:51:01 o ODLD 

DEPTH I 0 GRCD 200 ui:PTiol 0.2 RT 2000 , ............................................. 

( m••en l 8 CRL 18 ( ftetl 0-02 RWR 200 2 FRVE 20000 I 'o PHIE 

o LIME 

SILICR ----------- ------------- N 

.. 

0 

0 

N 

en 

0 

0 

N 

en 

0 

0 

N 

..,J 

0 

0 

.... 

N 

0) 

0 

0 

N 

w 

0 

0 

w 

0 

0 

0 

w 

0 

0 

w 

N 

0 

0 

w 

w 

0 

0 

w 

.... 

0 

0 

w 

cn 

0 

0 
(..) 

U'l 

w 

0') 

0 

0 

w 

..J 

0 

0 

.... 

w 

co 

0 

0 

w 

(D 

0 

0 

~ 

0 

0 

0 

~ 

-0 

0 

---?_,.. 

Figure 17.--Results of computer well-log analysis for COST No.B-3 well (SAM7): 12,400-14,100 ft 

(3,779-4,297 m). The corrected gamma ray (GRCO) and caliper (CAL) values are plotted 

on track 1. The apparent water resistivity (RWA) is in track 2, true formation 

resistivity (RT) and neutron formation resistivity factor (FN) are in track 3, 

effective porosity (PHIE) is in track 4, and shale content (VSH) is in track s. 
~ 

WELL NUMBER 

B-3 

s 

s 

c 

DEPTH I 0 GRCO 200 I DEPTH 

4400 

4500 

4600 

~--~~=====-~-~-~ 

' ----

-

. 

PLOT OUTPUT FROM LOGCALC 

12/07/79 21:12:30 
U) 

..... 

.... 

c.n 

t.l) 

0 

0 

.... 

c.n 

.... 4 700 1- I 0 

0 

.... 

c.n 

c.n 

0 

0 

.... 

c.n 

en 

0 

0 

.... 

c.n 

-.J 

0 

0 

.... 

c.n 

CD 

0 

0 

.... 

c.n 

to 

0 

0 

Figure 18.--Results of computer well-log analysis for COST No. B-3 well (SAM7): 14,100-15,810 ft 

(4,297-4,818 m). The corrected gamma ray (GRCO) and caliper (CAL) values are plotted 

on track 1. the apparent water resistivity (RWA) is in track 2, true formation 

resistivity (RT) and neutron formation resistivity factor (FN) are in track 3, 

effectived porosity (PHIE) is in track 4, and shale content (VSH) is in track 5. 
DEPTH 0 

(METERS) 8 

WELL NUMBER 

B- 3 

GRCO 

CAL 

s 

5 

c 

200 DEPTH 

18 ( FT l 

CJl 

-.J 

D 

D 

Cl1 

-.J 

Cl1 

D 

Cl1 

CX) 

D 

D 

Cl1 

CX) 

Cl1 

D 

38 

PLOT OUTPUT FROM LOGCRLC 

12/06/79 20:52:51 

o .2 RT 2000 , ................................................ . 

o .02 RWR 200 2 FN 20000 

/ ... :::::• 

···~· ... 

··~ 

Figure 19.--Results of computer well-log ana-

(4,785-4,818 m). T\e corrected 

on track 1. The apparent water 

tivity (RT) and neutron formation 

sity (PHIE) is in track 4, and 
40 

PLOT OUTPUT FROM LOGCALC 

12/06/79 20:55:37 

PHIE 0 100 SW 0 

lysis for COST No. B-3 well (SAM7): 15,700-15,810 ft 

gamma ray (GRCO) and caliper (CAL) values are plotted 

resistivity (RWA) is in track 2, true formation resisresistivity factor (FN) are in track 3, effective poreshale content (VSH) is in track 5. 

39 
WELL NUMBER 

B-3 

DEPTH I 0 GRCO 200 

(meters) I 8 CAL 18 ----------

~ 

I 

s 

s 

c 

DEPTH 

(feet) 

N 

.... 

0 

0 

N 

C11 

0 

0 

N 

en 

0 

0 

N 

..,J 

0 

0 

N -

CX) 

0 

0 

-N 

(D 

0 

0 

(.I) 

0 

0 

0 

(.I) 

-0 

0 

(.I) 

N 

0 

0 

(.I) 

(.I) 

0 

0 

(.I) 

.... 

0 

0 

t.o.l 

C11 

0 

0 

PLOT OUTPUT FROM LOGCALC 

12/21/'79 2L:L'7:40 

o.2 RT 2000 

r··············································· 

0-02 RWA 200 2 FN 20000 I •o PHIE 0 0 VSH 

I!!F LHU~ I ~ 

~-·'1ow I ~ .. · ~ ==-

~ 

.~ 
~ 

...... 

w 

C1l 

0 

0 

U) 

...:J 

0 

0 

w 

0) 

0 

0 

w 

f.D 

0 

0 

~ 

0 

0 

0 

-~ 

0 

CJ 

~ 1: ---1 c. 

Figure 20.--Results of computer well-log analysis for COST No. B-3 well (CAM7): 12,400-14,100 ft 

(3,779-4,297 m). The corrected gamma ray (GRCO) and caliper (CAL) values are plotted 

on track 1. The apparent water resistivity (RWA) is in track 2, true formation 

resistivity (RT) and neutron formation resistivity factor (FN) are in track 3, 

effective porosity (PHIE) is in track 4, and shale content (VSH) is in track s. 
~ 

1\) 

DEPTH 0 

WELL NUMBER 

B- 3 

GRCO 

4 j(, 0 ,,----==-=-----

4400 

4500 

200 

s 

s 

c 

DEPTH 

~,,I 

-.... 

-0 

0 

.... 

.... 

N 

0 

CJ 

; 

Ul 

CJ 

CJ 

.... 

.... 

.... 

CJ 

CJ 

; 

CJ1 

CJ 

CJ 

; 

en 

CJ 

CJ 

.... 

.... 

...J 

CJ 

CJ 

.... 

.... 

00 

0 

CJ 

.... 

.... 

(D 

CJ 

CJ 

..... 

CJ1 

CJ 

0 

CJ 

..... 

CJ1 

.... 

CJ 

CJ 

~ N 

CJ 

CJ 

D 

PLOT OUTPUT FROM LOGCRLC 

12/16/79 20:52:10 

0.2 RT 

DOLO 

2000 LIME 

.o2 RWR 200 2 FRVE 2oooo 1 •o PHIE o , o SILICR 
t> 

4700 

46001-~ 

CJl 

1.1) 

a 

a 

..... 

CJl 

.,.. 

a 

a 

..... 

CJl 

CJl 

a 

a 

..... 

CJl 

C'l 

a 

a 

..... 

CJl 

....! 

a 

a 

CJl 

co 

a 

a 

..... 

CJl 

(D 

a 

a 

Figure 21.--Results of computer well-log analysis for COST No. B-3 well (CAM7): 14,100-15,810 ft 

(4,297-4,818 m). The corrected gamma ray (GRCO) and caliper (CAL) values are plotted 

on track 1. The apparent water resistivity (RWA) is in track 2, true formation 

resistivity (RT) and neutron formation resistivity factor (FN) are in track 3, 

effective porosity (PHIE) is in track 4, and shale content (VSH) is in track s. 
FORAMINIFERAL STRATIGRAPHY, 

PALEOENVIRONMENTS, AND DEPOSITIONAL 

CYCLES IN THE OUTER BALTIMORE 

CANYON TROUGH 

c. Wylie Poag 

INTRODUCTION 

At least eight studies of foraminifers in 

the offshore portion of the Baltimore Canyon 

trough have now been published (Hathaway and 

others, 1976, 1979; Olsson, 1978, Poag, 1977, 

1978, 1979;), and three others have been openfiled by the u.s. Geological Survey (Hathaway 

and others, 1976; Smith and others, 1976; and 

Steinkraus, 1979). Most of the 17 nonexploration drill holes in the offshore part of the 

trough have penetrated no deeper than 1,000 ft 

(305 m) beneath the sea floor and have recovered 

only Cenozoic (mainly Miocene and younger) sedimentary rocks (fig. 22; Poag, 1978). Completion 

of the COST No. B-3 well has provided a second 

record (in addition to the COST No. B-2 well) of 

Middle(?) and Upper Jurassic and Cretaceous 

rocks in the outer part of the trough. This 

report provides a preliminary biostratigraphic 

and paleoenvironmental analysis of the planktic 

and benthic foraminiferal assemblages recovered 

in the COST No. B-3 well (fig. 23). Because the 

report is preliminary, later studies may modify 

some of the interpretations formulated herein, 

but the major conclusions will probably not be 

greatly altered. The B-3 results are compared 

to a revised analysis of the B-2 well (fig. 24; 

Poag, 1977, 1978) and are placed in regional 

stratigraphic and structural context by plotting 

them on a 48-channel common-depth-point seismic 

reflection profile (fig. 25). 

The biostratigraphic zonation is based 

primarily on planktic foraminifers in the Upper 

Cretaceous and Cenozoic rocks, but radiolarians 

provide secondary biochronology in the biogenicsilica-rich Miocene section. Benthic foraminifers provide age estimates for the Early 

Cretaceous and Middle(?) and Late Jurassic 

rocks. Paleoenvironmental interpretations are 

based on benthic foraminiferal associations, 

predominance of benthic genera, species 

diversity, absolute abundance of all specimens, 

and relative abundance of planktic specimens. 

44 

The foraminiferal zonations and time scales of 

Berggren and van Couvering (1974), Blow (1969), 

Hardenbol and Berggren (1978), arri Stainforth 

and others (1977) are used for the Cenozoic; 

those of Ascoli (1976), Pessagno (1967), and van 

Hinte (1976a, b), for the Cretaceous and 

Jurassic. The radiolarian interpretations are 

based on the work of Kling (1978), and Riedel 

and Sanfilippo (1978). 

Considerable uncertainty exists about the 

precise position of some of the sta~e boundaries 

in the Lower Cretaceous and Jurassic 

intervals. (See Valentine, this volume; Ascoli, 

1976.) The biostratigraphic interpretations are 

compatible, as far as possible, wit~ the work of 

Ascoli (1976), who thoroughly studied the 

foraminiferal sequences in the Scotian Basin and 

calibrated them with the palynomorph studies of 

colleagues who analyzed the same wells (Bujak 

and Williams, 1977; Williams, 1975). 

Samples from the COST No. B-3 well are, 

like those of the COST No. B-2 well, mainly 

rotary-ditch cuttings, taken every 10-30 ft (3-9 

m) beginning at 3,810 ft (1,161 m) below the 

Kelly Bushing (KB was 42 ft or 12.8 m above sea 

level). One hundred and five sidewall cores 

were also taken for foraminiferal studies in the 

COST No. B-3 well, and all of th~m have been 

examined through the courtesy of International 

Biostratigraphers, Inc. (see Amato and Simonis, 

1979, pl. 2, for location of side.wall cores.) 

The cuttings samples were examined at 30-ft (9-

m) intervals throughout the Cenozoic section and 

at 10-ft (3-m) intervals across th~ CretaceousCenozoic boundary. The remaining Cretaceous and 

Jurassic samples were examined, witl few exceptions, at 90-ft (27-m) intervals. (See fig. 23 

for location of examined samples.) The 

biostratigraphic sequence is described from the 

highest (youngest) sample downward, as is 

customary for drill holes. Conse"'uently, the 

first (highest) appearance of diagnostic fossil 

species as cited in the drilled sequence is, in 

fact, the last chronostratigraphic ~opearance. 
0 50 MILES 

L.___...j 

0 50 KM L-....J 

o. 

COST 

8-2 0~· , 

·o ./ . . . . ) 

.. / 

~ .o/ ~~ .. / ~. / 'vo 

•/ 

.. / 

o • /~MCOR 

0 

:Q . . / . "/ 

~-. 

~~-. 

~0 

0 

0 //~ 6010 

/ 

·cr / . ·/ l. ·. AMCOR co~T 

0 

0 

.. • '"'~ o~ <s o, 6021~ 8 '3 • ,o01 I -

0 

0 

<~oo • 

0 

.. I A :o fi 

0 

0 

0 

~ r--

I 

• ol. 

0 

Figure 22.--Location of study area showing USGS seismic lines and drill sites in the outer part of 

the Baltimore Canyon trough. AMCOR= USGS Atlantic Margin Coring Project; ASP= 

Atlantic Slope Project (Exxon, Chevron, Gulf, and Mobil, 1967); COST= Continental 

Offshore Stratigraphic Test (Ocean Production Co., 1976, B-2; Chevron, 1979, B-3). 

Numbers on seismic lines refer to shot points. Drill sites have been pr'1jected 

approximately along strike to USGS Seismic Line 25. (See fig. 25.) 

45 
0 KB COST 8-3 

SEA LEVEL 

500 

1000 

a:: 

w 

1-

~~ z 

0 

N 

0 (.!) 1500 iii z 

:I: 

en 

::::> 

m 

~ _J 

w 

~ 2000 

~ 

0 

_J 

w 

m 

1-

w 

w PALEOENVIRONMENT 

u... 2500 NON IN MID OUT UP LOW IMARINE,SHELF I SHELF,SHELF I SLOPE 'SLOPE I 

0 20 100 200 500 1000 METERS 

SEA FLOOR I 0 a:: ~ I 0 a:: 0 <I I _J z 

a:: u... I 3000 w 

1- I <( <I 100 w ::J 

a I en 

I 3: 

I 0 

_J 

I w 

-- 200 m 

3500 en 

a:: 

w 

1-

w 

300 :::!'! 

Figure 23.--Biostratigraphic column of the COST 

No. B-3 well, showing foraminiferal 

biozones and paleoenvironments. 

Dashed lines indicate approximate 

determinations; wavy lines designate 

hiatuses. 

46 

0 KB COST 8-2 

SEA LEVEL 

PALEOENVIRONMENT NON IN MID OUT UP LOW r-fH£LF I SHELFISHELF fLOPE I SLOPE I 20 100 2 0 500 1000 

SEA FLOOR 1 METERS 0 

500 I 

I 

1000 0 

0 

C\.1 

8a:: 

rr>o 

(.!) 0 

_J 

z u... 5: 

en O<C 

m 

::::> ow 

ven 

~ 

0 

_J 

ow 

om 

3: 10 

0 en _J a:: 

m 

w w olow 

tO :::::IE 

0 

~ 

0 

0 

co 

0 

0 

m 

Figure 24.--Biostratigraphic column of the COST 

No. B-2 well, showing foraminiferal biozones 

and paleoenvironments. The term "seismic" 

following a stage name indicates that the 

stage boundaries have been extrapolated from 

the B-3 well by means of seismic correlation. 

The term "palyn" following a stage same indicates that palynomorphs are the basis of the 

stage or series assignment. 
COST 8-3 PALEOENVIRONMENT 

,J~~, s~rLF I s~rF ,s~~lF I sroPE, st8~, 

0 20 100 200 500 1000 0 I METERS 0 

TOP SAMPLE r<> 

4000 0 

0 

v 

0 

0 

I() 

4500 rt5? 

0 

I 0 

I <.0 

l 5000 0 

0 

1'-

P14 

0:: 0 0 0 0 ---J CX) _J 

LL. 

~ 5500 I <( I w 3: I en 0 P9 __. 0 

I w 0 3: CD m g I w I- ,..j CD w 

w en LL. 6000 P6 0 0:: 

UCI4-13 0 w Q Iw 

:::::!: 

en 0 - Q Q 

6500 (.) 

::J 

0 

0 

~ 

CXl 

(.) 

::J 

7000 0 

0 

r<> 

0 

0 I v r-

(.) 

::J 

0 

0 

I() 

Figure 23.--Biostratigraphic column of the COST 

No. B-3 well, showing foraminiferal 

biozones and paleoenvironments.--

Continued 

47 

COST 8-2 PALEOENVIRONMENT 

NON IN 1110 OUT UP LOW j'i"RIIEI SHELF ISHELF,SHELF I SLOPE' SLOPE I 0 20 100 200 500 1000 0 

METERS 0 

Q 

4000 0 

Q 

0 

0 

~ 

4500 

0 

0 

~ 

PB 

0 

5000 0 ':'! 

Oo:: 

.oo 

~0 __. 

LL. 

<( 

3: ow 

oen 0 '<.0 _J -3: w g CD 

w 

CD 

0 

-~~ -w 

Iw 

:::::!: 

0 

0 

~ 

0 

0 

~ 

0 

_o 

0 

I N 

I 

I 0 

I -0 

I N 

-s 0 

_o 

N 

N 

Figure 24.--Biostratigraphic column of the COST 

No. B-2 well, showing foraminiferal 

biozones and paleoenvironments.--

Continued 
COST B-3 

CD 

::.::: 

8000 

8500 

9000 

9500 

~ 10000 

0 _.J 

w 

CD 

fw 

w 

LL 

10500 

11000 

11500 

<t 

(.) 

--' 

PALEOENVIRONMENT 

NON IN MID OUT UP LOW 

IMARINEI SHELF I SHELF I SHELF I SLOPE I SLOPE I 

0 20 1 100 200 500 1000 METERS 

0 

0 

c..D 

0 

0 

1'-

0 

0 

CX) 

0 

0 

()) 

0 

0 

0 

C\J 

oc:: 

oo _o 

C\J_.J LL 

<! 

w oen 

2~ C\Jg w 

CD 

oen 

00::: 

row 

C\Jf0 

0 

o::;t 

C\J 

0 

0 

LO 

C\J 

w 

~ 

Figure 23.--Biostratigraphic column of the COST 

No. B-3 well, showing foraminiferal 

biozones and paleoenvironments.--

Continued 

48 

COST B-2 

8000 

8500 

9500 

CD 

::.::: 

~ 10000 

0 _.J 

w 

CD 

PALEOENVIRONMENT 

NON IN M 10 OUT UP LOW 

IMARINEI SHELFISHELFISHELF I SLOPE I~ 

0 20 riOO J~~ER~CO 1000 

,--

L_, 

,J I 

0::: 

0 

0 

_J 

LL 

<! 

w 

en 

~ 

g 

w 

0 CD 

0 en 0 0::: ro w 

fw 

~ 

0 

Q 

ro 

0 

0 

C\J 

I'() 

0 

0 

I'() 

ro 

0 

0 

o::;t 

ro 

0 

0 

LO 

I'() 

Figure 24.--Biostratigraphic column of the COST 

No. B-2 well, showing f01·arniniferal 

biozones and paleoenvironments.--

. Continued 
COST 8-3 

3: 

0 

_J 

12500 

13000 

~ 14000 

~ 

w 

w 

LL 

PALEOENVIRONMENT 

IM~~EISHrLF I s~eF ls~~lF I s~6PEI st8~1 

0 20 100 200 500 1000 METERS 

TO 15820ft; 4822m 

0 

0 

0 

r<) 

0 

0 

r<) 

0 

0 

C\J 

r<) 

oo:: 

oo 

1'<)0 

r<)LZ 

<l: 

w Oc.n 

0 

"<:t3: 

r<">O _J 

w 

CD 

Oc.n Oo:: 

LOw 

r<)~ 

0 

0 

lO 

r<) 

0 

0 

,.._ 

r<) 

0 

0 

(X) 

r<) 

0 

0 

m 

r<) 

w 

::::?! 

Figure 23.--Biostratigraphic column of the COST 

No. B-3 well, showing foraminiferal 

biozones and paleoenvironments.--

Continued 

49 

COST 8-2 

3: 

0 

_J 

12500 

13000 

13500 

~ 14000 

~ 

w 

w 

LL 

14500 

15000 

15500 

16000 

z 

<X 

z 

0 

:I: 

!:::: 

1-

(J 

-~ 

! 

z 

<X 

0 

a:: 

0 

u. 

X 

0 

E 

z 

<X 

> g 

...J 

<l 

() 

PALEOENVIRONMENT 

NON IN MID OUT UP LOW 

IMAR"" SHELFISHELF,SHELF I SLOPE I SLOPE I 0 20 100 200 500 1000 

I 

I 

I 

I 

I 

I 

I 

I 

METERS 

LTD 16043ft; 4890m 

0 

.0 

lO 

f'() 

0 

-~ f'() 

0 

.0 

(X) 

f'() 

0 

-g 0:: 

v 0 

g 

LL 

o<l: 

-0 w ~C/) 

3: 

g 

w OCD 

_o 

C\J C/) 

.;tO:: w 

~ 

w o::E 

_o 

f'() 

v 

0 

_o 

LO 

v 

0 

-@ 

v 

0 

0 

~ 

Figure 24.--Biostratigraphic column of th~ COST 

No. B-2 well, showing foraminiferal 

biozones and paleoenvironments.--

Continued 
(/) 

~ 

NW 

~3 

COST AMCOR 

B-2 6010 ;:SEISMIC 

f:>HOT POINT 

2500 2600 

~ ~~;;~:f~;;~~~~~~~~~~~~~~~~Ie~~~~~~~~~~~~~~~~~~ ~ 

~ 

0 

0 

I 

5 

5 

I 

10 15 MILES 

10 KILOMETERS 

I 

Figure 25.--Geologic cross section along USGS Seismic Line 25.(See fig. 22). Drill sites have 

volume; Grow, this volume). Biostratigraphic boundaries in the COST No. B-3 

and older rocks) to accommodate the southward dip from the B-3 location; there is no 

outline of carbonate platform section; these lines are dashed where data is sparse 

BIOSTRATIGRAPHY 

Quaternary, Upper Miocene(?), and Pliocene 

rocks (2,728 to""3,810 ft; 831 to -1,161 m) 

No samples were collected shallower than 

3,810 ft (1,161 m) in the COST No. B-3 well; but 

it is certain, on the basis of other core holes 

and correlation of seismic profiles (fig. 25; 

Schlee and Grow, this volume), that Pliocene and 

Quaternary rocks were penetrated. The first 

sample collected (at 3,810 ft; 1,161 m) is of 

middle Miocene age, but the presence there of 

the late Pliocene planktic foraminifer 

Globo~otalia miocenica indicates that upper 

Pliocene beds lie above 3,810 ft. The Pliocene 

radiolarian Ommata~tus avitus also is in the 

sample at 3,810 ft. At ·present, it is not clear 

exactly how far above 3,810 ft the middle 

Miocene rocks extend or whether there are any 

upper Miocene rocks at this locality, but upper 

Miocene rocks are tentatively placed between 

3, 770 and 3,400 ft (1,149 and 1,C'36 m) on the 

basis of seismic correlation with the COST No. 

B-2 well (fig. 24). 

Middle Miocene rocks (~3,810 to""4,470 ft; 

--1,161 to -1,363 m) 

The youngest sample collected from the B-3 

well is of middle Miocene age (fig. 23). The 

presence of numerous specimens of Tu~bo~otalia 

siakensis indicates that this s~mple can be 

stratigraphically no higher than Zone N.14. 

Bulimina elongata (previously referred to by 

Poag (1978) as Buliminella g~cili~), a typical 

Miocene benthic species, is al·~ndant; and 

Canna~tus pette~ssoni, a middle Miocene 

radiolarian, is frequent. 

At 3,840 ft (1,170 m) specimens of the 

50 
SEISMIC 

LINE SPLICE 

AMCOR COST 

6021 B-3 

ASP 

5 SEA SURFACE 

CARBONATE 

PLATFORM 

~ 

w 

w 

LJ.... 

~ 

::::c 

~ 

a... 

w 

6000 Cl 

000 

been projected approximately along strike to intersect the seismic line (Schlee and Grow, this 

well have been systematically shifted downward approximately 650 ft (200 m) (for the Oligocene 

southward dip from the B-2 site, however. Heavy lines show approximate position of fault~ and or difficult to interpret. 

short-ranging GZoboPotaZia fohsi Pobusta 

indicate the lower part of Zone N.13. At 3,900 

ft (1, 189 m) GZoboPotaZia pePiphePoa~uta marks 

the top of Zone N.12. At 3,960 ft (1,207 m) the 

GZ. fohsi group disappears, suggesting that Zone 

N.ll was penetrated at this depth. However, 

caved specimens of the GZ. fohsi group recur 

deeper in the well. At 4,230 ft (1,289 m), the 

radiolarian Calo~y~Zetta ViPginis indicates an 

0.369 middle Miocene age, as does the 

radiolarian CaZo~y~Zetta ~ostata at 4,350 ft 

(1,326 m). 

At 4,410 ft (1,344 m), the first appearance 

of GZobigePinoides si~anus marks the top of Zone 

N.9, the lowest zone of the middle Miocene. 

CannaPtus mammifePUs, a lower middle Miocene 

radiolarian, also occurs for the first time at 

this level. TuPboPotaZia s~ituZa first appears 

at 4,440 ft (1,353 m). 

51 

Lower Miocene rocks ""4,470 to -4,6130 ft; 

-1,363 to -1,427 m) 

At 4,470 ft (1,363 m), lower Miocene 

radiolarians appear: Sti~ho~oPys l.Jol.ffii and 

CannaPtus vioZina at 4,470 ft, and CannaPtus 

tubaPius at 4, 500 ft (1, 372 m). The sample at 

4, 500 ft also contains the diagnostic planktic 

foraminifer TuPboPotaZia kugZePi, whic.h ranges 

no higher than Zone N.4, the lowest Miocene 

zone. At 4,530 ft (1,381 m), the lower Miocene 

radiolarian CannaPtus pPismati~us is present, 

and at 4,590 ft (1,399 m), GZobigePina auguZioffi~inaZis, G. auguZisutupalis, G. 

pseudo~ipePoensis, and G. oua~hitaensis appear 

together. The thinness of the interval between 

the top of N.9 and the highest lower Miocene 

rocks (probably Zone N.5) and the absence of any 
suggestion of Zones N.8 through N.6 in these 

deepwater sediments are evidence of a possible 

disconformity separating lower middle Miocene 

and lower Miocene rocks at approximately 4,450 

ft (1,356 m). 

Upper Oligocene rocks (~4,680 to ~4,980 ft; 

,....1,427 to ""1,518 m) 

The upper boundary of the Oligocene is not 

well defined by planktic foraminifers, as 

pointed out by many authors. (See Hardenbol and 

Berggren, 1978, for current status of the 

boundary.) Most authors place it either at the 

base of, or somewhere within, Zone N.4; but its 

exact placement has not been firmly established. It is widely agreed, however, that 

GtobigePina opima forma nana does not range 

above the upper Oligocene Zone P.22 (in fact, it 

may not quite reach the upper boundary), and the 

first occurrence of this species is used to 

identify the youngest Oligocene rocks, at 4,680 

ft (1,427 m). The transition from the lower 

Miocene T. kugtePi assemblage seems to take 

place without any break in sedimentation. At 

4,740 ft (1,445 m), GtobigePina opima forma 

typiaa marks the top of Zone P.21. At 4,830 ft 

(1,472 m) the typical late Oligocene 

radiolarians DoPaadoapyPiB ateuahua and 

TheoayPtia annoaa appear. Zone P. 20 may be 

present between 4,770 and 4,980 ft (1,454 to 

1,518 m), but the absence of diagnostic species 

of lower Oligocene Zones N.19 and N.18 above the 

highest Eocene rocks suggests that a disconformity separates the upper Oligocene and upper 

Eocene at ..... 4,980 ft (1,518 m). 

Eocene rocks (""4,980 to "'6,030 ft; 

-1,518 to ""1,838 m) 

A few upper Eocene foraminifers were 

encountered at 4,590 ft (1,509 m) (TuPboPotatia 

aoaoaensia and T. aePPoazutenaia), but are 

considered to have been redeposited in the 

Oligocene. At 4,980 ft (1,518 m), the first in 

situ Eocene planktic assemblage appears and 

contains Gtobigepinatheka mexiaana and Gk. 

aemiinvotuta, which mark the lower part of Zone 

P.l5. Thus, the uppermost Eocene as well as the 

lowermost Oligocene is missing at the disconformable Eocene-Oligocene contact. 

At 5,190 ft (1,582 m), the first indication 

of middle Eocene rocks appears. Here, 

MoPozovetta spinutoaa, TPUnaoPotatoides POhPi 

and T. topitenaia mark the top of Zone P.14. A~ 5,220 ft (1,591 m) AaaPinina buttbr>ooki marks 

the top of Zone P.13, and at 5,310 ft (1 619 m) 

Sub bot ina fpontoaa marks the top of Zon; p. 12. 

At 5,730 ft (1,637 m), a suite composed of 

AaaPinina pentaaame~ta, A. npoedePmanni 

Subbotina inaequiapim, S. higginsi, and 

MoPozove t ta amgonensia marks the top of Zone 

P.ll. Zone P.1Q may be present above 5,490 ft 

(1,673 m) but was not recognized. 

At 5,490 ft (1,673 m), the youngest iower 

Eocene rocks of Zone P.9 contain MoPozovetta 

aauaasiaa. AaaPinina sotdadoenais formas typiaa 

and augulosa appear at 5, 550 ft (1 ,692 m). An 

interval of conspicuous redeposition of 

Paleocene planktic foraminifers oc~urs between 

5,840 and 5,890 ft (1,780 and 1,75'5 m), where 

AaaPinina p~eauPBOPia, A. tPinidaiensis, and 

PtanoPotatites aompPesaa appear. (A. p~eauPBOPia was also noted in the sidewall'core 

at 5,840 ft (1,780 m).) However, sidewall cores 

and cuttings below this interval contain a 

progressively older suite of lower Eocene 

assemblages. Zone P. 8 is marked at 5, 840 ft 

(1, 780 m) by MoPozoveUa for>masa, at 5, 920 ft 

(1,804 m) by M. aubbotinae, and at 5,960 ft 

(1,817 m) by M. gmaitis. 

At 5,990 ft (1,826 m) in both cuttings and 

a sidewall core, the middle of Zone P.7 is 

indicated by the appearance of MoPozovetta 

maPginodentata. Zone P.6 is marked at 6,020 ft 

(1 ,835 m) by the appearance of Subbotina ve tasaoensis , MoPozove t ta ve taaa:Jenais , M. 

aauta, and M. simulatitis. A few redeposited 

specimens of Cretaceous globotruncanids also are 

present at 6,020 ft. 

Paleocene rocks 

In situ foraminifers of Paleocene age have 

not been recognized in the COST Nc. B-3 well. 

This is in accord with the record of calcareous 

nannofossils and palynomorphs (Valentine, this 

volume; Steinkraus, 1979). However, the 

presence of scattered Paleocene specimens 

(Aaar>inina pmeauPBOPia, A. t.,..·:nidadensia, 

Ptanopotatitea aompPeaaa, MoPozoveUa 

kotahidiaa, and M. pusitta forma typiaa) in the 

interval from 5,840 ft (1,780 m) to 6,020 ft 

(1,835 m) is evidence that upper Paleocene rocks 

were originally deposited in the vicinity of the 

well site and have since been eroded. Paleocene 

rocks are also missing from the COST No. B-2 

well (fig. 24). 

Maestrichtian rocks ("-'6,030 ft to ..... 6, 110 ft; 

""1,838 to -1,862 m) 

The youngest Cretaceous rocks in the COST 

No. B-3 well occur at 6,030 ft (1 ,838 m) and 

contain a diverse planktic assemblagn, including 

GtobotPunaana aontusa, Gt. Posetta, Gt. etevata, 

G-1; • · a Pea , Gt • af f • atuaPt if or>mia , Gt • stephensoni, Gt. patettifor>mis, Rugogtobiger>ina 

PUgoaa, Rg. hexaaamemta, and VentitabPelta 

muttiaamemta. This assemblage, in conjunction 

with Gt. ganaaePi at 6,040 ft (1,841 m; 

Steinkraus, 1979), is indicative of Zones UC 13 

and 14 of the lower Maestrichtian. The benthic 

foraminiferal assemblage does not undergo as 

drastic a change from the lower Eo~ene as the 

planktic assemblage does, but the ar~earance of 

the benthic species GtoboPotatitea miahetinianua 

and BPizatina inaPassata confirms the Late 

Cretaceous age at 6,030 ft (1,838 m). 

52 
Campanian rocks (-6,110 to-6,420 ft; 

-1,862 to ...... 1,957 m) 

The top of the Campanian Zone UC 12 is 

recognized at 6,110 ft (1,862 m) by the highest 

occurrence of G~obotrouncana ventroicosa and 

Neof~abe~~ina rougosa. A major increase in the 

abundance and diversity of benthic species 

accompanies this planktic datum. At 6, 240 ft 

(1,902 m), Gt. calcaroata in a sidewall core and 

Bo~ivinoides decor>atus in the cuttings mark the 

top of Zone UC 10. The first Epistomina 

supr>acr>etacea appears at 6,380 ft (1,945 m). 

Santonian rocks (~6,420 to ...... 7,040 ft; 

...... 1, 957 to .... 2, 146 m) 

Santonian rocks are marked by the 

appearance of Bo~ivinoides stroigi~latus at 6,429 

ft (1,957 m). It is accompanied by a few 

specimens of Maroginotr>uncana angusticar>enata. 

Mar>ginotr>uncana r>enzi appears at 6,510 ft (1,984 

m). At 6,526 ft (1,989 m) Mar>ginotrouncana 

concavata, found in a sidewall core, marks the 

top of Zone UC 8. G~oboroota~ites mu~tiseptus is 

frequent at 6,580 ft (2,006 m),- and the first 

frequent occurrence of Epistomina supr>acr>etacea 

is at 6,680 ft (2,036 m). At 6,860 ft (2,091 

m), Mar>ginotr>uncana pseudo~inneiana becomes 

conspicuous and the first Mt. concavata along 

with Ar>chaeog~obiger>ina hosquensis, occurs in 

the cuttings. 

Coniacian rocks ("'7,040 to "'7,900 ft; 

...,2, 146 to,...2, 408 m) 

The top of the Coniacian section is 

tentatively placed at 7,040 ft (2,146 m) on the 

basis of the appearance of Mar>ginotrouncana 

maroginata and Whiteinel~ arochaeocr>etacea. The 

Coniacian top may be somewhat deeper in the 

well, however, because elsewhere both Mt. 

maroginata and Wt. arochaeocr>etacea are known to 

range up into the lower Santonian. Epistomina 

steUiger>a forma typica, which is apparently 

restricted to the Coniacian and Turonian of the 

Scotian Basin (Ascoli, 1976), appears in 

moderate abundance at 7,130 ft (2,173 m). 

Steinkraus (1979) reported G~obotrouncana siga~i 

and Gt. schneegansi in cuttings at 7,110 ft 

(2,167 m), but I did not observe Gt. schneegansi 

in cuttings higher than 7,380 ft (2,249 m). It 

occurred in the sidewall core at 7,490 ft (2,283 

m), along with Hedberoge~~a amabilis. 

Turonian rocks ( ...... 7,900 to ...... 8,260 ft; 

"'2,408 to ...... 2,518 m) 

The lithologic, paleoenvironmental, and 

faunal changes across the Coniacian-Turonian 

transition suggest that a disconformity 

separates these stages. The first Turonian 

assemblage occurs at 7,900 ft (2,408 m) and 

contains Pr>aeglobotr>uncana stephani, which marks 

the top of Zone UC 4 of the lower Turonian; it 

is accompanied by Gave~inopsis tour>ainensis. 

Just above this level, a fine-grained sendstone 

from 7,610 to 7,810 ft (2,320 to 2,381 m) 

contains sparse inner shelf faunaP with 

scattered glauconite grains, coal, and gypsum 

(Lachance, 1979; this paper, fig. 27). Thus, 

the middle and upper Turonian and perhaps part 

of the lower Coniacian appear to be missjng from 

the COST No. B-3 well. 

At 7,990 ft (2,435 m), Gavel.inopsis 

tour>ainensis has a more strongly inflated umbo 

than in higher samples. At 8,080 ft (2,463 m) 

and 8,170 ft (2,490 m), Pg. stephani is more 

abundant and develops a more varied 

morphology. Lingu~ogave~ine~~a tur>onica appears 

at 8,170 ft (2,490 m) • 

Cenomanian rocks (""8,260 to -9,170 ft; 

...... 2,518 to~2,795 m) 

The first rotaliporids markir~ the 

Cenomanian (Zone UC 3) appear at 8,260 ft (2,518 

m) • At this level, Rotalipor>a cushm'lni, R. 

groeenhor>nensis, and R. r>eiche~i occur together, 

an association which suggests that the uppermost 

Cenomanian rocks are missing. Gave~inopsis 

eenomanica and Gave~ine~~a ba~tiea alsc appear 

at 8,260 ft. At 8,490 ft (2,588 m), the 

appearance of Favuse~~a washitensis marks the 

top of the lower Cenomanian Zone UC 2. 

Albian rocks ( ...... 9,170 (?) to,.,9,530 ft; 

...,2, 795 to "'2, 905 m) 

The first diagnostic foraminifer of Albian 

age, Favusella cf. F. seitu~a, appears at 9,170 

ft (2, 795 m) and indicates Zone LC 19 (' .. ichael, 

1972). This level is 500 ft (152 m) below the 

top of the Albian as recognized on the basis of 

palynomorphs (Steinkraus, 1979). TI1is low 

position of the first Albian foraminifer~ may be 

the result of environmental exclusion from the 

higher beds. The interval from 8, 710 to 9,170 

ft (2,655 to 2,795 m) consists chiefly of gray, 

slightly sandy shale and mudstone with thin coal 

laminae, sandstone beds, and limestone nodules 

in places (Lachance, 1979). The foraminiferal 

fauna is very sparse, terrestrial palynomorphs 

are abundant, and inner shelf to marginal-marine 

paleoenvironments are postulated for the 

interval. 

At 9,350 ft (2,850 m) the first assemblage 

of abundant F:pistomina spinu~iferoa form"" eo~omi 

appears, and at 9,410 ft (2,868 m) Favuse~~a 

nitida and F. pessagnoi appear as rare 

specimens. 

Aptian rocks (~,530 to -10,070 ft; 

"'2, 905 to "'3, 069 m) 

The top of the Aptian Stage is placed at 

9,530 ft (2,905 m) on the basis of palynomorphs 

(Steinkraus, 1979). The forminiferal evidence 

for Aptian rocks is not strong, but the benthic 

species Gave~ine~~a bar>r>emiana, which ranges no 

higher than the Aptian in the Scotian Basin 

(Ascoli, 1976), first appears at 9,530 ft. The 

53 
remaining Aptian interval contains sparse foraminiferal and nannofossil assemblages owing to 

the shallow-water paleoenvironment. 

Barremian rocks (~10,070 to ~10,500 ft; 

~3,069 to~3,201 m) 

Barremian rocks were first recognized at 

10,070 ft (3,069 m) on the basis of palynomorphs 

(Steinkraus, 1979), but no significant change 

was observed in the sparse foraminiferal 

assemblages near this level. The lower part of 

the Barremian interval is especially sparse in 

foraminiferal remains, and the thick-bedded, 

coaly sandstones in this interval appear to be 

of nonmarine origin. 

Hauterivian rocks (-10,500 to -10,770 ft; 

-3,201 to -3,283 m) 

Hauterivian rocks were recognized on the 

basis of palynomorphs within a shaley limestone 

at 10,610 ft (3,234 m) (Steinkraus, 1979). The 

foraminiferal faunas are very sparse, probably 

because the limestone is indurated, but they 

presumably were deposited in a shallow-marine 

paleoenvironment. A disconformity may separate 

the nonmarine Barremian sandstone and the 

Hauterivian limestone, and the top of the 

Hauterivian is placed at this contact. 

Valanginian rocks (-10,770 to -11,920 ft; 

-3,283 to -3,633 m) 

A rich assemblage of agglutinated benthic 

forminifers appears abruptly below the 

Hauterivian limestone at 10,770 ft (3,283 m). 

Prominent constituents are ~VePticyclammina 

ViPguliana and HaplophPagmium sp. In the 

Scotian Basin, ~. viPguliana (=BuccicPenata 

italica of Ascoli, 1976) does not range above 

the Valanginian, and on this basis, the top of 

the Valanginian section is placed at 10,770 ft 

(3,283 m). 

Berriasian rocks (-11,920 to -12,260 ft; 

"-'3,633 to "'3, 737 m) 

The top of the Berriasian Stage is placed 

at 11,920 ft (3, 633 m) on the basis of 

palynomorphs (Steinkraus, 1979). The benthic 

foraminiferal assemblage is moderately well 

developed, but no diagnostic species were 

recognized. This lack of foraminiferal 

definition extends to the Scot ian Bas in, where 

Ascoli (1976) also was unable to separate 

Berriasian and Valanginian foraminiferal 

assemblages. 

Tithonian rocks (-12,260 to -13,390 ft; 

-3,737 to~,081 m) 

The highest occurrence of Jurassic 

foraminifers, representing the Tithonian Stage 

is at 12,260 ft (3,737 m), where Rpistomina 

dnepPica appears. This is one of the species 

that Ascoli (1976) used to recognize Tithonian 

rocks in the Scotian Basin. At 12,500 ft (3,810 

m) in the rotary cuttings, and at 12,510 ft 

(3,813 m) in a sidewall core, two more of 

Ascoli's (1976) Upper Jurassic markers appear: 

Epistomina uhligi, in abundance, and a few E. 

mosquensis. The placement of tl?. TithonianBerriasian boundary is perhaps the most controversial boundary problem in the Baltimore Canyon 

trough and Scotian Basin (Ascoli, 1976; 

Steinkraus, 1979, Valentine, tl'iS volume). 

Based on this study, the place~ent of the 

boundary in the B-3 well is approximately the 

same as that of Steinkraus (1979), who placed it 

at 12,400 ft (3, 780 m) on tl'e basis of 

palynomorphs and calcareous nannofossils. 

However, Valentine's interpretation of the 

calcareous nannofossil assemblages (Valentine, 

this volume) places the top of the Tithonian 

approximately 1, 200 ft (366 m) lo··Ter than the 

foraminifers indicate. 

The major reasons for using the Scotian 

Basin boundary events are the lar~e number of 

wells (more than 20) analyzed by Aqcoli and his 

colleagues and the intercorrelatio1' of foraminiferal, palynomorph, and calpionellid datums in 

the Scotian Basin and Grand Banks (Ascoli, 1976, 

and personal communication, 1978; Gradstein and 

others, 1975). The calpionellidE' are shortranging planktic organisms (restd.cted to the 

oldest Cretaceous and youngest Jurassic rocks) 

and appear to offer the best possibility for 

accurate correlation with the Tithonian Stage in 

Europe. 

The COST No. B-3 well Titho"lian foraminiferal datum has also been recognized in the 

COST No. B-2 well, and the original placement of 

the boundary in the B-2 well has been raised 

from below 16,043 ft (4,848 m; Scholle, 1977) to 

11,830 ft (3,606 m; Poag, 1979). This agrees 

with a re-vision of COST No. B-2 well 

palynomorph interpretations carr1.ed out by 

Bebout (J. Bebout, written communication, 1978; 

Amato and Simonis, 1979, pl. 2). 

Kimmeridgian rocks (-13,390 to -15,390(?) ft; 

..... 4,081 to -4,691(?) m) 

The first foraminiferal evidence of 

Kimmeridgian rocks is the presence of Kuronubia 

palestinensis at 13,390 ft (4,081 m) (Ascoli, 

1976). This is 170 ft (52 m) below the highest 

Kimmeridgian palynomorphs (Steinkraus, 1979). 

At 14,000 ft (4,267 m), Alveosepta jaccaPdi, an 

agglutinated benthic foraminifer, marks the 

approximate top of the lower Kimmeridgian 

(Ascoli, 1976). At 14,320 ft (4,365 m), 

Epistomina stellicostata, ~. madagxscaPiensis, 

and Eoguttulina liassica are present. 

54 

Callovian(?) rocks (""15,390 to -15,820 ft; 

"'4,691 to "'4,822 m) 

No specimens older than Kimmeridgian in age 
were found among the palynomorphs (Steinkraus, 

1979) or calcareous nannofossils (Valentine, 

this volume) in the COST No. B-3 well, but at 

15,390 ft (4,691 m), the benthic foraminifer 

Epistomina eo~onata may indicate that Callovian 

rocks were penetrated. This species and 

Gamntella o~ta, which appears at 15,420 ft 

( 4, 700 m), range no higher than the Callovian 

Stage in the Scotian Basin (Ascoli, 1976). 

PALEOENVIRONMENTS 

Data and Interpretations 

The discussion of paleoenvironments, in 

contrast to that of the biostratigraphy, follows 

the chronology of deposition from the bottom of 

the well to the top. This treatment is based 

primarily on foraminiferal assemblages, but it 

also incorporates other faunal and floral 

elements as well as the lithology (Amato and 

Simonis, 1979), especially in considering the 

Jurassic and Lower Cretaceous rocks. A 

paleobathymetric curve for the B-3 well 

accompanies figure 23; it can be compared to 

that for the B-2 well in figure 24. A paleoenvironmental cross section is illustrated in 

figure 26. (See Steinkraus, 1979; Bebout and 

Lachance, 1979; and Valentine, this volume, for 

alternative interpretations.) 

The reader is reminded that the water 

depths given herein are gross estimates, and 

their imprecision increases in proportion to the 

age of the faunas and floras. This is 

especially true for the Mesozoic assemblages 

because all of the species and most of the 

genera are extinct. Furthermore, the seismic 

profiles show that terms like "inner shelf" and 

"upper slope" probably lacked today's 

physiographic meaning at the time of deposition 

of some of the rock units in the Baltimore 

Canyon trough (for example, during the 

Eocene). Nevertheless, the depth estimates are 

useful in conveying the relative changes in 

water depth through time, and they provide a 

point of departure for future studies of the 

depositional cycles of this basin. 

The oldest rocks in the COST No. B-3 well 

(Callovian(?) through early Kimmeridgian; 15,820 

to 14,500 ft; 4,823 to 4,421 m) contain very 

sparse, scattered foraminiferal assemblages of 

low species diversity. Epistominids and 

Eoguttulina are the predominant forms. The 

lithic components are interlaminated gray shale, 

gray oolitic limestone, and thin, light-gray to 

white sandstone beds interbedded with several 

thin coal beds (fig. 27). The sandy, coaly beds 

may represent alternating shallow-marine and 

coastal-marsh deposits (fig. 26), but the 

limestones appear to be shallow-marine "backreef" deposits associated with the carbonate 

platform that formed the Late Jurassic shelf 

edge about 6 mi (10 km) seaward (eastward) of 

the COST No. B-3 well site (fig 26; Schlee and 

Grow, this volume) • The low percentege of 

terrestrial palynomorphs in this section (Bebout 

and Lachance, 1979) suggests that during most of 

the deposition, the continental shorelir~ was 

not near the well site in spite of the shallowwater conditions. However, the shoreline must 

have lain between the B-3 and B-2 well sites. 

The B-2 is projected about 22 mi (35 km) up 

depositional dip from B-3, and nonmarine shales 

and sandstones inter-bedded with coal beds 

accumulated at B-2 during this time interval 

(fig. 26). 

During deposition of the rest of the lower 

and upper Kimmeridgian and lowest Tithonian 

rocks (14,500 to 13,100 ft; 4,421 to 3,9J4 m), 

slightly deeper water depths generally pre'•ailed 

at the B-3 well site. Epistominids are 

frequent, and T~oaholina and Lentieulina are 

common. Al.veosepta and Eve~tieyalammina occur 

sporadically, but are abundant at 14,020 ft 

(4,274 m) and 13,160 ft (4,012 m) respectively. The percentage of terre~trial 

palynomorphs did not change appreciably, b·'t the 

amount of limestone increased and coal be~s are 

absent. Water depths probably did not exceed 

160 ft (50 m). 

The zone of foraminiferal sparsity b~tween 

13,100 and 12,700 ft (3,994 to 3,872 m) pr~bably 

resulted from the induration of the limeqtone, 

but "middle- shelf" assemblages return across 

the Tithonian-Berriasian boundary (12,710 to 

11,900 ft; 3,872 to 3,628 m) as sandstone and 

shale become the predominant lithofacies. 

Epistominids predominate and acc~mpany 

Ophthalmidium, T~oeholina, T~istix, Lentie·,z.ina, 

and often abundant Ma~ssonel.Z.a. 

Most of the interbedded sands tone, shale, 

limestone, and siltstone of the Valan~inian 

Stage (fig. 27) encloses a sparse b~nthic 

foraminiferal assemblage, mainly episto~inids 

and lenticulinids, that indicates marginal 

marine conditions. However, at the top of the 

Valanginian, a rich assemblage of agglutinated 

benthic foraminifers (Eve~tiayalammina, 

Hapl.oph~agmium), along with a few episto~inids 

and spirillinids, accompanies a significant 

decrease in terrestrial palynomorphs (Bebo·tt and 

Lachance, 1979). This is interpreted as a 

transgressive marine pulse that produced water 

depths of about 160 ft (50 m) at the COST No. B3 well site (figs. 23 and 26). 

Just above the uppermost Valanginian, a 

250-ft (76-m) interval of Hauterivian shaley 

limestone (fig. 27) yielded essentially no 

calcareous marine microfossils, probably b~cause 

it is indurated, but it undoubtedly represents 

shallow-marine paleoenvironments. The 100-ft 

(30-m) -thick Barremian sandstone overlying the 

Hauterivian limestone (fig. 27) is barren of 

microfossils and is thus interpreted as to 

having been deposited in nonmarine conditions; 

as a result, a disconformity is recognized at 

the Barremian-Hauterivian contact. 

55 
COSTAMCOR 

B-2 6010 

L,SE/SMIC 

( '::JHOT POINT 

NW 2400 2500 2600 

o~==~~==~==========~==~==~==============~~==== 

2700 

en 

0::: 

IJ.J 

t;J3 

::E 

0 

....J 

~4 

~ 

0 

0 

I 

5 

5 

I 

10 15 MILES 

10 KILOMETERS 

I 

Figure 26.--Paleoenvironmental cross section along USGS Seismic Line 25. (See figs. 22 and 25.) 

Heavy lines show approximate position of faults and outline of carbonate platform 

The remaining Barremian and the Aptian 

rocks (10,350 to 9,550 ft; 3,155 to 2,911 m) are 

interbedded, light-gray sandstones, dark-gray to 

black shales, soft white limestones, and thin 

siltstones (fig. 27). The foraminifers in this 

interval are scattered small assemblages of 

epistominids, lenticulinids, and gavelinellids, 

plus frequent microgastropods. The percentage 

of terrestrial palynomorphs is quadruple that of 

the lower Barremian and Hauterivian. These 

rocks are interpreted as having accumulated in 

shallow-marine conditions of not greater than 

65-ft (20-m) depth. 

Similar faunas persist up to 8,550 ft 

(2,606 m) in Cenomanian rocks consisting chiefly 

of light-gray to brown shale and white sandstone 

(fig. 27), and a similar shallow-marine paleoenvironment is inferred. A significant exception occurs between 9,550 and 9,300 ft (2,910 to 

2,835 m), where an assemblage of abundant 

Epistomina spinulife~, gavelinellids, and a few 

favusellids appears in the lower part of a zone 

of limestone nodules. The decrease in terrigenous lithic components, the more abundant 

foraminifers, and the inclusion of planktic 

species (favusellids) suggest that slightly 

56 

deeper marine conditions, 160 ft ( 50 m), 

prevailed during deposition of this interval. 

From 8,550 to -8,230 (2,606 to -2,509 m), 

Cenomanian foraminiferal assembla~es become 

increasingly richer in specimens a"'l'.d species, 

and planktic forms gradually b?.come more 

frequent as the lithology changes from fine 

sandstone to shale (fig. 27). The foraminiferal 

assemblage is richest at the teo of this 

interval (8,260 ft; 2,518 m), where it consists 

of abundant gavellinellids, lingulogavelinellids, gavelinopsids, and l~nticulinids 

as well as frequent rotalip~rids and 

praeglobotruncanids. "Middle-shelf" conditions 

that include a water depth of about 270 ft (80 

m) may be inferred for this interval. 

Above a disconformity that separates 

Cenomanian and Turonian ro~ks (see 

"Biostratigraphy" section), shallcw "middleshelf" conditions accompanied deposition of gray 

Turonian shale (8,230 to 7,850 ft; 2,509 to 

2, 393 m; fig. 27). These foraminiferal 

assemblages are not as rich as those at the top 

of the Cenomanian, but they are similar in 

generic composition. Among the planl:tic genera, 

the Cenomanian rotaliporids are not present, but 

P~eglobotPUncana is frequent. 
SEISMIC 

liNE SPLICE 

AMCOR COST 

6021 B-3 

\ 

1:·:-:·:·:i NONMARINE FACIES 

I ISHELF FACIES ~~~1SLOPE FACIES 

\ 

SEA SURFACE 

CARBONATE 

PlATFORM 

ROOO 1-

w 

w 

L&.. 

12000 ~ 

:I: 

1-

a.. 

w 

'6000° 

20000 

24000 

Drill sites have been projected approximately along strike to intersect the seismic profile. 

section; these lines are dashed where data is sparce or difficult to interpret. 

Above the Turonian shale lies a 200-ft (61-

m)-thick, glauconitic, fine-grained sandstone 

(7,810 to 7,610 ft; 2,381 to 2,320 m; Lachance, 

1979) containing sparse, poorly preserved 

foraminifers and scattered gypsum crystals. 

This striking change in lithology and fauna, in 

conjunction with the lack of evidence for upper 

and middle Turonian rocks (see "Biostratigraphy" 

section), leads to the inference that a disconformity separates the lower Turonian and the 

Coniacian, and this fits the interpretation of 

seismic stratigraphy along USGS Seismic Line 25 

(Schlee and Grow, this volume). On the other 

hand, one could argue that the sparsely 

fossiliferous sandstone may represent part of 

the upper and middle Turonian. 

From 7,710 to 6,110 ft (2,350 to 1,862 m), 

the Coniacian through Campanian foraminiferal 

faunas become increasingly rich and diverse, 

culminating in "upper-slope" assemblages ( 1,000 

to 1, 300 ft water depth; 300 to 400 m) between 

6,700 and 6,100 ft (2,042 and 1,859 m; fig. 

23) • The dominant lithology throughout this 

interval is interbedded light- to medium-gray 

mudstone and shale (fig. 27; Lachance, 1979). 

The Coniacian foraminiferal assemblages contain 

epistominids, ammobaculitids, karreriellids, 

bolivinopsids, spiroplectamninids, 

gavelinellids, lenticulinids, and a sparse 

planktic association. In the lower Santonian, 

planktic specimens are more ab·mdant; 

Bolivinita, Loxostomum, Eouviger>ina, Gyr>oidina, 

and a few bathysiphons appear. 

In the upper Santonian and Campanian rocks, 

very rich and diverse assemblages of both 

planktic and benthic foraminifers are present. 

Benthic forms include Pseudotext;:.~.lar>ia, 

Bolivinoides, Heter>ostomella, Do~othia, 

Gaudr>yina, Textular>ia, Anomalinoides, Br>i.~alina, 

Aroenobulimina, Stensioina, Neoflab':!.llina, 

Kyphopyxa, Clavulinoides, Mar>ginulina, 

Epistomina, Bathysiphon, Osang·.•laroia, 

Cr>ibr>ostomoides, Globor>otalites, and 

Siphouviger>ina. (See "Biostratigraphy" section 

for planktic species.) 

The uppermost Campanian and lower 

Maestrichtian rocks are brownish-gray calcareous 

mudstones (fig. 27) that contain a somewhat 

diminished fauna. The planktic assemblage is 

still rich, but the benthic abundance and 

diversity are reduced. Globor>otatites, 

BY'izalina, Gavelinella, Neoflalettina, 

Kar>r>er>iella, Pseudogaudr>yinetta, Ramulina, 

57 
? 

PERIOD EPOCH AGE ~ LITHOLOGY 

i 

DESCRIPTION 

(Dominant lithology is shown in capital letters) 

SEA LEVEL.: 

42 ft. below K B 

DEPTH 

FEET 

METERS 

1000-

500 

2000-

r----~~----------~----~-----4----+-------~SEA FLOOR~~~----~----~ iaUATER PL~~TO- 2728 ft. below K B 

1-N_A_RY-+~CE~N,:,:E=-::--1- - - - --- PLIOCENE --LATE __ _ 

>- 1- __ Ml.QC!_N!_ __ 

0:: MIOCENE MIDDLE <( MIOCENE 

- EARLY MIOCENE-..,. 

~ 1---t::::::==LA;;;T::;:E=~~R 0:: OLIGOCENE OLIGOCENE '.a.. 

L1J LATE EOCENE f ~ EOCENE MIDDLE EOCENE ~ 

-------

_-_-.J.. ___ ..L, __ -.-

(/) 

:::;) 

0 

w 

u 

<l: 

1-

w 

0::: 

u 

EARLy EOCENE R 

~} ~~":z MAESTRICHTIANJ ) fvvv. ~ ~ )-

w (/) 1-

::> :5 

zl-~~~~~ CAMPANIAN Vvvv-~~~ 

~ ~ 

~ SANTONIAN 

0 

z 

L&.J 

Cl) 

CONIACIAN 

EARLY TURONIAN 

CENOMANIAN 

~ R 

~ ·~ 

~~~~ 

t=-~:::: 

- - -------

------- .. ~ 

0 1-----i-------1 

w e- !-

(._) 

<( 

~ 

w 

a:: 

(._) 

(/) 

:::;) 

0 

w 

u 

<l: 

1-

w 

0::: 

u 

~ 0::: 

<l: 

w 

ALBIAN 

APTIAN 

BARREMIAN I T;; 1---T~~---~ HAUTERIVIAN ~ 

z 

~ 

::E VALANGINIAN 0 

(..) 

0 

L&.JI--------1 

z BERRIASIAN 

e------=-=-

.... ,._ .. ~ 

E=:=~~~ 

··~··· -~- ~t_ ~ i ~"'c....:....:._........c.._:...._-:::.....:...:j ~E "'""! 

........ -s;:)L.- 1--___ -:: 

!:=::::=--=-~ j '==.=-----= 

L1ght-olive-gray CLAY w1th foramimferal test fragments, orgamc streaks, and glaucomte Traces 

of glaucon111c sandstone 

3000-

1-1000 

4000-

r-15ggoo- l-------------~ 

White biomicritic LIMESTONE w1th foram;mfera 

and wh1te to light-gray, calcareous CLAYSTONE 

ranging to CHALK. 

Dark- brown-gray, calcareous s1lty MUDSTONE, 

gray claystone, and thin beds of green glauconitic sandstone and hard, brown, blocky dolomite. 

6000-

1-2000 

1ooo8000 

l---------------r2500 

9000 

- 11 ooo1-3500 

12 000-

TITHONIAN '~ 

.. · . . . ~ : r-l688°-

(._) :.:..:..:. .... ~ .. :- . -:-...: ...; t_ Tan, brown, and gray, hard and dense LIMESTONE 

(/) 

(/) 

<( 

a:: 

::> 

J 

w 

1-

<l: 

__J 

LATE 

KIMMERIDGIAN 

EARLY 

KIMMERIDGIAN 

OXFORDIAN(?) 

1-----4- - - - - -

~~~~~~~ CALLOVIAN(?) 

........ (pelletal, oolil1cl and mtraclastic grainstones 

"'§ !0-: -:- · · : : . ~ '= and packstones and Interbedded wh1te and 

- gray, line- to medium-grained SANDSTONE. 

:=---=---= 

----

Dark -gray, brown, and black, fissile, micaceous 

; SHALE and COAL beds abundant in lower half 

~ of interval 

~ ~ 

L 

[F:-

. 14 ooor4500 

15 000-

Figure 27.--Lithologic column for the COST No. B-3 well showing lithologic symbols, short 

lithologic description, foraminiferal biostratigraphy, and geophysical-log 

characteristics. "R" next to spontaneous-potential curve indicates lC'~ation of 

lithologic contacts that are easily recognized as strong reflectors on USI'";S Seismic 

Line 25. Lithologies modified from Amato and Simonis (1979, pl. 2). 

58 
Bulimina, Osangutaroia, and Croibroostomoides are 

typical benthic constituents. This is interpreted to be an "outer-shelf" assemblage of 

about a 500- to 650-ft ( 150- to 200-m) water 

depth. 

The change in benthic foraminifers across 

the lower Eocene-lower Maestrichtian contact is 

not dramatic, although the planktic assemblage 

changes significantly. The lithologic change 

also is a significant one in which the brownishgray mudstone changes upward to white 

biomicritic limestone (fig. 27; Adinolfi and 

Jacobson, 1979). The absence of the Paleocene 

Series here and at the COST No. B-2 well site 

(figs. 23 and 24) is evidence of a major, 

widespread disconformity (see "Biostratigraphy" 

section). 

Benthic species in the lower Eocene 

interval from 6,030 to 5,900 ft (1,838 to 1,798 

m) include members of Troitaxia, Lenti~utina, 

Vaginulinopsis, Bulimina, Cibi~ides, 

Gonatosphaeroa, Croibroostomoides, Marossonel la, 

Pseudogaudroyinetta, Osangularoia, 

El lipsoglandutina, A tabamina, and Gavelinel.ta, 

which suggest an "outer-shelf" paleoenvironment 

of around a 650-ft (200-m) depth. 

From 5,900 to~5,400 ft (1,798 to ~1,646 m; 

lower to lower middle Eocene), the benthic 

assemblages are difficult to interpret. Species 

representing continental-slope conditions are 

abundant, but they may be cavings from the 

overlying "lower-slope" assemblages, as will be 

explained later. Another association, 

consisting of "outer-shelf" species, is also 

present in this section, and is absent or rare 

above; it includes species of Rosalina, 

Cibi~ides, and Nuttat tides. These species may 

represent the in situ assemblage here, but 

further analysis is required to confirm it. 

There is also an interval from 5,900 to 5,800 ft 

( 1, 798 to 1, 768 m) in which the benthic 

forminifers are almost completely absent; this 

may be due to diagenesis of the chalky white 

limestones and calcareous claystones that 

characterize must of the Eocene section 

(Adinolfi and Jacobson, 1979, pl. 2; fig. 27). 

Diagenetic alteration of early Eocene 

microfossil assemblages seems to be widespread 

along the Atlantic shelf and slope (Poag and 

Hall, 1979). 

From~5,400 to 5,050 ft (1,646 to 1,539 m), 

the highly calcareous claystones and limestones 

contain the richest, most diverse benthic 

assemblages observed in the COST No. B-3 well. 

Hoeglundina, Osangularoia, large polymorphinids, 

Gyrooidinoides, Gavelinella, Heteroolepa, 

Vulvulina, Lenti~ulina, Pleuroostomella, 

Allomorophina, Cy~lammina, Karoroeroiella, Doroothia, 

Marossonella, Troitaxia, Bulimina, and many 

others, along with an equally rich and diverse 

planktic assemblage, indicate water depths 

probably in excess of 3,000 ft (1,000 m). 

At the top of the Eocene section, many of 

the same species of benthic foraminifers are 

present in abundance, but some of the deeper 

59 

water forms, such as Pleuroostomella, 

Allomorophina, and Cy~lammina are replacec by 

somewhat shallower water forms such as costate 

Uvigeroina. This suggests a "lower slope" 

environment of around a 1,600- to 2,300-ft (500-

to 700-m) depth. 

Oligocene and most of the early Miocene 

faunas maintain the "lower slope" asp~ct, 

although the species and lithology change. 

Light-olive-gray clay and green-gray to browngray calcareous mudstone compose these strata 

(fig. 27; Lachance, 1979); they contain large 

polymorphinids, Lenti~ulina, Uvigerina, 

StilostomeHa, Cibi~ides, Vulvulina, Troita.xia, 

Nodosaroia, Planulina, Vaginulinopsis, 

MarotinottieUa, Siphouvigeroina, spinose and 

costate Uvigeroina, Siphogeneroia, and 

Hoeglundina, which suggest water depths of 1,600 

to 2,300 ft (500 to 700 m). Radiolarians become 

an important biogenic component of the Oligccene 

rocks; and their increasing abundance, elong 

with that of diatoms, in the Oligocene and 

Miocene strata suggests a surge in primary 

organic productivity in the photic zone. 

At ~4,500 ft (-1,372 m) the berthic 

foraminiferal assemblage changes. The diversity 

of species diminishes and the large-~ized 

specimens characteristic of the preceding 

assemblages disappear. Uvigeroina rousti~a is 

abundant, accompanied by Bulimina, Cibi~ides, 

Marotinottie lla, Nodosaroia, and Amphimorop1:in.a. 

This assemblage suggests "upper slope" depth; of 

"'1, 000 ft (-300 m); it persists intermittently 

throughout the lower two-thirds of the mi.ddle 

Miocene strata (4,500 to 4,000 ft; 1,372 to 

1,219 m), along with increasingly abur1ant 

diatoms and radiolarians. 

The simplest explanation for the biogenicsilica enrichment of the clays and mudstones of 

the Oligocene and Miocene strata (especially the 

middle Miocene) is the upwelling of nutrtentladen bottom water along the shelf edge. At 

least five factors may be used to infer that 

upwelling was a significant contributor to this 

association: (1) Increased ratio of diatoms and 

radiolarians to foraminifers, ( 2) presenc?. of 

cold-water diatom species, (3) intermittent 

zones of leached foraminiferal tests, (4) high 

organic-carbon content in sediments, and (5) 

high percentage of amorphous (algal) kerogen in 

the organic carbon. 

1. Ratios of diatoms and radiolarians to 

foraminifers (~ opal/calcite) begin to 

increase significantly in the Olig~cene 

and reach an acme in the middle Mio~ene. 

Beneath normally fertile surface waters, 

bottom waters and interstitial water~ are 

undersaturated with respect to opaline 

silica, and siliceous skeletons are not 

preserved (Berger, 1975). Supplies of 

opal large enough to saturate the b"lttom 

and interstitial waters are generated 

mainly in upwelling regions (DiesterHaass, 1978). The excellent preservation 
of the diatoms and radiolarians in the 

COST No. B-3 well is symptomatic of opal 

saturation or of sedimentation rates high 

enough to shelter opaline organisms from 

undersaturated bottom waters. 

2. Although the diatom floras of the B-2 and B3 wells have not yet been studied, at 

updip locations elsewhere on the Atlantic 

margin, middle Miocene diatom assemblages 

contain cold-water benthic species (Poag 

and Hall, 1979; Abbott, in press). 

Upwelling waters are characteristically as 

much as 16°F (9°C) colder than surrounding 

surface waters (Diester-Haass, 1978). 

3. Upwelling regions are sites of poor 

preservation of calcium carbonate, owing 

to the enrichment of co2 in the 

interstitial water of surface sediments 

that results from the enormous expansion 

of biologic productivity (Berger, 1974). 

Several zones of severely leached benthic 

foraminiferal tests are present in the 

middle Miocene strata of the COST No. B-3 

well. The inferred upper slope 

paleoenvironments normally would be 

considered to have been shallower than the 

lysocline. 

4. Sediments of upwelling regions contain 

significantly more organic carbon than 

surrounding regions (Diester-Haas, 

1978). The organic-carbon content of the 

Oligocene and Miocene strata is the 

highest in the COST No. B-3 well, except 

for a thin zone of Callovian(?) age at the 

bottom of the well (Smith, 1979). In the 

COST No. B-2 well, the organic-carbon 

content of Oligocene and Miocene rocks is 

greater than that of any of the other rock 

units younger than the Valanginian 

(Claypool and others, 1977). 

5. About 50-80 percent of the kerogen in the 

Oligocene-Miocene strata of the COST No. 

B-3 well is the amorphous type (algal 

bodies and amorphous sapropel), indicating 

that most of the kerogen is of marine 

origin. In the COST No. B-2 well, 

amorphous kerogen reaches a maximum of 80 

percent in the middle Miocene and 

diminishes in both younger and older rocks 

(Claypool and others, 1977). At both wl~l 

sites, these kerogens are enriched in C 

relative to adjacent strata, a phenomenon 

that Killingley and Berger (1979) have 

associated with upwelling. 

Enrichment in phosphate and fish remains, 

two additional criteria for identifying sediments associated with upwelling (Diester-Haass, 

1978), has been noted in Oligocene and Miocene 

sediments elsewhere along the u.s. Atlantic 

margin (Gibson, 1976; Hathaway and others, 1979; 

Poag, unpublished data). Analyses for these 

characteristics have not yet been carried out in 

the present area of study. 

Another aspect of middle Miocene deposition 

60 

that also probably influenced the development of 

silica-rich plankton communities W1'S an increase 

in terrestrially derived nutrients. As 

discussed by Poag (1977, 1978) and Schlee and 

Grow (this volume), the middle Mio~ene strata at 

B-2 and B-3 are parts of a prograding series of 

clinoform deltaic beds. At B-2, the inferred 

high nutrient content of Miocene shelf waters is 

reflected not only by the rich diatom flora, but 

by the benthic foraminiferal assembage as well 

(Poag, 1977; Seiglie, 1968). The rapid deposition of terrestrially derived organic-rich 

sediments (note the high sediment accumulation 

rates of the middle Miocene interYals, fig. 28) 

may have furnished a large part of the nutrients 

required for the diatom enricl -nent. This 

deltaic deposition also accounts for the other 

50 percent of the kerogen in the B-3 Miocene, 

which is herbaceous (plant cuticles, pollen, 

spores, resins, and waxy mate:rial; Smith, 

1979). However, the presence of the large 

Miocene delta does not account for the coldwater nature of the benthic diatom assemblage or 

the apparently ubiquitous occurrence of rich 

Miocene diatom assemblages all along the u.s. 

Atlantic margin. Thus, the eowelling and 

deltaic deposition may have combir~d to produce 

the diatom-rich Oligocene and Miocene sediments 

in the Baltimore Canyon trough. 

At 4, 000 f t (1 , 219 m) , the triddle Miocene 

foraminiferal faunas of the COST No. B-3 well 

begin to lose the upper slope: components. 

Bulimina maPginata, Bulimina elon(Jata, Bulimina 

alazanensis, CyPoidina, Clobobulimina, Me lonis 

baPleeanus, and UvigePina constitute an outer 

shelf assemblage. At 3, 900 ft (1, 189 m), 

Bulimina elongata becomes the trost abundant 

form, accompanied by FuPsenkoina, BPizalina, 

FloPilus, Epistominelta, Melonis, Islandiella, 

Clobobulimina, UvigePina, and Lenti~utina; this 

assemblage extends up to 3,810 ft (1,161 m), 

where the top sample was collected. A "middle 

to outer shelf" environment is inferred, 

probably of about a 300-ft (100-m) water depth. 

The paleoenvironments of the remaining 

unsampled upper part of the 1i'ell can be 

estimated from the other core h~les nearby. 

Presumably, the middle Pliocene transgression 

noted in the Southeast Georgia Eml 'iyment (Poag 

and Hall, 1979) and on other ocean margins (Vail 

and others, 19 7 7) would have produced "upper 

slope" conditions at the COST No. B·-3 well site. 

Pleistocene strata in the near~y AMCOR 6021 

core (figs. 25 and 26) consist of gray to darkgray, gassy, silty and sandy clays. These clays 

contain planktic foraminifers of temperate-water 

origin, and benthic foraminiferal associations 

range from "inner shelf" to "upper slope" in 

origin. Several intervals contain abundant dark 

organic particles and rich diatom floras along 

with "middle to outer she] f" benthic 

foraminifers. This association suggests 

accumulation in low-oxygen depres~ions on the 

shelf (Poag, 1978). Holocene sediments have not 

been differentiated in this study. 
AGE 6~!!! 

(M.Y.) ~"'~ 

5 

10 

15 

20 

25 

30 

35 

40 

45 

50 

55 

60 

65 

70 

75 

80 

85 

90 

110 

115 

2.0\ 

1.3\ 

~:3·····~·· ·· .. 

2.s····· .. 

3.3·· 

\2.0 

.\1.4 

' ·,3.3 

., 

···················· COST GE-l 

·-·-·-·-·- COST B-2 

COST 8-3 ------- PROJECTED SEGMENT 

Figure 28.--Comparison of sediment accumulation rates at the COST Nos. GE-l, B-2, and B-3 well 

sites. Numbers listed beside curves for the GE-l and B-2 wells record sediment 

accumulation rates in cm/1,000 yrs. Rates for the B-3 well are essentially identical 

to those at B-2, except as noted next to the B-3 curve. 

Discussion 

Figure 26 displays the inferred paleoenvironmental sequences (depositional cycles) 

along USGS Seismic Line 25 from the COST No. B-2 

well on the shelf to 6 mi (10 km) seaward of ASP 

15 on the lower slope. Parts of the section are 

somewhat diagrammatic and simplified, because 

the detail known at the well sites could not be 

61 

shown at the scale of the paleoenvironnental 

section. In the part of the Baltimore Canyon 

trough illustrated (and, by seismic extrapolation, it is inferred to be representative of 

the entire outer part of the trough; see Schlee 

and Grow, this volume), during the Middle(?) and 

Late Jurassic and Early Cretaceous, terrestrial 

environments dominated the B-2 site, and shallow 

marine (30-to 165-ft depth; 10 to 50 m), mixed 
clastic and carbonate environments prevailed at 

the E-3 site. The shoreline fluctuated back and 

forth, generally between seismic shot points 

2,400 and 2,500, as inferred from the pattern of 

seismic reflections (fig. 26), but occasionally 

it advanced or retreated considerably beyond 

this point. The most obvious exceptions are the 

transgression across the Tithonian-Berriasian 

boundary and the regression during the early 

Barremian. This group of rocks (Callovian(?) to 

Albian) maintains a uniform thickness from the 

B-2 to approximately the B-3 well site (fig. 

25). The fault block penetrated by the B-3 well 

contains a slightly thicker sequence, but the 

sequence thins rapidly southeastward onto the 

carbonate platform to approximately one-quarter 

the thickness at B-3 (Schlee and Grow, this 

volume; fig. 25). The Upper Jurassic "back 

reef" carbonate facies in the B-3 well represent 

the last stages in limestone-deposition associated with the carbonate plat;form. Shelf sediments began to override the carbonate platform 

perhaps as early as the Callovian(?) (figs. 25 

and 26), and a thick sequence of sedimentary 

rocks spilled across it during the Hauterivian 

to Cenomanian interval. Nevertheless, thinning 

across the platform indicates that it remained 

as a physiographic high until the beginning of 

the Cenomanian. After Cenomanian deposition, 

thinning across the top of the platform ceased 

(Schlee and Grow, this volume). 

Water depths began to increase in the 

Cenomanian and reached a Cretaceous maximum 

during the late Santonian and Campanian. 

Following a late Maestrichtian regression and a 

Paleocene hiatus, a major early to middle Eocene 

marine transgression deposited rich "outer 

shelf" carbonate deposits as far updip as the 

site of the USGS Island Beach well beneath the 

New Jersey Coastal Plain (fig. 22), while "lower 

slope" depths enveloped both the B-2 and B-3 

well sites. The Eocene rocks double in 

thickness from 1,150 ft (350 m) at the B-2 well 

to 2,300 ft (700 m), 16 mi (25 km) landward of 

the B-2 on an extension of USGS Seismic Line 

25. Presumably, depths equivalent to the modern 

~helf edge were reached between this location 

(16 mi or 25 km landward of B-2) and the Island 

Beach well, but there appears to have been no 

physiographic expression of the Eocene shelf 

edge comparable to that of the Miocene and 

Quaternary. During the late Oligocene, "slope" 

deposits continued to accumulate, but the 

terrestrial components of the rocks increased 

significantly. 

A gradual shallowing from "upper slope" to 

"inner and middle shelf" depths took place 

during the outbuilding of the middle Miocene 

deltaic wedge. The shelf edge appears to have 

migrated from shot point 2, 300 to about shot 

point 2,600 during the Miocene, judging from the 

prograding Miocene seismic reflectors that have 

close geometric similarity to those of the 

Pleistocene (Schlee and Grow, this volume). The 

thickest Miocene sequence was deposited beneath 

shot point 2,600 (fig. 25). The variety of 

Pleistocene paleoenvironments that have been 

penetrated on the present upper slope is the 

result of the interplay of glacial sea-level 

fluctuations and pulses of glaciof~wial clastic 

deposition. "Shelf" faunas apparently were 

commonly washed down onto the slope, and the 

shelf was exposed subaerially during low 

Pleistocene sea-level stands. 

HIATUSES 

The recognition of hiatuses in the Cost 

Nos. B-3, B-2, and GE-l wells is ltised chiefly 

on the absence of foraminiferal zo'les from the 

observed biostratigraphic sequences. These data 

are supplemented by paleoenvironm~ntal interpretations and lithologic changes. The oldest 

disconformity distinguished in tl?. B-3 well 

occurs at ~10,500 ft (3,201 m); it separates the 

Hauterivian from Barremian rocks an.d reflects a 

time gap of about 3-4 m.y. (time e~timated from 

accumulation-rate curve, fig. 28). The paleoenvironment changes from "middle shelf" 

conditions in the Hauterivian to nonmarine 

conditions in the lower Barremian. This change 

suggests that the disconformity wes caused by 

subaerial erosion. The lithology cbmges from a 

shaley limestone below to a shaley sandstone 

above the disconformity. The lithclogic change 

produces a significant contrast in interval 

seismic velocities (Carlson, 1979), which is 

recorded as a strong reflector on seismic 

profiles (Schlee and Grow, this volt'me). 

The next oldest significant cisconformity 

(at "'8,225 ft; "'2,507 m) separatef' "middle to 

outer shelf" assemblages of the late Cenomanian 

from "middle shelf" assemblagE'.S of the 

Turonian. The top of Zone UC 3 is missing in 

the biostratigraphic sequence, and the time gap 

is estimated to be "'1 m.y. or les~. The rock 

type changes from a thick quartzose sandstone 

below to a thick shale sequence above, approximately at the disconformity. The small time 

interval involved in the hiatus and the slight 

change in paleobathymetry suggest that this gap 

was created by submarine erosion at the B-3 

site. This disconformity is associated with a 

distinct reflector on seismic recorAs (Carlson, 

1979; Schlee and Grow, this volume). 

The absence of Zone UC 5 and Fart of UC 6 

in. the biostratigraphic sequence signifies that 

the upper boundary of the Turonian rocks in the 

B-3 well is also a disconformity (at "'7 ,850 ft; 

"'2, 393 m). A time gap of "'5 to 6 m.y. is 

postulated, and an equivalent gap is present at 

B-2 and at GE-l (fig. 28). Clearly, the late 

Turonian and early Coniacian are characterized 

by a regional regression along the Atlantic 

margin. The paleoenvironment below the hiatus 

is "middle shelf" and above is "ir'ler shelf," 

but the disconformable surface mar have been 

subaerially exposed during the peak regression. The Turonian shale gives Pay to dark 

silty mudstone in the lower Coniacian. This 

62 
horizon does not appear to produce a significant 

seismic reflector; but, on the other hand, it is 

so close to the disconformity bounding the lower 

Turonian that they may be inseparable on seismic 

records. 

The next major hiatus occurs at the 

Cretaceous-Tertiary contact. In the B-3 and B-2 

wells, the Paleocene Series (Zones P.l to P. 5) 

and the upper Maestrichtian (Zones UC 15 to UC 

17) are missing. The time gap is 17-18 m.y. At 

GE-l, a nearly coeval hiatus is present, but 

part of Zone P.4 (upper Paleocene) is preserved 

and only Zone UC 17 (uppermost Maestrichtian) is 

missing from the top of the Cretaceous (fig. 

28). To date, this is the most significant 

regional hiatus in terms of the chronologie gap 

that has been observed on the Atlantic margin. 

It can be traced easily on seismic reflection 

profiles (Carlson, 1979; Schlee and Grow, this 

volume). At B-3, the "outer shelf" paleoenvironment does not change across the 

dis conformity, but the lithology changes from 

dark silty mudstone to white biomicritic 

limestone. The missing section may have been 

eroded by a series of subaerial and submarine 

processes during this lengthy period (Vail and 

others, 1977; fig. 29). 

At B-2, however, the lithology and 

paleoenvironmental conditions are quite 

different. The Maestrichtian is represented by 

a lignitic, gypsiferous quartzose sandstone 

containing a marginal-marine assemblage of 

agglutinated foraminifers. Subaerial exposure 

clearly could have existed during or following 

deposition of this sandstone and prior to 

deposition of the overlying lower Eocene, "outer 

shelf," white limestone. 

At "'5,975 ft (1,821 m) in the B-3 well, a 

regional hiatus separates the late Eocene Zone 

P.l5 from late Oligocene Zones P.21-20. Zones 

P.19, 18, 17, and 16 are missing, a gap which 

spans "'8 m.y. (fig. 28). This hiatus is also 

present at B-2 and GE-l (fig. 28), although less 

of the section is missing in these wells. (The 

minimum gap is at GE-l where it spans ,..,5 m.y.) 

The paleoenvironment on either side of the 

disconformity at B-3 is equivalent to that of 

the modern lower slope. At B-2, a change occurs 

from an "upper slope" environment below the 

disconformity to an "outer shelf" environment 

above it. At these sites, as at GE-l (Poag and 

Hall, 1979), submarine currents seem to have 

been the erosive agent. 

A lithologic change from white Eocene 

limestone to olive-gray, glauconitic, Oligocene 

clay takes place in both B-2 and B-3. The 

resulting seismic-velocity contrast forms a 

distinctive reflector on seismic profiles 

(Carlson, 1979; Schlee and Grow, this volume). 

At "'4,450 ft (1,356 m), there is a gap 

between Zone N.9 of the middle Miocene and Zone 

N. 5? of the lower Miocene. Zones N. 8 through 

N .6 are missing and represent a hiatus of "'5 

m.y. Even greater gaps between the late 

Oligocene and middle Miocene are present at B-2 

("'9 m. y. ) and GE-l ("' 14 m. y. ) , they conf i rm the 

wide areal distribution of this disconformity. 

At B-3, the paleoenvironment changes from 

"lower" to "upper slope" depths acrof's the 

dis conformity, while at B-2 the change is from 

"outer shelf" to "inner shelf." Sul'llarine 

currents appear to have been the erosive agents 

at both sites. No lithologic charge is 

associated with this disconformity at B-3, but 

at B-2 a thin quartzose sandstone lies below and 

olive-gray clay lies above the disconformity. 

Several other subaerial erosional events 

apparently took place in the Miocene, Pliocene, 

and Pleistocene, as indicated by repeateQ zones 

of intensely oxidized microfossils and sediments 

in the B-2 well and in the AMCOR 6009 arli 6010 

cores. In these sections, the detailed 

biostratigraphic zonation required to estimate 

the time spans represented is not yet 

completed. None of these disconformities has 

the reflective strength on seismic profiles that 

characterizes the older disconformities. 

63 

SEDIMENT ACCUMULATION RATES 

Sediment-accumulation-rate curves for the 

COST Nos. B-2, B-3, and GE-l wells (Poag and 

Hall, 1979) are displayed in figure 29. During 

the Middle(?) and Late Jurassic, accum•.tlation 

rates in the B-2 and B-3 areas were uniformly 

high (2.1 to 3.1 in./1,000 yrs; 5.4 to 7.8 

cm/1,000 yrs) and nearly identical. This is 

manifest also on figure 25, which shc~s the 

uniform thickness of these strata across the 

outer part of the Baltimore Canyon trough. 

Throughout the Early Cretaceous and into the 

Cenomanian, the accumulation rates remained 

nearly identical at the B-2 and B-3 sites, but 

were reduced (0.8 to 1.5 in./1,000 yrs; 2.1 to 

3.8 cm/1,000 yrs, with the exception of a 

Valanginian pulse of 2.8 to 3.2 in./1,010 yrs; 

1.0 to 8.1 cm/1,000 yrs). Rates were 

considerably higher coevally at the GE-l site in 

the Southeast Georgia Embayment (2.5 irl./1,000 

yrs; 6. 4 em/ 1, 000 yrs). A pulse of increased 

accumulation affected the B-2 and B-3 sites in 

the Turonian (2. 2 to 4.1 in. I 1, 000 yrs; 5. 5 to 

10.5 cm/1,000 yrs), but was not effective at GEl (reduced slightly to 2.2 in./1,000 yrs; 5.5 

cm/1,000 yrs). Coniacian and Santonian rates 

remained high (1.8 to 2.6 in./1,000 yrs; 4.6 to 

6.5 cm/1,000 yrs) at B-3, but at B-2 Santonian 

rates were reduced to 0.8 in./1,000 y~s (1.9 

cm/1,000 yrs). All three COST well sites 

experienced reduced rates during the CEmpanian 

and early Maestrichtian (0.5 to 0.6 ir./1,000 

yrs; 1.3 to 1.4 cm/1,000 yrs). 

During the Cenozoic, the rat~s are 

noticeably less uniform between the Baltimore 

Canyon trough and the Southeast Georgia 

Embayment. Early Eocene rates are similar (1.1 

to 1.5 in./1,000 yrs; 2.8 to 3.9 cm/l,OCO yrs), 

but in the middle and late Eocene, th~ rates 

dramatically increase at the GE-l site (2.5 

in./1,000 yrs; 6.3 cm/1,000 yrs) and decrease in 
RELATIVE CHANGE OF 

GLOBAL SEA LEVEL 

PALEOBATHYMETRY SEDIMENT ACCUMULATION RATE TIME (cm/IOOOyn) 

(M.Y.) 

.-·-·) 

' II: 

: 

4 6 10 12 

·-·-·-·-·-·24.8"=+-· 

. 

: 

............ : 

r········· __ J . 

,~" . 

. -:::-·1 

...._ PRESENT 

SEA LEVEL Kb i ~-................... . -· : '"'·-·-·+·i-·-·-. · 1 I 

'-:.:::::::::J l . I 

·-....... 

B-2 

Figure 29.--Comparison of global sea-level changes (Vail and others, 1977) with paleobathymetry 

and sediment accumulation rates at the COST Nos. GE-l, B-2, and B-3 well sites. The 

sediment accumulation rate for the middle Miocene at site B-2 lies off the scale of 

the chart at 9.8 in./1,000 yrs (24.8 cm/1,000 yrs). 

B-2 and B-3 (0.4 to 0.9 in./1,000 yrs; 1.0 to 

2.4 cm/1,000 yrs). The Oligocene rates are 

similar at B-3 and GE-l (0.9 to 1.0 in./1,000 

yrs; 2.2 to 2.5 cm/1,000 yrs), but about half as 

great at B-2 (0.5 in./1,000 yrs; 1.3 cm/1,000 

yrs). In the middle Miocene, a significant 

increase occurs at each site (2.0 in./1,000 yrs; 

5.0 cm/1,000 yrs) at GE-l; 3.2 in./1,000 yrs 

(8.0 cm/1,000 yrs) at B-3), but the increase at 

B-2 is by far the most dramatic at any site (9.8 

in./1,000 yrs; 24.8 cm/1,000 yrs). Pliocene 

rates are poorly documented, but appear to range 

from 1.0 to 1.2 in./1,000 yrs ( 2.5 to 3.1 

cm/1,000 yrs). At GE-l, Quaternary rates remain 

about the same as Pliocene rates (1.0 in./1,000 

yrs; 2.5 cm/1,000 yrs), but at B-2 and B-3 

another pulse of terrestrial sedimentation 

raised rates to 4.3 in. and 3.9 in./1,000 yrs 

(11 em and 10 cm/1,000 yrs), respectively. 

SEA-LEVEL FLUCTUATIONS AND DEPOSITIONAL CYCLES 

A comparison of global sea-level cycles 

(Vail and others, 1977) and the depositional 

(paleobathymetric) and sediment-accumulation 

cycles observed in the COST Nos. B-2, B-3, and 

GE-l wells are shown in figure 29. In general, 

the correspondence of deep and shallow 

bathymetry with high and low sea levels, 

respectively, is remarkably close; and the 

supercycles of Vail and others (1971) can be 

recognized. The Middle(?) to Lete Jurassic 

supercycle (J) began with nonmarine to "inner 

shelf" deposition and culminated across the 

Tithonian-Berriasian boundary with "middle 

shelf" deposition. 

Deposition of supercycle KE' began in 

nonmarine to "inner shelf" water depths in the 

Valanginian and reached "middle shelf" depths in 

64 
the lower to middle part of the Albian. A 

Cenomanian hiatus marks the base of supercycle 

Kb in GE-l, but not in the B-2 and B-3 wells. 

In both latter wells, however, the lower 

Cenomanian rocks are of shallower water origin 

than the upper Cenomanian rocks. Subsequent to 

the "outer shelf" deposition of the late 

Cenomanian, a minor hiatus was followed by 

"inner to middle shelf" deposits of the lower 

Turonian in each well. The major hiatus at the 

top of the Turonian effectively divides 

supercycle Kb into two subcycles, as the 

generalized curve of Vail and others (1977) 

seems to suggest. The upper subcycle peaked in 

the Santonian, Campanian, and early 

Maestrichtian with "outer shelf to upper slope" 

deposition, and terminated, after a late 

Maestrichtan regression, in a major hiatus. 

Deposits of supercycle Ta are only 

fragmentarily represented in each well, and its 

cyclical nature cannot be distinguished. 

Super cycle Tb, however, is well represented at 

all three sites. The Eocene part of this 

supercycle began with "middle shelf to upper 

slope" deposition in the lower Eocene, peaked as 

"outer shelf to lower slope" deposits in the 

middle Eocene, and terminated after a late 

Eocene regression in a major hiatus in which the 

upper Eocene and lower Oligocene (upper half of 

supercycle Tb) were eroded (although part of the 

lower Oligocene remains at GE-l). This late 

Eocene-early Oligocene hiatus is evidently the 

65 

result of the dramatic sea-level drop dat is 

postulated for the middle Oligocene (Va:f 1 and 

others, 1977). 

Supercycle Tc began in the Baltimore Canyon 

trough with late Oligocene deposition in "outer 

shelf" and "lower slope" depths. A slight 

shallowing noted at B-2 and B-3 was follol,,ed by 

an early Miocene hiatus which also affected the 

GE-l site. At GE-l, and at other drill sites in 

the Southeast Georgia Embayment, this ero~ional 

event removed upper Oligocene as well as M~ocene 

rocks. The middle of supercycle Tc (middle 

Miocene) is represented by sustained terre~trial 

outbuilding at the COST Nos. B-2 and B-3 well 

sites. Deltaic progradation in the outer 

Baltimore Canyon trough was rapid enough to keep 

pace with the rise in sea level and pr')duced 

shallow-water deposits as far seaward as ~12 mi 

(-20 km) downdip from the B-2 site (fig. 26). 

The lack of biostratigraphic definition h"'mpers 

clear recognition of the remaining supercycles, 

but the top of Tc seems to be represented at B-2 

and B-3 by shoaling to "middle and inner shelf" 

depths. Tc is not represented at GE-l, having 

been removed by early Pliocene erosion which 

began supercycle Td. 

Supercycle Td is represented by middle 

Pliocene "upper slope" deposits at GE-l, and by 

undifferentiated Pliocene of "outer shelf" and 

presumably "upper-slope" depths at B-2 and B-3 

respectively. The details of Quaternary 

depositional cycles have yet to be worked out. 

CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY, 

PALEOENVIRONMENTS, AND 

POST-JURASSIC CONTINENTAL MARGIN DEVELOPMENT 

Page c. Valentine 

The COST No. B-3 well penetrated 13,134 ft 

(4,003 m) of sedimentary rock, and samples 

ranging in age from middle Miocene to Late 

Jurassic were collected over a 12,000-ft (3,658-

m) interval. Hiatuses in the stratigraphic 

record are apparent in the lower Miocene, middle 

and lower Oligocene, Paleocene, and upper 

Maestrichtian. Both marine and nonmarine 

environments existed during Late Jurassic-Early 

Cretaceous time, whereas marine environments 

prevailed during the Late Cretaceous and 

Cenozoic. In Cretaceous time, sediments 

accumulated rapidly at the COST No. B-3 well 

site, chiefly at shelf depths on a slowly 

subsiding, aggrading margin. However, Cenozoic 

sediments were deposited at slope depths on a 

relatively rapidly subsiding margin that became 

progradational in post-Oligocene time. 

Calcareous nannofossils are present throughout 

most of the section, but barren intervals exist 

within Jurassic, Lower Cretaceous, and 

Cenomanian strata. Selected nannofossil species 

that are of biostratigraphic significance in the 

Lower Cretaceous section are illustrated in 

plates 1 and 2. Preliminary studies of 

calcareous nannofossils found in the COST No. B2 well drilled on the outer Continental Shelf 30 

mi (50 km) to the north (Smith and others, 1976; 

Valentine, 1977) have been re-evaluated in light 

of the findings of the present study and the 

Tertiary and Upper Cretaceous stratigraphy of 

the two well sites are similar in many respects. 

Calcareous nannofossil biostratigraphy of 

the COST No. B-3 well (fig. 30) is based 

primarily on the study of rotary drill cuttings 

collected over 10- to 30-ft (3- to 9-m) 

intervals. With few exceptions, cuttings were 

analyzed at intervals of 100 ft (30 m) or less, 

beginning with the first sample which was 

collected at 3, 810 ft (1, 161 m) and ending at 

15,800 ft (4,816 m) (fig. 30) A complete 

sequence of samples was studied from 4,560 to 

5,370 ft (1,390 to 1,637 m). Smear slides were 

made from individual rock fragments representing 

each of the lithologic units present in a single 

cuttings sample. The oldest nannofossil 

assemblage identified in a sample was used to 

determine the age of the strata at that level. 

67 

Species listed as representative of a 

stratigraphic interval do not necessarily occur 

in every sample studied from that interval. In 

all, 572 samples from 243 levels in the well 

were studied. Sample depth are relative to the 

Kelly Bushing and total depth of the well was 

15,820 ft (4,822 m). The reports on the COST 

No. B-3 well by International Biostratigraphers, 

Inc. (1979) and Amato and Simonis (1979) were 

consulted; selected information, as cited, has 

been incorporated into the present study. 

BIOSTRATIGRAPHY 

Miocene (3,810-4,710 ft; 1,161-1,436 m) 

Calcareous and diatomaceous mudstone 

chiefly of middle Miocene age and at least 900 

ft (274m) thick is present from 3,81C to 4,710 

ft (1,161 to 1,436 m). Diatoms are abundant and 

well preserved in most of the sample~ studied 

from this interval, whereas the abu'1dance of 

calcareous nannofossils varies from few to 

common and preservation is moderate to good. , 

Many of the calcareous nannofossil S"":'ecies in 

this sequence are long-ranging; the~, include 

Coccolithus eopetagicus, c. pelagicus, 

Cyclicapgotithus floPidanus, Cyclococ~otithina 

macintyPei, DiscoasteP bPo~ePi, D. chaltengePi, 

D. defZandPei, D. VaPiabilis, Discolit1:·ina spp., 

Helicosphaem caPtePi, and ReticuZofenestm 

pseudoumbilica. 

The Miocene interval comprisesmiddle 

Miocene strata from 3,810 to 4,620 ft (1,161 to 

1,408 m), and slightly older beds of late early 

to early middle Miocene age that exten~ down to 

4,710 ft (1,436 m). DiscoasteP exitis is 

consistently present in the middle Miocene 

cuttings down to 4,620 ft (1,408 m), and 

DiscoasteP bottii ranges from 4,320 to 4,650 ft 

(1,317 to 1,417 m). The highest occurrence of 

Helicosphaem intePmedia is at 4,500 ft (1,372 

m) and of CoPonocyctus nitescens, at 4, 560 ft 

(1,390 m). 

Strata of late early to early middle 

Miocene age are recognized by th~ highest 

occurrence of 8phenolithus hetePomory::hus in a 

sample from 4,620 to 4,650 ft (1,408 to 1,417 
DEPTH 

(BELOW KB) 

ETERS FEET 

AGE 

3810 1 

MIDDLE 

MIOCENE 

SANTONIAN 

7040 1-----

CONIACIAN 

7440 1 

CENOMANIAN 

8900 1-----

ALBIAN 

PALEO- SELECTED NANNOFO~'rLSPECIE 

ENVIRONMENT IN THE UPPER CRETACEOUS 

AND TERTIARY OF C1ST B-3 

u.. u.. w w u.. _J _J a.. a.. 

w _J w w g g w ~ ~ z ~ (/) (/) (/) 

~ <( a:: w a:: a:: a:: :::E __. w w w 

~ w 0 t- a.. 

~ z 0 3 a.. ~ 2 ::::> 

I 

I 

I 

~ Highest occurrence 

__j Lowest occurrence 

(1) IBI sidewall core 

4560 ~ c. nitescens 

4620 1 _j D. exilis I H. arrpliaperta 

s. heteromorphus 

I 4710 1

1 H. eup~ratis, H. recta { ( 1) T. car~natus f 

4775 ~ s. ciperoensis (1) 

48001__j T. carinatus 

4830 ~ D. bisectus, D. scrippsae 

49201_j s. ciperoensis 

4950'I D. saipanensis, I. recurvus 

N. dubius 

4965 ~ D. barbadiensis (1) 

51751---, C. grar:dis, C. solitus 1( 1) 1 H. sem~nulum ~ 

5525 ~ D. lodoensis (1) 

5675'1 D. kuepperi (1) 

5830'~ T. orthostylu3 

5840 1

1 L. nascens 

6080 1 ----------, B. parca 

6120'1 T. gothicus 

6200 1 -----~ E. eximius 

6310 1 ____J T. aculeus, T. gothicus 

6470~-----~M. furcatus(1 

64801____J B. parca 

6600'~ c. cuneatus, L. floralis 

L. grillii 

7440' ~c. achylosum 

79401 ____J M. furcatus 

8210 1 _____ ---.J E. eximius 

84601 -----~ P. albianus 8520 11 c. chiastia 

8900 ~ B. africana 

Figure 30.--Calcareous nannofossil biostratigraphy and paleoenvironments of the COST N1. B-3 

2,686 ft (819 m). CSG, casing point, IBI, International Biostratigrapher;, Inc. In 

on findings of this study but incorporate some biostratigraphic information from 

68 
DEPTH 

(BELO KB) 

METERS FEET 

AGE 

CENOMANIAN 

8900'----

ALBIAN 

- 9840'-- -- - -

-

= 

APTIAN- -

- BARREMIAN -

- 11018'-------

- HAUTERIVIAN-

- VALANGINIAN -

12700'---- --

BERRIASIAN 

13450'-----

LATE 

JURASSIC 

PALEO- SELECTED NANNOFOSSIL 

ENVIRONMENT SPECIES IN THE LC'VER 

t 

t 

! 

t 

I 

? 

SLLSL CRETACEOUS OF COST B-3 

8900' ~B. africana 

9385 1 -----, F. biforaminis ( 1) 

10130' ~ N. colomii 

10930' ~c. margerelii, M. obtusus 

11018'~ B. colligatus (2) 

ll 045' ~ c. cuvillieri (2) 

12080'~ c. mexicana 

12700' ~ P. senaria 

Brachiolithus? Sp. 

13450'~ P. beckmannii 

~ Highest occurrence 

(1) 181 sidewall core 

(2) 181 conventional core 

well. Depths are relative to the Kelly Bushing (KB), 42 ft (13m) above sea level. Water depth 

sample column, blacked-in areas indicate a complete sequence of samples studied. Ages are based 

International Biostratigraphers, Inc. (1979). 

69 
m). This species is a biostratigraphic marker 

restricted to the Sphenolithus hetePomoPphus and 

Heli~osphaePa ampliapePta zones of Bukry (1973, 

1975). Sphenolithus hetePomoPphus and 

Heli~osphaem ampliapePtur>a are both found in 

cuttings from 4,620 ft (1,408 m) down to 4, 740 

ft (1, 445 m). However, a sidewall core from 

4, 710 ft (1,436 m) contains an upper Oligocene 

calcareous nannofossil assemblage (International 

Biostratigraphers, Inc., 1979), and therefore 

the maximum extent of upper lower to lower 

middle Miocene beds is from 4,620 to 4, 710 ft 

(1,408 to 1,436 m). An unconformity 

representing most of the lower Miocene exists 

between this sequence and the underlying upper 

Oligocene. 

At the COST No. B-2 well site, an 

equivalent interval of diatomaceous middle 

Miocene strata is present from about 2,800 to 

3,520 ft (853 to 1,073 m). These beds are 

barren of calcareous nannofossils and have been 

dated through the study of foraminifers (Smith 

and others, 1976; Poag, 1977). 

Oligocene (4,710-4,950 ft; 1,436-1,509 m) 

The unconformable upper Oligocene-middle 

Miocene contact is at 4,710 ft (1,436 m), 

coincident with the highest occurrences of 

Heli~osphaer>a euphr>ati, H. Pe~ta, and 

TPiquetPor>habdulus caPinatus reported from a 

sidewall core by International 

Biostratigraphers, Inc. (1979). The Oligocene 

is a 240-ft (73-m) sequence of calcareous and 

diatomaceous mudstone, less calcareous but 

otherwise lithologically similar to the 

overlying Miocene strata. Calcareous 

nannofossils are common to abundant, and 

preservation is moderate to good. Species that 

range throughout this interval include 

Co~~olithus eopelagicus, c. pelagicus, 

CoPonocyolus nitescens, CyclioaPgolithus 

abiseotus, c. flor>idanus, Disooaster> deflandPei, 

Disoolithina spp., Helioosphaer>a euphmtis, H. 

intePmedia, H. obliqua, H. Pecta, 

Reticulofenestr>a cf. R. scissuf'Us of Bramlette 

and Wilcoxon (1967), Sphenolithus dissimilis, 

and ZygPhablithus bijugatus. 

Upper Oligocene strata of the lower part of 

the TPiquetPor>habdulus caf'inatus zone (Bukry, 

1973, 1975) are present from 4, 710 to 4,830 ft 

(1,436-1,472 m) and are recognized by the 

presence of TPiquetr>or>habdulus car>inatus in 

association with the species listed above. 

Somewhat older beds of late middle to early 

late Oligocene age that represent the 

Sphenolithus cipePoensis zone (Bukry, 1973, 

1975) are present from 4,830 to 4,950 ft (1,472 

to 1,509 m) and contain the diagnostic species 

Diotyococoites bisectus, D. scPippsae, and 

Sphenolithus oiper>oensis, whereas 

TPiquetPoPhabdulus caPinatu.s is not present. An 

abrupt change to an upper Eocene calcareous 

nannofossil assemblage at the base of this 

interval (4,950 ft; 1,509 m) indicates that 

middle and lower Oligocene strata are absent. 

In the COST No. B-2 well, a similar 

Oligocene sequence is present. Upper Oligocene 

beds representing the Tf'iquetPoPhabdulus 

oaPinatus zone (Bukry, 1973, 1975) extend from 

3,580 to 3,730 ft (1,091 to 1,137 m); and strata 

of late middle to early late Oligocene age 

(Sphenolithus cipePoensis zone of Bukry, 1973, 

1975) are present from 3,790 to 4,0~0 ft (1,155 

to 1,234 m). 

Eocene (4,950-6,040 ft; 1,509-1,841 m) 

Beneath the Oligocene calcarecus mudstone, 

a sequence of Eocene argillaceot•s limestone 

1,090 ft (323 m) thick is present c".own to 6,040 

ft (1 ,841 m), where it unconformably overlies 

lower Maestrichtian calcareous shal~. 

Upper Eocene limestone extends for 200 ft 

(61 m) from 4,950 to 5,150 ft (1,509 to 1,570 

m). These beds contain abundant, w~ll-preserved 

calcareous nannofossils. The top of the upper 

Eocene is placed at the highest occurrences, at 

4, 950 ft (1, 509 m), of Blac1<ites spp., 

Cyclococcolithina foPmosa, DisooasteP nodifeP, 

D. saipanensis, Helicosphaem c?mpaota, H. 

Peticulata, Isthmolithus PecuPVus, 

Retioulofenestm caUida of Bybell (1975), R. 

umbilioa, Sphenolithus pr>edistentus, 

TPansVePsopontis obliquipons, and T. zigzag; and 

the highest occurrence of anoth~r important 

species, DisooasteP bar>badiensis, is in a 

sidewall core from somewhat deeper in the well 

at 4, 965 ft (1, 513 m) (International 

Biostratigraphers, Inc., 1979). Two of these 

species (Disooaster> bar>badiensis, D. 

saipanens1:s) are not known to range above the 

Eocene, whereas the highest occurr-;mces of the 

other species are coincidental only because 

lower and middle Oligocene strata are missing 

from the COST No. B-3 well section. Other 

species that are typical of the uprer Eocene in 

this well are Cyclicapgolithus f"lor>idanus, 

Dictyococcites bisectus, D. scPippsae, 

Discolithina spp., He"licosphaem euphr>atis, H. 

~ilcoxonii, and Zygr>hab"lithus bijugatus. 

Chiasmo"lithus oamaf'Uensis and Reticu"lofenestr>a 

Peticulata are present and are restricted to the 

upper Eocene of the COST No. B-3 well. Most of 

the sequence that is assigned a late Eocene age 

is equivalent to the DiscoasteP baPbadiensis 

zone of Bukry (1973, 1975). 

As is the case with the Miocene and 

Oligocene parts of this section, the Eocene 

interval in the COST No. B-3 well j_s comparable 

to the Eocene of the COST No. B-2 well. Upper 

Eocene beds of the DiscoasteP baPbc.diensis zone 

(Bukry, 1973, 1975) are present in the B-2 well 

from 4,080 to 4,320 ft (1,244 to 1,317 m). 

The top of the middle Eocene is placed at 

5,150 ft (1,570 m), halfway between two sidewall 

cores studied by International 

Biostratigraphers, Inc. (1979). The highest 

occurrences of Chiasmolithus gr>andis, C. 

solitus, and He"lioosphaem seminu"lum were 

observed in a sidewall core from 5,175 ft (1,577 

70 
m) (International Biostratigraphers Inc., 1979) 

and in the cuttings samples from 105 ft (32 m) 

lower, at 5,280 ft (1,609 m). Calcareous 

nannofossils are common to abundant, but their 

preservation is noticeably poorer than it is in 

the overlying strata. Middle Eocene limestone 

is about 680 ft (207 m) thick and is present 

from 5,150 to about 5,830 ft (1,570 to 1,777 

m). Calcareous nannofossil species that are 

typical of this interval include CepekieZZa 

Zumina, Chiasmotithus gigas (rare), C. g~ndis, 

c. sotitus, Coccotithus eopetagicus, C. 

petagicus, CycticaPgotithus fZoPidanus, 

Cyctococcotithina foPmosa, C. gammation, 

DiscoasteP baPbadiensis, D. saipanensis, Heticosphae~a Zophota, H. intePmedia, H. 

seminutum, Neococcotithes dubius, Sphenotithus 

~dians, TPansVePsopontis obtiquipons, and 

ZygPhabtithus bijugatus. In addition, the 

highest occurrences of Campytosphaepa deta, 

DiscoasteP diastypus, D. Zodoensis, and 

DiscoastePoides kueppePi are in the lower part 

of the middle Eocene in the COST No. B-3 well. 

In the COST No. B-2 well, middle Eocene beds of 

the same age are present from 4,380 to 4,800 ft 

(1,335 to 1,463 m). 

Lower Eocene limestone extends from about 

5,850 to 6,040 ft (1,783 to 1,841 m). 

International Biostratigraphers, Inc. (1979) 

placed the top of the lower Eocene at the 

highest occurrence of DiscoasteP Zodoensis in a 

sidewall core from 5,525 ft (1,684 m). nte 

boundary between the lower and middle parts of 

the Eocene Series falls within the DiscoasteP 

Zodoensis zone of Bukry (1973), as shown by 

Perch-Nielsen (1977, table 3). In the present 

study, recognition of the top of the lower 

Eocene is based on the ranges of eight species 

rather than on the highest occurrence of a 

single species. In cuttings samples from the 

COST No. B-3 well, the following pattern of 

species ranges, which overlap at about 5,850 ft 

(1,783 m), are recognized. Several species are 

present that elsewhere are most commonly 

observed in the middle Eocene but that range 

down into the uppermost lower Eocene. ntese 

species and their lowest occurrences in the B-3 

well are ChiasmoZithus gPandis (5,890-5,900 ft; 

1,795-1,798 m), DiscoasteP miPus (5,870-5,880 

ft; 1,789-1,792 m), Heticosphae~ Zophota 

(5,890-5,900 ft; 1,795-1,798 m), and H. 

seminutum ( 5, 890-5,900 ft; 1, 795-1,798 m) • 

DiscoasteP subtodoensis, usually restricted to 

middle Eocene strata, is present from 5,520 to 

5,880 ft (1,682 to 1,792 m) in the B-3 well. 

Two species are present that are generally found 

in the lower Eocene but that range up into the 

lowermost middle Eocene; these species and their 

highest occurrences in the B-3 well are 

Lophodotithus nascens (5,840-5,850 ft; 1,780-

1,783 m) and TPib~chiatus OPthostytus (5,830-

5,840 ft; 1,777-1,780 m). The ranges of 

DiscoasteP Zodoensis and DiscoastePoides 

kueppePi are known to overlap the lower Eocenemiddle Eocene boundary; in the B-3 well they are 

71 

present from their highest occurrences in 

sidewall cores at 5,525 ft (1,684 m) anc" 5,675 

ft (1,730 m), respectively (International 

Biostratigraphers, Inc., 1979), down to 6,040 ft 

(1841 m). Coccotithus magnicPassus is a species 

that, when first described (Bukry, 1971), was 

known only from the DiscoasteP Zodoensis zone; 

it is present from 5, 810 to 6, 040 ft (1, 771 to 

1, 841 m) in the COST No. B-3 well. Other 

species that are represented in the lower Eocene 

in the B-3 well are Campytosphae~ deta, 

Coccotithus eopetagicus, C. jugatus of PratoDecima and others (1975), C. peZagicus, C. 

petPinus, CycZococcotithina foPmosa, DisaoasteP 

baPbadiensis, D. diastypus, DiscoasteP~ides 

megastypus, sphenotithus ~dians, 

TPansvePsopontis fimbPiatus, ZygPhabtithus 

hijugatus, and, in the upper part, 

Cyctoccotithina gamnation. The lower Eocene 

strata are eqivalent to the DiscoasteP Zodoensis 

and TPib~chiatus OPthostyZus zones of Bukry 

(1973), and are coeval with the lower Eocene 

beds that extend from 4,850 to 5,020 ft (1,478 

to 1,530 m) in the COST No. B-2 well. 

The Eocene limestone beds overlie lcwer to 

middle Maestrichtian calcareous shale. The 

missing Paleocene and lowermost Eocene strata 

represent a major unconformity in the 

stratigraphic section of the COST No. B-3 well 

that is also present in the COST NO. B-2 well 

and may be widespread on the outer Contj nental 

Margin in this region. 

Maestrichtian (6,040-6,200 ft; 1,841-1,8~0 m) 

The Upper Cretaceous-Tertiary boundary is 

placed at 6,040 ft (1,841 m), where light-gray, 

lower Eocene limestone overlies medium- to darkgray calcareous shale containing lower to middle 

Maestrichtian calcareous nannofossil assemblages. The Upper Cretaceous section is 

approximately 2,860 ft (872 m) thick, extending 

down to the 8, 900-ft (2, 713-m) level. It is 

composed chiefly of gray calcareous mudstone and 

shale and includes a section rich in glauc~nitic 

sandstone, several intervals of quartz 

sandstone, and minor beds of limeston~ and 

dolomite. Calcareous nannofossil assemblages 

are diverse and contain species that are common 

to abundant and generally moderately to well 

preserved. Upper Cretaceous nannofloras c~ntain 

many long-ranging species that are present 

throughout most of the interval: AhmueZZePeZZa octo~diata, B~~dosphaena biget~ii, 

Chiastozygus pticatus, CoPoZZithion signum, 

CPetaPhabdus conicus, c. coPonadventia, c. 

cPenuZatus, CPibPosphaePeZZa ehPenb~Pgii, 

Cytind~Zithus asymmetPicus, c. coPo~atus, 

EiffeZZithus eximius, E. tuPPiseiffeZi, 

GaPtnemgo costatum, G. segmentatum, KarrrptnePius 

magnificus, K. punctatus, LithastPinus fZomtis, 

L. gPiZZii, Lithmphidites ca~ioZ€nsis, 

LucianoPhabdus cayeu~~, Manivitetta 

pemmatoidea, Micuta stauPopho~, PaPhabdoZithus 

angustus, P. embePgePi, P. spZeYLdens, 
PPediscosphae~ cPetacea, Stephanolithion 

laffittei, Tet~Zithus obscuPUs, T. ovalis, 

Vagalapilla matalosa, WatznauePia baPnesae, 

Zygodicus acanthus, z. diplog~mmus, and z. 

fibulifoPmis. The occurrences of stratigraphic 

marker species are discussed later. 

Strata of early to middle Maestrichtian age 

are present in a 160-ft (49-m) interval from 

6,040 to 6,200 ft (1,841 to 1,890 m) in the COST 

B-3 well and contain BPoinsonia paPca, 

TetPalithus aculeus, T. gothicus, and T. 

tPifidus. At the COST No. B-2 well site, 

Maestrichtian sandstone is present from 5,020 to 

5,400 ft (1,530 to 1,646 m). 

Campanian (6,200-6,470 ft; 1,890-1,972 m) 

Campanian calcareous shale at least 270 ft 

(82 m) thick is present from 6,200 to 6,470 ft 

(1,890 to 1,972 m). The top of the sequence is 

placed at the highest occurrence of Eiffellithus 

eximius observed in the present study, and the 

base at the highest occurrence of MaPthastePites 

fuPcatus in a sidewall core reported by 

International Biostratigraphers, Inc. (1979). 

The lowest occurrence of BPoinsonia paPca, a 

species restricted to strata of Campanian and 

early Maestrichtian age, is from 6,470 to 6,480 

ft (1, 972 to 1, 975 m) in a cuttings sample of 

this study. In the COST No. B-2 well, 

calcareous shale of Campanian age is present 

from 5,400 to about 5,750 ft (1,646 to 1,753 

m) • 

Rock chips of Campanian age dominate 

cuttings samples in the COST No. B-3 well down 

to about the 9,400-ft (2,865-m) level. The 

caliper log run from 12,689 ft (3,868 m) up to 

5,764 ft (1,757 m) shows that the drill hole 

from 6,200 to 6,700 ft (1,890 to 2,042 m) is 

wider than 18 in., the maximum value recorded on 

the log, although it was drilled with a 12 1/4 

-in. bit. The extensive down-hole contamination 

makes it difficult to delineate the underlying 

Santonian and Coniacian part of the section. 

Santonian-Coniacian (6,470-7,440 ft; 

1,972-2,268 m) 

The top of the 970-ft (296-m) SantonianConiacian interval is placed at the highest 

occurrence of MaPthastePites fupcatus in a 

sidewall core from 6,470 ft (1,972 m) 

(International Biostratigraphers, Inc., 1979). 

Glauconite grains are present as a rare or minor 

fraction of the cuttings from about 6, 270 ft 

(1,911 m) downward, but at 6,480 ft (1,975 m) 

they become common and remain an important 

component of the cuttings samples down to about 

7,040 ft (2,146 m). The strata from 6,480 to 

7,040 ft (1,975 to 2,146 m) appear to be 

composed of friable glauconitic silt and sand. 

Although samples from this part of the well are 

contaminated with Campanian cuttings, an 

examination of the relatively few intact 

glauconitic rock chips has shown that they 

72 

contain calcareous nannofossils of SantonianConiacian age. Chiastozygus cunqatus and 

LithastPinus flom.Zis, two stratig-raphically 

important species restricted to Santonian and 

older strata, are not present above 6,600 ft 

(2,012 m) in the COST No. B-3 well. 

The Santonian and Coniacian cannot be 

differentiated using calcareous narrnofossils, 

but the glauconitic beds that are present from 

6,480 to 7,040 ft (1,975 to 2,146 m) are 

provisionally assigned to the Santonian. From 

7, 040 ft to 7, 440 ft (2, 146 to 2, 268 m), where 

the highest sample of Turonian age was observed, 

the rock chips are chiefly Campanian cavings, 

and the rare glauconitic chips of SantonianConiacian age are probably also cavings from 

above. In contrast, the unconsolidated sediment 

in the cuttings samples from this interval 

(7,040-7,440 ft; 2,146-268 m) is silty, fine 

sand containing mica, lignite, large pyrite 

crystals, dolomite, and fragments of mollusks, 

including oyster shells and prisms of InocePamus 

valves. These poorly lithified strata are 

assigned to the Coniacian and are indicative of 

an inner shelf depositional environment in which 

calcareous nannofossils are poorly represented. In the COST No. B-2 well, Santonian and 

Coniacian sandstone and calcareous shale 

containing Inocemmus shell fragments are 

present from about 5, 750 to 7,100 ft (1, 753 to 

2,164 m). 

Turonian (7,440-8,230 ft; 2,268-2,508 m) 

Samples from 7,440 ft (2,268 m) and below 

contain the shallow-water elements described 

above, in addition to gray calcar~~us shale 

cuttings of Turonian age. The Turonian shale is 

recognized by the co-occurrence of CoPollithion 

achylosum and EiffeUithus eximius. The two 

uppermost Turonian samples from 7,440 to 7,450 

ft (2,268 to 2,271 m) and from 7,530 to 7,540 ft 

(2,295 to 2,298 m) are separated l:r several 

hundred feet of Campanian cavings from a 

sequence of Turonian samples that extends 430 ft 

(131 m), from 7,770 to 8,200 ft (2,36~ to 2,499 

m). If the top of the Turonian is indeed near 

7, 440 ft (2, 268 m), the stage is about 760 ft 

(232 m) thick. 

These results differ somewhat from the 

findings of International Biostratigraphers, 

Inc. (1979) based on a study of calcareous 

nannofossils from sidewall cores. In that 

report, the top of the Turonian was placed at 

8,140 ft (2,481m), although CoPollithion 

achylosum, a species restricted to Turonian and 

older rocks, was consistently present from 7,230 

ft (2,204 m) down to 8,306 ft (2,532 m). Also, 

EiffeHithus eximius was not observed in 

sidewall cores below 7,044 ft (2,147 m) or to 

occur with CoPollithion achylosum (International 

Biostratigraphers, Inc., 1979). However, in the 

present study, CoPollithion achylosum and 

Eiffellithus ex~m~us are present together in 

individual rock chips from 7,440 tc 8,210 ft 
(2,268 to 2,502 m), and previous investigations 

have shown that the ranges of these two species 

overlap in the Turonian (Thierstein, 1976; 

Valentine, 19 79). The base of the Turonian is 

placed at 8,230 ft (2,508 m) at a marked change 

in lithology from gray calcareous shale to 

coarse quartz sand that predominates down to 

8,700 ft (2,652 m). Turonian gray calcareous 

shale is present in the COST No. B-2 well from 

7,100 to about 7,600 ft (2,164 to 2,316 m). 

Cenomanian (8,230-8,900 ft; 2,508-2,713 m) 

The Cenomanian is represented by a 670-ft 

(204-m) interval of quartz sandstone containing 

a minor amount of calcareous shale. The abrupt 

lithologic change at 8,230 ft (2,508 m) from 

calcareous shale to friable, coarse quartz 

sandstone may represent an unconformity between 

strata of Turonian and Cenomanian age. Samples 

from the upper 200 ft (61 m) of this part of the 

section are barren of calcareous nannofossils or 

contain Campanian and Turonian cavings. 

International Biostratigraphers, Inc. (1979, 

fig. 1) placed the top of the Cenomanian at the 

highest occurrence of Rotalipom cushm::r.ni in a 

sidewall core from 8,040 ft (2,451 m), slightly 

above the top of the sandstone. According to 

their interpretation, the lithologic change from 

shale to sandstone is in the upper part of the 

Cenomanian interval. Shale cuttings from the 

lower part of the Cenomanian, as delineated in 

the present study, exhibit the highest 

occurrences of C~cietlipsis chiastia, Pa~habdolithua aspe~, and Podo~habdus atbianus, 

whereas Eiffellithua eximiua, a species 

restricted to Turonian and younger beds, is not 

present. 

Albian (8,900-9,840 ft; 2,713-2,999 m) 

The top of the Albian is recognized at 

8,900 ft (2, 713 m), the highest occurrence of 

Bma~dosphaem af~icana ( p 1. 2, fig. 12) , a 

species that ranges from the upper Aptian 

through the Albian (Gartner, 1977). Albian 

strata are chiefly calcareous shales and barren 

calcareous sandstones. The nannoflora found in 

the shale cuttings is relatively diverse and 

includes Bma~dosphaem af~icana, Co~oUithion 

signum, C~uciellipsis chiastia, Plabetlites 

bifomminis (pl. 1. figs. 5, 6), Pa~habdotithus 

aspe~, P~ediscosphaem c~etacea, and 

nannoconids. The lowest occurrence of 

P~ediscosphaem c~etacea is at 9,840 ft (2,999 

m) and approximates the base of the Albian 

Stage. 

Aptian-Barremian (9,840-11,018 ft; 

2,999-3,358 m) 

In contrast to the overlying Albian strata, 

the Aptian-Barremian interval is a very poorly 

fossiliferous sequence of calcareous sandstone 

and shale about 1,178 ft (359 m) thick. Most 

samples examined are almost barren except for 

some shale cuttings containing nannofloras of 

Aptian-Albian aspect that include such species 

as Bmarudosphaem af~icana, Chiastozygus 

plicatus, Co~otlithion achylosum, C~eta~habdus 

co~onadventis, Cruciettipsis chiastia, 

Plabetlites bifo~aminis, Lithast~inus [':omlis, Mic~antholithus obtusus (pl. 2, fig. 10), 

Pa~habdolithus angustus, and P. infinitus (pl. 

1, fig. 1). A conventional core and a series of 

seven sidewall cores from 9, 935 to 10,730 ft 

(3,028 to 3,270 m) are barren of calcareous 

nannofossils (International Biostratigraphers, 

Inc., 1979). Consequently, the Barremian and 

Aptian cannot be differentiated, and the upper 

and lower boundaries of the Barremian-Aptian 

part of the well are provisional. 

Hauterivian-Valanginian (11,018-12,700 ft; 

3,358-3,871 m) 

Hauterivian and Valanginian strata also 

cannot be differentiated using calcareous 

nannofossils. They are calcareous sandstone and 

shale, somewhat more fossiliferous than the 

overlying Aptian and Barremian beds. The 

abundance of calcareous nannofossils varies from 

few to common, and preservation is poor to 

moderate. The top of the approximately 1,682-ft 

(513-m) Hauterivian-Valanginian seque~ce is 

drawn at the highest occurrence of Bipodo~habdus 

colZigatus (pl. 1, figs. 8, 9), observ?.d in a 

conventional core sample from 11,018 ft (3,358 

m); and calcareous nannofossil assemblages of 

the same age were identified in three other 

conventional core samples from 11,029 ft (3,362 

m), 11,044 ft (3,366 m), and 11,045 ft (3,367 m) 

(International Biostratigraphers, Inc., 1979). 

The following species are typically present 

in calcareous shale from this interval: 

Bipodo~habdus cottigatus, Diazomat1-alithus 

tehmanii, Conuaphaem mexicana (pl. 2, fig. 3), 

c~uciettipsis chiastia, c. cuvittie~ (pl. 1, 

figs. 11, 12), Cyclagelosphaem deflandrqi (pl. 

1, fig. 10), c. m::r.~ge~etii (pl. 1, fig. 7), 

Micmntholithua obtusus, Nannoconus coZo~i (pl. 

1, figs. 2, 3), Pa~habdolithus aspe~, P. 

embe~ge~, Watznaue~ ba~esae, W. ~ommunis 

(pl. 1, fig. 4), Zygodiscus diplogmmm·.•s, and 

unidentified nannoconids. In the lower part of 

the Hauterivian-Valanginian, a small species of 

Mic~anthoZithua (pl. 2, fig. 13) was obs~rved in 

only one sample (12,590-12,600 ft; 3,8:'7-3,840 

m) in the COST No. B-3 well; it r~sembles 

MicmnthoZithus sp. reported from the Bossier 

Shale of Late Jurassic-Early Cretaceous age in 

Louisiana and Arkansas by Cooper and Shaffer 

(1976, pl. 1, fig. 4). A distinctive species, 

Bidiacua? canthus (pl. 2, fig. 4), is pr~sent in 

three samples from a short stratigraphic interval (12,470-12,740 ft; 3,801-3,883 m) that extends from the lower part of the HauterivianValanginian into the upper part of the 

Berriasian. 

An interval of varied lithology is present 

from about 12,400 to 12,700 ft (3,780 to 3,871 

73 
m). As described by Lachance (1979), this part 

of the section is composed of calcareous 

sandstone and gray shale and shallow-water 

oolitic and intraclastic limestone containing 

algal structures. The shale cuttings from this 

interval yielded calcareous nannofossil 

assemblages of Hauterivian-Valanginian age, 

whereas the limestone and calcareous sandstone 

cuttings are barren. The isolated occurrence of 

the Berriasian marker Polyaostella senaPia in a 

sidewall core from 12,394 ft (3,778 m) 

(International Biostratigraphers, Inc., 1979) 

casts some doubt on the Hauterivian-Valanginian 

age of the lower part of this interval, although 

its presence may have resulted from reworking or 

contamination, as will be discussed later. At 

present, the beds from 12,400 to 12,700 ft 

(3, 780 to 3,871 m) are included in the lower 

part of the Hauterivian-Valanginian sequence, 

and are interpreted as representing deposition 

in a shallow-water marine environment. 

Berriasian (12,700-13,450 ft; 3,871-4,100 m) 

On the basis of the study of calcareous 

nannofossils in individual rock chips from 

cuttings samples, the top of the Berriasian 

interval should be placed at 12,700 ft (3,871 

m), the level of highest occurrence of 

Polyaostella senaPia (pl. 2, figs. 7-9) and 

somewhat below both the lowest occurrence of 

BipodoPhabdus aolligatus (12,640 ft; 3,853 m) 

and the point at which the 9 5/8-in. casing was 

set (12,659 ft; 3,858 m). Polyaostella senaPia 

is restricted to strata of Berriasian age 

(Thierstein, 1973), and BipodoPhabdus colligatus 

does not range below the Valanginian 

(Thierstein, 1976). International 

Biostratigraphers, Inc. (1979), in a study of 

sidewall cores, reported the highest occurrence 

of Polyaostella senaPia from 12,394 ft (3,778 m) 

and the lowest occurrence of BipodoPhabdus 

aolligatus from 12,510 ft (3,813 m). The same 

study showed, however, that Polyaostella senaPia 

is consistently present in a series of four 

sidewall cores from 12,734 to 12,903 ft (3,881 

to 3,933 m), and the authors speculated that its 

isolated presence 340 ft (104 m) above this 

group of samples could be the result of 

reworking. 

Between the casing point (12,659 ft; 3,858 

m) and 13,400 ft (4,084 m), the cuttings are 

almost free of caved younger material and are 

composed of dark-gray calcareous shale of 

Berriasian age. Calcareous nannofossils are 

rare to few in number, and preservation is poor 

to moderate. Assemblages found in the shale 

comprise Bpachiolithus? sp. (pl. 2, figs. 1, 2), 

CPuciellipsis chiastia~ CyclagelosphaePa 

deflandPei~ c. maPgePelii~ Polycostella senaPia~ 

WatznauePia bamesae ~ W. communis, and 

nannoconids. The species questionably assigned 

to Bpaahiolithus (Noel, 1959, pl. 3, figs, 25-

27) is a common constituent of the Berriasian 

assemblages; it is restricted to strata of that 

age in the COST No. B-3 well and may prove to be 

74 

of biostratigraphic importance. Nearly barren 

cuttings of uncertain age are present in samples 

from 13,420 ft (4, 090 m) and deeper, but the 

Berriasian dark-gray shale, presumably cavings, 

remains a prominent constituent of sa~ples down 

to about 14,000 ft (4,267 m). 

Upper Jurassic (13,450-15,800 ft; 

4,100-4,816 m) 

The Jurassic-Lower Cretaceous bC'11ndary in 

the COST No. B-3 well is provisionally placed at 

13,450 ft (4, 100 m) the highest occurrence of 

Polycostella beckmannii (pl. 2, fig. 6). This 

species is reported to range from the Tithonian 

(=Portlandian) into the lower Berriasian, where 

it is associated with P. senaPia (T';ierstein, 

1973, 1976; Gartner, 1977), and the two species 

are found together in individual chips of 

calcareous shale from 13,450 to 13,940 ft (4,100 

to 4,249 m). However, undated cuttings of 

calcareous sandstone and shale that are almost 

barren are also present from about 13,420 ft 

(4,090 m); they become more prevalent with 

increasing depth and may be of Juressic age. 

The shale cuttings containing both Polycostella 

beakmannii and P. senaPia may therefore be 

cavings from lowermost Berriasia~ strata 

somewhat higher in the well. 

In the study by International 

Biostratigraphers, Inc. (1979) of calcareous 

nannofossils from the COST No. B-3 well sidewall 

cores, P. beakmannii and P. senaPia were not 

observed in the same samples, and the JurassicLower Cretaceous boundary was placed in the 

interval between the lowest occurrence of P. 

senaPia at 12,903 ft (3, 933 m) and the highest 

occurrence of P. beckmannii at 13,758 ft (4,193 

m). 

There is no consensus on the placement of 

the Jurassic-Lower Cretaceous boundary in the 

COST No. B-3 well. International 

Biostratigraphers, Inc. (1979) concluded that 

foraminifers are not diagnostic (although Poag, 

this volume, disagrees), and the biostratigraphic significance of the range of a 

palynomorph species (Ctenododinum panneum) is 

disputed by palynologists who have worked on 

offshore wells of the Atlantic margin. 

According to Bujak and Williams (1977), C. 

panneum is restricted to the Jurassic. On this 

basis Steinkraus (1979) and J. F. Bebout 

(written communication, 1979) have drawn the 

Jurassic-Lower Cretaceous boundary at 12,400 ft 

(3,780 m), and Poag (this volume) ar:rees with 

this interpretation on the basis of his study of 

benthic foraminifers. 

Steinkraus (1979) pointed out that in many 

of the Atlantic offshore wells the highest 

occurrences of C. panneum and the n9.nnofossil 

Hexalithus noelae often coincide, and he also 

stated that H. noelae is not known to range 

above the Upper Jurassic. Cooper ard Shaffer 

(1976) studied the stratigraphic distribution of 

H. noelae in the Bossier Shale of the Arkansas 
and Louisiana subsurface and discussed the 

variant forms of the species as described by 

Noel (1957, 1959). [The species was described 

as Hexalithus hexalithus by Noel (1957) from the 

Portlandian of Algeria and renamed by Loeblich 

and Tappan (1966)]. Cooper and Shaffer (1976) 

concluded that the extinction level of this 

species approximates the top of the Jurassic; 

although they did not present an occurrence 

chart, they imply that H. noelae in the Bossier 

Shale is associated with, among others, 

Broaaroudosphaem bigelowii, Microantholithus sp., 

Nannoconus colomii, PolycosteZZa beckmannii, P. 

senaroia, and Watznaueroia broittanica. According 

to Thierstein (1973, 1976), PolycosteZZa senaroia 

and Nannoconus coZomii are restricted to 

Berriasian and younger rocks, and PoZycosteZZa 

beckmannii is found only in the Tithonian and 

Berriasian. Thus, the assemblage described by 

Cooper and Shaffer (1976) has a Berriasian 

aspect, and their evidence for the restriction 

of HexaZithus noelae to Tithonian and older 

strata is not compelling. Hexalithus noelae, as 

illustrated by Noel (1957, pl. 5, figs. 39, 40; 

1959, pl. 3, fig. 24), was not observed in the 

present study. But a circular form with 

prominent sutures (pl. 2, fig. 5), very similar 

to H. noelae of Cooper and Shaffer (1976, pl. 1 

figs, 6, 7), is present in one sample (12,020-

12,030 ft; 3,664-3,667 m) from the HauterivianValanginian part of the section in the COST No. 

B-3 well. 

International Biostratigraphers, Inc. 

(1979) interpreted the palynomorph Ctenododinum 

panneum as ranging from the Jurassic into the 

Lower Cretaceous where it is found with 

Pseudoceroatium peZZiferoum, a Cretaceous 

dinoflagellate species. Therefore, at the COST 

No. B-3 well site, International 

Biostratigraphers, Inc. (1979) placed the 

Jurassic-Lower Cretaceous boundary in the 

interval from 12,900 to 13,650 ft (3,932 to 

4,161 m), the interval in which the ranges of 

the two species overlap. 

To the north, at the COST No. B-2 well 

site, the Jurassic-Lower Cretaceous boundary is 

at about 12,800 ft (3,901 m). In a revised 

interpretation of the biostratigraphy of the 

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

Fairchild (International Biostratigraphers, 

Inc., written communication, 1977) provisionally 

placed the Jurassic-Lower Cretaceous boundary 

between 12,800 and 13,000 ft (3,901 and 3,962 m) 

on the basis of the following observations: 

PoZycosteZZa senaroia, the Berriasian nannofossil 

marker, is present in sidewall cores from 12,120 

ft (3,694 m) and 12,365 ft (3,769 m); and the 

Cretaceous dinoflagellate Pseudoceroatium 

peZZiferoum, mentioned above, is present in 

samples from 12,301, 12,561, and 12,791 ft 

(3,749, 3,829, and 3,899 m). Ctenododinum 

panneum, a Jurassic-Cretaceous palynomorph, is 

present in the same interval and in sidewall 

cores up to 12,037 ft (3,669 m). In contrast, 

the Jurassic dinoflagellate MeiouroogonyauZax 

75 

staffinensis is present in sidewall cores and 

conventional cores from 12,791 ft (3,899 m) down 

to 13,448 ft (4,099 m). The Jurassic-I.ower 

Cretaceous contact is, therefore, near the 

12, 800-ft ( 3, 901-m) level in the COST No. B-2 

well, about 650 ft (198 m) higher than it is in 

the COST No. B-3 well. On the other 1 'ind, 

Adinolfi and Jacobson f1979) and Poag (1979, and 

this volume) placed the top of the Jurassic 

between 11,800 and 12,000 ft (3,597 and 3,658 m) 

in the COST No. B-2 well on the basis of benthic 

foraminifers and palynomorphs. 

In the COST No. B-3 well, calcareous 

nannofossils are rare and poorly preserved 1~low 

about 14,000 ft (4,267 m); only long-rar~ing 

species such as Cyclagelosphaeroa rrn.rogeroelii. and 

Watznaueroia baronesae are present. Calcareous 

nannofossil assemblages of Jurassic age wer~ not 

recognized in this analysis or by Internat:tonal 

Biostratigraphers, Inc. (1979), but the pre~~nce 

of palynomorphs of Kimmeridgian age in the part 

of the well below 13,220 ft (4,029 m) has been 

reported by Steinkraus (1979) and J. w. Bebout 

(written communication, 1979), and below about 

13,700 ft (4, 176 m) by Internat:tonal 

Biostratigraphers, Inc. (1979). Poag (this 

volume) recognized benthic foraminifers of ~arly 

and late Kimmeridgian age and possibly of 

Callovian age. 

PALEOENVIRONMENTS 

The paleoenvironmental interpretatior of 

the COST No. B-3 well section presented here 

(fig. 30) is based on the abundance, diver~ity, 

and generic composition of calcareous n~nnofossil and ostracode assemblages; on the 

presence and abundance of diatoms; and on the 

lithologic characteristics of the sedimertary 

strata. Paleoenvironmental reconstructions 

based on studies of benthic and planktic foraminifers and of sporomorphs and dinoflagellates 

(International Biostratigraphers, Inc. 1979; 

Bebout and Lachance, 1979; Poag, this volt'me), 

and the abundance of terrestrial palynomC'rphs 

(Bebout and Lachance, 1979, fig. 5) have also 

been considered. Depositional environments are 

characterized in terms of shelf and slope deryths 

as they generally exist today. However, 

references to slope depths do not necess~rily 

mean that deposition took place on an ancient 

slope, for it may well have occurred on a ~helf 

or platform that lay at a depth greater than 

modern shelves (greater than about 650 ft or 200 

m). The trends illustrated in figure 30 are 

real, but because the results of this analysis 

are general in nature, the degree of their 

development is not yet known precisely. 

Upper Jurassic strata are present in the 

COST No. B-3 well from total depth of the well 

at 15,820 ft (4,822 m) to 13,450 ft (4,101 m) 

and comprise a 2,370-ft (722-m) sequence of 

interbedded oolitic limestone, sandstone, carkgray shale, and lignite. Below about 14,0(0 ft 

(4,267 m), these rocks are almost barren of 

calcareous nannofossils; foraminiferal f~unas 
are also very sparse below 14,500 ft (4,420 

m). The lithology of the sedimentary beds and 

the nature of the fossil assemblages indicate 

that this part of the Upper Jurassic was 

probably deposited in fluctuating nonmarine and 

shallow-marine environments. 

From 14,000 ft (4,267 m) to the JurassicLower Cretaceous boundary- at 13,450 ft (4, 100 

m), the strata were deposited in a somewhat 

deeper-marine middle-shelf environment. The 

calcareous nannofossil assemblages are not 

diverse, but the few species are consistently 

present throughout the interval. 

A marine middle-shelf environment continued 

to prevail throughout Berriasian time, and 

calcareous nannofossil assemblages became more 

diverse. The Berriasian rocks (13,450-12,700 

ft; 4,100-3,871 m) are primarily marine shale 

and sandstone with a minor amount of limestone. 

At the base of the Hauterivian-Valanginian, 

a 300-ft (91-m) interval from 12,700 to 12,400 

ft (3,871 to 3,780 m) is chiefly shale and 

sandstone interbedded with oolitic limestone 

indicative of a shallow-marine origin. 

Terrestrial palynomorphs increase in abundance 

in these strata and subsequently decline in 

number with the return of middle-shelf, silty 

and sandy shale that extends up to about 12,000 

ft (3,658 m) and contains fairly diverse 

calcareous nannofossil assemblages. 

The upper part of the HauterivianValanginian, from 12,000 ft to about 11,000 ft 

(3,658 to 3,353 m), is sparsely fossiliferous 

with regard to both calcareous nannofossils and 

foraminifers. The silty shale, sandstone, and 

minor coal beds of this interval were deposited 

in an inner shelf environment. 

At the Hauterivian-Barremian boundary 

(11,018 ft; 3,358 m), a very thin sequence of 

shale (11,046-10,930 ft; 3,367-3,331 m) marks 

the return of middle-shelf conditions. 

Calcareous nannofossils and foraminifers are 

present, and terrestrial palynomorphs decline in 

abundance. 

The overlying Aptian-Barremian strata 

(10,930-9,840 ft; 3,331-2,999 m) are almost 

barren of calcareous nannofossils, and foraminifers are mostly absent from about 10,700 to 

10,400 ft (3,261 to 3,170 m), except near the 

top of the interval. The sandstone, shale, and 

minor lignite present in the sequence were deposited in a nonmarine to inner shelf 

environment. 

The Albian beds (9,840-8,900 ft; 2,999-

2,713 m) are chiefly silty shale with several 

interbedded sandstone layers; they reflect a 

modest increase in water depth to inner shelf 

conditions. Calcareous nannofossils and 

foraminifers are present in some samples, 

although others are barren. Terrestrial 

palynomorphs are abundant, perhaps indicating an 

increase in terrigenous sedimentation. 

Water depth continued to increase, and the 

silty shale that is present in the lower part of 

76 

the Cenomanian (8,900-8,460 ft; 2, 713-2,579 m) 

reflects a middle-shelf environme:nt. Diverse 

calcareous nannofossil assemblageE' are present 

in this interval, and terrestrial palynomorphs 

increase markedly in abundance. T~~ upper part 

of the Cenomanian (8,460-8,230 ft; 2,579-2,509 

m), however, is composed of coarse quartz sand 

and is barren of calcareous nannofossils. Also, 

terrestrial palynomorphs increase in abundance 

and indicate that the sand was de .... osited in an 

inner shelf environment. 

A disconformity exists in the COST No. B-3 

well section at 8,230 ft (2,509 m); marks a 

hiatus between Cenomanian shallow-to·'iter deposits 

and middle to upper Turonian calcareous shale of 

outer shelf origin that extends u'J to 7,440 ft 

(2,268 m). Calcareous nannofossil~ are diverse, 

and terrestrial palynomorphs decline in 

abundance in this interval. 

At the top of the Turonian, another disconformity coincides with a shallowing of the 

marine environment to inner shelf conditions 

during the Coniacian. Marine s<:~.nd and silt 

containing lignite, mica, large pyrite crystals, 

and shell fragments of shallow-marine mollusks 

were deposited from 7,440 ft to about 7,040 ft 

(2,268 to 2,146 m). Calcareous nar~ofossils are 

poorly represented in this part of the 

section. However, they increase in abundance 

and diversity in the overlying Santonian 

glauconitic sandstone of middle-sl:~lf to outer 

shelf origin that is present from 7,040 to 6,470 

ft (2, 146-1,972 m). Terrestrial palynomorphs 

reach a maximum abundance in the Coniacian 

interval and decline in numbers with deepening 

marine conditions in in the Santonian. 

The overlying Campanian and Maestrichtian 

calcareous shale that is present from 6,470 to 

6, 040 ft (1, 972 to 1, 841 m) is rich in calcareous nannofossils and foraminifers, but poor 

in terrestrial palynomorphs. A marine environment characterized by outer shelf to upper slope 

depths developed at the COST No. B-3 well site 

during the Campanian and ~·.~estrichtian. 

Ostracode assemblages indicativ?. of these 

conditions are also present; they are sparse, 

exhibit low diversity, and are corrposed chiefly 

of the genera AZataaythePe, BaiPdia, 

BythoaythePemoPpha, CythePella, KPithe, and 

PhaaoPhabdotus. 

A major disconformity is present at 6, 040 

ft (1 ,841 m) between lower Maestrichtian 

calcareous siltstone and lower Eocene limestone. The thick limestone sequence from 6,040 

to 4,950 ft (1,841 to 1,509 m) encompasses 

lower, middle, and upper Eocene strata that 

contain very rich calcareous nannofossil and 

foraminifer assemblages. Terrestrial palynomorphs are absent, and ostracod-a assemblages 

throughout the Eocene are dominate1 by BaiPdia, 

CythePeZZa, KPithe, EahinoaythePeis, HenPyho~elZa, PhaaoPhabdotus, and 

PtePygoaythePeia. All evidenc~ points to 

deposition of the Eocene limestone at upper 

slope water depths, somewhat dee.,er and more 
isolated from 

postulated for 

strata. 

terrigenous sediments than 

Campanian and Maestrichtian 

The upper Eocene limestone is overlain 

disconformably by middle and upper Oligocene 

calcareous and diatomaceous mudstone that 

extends from 4,950 to 4, 710 ft (1,509 to 1,436 

m). Calcareous nannofossils are abundant and 

diverse, and ostracode assemblages in these beds 

are similar in generic composition to those 

found in the underlying Eocene. The Oligocene 

rocks were deposited ~t upper slope depths 

similar to those of the Eocene paleoL 

environment. The sedimentary regime had altered 

significantly, however, as indicated by the 

presence of an increased volume of terrigenous 

particles in the Oligocene rocks. 

The upper Oligocene is succeeded disconformably by middle Miocene diatomaceous siltstone and mudstone. These beds are less 

calcareous than those of the Oligocene and also 

contain a less diverse calcareous nannofossil 

flora. Even though terrestrial palynomorphs are 

abundant, their presence here reflects the 

continuation of a sedimentary regime characterized by an influx of terrigenous sediments 

rather than a decrease in water depth. The 

middle Miocene at the COST No. B-3 well site was 

a time of rapid terrigenous sedimentation in an 

upper slope environment of deposition. 

Pliocene and Quaternary silt and clay are 

probably present at the COST No. B-3 well site 

in the upper part of the unsampled interval 

between the sea floor (2, 728 ft; 831 m) and 

3,810 ft (1,161 m). At least 1,000 ft (305 m) 

of Pleistocene silt and clay of outer shelf to 

upper slope origin have been cored at AMCOR site 

6021 on the uppermost Continental Slope, about 4 

mi (6 km) northwest of the COST No. B-3 well; 

and sand and silt of Miocene, Pliocene, and 

Pleistocene age have been cored at AMCOR site 

6010 on the Continental Shelf, about 21 mi (33 

km) to the northwest (Hathaway and others, 

1979). 

In summary, the stratigraphic section 

drilled at the COST No. B-3 site comprises 

chiefly marine clastic and carbonate strata 

ranging in age from Late Jurassic to 

Quaternary. In Late Jurassic time, nonmarine to 

inner shelf environments prevailed, whereas the 

Early Cretaceous is best characterized as a time 

during which marine environments fluctuated 

between inner shelf and middle-shelf depths. 

Middle-shelf conditions existed during 

deposition of the following stratigraphic 

intervals: the uppermost Jurassic and the 

Berriasiat?-, the lower part of the HauterivianValanginian, the Hauterivian-Valanginian 

boundary, and the lower part of the 

Cenomanian. Major unconformities are not 

discernible in the Upper Jurassic and Lower 

Cretaceous, although the poorly fossiliferous 

nature of the shallow-marine and marginally 

nonmarine intervals may mask hiatuses in this 

section. 

The middle-shelf environment of depoe-ition 

in the lower part of the Cenomanian prece.-ted a 

major regression, also in the Cenomanian, when 

quartz sand was deposited in an innermost shelf 

environment. These beds are separ-ated by an 

unconformity from the overlying transgressive 

calcareous shale of middle to late Turonian age 

that was deposited at outer shelf denths. 

Subsequently, another regression occurred, and 

Coniacian sand and silt indicative of an inner 

shelf facies accumulated disconformably 0'1 the 

Turonian shale. 

During Coniacian through Maestrichtian 

time, a major transgression developed, an.-1. the 

marine environment gradually deepened from inner 

shelf depths in the Coniacian to a middlenshelf 

and outer shelf environment during deposit:J',on of 

the Santonian glauconitic sand. Fir filly, 

Campanian and Maestrichtian calcareous shale 

accumulated at outer shelf and upper slope 

depths. 

The Maestrichtian and lower Eocene strata 

are separated by a disconformity that may nark a 

marine regression, although no shallow-~water 

deposits are present in this part of the COST 

No. B-3 well section. The limestone of the 

lower Eocene is indicative of deposition at 

upper slope depths that are also recorded in the 

overlying beds of Eocene, Oligocene, and M:C.ocene 

age that were sampled during the drilling of the 

well. 

Two other disconformities are prese':lt in 

the Tertiary part of the section, for both the 

lower Oligocene and lower Miocene are missing. 

There is no indication, however, of significant 

shallowing of the marine environment associated 

with these two hiatuses in the stratigraphic 

record. 

As the flux of both terrigenous sediments 

and nutrients increased in post-Eocene time, the 

Eocene limestone gave way to calcareou~ and 

diatomaceous mudstone and siltstone that 

accumulated rapidly during the Oligocen,~ and 

especially in Miocene time. The increa"e in 

nutrients, as demonstrated by the presence of 

rich diatom floras, was directly related to the 

increase in terrigenous sedimentation and (or) 

upwelling on the Continental Slope. Given the 

results of the limited shallow coring thet has 

taken place on the upper slope of this region 

and the present water depth (2,686 ft; 819 m) at 

the ·drill site, it is evident that an upper 

slope environment has existed at the COST No. B3 well site throughout Neogene and Quaternary 

time. 

POST-JURASSIC MARGIN DEVELOPMENT 

The post-Jurassic developmental history of 

the Continental Margin at the COST No. B-3 well 

site can be elucidated by comparing the average 

sediment-accumulation rates, the average 

subsidence rates, and the depositional depths of 

the stratigraphic intervals represented in the 

section. 

77 
Sediment accumulation rates for three major 

intervals in the COST No. B-3 well section are 

1.56 in./1,000 yrs (3.96 cm/1,000 yrs) for the 

Lower Cretaceous, 0.98 in./1,000 yrs (2.49 

cm/1,000 yrs) for the Upper Cretaceous, and 0.61 

in./1,000 yrs (1.55 cm/1,000 yrs) for the 

Cenozoic. Hiatuses contribute significantly to 

the low accumulation rate calculated for the 

Cenozoic part of the section. Separate 

determinations for the Eocene, upper Oligocene, 

and middle Miocene intervals give accumulation 

rates of 0.87 in./1,000 yrs (2.21 cm/1,000 yrs), 

0.44 in./1,000 yrs (1.11 cm/1,000 yrs), and 2.57 

in./1,000 yrs (6.52 cm/1,000 yrs), respectively. 

Subsidence rates for the lower surfaces of 

these stratigraphic intervals are more difficult 

to determine. Factors that must be considered 

include the thickness of the strata, compaction, 

the depths at which the lower and upper surfaces 

of the unit were deposited, and the positions of 

sea level (relative to present sea level) at the 

beginning and end of deposition of the unit. 

(For method of calculation, see van Hinte, 1978; 

Poag and Hall, 1979.) The effect of compaction 

was disregarded in the present study. 

Paleodepths remained at about 300 ft (100 m) for 

the lower and upper surfaces of the Lower 

Cretaceous, but increased from 300 to 1,000 ft 

(100 to 300 m) for the Upper Cretaceous and from 

1,000 ft (300 m) to 2,686 ft (819 m; present-day 

water depth) for the Cenozoic. Subsidence rates 

are based on these estimates, as well as on the 

sea-level projections of Vail and others (1977, 

fig. 6c) and, alternatively, on the assumption 

that sea level was always at its present 

level. Even though this conservative approach 

has generated a spread of values for the 

subsidence rate of each stratigraphic interval, 

the general depositional history has not been 

obscured. The calculations using sea levels 

postulated by Vail and others (1977) resulted in 

the lowest values for Lower and Upper Cretaceous 

subsidence rates and the highest values for the 

Cenozoic subsidence rate. 

The Lower Cretaceous subsidence rates vary 

from 1.11 to 1.56 in./1,000 yrs (2.96 to 3.96 

cm/1,000 yrs), generally lower than the 

accumulation rate of 1.56 in./1,000 yrs (3.96 

cm/1,000 yrs). The Upper Cretaceous subsidence 

rates range from 0.99 to 1.20 in./1,000 yrs 

(2.51 to 3.06 cm/1,000 yrs), somewhat higher 

than the accumulation rate of 0.98 in./1,000 yrs 

(2.49 cm/1,000 yrs). In contrast, subsidence 

rates calculated for the Cenozoic interval range 

from 0.93 to 1.12 in./1,000 yrs (2.35 to 2.85 

cm/1,000 yrs), consistently much higher than the 

overall sediment accumulation rate of 0.61 

in./1,000 yrs (1.55 cm/1,000 yrs). 

The post-Jurassic geologic evolution of the 

Continental Margin in this region is summarized 

as follows: Lower Cretaceous sediments 

accumulated rapidly, and water depth fluctuated 

within a narrow range characteristic of shelf 

conditions (although, according to Vail and 

others (1977, fig. 6c), sea level rose 

78 

throughout the Early Cretaceous). During Late 

Cretaceous time, the subsidence rate was 

somewhat higher than the sediment-accumulation 

rate, and sediments were deposited at shelf and, 

later, uppermost slope depths coincident with a 

continued rise and stabilization of sea level 

(Vail and others, 1977, fig. 6c). In general, 

during the Cretaceous, rapid accumulation of 

sediments, relatively rapid sub~idence, and 

rising sea level all contributed to the 

aggradation or upbuilding of the middle Atlantic 

Continental Margin off New Jersey. If a 

Continental Slope existed, it was s~award of the 

COST No. B-3 well site. 

In Cenozoic time, the rate of subsidence 

and (or) sediment removal was, on the average, 

much greater than the rate of sediment 

accumulation. As mentioned above, the 

calculated sediment accumulation rate may be 

somewhat low due to hiatuses in the record. The 

Continental Margin near the COST No. B-3 well 

site subsided to water depths characteristic of 

the present slope, but seismic profiles of the 

margin in this region (Grow and others, 1979, 

figs. 4, 5) show that an obvious shelf-slope 

break did not exist landward of the COST No. B-3 

well until post-Oligocene time. During the 

Eocene and Oligocene, the broadly subsiding 

Continental Margin was built upward by a 

substantial thickness of predominantly carbonate 

sediments that included an increased amount of 

terrigenous debris in the Oligoc~ne. Slope 

water depths have been maintained by subsidence 

at the COST No. B-3 well to the present time, 

even though Vail and others (1977, fig. 6c) have 

indicated that sea level, while fluctuating 

above and below its present level, has fallen 

throughout the Cenozoic. It is not yet clear 

whether the Paleocene, lower and middle 

Oligocene, and lower Miocene hiatu<1es are the 

result of subaerial or submarine erosion or 

nondeposition. No evidence exists of shallowwater sediments bounding these hiatuses in the 

COST No. B-3 well section. 

Subsidence continued throug;out postOligocene time, but the margin became 

progradational; it evolved primarily by 

outbuilding or progradation through the rapid 

deposition of a large volume of terrigenous 

sediment. Prograding beds of probable Miocene 

age are clearly visible in seismic profiles of 

the shelf in this area (Schlee and others, 1976, 

figs. 7, 8, 9; Amato and Simonis, 1979, pl. 5; 

Schlee and Grow, this volume). The edge of the 

present Continental Shelf was therefore defined 

by the prograding post-Oligocene sedimentary 

wedge, and the Continental Rise dev~loped as an 

onlapping sequence of deep-water sediments that 

were derived from erosion of both the land 

surface and the newly developed Continental 

Slope. 

TAXONOMIC NOTES 

The following remarks refer to several of 

the calcareous nannofossil species illustrated 

in plate 2. 
Broa~hiolithus? sp. (pl. 2, figs. 1, 2) is 

restricted to the Berriasian interval in the 

COST No. B-3 well and is present from 12,700 to 

13,240 ft (3,871 to 4,036 m). This apparently 

undescribed species is hexagonal or septagonal, 

having an open center and six or seven short, 

rectangular, lateral spines that radiate from 

the corners of the rim. The outside diameter of 

the rim is 5.0-6.5 J-Lm, and including the spines, 

6.0-7.5 flm• The width of both the rim wall and 

spines is 0.7-1.0 J-Lm• Broa~hiolithus? species 

somewhat resembles three species of the genus 

BPa~hiolithus Loeblich and Tappan that have been 

observed in the Portlandian, Berriasian, and 

Valanginian of Algeria (Noel, 1959, pl. 3, figs. 

25-27). However, BPa~hiolithus? sp. of the COST 

No. B-3 well is smaller, the central area is 

open, and the species does not appear to be 

formed by a single crystal of calcite as is 

Broa~hiolithus. It is not possible to determine 

using the light microscope whether the rim of 

BPa~hiolithus? sp. is segmented. BPa~hiolithus? 

sp. also resembles Stephanolithion sp. of Bukry 

and Bramlette (1969, pl. 4B), a species observed 

in a core-catcher sample from the bottom of DSDP 

Hole SA that was dated as Tithonian 

(=Portlandian) by those authors. Broa~hiolithus? 

sp. lacks the central spine and radiating bars 

of the central area that are characteristic of 

the described species of Stephanolithion from 

the Jurassic and Lower Cretaceous (Rood and 

Barnard, 1972). 

Bidis~us? ~anthus Wilcoxon (pl. 2, fig. 4) 

is present in the Hauterivian-Valanginian and 

Berriasian intervals in the COST No. B-3 well 

from 12,470 to 12,740 ft (3,801 to 3,883 m). 

This species was observed in the Valanginian, 

Hauterivian, and Barremian strata at DSDP sites 

99 and 105 (Wilcoxon, 1972, pl. 6, figs. 5, 

6). The specimen illustrated here (pl. 2, fig. 

4) most resembles the specimen on Wilcoxon's 

plate 6, figure 6, but specimens similiar to the 

specimen on Wilcoxon's plate 6, figure 5 were 

also observed and are included in R.? ~anthus. 

Hexalithus aff. H. noelae Loeblich and 

Tappan (pl. 2, fig. 5) was observed in a single 

sample in the COST No. B-3 well (12,020-12,030 

ft, Hauterivian-Valanginian). This species is 

similar to H. noelae of Cooper and Shaffer 

(1976, pl. 1, figs. 6, 7) from the Bossier Shale 

of Louisiana, but it differs from H. noelae 

Loeblich and Tappan in possessing a circular 

rather than the festooned or hexagonal outline 

exhibited by the forms originally illustrated by 

Noel (1957, pl. 5, figs. 39, 40; 1959, pl. 3, 

79 

fig. 24). The extinction level of H. noelae of 

Cooper and Shaffer (1976) may not be a reliable 

datum for recognizing the Jurassic-Cretaceous 

(Tithonian-Berriasian) boundary. 

Poly~ostella senaPia Thierstein (pl. 2, 

figs. 7-9), a Berriasian marker, is present from 

12,700 to 14,120 ft (3,871 to 4,304 m) in the 

COST No. B-3 well, but occurrences belollr about 

13,450 ft ( 4, 100 m) are probably the reE'•1lt of 

caving. (See preceding text.) P. senaPia, 

illustrated on plate 2, figure 7, displayE' seven 

ridges, and it is comparable to sp~cimens 

illustrated by Thierstein (1971, pl. 1, fig. 6) 

and by Cooper and Shaffer (1976, pl. 1, fig. 3), 

both of which show a proximal view of a sevenpointed specimen. P. senaPia specimens 

illustrated here in plate 2, figures 8, 9 each 

display six points and six well-developed 

ridges, and they are comparable to distal views 

of the holotype (Thierstein, 1971, pl. 1, figs. 

2-5). The six-pointed specimens found in the 

COST No. B-3 well are also similar to 

?Hexalithus noelae? of Cooper and Shaffer (1976, 

pl. 1, fig. 2) from the Bossier Shale of 

Louisiana. And a comparison of the scanning 

electron micrographs of Polyso~tella senaPia 

(Thierstein, 1971, pl. 1, fig. 2) and 

?Hexalithus noelae? of Cooper and Shaffer (1976, 

pl. 1, fig. 2) indicates that their similarity 

might be somewhat obscured by overgro~~th on 

Thierstein's specimen. If these observations 

are correct, the specimen of ?H. noelae? 

illustrated by Cooper and Shaffer (1976, pl. 1, 

fig 2) is Poly~ostella senaPia. 

The pentaliths of tJPaaPudosphaePa df. B. 

afPi~ana Stradner (pl. 2, fig. 11) are composed 

of elements that are relatively wide with a 

blunt distal termination, whereas in B. afPi~ana 

Stradner (pl. 2, fig. 12), the elements are 

relatively narrower and pointed. (Compare with 

Noel, 1959, pl. 9, fig. 47, from the AU ian of 

France.) B. aff. B. afPi~ana was observed in 

two Turonian samples (both are cavings collected 

from the Cenomanian interval: 8,260-8,270 ft 

and 8,330-8340 ft; 2,518-2,521 and 2,539-2,542 

m) in the COST No. B-3 well; and it is present 

higher in the section than B. afPi~ana, which is 

present from 8,900 to 9,830 ft (2,712 tc 2,996 

m) • 

Mi~roanthotithus sp. (pl. 2, fig. 13) is 

present in only one sample (HauterivianValanginian; 12,590-12,600 ft; 3,837-3,840 m). 

This species resembles M. sp. of Coop~r and 

Shaffer (1976, pl. 1, fig. 4) from the Bossier 

Shale of Louisiana. 
Light 

Figure 1. 

2-3. 

PLATE 1 

micrographs (x2890) of selected nannofossils from the COST No. B-3 well. 

PaPhabdolithus infinitus (Worsley) Thierstein, Sample 9,950-9,960 

ft; R86N16A; crossed nicols, gray filter. 

Nannoconus colomii (de Lapparent) Kamptner. 

2. Sample 12,390-12,400 ft; R87N25A; crossed nicols, blue 

filter. 

3. Same specimen; R87N26A; partly polarized light, blue 

filter. 

4. WatznauePia communis Reinhardt, Sample 12,590-12,600 ft; R87N34A; 

crossed nicols, gray filter. 

S-6. Flabellites bifo~minis Thierstein. 

5. Sample 10,240-10,250 ft; R87N18A; crossed nicols, 

gray filte~. 

6. Same specimen, rotated 45°; R87N19A; crossed nicols, 

gray filter. 

1. CyclagelosphaePa maPgePelii Noel, Sample 13,130-13,140 ft; 

R87N31A; crossed nicols. 

8-9. BipodoPhabdus colligatus (Black) Thierstein. 

8. Sample 12,390-12,400 ft; R87N23A; crossed 

nicols, gray filter. 

9. Same specimen, rotated 28°; R87N24A; crossed 

nicols, gray filter. 

10. Cyclagelosphae~ deflandPei (Manivit) Roth, Sample 13,130-13,140 

ft; R87N28A; crossed nicols, gray filter. 

11-12. CPuciellipsis cuviZZiePi (Manivit) Thierstein. 

11. Sample 12,020-12,030 ft; R87N21A; crossed nicols, 

gray filter. 

12. Same specimen, rotated 45°; R87N22A, crossed nicols, 

gray filter. 
2 3 

4 5 6 

7 8 9 

10 11 12 
PLATE 2 

Light micrographs (x2890) of selected nannofossils from the COST No. B-3 well. 

For species marked with an (*), please refer to "taxomomic notes" section. 

Figures 1-2. *BPachioZithus? sp. 

1. Septagonal form. Sample 13,130-13,140 ft; R87N5A; 

crossed nicols. 

2. Hexagonal form. Sample 12,730-12,740 ft; R86N36A; 

crossed nicols. 

3. ConusphaePa mexicana Trejo, Sample 12,470-12,480 ft; R86N30A; 

crossed nicols, gray filter. 

4. *Bidiscus? canthus Wilcoxon, Sample 12,630-12,640 ft; R86N33A; 

crossed nicols. 

5. *HexaZithus aff. H. noeZae Loeblich and Tappan, Sample 

12,020-12,030 ft; R86N25A; crossed nicols. 

6. PoZycosteZZa beckmannii Thierstein, Sample 13,840-13,850 ft; 

R87N16A; crossed nicols, blue filter. Present from 13,450 

to 13,930 ft (4,100-4,246 m) in COST No. B-3 well, but the 

lowest occurrences may be the result of caving (see text). 

7-9. *PoZycosteZZa senaPia Thierstein. 

7. Specimen with seven ridges. Sample 12,920-12,930 ft; 

R87N3A; crossed nicols. 

8. Specimen with six ridges. Sample 13,230-13,240 ft: 

R87N9A; crossed nicols. 

g. Specimen with six ridges. Sample 13,320-13,330 ft; 

R87N15A; crossed nicols. 

10. MicPanthoZithus obtusus Stradner, Sample 12,020-12,030 ft; 

R86N24A; crossed nicols. 

ll. *BPaaPudosphaePa aff. B. afPicana Stradner, Sample 8,260-8270 

ft; R86N2A; crossed nicols. 

12. *BPaaPudosphaePa afPicana Stradner, Sample 8~900-8,910 ft; 

R86N5A; crossed nicols. 

13. *MicPanthoZithus sp., Sample 12,590-12,600 ft; R87N32A; 

crossed nicols. 

82 
2 3 

4 5 6 

7 8 9 

10 11 12 13 

ORGANIC GEOCHEMISTRY 

R. E. Miller, n. M. Schultz, G. E. Claypool, 

M. A. Smith, H. E. Lerch, D. Ligon, 

D. K. Owings, and c. Gary 

PURPOSE AND SCOPE 

The COST No. B-3 well was drilled to a 

depth of 15,820 ft (4,822 m) for the purpose of 

estimating the petroleum potential and 

determining the stratigraphy and sedimentary 

history of the Baltimore Canyon Mid-Atlantic 

Slope. In this petroleum geochemistry study, 

the major objectives were to (1) evaluate those 

sedimentary units that could be considered as 

potential and possible liquid-petroleum or 

natural-gas source rocks, and (2) estimate and 

define the possible effects of mud additives on 

the source-rock characteristics. 

DEFINITION OF TERMS AND CONCEPTS 

The general concepts of thermal maturation 

of organic matter and petroleum generation 

employed in this study largely follow those of 

Vassoyevich and others (1970) and Tissot and 

Welte (1978). Terms used to describe the 

source-rock richness, maturity, and potential 

follow the usage of the reports by Claypool and 

others (1977) and Miller and others (1979). The 

organic richness of a source bed and its 

petroleum potential may be measured by (1) a 

minimum amount of total organic carbon (0.7-1.0 

weight percent for argillaceous rocks), (2) 

pyrolytic oil yields in excess of 0.2-0.3 

percent, and (3) solvent-extractable hydrocarbon 

concentrations in excess of 100-500 ppm. The 

degree to which organic matter progresses 

through a series of time-dependent kinetic 

reactions is expressed as the maturation stage 

of a source rock or source bed. Because some 

source beds contain organic matter that is 

predominantly of the humic and lignin type 

(hydrogen-poor), it is necessary for such rocks 

to contain more organic carbon than those 

sedimentary units that may contain predominantly 

marine algal organic matter (hydrogen-rich) to 

be considered as a petroleum source bed. The 

85 

required higher organic-carbon contents in the 

hydrogen-poor organic matter are based on the 

poorer convertibility of lignin ana. humic 

substances. Therefore, the nature and type of 

organic matter may be as significant as the 

total amount of organic matter in evaluation of 

the effectiveness of a source bed. 

Those sedimentary rocks that co~tain a 

predominance of biochemically derived 

hydrocarbons but which can be shown to be 

capable of generating petroleum hydrocarbons by 

pyrolysis are categorized as "immature." When 

organic-rich sedimentary rocks have n~t been 

altered by petroleum-generating reaction~ to the 

extent that a minimum amount of petroleum has 

been generated and physically expelled, the 

source rock is defined as "immature" (Claypool 

and others, 1977; Miller and others, 197~). 

The major criteria that characte1·ize and 

distinguish the stages of thermo~hemical 

conversion of the organic matter to oil are the 

molecular composition and the relative 

concentration of the indigenous extractable 

hydrocarbons. Source beds are described as 

being "mature" when extractable hydrocarbons are 

present in quantities of about 1-2 percent of 

the total organic carbon and the hydrocarbons 

are compositionally identical to petroleum. To 

define a source rock as "mature" infer;;- that a 

thermochemical conversion of the dis~eminated 

organic matter in shales or other sedi~~nts has 

taken place (Claypool and others, 1977; Miller 

and others, 1979). 

The terms "potential" and "possible" source 

rock refer to the degree of thermal maturity 

that an organic-rich rock has attained, ranging 

from "immature" (or "potential") source. rock to 

"mature" (or "possible") source rock (Claypool 

and others, 1977; Miller and others, 1979). 

ANALYTICAL PROCEDURE 

In the present study, the USGS analyzed a 

series of 24 well-cuttings samples from depths 
of 3,810 ft (1,161 m) to 15,600 ft (4,755 m). 

Prior to opening the sealed cans, a measured 

volume of the dead-volume air was withdrawn, and 

the cl to c4 hydrocarbon composition and 

distribution were determined on a Hewlett 

Packard model 5830 gas chromatograph equipped 

with a 6-ft x 0.125-in. (1.8-m x 0.318-cm) 

Porapak R column. The column temperature was 

programmed from an initial injection temperature 

of 149°F (65°C) at 11°F/min (6°C/min) for 11 

minutes; it was then programmed at 22°F/min 

(12°C/min) to a final temperature of 356°F 

(180°C). After the gas analyses for the c 1 to 

c4 light hydrocarbons were completed, the 

samples used in the experimental work were 

carefully removed from the 1-qt (0.95-L) sample 

cans and thoroughly washed through a Tyler 

number 100 mesh screen under running water to 

remove as much of the effects from the drilling 

mud as possible. While still wet, about 0.2 oz 

avdp (5 g) of each washed sample was immediately 

placed in a vial and stored under degassed water 

for analyses of the gasoline-range (c4 to c 7) 

hydrocarbons by gas chromatography. The 

gasoline-range (c4 to c 7) hydrocarbons were 

determined by adding a known volume (0.04-0.07 

oz avdp; 1-2 g) of sediment to a known volume 

of water in a sealed microblender at 198°F 

(92°C). After blending the sediment for 5 

minutes, the liberated light and gasoline 

hydrocarbons (C1 to c 7) diffused into the 

trapped air space at the top of the blender. A 

sample of the liberated gas was then injected 

onto the Perkin Elmer 3920 gas chromatograph 

equipped with a 50-ft (15-m) SCOT column with 

hexadecane-hexadecene-Kel-f (HHK) mixed phase. 

The column was operated isothermally at 77°F 

(25°C). 

The washed sample cuttings retained by the 

Tyler 100 mesh screen were air and oven dried at 

95°-104°F (35°-40°C). Each wet-sieved and dried 

sample was lithologically described under a 

binocular microscope, and all foreign substances 

were removed. Table 4 shows the lithologic 

descriptions of the samples analyzed. After 

each sediment sample was picked, it was passed 

through a set of Tyler mesh screens, and only 

those rock chips larger than 10-20 mesh were 

retained for the c 15+ hydrocarbon studies. Each 

sample was then ground, using a mortar and 

pestle, to pass through a 60-mesh screen and 

weighed. Aliquots were taken from the ground 

sample for total-organic-carbon determinations 

and thermal pyrolysis analysis. 

Details of the solvent-extraction 

techniques, liquid-column chromatography, and 

gas-chromatography procedures used for the c 15+ 

liquid-hydrocarbon analyses have been described 

previously (Miller and others, 1979). The 

general steps employed involve Soxhlet-solvent 

extraction, followed by removal of sulfur, and 

then elution-column chromatograph:r on silica 

gel. The saturated (paraffin-naphthene) 

fractions were analyzed both qualitatively and 

quantitatively on Perkin Elmer 3920 gas 

chromatographs. The columns used for the 

qualitative work were 8-ft x 0.125-in. (2.4-m x 

0.318-cm) stainless steel, packed with 3 percent 

OV-101, 100-to- 120 mesh GCQ. The column 

temperature was 176°F (80°C) at injection and 

was temperature programmed at a rate of 29°F/min 

(16°C/min) for 8 minutes; it was then programmed 

at 14°F/min (8°C/min) to a final temperature of 

572°F (300°C). Quantitative evaluations were 

made on an OV-1 50-ft (15-m) SCOT column. The 

column was held isothermally at an injection 

temperature of 212°F (100°C) for 1 minute; it 

was then temperature programmed at 7°F/min 

(4°C/min) to a final temperature of 473°F 

(245°C) and held at the final temperature until 

n-c32 eluted. 

The following expression, modified from 

Hunt (1974), was used to calculate the Carbon 

Preference Index (CPI): 

(%nc 25 + %nc 27 + %nc 29 + %nc 31 ) (%nc25 + %nc 27 + %nc 29 + %nc 31 > ___________ + ___________ _ 

(%nC24 + %nC26 + %nC28 + %nC30 %nC26 + %nC28 + %nC30 + %nC32 

Total organic carbon is a me,1sure of the 

organic richness of a source rocl:. Analyses 

were performed by the USGS (in triplicate) on 

dried, weighed aliquots of the Cl't'bonate-free 

residue produced by leaching with t 'lt, 6-Normal 

hydrochloric acid of approximately 0.07 oz avdp 

(0.2 g) of ground sample (less than 60 mesh) • 

'nle samples were combusted in a Perkin Elmer 

model 240 Carbon, Hydrogen, Nitrogen Analyzer. 

Organic-carbon analyses for tre thermalpyrolysis studies were also p~rformed by 

Rinehart Laboratories, Arvada, Colo., on 

equivalent sample splits using a chromic-acid 

oxidation method outlined in Bush (1970). 

The thermal-pyrolysis analyses reported 

here were performed by the USGS on a Rock-Eva! 

system following the principles of source-rock 

characterization of Espitalie and others 

(1977). Terminology used to describe the 

thermal-pyrolysis measurements follows that of 

Claypool and Reed (1976), Claypool and others 

(1977), Tissot and Welte (197 8), and Miller and 

others (1979). nte volatile-hydrocat'bon content 

(S 1

) is the free or existing hydrocarbon 

component (expressed as mgHC/gC (p~t)) that is 

already present in the rock aod that is 

volatilized when the rock is heated at 4 81' F 

(250'C) for 5 min. Hydrocarbons and related 

compounds that are generated by pyrolysis at 

temperatures from about 480 to 1 ,020' F (250 to 

550'C) from the nonvolatile orP,anic matter are 

86 
Table 4.--Lithologie desePiptions of COST No. B-3 1JJelt 

euttings used fop OPganie geoahemiaal analyses 

Depth 

Feet Meters 

3,810 1,161 

4,020 1,225 

4,530 1, 381 

5,190 1, 582 

5,610 1, 710 

6,100 1,859 

6, 700 2,042 

7,200 2,195 

7. 710 2,350 

8,220 2,505 

8, 700 2,652 

9,200 2,804 

9, 700 2,957 

Lithology 

Light-gray, soft, calcareous clay (99 

percent); broken shell fragments (micro and 

macro); traces of glauconite and quartz 

sand grains (1 percent). 

Light-gray, soft, calcareous clay (100 

percent); traces of broken shell fragments. 

Light-gray, soft, calcareous clay (100 

percent); traces of broken shell fragments. 

Light-to medium-light gray, calcareous shales 

(95 percent); discrete broken angular 

glauconitic sand with traces of 

Foraminifera (5 percent). 

Medium-hard to soft, buff to light-gray, 

calcareous shales (97 percent); 

Foraminifera, pyrite, and broken to angular 

glauconitic sand (3 percent). 

Light- to dark-gray, calcareous shales (90 

percent); light-brown to light-gray, 

calcareous siltstone with finely 

disseminated glauconitic sand (8 percent); 

Foraminifera and traces of pyrite (2 

percent). 

Light-brown to light-gray, silty, micaceous 

shale with medium to coarse, angular, 

clear, quartz sand (90 percent); wellrounded glauconitic sand, broken shell 

fragments, and Foraminifera (8 percent); 

pyrite and carbonaceous organic matter (2 

percent). 

Light-brown to dark-gray, silty, micaceous 

shale with traces of calcitic or dolomitic 

cement (90 percent); rounded glauconitic 

sand, pyrite, carbonaceous organic matter, 

and broken 'shells (10 percent). 

Light- to medium-gray, micaceous, silty 

claystone with light-brown calcareous 

cement (85 percent); brown, angular, 

cryptocrystalline -chert fragments (5 

percent); fine-grained sand with calcareous 

cement and glauconitic pellets (5 percent); 

pyrite, carbonaceous organic matter, 

Foraminifera, shell fragments (5 percent). 

Light- to dark-gray, medium-soft, friable, 

calcareous, micaceous clays tone ( 40 

percent); coarse, angular, quartz sand (40 

percent); light-brown to light-yellow, 

slightly calcareous argillaceous siltstone 

(15 percent); pyrite, carbonaceous organic 

matter, and traces of Foraminifera (5 

percent). 

Dark-gray to light-gray, calcite-cemented 

claystone to silty mudstone (75 percent); 

fine-grained, silty quartz grains floating 

in argillaceous matrix (20 percent); 

pyrite, carbonaceous organic matter, 

Foraminifera (5 percent). 

Light- to medium-gray, calcareous, silty clay 

(SO percent); coarse- to fine-grained, 

subangular to rounde,d, frosted quartz sand 

with calcite cement (40 percent); grayishbrown to tan limestone (5 percent); pyrite, 

glauconitic sand, trace of micaceous sand 

(5 percent). 

Light-gray to greenish-gray, calcareous, 

slightly micaceous, hard, brittle shale to 

mudstone (90 percent); light-buff to brown, 

dolomitic shale (7 percent); pyrite, 

Foraminifera, and well-rounded, frosted 

quartz grains (3 percent). 

Table 4.--Lithologic desaPiptions of COST No. B-3 1JJeU 

cuttings used fop oPgania geoahemiaal analyses--co,tinued 

Depth 

Feet Meters 

10,300 3,139 

10,800 3,292 

11,300 3,444 

11,800 3,597 

12,300 3, 749 

12,800 3,901 

13,300 4,054 

13,700 4,176 

14,300 4,359 

14_,900 4,542 

15,600 4, 755 

87 

Lithology 

Coarse- to medium-grained, sul angular, 

moderately well sorted, slightly ,frosted, 

quartz sandstone (55 percent); dark- to 

light-gray, micaceous shale (40 percent); 

gray to light-tan limestone, pyrite, 

carbonaceous organic matter, and traces of 

glauconitic sandstone (5 percent). 

Dark-gray, micaceous, silty shF le (45 

percent); light-brown to tan limestone with 

traces of gray or buff to brown pE'llets of 

siderite (30 percent); coarse- to mediumgrained, subangular to subrounded, 

moderately sorted, frosted sandstone with 

calcite cement (24 percent); glauconitic 

sand, carbonaceous organic ma':ter (1 

percent). 

Dark-gray to greenish-gray, brittle shale 

with waxy luster (50 percent); finegrained, moderately well sorted, buff to 

white sandstone with calcite cement (35 

percent); light-tan to gray, 

microcrystalline limestone (10 percent); 

buff to light-gray siltstone, carbonaceous 

organic matter (5 percent). 

Dark-gray to grayish-brown, noncalcareous, 

waxy, micaceous, silty shale (25 percent); 

gray, fine-grained, micaceous sandstone 

with traces of calcite cement (65 percent); 

grayish-brown to tan, crypto-cr:•stalline 

limestone (9 percent); glauconite, 

carbonaceous organic matter (1 percent). 

Brownish-gray, micaceous, silty shale (70 

percent); white to buff or gra:•, silty 

limestone (25 percent); grayish-white, 

calcite-cemented sandstone with traces of 

pyrite and greenish-gray glauconite grains 

(5 percent). 

Light-brown to tan, silty, micaceous shale 

(50 percent); brown to buff, fine·-grained, 

calcareous sandstone (40 percent); lightgray to greenish-brown, micaceous, slightly 

calcareous sandy shale with traces of 

pyrite (10 percent) 

Dark-gray to black, slightly silty, 

calcareous shale (80 percent); buff to 

light-gray, fine-grained, subangular to 

subrounded sandstone with calcite cement 

( 19 percent); pyrite (1 percent). 

Greenish-gray to dark-gra , slightly silty, 

micaceous shale (60 percent); light- to 

medium-gray, cryptocrystalline limestone 

with traces of pyrite (40 percent). 

Light-gc-qy to buff, fine-grained sandstone 

(25 percent); dark- to light-g-r:ay, slightly 

silty micaceous shale with traces of pyrite 

(75 percent). 

Dark-brown to grayish-black, slightly 

calcareous, micaceous shale (40 percent); 

light-gray to buff or white, mediumgrained, slightly calcareous sands':one with 

abundant biotite (30 percent); tan to 

grayish-white, cryptocrystalline limestone 

with traces of carbonaceous organic matter 

(30 percent). 

Dark-gray to black, micaceous shale (70 

percent); light-tan to grayish-buff, 

medium-grained sandstone with sone traces 

of biotite (20 percent); ligh':-tan to 

brown, cryptocrystalline limestone with 

traces of carbonaceous matter (10 percent). 
defined by the term s2 and are also expressed in 

units of mgHC/gC (ppt). Carbon dioxide 

generated from the kerogen is designated s3 and 

is expressed in units of mgco2/gC (ppt). 

If it is assumed that the pyrolysis 

measurements are not influenced by external 

interference from nonindigenous hydrocarbons, 

then a semi-quantitative evaluation of the 

original generation potential of the source rock 

that has been effectively transformed into 

hydrocarbons may be made and is represented by 

the symbol s1• The residual generation 

potential, that has not been used to generate 

hydrocarbons, is represented by the symbol Sr 

The sum, [S 1 + s21, can be expressed on a 

weight-percent basis as a measure of the 

generation potential of the source rock when 

expressed in KgHC/ton rock (Tissot and Welte, 

1978). In this study the sum (S 1 + s2) is 

expressed on a weight-percent basis. 

The ratio of pyrolytic-hydrocarbon yield to 

organic carbon in percent [S 1 + s2/organic C 

percent] is defined as a measure of the type and 

convertibility of the organic matter to 

hydrocarbons. In this study, the ratio [s 1ts 1 + 

s21 is emp).oyed as a measure of the thermal 

maturation of the organic matter. The maximum 

temperature at which the yield of volatile 

organic compounds is produced by pyrolysis of 

the solid organic matter (T 52 ) is also an 

indicator of thermal maturation (Tissot and 

Welte, 1978). In this study, the ratio of 

[S2/organic C] is designated as the hydrogenindex; [S3/organic C] is defined as the oxygenindex and may provide an indirect measure of the 

type of kerogen (Tissot and Welte, 1978). 

Atomic (hydrogen/carbon) ratios, carbon-isotopic 

compositions ( c 13PDB), and classes of relative 

percent of kerogen are also used to evaluate the 

type of kerogen. 

RESULTS AND DISCUSSION 

This study has focused on determining the 

source-rock potential of the sedimentary units 

present in the COST No. B-3 well. A combination 

of geochemical methods has been employed and 

evaluations have been made where inconsistencies 

appear to occur. The geochemical data and 

interpretations generated in this report are 

those of the USGS unless otherwise credited. 

The chemical composition and abundance of 

the extractable organic matter in source rocks 

generally reflects the richness and type of the 

original organic matter as well as the degree of 

thermal maturation, provided that the 

extractable organic matter is indigenous to the 

88 

sediments (Tissot and Welte, 1978). The USGS 

extractable-organic-matter data, saturated 

paraffin-naphthene gas chromatograms, and lighthydrocarbon analyses for the COST N':l• B-3 well 

are shown in table 5 and figures 31 through 

36. Characterization of the original genetic 

and residual source-rock potential, as well as 

the type and thermal maturity of the organic 

matter, was carried out by the USG'i' using the 

thermal pyrolysis method. These pyrolysis 

results are summarized in table 6. 

In addition to the independent geochemical 

studies conducted by the USGS, organic 

geochemical analyses completed by outside 

contractors were reported for th~ COST B-3 

participants on a separate suite of B-3 well 

samples. The results of this work have been 

summarized by Smith (1979), and the data have 

been made available by the USGS Conservation 

Division, Atlantic Area Office for Resource 

Evaluation, Washington, D.C., for reference and 

selective comparison. The contract data 

incorporated in this present study include a 

summary depth profile of the types of organic 

matter, as determined by optical m!!thods, for 

relative kerogen types and abundance (percent), 

and atomic hydrogen-carbon ratios (Core 

Laboratories, Inc., 1979); and stable-carbonisotope analyses of the saturated paraffinnaphthene and aromatic hydrocarbons, as well as 

total extractables and kerogen (J. G. Erdman, 

Phillips Petroleum Company, written 

communication, 1979). These source-rock typeparameters are compared with the US';S thermalpyrolysis kerogen-convertibility, as well as 

hydrogen and oxygen indices, and are shown in 

figure 37. Source-rock-maturity characteristics, based on optical thermal alteration index 

(TAI) values and vitrinite reflectance (R0 ) 

values (Core Laboratories, Inc., 1979) have been 

incorporated in this study and are co~pared with 

the USGS thermal-pyrolysis temperatures of 

maximum yield (T52 ) and the Carbon Preference 

Index (CPI) in figure 38. 

Because drilling operations must use 

certain mud additives, it is essential that each 

additive be "fingerprinted" by gas chromatography for the molecular compoE-ition and 

distribution of the c 15+ saturated paraffinnaphthene hydrocarbons, in order to avoid 

misleading interpretations of type and maturity 

of indigenous material. The gas chromatograms 

of the saturated paraffin-naphthene hydrocarbons 

and the concentrations of the paraffinnaphthene, aromatic, and nitrogen-sulfur-oxygen 

(NSO) compounds of the available additives are 

shown in figure 39 and table 7, respe~tively. 
Data on Source-rock Richness, Type, 

and Maturity of Organic Matter 

Tertiary 

The Tertiary section in the COST No. B-3 

well (3,800-6,040 ft; 1,158-1,841 m), is 

composed of calcareous mudstone, claystone with 

smaller amounts of argillaceous limestone, and 

siltstone. Trace components consist primarily 

of muscovite, shell fragments, microcrystalline 

limestone, buff-colored chert, glauconite 

grains, and, above 5,160 ft (1,573 m), some coal 

fragments (Lachance, 1979) (table 4). 

The COST No. B-3 Tertiary section has an 

average total-organic-carbon value of 1.5 

percent (by weight), which is considerably above 

the worldwide average of 0.27 percent for 

carbonate sediments according to Hunt (1961) and 

Gehman (1962). This higher total-organic-carbon 

value probably reflects the effect of oxygenminimum zone deposition of organic-rich clays 

and silts in these outer neritic to middle-shelf 

calcareous sediments. The total extractable 

hydrocarbons, however, average only 58 ppm, 

which falls within the very poor ran~e for 

liquid-hydrocarbon source rocks (Philippi, 1957; 

Baker, 1972). For these Tertiary sediments, the 

ratio of total hydrocarbon to total organic 

carbon (percent) averages 0.40, suggesting 

thermally immature sediments that have not 

generated and expelled liquid or gaseous 

hydrocarbons. This interpretation is consistent 

with the CPI value of 2. 7 for the r~solved 

saturated paraffin-naphthene hydrocarbo~s and 

the comparatively high concentration of NSO 

compounds (320 ppm) and lends further supryort to 

the view that the Tertiary saturated paraffinnaphthene hydrocarbons 

indigenous, biogenic, and 

(table 5, fig. 31). 

are predominantly 

thermally immature 

The ratio of the saturated paraffinnaphthene to aromatic hydrocarbons is ~. 9, an 

unusually high value for thermally immature 

sediments. This particular ratio, however, is 

not considered to respond to thermal history 

alone, but may also reflect the type and percent 

of the organic matter as well as the p-:~ssible 

presence of mud-additive contamination. As a 

Table 5.--0Pganie eaPbon and extpaetabte oPganie matteP, COST No. B-3 ~ett 

Ratio of 

saturated Carbon 

Organic Total Ratio of Ratio of hydrocarbon Preference 

DeJ2th carbon hydrocarbon hydrocarbon to extractable to aromatic Index 

Feet Meters (percent) (ppm) organic carbon organic matter hydrocarbon (CPI) 

Tertiary 

3,810 1,161 1.19 95.0 0.80 o. 34 1.42 2.17 

4,020 1,225 1.73 n.o -44 .19 1.28 3.4/ 

4,530 1,381 3.08 64.0 .21 .16 1.13 3-22: 

5,190 1,582 1-18 49.0 -42 .28 1.49 2-6~ 

5,610 1, 710 .45 6.0 .13 .13 9.33 1. 71 

Upper Cretaceous 

6,100 1,859 0.41 12.0 0.30 0.20 3.44 1.5(' 

6,700 2,042 .92 50.0 .54 • 1.2 1-39 1.6~ 

7,200 2,195 1.57 36.0 .23 .22 .96 1-27 

7, 710 2,350 .72 780.0 10.83 .63 1-83 1.0!-

8,220 2,505 .42 48.0 1.15 .37 .61 1.9:: 

Lower Cretaceous 

8,700 2,652 0.87 73.0 0.84 o.so 1.63 0.8~ 

9,200 2,804 .66 143.1) 2.17 .65 1.30 1.21 

9,700 2,957 .72 52.0 .72 .42 .78 2. 2l· 

10,300 3,139 .so 81.0 1.62 -49 .34 1.03 

10,800 3,292 • 70 106.0 1.52 .56 .94 1.50 

11,300 3,444 .55 69.0 1.25 .48 .37 1.67 

11,800 3,597 1.05 387.0 3.69 .65 .92 1-77 

12,300 3,749 .64 45.0 .70 .40 .20 2.47 

Upper Jurassic 

12,800 3,901 0.76 229.0 3.00 o. 72 1.44 0.69 

13,300 4,054 .89 1,064.0 11.95 .81 2.48 .70 

13,700 4,176 .41 67.0 1. 63 .'i4 .99 1.46 

14,300 4,359 1.05 716.0 6.82 .82 2.32 .95 

14,900 4,542 1.02 288.0 2-83 .69 1.09 1.12 

15,600 4,755 2.25 160.0 .71 ,57 .55 1-31 

89 
2000 

4000 

~ 

~ 

~ ---6000 

(I) 

:::::> a::O 

~~ S a....:t 

:::::>>-

>- ~ 8000 ~ u 

z 

- (I) 

:I: :::::> >- 0 Cl... LLJ 

~ ~ 10.000 t;:; 

a: 

<-> 

a: 

~ _. 12.000 

<-> 

~ 14,000 

~ ;;; 

16.000 

Figure 

TOTAL EXTRACTABLES 

I ppm I 

200 400 600 800 1000 1200 

PARAFFIN-NAPHTHENE 

I ppm I 

1 00 200 300 400 500 600 7 00 40 

AROMATIC HYDROCARBONS 

I ppm I 

ELUTED NSO 

I ppm I 

80 120 160 200 240 280 320 0 40 80 120 160 zoo 240 280 •320 

1000 

2000 

3000 

4000 

31.--Summary of organic-richness analyses on c15+ hydrocarbon extractables of samples from the COST No. B-3 well. 

ffi 

t;:; 

~ 

~ 

::r:: 

a; 

Cl 
2000 

4000 >- a::: 

<( 

~ ---6000 

C/J 

=> 

co ~~ =>tu 

""""' tu a::: 8000 '-' ~ 

~ (/) 

:I: => 

~ 0 

'-' 10,000 i 

a::: 

?: 

g 12,000 

'-' C/l 14,000 

~ 

16,000 

TOTAL HYDROCARBON 

TOTAL EXTRACT 

02 0 4 0 6 0 8 1 0 

PARAFFIN-NAPHTHENE 

TOTAL EXTRACT 

02 0 4 06 

TOTAL ORGANIC 

CARBON 1%1 

TOTAL HYDROCARBON 

TOTAL ORGANIC CARBON 1%1 

0 4 0 8 1 2 1 6 2 0 2 4 2 8 3 2 0 2 0 4 0 6 0 8 0 10 0 

PARAFFIN-NAPHTHENE 

AROMATIC HYDROCARBON 

0 4 0 8 1 2 1 6 2 0 2 4 2 8 3 2 

Figure 31.--Summary of organic-richness analyses on c15+ hydrocarbon extractables of samples from the COST 

No. B-3 well--continued. 

1000 

2000 

~ 

~ 

~ 

~ 

:I: 

~ 3000 

4000 
result, this seemingly inconsistent value 

reflects more of the nature and type of the 

extractable hydrocarbons than the thermal 

history of these Tertiary sediments. A 

comparatively low ratio (0.22) of total 

hydrocarbon extractables to total extractable 

organic matter for the Tertiary interval is 

believed to be consistent with an interpretation 

of a predominantly indigenous, thermally 

uncontaminated, immature section (table 5, fig. 

31). 

Figure 32 shows a series of saturated 

paraffin-naphthene hydrocarbon gas chromatograms 

for Tertiary sediments down to 6,040 ft (1,841 

m). These gas chromatograms illustrate a 

predominantly bimodal distribution for the 

resolved aliphatics and a molecular hydrocarbon 

assemblage that ranges from n-c 14 to n-c34 • The 

paraffin-naphthene unresolved complex mixture is 

equal to or predominates over the resolved 

aliphatics, a characteristic signature that 

usually suggests a low-temperature thermal 

history for the liquid c 15+ hydrocarbons. 

Inconsistent with this interpretation is the 

fact that the isoprenoid pristane and phytane 

hydrocarbons are dominated by the normal alkanes 

CARBON NUMBER 

10 12 14 16 18 20 22 24 26 28 30 32 34 

TIME-TEMPERATURE 

36 

3810 It 

1161 m 

4020 It 

1225 m 

4530 ft 

1381 m 

in these Tertiary rocks, a c,_,aracteristic 

normally associated with mature hyd~ocarbons. 

The Tertiary light hydrocarbo,s (C1 to c

4 ) 

show the second highest concentration (15,500 

ppm (volume c 1 to c 4 per volume of rock) at 

4,020 ft (1,225 m)) for the COST No. B-3 well 

sample. In this same interval, the gasolinerange hydrocarbons (C5 to c 7) have a 

concentration of 700 ppm. The lo~~ gas-wetness 

percentage c 2_c4 x 100 suggests that the major 

C1-C4 

component of this shallow gas is probably 

biogenic methane (fig. 33). However, the nc4/n-c7 ratio is much less than unity for the 

same interval. This particular ratio has been 

interpreted as being diagnostic of diesel fuel 

and may suggest the influence of nonindigenous 

hydrocarbons possibly associated with dieselfuel contamination (K. F. Thomp~on, written 

communication, 1977). The remainder of the 

Tertiary below 4,020 ft (1,225 n) shows low 

concentrations (less than 200 ppm) of c 1 to c4 

and a progressive decrease in the amount of the 

Cs to C7 gasoline-range fraction to less than SO 

ppm. Similarly, the gas-wetness percentage 

CARBON NUMBER 

10 12 14 16 18 20 22 24 26 28 30 32 34 36 

5190 ft 

1582 m 

5610 It 

1710 m 

Figure 32.--Gas-chromatographic analyses of saturated paraffin-napthene hydrocarbons of Tertiary 

rocks above 6,040 ft (1,841 m), COST No. B-3 well. 

92 
~ co 

(,.) ~ 

:X: 

~ 

2000 

2000 

4000 

ii: 

<( 

~ ---6000 

en 

::::> a::O 

a...<( 

~~ 

::::>~ a: 8000 (..) 

en 

::::> 

§ 

~ 10,000 

5 

a: 

3:: 

0 

--' 12,000 

(..) 

c;;; 14,000 

TOTAL C1-C4 (ppm) 

4000 6000 8000 10,000 200 

TOTAL C5-C7 (ppm) 

400 600 800 

GAS WETNESS 

(%) 

20 40 60 80 100 0 

c4 

c1 

10 12 14 

~ 16,000 t_~ __ _L __ _L __ _L __ _L __ _L __ ~--~--~--L---~~~_j--~ __ _i~_L __ _L __ _L __ _L __ L__L ____ _L_L~_L_L~~~~~LL~-L-L-L_L-L_L~~~~~----

( 

C :+-C:J+IC +nC ~ Gas wetness (percent) 2 4 4 x 1 00 

C1+C2+C3+1C4+nC4 

Figure 33.--Summary of light-hydrocarbon analyses from the Cost No. B-3 well. 

1000 

2000 en 

a: 

L.LJ 

~ 

~ 

:X: 

fr; 

0 

3000 

4(!00 
decreases with increased burial depth to values 

less than 5 percent (fig. 33). Such 

relationships tend to confirm low thermal 

maturity for the organic matter. 

Thermal-pyrolysis maximum-yield temperatures for these Tertiary sediments range from 

757 to 817°F (403° to 436°C) which is consistent 

with an interpretation of thermal immaturity. 

The ratio of the total pyrolytic hydrocarbons 

(s 1 + s2) to total organic carbon is a measure 

of the convertibility of the organic matter to 

hydrocarbons (Claypool and others, 1978; Miller 

and others, 1979). With the exception of one 

sample at 4,530 ft (1,381 m), which has a 

convertibility factor of 29.88 percent and also 

has the highest organic-carbon content (3.28 

weight percent) in these Tertiary sediments, the 

average convertibility factor is 7. 33 percent, 

which indicates the predominance of hydrogenlean kerogens. This low convertibility ratio is 

also reflected in the characterization of the 

kerogens by their hydrogen and oxygen indices of 

129 mgHC and 65 mgC02 respectively. The 

gC gC 

thermal-pyrolytic parameters indicate that the 

Tertiary sediments are thermally immature and 

have poor liquid-hydrocarbon source-rock 

potential (table 6). 

Upper Cretaceous 

Upper Cretaceous sediments extend from 

6,040 to 8,690 ft (1,841 to 2,649 m) and are 

characterized by outer neritic, gray siltstones 

grading into mudstones in the sectio, from 6,040 

to 6,290 ft (1,841 to 1,917 m). Below this 

interval, from 6,290 to 8,200 ft (1,917 to 2,499 

m), the sediments are composed of ortter neritic 

to marginal-marine calcareous shales that are 

intercalated with light-gray to buff, dolomitic, 

sandy limestones. Glauconite is common to 

abundant in the more sandy intervals. From 

8,200 to 8,690 ft (2,499 to 2,649 m), 

interbedded sandstones, shales, an1 mudstones 

occur with relatively minor limestones and coal 

(table 4; Lachance, 1979). 

The Upper Cretaceous interval has an 

average total-organic-carbon conte~t of 0.83 

percent, an average total-~xtractablehydrocarbon content of 36 ppm, and an average 

NSO concentration of 6 7 ppm if the 7, 710-ft 

(2,350-m) sample is excluded from the 

calculations. This anomalous sample has higher 

concentrations of total hydrocarbon"' (779 ppm) 

and of NSO's (160 ppm), but the total organic 

carbon (0.72 weight percent) is comparable with 

the average total organic carbon fc-.:- the Upper 

[--- undetectable or unable to determine; * numerically zero or one] 

Total 

Sample 

de2th ~:;::~~ s1 s2 

(weight mgHC/g mgHC/f, 

Feet Meters 2ercent) <22t) <22t) 

3,810 1,161 1.03 0.122 0.27 

4,020 1, 225 1. 76 .023 2. 39 

4,530 1, 381 3. 28 9.Ao 

5,190 1, 5A2 1.19 1. 3R 

5. 610 1, 710 • 54 • 37 

6,100 1, 859 0.33 0.027 * 6,700 2,042 1. 30 .011 4.QA 

7. 200 2,195 1. 59 .31 

7. 710 2, 350 1. 05 1.05 

8,220 2,505 .40 • 32 

8, 700 2,652 1. 31 0.45 

9, 200 2,804 .87 

9, 700 2,957 .45 • 24 

10,300 3,139 .69 * 10,800 3,292 • 74 .19 

11,300 3,444 .70 0.034 !. 29 

12,300 3, 749 .72 .25 

12,800 3,901 0.92 0.034 0.38 

13,300 4,054 • 70 .13 • 50 

13,700 4,176 • 37 .07 * 14,300 4,159 1. 15 .os .42 

14,900 4. 542 1. 25 .04 1.07 

15,600 4, 755 2.12 .03 1.60 

1Rock-Eval pyrolysis by Robert Peterson, n.s. 2organic-carbon analyses, wet-oxidation method 

53 s1 + s2 s 2/org. c s 3/org. 

mgC0 2 /g (weight mgHC/gC mgC0 2/gC 

(p2t) percent) 

Tertiary 

1.58 0.04 26 153 

.98 .24 136 56 

1.14 .98 299 35 

.44 .14 116 37 

.26 .04 69 48 

Upper Cretaceous 

0.54 0.003 164 

.48 .41 314 37 

.5R .03 20 36 

.95 .11 100 90 

.67 .03 81 168 

Lower Cretaceous 

o. 73 0.05 35 56 

* * 1.24 .02 52 275 

• 51 74 

.53 .02 26 72 

.ss .13 11'l5 79 

.51 .02 34 71 

Upper Jurassic 

1.18 0.04 41 128 

2.06 .06 71 295 

.52 .01 141 

.46 .05 37 40 

.so .11 86 40 

.37 .16 75 17 

Geological Survey, Lakewood, Colo. 

by Rinehart Laboratories, Inc., Arvada, Colo. 

94 

c TS 

421 

406 

403 

427 

436 

430 

436 

421 

424 

448 

436 

436 

445 

430 

448 

436 

439 

0.31 

.01 

* 

.003 

* 

* 

* 

* 

.03 

o.os 

.20 

* .11 

.04 

.02 

3. 79 

13.69 

29.88 

1l. 76 

7.41 

0.91 

31.54 

1.89 

10.48 

7 .so 

3.82 

4.44 

2. 70 

1A. 57 

2. 78 

4.35 

8.57 

2. 70 

4.35 

8.80 

7. 55 
Cretaceous. With the exception of the 7,710-ft 

(2,3SO-m) sample, the Upper Cretaceous sediments 

are poor to lean source rocks for the generation 

of liquid hydrocarbons (table S, fig. 31). 

The saturated paraffin-naphthene hydrocarbon gas chromatograms for the Upper 

Cretaceous rocks are shown in figure 34. The 

gas chromatograms for the 6,100-ft (1,8S9-m) to 

7,200-ft (2,19S-m) samples are characterized by 

the dominant bimodal, unresolved, paraffinnaphthene mixture. The less pronounced resolved 

aliphatics in this interval have a molecular 

composition and boiling-point range that extend 

from about n-C1s to n-c30, with a CPI ratio that 

averages 1.47. In samples from 7,200 ft (2,19S 

m) to 8,690 ft (2,649 m), the bimodal unresolved 

paraffin-naphthene hydrocarbons are comparable 

with the resolved aliphatics, and the CPI ratio 

averages 1.41 (table 6). 

The longer chain (n-c20 to n-c30) 

hydrocarbons are predominant in the 7,710-ft 

(2,350-m) sample and have an odd-to-even ratio 

of 1.04. The shorter chain (n-c 17 to n-c20) 

hydrocarbons are the major, resolved, aliphatic, 

molecular species in the 8,220-ft (2,SOS-m) 

CARBON NUMBER 

10 12 14 16 18 20 22 24 26 28 30 32 34 

TIME-TEMPERATURE 

36 

6100 ft 

1859 m 

6700 ft 

2042 m 

7200 It 

2195 m 

sample (fig. 34). The longer chain hydr~carbon 

assemblages may be indicative of plant-wax 

hydrocarbons, or, for those sections ir which 

the input of terrestrial sediment and organic 

matter is negligible, the longer chain 

hydrocarbons may be derived from marine 

planktonic algae and bacteria. When marine 

plankton and algae are the major source of 

input, the CPI value may be near unity even in 

thermally immature sediments (Tissot and Welte, 

1978). Thus, the low CPI value fo·md in 

sediments otherwise indicated to be immature 

indicates derivation of long-chain n-q.lkanes 

from marine plants. The shorter chain normal 

aliphatics (n-C1s to n-c 17) also occur in marine 

zooplankton, with pristane as the major 

saturated component along with unsaturated 

isoprenoid hydrocarbons and the unsaturated 

hydrocarbon squalene (Blumer, 196 7; Bluner and 

others; 1969; Gelpi and Oro, 1968). 

Throughout the Upper Cretaceous s~ction, 

only the 8,220-ft (2,SOS-m) sample c?ntains 

significant concentrations of c 1 to C~ light 

hydrocarbons (7,000 ppm) and Cs to c 7 gasolinerange hydrocarbons (12S ppm). The gas is mainly 

CARBON NUMBER 

10 12 14 16 18 20 22 24 26 28 30 32 34 36 

~ 

7710 It 

J.. A • ~ d.. A 8220 It "'IVJifWY'.'""'\t,.. 

~ 

2505 m 

Figure 34.--Gas-chromatographic analyses of saturated paraffin-napthene hydrocarbons of Upper 

Cretaceous rocks below 6,040 ft (1,841 m), COST No. B-3 well. 

95 
composed of methane, with a gas-wetness value of 

less than 2 percent, which may indicate a low 

temperature history for the organic matter. A 

point that must not be discounted in the 

interpretation, however, is the value of the nc4/n-c7 ratio, of approximately unity, which 

suggests the presence of trace amounts of 

nonindigenous hydrocarbons possibly from 

anthropogenic sources (fig. 33). 

The thermal pyrolysis temperatures (T 52 ) 

for Upper Cretaceous samples ranges from 790 to 

817°F (421 to 436°C) and fall within the range 

for thermally immature organic matter (Tissot 

and Welte, 1978). Further support for an 

interpretation of thermally immature organic 

matter in the Upper Cretaceous section is 

provided by the average-total-hydrocarbon to 

total-extractable-matter ratio of 0.30 and an 

average CPI ratio of 1.4 (tables 5 and 6, fig. 

31) • The presence of hydrogen-deficient, gasprone kerogens in the major part of the Upper 

Cretaceous section is also indicated by the low 

average pyrolytic-hydrocarbon to organic-carbon 

ratio of 5.2 percent. This average-ratio 

calculation excludes the 6,700-ft (2,042-m) 

sample, which has a pyrolytic hydrocarbon/total 

organic carbon percent yield of 31. 54. The 

higher ratio for the 6, 700-ft (2, 042-m) sample 

indicates a greater proportion of hydrogen-rich, 

amorphous, algal-type kerogens. 

The very low to undetectable or 

unmeasurable generation potential (S 1) as 

determined by pyrolysis is consistent with an 

interpretation of poor to lean liquidhydrocarbon source rocks for the major portion 

of the Upper Cretaceous section from 6,040 ft to 

8,690 ft (1,841 to 2,649 m) with the exception 

of the 6,700-ft (2,042-m) sample. Further 

evidence of the poor potential for liquidhydrocarbon generation for these Upper 

Cretaceous sediments is provided by an average 

pyrolytic-hydrogen index of 69 m:~c ,and an 

average oxygen index of 103 mgC02 (tables 5 and 

6, fig. 31). gC 

Lower Cretaceous 

The Lower Cretaceous section in the COST 

No. B-3 well ranges from 8,690 ft (2,649 m) to 

12,400 ft (3,780 m) and is characterized by 

marginal-marine, shallow-shelf, and outer shelf 

depositional environments. The lithologies are 

sandy, calcareous shales and mudstones 

intercalated with thin, light-gray to brown 

sandstones and limestones interbedded with minor 

amounts of coal. Very small amounts of 

glauconite, pyrite, siderite, and shell 

fragments occur as trace constituents (table 4; 

Lachance, 1979). 

The Lower Cretaceous interval is 

characterized by an average total~c~ganic-carbon 

content of 0.71 percent, an average totalextractable-hydrocarbon concentration of 120 

ppm, and an average NSO content of 84 ppm (table 

5, fig. 31). These organic-carbon and totalextractable-hydrocarbon values indicate poor 

source-rock richness and quality for liquidhydrocarbon generation (table 5, fig. 31). The 

averages for the total-hydrocarbor to organiccarbon ratio (percent), the total-hydrocarbon to 

extractable-organic-matter ratio, and the 

saturated-paraffin-naphthene to aromatic ratio 

for the Lower Cretaceous are 1.56, 0.52, and 

o. 81, respectively. These values suggest 

immature to marginally mature organic matter 

with respect to liquid-hydrocarbon generation 

(table 5, fig. 31). 

96 

The saturated paraffin-naphthene hy~rocarbon gas 

chromatograms for the samples taken from the 

Albian section at depths of 8, 700 ft (2,652 m) 

and 9,200 ft (2,804 m) are characterized by a 

bimodal, unresolved, complex mixture relative to 

the comparatively weak, resolv~d aliphatic 

signatures (fig. 35). This is ccnsistent with 

thermal immaturity. The resolved r0rmal alkanes 

have a molecular composition ani range that 

extend from n-c 15 to n-c30 • Because of the 

restricted range and the effect that small 

concentration values may have on the CPI-ratio 

calculations of the concentrations beyond n-c 22 , 

the use of the CPI ratio as an indicator of 

maturity is limited (Miller and others, 1979; 

Swetland and others, 1978). In the Albian 

section, the CPI value for the 8,700-ft (2,652-

m) sample is 0.88, whereas the CPI ratio for the 

9,200-ft (2,804-m) sample is 1.21. These ratios 

imply that thermal-maturation proc~sses may have 

started. However, the change in the ratio with 

depth of burial probably also reflects the 

variations in types of organic matter. The 

normal alkanes dominate the isoprenoid 

hydrocarbons (pristane and phytane) in the 

Albian samples and may reflect the nature of the 

organic matter as well as thernal-maturation 

effects. The saturated paraffin-naphthene 

hydrocarbons for the Aptian (9,700 ft; 2,957 m) 

and Barremian (10,300 ft; 3,319 m) samples, with 

differing CPI ratios of 2.2~ and 1.03, 

respectively, nevertheless have similar gross 

compositions in that the bimodal, unresolved, 

complex mixture is equal to or dominates the 

resolved aliphatics. Such gas-cl romatographic 

features are unlike matur~ petroleum 

hydrocarbons and are consistent with thermal 

immaturity (fig. 35). 

Lower Cretaceous (Hauterivian) rocks from 

10,800 ft (3,292 m) to 12,300 ft (3,749 m) have 
CARBON NUMBER 

10 12 14 16 18 20 22 24 26 28 30 32 34 

TIME-TEMPERATURE 

36 

9200 It 

2804 m 

9700 It 

2957 m 

10,300 It 

3139 m 

CARBON NUMBER 

10 12 14 16 18 20 22 24 26 28 30 32 34 36 

10,800 It 

3292 m 

11,300 It 

3444 m 

11,800 It 

3597 m 

12.300 It 

3749 m 

Figure 35.--Gas-chromatographic analyses of saturated paraffin-naphthene hydrocarbons of Lower 

Cretaceous rocks below 8,690 ft (2,649 m), COST No. B-3 well. 

a saturated-hydrocarbon mixture which has a 

bimodal character. At 12,300 ft (3,749 m), 

however, the resolved aliphatics are equal to or 

dominate the bimodal, unresolved, complex 

mixture of cycloparaffins and naphthenes. Also 

at this depth, the resolved aliphatics have a 

CPI value of 2. 466, a hydrocarbon to organiccarbon ratio of 0.7, a hydrocarbon to 

extractable-organic-matter ratio of 0.40, and a 

saturated-hydrocarbon to aromatic ratio of 

0. 20. Each of these values is consistent with 

an inter-pretation of thermally immature organic 

matter (figs. 31 and 35, table 5). 

Over the entire Lower Cretaceous interval, 

the cl to c4 light hydrocarbons are low, 

averaging only 685 ppm. The 12,300-ft (3,749-m) 

sample contains as much as 700 ppm of the 

97 

gasoline-range (C5 to c 7) hydrocarbons, with a 

50 percent gas-wetness ratio. This interval 

contains the highest gas-wetness percenta~e for 

the Lower Cretaceous interval. If the n-c4/n-c7 

ratio is a true indicator of the influe ... ce of 

diesel fuel, then the 1.5 ratio would s-uggest 

that anthropogenic influences from diesel fuel 

are probably not a significant factor in the 

11,800 ft (3,597 m) sample. However, the low 

total-gas concentrations for this interv,.l may 

suggest that catagenic processes have n•'lt yet 

progressed to a significant degree (fig. ~3). 

Thermal-pyrolysis analyses of the Lower 

Cretaceous rocks indicate that the most 

prevalent type of kerogens present are of the 

hydrogen-poor, oxygen-rich variety, with an 

average hydrogen index of 74 mgHC and ar gC 
mgC02 

average oxygen index of 114-gc-. These values 

are consistent with the average pyrolytic 

convertibility of the organic matter, which is 

6.S7 percent. With the exception of the 10,800-

ft (3,293-m) sample, which has an unusually high 

temperature of maximum yield (T5 ) of 838°F 0 2 (448 C), the temperature index ranges from 790 

to 817°F (421°C to 436°C) and is consistent with 

an interpretation of marginal thermal immaturity 

for the Lower Cretaceous (table 6). 

Jurassic 

The Upper Jurassic interval penetrated in 

the COST No. B-3 well ranges from 12,400 ft 

(3,780 m) down to the total well depth of 15,820 

ft (4,822 m) and includes outer to inner shelf 

and nonmarine sediments. The section from 

12,400 ft to 12,710 ft (3,780 m to 3,874 m) 

includes intercalated calcareous, light-gray 

sandstones, medium- to dark-gray shales, and 

comparatively thin, gray to light-gray, oolitic 

limestones. Below 12,710 ft (3,874 m), the 

section is composed of increasing amounts of 

silty, micaceous, dark- to light-gray, 

calcareous shales, and coals interbedded with 

oolitic, algal, and pelletal limestones (table 

4; Lachance, 1979). 

If the 13,300-ft (4,0S4-m) sample, which is 

believed to contain nonindigenous extractable 

hydrocarbons, is excluded, then the Upper 

Jurassic sediments sampled here (table S) have 

an average total-organic-carbon value of 1.09 

percent, an average total-extractablehydrocarbon content of 28S ppm, and an average 

NSO concentration of lOS ppm. The organicrichness properties of the organic carbon and 

extractable hydrocarbons suggest that these 

sediments have fair to good source-rock 

potential (table S, fig. 31). 

The 13,300-ft (4,0S4-m) sample has a totalorganic-carbon content of 0. 89 percent and an 

extractable-hydrocarbon concentration of 1,063 

ppm. The abnormally high total-extractablehydrocarbon to total-organic-carbon ratio of 

11. 9S percent for this interval indicates the 

probable influence of nonindigenous hydrocarbons 

for this interval. 

The CPI values and saturated paraffinnaphthene to aromatic average ratios for the 

Upper Jurassic interval are 1.33 and 1.28, 

respectively. These ratios, together with the 

average hydrocarbon to organic-carbon ratio of 

3.13 percent, indicate that the hydrocarbongeneration process is in progress (table S, fig. 

31). 

The saturated paraffin-naphthene hydrocarbon gas chromatograms for the sample taken 

from the Tithonian section at a depth of 12,800 

98 

ft (3,901 m) are characterized by a strongly 

bimodal, unresolved, complex mixture that 

dominates a relatively narrow range from n-c15 

to n-c 26 of resolved aliphatics (fig. 36). 

Kimmeridgian samples from 13,300 ft (4,0S4 m), 

13,700 ft (4,176 m), 14,300 ft (4,3S9 m), 14,900 

ft (4,S42 m) and 1S,600 ft (4,7SS m) were 

examined. At 13,300 ft (4,0S4 m), the resolved 

aliphatics are very weak, po01·ly resolved, 

restricted in range (n-c1s to n-c22 ), and 

dominated by a very stronrly bimodal, 

unresolved, complex mixture of paraffinnaphthenes. The 13, 700-ft (4, 176-~m) sample has 

a comparatively well developed, resolved 

aliphatic component from n-c1s to n-c30 relative 

to a very weak, bimodal, unresolved mixture. 

From 14,300 ft (4,3S9 m) down to e burial depth 

of 15,600 ft (4,75S m), there is a progressive 

decrease in the magnitude of the unresolved 

envelope and a relatively consistert increase in 

the distribution and molecular c~mposition of 

the resolved, aliphatic, saturated paraffinnaphthene hydrocarbons. 

The Upper Jurassic shows a significant 

increase in the concentratior of light 

hydrocarbons beginning with the 14,300-ft 

(4,3S9-m) sample, which has 8 cl to c4 

concentration of 11,300 ppm and a gas wetness of 

2S percent (fig. 33). The cl to c4 light 

hydrocarbons show a further increase to 27, S83 

ppm at 14,900 ft (4,S42 m) and 47,102 ppm at 

1S,600 ft (4,7S5 m), with a gas wetness of 18-19 

percent. The Cs to c 7 rasoline-range 

hydrocarbons average 28S ppm for the Jurassic 

interval, and the n-C4/n-c7 ratio is well above 

unity, ranging from l.S to 14.0. This indicates 

that anthropogenic sources are most probably not 

a factor. The progressive increas~ in the c1 to 

c4 light-hydrocarbon concentrations confirms the 

onset of thermal maturity end suggests 

significant generation of light hy~rocarbons in 

sediments at depths below 14,300 ft (4,3S9 m). 

This interpretation is supported by the observed 

increase in concentration of the c 15 to c 20 

hydrocarbons in the c 1s+ liquid-hyirocarbon gas 

chromatograms for samples below 14,300 ft (4,3S9 

m) (figs. 33 and 36). 

These Upper Jurassic sedim~nts contain 

kerogens that are primarily hydrogen-poor and, 

based upon their organic-richness 

characteristics, may be classified as good gasprone source rocks. This interpretation is 

consistent with the results of the thermalpyrolysis analyses which show the average 

hydrogen and oxygen indices to be 62 mgHC and m~02 ~ 110 ~ , respectively, which are consistent 

with a hydrogen-poor, Type III (humic-coaly) 
CARBON NUMBER 

10 12 14 16 18 20 22 24 26 28 30 32 34 

TIME-TEMPERATURE 

36 

12,800 It 

3901 m 

13,300 It 

4054 m 

13.700 It 

4176 m 

CARBON NUMBER 

10 12 14 16 18 20 22 24 26 28 30 32 34 36 

14.900 It 

4542 m 

--

15,600 It 

4755 m 

Figure 36.--Gas-chromatographic analyses of saturated paraffin-naphthene hydrocarbons of Jurassic 

rocks below 12,400 ft (3,780 m), COST No. B-3 well. 

kerogen. The temperature of maximum pyrolysis 

yield (T5?) for the solid organic matter in 

the Upper Jurassic ranges from 806 to 838°F 

(430° to 448°C) (table 6). 

A Comparative Discussion of Kerogen 

Types, Stable-Carbon-Isotope Ratios, 

Atomic-Hydrogen to Carbon Ratios, 

Thermal Alteration Indices, and 

Vitrinite Reflectance with USGS 

Thermal-Pyrolysis and CPI Values 

The measurements of the types of organic 

matter in the Tertiary, Cretaceous, and Upper 

Jurassic sediments of the COST No. B-3 well are 

shown in figure 37. Geochemical parameters 

indicative of the nature of the solid organic 

matter are the relative kerogen type and 

abundance (Core Labs, Inc.), atomic-hydrogen to 

carbon ratio (Core Labs, Inc.), carbon isotopic 

composition (Phillips Petroleum Company), and 

the hydrogen and oxygen indices as determined by 

99 

thermal pyrolysis (USGS). Figure 38 summarizes 

properties sensitive to thermal maturit?• Such 

parameters include the thermal alteration index 

(TAI) and vitrinite reflectance (R0 ) (Core Labs, 

Inc.), and the Carbon Preference Index (CPI) and 

temperature of maximum pyrolysis yield (T 52 ) 

(USGS). 

Tertiary 

The most abundant kerogens in the Tertiary 

section are the algal-amorphous type, which have 

atomic-hydrogen to carbon ratios that vary from 

1.0 to 1.25. However, the values of the 

kerogen-pyrolysis hydrogen and oxygen in.dices in 

mgHC the same interval are low, averaging 129 -cand 65 mgCOz , res ectively. The stable-cJrbonisotope t?.itios, 1fc1 12c (given as c13 values 

in parts per thousand (permil) standard 

deviations from the PeeDee Belemnite (PDB) 

carbonate standard), have values of 23.5 to 

26.0, which is in the range for organic carbon 

derived from marine as well as ronmarine 
2000 

4000 

ir 

~ 

§ 

t-~ 6000 

Cll 

:::> 

ffi§ 

~~ t- 8000 5 ~ ...... ~ Cll 

:::> 8 i ~ 10,000 

~ a: 

~ g 12.000 

u 

gj 14,000 

! 

16,000 

RELATIVE KEROGEN 

TYPE AND ABUNDANCE 

20 

1%) 

40 60 

CORE LABS 

~ ALGINITE 

D EXINITE 

D ,VITRINITE 

OTHER 

80 100 0 0 2 

ATOMIC 

HYDROGEN/CARBON 

I RallO) 

0 4 0 6 0 8 1 0 12 

CORE LABS 

• SIDEWALL CORES 

• CUTIINGS 

1 4 -30 

CARBON 

ISOTOPIC 

COMPOSITION 

lc5C13pDB) 

-28 -26 

00 )I. 

', 

o'O II : 

~uo • •x 

ao.o • ACD 

r:/i•o 

00 X 

ill 

-24 

t 0 cii 

-22 

PHILLIPS PETROLEUM 

-20 

o EXTRACTABLE ORGANIC MATTER 

X KEROGEN 

D AROMATIC 

• SATURATES 

0 20 

s3 

S2/C ORGANIC ORGANIC CARBON 

( mgHC/gC) lmgCO/gC) 

60 100 140 180 220 260 300 0 40 80 120 160 200 

USGS USGS 

Figure 37.--Summary profile of indicators of types of organic matter present in the COST No. B-3 well, 

as a function of depth. 

240 280 

1000 

2000 Cll 

a: 

t-

~ 

;!; 

I 

~ 3000 

4000 
~ :s; 

1-

ffi 

1-

(/) 

:::::> 

a::8 

wu 

8:::;:=: 

:::::>LU 

1- a: LU u LU ....\ u... 

~ (/) 0 :::::> ....\ 

:I: 0 fu ~ 0 < t;:; 

a: 

u 

a: 

~ g 

u 

Ci) 

~ ~ 

16.000 I 

THERMAl AlTERATION 

INDEX 

1 0 1.2 1 4 1 6 1 .B 2.0 2 2 2 4 

I I I I 

02 0.3 

VITRINITE REFlECTANCE 

IRol 

. . . . . . . . . . . 

. . . 

•• ! 

0.4 

. . . . 

. 

.. 

11 

CORE LABS 

. 

• SIDEWALL CORES 

• CUTTINGS 

. . . . . . . 

05 C PI 

TEMPERATURE 

MAXIMUM 

PYROlYSIS YIELD 

Ts2 I"CI 

0 4 0 B 1 2 1 6 2 0 2 4 2 B 3 2 3.6 400 420 440 

USGS USGS 

Figure 38.--Maturity profiles of organic matter as a function of depth in samples from the COST No. B-3 well. 

1000 

2000 (/) 

a: 

LU 

1-

::g 

~ 

:I: 

fu 

C> 

3000 

4000 

5000 
sources. The wide range and inconsistency in 

the stable-carbon-isotope ratios may indicate 

that the kerogen and extractable organic matter 

in the Tertiary secion have unrelated genetic 

origins, indicating that the extractable 

hydrocarbons were not derived by thermal 

processes (fig. 37). 

The TAI values range from 1.2 to 1.5., and 

the vitrinite-reflectance values span 0.26 to 

0. 35 percent. Thermally immature extractable 

organic matter and kerogen are also suggested by 

CPI ratios that range from 3.5 to 1.7 and 

temperatures of maximum pyrolysis yield (T52 ) 

that vary from 757 to 817°F (403 to 436°C) (fig. 

38). 

Upper and Lower Cretaceous 

The kerogens of the Upper and Lower 

Cretaceous intervals are composed predominantly 

of exinite and vitrinite. Much smaller amounts 

of alginite are present here relative to amounts 

in the overlying Tertiary sediments. The 

atomic-hydrogen to carbon ratio varies from 0.6 

to 0.8, which is characteristic of hydrogenpoor, humic (Type III) kerogens. Exceptions to 

this trend are those samples at approximately 

10,000 ft (3,048 m), 11,500 ft (3,505 m), and 

12,000 ft (3,658 m) that contain a slight 

enrichment in the hydrogen-rich type of 

kerogens. For the major part of the Cretaceous 

section, the relative kerogen abundance and 

classification show the presence of the Type-III 

kerogens; these are gas-prone and are not 

favorable for oil generation. This humic (Type 

III)-kerogen predominance is consistent with the 

thermal-pyrolysis average convertibility of 8.46 

(weight percent) for the total Cretaceous 

interval. For these predominantly humic (Type 

III) Cretaceous kerogens, the stable-carbonisotope ratio ranges from 23.5 to 27 permil and 

differs very little from the algal {Type I) 

kerogens of the overlying Tertiary (fig. 37). 

The Cretaceous section is characterized by 

a constant TAI of 1.5 and vitrinite-reflectance 

(R0 ) values that increase continuously from 0.32 

to 0.40 percent. The CPI ratio varies 

inconsistently from 0.9 to 2.5. The 

temperatures of maximum pyrolysis yield vary 

from 806 to 817°F (430 to 436°C), except for 

those samples at 8,700 ft (2,653 m) with a 

temperature of 790°F (421°C), at 9,700 ft (2,957 

m) with a temperatu!'e of 795°F (424°C) and at 

10,800 ft (3,292 m) with a temperature of 838°F 

(448°C). These thermal maturation parameters 

suggest that the organic matter present in the 

Cretaceous section has not yet reached 

sufficient thermal maturity to be capable of 

generating and expelling hydrocarbons (fig. 38). 

Upper Jurassic 

The Upper Jurassic sediments penetrated in 

the COST No. B-3 well have kerog"'ns that are 

predominantly exinite and vitrinite. These 

humic and woody kerogen types are very similar 

to the kerogens present in tl <?. overlying 

Cretaceous sediments. The atomic-hydrogen to 

carbon ratio for the Jurassic kero3ens averages 

0.11, which is consistent with a Type-III 

classification. Additional evidence for an 

interpretation of a predominantly hydrogen-poor 

type of kerogen is provided by the average 

thermal-pyrolysis-convertibility ratio of 

pyrolytic hydrocarbon to organic carbon of 6.05 

(weight percent). The wide range of the stablecarbon-isotope ratios, from 2.5 to 3.5 (permil), 

between the kerogen, saturated paraffins, 

aromatics, and total extractable organic matter, 

suggest that the extractable liquid hydrocarbons 

are not genetically related to the kerogens 

(fig. 37). 

Significant and consistent increases in the 

degree of thermal maturity are indicated by TAI 

values that vary from 1.5 at 12,750 ft (3,886 m) 

to 2.2 at 15,820 ft (4,822 m) ani vitrinitereflectance values that range from 0.39 to 0.55 

percent. Although the R0 values are less than 

the 0. 6 percent commonly cited as required for 

the onset of peak hydrocarbon generation, there 

is some reason to believe that the data reported 

are biased toward low values (Smith, 1979). For 

this reason, the other maturity in-licators are 

weighted more heavily in our interpretation. 

The CPI odd-even ratio and the te11perature of 

maximum pyrolysis yield varies from 0.69 to 1.46 

and from 806 to 838°F (430 to 448°C), 

respectively (table 3). Such consistent 

agreement between parameters probably indicates 

the onset of thermal maturity at depths below 

14,900 ft (4,542 m). 

Possible Effects of Mud Additives 

on Source-Rock Interpretation 

Figure 39 shows the saturated paraffinnaphthene hydrocarbon gas chromatograms for the 

major mud additives used during the drilling of 

the COST No. B-3 well. The normal aliphatic 

hydrocarbons extracted from the r:?w stock of 

Spersene (lignosulfonate), and barite (BaSo4) 

have similar gas-chromatogr~phic characteristics 

that suggest a common component. Both have a 

well-resolved aliphatic component ranging from 

n-c16 to n-c28 and having a m~ximum peak 

intensity at n-c18 , and a moderately well 

developed, unimodal unresolved complex 

mixture. The Spersene and barite have totalorganic-carbon (weight percent) values of 37.5 

102 
en 

z 

~ c:c 

Cl 

c:c 

0 

u 

c:c 

CARBON NUMBER 

10 12 14 16 18 20 22 24 26 28 30 32 34 36 

Spersene 

~-------------

Bante 

~~------

Bentomte 

TIME-TEMPERATURE 

CARBON NUMBER 

10 12 14 16 18 20 22 24 26 28 30 32 34 36 

CARBOXYMETHYLCELLULOSE 

P1pe Dope 

Hydrocarbon Standard 

Figure 39---Gas-chromatographic analyses of additives to the mud drilling 

system, COST No. B-3 well. 

and 0.36 respectively (table 7). The source of 

the normal alkane hydrocarbons in these 

additives is unknown; however, they are believed 

to be related to a petroleum-based substance, 

possibly a light-oil or diesel component, which 

may have been introduced during the mudadditive-preparation process either at the 

manufacturing stage or during the time the mud 

was mixed on the drilling platform. 

The saturated paraffin-naphthene gas 

chromatogram of the montmorillonitic bentonite 

(total organic carbon, o. 2 weight percent) is 

characterized by the domination of the resolved 

Table ].--Analytical data fo1' extroctabZe organic rrrztter in d1'iUing-rrrud 

additives used in the COST No. B-3 ~UeZZ 

[-- indicates no data) 

Total 

organic 

Additive carbon Aliphatic Aromatic NSO 

(weight (ppm) (ppm) (ppm) 

ercent 

Pipe dope-------------- 312,567 71,753 4,247 

Bentonite-------------- 0.2 4.4 2.8 103.9 

Carboxymethylcellulose- 33.5 148.3 69.1 237.9 

Spersene--------------- 37.5 11.4 1.9 209.5 

Barite----------------- 0.36 71.9 26.6 63.9 

aliphatics over a weakly developed unresolved 

envelope. The aliphatics range from n-c18 to nc28, with the longer chain n-c22 to n-c 27 

hydrocarbons as the dominant molecular 

species. Both casing-thread dope and the 

carboxymethylcellulose (CMC), which has a totalorganic-carbon content of 33.5 weight percent, 

have signatures that show the predominanc~ of a 

well-developed, unresolved, complex mixtu1·e but 

with very poorly developed, resolved, normal 

aliphatic components. The unresolved envelope 

of_ the pipe dope reaches its maximum at n-c29 , 

whereas the maximum is at n-c21 for th~ CMC 

additive. 

The well-cutting samples selected to be 

analyzed for the COST No. B-3 well source-rock 

profile were thoroughly hand washed and 

extraneous foreign particles were eliminated 

before the samples were analyzed. Excert for 

those specific intervals for which nonindigenous 

liquid hydrocarbons were discussed, the effect 

of the mud additives may be minimal on the basis 

of the relatively immature character of th~ c 15+ 

gas chromatograms, and the relatively consistent 

103 
levels of total organic carbon (fig. 39 and 

table 7). However, the n-c4/n-c 7 ratios would 

suggest, if the value of unity or below for the 

ratio is accepted as a fingerprint for dieselfuel contamination, that nonindigenous 

anthropogenic hydrocarbons might be present in 

the interval from 3,800 ft (1,158 m) to 8,200 ft 

(2,499 m). The possibility that the mud 

additives employed in the COST No. B-3 well may 

have played an influential role by partially 

masking the indigenous hydrocarbons should not 

be excluded in the interpretation of source-rock 

richness, quality, and maturation. However, 

their influence is believed to be minimal in the 

B-3 well. A possible solution to the problem of 

mud-additive effects on source-rock interpretation and evaluation would be to label each 

additive with a distinctive "tracer" that would 

allow a diagnostic signature to be detected 

whenever mud additives have not been completely 

removed in either well cuttings or sidewall 

cores. 

CONCLUSIONS AND IMPLICATIONS 

FOR PETROLEUM GENERATION 

The Tertiary section in the COST No. B-3 

well (3,800-6,040 ft; 1,158-1,841 m) has an 

above-average total-organic-carbon content (1. 5 

percent) and kerogens that are mainly composed 

of the hydrogen-rich (Type I), marine algal 

variety. Results of both optical and chemical 

measurements indicate that the Tertiary kerogens 

are thermally immature. The molecular 

compositions and boiling-point ranges of the 

saturated c 15+ liquid paraffin-naphthene 

hydrocarbons also are consistent with thermally 

immature extractable organic matter. The 

shallow gas occurrence at about 4,000 ft (1,219 

m) is predominantly methane and has a relatively 

low percent gas wetness; it is not believed to 

be of thermogenic origin. 

The Upper Cretaceous section down to a 

depth of 7,500 ft (2,286 m) may have been 

affected by mud additives. Below 7,500 ft 

(2, 286 m), the effects of mud additives do not 

appear to be significant factors in influencing 

source-rock richness or maturity interpretations. In contrast with the overlying 

Tertiary section which contains predominantly 

hydrogen-rich kerogens, the Upper and Lower 

Cretaceous interval from 6,040 to 12,400 ft 

(1,841 to 3, 780 m) contains hydrogen-lean 

kerogens that are classified primarily as 

exinite and vitrinite (Type III). Th~ molecular 

compositions of the saturated paraffin-naphthene 

hydrocarbon mixtures are unlike the composition 

of petroleum, and the pyrolysis characteristics 

also indicate that the Cretaceous section is 

thermally immature. The very low total gas 

concentrations, coupled with the low values for 

optical-maturity indicators, suggest that the 

temperatures required to initiate the petroleumhydrocarbon-formation processes hava. been of 

sufficient intensity or duration to have 

generated or expelled liquid and (or) gaseous 

hydrocarbons from any potential sour~e rocks in 

the Cretaceous section. 

The Upper Jurassic interval (12,400-15,820 

ft; 3, 780-4,822 m) penetrated in the B-3 well 

has total organic-richness characteristics that 

indicate moderate to good source-rock 

potential. The kerogens are composed 

predominantly of the gas-prone (Type III) 

exinite and vitrinite varieties. The c 15+ 

liquid-hydrocarbon mixtures show an increasing 

resemblance to petroleum below 14,9011 ft (4,542 

m), as indicated by a systematic decra.ase in the 

magnitude of the unresolved envelope and a 

relative increase in the concentration of the 

lower molecular weight, resolved, saturated 

paraffin-naphthenes. A significant increase in 

the concentration of c 1 to c 4 light h;drocarbons 

and in the gas-wetness percentage t'lso occurs 

below 14,300 ft (4,359 m), indic'l'ting that 

thermal maturation of the organic matter has 

started. Optical and other chemical-maturity 

indicators are consistent w~th this 

interpretation. Although conditione- favorable 

for petroleum generation are reached in the 

Upper Jurassic section at depths l:elow about 

15,000 ft (4,572 m) in the COST No. B-3 well, 

the organic matter is not of the type that 

yields significant amounts of liquid 

hydrocarbons (oil). Although the concentrations 

of organic matter are adequate for hydrocarbon 

generation, the types of organic matter present 

indicate that this section is more likely . to 

generate gas than oil. 

104 
GEOPHYSICAL STUDIES 

David J. Taylor and Robert c. Anderson 

SYNTHETIC SEISMOGRAM 

Synthetic seismic traces were computed using 

the interval-transit-time log and density log 

from the COST No. B-3 well. Velocity 

information from the interval-transit-time log 

was also used to generate cross-plots of depth 

versus two-way travel time and of average and 

RMS velocity versus two-way travel time. 

Data for these computations were obtained 

directly from the digital well-log tape recorded 

at the COST No. B-3 well site during the 

logging. A minor amount of editing was 

performed on the interval-transit-time curve 

before the synthetic-seismogram traces were 

generated. 

The velocity and density curves were 

converted to a linear time scale through 

integration of the interval-transit-time welllog curve. The product of the velocity curve 

and the density curve produces the acousticimpedance trace, from which the reflectioncoefficient trace is computed according to: 

r(t) • r(t+1)V(t+1) - r(t)V(t) 

r(t+1)V(t-1) + r(t)V(t} ' 

where r(t) is the reflection coefficient at time 

t, V is velocity, r is density, and the index 

"t" denotes the two-way-time position of rock 

layers above and below the reflecting horizon 

with respect to sea level. The computation of 

r(t) for each rock-layer interface yields a 

reflection-coefficient trace, consisting of a 

time series of sharp pulses. The magnitude 

represents the strength of the reflecting 

horizon, and the time index is its position in 

two-way normal-incidence travel time. The sign 

of the reflection coefficient represents the 

polarity of the rock layers, which is an 

indication of whether the seismic wave is 

leaving a rock layer that is acoustically harder 

or softer than the one it is entering. This 

method for generating synthetic seismograms 

ignores transmission losses, absorption losses, 

and any effects of multiples. 

To complete the synthetic seismogram, an 

arbitrary wave pulse, or wavelet, is convolved 

with the reflection-coefficient series to match 

the wave form and frequency characteristics of 

the seismic data. The resulting trace can then 

be used to correlate geologic formatjons to 

their corresponding expression in seismic field 

data. For this study, the waveforms applied 

were symmetric bandpass wavelets with differentfrequency passbands. This approach show~ which 

seismic frequencies are required to be present 

in the field data in order to allow detection of 

a particular geologic formation. 

A set of synthetic seismograms ge:'lerated 

using the product of velocity and density 

(acoustic impedance), and with varying b~ndpass 

filters applied, is shown in figure 40. 

Bandpass-filter cutoffs are listed aboy~ each 

seismogram group. Polarity of these seis~ograms 

is conventional: a positive reflection 

amplitude represents a transition of lower to 

higher acoustic impendance between rock 

layers. Noise or multiple reflections w~re not 

added to these seismograms. 

In addition to this group of sy~thetic 

seismograms, additional sets of synthetics were 

computed using. the velocity· data alone a"'ld then 

the density data alone. These seism~grams, 

using the same bandpass filters that were 

applied to the seismograms in figure 40 are 

shown in figures 41 and 42. These seis11ograms 

were constructed to show the individual 

contributions of velocity and density to the 

seismic trace. The amplitude of the traces in 

these figures were scaled to a common lev,.~l and, 

therefore, do not accurately represent the true 

relative amplitude strength of each trace. 

However, the seismograms do show where the 

important acoustic boundaries are located and 

which acoustic property is contributing to the 

total seismogram. 

The best correlation of the sy:'lthetic 

seismogram (generated from the COST No. B-3 

well) to field data occurs using the 8-35 Hz, 

filtered, synthetic seismogram developed from 

the velocity-density product, and having the 

polarity inverted. This compensation for 

polarity is common in seismic interpretation, as 

it is possible for polarity to be inverted in 

the phases of recording or processing seismic 

data. Figure 43 shows the 8-35 Hz sy"'thetic 

seismogram selected for correlation to th~ field 

data, discussed in the next section, along with 

105 
Cl) 

0 

z 

0 

u 

w 

V) 

~ 

u.i 

~ 

1.5 

2.0 

Cl) 

0 

z 

0 

u 

w 

Cl) 

~ 

1.5 

2.0 

REF. 

COEF, 8-25 8-30 8-35 8-40 8-45 8-50 8-55 8-60 

I .. @; i . '· iiii•... ':'' .... (il[i .... ii!!i Wi! 

-.1111100\·~00\ ~ Jilil. i ~~ i~ 1~~·~1· .~11· .ii·~· ~~--?»» ,. ,,,,, ,,.,,, ,,,,, ,,,,, ,,,,, ,, 1,1,1,1,1 

.. I"", .· .. ,T.' ...... ·~ff .... ·.· i~.·.·.·~.~.·~·.·.·.·· ~ .. ~~~~~; ... ~~·~~l.~~.~~ ..... ~mr; ....... ~ .... 1 ........ .. l • il il iillL ill[ .l llill @( ""I 

Iii HI!! . ._ -. ~ 2.5 w 2.5 

~ _, \w\ 'tfffr ~ ·~ ·~ ·:·:::·: w 

> c( 

a:: 

~ 

> c( 

~ 

0 

~ 

~ 

_, 

w 

> c( 

a:: 

~ 

> c( 

~ 

~ 3.0 6 3.0 

~ 

3.5 

Figure 40.--Reflection-coefficient trace (at the 

far left), constructed from the COST 

No. B-3 interval-transit-time and 

density-log curves, and several 

bandpass-filtered versions of the 

reflection-coefficient trace. The 

upper and lower frequencies of the 

bandpass filters are listed above 

each group. Polarity for these 

synthetic seismograms is 

conventional: a positive reflection 

(deflection to the right) represents 

the transition from a layer with 

lower acoustic impedance to a deeper 

layer with higher acoustic 

impedance. 

~ 

3.5 

Figure 41.--Reflection-coefficient trace and 

filtered versions constructed from 

the COST No. B-3 well usin~ only the 

velocity information from the 

interval-transit-time log. Filter 

cutoffs and polarity are the same as 

those used in figure 40. The upper 

and lower frequencies of the 

bandpass filters are liRted above 

each group. Polarity for these 

synthetic seismograms is 

conventional: a positive reflection 

(deflection to the right) represents 

the transition from a layer with 

lower acoustic impedance to a deeper 

layer with higher acoustic 

impedance. 

Figure 42.--Reflection-coefficient trace and filtered versions constructed using only densityC> 

information. Filter cutoffs and polarity are the same as in figure 40. Th~ upper 

and lower frequencies of the bandpass filters are listed above each group. Polarity 

for these synthetic seismograms is conventional: a positive reflection (deflection 

to the right) represents the transition from a layer with lower acoustic im~edance 

to a deeper layer with higher acoustic impedance. 

106 
Figure 43.--Synthetic seismograms constructedC> 

from velocity and density data from 

the COST No. B-3 well. These 

seismograms have been filtered using 

an 8-35 Hz bandpass filter and 

reversed in polarity to match the 

seismic field data shown in figure 

46. From the left, the first group 

of traces represents a synthetic 

trace constructed from velocity data 

alone , and the second group is a 

synthetic trace constructed using 

density data alone. The right-most 

group is the synthetic trace 

constructed from the velocitydensity product, or acoustic 

impedance. 

Cl) 

0 

z 

0 

u 

w 

Cl) 

z 

2.0 

-_ 2.5 w 

:E 

;:::: 

.... 

w 

> 

< 0::: 

.... 

> 

< 

~ 6 3.0 

~ 1-

3.5 

REF. 

COEF, 8-25 8-30 8-35 8-40 8-45 8-50 8-55 8-60 

rrrrr 

,,, 

IHH 

fiiii 

rrccc 

rrrrr 

107 

en 

c 

z 

0 

u 

w 

en 

z 

w 

1.5 

~ 2.5 

~ 

....J 

w 

> 

<( 

0:: 

~ 

> 

<( 

~ I 

0 

~ 3.,0 ~ 

3.5 

tJEL. ·OENSa tJEL. 

ONLY ONLY OENSa 
VELOCITY, IN KILOMETERS PER SECOND 

1.5 2.0 2.5 3.0 

1.5 

CJ) 

0 

z 

0 0 2.0 

w 

CJ) 

~ 

uj 

::?i 

~ 

...J 

w 

> 2.5 <t: 

a: 

~ 

~ 

<t: 

3: 

0 

3: 

~ 

3.0 

3.5 

~ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ VRMS 

\ 

Vaverage ', 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

Figure 44.--Two-way travel time from sea-level 

datum as a function of average 

velocity and root-mean-square (RMS) 

velocity. 

the velocity-only and density-only synthetic 

seismograms. All of these traces in this figure 

have been reversed in polarity. 

Velocity information useful to seismic-data 

interpretation can also be extracted from welllog data. Average velocity versus two-way 

travel time, shown in figure 44, can be used to 

convert the reflection time of a formation from 

seismic field data to a function of depth below 

the surface. Average velocities can also be 

used for migration of seismic data in areas of 

geologic structure and faulting. 

Root-mean-square (RMS) velocity, shown in the 

same figure, can be used to determine the proper 

correction for normal-moveout in the stacking of 

offset seismic traces. RMS velocities, however, 

are only usable in areas where changes in 

lateral velocity are not great. Finally, the 

relationship between two-way travel time and 

depth is shown in figure 45. Major age 

boundaries plotted in the figure are from Amato 

and Simonis (1979). 

TWO-WAY TRAVEL TIME, IN SECONDS 

2 3 4 

Miocene 

5,000 

Coniacian 

~ Qj 

_j Turonian 0. 1- 0. w w Cenomanian :::> w > u. w 

...J ~ c( Albian _j w w (/) rll > 

~3 Aptian ::l w 0 CD 10,000 ~ ...J (.) 

w Berremian ., w ID "§ (/) 

I Hauterivian- (.) ~ 1-

Q. Valanginian Qj 0 

...J w ~ w 0 0 ID Berriasian ...J 

I 

1-

Q. 

w 

0 

Tithonian 

4 ~---"'"1 

Kimmeridgian 15,000 

5L----~~--------------__...J 

Figure 45.--Two-way travel time below sea-level 

datum as a function of depth. Ages 

are from Amato and Simor.is (1979). 

SEISMIC DATA - LINE 25 

In order to tie the COST No. B-3 well into 

the grid of regional seismic data, Seismic Line 

25 was used. Line 25 is a 48-fold, 

common-depth-point (CDP), seismf.c-reflection 

line and, at this date, is the closest USGS line 

to the COST No. B-3 well. The COST No. B-3 well 

is roughly 7 mi (11 km) along strike and 

northeast of shotpoint number 2885 of Line 25. 

Line 25 was acquired for the USGS by 

Geophysical Services, Inc. (GSI), during the 

summer of 1978. Following the acquisition of 

the seismic data, GSI performed data processing 

of the raw field data to a final stacked 

section. This processing included 

demultiplexing, velocity analysis every 2 mi (3 

km), normal-movement (NMO) corrections, 48-fold 

horizontal stacking, time-variant predictive 

deconvolution for removal of multiples, bandpass 

filtering, and trace-amplitude equalization. 

Figure 46 is a portion of Line 25 

surrounding the projected tie with the COST No. 

B-3 well. Evident from this figure are several 

good correlations between the synthetic 

seismogram and the seismic data. Table 8 lists 

several of the better correlations between the 

synthetic seismogram and the seismic data, along 

with age dates taken from Amato and Simonis 

108 
WATER DEPTH, m 

SHOT POINT 2850 

I

CCIST B-3 WELL 

' ·;I I.JTHET ,,= SE I o;lli]I~PH'l 

> 

827 

2900 2950 

I 

i:l ' I;• 'il,i' I ·'! 1:, 1 1! i V1

' il 

0.5 ii: ' : I i!· ::~:i!- ; i I; 

! i I, I i!' I i !:; .. !'! i; j: :; • II: I! I i' :i i 1:! :1 '·' 

,,:: : '';' '·! 1,, I!'' I jl; Ill 'I i[ ! I:: !' 

ti Iii,; I I :II I i :':;:I I I ; I ' ii ! ' i! I !" !I 

!:JiiW! I ''il !II, I', 1:], ': 

1.0 

~ 

~~lt1 ! I il ,:11 

'i 

:I 

I 

: 

' 

ii' 

I! 

;; 

1296 

3000 

i: ii I''[ 1 

,, ' 

i:i s: I.! ~~ ,i II :: :, 1: 

; i; !'I :1: ,; 

i 

iii!: ill 

I lj 

!i !! I' I .1 IIi I r ,, ;r: . 

!i I. :r::: 

I i I 

en 

0 

z 

0 

() 

w 

en 

:~( 

1 11 

!, I', j,i ,i 1! I' 

~ 

w 1.5 

~ 

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...J 

w 

> <( 

cc 

~ 

>- 2.0 

<( 

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2.5 

It', 

' 

:• 

'" ~ 

I, 

-.mtl 30 11. 

i!:.~lr,l .. ~~()i;'(~[ .~ 

~~~~~. ·, /_1) ' I JK = 

... , 

3.5 I 

i '!; 

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·~ .. ; ... 

·(~:~. ";:;: "' ;;, 

:r f'(·: ,,','::: .cr 

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,., 

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:.~ ~ .·· ~~. i ,, :,:, 

', I I 

1:1 I I. 

![I :':1 ! II: i 1: 'i,! 

I ~~I il j 1 i 

I 

3050 

i I 

: I ! i I ~ 

'i I 

I' 

~ i 

• I I! i 

'! iii! II'; 

!I 

II 

! ,i I I I 

Figure 46.--A portion of USGS CDP reflection Line 25 and the bandpass-filtered (8-35 Hz), 

reflection-coefficient trace projected along strike from the COST No. B-3 well. The 

synthetic seismogram has been time shifted to account for dip between the well and 

seinic line and has been reversed in polarity to match the polarity of the seismic 

field data. This synthetic seismogram is also shown in figure 43. 

(1979). Figure 47 shows these age correlations interval-velocity log of the COST No. B-3 

and lithologic descriptions plotted against the well. 

109 
5,000 

li:i 

w 

u. 

~ 

:X: 

li: 

w 

0 

10,000 

15,000 

.5 

.0 

.5 

3 .0 

3 .5 

4. o4. 5 

INTERVAL VELOCITY, IN KILOMETERS PER SECOND 

0 2 4 6 I 

Miocene !:1 Calc 

L ~ mudstone 

Oligocene ~ !l 

u l... 

= J V Calc L 

Eocene 

~ claystone 

& shale 

1 rlayst sh, slst L Maest "--- ,___ 

Campanian c~ 

r V Calc 

Santonian 

~ silty 

U) mudstone, ::I 

g ~ minor 0 

Coniacian ~ ~j:, sh, Is, dol 

u 

a. 

Q; ~~ a. It- Turonian :::l 

~ 

' Cenomanian lntrbd ss/sh, 

minor Is, dol 

Shale & Albian 1r mudstone, 

~ Aptian U) \_ minor ss, Is 

::I 

0 

Q) 

Barremian lC 0 

~ - lntrbd 

0 ~ ~ ss, sh, Is, Hauterivian Q; 

~ "" t- minor slst 0 

...J 

Berriasian 

intrlm 

~ sh & ss, 

slst/ls 

Tithonian ss & sh, Is 

0 ~ lnterlaminated iii 

Kimmeridgian U) 

~ sh & Is, ~ 

~ ~~ thin ss 

i ~ 

~ 

1.5 

2.0 

(/) 

0 

z 

0 

u 

w 

(/) 

~ 

ui 2.5 ~ 

3.0 

3 .5 

i= 

...J 

w 

> <( 

a: 

I-

>- <( 

~ 

6 

~ 

Figure 47 .--Interval velocity as a function of 

depth below sea level and two-way 

travel time. The correlations and 

lithology are from Amato and Simonis 

(1979). 

Tabl.e 8.--CoT'T'el.ations between the COST No. B-3 

bJel.l. and USGS Seismic Line 25 

Two-way 

travel time Depth 

( s) Feet Meters 

1. 745 

1.805 

1.900 

2.090 

2.300 

2.700 

3.160 

3.405 

3.600 

4,856 

5,052 

5,348 

6,070 

6,923 

8,694 

11,320 

12,960 

14,534 

1,480 

1, 540 

1,630 

1,850 

2,110 

2,650 

3,450 

3,950 

4,430 

1oata from Amato and Simonis, 1979. 

Within late Oligocene. 

Within late rocene. 

Within late Eocene. 

Late Cretacec-us boundary. 

Santonian-Coriacian boundary. 

Early Cretace-ous boundary. 

Within Berri~>.sian. 

Within Jurase-ic-Tithonian. 

Within Jurassic-Kimmeridgian. 

110 
SEISMIC STRATIGRAPHY IN THE VICINITY 

OF THE COST NO. B-3 WELL 

John s. Schlee and John A. Grow 

INTRODUCTION 

The COST No. B-3 well is situated in the 

vicinity of a grid of multichannel seismicreflection profiles and shallower drill holes 

(fig. 48); the holes have been described by 

Scholle (1977), Poag (1978, 1979), Hathaway and 

others (1976, 1979), and Amato and Simonis 

(1979). The seismic-reflection profiles have 

been studied by Grow and others (1979), Klitgord 

and Behrendt (1979), Schlee and others (1976, 

1979), and Folger and others (1979). 

The purpose of this paper is to describe 

the seismic stratigraphy adjacent to the COST 

No. B-3 well and to tie these observations to 

the lithology encountered in this and other 

nearby wells. 

SEISMIC STRATIGRAPHY 

As can be seen by the age and arrangement 

of key reflectors in figures 49 and 50, the 

outer shelf and slope were built up during the 

Cretaceous and Jurassic. During the Cenozoic, 

intervals of progradation alternated with 

intervals of erosional retreat, and so the 

shelf-slope break, at present, is 12 mi (20 km) 

landward of where it was in the Early 

Cretaceous. Beneath the shelf, where the oldest 

reflectors can be distinguished, subsidence 

occurred mainly during the Jurassic and Late 

Triassic. Reflectors inferred to be Late 

Cretaceous and Tertiary are exposed along the 

present Continental Slope (Weed and others, 

1974), and a large sedimentary wedge of Miocene 

and younger age underlies the Continental 

Rise. Construction of the rise wedge has been 

discontinuous, as shown by the presence of 

apparent unconformities within it (fig. SO). 

Differential subsidence flanking the Early 

Cretaceous shelf edge (fig. 51) has created a 

broad slope "anticline" similar to that 

described by Lancelot and Seibold (1978) and Von 

Rad and Einsele (1980) in the Aaiun basin off 

West Africa. 

111 

REFLECTOR BOUNDARIES 

The character of the key reflectors (figs. 

49, 50, 52, and 53) changes from the shelf to 

the rise. In a study of reflectors beneath the 

shelf, Schlee (in press) showed that certain 

ones are associated with unconformities, and 

these have been used to delineate th€ major 

seismic-stratigraphic units. By tracing 

reflectors from onshore well and the COST No. B2 well, the unconformities are enferred to occur 

in the late Oligocene, at the base of the 

Tertiary, in the Coniacian and the Ceno'tlanian, 

and at the base of the Albian. Poag (this 

volume) has detected hiatuses on the Continental 

Shelf in the COST No. B-2 well at the base of 

the Quaternary, within the middle Mioce'le, at 

the base of the Miocene, between th~ late 

Oligocene and late Eocene, within the early 

Eocene, at the base of the Tertiary, betw~en the 

Maestrichtian and Campanian, betwee, the 

Coniacian and Turonian, and between the T·tronian 

and Cenomanian. Below the Cenomanian, faunas 

are sparse and detection of erosional breaks is 

difficult. In the COST No. B-3 well, on the 

Continental Slope, Poag finds disconformities 

between the middle and lower Miocene, tl?. late 

Oligocene and late Eocene, the early Eocene and 

Maestrichtian, the Coniacian and early Turonian, 

the Turonian and Cenomanian, and the Barremian 

and Hauterivian. Some of the breal:s, as 

detected seismically and dated by correlation 

with other wells, agree with Poag's studies and 

also with the relative-sea-level curve (fig. 50) 

of Vail and others (1977). The base of the 

Cretaceous sequence is in apparently conformable 

contact with Jurassic strata beneath the: Outer 

Continental Shelf, and the conta~t is 

unconformable toward the inner part. 

Under the Continental Rise (fig. 49), a few 

of the same reflectors are present: the 

Oligocene (Au), Tertiary-Cretaceous, Coniacian, 

and Cenomanian, reflectors are present, although 

all but the Au horizon are conformable. Also 

present is Horizon (Tucholke and others, 
72°00 ~------------~~~----------------------------------------~--~--------------· 

_.'/,o 

i .. r" 

···· ...... ·····• 

.. 

/ ... ············· 

·. ·.:·.·:-':. 

7YOO 

0 cosr No. 

B-2 

. ·· -·· 

0 

0 

... ····· 

N 

10 

.. ···~ 

···--;;] 

.... : )._, _____ .. / / ··. 

____ ........ ..:_.::~! 

•• zoofl' ./ 

10 

.~·-·· ..... :-

20 

... ,oo 

_ _, ................. ··· 

0, ......... .... 

30 KM 

20 Ml 

Figure 48.--Index map of seismic lines and drill holes in the vicinity of the 

COST No. B-3 well. Inset locates area within the Mid-Atlantic 

Outer Continental Shelf. 

112 

~·· ··:.: 
(/) 

NW SP 2600 SE 

3400 

o~~~~~~~~~~~~wu~~~~~~~~~o 

~~7~C:~~-~ __ _ POINTY 

4 

16 

8 

~ ~ 

w 0 

~IO~~~~~~~~--=-~~L~IN~E~3~4~~~~~~~~ ~ 

~ 0 ~::::::::::==~~=-o;;:t-r:;-::.,..--;ii<:PT.r...-1---------,- 0 ~ ~ (/) 

~ g 

4 

8 

0 IOKM 

0 6MI 

I I I 

CARBONATE 

PLATFORM COMPLEX 

16 

32 

:I: 

..... 

10-L-------------------~----jFigure 49.--Annotated depth section of a portion 

of USGS Seismic Line 25 between 

shotpoints 2600 and 3400. On the 

interpretation below the photo, 

reflectors beneath the shelf and 

upper slope probably approximate 

disconformities. Nearby well have 

been projected onto the depth 

section. Ages of sediments 

encountered in the shallow 

penetration holes are marked with a 

letter designation: P, Pleistocene; 

M, Miocene; E, Eocene. For the COST 

No. B-3 well, the intervals of upper 

and lower slope conditions, as 

detected by Poag (this volume), are 

indicated by vertical bars to the 

right of the COST No. B-3 well 

projection line; the one interval of 

nonmarine conditions is indicated by 

a vertical bar to the left of the 

well. An "R" near the COST No. B-3 

well indicates a relative 

regression, and the wavy lines 

signify the positions of 

disconformities detected by Poag 

(this volume). The broad outline of 

the carbonate platform-reef complex 

is shaded in the interpretation 

below the photo. 

1979), inferred to be the top of Neocomian 

limestones drilled in DSDP Hole 105 (400 mi (650 

km) southeast of the area). Two conspicuous 

unconformities are evident within the 

Continental Rise wedge (fig. 53) above the Au 

reflector. 

On the seismic sections parallel to the 

slope (figs. 52 and 53), some of t~e same 

reflectors are evident within rocks of probable 

Cretaceous and Tertiary age. Horizon , so 

evident on Line 35 seaward of the carbonateplatform front (fig. 51), does not carry through 

to Line 34 (fig. 49), landward of the front. 

Instead, at about the same stratigraphic level, 

a horizon inferred to be near the top of the 

Hauterivian is evident (fig. 51; and I.ine 34, 

fig. 52). 

Key reflectors (figs. 52 and 53) within the 

upper Continental Rise are mainly conformable, 

although Au has a relief of several hundred 

meters on Line 35 (fig. 53). However, older 

reflectors are flat and are distinguished by 

their continuity and moderate tc high 

amplitude. Further, they mark changes in the 

seismic character between adjacent groups of 

less prominent reflectors. 

COREHOLE STRATIGRAPHY 

Projection of lithology and ages of rocks 

drilled in nearby holes onto Line 25 (fig. 49) 

reveals the conditions under which the 

Continental Margin formed over the p~st 160 

million years (since Middle Jurassic). The COST 

No. B-3 well penetrated the upper 3 mi (4.8 km) 

of the upper slope (fig. 49); Upper JurassicLower Cretaceous rocks were deposited in a 

marine-shelf to nonmarine mileau, probably 

behind a reef complex (Poag, this volume; 

Valentine, this volume; Bebout and Lachance, 

1979). Several regressions and transgressions 

affected the Cretaceous shelf, giving rise to 

hiatuses at the times already indicated. A 

major transgression occurred during the Late 

Cretaceous and the Eocene when "upper slope" and 

"lower slope" conditions prevailed. Regressions 

preceded development of the Tertiary hiatuses 

(fig. 49), and the site became part of the outer 

shelf in late Miocene, before returning to a 

slope milieu in the Quaternary (Poag, this 

volume). 

Strong acoustic reflectors on Line 25 

commonly are associated with disconformities 

(fig. 49) detected in the COST No. B-3 well 

(Poag, this volume). Examples are the late 

Oligocene horizon, the base of the Tertiary, the 

Cenomanian horizon, and the BarremianHauterivian horizon. The strong reflector near 

the base of the Tertiary could be caus~d by a 

sequence of deep-water transgressive li111estones 

encountered in both the COST No. B-2 (f'~holle, 

1977) and the COST No. B-3 wells (Adinolphi and 

Jacobson, 1979, pl. 1). A strong r~flector 

coinciding with the Hauterivian-Barremiar hiatus 

(fig. 49) appears to be associated with a 

regression and the landward shift of the 

carbonate-platform complex. Though structurally 

warped, the reflector appears to be shir~led in 

a discontinuous manner toward the northwest 

113 
Figure 50. --A tabulation of the major reflectors distinguished on USGS Seismic Lines 25, 34, and 

35; they are keyed to the relative-sea-level curve of Vail and others (1977). Also 

included is a generalized lithologic log of the COST No. B-3 well showing the 

disconformities recognized by Poag (this volume) as wavy lines. Reflector 

abbreviations are CALLOV (Callovian--Poag, this volume), HAUT (Hauterivian), ALB. 

(near base of Albian), CENO, (Cenomanian), CO~. (Coniacian), OLIGO. (within the 

Oligocene), PLEIST. (near the base of the Pleistocene), and UNC (unconformity). 

(point Y, fig. 49); this arrangement and the 

presence of a limestone unit at the top of the 

Hauterivian in the COST No. B-3 well suggest 

platform retreat during this part of the 

Cretaceous. 

In a stepwise manner, the shallowpenetration holes (AMCOR 6021, ASP 14, ASP 15, 

and DSDP 108} date major units (figs. 48 and 

49) • Light-gray, siliceous, calcareous chalks 

of middle Eocene age were cored in DSDP hole 108 

(Shipboard Scientific Party, 1972) and in ASP 

hole 15 (Poag, 1978). The rocks contain 

radiolarians, calcareous nannoplankton, and 

planktic Foraminifera, all suggestive of bathyal 

conditions of deposition (Poag, 1978), just as 

indicated in the COST No. B-3 well for the 

Eocene sequence (Poag, this volume; Valentine, 

this volume). A thin sequence (30 ft, 10 m) of 

Oligocene age was encountered in the ASP 15 

hole, unconformable with both the Eocene below 

and the Miocene above. 

Most of the upper slope in this area is 

underlain by a shallowly buried progradational 

sediment wedge, as seen in seismic records. The 

wedge is more than 778 ft (237 m) thick in ASP 

14 and is of Miocene age; Poag (197f) noted that 

it consists of dark-olive-gray glauconitic sand 

and silty clay deposited under outer shelf 

conditions. In ASP 15, the sequ€nce is much 

thinner (148 ft; 45 m), and a low,~r to middle 

Miocene section was recovered (Poag, this 

volume). 

AMCOR hole 6021 (7 mi; 11 km northeast of 

the profile) drilled through 1,000 ft (305 m) of 

dark-gray, silty clay of Pleistocene age 

(Hathaway and others, 1976). As can be seen 

from the profile (fig. 49), a thick wedge of 

Pleistocene sediment underlies the shelf edge, 

thinning in both a seaward and landward 

direction. In both ASP holes, a thin cover of 

Pleistocene sediment unconformably overlies 

114 
USGS LINE 25 - BALTIMORE CANYON TROUGH 

COST B-3 

35 NW SE SHOT POINT :2000 2200 2400 2600 3200 3400 3 600 3800 

WELL LINE 34 

2800 l 3oo0 

o-rPLfi~==~~~~~~~~~~~==~ --LL-i-- ~Jm~~~--~~~~~~o 

aJ 

~ 5 

lId 

9 

il 

~ 10 

:I 

ln. 

lol 

0 I S 

0 

KILOMETERS 

10 20 

STATUTE M ILES 

OCEA NIC 18ASEMENT 

I EA RlY JURASSIC AGE ?) 

30 40 

/f- REFRACTION VElOCITY · - IN KMISEC. 

50 

lId 

10 ~ 

:I 

I- 50 n. 

~ 

Figure S1.--An interpretation of the depth profile for USGS Seismic Line 2S between shotpoints 

1900 and. 3900. Major features are the carbonate bank-reef buildup under the margin 

and extensions of continental and oce~nic crust. Age assignments for the major 

reflectors are shown in figure SO. Dotted rectangle shows the area of figure 49. 

Approximate position of faults shown by heavy lines with arrows indicating direction 

of fault movement. 

sw 

800 

NE 

1600 

Figure S2.--Time section of USGS Seismic Line 34 between shotpoints 800 and 1600. Major 

reflectors are indicated on a small segment of the profile. Age designations of these 

reflectors are shown on figure SO. 

115 
sw NE 

500 LINE 35 1300 

2 2 

(f) 

0 

z 

0 

u 

w 

(f) 4 4 

w 

~ 

1-

_j 

w 6 ~ 6 

0::: 

1-

~ I 

~8 8 

1-

Figure 53.--Time section of USGS Seismic Line 35 between shotpoints 500 and 1300. Major 

reflectors beneath the Continental Rise are indicated on a small segment of the 

profile. Age designations of these reflectors are shown in figure SO. 

sediment of middle Miocene age (Poag, this 

volume); the cover is thickest (100-200 ft; 30-

60 m) in ASP 14. 

INTERPRETATION OF SEISMIC PROFILES 

The change in seismic character of broad 

groups of reflectors from the shelf to the rise 

(fig. 49) gives some insight into the 

constructional history of the margin since the 

Jurassic. Beneath the shelf, reflectors that 

were inferred to be Jurassic and older are 

discontinuous and moderate to low in seismic 

amplitude. Utilizing the criteria of Sangree 

and Widmier (1977, 1979) the sequence is 

inferred to be a nonmarine or marginal-marine 

section of clastic rocks. The upper part of the 

section was drilled in the COST No. B-2 well and 

proved to be a sequence of fine- to mediumgrained sandstone, siltstone, and shale with 

coal seams. Under the slope, some of the 

reflectors of equivalent age are more continuous 

and higher in amplitude in the upper part of the 

group; to the southeast they merge with the main 

carbonate mass. These more continuous 

reflectors probably represent limestone formed 

in shallow-marine environments behind the 

platform front. Seaward of the main carbonate 

mass, high-amplitude, continuous and 

discontinuous reflectors older than Horizon 

(fig. 49) may be a slope facies of fore-reef 

breccias and pelagic limestones, as postulated 

116 

by Arthur and Schlanger (1979). Still farther 

seaward (fig. 49), below Horizon , reflectors 

are discontinuous and a few high-amplitude ones 

are scattered among low- and moderate-amplitude 

reflectors. They are most likely the 

continuation of the slope or flank facies seen 

at the right of Line 25 (fig. 49). 

The seaward change in acoustic character 

for reflectors inferred to be of Cretaceous age 

is less pronounced than that seen in the thick, 

Jurassic sequences of shale (weak amplitude) 

interbedded with scattered sequences of 

limestone (high continuity, moderate amplitude) 

which accumulated in a slope environment. 

Beneath the rise (fig. 53), where inferred 

Tertiary reflectors are semicontinuous and of 

moderate intensity, their arrangement is 

dominated by major hiatuses. As seen in figure 

53; the seismic character of this group of 

reflectors probably indicates onlapping-fill and 

slope-front-fill facies (Sangree and Widmier, 

1977, 1979) of a lower slope environment 

covering broad, channel-like erosion surfaces 

(Au) whose axes trend normal to the present 

slope. The younger groups of reflectors are 

part of the rise wedge built of silt and clay 

obtained through the periodic cutback of the 

slope during the Cenozoic. Proximal sources 

upslope and on the shelf supplied the sediment 

from which the wedge was constructed. 
DEEP STRUCTURE AND EVOLUTION OF 

THE BALTIMORE CANYON TROUGH 

IN THE VICINITY OF THE COST NO. B-3 WELL 

John A. Grow 

INTRODUCTION 

The recent availability of both 

multichannel seismic-reflection data and deep 

drilling information from the Outer Continental 

Shelf off New Jersey has begun to answer many 

important geologic questions concerning the deep 

structure and evolution of the Atlantic 

Continental Margin since North America and 

Africa rifted apart in Late Triassic or Early 

Jurassic time. Although earlier refraction 

studies had detected 16,500-ft/s (5-km/s) 

refractors at depths of 1.2-3.7 mi (2-6 km) 

beneath the Outer Continental Shelf that were 

inferred to be basement (Drake and others, 

1959), the first multichannel lines measured as 

much as 7.5 mi (12 km) of sedimentary section 

(Mattick and others, 1974; Schlee and others, 

1976) and supported interpretations of the highvelocity horizons as carbonate-bank or reef 

deposits of Late Jurassic and Early Cretaceous 

age (Emery and Uchupi, 1972; Sheridan, 1974; 

Sheridan and others, 1979). The COST No. B-2 

well was the first deep stratigraphic well on 

the u.s. Atlantic Outer Continental Shelf (fig. 

54) ; it sampled 3 mi (4.8 km) of Upper Jurassic 

to Pleistocene shallow-water-marine and 

nonmarine sediments (Smith and others, 1976; 

Scholle, 1977; Poag, 1979; Grow ,Mattick, and 

Schlee, 1979). More recent multichannel depth 

sections across the Outer Continental Shelf and 

Slope (Grow, Mattick, Schlee, 1979; Schlee and 

others, 1979; Mattick and others, 1978) reveal 

that the Late Jurassic and Early Cretaceous 

shelf edge off New Jersey is about 12.5 mi (20 

km) seaward of the present shelf and about 25 mi 

(40 km) seaward of the East Coast Magnetic 

Anomaly (ECMA) (fig. 54). 

The ECMA has been interpreted as a 

"magnetic edge effect" due to the oceancontinent boundary (Keen, 1969; Keen and Keen, 

1974; Klitgord and Behrendt, 1979). Recent 

refraction data (Sheridan and others, 1979) and 

gravity models of the ocean-continent boundary 

structure (Grow, Bowin, and Hutchinson, 1979) 

have supported the interpretation that the ECMA 

100 STATUTE M IL E S 

~~~ ~~~ 

0 COST WELLS 

0 LOWER CRE TACEOUS MAFIC INTRUSION R DIAPIR OR SALT INTRUSION 

....... .... ~~~ S~ 'ij1 H~~ L SEISMIC LINES 

LE GEND 

-- SEISMIC RECORDS SHOWN IN FIGURES 

- 200m -' BATHYMETRIC CONTOUR IN METERS * * * AXIS Of EAST COAST MAGNET IC ANOMALY ""- -,.,.. k~JEFJ~~~SI C EARLY CRETACEOUS 

Figure 54.--Continental Margin off New Jersey 

showing primary structural features 

and seismic profiles discussed in 

this report. The Late JurassicEarly Cretaceous shelf edge has been 

mapped using eight seismic profiles 

and is approximately 12 mi (20 km) 

seaward of the present shelf edge as 

marked by the regional trend of the 

650-ft (200-m) isobath. The 

boundary between continental and 

oceanic crust is inferred to be 

marked by the East Coast Magnetic 

Anomaly (ECMA). The COST No. B-3 

well is about 3 mi (5 km) seaward of 

the present shelf edge and 9 mi (15 

km) landward of the Late JurassicLower Cretaceous shelf edge. Note 

that the shelf edge prograded 25 mi 

(40 km) seaward of the ECMA during 

the Jurassic in the area south of 

Hudson Canyon, whereas it retreated 

by about 20 mi (30 km) in the region 

immediately to the northeast. 

117 
marks the boundary between oceanic crust to the 

southeast and thin continental or transitional 

crust to the northwest. Multichannel seismic 

penetration has typically been less than 4 mi (6 

km) over the ECMA compared with magnetic depthto-source estimates at depths of 4-5 mi (6-8 

km). These data have been interpreted as a 

thickening of the oceanic basement layer beneath 

the ECMA (Grow, Mattick, and Schlee, 1979; 

Klitgord and Behrendt, 1979). This 

interpretation was based on seismic data 

collected prior to 1978. 

During 19 78, a new, high-quality, 

multichannel reflection profile (Line 25, fig. 

54) was collected across the Baltimore Canyon 

trough approximately 6 mi (10 km) south of the 

COST No. B-3 well (drilled after Line 25 was 

shot). This reveals much deeper sedimentary 

reflectors than any of the lines used in 

previous studies by the USGS. The profile was a 

48-channel line collected by Geophysical 

Services Inc. under contract to the USGS. 

Advanced processing steps, including deep-water 

deconvolution, signature deconvolution, 

migration, and depth conversion, were completed 

during the spring of 1979. In addition to the 

high quality of the basic data and the 

opportunity for advanced processing, Line 25 is 

the first publicly available multichannel 

seismic line through the broadest and least 

complex part of the Baltimore Canyon trough. 

Because much deeper penetration was obtained on 

this line than with our previous data, this 

report will discuss Line 25 in some detail and 

will review selected portions of previous lines 

that bear on the deep structure and evolution of 

the ocean-continent boundary structure in the 

vicinity of the Baltimore Canyon trough and the 

COST NO. B-3 well. 

MULTICHANNEL SEISMIC LINE 25 

Line 25 extends nearly 200 mi (320 km) 

southeast from Atlantic City, N.J., passing 6 mi 

(10 km) south of the COST No. B-3 well (fig. 

54). A summary cross section of the entire 

length of Line 25 is shown in figure 55; and a 

53-mi (85-km) segment of an annotated seismic 

record over the ECMA, COST No. B-3 well, and 

Jurassic shelf edge is given in figure 56. Line 

25 started about 12.5 mi (20 km) from the 

coastline (fig. 54), where the shelf sediments 

are more than 3 mi (5 km) thick (fig. 55). The 

undeformed sedimentary wedge thickens seaward to 

approximately 9 mi (14 km) near the axis of the 

ECMA and appears to be underlain by another 

wedge of gently deformed, seaward-dipping 

reflectors between 9 and 11 mi (14 and 18 km) in 

depth (fig. 56, shot point 2350). Although the 

reflectors between 9 and 11 mi (14 and 18 km) in 

depth are interpreted to be Triassic graben 

deposits (which may include red beds, 

evaporites, and volcanic rocks), no definitive 

age or lithology can be assigned to these deep 

reflectors at this time. Because no previous 

seismic line has ever succeeded in recording 

reflections from deeper than about 4 mi (6 km) 

in depth near the axis of the ECMA (Grow, 

Mattick, and Schlee, 1979), the penetration 

achieved with Line 25 represents a significant 

improvement. 

Line 25 also obtained strong, landwarddipping reflectors at 7. 5-8 mi (12-13 km) in 

depth immediately seaward of the Jurassic shelf 

edge (fig. 56, shot point 3400), and these are 

interpreted as Early Jurassic Continental Rise 

turbidites which originally dipped to the 

southeast and gradually reversed dip to the 

northwest during the deposition and subsidence 

of the Baltimore Canyon trough. Although one 

previous seismic line off New Jersey had 

detected landward-dipping reflectors at 5.5-6 mi 

(9-10 km) in depth seaward of the Late JurassicEarly Cretaceous shelf edge (Line 2 depth 

section, Grow, Mattick, and Schlee, 1979), the 

strong reflectors at 7.5-8 mi (12-13 km) in 

depth on this portion of Line 25 indicate that 

the depth to oceanic basement beneath the 

Continental Rise off New Jersey is 1-2 mi (2-3 

km) deeper than estimated from previous seismic 

lines (25 mi (40 km) northeast and southwest of 

Line 25). 

Although a very strong reflector at 9 mi 

(14.5 km) in depth beneath the ECMA was detected 

on Line 25, its reflectivity is difficult to 

recognize in figure 56 because this record has 

time-variant scaling (500 ms) which suppresses 

strong events and amplifies weak events. The 

strong reflector associated with the ECMA is 

more dramatically shown in a true-amplitude 

display (fig. 57, a time section that has not 

been converted to depth). The amplitude anomaly 

at 6.5 seconds in figure 57 is equivalent to the 

"very strong reflector" at 9 mi (14 .5 km) in 

depth in figure 56. The amplitude anomaly does 

not appear to be explainable as a multiple or 

any other kind of artifact produced during 

acquisition or processing. The types of 

sedimentary and (or) igneous rocks that could 

give such an impedance contrast at a depth of 

greater than 9 mi (14.5 km) remain a matter of 

speculation, but interbedded low impedence units 

(salt?) and high-impedance units (volcanic 

rocks, dolomites, and (or) limestones) are one 

possibility. This does not exclude the 

possibility that such salt, volcanic, and 

carbonate deposits could be incorporated in 

Triassic grabens that probably, by analogy with 

onshore exposures, are composed predominantly of 

continental red beds and arkoses (Hubert and 

others, 1978). Another set of impressive 

amplitude anomalies was observed on Line 25 at 

between 4 and 5 seconds in depth (fig. 57). 

These climb upward towards the southeast, rising 

from 6 mi (10 km) in depth beneath the west 

flank of the ECMA to about 2.5 mi (4 km) in 

depth in the vicinity of the Jurassic shelf edge 

(fig. 56). Their origin remains speculative, 

but a prograding carbonate sequence deposited as 

a bank or reef complex appears to be the most 

118 
+200 

1--

c:: 

(jJ 

USGS LINE 25 SE + 2oo 

ATLANTIC CITY, NEW JERSEY 

4 ~~~~~----~~----------~~~~----------------------------------1 0 

L 

L 

4 

\9 -200 -200 SHOT POINT NUMBE R O ~~~~ GC~~~~~~ ~~~~~~~~~~~;;;;~::~~~~~00 ~~~::~~6~ ~~~ L. TERT 

OCEAN 

LATE TERTIARY 

(jJ 

tr L CRET . 

w E. 

I0 

(jJ 

0 

z 

4 w 5 

L 

0 

_J 

'i. 10 

(jJ 

2 0 :>I- Ow Iw 

I-ll.. 

~ 4 0 

Zll.. 

-o 

I 15 IQ._ 

w VE = 5 X 

VELOCITY KM/SEC 

A :~~JI~ ~s T~ c~~J Yso~ ~gAN 1cs ?) 

I 

IQ._ 

w 

0 0 0 50 100 150 200 250 300 

0 50 

KI LOMETERS 

100 150 200 

STATUTE MILES 

Figure 55.--Structural cross section along USGS multichannel Seismic Line 25. The actual seismic 

record between shot points 1900 and 3600 is shown in figure 56. Age designations for 

named reflectors are shown in figure SO. 

obvious possibility. The significant carbonate 

content in the Jurassic section of the B-3 well 

(Pollack, this volume) supports the inference of 

a prograding carbonate bank; whether it was a 

reef or not is uncertain. The high-amplitude 

reflectors may represent carbonate rocks 

deposited in "back-reef" environments. 

A third set of amplitude anomalies observed 

on Line 25 dips seaward from 6.5 to 7.5 seconds 

(shot points 2000 to 2200, fig. 57). These 

appear to form the base of the Triassic-Jurassic 

sedimentary wedge; that is, the top of 

continental basement. Individual blocks of 

fragmented continental crust were not observed 

beneath these strong seaward-dipping events in 

either the migrated or unmigrated data, although 

the resolution capability of multichannel 

seismic techniques at depths in excess of 8 mi 

(12 km) is limited. Further towards land, these 

strong reflectors merge into what appears to be 

a major unconformity, which may be equivalent to 

Falvey's (1974) "breakup unconformity." 

Another phenomenon displayed on Line 25 

better than on previous seismic lines is the 

occurrence of seaward-dipping growth faults 

(that is, listric normal faults) between the 

ECMA and the Jurassic shelf edge (fig. 56). The 

downward continuation of these growth faults is 

obscured by the prograding carbonates, but they 

probably go considerably deeper than shown and 

may ultimately tie into bedding-plane faults 

along the Jurassic slope. The faults were 

probably most active during the time of Jurassic 

carbonate-platform progradation, but movement 

appears to have continued on a few of these 

faults through the Late Cretaceous. The fault 

immediately landward of the COST No. B-3 well 

appears to have offset early Tertiary horizons 

by several tens of feet, but does not appear to 

displace late Tertiary sediments on Line 25. 

Klitgord and Behrendt (1979), in a magnetic 

depth-to-source study of the ECMA, observed a 

systematic pattern of low- or intermediatestrength solutions at· 4-5 mi (6-8 km) in depth 

near the axis of the ECMA compared to solutions 

at 6-7.5 mi (10-12 km) in depth on either 

side. Similar magnetic depth-to-source results 

were found near Line 25, and they are shown as 

triangles in figure 56 (K. Klitgord, oral 

communication, 1979). They occur at about 5.6 

mi (9 km) in depth, just beneath the reflectors 

interpreted as prograding carbonates and more 

than 3 mi (5 km) above the strong reflector at 9 

mi (14 .5 km) (fig. 56). Although none of our 

previous seismic lines obtained seismic 

penetration deeper than 4 mi (6 km) near the 

ECMA, Line 25 clearly suggests that the magnetic 

solutions are well up in the sedimentary 

section. Therefore, interpretations of the ECMA 

involving a thickened ridge of oceanic basement 

underlying the anomaly (Grow, Mattick, and 

Schlee, 1979; Klitgord and Behrendt, 1979) must 

now be revised. While the ECMA probably still 

marks the landward edge of oceanic crust, the 

119 
EAST COAST 

':Y I i~ETIC AN~~~~~ fl 

NW 

(J) 

cr 

w 

.... 

w 

::E 

0 

_J 

;;: 

!!: I 

:I: 

.... 

a. 

w 

0 

10 KILOMETERS 

COST B·3 

WELL 

A• MAGNETIC OEPTH SOLUTIONS 

SE 

§ 

X 

.... 

w 

w 

... 

!!: 

:I: 

.... 

a. 

w 

0 

Figure 56.--Annotated multichannel depth section (migrated) for USGS Seismic Line 25 with magnetic 

anomalies plotted at the top. Line 25 is the first seismic profile to achieve 

penetration deeper than about 4 mi (6 km) in the vicinity of the ECMA and the first 

profile to record reflected energy from deeper than S-6 mi (9-10 km) in the region 

immediately seaward of the Late Jurassic-Early Cretaceous shelf edge. Age horizons on 

shelf from Amato and Simonis (1979), Poag (this volume), and Valentine (this 

volume). Deep-sea correlations from Klitgord and Grow (in press). The triangles at 5 

mi (9 km) in depth beneath the ECMA are magnetic depth-to-source solutions (K. 

Klitgord, oral communication, 1979); see text for further discussion. Location shown 

in figure 54; age designations for named reflectors are shown in figure SO. 

shallow magnetic solutions will have to be 

attributed to secondary volcanic events such as 

dikes, sills, and flows which could have 

occurred in Late Jurassic or Early Cretaceous 

time. Alternatively, the Werner deconvolution 

method for estimating magnetic depth to basement 

may encounter special problems at depths greater 

than 4-5 mi (7-8 km), which makes these deeper 

solutions less reliable than those at shallower 

depths. 

In summary, Line 25 represents an important 

breakthrough in our understanding of the deep 

structure of the Baltimore Canyon trough and the 

evolution of the ocean-continent boundary 

structure, because it now seems probable that no 

basement ridge lies between 4 and 9 mi (6 and 14 

km) in depth along the ECMA or shallower than 8 

mi (13 km) immediately seaward of the Jurassic 

shelf edge. Furthermore, considering the way 

the deep sedimentary reflectors project seaward 

from beneath the shelf and landward from benea t h 

the rise, it seems unlikely that oceanic 

basement is shallower than 8-9 mi (13-14 km) 

beneath the COST No. B-3 well or any part of the 

margin between the ECMA and the Jurassic shelf 

edge (fig. 56). The past failure of 

multichannel seismic systems to record 

reflections from deeper than 4 mi (6 km) between 

the ECMA and the Jurassic shelf edge may be due 

to a combination of high-impedance reflectors in 

the prograding carbonate rocks, which are very 

difficult to penetrate, and diffraction effects 

caused by numerous growth faults. 

GREAT STONE DOME 

A mafic plutonic body, referred to as the 

Great Stone Dome, intruded the Baltimore Canyon 

trough during the Early Cretaceous (Schlee and 

others, 1976) and is shown in figure 58. This 

plutonic body appears to have been intruded 30-

40 million years after the separation of North 

America and Africa , and its emplacement created 

a local unconformity of approximately Aptian 

age. No other mafic intrusions are known to 

intrude the Late Jurassic and younger basins 

120 
SHOT PT. NO. 

2000 2100 2200 2300 2400 2700 

o,;~~~~~~ ~~~~~a.o 

1 

en 

0 

~22--~ i= 

w3-! 

~ 

····1 2 

3 

>- <( 

3: 

~ 6-t~~ ~~~~~~~~~~~~~~~~~~6 IFigure 57.--True-amplitude display (time section) of USGS Seismic Line 25 showing three deep 

amplitude anomalies. See figure 56 for comparison with depth section that has timevariant scaling (that is, weak reflections are amplified while strong reflections are 

reduced). ECMA is the East Coast Magnetic Anomaly. 

beneath the Continental Shelf off the Eastern 

United States, although Cretaceous volcanism has 

been found along the New England seamounts and 

in the White Mountains of Vermont (Tucholke and 

others, 1979). The possibility of secondary 

volcanism occurring 30-40 million years after 

separation of Africa and North America and the 

formation of the ocean-continent boundary which 

is inferred to be the source of the ECMA may 

help explain the apparent conflict between 

shallow magnetic-depth-to-basement values at 4-5 

mi (6-8 km) in depth along the ECMA (Klitgord 

and Behrendt, 1979) and the deeper sediment 

penetration obtained on multichannel Line 25. 

For example, small quantities of secondary 

volcanic rocks such as dikes and sills may have 

also leaked up from the ocean-continent boundary 

zone periodically during the Jurassic and (or) 

Early Cretaceous, which now give rise to the 

magnetic depth-to-source estimates at 4-5 mi (6-

8 km) depth. 

POSSIBLE SALT STRUCTURES IN 

BALTIMORE CANYON TROUGH 

Extensive salt diapirs and related 

structures have been found along the Continental 

Shelf and Slope off eastern Canada (Emery and 

Uchupi, 1972; Jansa and Wade, 1975; Uchupi and 

Austin, 1979), but have only recently been 

reported off the Eastern United States. A 

linear chain of diapir structures has been found 

along the ECMA off Cape Hatteras which is 

thought to be salt (Grow and Markl, 1977; Grow 

and others, 1977), and at least three probable 

salt structures occur along the ECMA where it 

swings landward of the shelf edge in the 

Baltimore Canyon trough region (fig. 54). 

A diapir structure that penetrates up into 

Tertiary sediments has been observed on Line 14 

(fig. 59), and two probable salt intrusions were 

also seen on Line 15 (fig. 60). The latter 

intrusions do not penetrate Creta~eous and 

Tertiary sediments, probably because they were 

blocked from shallower penetration by 

mechanically strong carbonate rocks in the 

prograded carbonate bank or reef complex. Salt 

has also been encountered at a depth of 2.4 mi 

(3.8 km) in an exploration well on the south 

flank of the Great Stone Dome (Oil and Gas 

Journal, 1978), which may be due to salt 

diapirism in that area having been triggered by 

the more dominant mafic pluton. 

121 
SHOT POINT 

C/) 

0 

z 

C/) 

~2 

~ 

ui 

:::!: 

i= 

....J 

~4 cc 

1-

>-

<( 

~ 

6 

~ 1-6 

900 1000 1100 S£ 

0 

2 C/) 

cc 

w 

1-

w 

4~ ....J 

~ 

~ 

:i 

1-

a. 

w 

0 

Figure 58.--Multichannel seismic section (Line 2) over the Great Stone Dome. To date, exploration 

wells have not yielded significant indications of oil or gas on or near this dome 

(modified from Schlee and others, 1976). Location shown in figure 54. 

The salt off eastern Canada is found in the 

Early Jurassic Argo Formation (Jansa and Wade, 

1975); and a similar age can be expected for the 

salt off the Eastern United States. The origin 

of salt along the margins of the Atlantic Ocean 

remains a matter for debate, but the most likely 

explanation is that evaporite basins formed 

along the continental shelves in a shallow 

seaway during the initial separation of Africa 

and North America, probably as a consequence of 

restricted oceanic circulation (Evans, 1977). 

One other possible diapir has been proposed 

in the Baltimore Canyon trough, just north of 

Wilmington Canyon and also along the ECMA 

(Sheridan, 1975), but subsequent multichannel 

'Figure 59.--Multichannel seismic section (Line t> 

14) over inferred salt diapir which 

appears to have originated from very 

deep in the Jurassic section and 

penetrated into Tertiary 

sediments. No exploration wells 

have sampled this structure to 

date. Location shown in figure 54. 

122 

(/) 

0 

~2 2 (.) 

w 

(/) 

~ 

w 4 ::; 

;:: 

__, 

w 

,_ 

~4 

>-

<( 

:;: 

0 

:;: 

,_ 

6 
SHOT POINT 

sw1BOO 2000 2200 2400NE 

li~iiii~~~iiiiiiif0 

C/) 

0 

z 

0 2 C/) 

() a: w 2 w C/) 1-

~ w 

::!: 

ui 0 

...J ::!: 

i= 

...J 4~ w 

> I 

<( 1-

a: fl.. 

1- 4 w 

>-

0 

<( 

::: 

0 

::: 

1-

10 STATUTE MILES 

Figure 60.--Multichannel seismic section (Line 15) showing two small, deep domes which are 

inferred to be salt intrusion. Natural gas has been discovered in three exploration 

wells drilled by Texaco and Tenneco on the northeastern intrusion, but drilling on the 

southwestern structure by Exxon has not indicated any significant shows of either oil 

or gas. Location shown in figure 54 • 

. seismic profiles within 1.2 mi (2 km) of this 

proposed structure (Line 6 and the southern part 

of Line 14) have not detected any obvious salt 

intrusion in that area. Although additional 

salt intrusions will probably be detected as 

more multichannel seismic lines become 

available, the quantity of salt at depth in the 

Baltimore Canyon trough is small in comparison 

to the quantity off Canada or even in comparison 

to the zone south of Cape Hatteras. 

Nevertheless, these probable salt structures do 

suggest a similar structural history to that off 

Canada, even if the quantity of salt deposited 

in such Early Jurassic seaways was variable. 

DEEP STRUCTURE AND EVOLUTION 

A schematic cross section through the 

Baltimore Canyon trough near the COST No. B-3 

well depicts the overall crustal and sedimentary 

structure in this part of the trough (fig. 61). 

Because the B-3 well bottomed in sediments 

of Middle(?) Jurassic age at 3 mi (4.8 km) in 

depth, the remaining 8 mi (13 km) of stratified 

sediments seen on Line 25 are probably Triassic 

through Middle Jurassic in age. In the main 

part of the basin, near and just west of the 

ECMA, the sediments are undeformed down to about 

9 mi (14 km) in depth, except for variable tilt 

related to differential regional subsidence. 

The stratified section between 9 and 11 mi (14 

and 18 km) in depth near the ECMA (fig. 56) 

shows gentle deformation, probably caused by 

deposition in a rapidly subsiding graben 

underlain by small crustal blocks subsiding ~ 

independently. 

The gravity and refraction data (fig. 61) 

support the interpretation that the oceanic 

crust continues westward to the ECMA and that 

the ECMA is caused by a magnetic edge effect 

between thin continental or transitional crust 

to the west and oceanic crust to the east (Keen, 

1969; Keen and Keen, 1974; Klitgord and 

Behrendt, 1979; Grow, Mattick, and Schlee, 1979; 

Sheridan and others, 1979; Grow, Bowin, and 

Hutchinson, 1979). The oldest oceanic crust is 

probably Early Jurassic in age (Klitgord and 

Behrendt, 1979). This is consistent with the 

inception of volcanism in the Newark and 

Connecticut grabens at the Triassic-Jurassic 

boundary (Cornet, 1977; Hubert and others, 

1978). 

Recent geophysical studies of continental 

rifting in the Bay of Biscay, along with new 

deep-sea-drilling results, indicate that the 

123 
NW ~ +200 

BALTIMORE CANYON TROUGH 

--EAST COAST 

MAGNETIC ANOMALY 

SE 

+200 

c:: 

en 

0:: 

w 10 

-------::~_ 200 

1-

w 

w 

I.L 

I.L 

0 

1-

w 40 en 

~ 0 

z 

<( 0 

...J 

'i. en 

60 :J 

z 0 

I 

1-

I 

1-

0.. 

w 

0 

MANTLE 

80 z 

EXPLANATION 

LOWER CRETACEOUS 

VOLCANIC INTRUSION 

ff =REFRACT ION VELOCITY IN KM/SEC. 

100 

I 

1-

0.. 

w 

0 

A -MAGNETIC DEPTH-TO-SOURCE ESTIMATES IMPLYING 

-SECONDARY VOLCANICS (DIKES, SILLS, OR FLOWS) 

0 

0 

100 200 

KILOMETERS 

300 

50 100 150 200 

STATUTE MILES 

Figure 61.--Schematic cross section through Baltimore Canyon trough approximately along Seismic 

Line 25 (figs. 55 and 56) with nearby COST No. B-3 well, geologic features, and 

geophysical parameters projected into the profile. Refraction data are from Ewing and 

Ewing (1959) and Sheridan and others (1979). The moho configuration is projected from 

a gravity model for Line 6. 

transition from deformed graben sediments, 

referred to as syn-rift sediments, to undeformed 

basin sediments, referred to as post-rift 

sediments, occurs after the continental crust 

has been thinned and at the inception of seafloor spreading (Montedert and others, 1979). 

The Bay of Biscay model suggests that syn-rift 

sediments are deposited while the continental 

crust is being thinned by necking in the lower 

crust and listric normal faulting in the brittle 

upper crust. The unconformity marking the 

transition from syn-rift to post-rift sediments 

can be considered equivalent to the "breakup 

unconformity" of Falvey (1974). 

Applying the Bay of Biscay model (Montadert 

and others, 1979) to the Baltimore Canyon trough 

and assuming that the transition from 

continental rifting to sea-floor spreading began 

at the Triassic-Jurassic boundary, we may infer 

that all of the undeformed sediments between 3 · 

and 9 mi (5 and 14 km) in depth near the ECMA on 

Line 25 are Early and Middle Jurassic in age 

(figs. 56 and 61). It follows from this model 

that the deformed sediments between 9 and 11 mi 

(14 and 18 km) near the ECMA (fig. 56) are 

Triassic in age (fig. 61). The graben sediments 

probably contain predominantly continental red 

beds but might include some volcanics and 

evaporites, especially near the base of the 

Early Jurassic (fig. 61). 

Following thinning of the continental crust 

during the Triassic, along with · related 

deposition within Triassic syn-rift grabens, and 

the initiation of sea-floor spreading during the 

earliest Jurassic, the shelf edge prograded 

about 25 mi (40 km) east of the ECMA during the 

Early and Middle Jurassic. The cause of this 

124 
progradation is not known, but carbonate bankand (or) reef-building processes may have been 

important. The Jurassic section within the COST 

No. B-3 well contained a substantial thickness 

of carbonate rocks, but, because this well is 

about 9 mi (15 km) landward of the Late Jurassic 

shelf edge (fig. 56), further drilling is needed 

before the carbonate-bank and (or) reef model 

can be substantiated. Note that north of Hudson 

Canyon (fig. 54), the Jurassic shelf edge lies 

12-19 mi (20-30 km) landward of the ECMA, 

thereby suggesting that the shelf edge retreated 

during the Jurassic in that area. The Late 

Jurassic-Early Cretaceous shelf edge off Cape 

Hatteras and Cape Cod also indicates either 

retreat or nonprogradation during the Jurassic 

in those areas (Grow, Mattick, and Schlee, 1979; 

Schlee, Dillon, and Grow, 1979). 

Great Stone Dome is an isolated igneous 

intrusion that intruded during the Early 

Cretaceous; it is unique along the eastern 

margin of North America. No evidence is 

available at this time to determine whether it 

was derived from the mantle or from within the 

crust. The strong magnetic anomaly over the 

dome suggests a mafic intrusive which would 

probably have been generated in the mantle. 

However, its intrusion followed very rapid 

subsidence during the Jurassic (6 mi (10 km) of 

Jurassic sediments versus approximately 1.2 mi 

(2 km) each during the Cretaceous and Tertiary), 

which might have pushed radiogenic upper 

continental crust and graben sediments deep 

enough to initiate igneous melting. Samples 

from exploration wells on the Great Stone Dome 

have not been released to date, but petrologic 

analyses may yet become available to shed light 

on this question. 

The intrusion of the salt structures along 

the ocean-continent boundary in the Baltimore 

Canyon trough area appears to have occurred 

during the Late Jurassic and Early Cretaceous 

for the two structures on Line 15 (fig. -60) and 

during the Tertiary for the shallow diapir on 

Line 14 (fig. 59). 

The final major event in the evolution of 

the Baltimore Canyon trough has been the retreat 

of the shelf edge during the Late Tertiary 

(Grow, Mattick, and Schlee, 1979; Schlee, Dillon 

and Grow, 1979; Schlee and Grow, this volume). 

The 12.5-mi (20-km) retreat of the shelf edge 

appears to have started with a massive submarine 

erosional event during the late Oligocene and is 

probably related to frequent regressions of sea 

level since that time (Vail and others, 1977; 

Poag, this volume). 

SUMMARY 

The Baltimore Canyon trough began to form 

during the Triassic Period when tensional 

stresses between North America and Africa 

resulted in thinning of the continental crust 

and deposition of sediments within rift 

grabens. The transition from continental 

rifting to sea-floor spreading probably occurred 

during the earliest Jurassic and was marked by 

volcanism and formation of evaporites due to 

restricted oceanic circulation. Within the 

portion of the Baltimore Canyon trough near the 

COST No. B-3 well, the shelf edge prograded 25 

mi (40 km) seaward out over the initial oceancontinent boundary (ECMA) during Early and 

Middle Jurassic time. 

The Jurassic shelf-edge progradation with 

respect to the ECMA occurred southwest of Hudson 

Canyon, while retreat occurred to the northeast 

(fig. 54). Because erosion and retreat of the 

shelf edge are also dominant north of Cape Cod 

and south of Cape Hatteras (Grow, Mattick, and 

Schlee, 1979; Schlee, Dillon, and Groll~, 1979), 

the evidence for a Jurassic progradational event 

off New Jersey appears to be unique elong the 

u.s. margin. On the other hand, submarine 

erosion removed much of the Late Juras~ic-Early 

Cretaceous shelf-edge complex in the other 

areas, especially since the late Oligoc~ne. 

The strong reflectors that occur w~thin the 

prograding Jurassic shelf edge suggest that a 

carbonate-bank and (or) reef complex underlies 

the outer shelf and Continental Slope off New 

Jersey (figs. 56 and 57). The crest of this 

inferred Late Jurassic and Early Cretaceous 

carbonate complex lies 9 mi (15 km) seaward of 

the COST No. B-3 well. Although some Jurassic 

carbonate rocks were encountered in the B-3 

well, the seismic data from Line 25 sugrest that 

more massive carbonates occur at depth beneath 

the B-3 well and farther southeast to·,rard the 

Late Jurassic shelf edge. Only mc~e deep 

drilling can substantiate this infer~nce and 

determine if actual reefal faunas occur within 

the inferred carbonate complex. 

CONCLUSIONS 

1. The COST No. B-3 well was drilled in 2, 686 

ft (819 m) of water and penetrated 13,092 

ft (3, 990 m) of sedimentary rocks in the 

slope area of the Baltimore Canyon 

trough. The age of sedimentary units was 

determined through the examination of 

Foraminifera, calcareous nannofossils, and 

palynomorphs. The section is Cenozoic 

down to about 6,000 ft (1 ,830 m). From 

6,000 to about 9,000 ft (1,830-2,750 m), 

the sediments are Late Cretac~ous in 

age. The base of the Early Cretaceous 

interval is placed between 12,250 and 

13,450 ft (3, 730 and 5,000 m) by various 

workers. The oldest unit in the well was 

considered to be Middle Jurassic 

(Callovian) by one worker ar.f Late 

Jurassic (Kimmeridgian) by others. 

2. The sediments down to about 8,200 ft (2,500 

m) are predominantly mudstones, calcareous 

mudstones, and micritic limeston,~s. In 

the interval from about 8,200 to 12,300 ft 

(2,500 to 3,750 m), medium- to coarse125 
grained sandstones, gray-brown shales, 

micritic limestones, and subordinate coal 

and dolomite are the major lithologies. 

Below 12,300 ft (3,750 m), to the bottom 

of the well at 15,820 ft (4,822 m), the 

section consists of limestones, fine- to 

medium-grained sandstones, dark-colored 

shales, and coal seams. 

3. The Tertiary sediments were deposited, for 

the most part, in slope water depths. The 

Cretaceous section and the upper half of 

the Jurassic interval were deposited in 

lower- to outer-shelf water depth. The 

lower half of the Jurassic section 

reflects inner shelf to marginal-marine 

conditions. 

4. Porosities of units down to about 8,200 ft 

(2,500 m) range from 20 to 32 percent. 

The corresponding permeabilities of these 

fine-grained rocks are generally low. The 

interval between 8,200 and 11,630 ft 

(2,500 and 3,550 m) contains more than 

1,000 ft of sandstone with porosities 

between 16 and 24 percent. Thin sandstone 

and limestone units in the interval from 

11,630 to 15,820 ft (3,550 to 4,822 m) 

have porosities between 2 and 25 

percent. In general, only a moderate loss 

of porosity occurs with increasing burial 

depth in this well, and potential 

reservoir units are present in most parts 

of the B-3 section. 

5. Petrographic analysis has shown that calcite 

cementation is the major cause of porosity 

loss in this well. Feldspar decomposition 

and compaction have only minor influence 

on porosity. Most sandstones in this well 

are subarkoses with subordinate arkoses, 

quartzarenites, and feldspathic 

litharenites. 

6. Temperature logs were not run in this well, 

but temperature data from other 

geophysical logs indicate an approximate 

geothermal gradient of 1.26°F /100 ft 

(22.8°C/km). 

1. Organic geochemical studies, coupled with 

data on vitrinite reflectance and color 

alteration of visible organic matter, 

indicate that rocks down to approximately 

14,300 ft (4,359 m) are thermally immature 

to marginally mature with respect to 

hydrocarbon generation. Although certain 

intervals above 14,300 ft (4,359 m), 

particularly in the Tertiary section above 

6,000 ft (1,830 m), contain abundant 

organic matter (of both oil-prone and gasprone types), the low degree of thermal 

maturation makes it unlikely that these 

sediments have generated significant 

quantities of hydrocarbons. The section 

below 14, 300 f t ( 4, 359 m), especially in 

the interval from about 15,000 ft (4,572 

m) to the base of the well, is both 

thermally mature and rich in organic 

carbon. The section contains dominantly 

exinite and vitrinite types of organic 

matter and must therefore be considered to 

be gas-prone rather than oil-rrone. 

a. The combination of the above-1:1 sted factors 

indicates that the intervals Pith the best 

potential for hydrocarbon di~coveries are 

in the basal part of the well, below 

approximately 14,000 ft (4,267 m). This 

interval contains thermally rrature source 

rocks, porous (and sufficiently permeable) 

sandstone, possibly also limestone 

reservoirs, and shale seals. The this 

interval is most likely to be gasproductive rather than oil-productive 

owing to the dominance of terrestrially 

derived organic matter. This conclusion 

is reinforced by the "significant" gas 

show encountered during drilling in the 

interval from 15,744 to 15,752 ft (4,799 

to 4,801 m). Some potential for both oil 

and gas production also exists in the 

marginally mature zone abov~ 14,000 ft 

(4,267 m), either through in situ 

generation or upward mi.gration of 

hydrocarbons into reservoir units. 

REFERENCES CITED 

Abbott, w. H., in press, Analysi.s of diatom 

assemblages and stratigraphically 

significant silicoflagellate~ from the 

United States Geological Survey Atlantic 

Margin Coring Program and other Atlantic 

margin sites: Micropaleontolo.1Y • 

Adinolfi, Frederick, and Jacobson, s. s., 1979, 

Geologic correlation with oth~r wells, in 

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