~\i!E{iii\\\\~~«(f.ir!iifi!t Structural Framework Stratigraphy and 

~~~~~~1~~~l P~troleum Geology o/ the Area of ' . 

~,=~~,~~\~~t\,\~~?8:~}/?-::: 011 and Gas Lease Sale No. 49 on the 

li~~J'f~Jifll*¥,r~ u.s. Atlantic Continental Shelf and Slope 

Structural Framework, Stratigraphy, and 

Petroleum Geology of the Area of 

Oil and Gas Lease Sale No. 49 on the 

U.S. Atlantic Continental Shelf and Slope 

Robert E. Mattick and Jacqueline L. Hennessy, editors 

G E 0 L 0 G I CAL 5 U R V E Y C I R C U LA R 812 

Washington 1980 
United States Department of the Interior 

CECIL D. ANDRUS, Secretary 

Geological Survey 

H. William Menard, Director 

Library of Congress Catalog-card No. 80-600090 

Any use of trade names in this publication is for descriptive purposes 

only and does not constitute endorsement by the U.S. Geological Survey. 

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

1200 South Eads Street, Arlington, VA 22202 
Abstract --------------------------------------

Introduction -----------------------------------

Acknowledgments ------------------------------

Processing of seismic data, by Robert C. Anderson, 

William C. Patterson, and Richard Wise __________ _ 

Geologic setting, by Kenneth C. Bayer and 

Robert E. Mattick-----------------------------

Structural framework, by John A. Grow and 

Kim D. Klitgord -------------------------------

Seismic-refraction data -----------------------

Multichannel seismic-reflection data-------------

Magnetic data -------------------------------

Gravity data --------------------------------

The ocean-continent boundary and subsidence 

history -----------------------------------

Stratigraphy ----------------------------------- Foraminiferal stratigraphy and paleoecology, by 

C. Wylie Poag -----------------------------

Pre-Cretaceous rocks ---------------------

Cretaceous ------------------------------

Paleocene -------------------------------

Eocene ---------------------------------

Oligocene -------------------------------

Miocene --------------------------------

CONTENTS 

Page 

1 

2 

4 

4 

6 

8 

8 

19 

21 

26 

33 

35 

35 

35 

35 

39 

39 

43 

43 

Stratigraphy-Continued 

Foraminiferal stratigraphy and paleoecologyContinued 

Pliocene --------------------------------

Pleistocene ------------------------------

Holocene ------------------------------- Acoustic stratigraphy, by JohnS. Schlee ________ _ 

Acoustic units ---------------------------

Discus~ion ------------------------------

Petroleum geology ------------------------------

General comments, by Robert E. Mattick and 

0. W. Girard, Jr.---------------------------

COST No. B-2 well, by Peter A. Scholle ________ _ 

Shelf, by Robert E. Mattick and Kenneth C. Bayer 

Slope, by Robert E. Mattick, Peter A. Scholle, and 

0. W.Girard,Jr. __________________________ _ 

Organic matter in slope sediments -----------

Reservoir rock on the slope -----------------

Potential hydrocarbon traps on the slope _____ _ 

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

Geology ------------------------------------ Petroleum geology -------------------------·--

References cited --------------------------------

ILLUSTRATIONS 

FIGURE 1. Map showing location of lease-sale tracts, drill holes, and seismic-reflection grid on the mid-Atlantic continental 

Page 

47 

47 

48 

48 

58 

72 

75 

75 

79 

84 

87 

87 

88 

89 

93 

93 

94 

97 

Page 

margin of the United States------------------------------------------------------------------ 3 

2. Flow chart of the first-pass processing steps performed by the USGS on multichannel seismic-reflection profiles 11, 12, and 13 -------------------------------------------------------------------------- 5 

3. Diagra111matic cross section of the Baltimore Canyon Trough------------------------------------------- 7 

4-6. Structure-contour maps of the mid-Atlantic continental margin of the United States showing depth to the top of: 

4. Upper Cretaceous rocks------------------------------------------------------------------- 9 

5. Lower Cretaceous rocks------------------------------------------------------------------- 10 

6. The acoustic basement-------------------------------------------------------------------- 11 

7, 8. Isopach maps of the mid-Atlantic continental margin of the United States showing: 

7. Thickness of Lower Cretaceous and older sedimentary rocks above the acoustic basement ------------- 12 

8. Total sediment thickness between the sea floor and the acoustic basement-------------------------- 13 

9. Map showing locations of seismic-refraction surveys discussed in text------------------------------------ 14 

10. Cross section from outer shelf to rise based on recent seismic-refraction surveys--------------------------- 15 

11. Line drawings showing strong reflectors, interval velocities, and inferred ages of horizons interpreted from 

seismic-reflection profiles 9, 10, 6, and 2--------------------------------------------------------- 16 

12. Part of CDP multichannel seismic profile 2 having vertical scale in depth --------------------------------- 18 

13. Part of CDP multichannel seismic profile 6, which crosses the Continental Slope --------------------------- 20 

14, 15. Parts of CDP multichannel seismic profiles having vertical scale in depth: 

14. Profile10------------------------------------------------------------------------------ 22 

15. Profile9------------------------------------------------------------------------------- 23 

III 
Page 

FIGURE 16. Graphs showing velocities and deposition rates at the COST No. B-2 well site ---------------------------- 24 

17. Aeromagnetic anomaly map of the Baltimore Canyon Trough area ------------------------------------- 25 

18. Edge and dike models assumed in making magnetic depth estimates ------------------------------------ 26 

19, 20. Diagrams showing a comparison between seismic-reflection data and magnetic depth estimates for: 

19. Seismic lines 9 and 2 -------------------------------------------------------------------- 27 

20. Seismic lines 6 and 10 ------------------------------------------------------------------- 28 

21. Contour map showing estimated depth to magnetic basement in the Baltimore Canyon Trough area---------- 29 

22. Free-air gravity map of the Baltimore Canyon Trough area------------------------------------------- 30 

23. Profile showing gravity anomalies at the continental margin along seismic line 6-------------------------- 31 

24. Geologic section across the ocean-continent boundary near seismic profile 2 ------------------------------ 32 

25. Geologic section based on interpretation of seismic profile 6, which crosses the ocean-continent boundary ______ 33 

26. Graph showing subsidence rates of shelf and adjacent slope-rise areas in the Baltimore Canyon Trough area____ 34 

27. Map of the United States mid-Atlantic margin showing locations of lease tracts, seismic grid, sample sites, and 

cross sections illustrated in figures 28-35 ------------------------------------------------------ 36 

28. Schematic geologic cross section of the Baltimore Canyon Trough-------------------------------------- 37 

29. Schematic paleoecologic cross section of the Baltimore Canyon Trough---------------------------------- 38 

30-32. Schematic dip sections showing stratigraphy and paleoecology of sedimentary rocks in the: 

30. Northern Baltimore Canyon Trough area--------------------------------------------------- 40 

31. Southern Baltimore Canyon Trough area--------------------------------------------------- 41 

32. Central Baltimore Canyon Trough area----------------------------------------------------- 42 

33. Schematic strike section showing stratigraphy and paleoecology of the Coastal Plain segment of the Baltimore 

Canyon Trough area ----------------------------------------------------------------------- 44 

34. Schematic stratigraphic and paleoecologic section through four wells that penetrated Jurassic rocks within the 

Baltimore Canyon Trough area --------------------------------------------------------------- 45 

35. Schematic strike section showing stratigraphy and paleoecology of upper Cenozoic rocks at the seaward margin 

of the Baltimore Canyon Trough -------------------------------------------------------------- 46 

36. Schematic diagram of a depositional sequence showing the different types of relations that can exist along the 

same unconformity, and a chronostratigraphic section showing where the sedimentary record is most 

complete --------------------------------------------------------------------------------- 50 

37. Schematic diagrams showing possible types of stratigraphic relations found at the upper and lower bounding 

surfaces in a depositional sequence---------------------------------.--------------------------- 51 

38. A part of CDP multichannel seismic profile 6 off southern New Jersey----------------------------------- 52 

39. The same part of seismic profile 6 that is shown in figure 38 but on which the acoustic units are labeled________ 53 

40. A generalized lithologic section based on 13 holes drilled near the seaward edge of the Atlantic Coastal Plain 

from North Carolina to New York ------------------------------------------------------------- 54 

41. Diagram showing environments of deposition as represented in the generalized lithologic section in figure 40 ___ 55 

42. The depth and time section of seismic line 6 under the seaward edge of the Continental Shelf, Continental Slope, 

and upper Continental Rise ------------------------------------------------------------------ 59 

43. Maps showing characteristics of unit A in the Baltimore Canyon Trough area ----------------------------- 60 

44. A depth section along seismic line 12 parallel to the coast--------------------------------------------- 61 

45-49. Maps of the Baltimore Canyon Trough area showing thickness, depositional environment, and averaged interval 

velocity of: 

45. Unit B ------------------------------------------------------------------------------- 62 

46. Unit C ------------------------------------------------------------------------------- 64 

47. Unit D ------------------------------------------------------------------------------- 65 

48. Unit E ------------------------------------------------------------------------------- 67 

49. Unit F ------------------------------------------------------------------------------- 68 

50. An enlargement of a part of figure 38 (line 6) to show the delta built during accumulation of unit F ------------ 69 

51, 52. Maps of the Baltimore Canyon Trough area showing thickness, depositional environment, and averaged interval 

velocity of: 

51. Unit G ------------------------------------------------------------------------------- 71 

52. Unit H ------------------------------------------------------------------------------- 73 

53-55. Isopach maps of the Baltimore Canyon Trough area: 

53. Probable Middle and Lower Jurassic and Triassic sedimentary rocks (units A and B combined)-------- 74 

54. Inferred Cretaceous and Upper Jurassic sedimentary rocks (units C, D, and E combined)------------ 75 

55. Inferred Cenozoic sedimentary rocks (units F, G, and H combined)------------------------------- 76 

56. Structure-contour map of the top of basement rocks in the Baltimore Canyon Trough area---------------·--- 76 

IV 
Page 

FIGURE 57. Schematic section through the northern Scotian basin showing main stratigraphic units-------------------- 77 

58. Part of seismic profile 15 showing anticlinal structures along the shelf edge in the Baltimore Canyon Trough 

area_____________________________________________________________________________________ 78 

59. Generalized plot of lithologies and depositional environments of sediments in the COST No. B-2 well_________ 80 

60-63. Graphs for the COST No. B-2 well showing: 

60. Comparison of density log curve of porosity with measured core porosities and empirically determined 

permeabilities ---------------------------------------------------------------------- 81 

61. Comparison of various measures of thermal maturity as a function of depth ----------------------- 83 

62. Summary and comparison of analyses of organic content of sediments---------------------------- 84 

63. Summary and comparison of type of organic matter in samples ------------------------~--------- 85 

64. Diagrammatic cross section illustrating potential hydrocarbon traps in the Baltimore Canyon Trough area _____ 86 

65. Geologic model derived from seismic bright spot---------------------------------------------------- 87 

66. Interpreted depth section computed along seismic-reflection line 2 ------------------------------------- 90 

67. Diagram presenting a geologic interpretation of the part of seismic profile 2 shown in figure 66 -------------- 91 

TABLES 

Page 

TABLE 1. Acoustic units delineated in the Baltimore Canyon Trough area---------------------------------------- 51 

2. A comparison of the thickness of acoustic units from seismic line 2 with the thickness of rocks of equivalent age 

in the COST No. B-2 well------------------------------------------------------------------- 56 

3. Seismic facies present in the Baltimore Canyon Trough area ________________ _:_________________________ 56 

4. Summary of combustion and thermal analysis of Cretaceous sapropels collected during DSDP Leg 44 from site 

391, Blake Basin--------------------------------------------------------------------------- 88 

v 
Metric unit 

millimeter (mm) meter (m) 

kilometer ( km) 

square meter (m2 ) 

square kilometer (km2) 

hectare ( ha) 

cubic centimeter (cma) 

liter (L) 

cubic meter (m3) 

cubic meter cubic hectometer (hm3) 

liter 

liter 

liter 

cubic meter 

cubic meter 

gram (g) 

gram 

metric tons (t) 

metric tons 

kilogram per square centimeter (kg/cm2) kilogram per square 

centimeter 

cubic meter per second 

(m3/s) 

CONVERSION FACTORS 

Inch-Pound equivalent 

Length 

0.03937 inch (in) 

3.28 feet (ft) 

.62 mile (mi) 

Area 

10.76 

.386 

2.47 

Volume 

0.061 

6\1.03 

35.31 

.00081 

=810.7 

2.113 

1.06 

.26 

.00026 

6·.290 

Weight 

0.035 

.0022 

1.102 

0.9842 

square feet (ft2) 

square mile (mi2) acres 

cubic inch (ina) 

cubic inches 

cubic feet (ft3) 

acre-foot (acre-ft) 

acre-feet 

pints (pt) 

quarts (qt) gallon (gal) 

million gallons (Mgal or 106 gal) barrels (bbl) (1 bbl=42 gal) 

ounce, avoirdupois ( oz avdp) pound, avoirdupois (lb avdp) 

tons, short ( 2,000 lb) 

ton, long (2,240 lb) 

Specific combinations 

0.96 atmosphere (atm) 

.98 

35.3 

bar (0.9869 atm) 

cubic feet per second (fta/s) 

Metric unit Inch-Pound equivalent 

Specific combinations-Continued 

liter per second (L/s) 

cubic meter per second 

per square kilometer 

[(m3/s)jkm2] meter per day (m/d) 

meter per kilometer 

(m/km) 

kilometer per hour 

(km/h) 

meter per second (m/s) 

meter squared per day (m2jd) 

cubic meter per second 

(ma;s) 

cubic meter per minute 

(m3 /min) 

liter per second (L/s) 

liter per second per meter [ (L/s)/m] 

kilometer per hour 

(km/h) 

meter per second (m/s) 

gram per cubic 

centimeter (gjcm-'~) 

gram per square centimeter (gjcm2) 

gram per square centimeter 

degree Celsius (°C) 

degrees Celsius 

(temperature) 

.0353 

91.47 

3.28 

5.28 

.9113 

3.28 

10.764 

22.826 

=264.2 

15.85 

4.83 

.62 

2.237 

612.43 

2.048 

cubic foot per second 

cubic feet per second per 

square mile [ (fta;s) jmi2] 

feet per day (hydraulic 

conductivity) (ft/d) 

feet per mile (ft/mi) 

foot per second (ft/s) 

feet per second 

feet squared per day (ft2jd) 

(transmissivity) 

million ~allons per day (Mgal/d) 

gallons per minute (gal/min) 

gallons per minute 

gallons per minute per foot 

[(gal/min) /ft] 

mile per hour (mi/h) 

miles per hour 

pounds per cubic foot (lb/fta) 

pounds per square foot (lb/ft2) 

.0142 pound per square inch (lb/in2) 

Tern perature 

1.8 degrees Fahrenheit (°F) = [ (1.8 X °C) +'32] degrees Fahrenheit 
Structural Framework, Stratigraphy, and Petroleum 

Geology of the Area of Oil and Gas Lease Sale No. 49 

on the U.S. Atlantic Continental Shelf and Slope 

Robert E. Mattick and Jacqueline L. Hennessy, editors 

ABSTRACT 

On September 23, 1977, the U.S. Department of the Interior 

announced the tentative selection of 136 tracts for Sale No. 49 

of oil and gas leases in the Ba)timore Canyon Trough on the U.S. 

Atlantic Continental Shelf and Slope. This report summarizes 

the geology and petroleum potential of the area. 

The Baltimore Canyon Trough is an elongate, seawardopening sedimentary basin filled by as much as 14 km of 

Mesozoic and Cenozoic sedimentary rocks. The basin first formed under the New Jersey shelf and gradually spread west and 

south as the area subsided after the rifting that formed the 

Atlantic basin. 

Rocks of the Triassic and Jurassic Systems together are more 

than 8 km thick in a depocenter areally restricted to the northern part of the trough. Basal Jurassic rocks are apparently nonmarine sedimentary rocks bedded with evaporite deposits. 

Direct evidence that some salt is in the basal Jurassic section 

comes from the Houston Oil and Minerals 676-1 well, which 

penetrated salt at a depth of about 3.8 km. 

During the Middle and Late Jurassic, more open marine conditions prevailed than in the Early Jurassic, and carbonate 

banks and reefs formed discontinuously along the seaward side 

of the shelf. Sand flats likely occupied the central part of the 

shelf, and these probably graded shoreward into nonmarine red 

beds that accumulated in a bordering coastal plain. Thick nonmarine sands and silty shales of Late Jurassic age were 

deposited in what is now the nearshore and midshelf area. 

These sedimentary rocks probably grade into thick marine carbonate rocks near the present shelf edge. 

During the Cretaceous, less sediment accumulated (about 4 

km) than during the Jurassic, and most was deposited during 

Early Cretaceous time. The Cretaceous units show two main 

trends through time- a diminishing rate of sediment accumulation and an increase in marine character of sediments. During 

the Middle and Late Cretaceous, calcareous sand and mud filled 

the basin, buried the shelf-edge reefs and later spilled across the 

reefs into the oceanic basin as worldwide sea level reached a 

maximum. 

Cenozoic deposits are spread over the present shelf and adjacent Coastal Plain in overlapping sheets of marine and nonmarine sediment. The maximum thickness (1.5 km) is along the 

outer part of the present shelf. 

Major tectonic deformation in the Baltimore Canyon Trough 

area appears to have terminated near the end of the Early 

1 

Cretaceous, when at least one large mafic intrusion (Great 

Stone dome) was emplaced. Upper Cretaceous sedimentary 

rocks are arched above older uplifted fault blocks near the shelf 

edge; this arching may be the result of draping due to differential compaction or, perhaps, minor movement of the fault blocks 

during Late Cretaceous time. 

The dominance of terrestrial over marine-derived organic 

matter in sediment samples from the COST No. B-2 well indicates that economic amounts of liquid petroleum hydrocarbons were probably not generated in the area but suggests a 

high potential for generation of wet or dry gas. Supporting 

evidence for the presence of natural-gas deposits on the slope 

comes from AMCOR 6021, the upper 305m of which penetrated 

sediments that contained methane, ethane, and propane. Texaco, Inc., has announced that its 598-1 well yielded nearly 

479,000 ma of natural gas per day from two zones during early 

testing. Further indication of possible gas deposits comes from 

analyzing the amplitude (bright spots) of seismic data. 

Geochemical studies of the COST No. B-2 well have shown 

that the shelf area of the Baltimore Canyon Trough has a 

relatively low geothermal gradient today and that it apparently 

has had a gradient as low or even lower throughout the Cretaceous to Holocene. A controversy exists concerning the maturity of the basal sediments penetrated by the COST No. B-2 well. 

Although significant amounts of gaseous hydrocarbons may 

have been generated, large amounts of liquid petroleum hydrocarbons probably have not yet been generated. 

Although the sediments penetrated in the COST No. B-2 well 

are predominantly nonmarine to marginal marine, regional 

geology and seismic data indicate that sections to the east and 

southeast are probably more marine. By analogy with the 

Scotian Shelf, a more fully marine section would be more likely 

to contain source rocks than would nonmarine to marginalmarine sections. Studies of the Scotian Shelf indicate that the 

percentage of amorphous organic material, which can be c~nverted to petroleum at relatively low temperatures, tends to Increase in the direction of deep-water environments. Petroleum 

could also have been generated under the present lower slope 

and rise in basin facies that are rich in organic matter and then 

could have migrated to reservoirs along the shelf edge. Possible 

patterns of thermal maturity (that is, sufficiently high rock 

temperatures to have generated hydrocarbons) are difficult to 

predict, but geothermal gradients might increase toward the 

shelf edge, where major faults and intrusions have been postulated from seismic data. 
EXPLANATION 

D 

D 

0 

Isobath shown for 200 and 2000 m 

Lease sale No. 49 

Lease sale No. 40 

Seleded drill holes 

USGS seismic lines 

Sedion shown in denoted figure 

25 50 

4Ct60 ~0 

PENNSYLV~~IA_~ 

--/-- (f/ 

'~\"·,....,NEW J:SEY 

"' ANCHOR GAS- RAGOVIN I 

) ~-~c__ 1- 39°+ 

38°+ ,--- --c_ __ /'' 

J & J 

ENTERPRISE~~­ TAYLOR I.G

1 VIRGINIA J • I 

) 

j) 

\J~/ lfJ/>..'11'1-,lfi!,_ 

374 

"1'&'' 

--'~' Blair and others 

WEYERHAEUSER 1 

o\ Blair and others 

TWIFORD 1 

MOBIL-N.C~ 360+ 10 

Blair and others 

COLLINS 10 

NORTH 0 

CAROLINA ES 0- N.C. 2 

l ............. U .. 

I 

I 

I 

I 

ANCHOR GASDICKINSON I 

I 

I 

I 

I.....___ 

I ......___ 

I 

I 

I 

I 

I 

\ / 

,.) ~ 

/ r--.00 

35°+ 

o--- HOUSTON OIL AND 

~MCOR '-.__MINERALS 676--1 

6011 ---... ......___ 

I 

I 

I 

I 

I 

AMCOil'-

06020 

I 

I 

I 

I 

I 

''''v~ I "'-...!..' 

FIGURE 1.-Map showing location of lease-sale tracts, drill holes, and seismic-reflection 

grid on the mid-Atlantic continental margin of the United States. Locations of sections 

for figures 38, 42, and 44 are shown also. AMCOR, Atlantic Margin Coring Project; 

ASP, Atlantic Slope Project; DSDP, Deep Sea Drilling Project. 

2 
On the shelf, potential hydrocarbon traps are associated with 

diapirs, drape structures over uplifted fault blocks, and faults. 

Seismic evidence suggests that although these potential traps 

are sparse under the inner-shelf and midshelf areas, they are 

more common along the landward edge of the shelf-slope break. 

Along the shelf edge, good possibilities exist for numerous 

structural traps related to rift or prerift tectonism. On seismic 

sections, uplifted fault-block structures appear to be numerous, 

to be about 5-10 km wide, and to involve several hundred 

meters of relief. Movement of these basement blocks may have 

continued throughout Cretaceous time; if so, the chance of finding significant anticlinal and fault-related hydrocarbon traps 

would be enhanced. 

Seismic and indirect geologic evidence suggests the presence 

of potential hydrocarbon traps on the present slope that are 

related to a paleoshelf margin. What is now the Continental 

Slope is believed to be underlain by sequences of Jurassic and 

Lower Cretaceous sedimentary rocks deposited, during periods 

of fluctuating sea level, above a carbonate platform or possibly 

atop high-standing basement blocks. The landward shift of the 

present shelf edge relative to the buried paleoshelf edge is 

20-30 km. 

The importance of the paleoshelf edge, as far as petroleum is 

concerned, is the fact that it is a large high that could contain 

zones of very porous carbjnate rock in both reefal and carbonate platform material. ~'his high is apparently bordered on 

its seaward flank by at least 6 km of slope sediments rich in 

organic matter. Furthermore, thick shale beds, which probably 

overlie the paleoshelf, could provide a relatively impermeable 

seal needed to trap migrating fluids. 

INTRODUCTION 

On September 23, 1977, the U.S. Department of 

the Interior announced the tentative selection of 

136 tracts totaling 77 4,273 acres for proposed Oil 

and Gas Lease Sale No. 49 on the mid-Atlantic 

Outer Continental Shelf (OCS) and the upper part 

of the Continental Slope (fig. 1). The tracts are in 

water depths between about 35 and 1,500 m (fig. 

1). The sale, held in February 1979, was the second 

(the first was Sale No. 40 (fig. 1)) in the Baltimore 

Canyon Trough area. The primary purpose of this 

report is to summarize the general geology of the 

area insofar as it pertains to petroleum potential. 

Much of our information has been derived from 

indirect evidence- chiefly seismic-reflection profiles. Since 1973, the USGS has contracted for 

several thousand kilometers of CDP (commondepth-point) profiles on the Atlantic continental 

margin (Schlee and others, 1976; Schlee, Martin, 

and others, 1977; Dillon and others, 1979; Grow 

and others, 1979). The processing of seismic data is 

described by Robert C. Anderson, William C. Patterson, and Richard Wise (this volume). 

The results from the COST No. B-2 well have 

been used by C. Wylie Poag (this volume) and John 

3 

S. Schlee (this volume) to discuss the stratigraphy 

and depositional environments of the Baltimore 

Canyon Trough area. These two authors, however, 

use somewhat different approaches. The interpretations of Poag are based primarily on preliminary 

analyses of forminiferal assemblages derived from 

16 offshore borings and on a review of published 

stratigraphic investigations of Coastal Plain wells. 

His interpretations of onshore stratigraphy are 

based largely on data taken from the comprehensive compilation by Brown, Miller, and Swain 

(1972; also see references therein). Two major programs (besides the COST No. B-2 well) provided 

sediment samples upon which the foraminiferal 

analyses were based: 

1. In 1967, a consortium of oil companies conducted their Atlantic Slope Project (ASP) 

aboard the M/V Caldrill I (Minard and others, 

1974; Weed and others, 1974; Poag, 1978). 

They drilled coreholes at seven sites along 

the base of the Continental Slope adjacent to 

the Baltimore Canyon Trough. Sediment 

penetration was limited to approximately 330 

m, and water depth at hole sites was as much 

as 1,500 m. 

2. In 1976, the USGS (U.S. Geological Survey) 

undertook the Atlantic Margin Coring (AMCOR) Project (Hathaway and others, 1976). 

Cores were recovered at 19 sites (9 in the 

Baltimore Canyon Trough area); these sites 

and cores are designated AMCOR in this 

volume (fig. 1). Like the ASP coreholes, these 

penetrated no deeper than 330 m. Water 

depth at hole sites was as much as 300 m. 

Whereas Poag's emphasis is on analyses of drillhole samples, Schlee's emphasis is on the acoustic 

characteristics of seismic reflectors. Schlee describes the seismic units delineated on the seismic 

records and thereby provides an interpretation of 

the depositional environment in which the rocks 

they represent were formed. Schlee's approach 

allows him to interpret the stratigraphy and paleoecology of sequences below the bottom of the 

COST No. B-2 well {4,890 m below kelly bushing). 

Grow and Klitgord (this volume), in an effort to 

interpret the structural framework of the Baltimore Canyon Trough area, have integrated the 

seismic-reflection data with the results obtained 

from seismic-refraction surveys, velocity computations, and gravity and magnetic surveys. Interpretations of the magnetic field (Grow and Klitgord, this volume) are based on data from a high-
sensitivity aeromagnetic survey along 185,000 km; 

the survey was flown and the data were compiled 

and contoured by LKB Resources, Inc. 

The discussion of petroleum geology in this 

report is divided into four sections entitled: (1) 

General Comments; (2) COST No. B-2 Well; (3) 

Shelf; and (4) Slope. Analogies between the U.S. 

Atlantic margin and other offshore areas (producing and nonproducing) are discussed in the first 

section. In the second section, analyses of cuttings, 

cores, and logs from the COST No. B-2 well (the 

only deep well on the outer shelf in the Baltimore 

Canyon Trough from which data are available) provide information about lithology, depositional environments, organic-carbon contents and types, 

thermal maturity, reservoir rock character, and 

presence or absence of seals. Because much has 

been written already on the petroleum geology of 

the shelf, the third section is short and deals 

primarily with potential traps. Further discussions 

pertaining to the petroleum geology of the shelf 

can be found in Mattick and others (197 4), Smith 

and others (1976), Scholle (1977b), and Schlee, 

Martin, and others (1977). In the fourth section, 

much of the discussion of the slope area is derived 

from geophysical data and is somewhat 

speculative. The authors attempt to draw 

preliminary conclusions concerning source rocks, 

reservoir rocks, and potential traps on the slope. 

As often happens, authors of different parts of 

this report have some conflicting interpretations, 

some of which are based on the same data. Where 

such conflicts have arisen in this report, an attempt has been made to refer the reader to the 

alternative or conflicting interpretation(s) rather 

than to force an artificial conformity among the 

different sections. For example, Poag (this volume) 

places the Cretaceous-Jurassic boundary in the 

COST No. B-2 well at 4,060 m, whereas Bayer and 

Mattick (this volume) place the boundary below the 

basal section penetrated in this well. Bayer and 

Mattick follow Scholle (1977a, p. 8) who said, 

"Although the basal part of the section might well 

be Jurassic, the consensus now favors a Berriasian 

(Early Cretaceous) age***." According to E. I. 

Robbins (oral commun., 1977), however, 

dinoflagellates in a core at 4,060 m from the COST 

No. B-2 well indicate a Kimmeridgian (Late 

Jurassic) Age. 

ACKNOWLEDGMENTS 

We thank William P. Dillon and Thomas G. Gib4 

son for their editorial and technical advice in 

preparing the section on foraminiferal 

stratigraphy and paleoecology. Page C. Valentine, 

Raymond E. Hall, Charles C. Smith, Richard Benson, and William H. Abbott contributed 

biostratigraphic analyses, and William H. Abbott 

provided the paleoecologic interpretations of 

diatom assemblages. We gratefully acknowledge 

technical assistance from the following USGS personnel: Peter K. Stinger, Frederick N. Zihlman, 

and Patricia L. Brady for compiling velocity data 

and maps and Lois Tomlinson for her meticulous 

work in preparing and correcting many of the 

figures. 

PROCESSING OF SEISMIC DATA 

By ROBERT C. ANDERSON, WILLIAM C. PATTERSON, and 

RICHARD WISE 1 

The location of the seismic profiles discussed in 

this volume are shown in figure 1. These profiles 

were recorded by Digicon Geophysical Corporation 

under USGS contract in the years 1973 through 

1976. Profiles 2 and 3 were processed by Digicon 

Geophysical Corporation, profiles 6, 9, and 10 were 

processed by Geophysical Services, Inc., and 11 

and 12 were processed by the USGS. Final processing for profile 13 has not been completed. 

A flow chart of the first-pass processing procedures performed by the USGS is shown in figure 

2. Those performed by contract service companies 

were similar. Processing begins with demultiplexing of field records, that is, sorting the data into a 

format compatible with specific computer requirements. Correction for signal-amplitude decay 

is made in the demultiplexing phase by applying a 

gain function, usually an exponential curve. The 

gain curve is designed to correct for the average 

attenuation of amplitude while preserving the 

short-period variations caused by changes in the 

subsurface acoustic contrasts. In this phase of processing, trace editing is performed to remove erroneous data. 

Data Analysis (fig. 2) is usually performed 

several times along a profile. Processing 

parameters are rechecked and altered if necessary 

to account for changes in conditions near the shotpoint. For many profiles, the data analysis provides a(iditional iQformation to the interpreter 

1 Digicon Geophysical Corporation, Houston, Texas 
DATA ANALYSIS ----------------------i 

ANALYZE DATA RlR 

DIFFERENT LOCATIONS AND 

SELECT PARAMETERS 

1. Spectrum Plot 

2. Autocorrelation Plots 

3. Trace Amplitude Analysis 

4. Trace Blanking 

I 

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1 

I 

APPLY THE FOLLOWING PROCESSES AFTER 

DATA AND VELOCITY ANALYSIS 

1. mank out refracted data 

2. Apply normal-moveout corrections 

3. Band-pass filter 6-55 Hz. 

4. Trace-Amplitude Adjustment 

s. Stack 

DISPLAY 

Preliminary 

stack section 

APPLY THE RlLLOWING PROCESSES AFTER 

CHECKING QUALITY OF PRELIMINARY STACK 

1. Predictive Deconvolution 

2. Time-Varying Bandpass Filter 

(Filter cutoff points dependent on 

location of data) 

3. Final Amplitude Adjustment 

DISPLAY 

Final Stack 

Section FINAL FILM 

PLOT Of 

STACK SECTION 

PAPER COPIES MADE 

FOR DISTRIBUTION 

DEMULTIPLEX 

1. Apply gam function 

2. Define shooting receivtng 

geometry 

3. Edit out bad data 

1. Select Traces for 

Velocity Analysis and 

near-trace gathers. 

2. Apply Filtering and 

Amplitude AdJL!Stment 

VELOCITY ANALYSIS 

DISPLAY 

Near-Trace 

Secuon 

r----------------- ----------------------, 

NO-DIP AREAS 

VELOCITY SPECTRUM 

Select 3 COP's 

every 200 COP's 

t 

DISPLAY 

Velocity-Spectrum 

Plots 

GENTLE-DIP AREAS 

VELOCITY SPECTRUM 

Select 3 COP's 

every 100 COP's 

~ DISPLAY 

Veloc1ty-Spectrum 

Plots 

DIS Y 

NMO Carr ed COP and/or 

s t gathers 

STEEP-DIP AREAS 

CONSTANT VELOCITY 

STACK 

Select 8 COP's 

every 40 COP's 

• DISPLAY 

Constant-VelocotvStack Plots 

---------------------------· 

FIGURE 2.-Flow chart of the first-pass processing steps performed by the USGS on the multichannel seismic-reflection profiles 11, 

12, and 13 (fig. 1). Designations used: CDP, common depth point; NMO, normal moveout. 

5 
such as correlation between frequency content of a 

reflection and geologic characteristics. 

The velocity-analysis phase (fig. 2) is important 

because the velocities used in computer computations greatly affect the quality of final seismic 

records. Velocities derived in this phase are used to 

compute normal-moveout (NMO) corrections prior 

to stacking. Stacking, or summing, the commondepth-point (CDP) traces increases the signal-tonoise ratio of the subsurface reflections so they can 

be mapped more easily. 

The two boxes on the flow chart (fig. 2) labeled 

"velocity spectrum" represent methods for deriving stacking velocities. Both methods involve scanning the reflection hyperbola and plotting reflection coherence as a function of velocity and time. 

In areas of steep dip, a constant velocity stack is 

used; the procedure consists of stacking a short 

segment of the data at various constant velocities 

and then visually choosing the velocity that best 

corrects the data at the different times. 

In the application phase, the data are stacked 

and predictive deconvolution filtering and bandpass filtering are applied. Predictive deconvolution 

is a procedure for attenuating water-bottom 

multiples, which can interfere with primary reflections. Water-bottom multiples result from energy 

being trapped between the air-water interface and 

the water-sediment interface. Reverberation 

removal has been very successful for lines on the 

shelf where the water is shallow. In deeper water 

(greater than 500 m), predictive deconvolution is 

less effective, and other methods have been devised by the USGS to attack this problem. The most 

effective method to date has been to weigh (on the 

basis of wave amplitude) the individual traces prior 

to stacking to enhance the NMO discrimination of 

multiple reflections during the stacking process. 

Finally, a band-pass filter and a final amplitude 

adjustment are applied to the data before the final 

display. The resulting section is an amplitude-and 

frequency-balanced seismic time section showing 

geologic information that has been separated from 

seismic noise. Relative amplitude changes have 

been preserved on the section to allow interpretation of amplitude information; in recent years, 

amplitude information has been used to locate 

changes in rock composition, porosity, and layer 

thickness and to identify contained fluid. 

Special processing was performed on lines 2, 3, 

and 9 by Digicon Geophysical Corporation to improve the continuity of reflectors, both shallow and 

6 

deep. This processing involved computing velocity 

analyses every 1.6 km or every 0.8 km where structural changes were detected, and computing a better deconvolution operator and filter. Final rootmean-square velocities were contoured and reevaluated to provide the best functions for stacking the data. Final stacked data were then 

migrated to put the data in a more realistic attitude. The final process was converting these time 

data to depth. 

GEOLOGIC SETTING 

By KENNETH C. BAYER and ROBERT E. MATTICK 

The lease tracts for proposed Lease Sale No. 49 

(fig. 1) are within the Baltimore Canyon Trough, 

an elongate northeast-trending sedimentary basin 

that was named by Maher (1965) for a nearby submarine canyon. The trough extends more than 600 

km between Long Island and Cape Hatteras and is 

arcuate but subparallel to the shoreline. It is widest 

(200 km) off New Jersey, where its sediment fill is 

thickest-14 km (Mattick and others, 1974; Schlee, 

Martin, and others, 1977). 

The geology of the Baltimore Canyon Trough is 

characterized by extensional tectonic features, a 

result of the splitting apart of an older supercontinent into the North American and African continents during the Mesozoic Era. In general, extensional margins or Atlantic-type margins are structurally simple in relation to their postrift sedimentary sequences. 

A diagrammatic cross section of the Baltimore 

Canyon Trough is shown in figure 3. Sheridan 

(1976, p. 118-120) listed 14 geologic features of offshore basins on the North American margin. 

Several of the features listed by Sheridan (1976) 

and additional ones, as interpreted by us, are 

described as follows: 

1. Breakup of basement into horst and graben 

structures during initial phases of rifting, 

probably during Triassic time: The westerly 

dip of faults beneath the slope and shelf edge 

suggests that continental breakup began 

beneath the midshelf area. Later, when rifting actually took place, the locus of the rift 

shifted eastward to a position at, or 

somewhat east of, the base of the present 

Continental Slope. 
Cl) 

a.:: 

w 

1-

w 

~ _, 

S2 

~ 

:i 

1-

D.. 

w 

0 

WEST COST No. B-2 well EAST 

o,---------------~=-------~-----'~--~~~--------~S~~~L~E~VE~L 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~w~~~~d~e~ 2 

4 

6 

8 

10 

interface 

7 

12 

11 

14 

EXPLA~ATION 

1. Pleistocene, Pliocene, and Miocene shallow marine to nonmarine deposits; chiefly unconsolidated sand containing shale in the basal part of the section. 

2. Oligocene marine shale and claystone that pinches out shoreward. 

3. Eocene and Paleocene marine deposits; chiefly dense argillaceous micrite and claystone. 

4. Upper Cretaceous deposits; chiefly marine sandstone and shale. 

5. Lower Cretaceous sedimentary rocks; chiefly alternating sandstones and shales of shallow 

marine to nonmarine origin; contains coal and lignite seams; grades into limestone at shelf 

margin. 

6. Lower Cretaceous shelf-edge reef. 

7. Jurassic sedimentary rocks; by analogy with Scotian Shelf, upper part consists chiefly of 

sandstone and shale, lower part consists chiefly of limestone. 

8. Jurassic carbonate bank deposit. 

9. Jurassic salt and evaporite deposits. 

10. Triassic deposits; chiefly continental lake and stream deposits. 

11. Slope deposits. 

12. Continental basement rocks. 

13. Mafic intrusion (Great Stone dome). 

14. Oceanic basement rocks. 

15. Basement rocks(?), uplifted and block faulted. 

FIGURE 3.-Diagrammatic cross section of the Baltimore Canyon Trough. Approximate length of section is 

200 km. 

7 
2. Deposition in grabens of Triassic nonmarine 

red beds, mudstone, shale, siltstone, arkosic 

sandstone, and fanglomerate: In outcrops 

onshore, these rocks are a heterogeneous 

mixture of stream, lake, and swamp deposits 

plus intrusive and extrusive volcanic rocks. 

3. Great subsidence of basement rocks to depths 

of 12-14 km since Triassic or perhaps Early 

Jurassic time: The subsidence is believed to 

be the result of cooling (Sclater and others, 

1971) and an associated increase in density of 

the deep crustal rocks. A controversy exists 

over how much rocks subsided at the present 

shelf edge. Some authors (Schlee and others, 

1976; Sheridan, 1976) believe that basement 

rocks are at a depth of 12-14 km beneath the 

shelf edge in the Baltimore Canyon Trough 

area. Other authors (Mattick and others, 

197 4) believe that the shelf edge is underlain 

by a high-standing basement ridge (6-7 km 

deep), behind which Jurassic sediments accumulated. On the basis of magnetic studies, 

Grow and Klitgord (this volume) believe that 

the shelf edge is underlain by an uptilted 

block of oceanic crust at a minimum depth of 

6-8 km. 

4. Deposition of evaporite beds in a narrow, 

shallow early Atlantic sea: Although this 

part of the section probably contains salt, 

authors differ in their opinions on whether or 

not a significant amount of salt flowed in the 

Baltimore Canyon Trough area; compare the 

opinions in this report of Poag, of Grow and 

Klitgord, and of Mattick and Girard. 

5. Thick accumulations of carbonate rocks in the 

Jurassic. 

6. Formation of Jurassic carbonate bank complexes under what is now the Continental 

Slope and edge of the Continental Shelf: The 

carbonate bank deposits may have formed 

above a basement ridge. 

7. Thick accumulations of Upper Jurassic 

through Oligocene sand and shale and subordinate amounts of limestone, coal, and 

lignite: This part of the section is primarily 

nonmarine to very shallow marine in origin. 

8. Reef growth along the then-existing shelf edge 

(under the present slope) in Late Jurassic 

and Early Cretaceous time. During Early 

Cretaceous time, the reef was exposed or 

nearly exposed and later, in Late Cretaceous 

time, it was buried by an influx of deltaic 

sediments. 

8 

9. Intrusive igneous doming during the last 

stages of the Early Cretaceous. 

10. Outward building of the Continental Shelf by 

progradation in the Miocene. 

Structure-contour and isopach maps on strong 

seismic-reflecting horizons are shown in figures 

4-8. Data from onshore wells and the COST No. 

B-2 well provided correlation for the seismic interpretation. The authors have more confidence in the 

seismic results from the Continental Shelf than in 

those from the slope and rise. We were able to tie 

together, by means of line 12 (fig. 1), the seismic 

profiles on the shelf. The strike profile across the 

rise (line 13, fig. 1), however, was not available. 

Some evidence exists for faulting, generally on the 

shelf margin and the Continental Slope, but 

because of the map scales, faulting is ignored. 

STRUCTURAL FRAMEWORK 

By JOHN A. GROW and KIM D. KLITGORD 

Our knowledge of the structural framework of 

the Outer Continental Shelf, Slope, and Rise 

depends primarily on four types of geophysical 

measurements: seismic refraction, seismic reflection, magnetic, and gravity. In this section, we 

review these basic data in order to define the major 

structural elements in the area of Lease Sale No. 

49 and infer their geologic evolution. 

SEISMIC-REFRACTION DATA 

Three early series of refraction surveys (fig. 9) 

were conducted off New York and New Jersey 

(Ewing and others, 1950; Drake and others, 1959; 

Ewing and Ewing, 1959). Analysis of these data indicated 5 km of low-velocity (less than 4.5 km/s) 

sedimentary rocks in the midshelf area. The lowvelocity layers are underlain by refracting layers 

having velocities greater than 5.3 km/s. Because 

velocities above 5.3 km/s correlated with basement 

rocks onshore, these higher velocity layers were 

also believed to represent basement rocks in the 

midshelf and outer-shelf areas (stations 85 and 86; 

Drake and others, 1959). However, on the basis of 

subsequent reflection studies, authors of later 

papers interpreted these high velocities as 

representing carbonate rocks in the midshelf area 

and carbonate bank deposits or reef complexes in 
EXPLANATION 

---200m---

_ _ _2 Seismic-reflection line 

0 Well location. See figure 1 for 

well names 

D lease sale No. 40 

D Lease sale No. 49 

25 50 

~ " 

" .,. 

"' ~ ~ ~ 

" (, 

0 

FIGURE 4.-Structure-contour map of the mid-Atlantic continental margin of the United 

States showing depth in meters to the top of Upper Cretaceous rocks. Datum 

is mean sea level. Contour interval is 100 m on the shelf and 500 m on the slope 

and rise. Dashed contours indicate data subject to change. 

9 
EXPlANATION 

--200m-- Isobath shown for 200 and 2000 m 

Seismic-reflection line 

0 Well looation. See figure 1 for 

well names 

D Lease sale No. 40 

D l.ea.se sale No. 49 

/ / 

FIGURE 5.-Structure-contour map of the mid-Atlantic continental margin of the United 

States showing depth in meters to the top of Lower Cretaceous rocks. 

Datum is mean sea level. Contour interval is 100m between water depths of 300 and 

2,500 ·m and is 500 m in water depths greater than 2,500 m. Dashed contours 

indicate data subject to change. 

10 
EXPlANATION 

--200m--

Seismic-reflection line 

0 Well location. See figure 1 for 

well names 

0 Lease sale No. 40 

0 Lease sale No. 49 

REPfiOCfSSING OF fHE OEEP-WATU 

SECTION Of liNE 11 ITO MINIMIZf 

MUlTIPlES). PlUS A TIE TO liNE 13 

ISH f iGUfiE l l. lS lfQUIREO TO 

EVALUATE THE ACOUSTIC 

IASfMENT IN THIS AREA . 

FIGURE 6.- Structure-contour map of the mid-Atlantic continental margin of the United 

States showing depth in meters to the top of the acoustic basement. Datum 

is mean sea level. Contour interval is 1,000 m, except along part of seismicreflection line 2 where the interval is 2,000 m. Dashed contours indicate data subject 

to change. 

11 
EXPLANATION 

- -200m--- Isobath shown for 200 and 2000 

Seismic-reflection line 

0 Well location . See figure 1 for 

well names 

c:::::J Lease sale No. 40 

c:::::J Lease sale No. 49 

~ " 

" "' "' ~ ~ " v (, 

0 

FIGURE 7.-Isopach map of the mid-Atlantic continental margin of the United 

States showing thickness of Lower Cretaceous and older sedimentary rocks 

above the acoustic basement. Contour interval is 1,000 m, except along part of 

seismic-reflection line 2 where the interval is 2,000 m. Dashed contours indicate 

data subject to change. 

12 
EXPlANATION 

- -200.,-- Isobath shown for 200 and 2000 m 

Seismic-reflection line 

0 Well location. See figure 1 for ·.<.: well names 

D Lease sale No. 40 ··:: 

D Lease sole No. 49 

FIGURE 8.-Isopach map of the mid-Atlantic continental margin of the United 

States showing total sediment thickness between the sea floor and the acoustic 

basement. Contour interval is 1,000 m, except along part of seismic-reflection 

line 2 where the interval is 2,000 m. Dashed contours indicate data subject to change. 

13 
41° ,----.-----:-:-T~y-:-::-r,;;;::;:;;;;;;~77~rt---, 

PENNSYLVANIA 

REFRACTION LINES 

7-16 

G-16 

83--86 

\ GS-2. 3. 4 

\500 

\ 

\ 

\ 

\'1000 

EWING AND OTHERS (1950) 

EWING AND EWING (1959) 

DRAKE AND OTHERS (1959) 

A. E. SHERIDAN 

( UNPUBLISHED OATA,1977) 

37°~--------~~-L~~~~--------~~------~~--------~ 760 730 720 710 

• • • • 

-200m0 

EXPLANATION 

Landward edge of Baltimore Canyon 

trough at approximately 5 km depth to 

basement contour 

Basement ridge at 6 to 8 km depth associated with East Coast Magnetic 

Anomaly 

Lease sale No. 49 blocks 

Isobath shown for 200 and 2000 m 

50 100 150 200 KILOMETERS 

FIGURE 9.-Map showing locations of seismic-refraction surveys discussed in text. The locations of some of the CDP 

multichannel seismic-reflection lines (fig. 1) are also shown (dashed lines) for reference. 

14 
REFRACTION LINES 

GS-2 GS-3 G-16 GS-4 

s. N. N. s. s. N. SEA LEVEL 0 0 

1.97 --- ........ 1.66 ........ 2.75 ........ WATER ........ 2.99 / --- --------- 4.75 ' / 1.66 / ' / ' ' SEDIMENTS 

5 5 

--------- 6.17? SEDIMENTARY 

--- -?- -?- 5.01 ROCKS 

5.46 " (/) 

a: ?" 

w 10 THICK OCEANIC -?- 10 - OCEANIC BASEMENT Iii LAYER 2 AND 3A (LAYER 2) ~ 

0 OCEANIC CRUST ...J 

i2 ---~YER2&_ _.. --- ~ ..- _.. 713 7.18 ~ 

..- _... OCEANIC CRUST 

(LAYER 38) -

..-

-- 15 

EWING AND 

EWING ( 1959) 

-- _... _... _... _.. _... 8.28 MANTLE 

50 100 

25~--~----------~--------~----------~--------~--------~25 

DISTANCE, IN KILOMETERS 

FIGURE 10.-Cross sectic-n from outer shelf to rise based on recent seismic-refraction surveys (R. E. Sheridan, unpub. data, 1977). 

Velocities are shown in kilometers per second. See figure 9 for locations of sections GS-2, 3, and 4 and G-16. 

the outer shelf area (Emery and Uchupi, 1972; 

Sheridan, 1974; Mattick and others, 1974; Mattick 

and others, 1977; Schlee and others, 1976; Schlee, 

Behrendt and others, 1977; Grow and others, 

1979). 

Three recent refraction lines (GS-2, GS-3, and 

GS-4) are near the intersection of the earlier· 

refraction work and CDP line 2 (fig. 9). The results 

from the analysis of these lines confirm earlier interpretations of stations 83-84 and 85-86 by 

Drake, Ewing, and Sutton (1959) and extend the 

7 .13-km/s horizon reported by Ewing and Ewing 

15 

(1959) at profile G-16 (fig. 10). This layer has 

velocities of 7.13-7.19 km/s (fig. 10) and is inferred 

to represent oceanic crustallayer.3B as defined by 

Sutton, Maynard, and Hussong (1971). Because 

reflection data along CDP line 2 near GS-4 (figs. 

11, 12) indicate that sediments extend to a depth of 

more than 9 km, the 5.01-km/s refractor at GS-4 

must represent a high-velocity sedimentary 

horizon on the Continental Slope. Refracted arrivals from oceanic basement (layer 2 having 

velocities between 5.46 and 6.5 km/s) and oceanic 

crust (layer 3A having velocities between 6.5 and 
DISTANCE, IN KILOMETERS 

0 17! I 250 SEA LEVEL 

0 0 V) 

1:111:: 1.9±.1 T w 

..... 

w 

~ 

0 Acoustic basement ..... -....... 

S2 " \ \ 

z ? '? 

~ ?--~-

..... I 

Ill.. Oceanic w 

0 500 1000 1500 2000 2500 basement 3000 

15 15 

SHOTPOINT NUMBER 

A 

KILOMETERS 

0 150 SEA LEVEL 

or-~~======~~~~==~~----------~----------~----------~--.o 

200 250 

V) 

1:111:: 

w 

tw 

~ 

0 

..... 

S2 

z 

:I: 

~ w 

0 

' , .... ' 

,','' I 5.9t.2 

I ' - I I 

Acoustic ' .... - - I ~ 1 

basement(?) ~~r:;L~~~-- " 

52:t .4 

500 1000 

2.01.1 

1500 

T 

? 

2000 

l8tJ 

10 

2500 

SHOTPOINT NUMBER 

8 

FIGURE 11.-Line drawings showing strong reflectors, interval velocities, and inferred ages of horizons interpreted from seismicreflection profiles. A, Profile 9. B, Profile 10. C, Profile 6. D, Profile 2. Locations of profiles are shown in figures 1 and 9. 

Velocities of the units (between dashed vertical lines) are shown in kilometers per second, and the mean standard 

deviation is shown by ±. Designations used: T, Tertiary; UK, Upper Cretaceous; LK, Lower Cretaceous; A, strong seismic 

reflector mappable throughout the Atlantic basin. The Lower Cretaceous mafic intrusion is called the Great Stone dome. 

Reflectors are dashed where inferred. 

7.0 km/s) apparently were not recorded at GS-4. 

Perhaps arrivals from a deeper 7.18-km/s layer 

masked the arrivals from layers 2 and 3A. A mantle velocity of 8.28 km/s was also detected at GS-4 

at a depth of about 20 km. 

The refraction data support the following conclusions: 

16 

1. Along the inner shelf, the shallow 5.3-6.0-km/s 

refractors represent continental basement 

rock. 

2. Along the midshelf to outer shelf and upper 

slope, between the depths of 2.6 and 6.0 km, 

the 4.8-5. 7 -km/s refractors represent Lower 

Cretaceous and Upper Jurassic carbonate 

rocks. 
en 

a: 

w 

1-

w 

~ 

0 

....1 

~ 10 

z 

It 

w 

Cl 

en 

a: 

w 

1-

w 

~ 

0 

....1 

~ 

z 

I 

1-

fri 

Cl 

0 

5 

10 

500 

~ ? 

--.. 

1000 " 

150 50 

VERTICAL EXAGGERATION X5 

IN All PROFILES 

l I 

101 500 

DISTANCE, IN KILOMETERS 

150 200 250 SEA LEVEL O 

T 

: ~Sci~~~======~~~.e~~·EI ~::~ ====~~~====~l.e~~g. A? 3~.2 ~==~==~ 5 4.3~ 2 2.8:!:.3 

--?-- 4.3~.5 

5.3±.3? 

10 ?------- \ 

Oceanic basement 

15 

1500 2000 2500 3000 

SHOTPOINT NUMBER 

c 

5.0 REFRACTORS SEA LEVEL 

-----? ? ........ , Acoustic 

basement 

100 

DISTANCE, IN 

I 

150 

KILOMETERS 

I 

200 250 

1000 1500 2000 2500 

SHOTPOINT NUMBER 

D 

FIGURE 11.-Continued 

3. Oceanic crustal layer 3B having a velocity of 

7.13-7.19 km/s dips gently landward and can 

be traced to a depth of about 15 km beneath 

the outer edge of the Continental Shelf. 

5. The 5.87- and 6.17-km/s arrivals on lines GS-2 

and GS-3 are poorly defined arrivals, and we 

do not know whether they represent highvelocity sedimentary rocks or basement rocks. 

4. The top of oceanic basement (layer 2) cannot be 

clearly defined near refraction lines GS-2, 

GS-3, and GS-4. 

6. High velocities, indicative of basement rocks, 

have not been measured by seismic-refraction 

surveys in the central Baltimore Canyon 

Trough area. 

17 
t-' 

00 

Cl) TOP 

a: 

w 

1-

w 

~ 

0 

....1 

5;2 

z 

:I: 

1-

0.. 

w 

0 

NORTHWEST 

1500 SEA LEVEL 

SHOTPOINT 

1700 1800 1900 - - j _____ ------- I 

LOWER CRETACEOUS 

SHELF EDGE 

6 ~~-·_ .·-=~~~-. :• :~ ::;-::~· ~;::~~~; :-.. ·~·:;:~:S~--~ ~ 

- ( 

VERTICAL EXAGGERATION X2 

0 5 10 KILOMETERS 

SOUTHEAST 

2000 

L --0 

FIGURE 12.- Part of CDP multichannel seismic profile 2 having vertical scale in depth. Location of profile 2 is shown in figures 1 and 9. Designations used: LK, Lower 

Cretaceous; K, Cretaceous; J, Jurassic; A and {3, strong seismic reflectors mappable throughout the Atlantic basin. 
MULTICHANNEL SEISMIC-REFLECTION DATA 

The seismic-reflection data from the Baltimore 

Canyon Trough area (lines 2, 6, 9, and 10; see figs. 

1 and 9 for location) are summarized in figure 11. 

Lines 2, 6, and 10 reveal two major sedimentary 

troughs; one beneath the shelf contains at least 12 

km of sedimentary rocks, and a second is beneath 

the upper Continental Rise where the sedimentary 

rocks are at least 9 or 10 km thick. The shelf and 

rise sediment troughs are separated by an 

acoustically opaque feature interpreted to be a 

ridge whose top ranges from 3 to 6 km below sea 

level. 

The parts of the four profiles over the outer shelf , 

edge and upper Continental Slope near the possible 

ridge were converted from two-way travel time to 

depth below sea level (figs. 12-15). Both the time 

and depth sections are shown for line 6 (fig. 13). 

The strong reflector at a depth of about 3 km 

beneath the shelf edge apparently represents the 

top of the Lower Cretaceous section. The diffraction pattern at a depth of 3.5 km near shotpoint 

1480 is probably associated with the edge of the 

Lower Cretaceous shelf. A major unconformity is 

beneath the present upper rise, where Tertiary rise 

sediments overlie the Lower Cretaceous shelf 

margin (fig. 13). The present shelf edge appears to 

be about 20 km landward of the Lower Cretaceous 

shelf edge. The seismic record suggests that block 

faulting and arching of Lower Cretaceous horizons 

between shotpoints 1380 and 1500 took place near 

the end of Early Cretaceous time. 

At a depth of 12 km beneath the shelf, the depth 

section for line 10 (fig. 14) shows a series of strong 

reflections that may represent basement rocks. 

Alternatively, its smooth continuous character between shotpoints 800 and 950 suggests that it 

represents sedimentary units that may contain 

alternating evaporite and carbonate sequences 

(see Schlee, this volume). The apparent seaward 

dip of these deep reflectors between shotpoints 950 

and 1000 may not be real but rather may result 

from diffraction. The top of Lower Cretaceous 

strata along line 10 is also marked by a strong 

reflection at about 3 km depth, and a rotated fault 

block can be seen on the seismic record (fig. 14) 

between shotpoints 1130 and 1200. Beneath the 

Continental Rise (between shotpoints 1100 and 

1300), a marked unconformity is present, and 

coherent reflections are absent at depths greater 

than 6 km. 

19 

On line 2 (fig. 12), reflectors of unusually high 

amplitude appear at a depth of 2.6 to 4.0 km between shotpoints 1500 and 1700. The lowest of 

these reflectors correlates with the top of the 

Lower Cretaceous section in the COST No. B-2 

well. Although refraction velocities for this unit 

range from 4.8 to 5.3 km/s, the interval velocity, as 

calculated from reflection records, averages about 

4.2 km/s (fig. 11). This difference in velocity as 

measured by the two different seismic methods 

could indicate an alternating sequence of high~ and 

low-velocity beds-the high velocities representing 

carbonate units and the low velocities representing 

sands and shales. The irregular reflectors at depths of 3-6 km at shotpoint 1750 (fig. 12) apparently 

represent a reef complex of Early Cretaceous and 

Late Jurassic age (Schlee and others, 1976; Mattick and others, 1977; Grow and others, 1979). The 

landward-dipping reflectors (fig. 12) at depths of 

8-10 km between shotpoints 1800 and 2000 probably represent Jurassic turbidite deposits. The dip 

reversal could have resulted from differential subsidence rates between the shelf and the rise areas. 

The early shelf sediments have apparently subsided at least 12 km, whereas the early rise sediments 

(probably deposited in 2-4 km of water) may have 

subsided only 6 km. (Compare this interpretation 

for the dip reversal with the interpretation involving growth faults by Mattick, Scholle, and Girard 

(this volume).) The absence of coherent reflectors 

deeper than 6 km and the presence of magnetic 

sources between 7 and 8 km depth (see "Magnetic 

Data," this section) could be explained by a highstanding block of oceanic basement rock, a 

volcanic ridge, or a faulted sedimentary complex 

pervaded by mafic dikes and sills (during the Early 

Cretaceous?). The magnetic data suggest that the 

explanation involving oceanic basement rocks is 

the most likely. 

The depth section for line 9 (fig. 15) indicates 

that the Lower Cretaceous shelf edge is at a depth 

of 3 km near shotpoint 1700. Beneath the rise 

(shotpoint 1800), the strata appear to dip landward, as on line 2. Some irregular reflections are 

from strata at 7-10 km depth beneath the shelf, 

but they appear much more broken up than on lines 

2, 6, and 10. We do not know whether the broken 

character of these deep units is typical of the area 

near line 9 or reflects poor data quality on this particular line. The change in character northward 

from line 2 to line 9 is probably due, in part, to the 

transition out of the main sediment trough beneath 
A 

B 

c 

....1(/) 

wo 

>z :!o 

t-U w ~V) 

~~ I 

ow 

~~ .......... 

(/) 

0::: 

w 

..... 

w 

~ 

0 

..... 

~ 

z 

:I: 

..... 

Q.. 

w 

0 

(/) 

0::: 

w 

..... 

w 

~ 

0 

..... 

~ 

z 

' :I: 

..... 

Q.. 

w 

0 

NORTHWEST SHOTPOINT NUMBER SOUTHEAST 

14 

4.51 4.58 

5.13 

6 

v~~~--------------------.-----------~----------~8 1200 1300 

VERTICAL EXAGGERATION X2 

0 5 

1400 I 00 1600 

10 KILOMETERS 

FIGURE 13.- Part of CDP multichannel seismic profile 6, which crosses the Continental Slope. Location of profile 6 is 

shown in figures 1 and 9. A, Seismic profile having vertical scale in two-way travel time. B, The seismic profile having 

vertical scale in depth. C, Section showing computed interval velocities (in kilometers per second) and inferred ages of 

horizons. Designation used: A and (3, strong seismic reflectors mappable throughout the Atlantic basin. Segment of 

line marked by asterisks defines major unconformity. 

20 
the New Jersey shelf up onto the Long Island platform, where a narrower and shallower trough is 

present along the outer shelf. 

Velocities recorded in the COST No. B-2 well 

(Scholle, 1977b) are in good agreement with the interval velocities calculated from the seismic data in 

that vicinity (fig. 16). However, the 4.8-5.3-km/s 

refraction horizons detected at a depth of 2.6-3.9 

km near stations GS-2, GS-3, and 85-86 (figs. 9, 

10) can be traced on seismic section~ to Albian and 

Aptian units penetrated in the COST No. B-2 well 

where lower velocities of 3.5-4.3 km/s were 

measured. Our calculations, therefore, indicate 

that the velocities of the Albian and Aptian units 

increase southeastward from the COST No. B-2 

well. This trend suggests a lateral change in facies. 

The presence of refraction velocities that are 

10-15 percent faster than the interval velocities 

calculated from the reflection data is common 

along the U.S. Atlantic margin and may be explained by the alternation of high- and low-velocity 

beds as seen in the velocity logs from the COST 

No. B-2 well (fig. 16). 

MAGNETIC DATA 

Early aeromagnetic and shipboard magnetic 

data identified a conspicuous positive anomaly 

along the outer shelf and slope. This anomaly is 

referred to as the East Coast Magnetic Anomaly or 

Slope Anomaly (Keller and others, 1954; Drake 

and others, 1963). Taylor, Zeitz, and Dennis (1968) 

published a magnetic map contoured at an interval 

of 100 nanoteslas (nT; a nT = 1 gamma); the map 

showed that the inner Continental Shelf is 

characterized by short-wavelength anomalies suggestive of shallow basement. The outer shelf and 

Continental Rise are characterized by longer 

wavelength anomalies suggestive of deeper basement. Taylor, Zeitz, and Dennis (1968) also modeled the East Coast Magnetic Anomaly. These 

authors inferred a 30-km-wide vertical intrusive 

body that rises to a depth of about 7 km beneath 

the sea floor. 

A recent high-sensitivity aeromagnetic survey 

along 185,000 km (fig. 17) has been interpreted by 

Klitgord and Behrendt (1979). Estimates of the 

depths to the sources of the magnetic anomalies 

were computed along all the profiles of this survey 

(Hartman and others, 1971; Jain, 1976) by using 

the Werner deconvolution method (Werner, 1953). 

In this method, the anomaly is assumed to be due 

either to a vertical interface (edge model), or to a 

21 

100-m-wide dike alined normal to the magnetic 

profile direction (fig. 18). The depth to the top of 

source and the susceptibility contrast between op-

, posite sides of the interface, or between the dike 

and its surrounding material, can then be determined from a set of least-squares solutions of two 

truncated series that are calculated for several 

complete passes of a sampling window over the 

data set. On each pass, a wider sampling window 

and appropriate low-pass filtering are used to 

search for deeper sources. 

The depths, as calculated from the magnetic data 

recorded on the shelf, show that the edge solutions 

were in closest agreement with the seismic data 

(figs. 19, 20). This solution is compatible with the 

suggestions that, in this region, the basement is 

composed of large blocks of continental crust having various susceptibilities (Taylor and others, 

1968; Rabinowitz, 1974; Schlee and others, 1976). 

On the seaward side of the East Coast Magnetic 

Anomaly, where the acoustic basement is probably 

oceanic crust (Mayhew, 1974; Sheridan, 1974; 

Schlee and others, 1976), the depth to the magnetic 

source was best estimated by the dike solutions. In 

addition to the depth estimates associated with 

crystalline and (or) igneous basement, a consistent 

set of solutions for shallow magnetic sources having weak susceptibilities was computed both landward and seaward of the East Coast Magnetic 

Anomaly. These sources apparently are in the 

sedimentary column and may be associated with 

strong seismic horizons (figs. 19, 20). The weak 

susceptibility contrasts associated with these 

anomalies suggest that their sources are neither 

crystalline nor volcanic rock. Their consistent appearance on adjacent magnetic profiles and their 

association with strong seismic horizons suggest 

that the anomalies are real, but further discussion 

of them at this time would be beyond the scope of 

this paper. 

Similarly, for areas bounded by the East Coast 

Magnetic Anomaly, we calculated many estimates 

of depth to magnetic basement being greater than 

10 km together with a set of estimates of magnetic 

basement being shallow- 6-8 km below sea floor. 

The susceptibility contrast associated with the 

magnetic anomalies interpreted to represent 

shallow (6-8 km) magnetic basement suggests that 

their source is most likely a ridge of magnetic basement rocks (fig. 19, 20). The seismic profiles do not 

show any identifiable structures below this 

magnetic basement high, but in most profiles, a 

disturbed seismic zone has been interpreted as 
!:-:> 

!:-:> 

(/) 

a:: 

w 

t1i 

~ 

0 

...... 

:;;:: 

z 

I. 

1-

~ 

w 

Cl 

NORTHWEST 

TOP OF K 

BASEMENT and (or) 

CARBONATE and EVAPORITE DIFFRACTION (?) DEPOSITS 

VERTICAL EXAGGERATION X2 

0 5 10 KILOMETERS 

FIGURE 14.-Part of CDP multichannel seismic profile 10 having vertical scale in depth. Location of profile 10 is shown in figures 1 and 9. Designation used: 

K, Cretaceous. 
t-.:l 

~ 

en 

a: 

w 

1-

w 

~ 

0 

::::! 

::.::: 

z 

:t: 

1-

a.. 

w 

Cl 

NORTHWEST 

1400 

K(?) SHOTPOINT NUMBER 

1500 I 

LOWER CRETACEOUS 

SHELF EDGE 

SOUTHEAST 

()10£"'?! ~~ 14 

VERTICAL EXAGGERATION X2 

0 5 10 KILOMETERS 

FIGURE 15.-Part of CDP multichannel seismic profile 9 having vertical scale in depth. Location of profile 9 is shown in figures 1 and 9. Designations 

used: K, Cretaceous; LK, Lower Cretaceous. 
.t-:> 

~ fJ) 

"' w 

1-

w 

~ .... 

i2 

~ 

:i 

1-

"-w 

c 

0 

2 

3 

4 

VELOCITY, IN KILOMETERS PER SECOND 

2.0 3.0 4.0 5.0 --,0 

I ~ .-----------------

2 

3 

/ 

INTERVAL VELOCITIES 

USGS LINE 2 (SHOTPOINT No. 1200) 

4 

5' I 1 1 I I I 1 1 I I I I I 1 I I I I 1 I I I I I I I I I I I I I I I I 5 

~ 

~ 

:;;; 

w 

... 

"' w 

.... 

.... 

:::> 

~ .... 

~;:; 

"' u 

"' w 

.... 

.... 

:::> 

If) 

::> 

0 

"' 0 

~ 

"' a: 

0 

a: 

"' ~ 

0 

..J 

SYSTEM, 

SERIES, 

OR STAGE 

------

MIOCENE 

-

OliGOCENE 

EOCENf 

PALEO. 7 

lMES. ~ 

CAMPANV.N 

SANTONIAN AND - CONIACIAN 

TURONIAN 

CENOMANIAN 

AlBIAN 

APTIAN -

BARREMIAN AND 

VAlANGINIAN 

BERRIASIAN 

-

UPPER 

TO LOWER 

JURASSIC 

AGE, IN MILLIONS OF YEARS 

o_,Q 50 100 

RATES 0 B SEDIMENTATION , .. _ .. 

•\ RATES AT 

COST No. S--2 

WELL 

SLOW 

=====:~.~ /ODS 

=============~~~~\~ 

10 

20 

30 

2 +_------- -- -- ------- --."' •"-....100 

::::::::::::::::=:::::::o.~\ '+------------------------- ---~60 

40 

50 

1500 

fJ) 

2 "' ~ w 

~ .... 

i2 

z 

3 i!= 

"- w 

c 

--------------------------------·""" 

4+ \ 

4 

? 

5 5 

FIGURE 16.- Velocities and deposition rates at the COST No. B-2 well site. A, Velocities recorded on sonic logs from the COST No. B-2 well and velocities calculated from 

seismic-reflection data. B, Deposition rates in the COST No. B-2 well. The age-versus-depth data are taken from Scholle (1977b), except for the top of the Jurassic, which 

has recently been revised (E. Robbins, oral commun., 1978). Designations used: Paleo., Paleocene; L. Tert., Lower Tertiary; Maes., Maestrichtian; Cret., Cretaceous. 
I::'V 

01 

7SO 

77" 

37° 38° 3«r 

)( 

)( 

)( 

)( 

)( 

~ 

36° 

40° 

)( 

41° 

EXPLANATION 

© Magnetic anomaly contour-Contour 

interval 50 nanoteslas. Hachures 

indicate areas of lower magnetic 

, intensity 

.. riOOm-r' Bathymetric contour, in meters I 

)( /'t40° 

FIGURE 17.-Aeromagnetic anomaly map of the Baltimore Canyon Trough area. Survey was flown in 1975 by LKB Resources, Inc., under contract to the USGS. 

75° 

74° 

72° 
representing carbonate rocks above this high 

(Schlee and others, 1976). 

A contour map of depth to magnetic basement 

rocks is shown in figure 21. The controls for this 

map are the estimates of depth to magnetic basement and the seismic-reflection data. Reference to 

figure 21 suggests that intrusive bodies underlie 

the mapped area. The most prominent of these 

bodies is the Great Stone dome at about lat 39.3° 

N., long 73° W. (Schlee and others, 1976), which is 

crossed by seismic line 2 (fig. 11). The map suggests that other intrusive bodies could be near 

Cape Charles and Cape Henry; these would be near 

the edge of the Baltimore Canyon Trough and may 

have been intruded into older continental crust. 

The estimates of depth to magnetic basement are 

of parj;icular interest in the vicinity of the shelf 

break and the East Coast Magnetic Anomaly 

because the seismic technique has not been able to 

penetrate more than 6 km in this region. Depth 

estimates obtained in this region range from about 

7 km to more than 12 km. The magnetic basement 

is estimated to be at greater depths both landward 

and seaward of the East Coast Magnetic Anomaly. 

Many of the estimated shallower depths to 

magnetic basement are at about the same location 

as the conspicuous truncation of seismic reflectors. 

The calculated susceptibility contrasts are about 10 

x 10-4 Gauss per oersted (G/Oe), which is lower 

than the contrast calculated for the Great Stone 

dome (25 x 10-4 G/Oe). Basement is calculated to 

be about 10.5 km deep on the seaward side of the 

East Coast Magnetic Anomaly. The greatest 

depths to basement (12-13 km) are estimated to be 

landward of the East Coast Magnetic Anomaly. 

"Edge 

Model" 

CD contrast 

I 

z 

Flight level 

FIGURE 18.-Edge and dike models assumed in making magnetic depth estimates using the Werner (1953) deconvolution 

method. In the mathematical calculations, the right siqe of the 

edge model and the bases of both models were considered to 

extend to infinity (ex). 

26 

GRAVITY DATA 

Early marine gravity measurements along the 

U.S. Atlantic margin were made by using pendulum systems aboard submarines (W orzel and 

Shurbet, 1955; Worzel, 1965). The improvement of 

surface-ship gravimeters led to a rapid increase in 

the quality and quantity of data collected in the late 

1960's, and free-air anomaly maps of the continental margin at contour intervals of 20 and 25 mGal 

(milligals) were published by Emery and others 

(1970) and Rabinowitz (1974). More recent U.S. 

Navy and USGS gravity data have been compiled 

into a free-air anomaly map contoured at an interval of 10 mGal (Grow and others, 1976). The freeair anomalies over the continental margin near 

Lease Sale No. 49 are shown in figure 22. 

The change in topography, crustal type, and 

crustal thickness across a continental margin, even 

one in perfect local isostatic balance, results in a 

positive free-air anomaly along the shelf edge and 

an adjacent negative anomaly along the base of the 

slope (fig. 23). The magnitude of this edge effect at 

the boundary between thick continental crust and 

thin oceanic crust varies depending on the change 

in crustal thickness .and the abruptness of change, 

but typical values are +50 mGal at the shelf edge 

and - 40 mGal at the base of the slope for an 

Atlantic-type margin. 

Near Lease Sale No. 49, free-air-anomaly values 

change abruptly along the margin southeast of 

Delaware Bay and southeast of Atlantic City (fig. 

22). The mafic intrusion interpreted on seismic line 

2 (fig. 11) as the Great Stone dome was a site for intense bidding during Lease Sale No. 40. It is 

characterized by a small, circular + 18-mGal 

anomaly (fig. 22). Another + 10- to +23-mGal 

elongate high runs north-northeast through 

western Long Island and is thought to be 

associated with a high-standing basement block 

between two Triassic grabens- one along the Hudson River and the other along the Connecticut 

River. Northeast of the Great Stone dome is a 

triangular low having values between - 20 and 

- 29 mGal. On the shelf southeast of Long Island, 

anomalies are generally between 0 and -10 mGal, 

and a few small positive values are as much as + 5 

mGal. 

The free-air minimum along the Continental 

Slope between Hudson and Wilmington Canyons is 

extremely low ( < 60 mGal). This minimum is not 

related to an anomalously thick sequence of 
50 

-so 

SEISMIC LINE 9 

NORTH-NORTHWEST 

EAST COAST MAGNETIC ANOMALY 

DISTANCE, IN KILOMETERS 

50 100 l!>o 200 

SOUTH-SOUTHEAST 

0 

~---400 

250 SEA LEVEL 300

0 OCEAN 

5 

10 

Oceanic basement 

1500 2000 2500 

15 j_ __ _:~---~~--_:_::::c::... __ ___::....=..c...::__ ____ ~-=-=-==~~15 

SHOTPOINT NUMBER VERTICAL EXAGGERATION X5 

3000 

25 

Cl) 

a.:: 

w 

1-

w 5 ~ ..... 

~ 

~ 10 r. 

~ w 

0 

15" 

MAGNETIC ANOMALIES 

SEISMIC LINE 2 

NORTHWEST 

SOUTHEAST O 

w 

~ ~~~~~~~~~~~~-----------~~~~--------------,-200 ~ 

~ 

10 

101 15 

SHOTPOINT NUMBER VERTICAL EXAGGERATION X5 

FIGURE 19.-A comparison between seismic-reflection data (lines 9 and 2, figs_ 1 and 9) and magnetic depth estimates. The magnetic 

susceptibility contrast symbols used on top figure also apply to bottom figure. LK, Lower Cretaceous; UK, Upper Cretaceous; 

T, Tertiary. Solid circles, triangles, and squares represent depth estimates that had more than 50 solutions. Open circles, 

triangles, and squares represent depth estimates that had fewer than 50 solutions. 

27 
NORTHWEST SOUTHEAST 

"' _, 

<C( 

C> 

:::; 

_, 

i 

"' 1¥ 

w 

1-

w 

~ 

0 

.... 

~ 

~ 

:i 

1-

D. 

w 

a 

50 

0 

-so 

5 

10 

15 

AST COAST MAGNETIC ANOMALY SEISMIC LINE 6 

0 

~ 

"' w ==~~--------~----~--~------~~---, -zoo 5 

FREE-AIR GRAVITY ANOMALIES~ •••• • • o o• • 

0 

• 

0 

• • • z 

. . . . . .. .. . . . ~ 

LK T 

•. .. .. . . ..... . DISTAN~e:· iN .• Kita~ETERs 150 200 

• 7 _ _. • • 

·-------.. 

ul~~ ~~~~~~~~''' 1111 . ? 1:

. 

1

? 

111 11111 11 i 

1111111 11111\11~111111111111111? lllllllll ? 111111 ~~~~~ ~ ... ··:~~~~~rrm~mmrT7'1 1 ~' ______ Ocean1c basement 

' '-...verystr TN MAGNETIC 

'- ......._ reflectors ' SUSCEPTIBILITY CONTRASTS 

, - ........._ 7 o .• o-3} ....._ • 1::::.. ,& >3 -10 X 10-4 G,t>e .---,....,., 0 ,. > 10 

500 1000 1500 2000 2500 3000 

VERTICAL EXAGGERATION X5 

SHOTPOINT NUMBER 

-400 

5 

10 

15 

NORTHWEST SOUTHEAST 

EAST COAST MAGNETIC ANOMALY 

50 SEISMIC LINE 10 0 

"' _, 

<C( 

C> 0 :::; 

_, 

~ 

-50 

0 50 

0 

"' ac: 

w 

1-

w 

~ 5 0 

.... 

S2 

~ 

:i 10 1-

D. 

w 

0 

~~~ o---

' -~ 0 

""'~ ,',~' ~I IIi I •7 . -- ~1111111111111111111111 • 

Acoustic ')' I• 7\111111111111111171111111111111\lllllll r---....---._,, 10 

basement (?Yvery str~ ';!JIIIlllrTntlt..l 1111111111111111111111111? 11111111111111111111111 • • - __/'"""Oceanic 

reflectors . '

11 1 \%7 ? .../" ~ - basement 

500 lObo 1500 2000 2500 15·~------~----------~--------~----------~--------~------15 

SHOTPOINT NUMBER 

VERTICAL EXAGGERATION X5 

FIGURE 20.-A comparison between seismic-reflection data (lines 6 and 10 in figs. 1 and 9) and magnetic depth estimates. The magnetic susceptibility contrast symbols used on top figure also apply to bottom figure. LK, Lower Cretaceous; UK, Upper 

Cretaceous; T, Tertiary. Solid circles, triangles, and squares represent depth estimates that had more than 50 solutions. Open 

circles, triangles, and squares represent depth estimates that had fewer than 50 solutions. 

28 
37° 

)( 

78° 

• 

77° • 

~ 76° 

75° 

39° 40° 

)( 

• 

eK 

38° 

0 20 40 60 STATUTE MILES I I I I I I I I 

0 2tl 40 60 fll KilOMETERS 

41° 

EXPLANATION 

~ Depth to magnetic basement, in kilome- 1

750 ters below sea level. Hachures indicate a basement low 

_,-1- Depth to Triassic and Paleozoic basement, in kilometers 

• Well drilled to Triassic and Paleozoic 

basement 

. ~~0: ~ Drill site 

··· .. ·-Joom .... Bathymetric contour, in meters 

FIGURE 21.-Contour map showing estimated depth to magnetic basement in the Baltimore Canyon Trough area. Contour interval is 1 km. 
42°r-----------.----------,----------~----------~----------~ 

EXPLANATION 

Contour interval, 10 mGals 

.··200m ... Bathymetry contour, in meters 

KILOMETERS 

L ;3,0 

Based on USGS Mep MF-795 by 

Grow and others (1976) 

PENNSYLVANIA 

100 I NEW 

YORK 

FIGURE 22.- Free-air gravity map of the Baltimore Canyon Trough area. 

30 
LOCAL AIRY ISOSTATIC GRAVITY ANOMALIES-WITHOUT SEDIMENT CORRECTION 

+50 ....... ········.\_..-THEORETICAL ISOSTATIC MODEL (8) 

--~···· : •••• ····················- ~ OBSERVED FREE-AIR GRAVITY ANOMALIES (A) 

(/) 10 a:: 

w 

.... 

w 

~ 

g 

S2 

~ 

~ 20 w 

a 

MANTLE p=3.3 

0 50 150 

DISTANCE, IN KILOMETERS 

250 

FIGURE 23.- Gravity anomalies at the continental margin. Figure shows observed free-air gravity anomaly (A), theoretical gravity 

(B) calculated from an isostatically balanced model, and isostatic anomaly computed by subtracting A from B. Densities (p) are 

in grams per cubic centimeter. Location of gravity profile coincides with that of seismic-reflection profile 6 (fig. 22). 

sediments because seismic-reflection data Oines 2 

and 6) and depths to basement calculated from the 

magnetic data (fig. 21) indicate that the sediment 

thickness on the rise north of Hudson Canyon and 

south of Wilmington Canyon is about equal to the 

sediment thickness between the two canyons. 

Probably the Mohorovicic discontinuity is 1-2 km 

deeper between Hudson and Wilmington Canyons 

than elsewhere in the mapped area. 

For interpretation, Rabinowitz (197 4) has recommended the use of local Airy isostatic gravity 

anomalies across continental margins. Such 

isostatic profiles along seismic lines 2 and 6 are 

31 

shown in figures 24 and 25. Although these profiles 

were computed without correction for the sediment layer, ~abinowitz (1974) has shown that this 

correction does not significantly change the overall 

isostatic profile. The values on the isostatic profiles 

vary considerably along the margin. The anomalies 

south of line 6 are near zero; along line 6 off Cape 

May, a regional isostatic anomaly of - 30 to - 40 

mGal is interrupted by a strong, local high near the 

upper Continental Slope (fig. 25). To the north, 

along line 2, broad weak isostatic negative 

anomalies over the inner shelf and rise are 

separated by a weak broad high (fig. 24). 
NORTHWEST SOUTHEAST 

50 EAST COAST en~ ·_," LOCAL AIRY /MAGNETIC ANOMALY 0 •• 

v, ISOSTATIC GRAVITY v 

~ o~-----r------~~--~-----.. -... -.. -.. -.. -... -.. -.. -... ~ .. ~~~~--------------~-2ooi i ··........ ~ 

-50 COST No. B-2 Well LK 

SHELF 

5 -400~ SALT 

DIAPIR(?) 

MANTLE 

z 

T•TERTIARY 

K•CRETACEOUS 

30 

LK• LOWER CRETACEOUS 

J•JURASSIC 

"R•TRIASSIC 

0 VERTICAL EXAGGERATION X5 

DATUM IS SEA LEVEL 100 200 

DISTANCE, IN KILOMETERS 

FIGURE 24.-Geologic section across the ocean-continent boundary near seismic profile 2. Diapir projected from 10 km south of profile, and COST No. B-2 well projected from 10 km north of profile. 

The zone between the shelf and slope-rise areas, 

which is characterized by shallow seismic penetration (6 km) and shallow (8 km) magnetic sources 

(fig. 21), is marked by a local positive isostatic 

anomaly (figs. 24, 25) and the nearby East Coast 

Magnetic Anomaly. Various explanations for this 

anomalous area have been published. Taylor, Zietz, 

and Dennis (1968) proposed that the source of the 

East Coast Magnetic Anomaly was an igneous 

32 

body 30 km wide whose upper surface was about 7 

km below sea level. Rabinowitz (1974) proposed 

that the local isostatic high could be accounted for 

by high-density material within the basement. Mattick and others (1974) proposed that a basement 

ridge underlies the outer shelf edge, whereas 

Schlee and others (1976) proposed that a carbonate 

bank or reef complex underlies the area. Detailed 

gravity models of the zone between the shelf and 
NORTHWEST SOUTHEAST 

+50 EAST COAST 0 ~ 

~ i ~ or-----------~~--------~~==~~----------------------------------1-200~ 

~ ........... ............................. ........................................................... ~ 

.............................. \~ocAL AIRY 1sos"i'A'iic................. 5 

-50 GRAVITY ANOMALIES -400 ~ 

II) 

IX 

w 

1-

w 

~ ~ 

z 

10 

MANTLE 

EXPLANATION 

T10TERTIARY 

K•CRETACEOUS 

30 

LK= LOWER CRETACEOUS 

J: JURASSIC 

"R•TRIASSIC 

0 VERTICAL EXAGGERATION XS 100 300 DATUM IS SEA LEVEL 

DISTANCE, IN KILOMETERS 

FIGURE 25.-Geologic section based on interpretation of seismic profile 6, which crosses the ocean-continent boundary. 

slope-rise areas are in preparation. Preliminary 

results of these studies indicate that a high-density 

body must underlie the anomalous area between 

the shelf and rise, an interpretation that is consistent with Rabinowitz's (1974) observations. Highdensity carbonate rocks (3-7 km deep) may account for part of the gravity anomaly, but the 

magnetic data (fig. 21) seem to indicate that 

oceanic basement rocks are relatively shallow in 

this area. Therefore, the gravity anomaly probably 

is related to a ridge of oceanic basement rocks 

perhaps capped by high-density carbonate rocks. 

THE OCEAN-CONTINENT BOUNDARY AND 

SUBSIDENCE HISTORY 

The geophysical data are summarized in figures 

33 

24 and 25, which show interpreted geological cross 

sections along seismic lines 2 and 6, respectively. 

The landward edge of the oceanic crust is interpreted as the source of the East Coast Magnetic 

Anomaly. The oceanic crust is approximately 8 or 9 

km thick near the southeast end of the profiles, and 

it may thicken to 12-15 km near the East Coast 

Magnetic Anomaly. This model is consistent with 

the model of Rabinowitz and LaBrecque (1977), 

who proposed that oceanic crust is abnormally 

thick during the initial stage of continental separation. The continental crust is believed to have been 

thinned during rifting, but it may also have been 

intruded by basaltic flows, dikes, and sills. 

At least one diapir, believed to be salt, has been 

mapped on the shelf. In addition, at least seven 
other diapirs have been mapped seismically along 

the base of the Continental Slope off Cape Hatteras (Grow and others, 1977). Because these 

diapirs are not associated with measurable 

magnetic or gravity anomalies, they could be the 

result of salt flowage (Grow and others, 1977). 

Although diapirs along this part of the Atlantic 

margin are few, their presence could indicate that 

salt deposits exist at depth in the Baltimore Canyon Trough area. II! fact, the Houston Oil and 

Minerals well 676-1 (fig. 1) penetrated salt at a 

depth of about 3.8 km (J. C. Hathaway; written 

commun., 1979). The salt was probably deposited 

in Late Triassic to Early Jurassic time when 

restricted oceanic circulation would have created 

local evaporite conditions (Evans, 1977). The diapir 

shown in figure 24 and the one off Cape Hatteras 

(not shown) arch Tertiary sediments and, therefore, may still be active. Their proximity to the 

landward edge of the oceanic crust suggests that 

differential subsidence between the shelf and 

slope-rise areas could have disturbed the deep 

evaporite horizons and initiated the piercement activity. 

Biostratigraphic data from the COST No. B-2 

well indicate that the sediments penetrated by the 

well were deposited in water depths of less than 

500 m and that much of the Cretaceous section was 

deposited in a shallow-marine or terrestrial environment (Scholle, 1977b). A depth-versus-age 

curve for the COST No. B-2 well (fig. 16) indicates 

that the average Tertiary and Cretaceous subsidence rates were 23 and 31 m per million years, 

respectively. If the base of the Jurassic section in 

the Baltimore Canyon Trough is assumed to be at a 

depth of 12 km, ·then the Jurassic subsidence rate 

would be approximately 120 m per million years, or 

nearly four times the Cretaceous rate. 

According to Watts and Ryan (1976), if the effect 

of sediment loading is removed, rifted margins 

subside in an exponentially decreasing manner 

similar to that found for midocean ridges. The subsidence of these margins is controlled primarily by 

cooling and thermal contraction of the lithosphere 

(Sclater and others, 1971; Sleep, 1971). Watts and 

Ryan (1976) noted that additional driving 

mechanisms, such as gravitational outflow of 

crustal material (Bott, 1971) and deep crustal 

metamorphism (Falvey, 1974), may be required to 

explain the large amounts of subsidence seen along 

Atlantic-type continental margins. The Baltimore 

Canyon Trough has nearly four times as much sediment fill as have the basins studied by Watts and 

34 

Ryan (1976) and is one of the deepest basins along 

the Atlantic margin. 

Although the subsidence history of the sediments 

of the slope-rise area has not been detailed by any 

deep drill holes, the landward-dipping sedimentary 

horizons below the slope and upper rise on USGS 

line 2 (at a depth of 8-10 km, fig. 12) suggest that 

subsidence there has been less than that beneath 

the shelf. (The dip reversal is accounted for by 

growth faults, as shown on figure 66 by Mattick, 

Scholle, and Girard (this volume).) If the continental crust beneath the shelf was not rigidly coupled 

to the oceanic crust during the Jurassic Period, 

then the shelf and slope-rise areas could have subsided independently (fig. 26). The boundary between areas having different rates of subsidence 

may have been a narrow zone at the landward edge 

of the oceanic crust through Jurassic and Early 

Cretaceous time. However, the continuity of Upper Cretaceous and lower Tertiary horizons (on 

seismic records) across the outer shelf and upper 

slope indicates that major tectonic activity and differential rates of subsidence terminated near the 

end of Early Cretaceous time. 

en 10 a: 

~ :i 

g 

S2 8 

~ 

SHELF SUBSIDING 

MUCH FASTER 

THAN RISE I 

JURASSIC 

A 

/J 

SHELF SUBSIDING 

SLIGHTLY FASTER 

THAN RISE 

I 

II 

CRETACEOUS I 

I 

I 

I 

I 

I 

I 

I 

~-l\\S~ s~ I 

I 

100 

RISE SUBSIDING 

FASTER THAN 

SHELF 

I 

I 

TERTIARY.........-. 

0 

AGE, IN MILLIONS OF YEARS 

FIGURE 26.-Subsidence rates of shelf and adjacent slope-rise 

areas in the Baltimore Canyon Trough area. 
According to Grow and Markl (1977), during the 

Late Cretaceous about 1 km of sediment was 

deposited on the shelf and somewhat less was 

deposited on the rise (at least where sediment 

thickness has been mapped off Cape Hatteras rise). 

Because Tertiary sediments on the shelf are less 

than 1. 5 km thick and those on the rise are more 

than 2.5 km thick, we conclude that during the Tertiary, sediments tended to bypass the shelf. 

Therefore, during the Tertiary, the subsidence rate 

of the slope-rise area probably was greater than 

that of the shelf area. 

STRATIGRAPHY 

Poag (this volume) and Schlee (this volume) both 

discuss the stratigraphy and paleoecology of the 

Baltimore Canyon Trough area; however, each 

author uses a somewhat different approach. The 

interpretations of Poag are based on preliminary 

analyses of foraminiferal assemblages derived 

from 17 offshore borings and on a review of 

published stratigraphic investigations of Coastal 

Plain wells. His data on deposits onshore are largely taken from the comprehensive compilation by 

Brown, Miller, and Swain (1972). Schlee describes 

the seismic units delineated on the seismic records 

and attempts to interpret the lithology of these 

units and the environments in which they were 

deposited. Poag's analyses are limited to the 

deepest sediments penetrated . in drill holes, 

whereas Schlee interprets the stratigraphy and 

paleoecology of sequences below the bottom of the 

COST No. B-2 well. 

FORAMINIFERAL STRATIGRAPHY AND 

PALEOECOLOGY 

By C. WYLIE POAG 

In this section, biostratigraphic and paleoenvironmental interpretations are based chiefly on 

the distribution of planktic and benthic 

foraminifers, but calcareous nannoplankton, 

radiolarians, and diatoms also yielded significant 

information. Figure 27 shows the location of sample sites and of the cross sections constructed from 

these studies. 

For those units from which samples are not 

available (chiefly rock units deeper than the bottom 

of the COST No. B-2 well), interpretations are 

derived from seismic-reflection studies (Schlee, 

35 

this volume) and from stratigraphic evidence obtained from the Scotian Shelf, U.S. Atlantic 

Coastal Plain, and Bahamas Platform. Figure 28 

shows the major geologic and seismic units in the 

Baltimore Canyon Trough area (see also Schlee, 

this volume). 

PRE-CRETACEOUS ROCKS 

A schematic paleoecologic cross section of the 

Baltimore Canyon Trough is shown in figure 29. 

Interpretation of the pre-Cretaceous units is based 

chiefly on the work of Schlee (this volume) and 

Grow and Klitgord (this volume); however, 

Jurassic rocks have been penetrated in several 

wells in the studied area (Brown and others, 1972; 

Perry and others, 1975). Coarse micaceous 

feldspathic nonmarine sandstones, red and green 

shales, and a few marine limestones constitute 

most of the thickest Jurassic interval in the 

Salisbury and Albemarle embayments (215 m in 

the Esso-Hatteras Light No. 1 well; Brown and 

others, 1972; Perry and others, 1975). A few 

meters of fossiliferous limestone overlying the 

sandstone in this well may also be of Jurassic age 

because it contains the foraminifer Anchispirocyclina lustitanica (Egger). The COST No. 

B-2 well penetrated Jurassic rocks having a 

similar lithology but also containing thin marine 

shale beds. Dinoflagellates in a core at 4,060 m 

from the COST No. B-2 well indicate a Kimmeridgian (Jurassic) age (E. I. Robbins, oral commun., 1977). The precise age at the bottom is not 

known but is assumed to be Jurassic (figs. 28, 29). 

CRETACEOUS 

The COST No. B-2 well penetrated approximately 2 km of chiefly nonmarine Lower Cretaceous sandstone and shale containing lignite and coal 

beds. The sandstones are fine, medium, and coarse 

grained; the shales are red, green, and gray 

(Scholle,1977b). Drill-hole data from the onshore 

Coastal Plain (Brown and others, 1972; Perry and 

others, 1975) indicate that the lithology and 

paleoenvironment of Lower Cretaceous sedimentary rocks there are similar to those of the 

Lower Cretaceous sedimentary rocks penetrated 

in the COST No. B-2 well (figs. 28 and 29). In onshore outcrops, Lower Cretaceous rocks are generally assigned to the Potomac Group. Schlee (this 

volume) and Mattick, Scholle, and Girard (this 
E 

DAVIDSONFURBEE I 

35°+ 

EXPLANATION 

.r-200m"' Isobath shown for 200 and 2000 m 

0 Lease sole No. 49 

Cl Lease sole No. 40 

0 Selected drill hales 

USGS seismic lines 

A_K Cross section lines A-K 

25 50 

0 

0 

ASP~~ ASP 7 ~ 

AM COR I 6006 

74° 

+ 73° USGS 72° 

+ 0 SUFFOLK ~'+41 

NEW YORK TW-6 / 

c;\S\.~~0 ~ 

\.0~ \c-. 

K ~ 

~ 

\ 

\ 

FIGURE 27.-Map of the United States mid-Atlantic margin showing locations of lease tracts, seismic grid, 

and sample sites (coreholes and drill holes). Lettered cross sections are illustrated in figures 28-35. In 

1967, a consortium of oil companies conducted the Atlantic Slope Project (ASP), during which coreholes 

were drilled at eight sites. In 1976, the USGS undertook the Atlantic Margin Coring Project (AM COR), 

and cores were recovered at 19 sites (9 in the Baltimore Canyon Trough area). Sediment penetration at 

ASP and AMCOR sites was limited to 330 m. 

36 

AM COR 

6012 

J 
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50 

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100 150 

APPROXIMATE HORIZONTAL SCALE, IN KILOMETERS 

E X P L A 

~ CALCAREOUS MATERIAL 

tt:S:g LIMESTONE OR DOLOMITE 

NATION 

I ~ ---1 SALT I EVAPORITE 

~-~_:,~'j CONTINENTAL BASEMENT 

l,('cJ REEF 

B 

E:3 

200 

OCEANIC BASEMENT 

WAVY LINE REPRESENTS 

UNCONFORMITY 

FIGURE 28.- Schematic geologic cross section of the Baltimore Canyon Trough (A -B on fig. 27). Strong seismic reflectors, in some areas coinciding with unconformities, are indicated by heavy black lines. General geometry of major rock units is approximately to scale, but 

thicknesses within the Cenozoic strata are not to scale. (This distortion is necessary to show the stratigraphic relationships.) Adapted from 

Poag (1978). 
zz 

-o 

Oj:: 

zu 

ww 

Ill (I) 

B 

15 I I I I I I 

0 APPROXIMATE VERTICAL 50 100 150 200 

EXAGGERATION X8 

APPROXIMATE HORIZONTAL SCALE, IN KILOMETERS 

EXPLANATION 

~ ~ ~ E3 a LZ2J .. ~ ' ~ NONMARINE MARGINAL DELTAIC SHELF SLOPE OCEANIC CONTINENTAL WAVY UNE 

MARINE BASEMENT BASEMENT REPRESENTS 

UNCONFORMITY 

FIGURE 29.- Schematic paleoecologic cross section of the Baltimore Canyon Trough (A -B on :fig. 27). Strong seismic reflectors, in some areas coinciding with unconformities, are indicated in heavy black lines. Interpretations of paleoecology of rocks deeper than about 5 km and those 

seaward of COST No. B-2 well are based on seismic characteristics (Schlee, this volume), extrapolation from drill holes on the U.S. Atlantic 

Coastal Plain (Brown and others, 1972), and analogy with the Scotian Shelf (Jansa and Wade, 1975a). 
volume) suggest that seaward of the COST No. 

B-2 well, Lower Cretaceous rocks are limestone 

and dolomite and, locally beneath the slope, form a 

fringing reef complex that bordered much of the 

Baltimore Canyon Trough during the Late 

Jurassic and Early Cretaceous (fig. 28). Determination of palynological zones within the 

Cretaceous Coastal Plain sedimentary rocks indicates that the Upper Cretaceous may extend 

deeper than was formerly thought. Perry and 

others (1975) presented a reassessment of 

Mesozoic Coastal Plain stratigraphy; detailed 

studies of palynomorphs include those by Sirkin 

(1974), Wolfe (1976), Doyle and Robbins (1977), 

and Christopher (1977). 

Upper Cretaceous strata in the COST No. B-2 

well show an increasing prevalence of marine 

deposition and consist of nearly 1,000 m of 

dominantly shallow marine sandstone, limestone, 

and shale (figs. 28, 29). Microfossils are abundant 

in much of the Upper Cretaceous section and 

reflect a marine shelf paleoenvironment. This 

change from nonmarine to marine conditions during Late Cretaceous time also is recorded in 

coastal wells from Cape Hatteras to New Jersey 

and is further manifest in sandy and clayey outcrops of the Raritan and Magothy Formations and 

the Matawan and Monmouth Groups (Perry and 

others, 1975). 

Seaward from the COST No. B-2 well, Upper 

Cretaceous mudstone and foraminiferal ooze have 

been dredged from the slope off New Jersey. They 

appear to have been deposited in bathyal conditions (Gibson and others, 1968). 

Meisburger (1977) has recovered abundant 

assemblages of well-preserved Late Cretaceous 

planktic foraminifers, which are present in sand as 

much as 30 m thick beneath the shallow coastal 

waters of North Carolina, between Cape Fear and 

Cape Lookout. Turbidite deposits on the Continental Rise off Cape Hatteras also contain Late 

Cretaceous microfossils (reworked) derived from 

outcrops on the nearby Continental Slope (Emery 

and Uchupi, 1972; Weed and others, 1974). 

PALEOCENE 

Paleocene rocks from beneath the shelf have 

been sampled only in the COST No. B-2 well. An 

interval of approximately 10m of relatively dense 

buff limestone contains microfossil assemblages 

deposited on the middle to outer shelf (fig. 30). 

Paleocene strata thicken to 60 m westward under 

39 

the New Jersey Coastal Plain. The shallow-marine 

nature of the microfossils is maintained, although 

the lithology changes to gray and white calcareous 

clay and sand. Southwestward beneath Cape Hatteras, 30 m of gray to white, calcareous, shallowmarine sandy clay and clayey sand represents the 

Paleocene. In outcrop, equivalent beds are placed 

in the Beaufort, Brightseat, Aquia, Marlboro 

(lower part), Hornerstown, and Vincentown Formations. 

EOCENE 

Eocene strata have been penetrated in many offshore boreholes (including COST No. B-2 well, 

AMCOR 6011, ASP 15 and 22, and DSDP 108) and 

also have been sampled in several dredges and 

cores from Hudson Canyon and on the shelf and 

slope off North Carolina (fig. 27). 

On the New Jersey shelf, approximately 20m of 

blackish to gray-green silty clay and fine silty 

glauconitic sand of middle to early(?) Eocene age 

was penetrated in AMCOR 6011 (fig. 30). The benthic species of calcareous foraminifers from this interval indicate that it was deposited under middleshelf conditions. Directly westward in the New 

Jersey Coastal Plain (Salisbury embayment), a 

more complete section of shallow marine Eocene 

rocks can be sampled. These rocks are gray to 

green clay, sandy clay, sand, and greensand and 

are approximately 150 m thick. Outcropping 

Eocene strata are included in the Castle Hayne, 

Nanjemoy, and Manasquan Formations and Shark 

River Marl (Brown and others, 1972). 

Southward from New Jersey, the Eocene section 

of the Coastal Plain thickens. At Cape Hatteras, 

the Eocene section is chiefly limestone and 

glauconitic sand and is about 300 m thick even 

though upper Eocene rocks are missing (fig. 31). 

Eocene beds thin shoreward of Cape Hatteras (fig. 

31). Eocene strata also are present near the sea 

floor on the North Carolina shelf between Cape 

Fear and Cape Lookout. The beds there contain a 

bryozoan hash and shallow-water benthic 

foraminifers (Meisburger, 1977). 

At the site of the COST No. B-2 well, the Eocene 

section appears to be nearly complete and is 270 m 

thick (fig. 30). In this well, the uppermost 90 m of 

Eocene rocks consists of impermeable, buff, 

calcareous shale; the middle 90 m is white chalky 

limestone; and the lowermost 90 m is buff shale 

and cream limestone. All these rocks are rich in 
zz zz zz ~z zz z -z -o -o -o ~Q -o (1)0 

ww 

~B ww 

~B ~B ztJ ~B ~B ww ww ww ww £0(1) £0(1) £0(1) £0(1) £0(1) £0(1) 

A TT rr B 

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500 

V) 

a:: 

w 

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w 

~ 

~ 1000 

-I 

.... 

0.. 

w 

a 

1500 

2000 APPROXIMATE VERTICAL 

E X p L A N A T 0 N 

D ~ ~ ED ~ NONMARINE MARGINAL DELTAIC SHELF SLOPE 

MARINE 

FIGURE 30.-Schematic dip section showing stratigraphy and paleoecology of sedimentary rocks in the northern Baltimore Canyon 

Trough area (approximately line A -B on fig. 27). 

40 
E 

0 

500 

1000 

V') 

Cll: 

w 

..... 

w 

~ 

~ 1500 

£ 

..... 

ICI.. 

w 

c 

2000 

2500 

3000 

KILOMETERS 

0 10 20 30 

APPROXIMATE VERTICAL EXAGGERATION X52 

DATUM IS SEA LEVEL 

EXPLANATION 

NONMARINE 

MARGINAL MARINE 

UNCONFORMITY 

zz zz -o -o 

~6 ~6 ww ww al(J) al(/) 

I I 

w 

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z 

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< M 

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F 

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w 

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.............. ............. ··········· ··········· 

FIGURE 31.- Schematic dip section showing stratigraphy and paleoecology of sedimentary rocks in the 

southern Baltimore Canyon Trough area (Albemarle embayment beneath North Carolina Coastal 

Plain; E-F of fig. 27). 

41 
0 

200 

en 400 

IX 

w 

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1-

ll.. 

w 

a 600 

800 

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EXPLANATION 

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zz 

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....... 

0 

0 

'() 

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~ SEA LEVEL 

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····::::::::::::::::::::::::::::::::::::::::::::::::::::::. 

0 10 20 30 KILOMETERS 

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1200 

0 

m 

1300 :!I 

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z 

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..... 

m 

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APPROXIMATE VERTICAL EXAGGERATION X132 

1000 1..---1 UNCONFORMITY 

FIGURE 32.- Schematic dip section showing stratigraphy and paleoecology of sedimentary strata in the central Baltimore Canyon 

Trough area (C-D of fig. 27). 

planktic microfossils and nannofossils that accumulated in bathyal conditions. They represent 

the maximum marine transgression known in the 

Baltimore Canyon Trough area. 

On the Continental Slope, three holes have 

penetrated Eocene strata (ASP 15 and 22 and 

DSDP 108; figs. 30, 32). ASP 15 penetrated approximately 100 m of middle Eocene, pale yellowgray, siliceous calcilutite; DSDP 108 penetrated 37 

m of light-gray siliceous calcilutite of the same age. 

42 

Approximately 200 km southward, ASP 22 

penetrated 15 m of buff to yellow-gray siliceous 

calcilutite of late Eocene age. All these slope 

samples contain rich radiolarian assemblages in 

addition to abundant planktic foraminifers and 

calcareous nannoplankton and were deposited in 

bathyal depths. 

In Hudson Canyon, yellowish calcilutite deposits 

and white chalks of early, middle, and late Eocene 

age have been dredged (Gibson and others, 1968); 
they, too, contain bathyal calcareous microfaunas 

including abundant radiolarians. 

On the North Carolina slope, several dredge 

hauls have recovered dense, tan and greenish, sandy limestone and foraminiferal calcilutite of 

Eocene age (Weed and others, 1974), but the 

presence of siliceous microfossils there has not 

been established. 

OLIGOCENE 

In the offshore area, the most complete section 

of Oligocene rocks occurs in the COST No. B-2 

well; the only other Oligocene samples in this area 

are from the shelf and the slope off North Carolina. 

The COST No. B-2 well penetrated approximately 

150 m of upper and lower Oligocene strata composed largely of buff to light-gray calcareous shale and 

claystone and of impermeable limestone near the 

top of the section (fig. 30). These strata accumulated in a shelf environment. 

According to Brown, Miller, and Swain (1972), 

Oligocene strata have not been reported from the 

onshore Coastal Plain of Virginia, Maryland, 

Delaware, and New Jersey (fig. 33). However, recent field work has revealed that upper Oligocene 

sediments crop out along the Pamunkey and 

Chickahominy Rivers in Virginia (J. E. Hazel, 

USGS, written commun., 1978). In the subsurface 

at Cape Hatteras (Albemarle embayment), an interval of 66 m of white sandy limestone, sand, and 

clay and green glauconitic, clayey sand represents 

Oligocene shallow shelf deposition (figs. 31, 34). 

Similar strata (former "Trent Marl") crop out in 

North Carolina, where they are overlain by shelly 

sands of the "Silverdale beds." Between Cape Fear 

and Cape Lookout, N. C., shallow cores and 

seismic-reflection profiles reveal a homogeneous 

fine sand as much as 80 m thick. Samples of this 

sand contain shallow-water benthic foraminifers, 

ostracodes, and mollusks of Oligocene age 

(Meisburger, 1977; L. W. Ward and J. E. Hazel, 

written commun., 1978). 

The Oligocene sediments recovered from the 

Hatteras slope include calcareous glauconitic 

siltstone, sandstone, and tan chalk that were 

dredged from a water depth of 1,525 m (Weed and I 

others, 1974). 

43 

MIOCENE 

Miocene rocks of the United States mid-Atlantic 

margin have been studied in considerably more 

detail than have been the older rocks. They were 

penetrated by AMCOR 6007, 6009, 6010, 6011, 

6012?, and 6016 (beyond areas shown in fig. 27); 

ASP 10, 14, and 15; and COST No. B-2 well (fig. 

27). 

Near the New Jersey shore (AMCOR 6011), 

approximately 172 m of largely shelly, gray to 

grayish-brown, fine, medium, and coarse sand containing beds of gray clay and grayish-brown silty 

clay was drilled (fig. 30). Microfossils in this section 

are chiefly diatoms, but radiolarians also are common. Calcareous nannoplankton and foraminifers 

are sparse. These sediments were deposited in 

shallow marginal marine conditions. 

Beneath the New Jersey Coastal Plain, Miocene 

rocks are similar to those from AMCOR 6011, but 

the sand is less shelly and less marine (fig. 30). 

According the Maher and Applin (1971) and 

Brown, Miller, and Swain (1972), Miocene deposits 

beneath Cape Hatteras are much thicker (as much 

as 400 m; figs. 31, 35) than those beneath the New 

Jersey Coastal Plain. In the Miocene deposits 

beneath Cape Hatteras, gray to white sand 

predominates, but greensand and sandy limestone 

also are present. Sandy Miocene strata, some containing diatomaceous beds, thin updip (fig. 33) and 

crop out as the Pungo River, Calvert, Choptank, 

St. Marys, and Kirkwood Formations. 

In the COST No. B-2 well, Miocene rocks 

thicken dramatically (fig. 30). More than 800 m of 

unconsolidated to semiconsolidated gray sand, 

gravel, and clay was penetrated. Diatoms are 

abundant in the microfossil assemblages, especially in middle and lower Miocene strata. Foraminifers are largely benthic species indicative of deltaic 

or near-deltaic conditions. The thick sequences of 

foreset bedding seen on geophysical profiles support the interpretation that the biota are deltaic 

(Schlee, this volume). 

Along the Outer Continental Shelf from Virginia 

to Long Island (AMCOR 6007, 6009, and 6010; fig. 

35), upper(?) Miocene sediments were penetrated 

to a maximum thickness of about 130 m (AMCOR 

6009). The lithology, microfossils, and derivation 

of these sediments are similar to those of Miocene 

sediments penetrated in the COST No. B-2 well. 

Sparse calcareous nannoplankton suggest that the 

bottom 10m of AMCOR 6012 may also be of Miocene age, but the lack of foraminifers or diatoms 
0 

500 

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1500 

2000 

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APPROXIMATE VERTICAL EXAGGERATION X528 

DATUM IS SEA LEVEL 

G 

II) 

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SALISBURY 

EMBAYMENT 

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:::::> u:: 

EXPLANATION 

NONMARINE 

MARGINAL MARINE 

~ 

~ 

SHELF 

UNCONFORMITY 

FIGURE 33.- Schematic strike section showing stratigraphy and paleoecology of the Coastal Plain segment of 

the Baltimore Canyon Trough area (E, C, G, A, Kin fig. 27). Basement configuration is somewhat distorted 

owing to choice of wells; for example, the Norfolk arch is not shown. 

44 
zz zz -o -o 

ww 

~6 ~6 ww al<n !C(/) 

I 

F G H 

V> 0 < z <><- < Wf- V>- --' N 

f-J: >- <z "' f-C) "' "o <- < "'V> 6 ;--' :::< 0~ z 0 6 J:>< f- V> V> uu V> V> V> z- 0 w w <0 u 0 

.... 

. . . ·.·.·.·.·.·.· .·.·.·. 

500 

1000 

1500 

2000 

(/) 

0:: 

w 

1-

w 

:::!! 

~ 2500 

:r:· 

1-

c.. 

w 

0 

KILOMETERS 

3000 ALBEMARLE 100 200 

EMBAYMENT 

EXPLANATION 

3500 ~ NONMARINE 

~ MARGINAL MARINE 

4000 

~ DELTAIC 

[J] SHELF 

4500 

!mill SLOPE 

E:::3 UNCONFORMITY \ 

5000 

APPROXIMATE VERTICAL EXAGGERATION X264 

FIGURE 34.-Schematic stratigraphic and paleoecologic section (approximately 

along strike) through four wells that penetrated Jurassic rocks within the 

Baltimore Canyon Trough area (F, G, H in fig. 27). Basement configuration is 

distorted owing to choice of wells. 

45 
I 

,., 

0 

0 

,., 

0:: 

0 

u 

~ 

<( 

0 

1000 

1500 

zz 

-o 

Ci= 

zu 

ww 

aJ(/) 

Vl 

<( 

0:: 

w~ 

1-1-

1-::r: 

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w 

0 

I 

zz 

-o 

Ci= 

zu 

ww 

a!(/) 

...... 

0 

0 

,., 

0:: 

0 

u 

~ 

<( 

KILOMETERS 

50 100 150 

I 

EXPLANATION 

~ MARGINAL MARINE 

DELTAIC 

t:::::::-:::1 SHELF 

1:;;-;;:s SLOPE 

B UNCONFORMITY 

zz ~z -o (/)Q Ci= 01-

zu zu ww ww aJ(/) aJ(/) 

n J 

N N 

~ "' ~ al 0 

0 0 0 ,., ,., 0 ,., 0:: 0:: z 0:: 

0 

u 

0 0 1- u u Vl 

~ ~ 0 ~ <( <( u SEA LEVEL <( 

PLEISTOCENE 

~ E VERTICAL EXAGGERATION X 660 cology of upper Cenozoic rocks a ttho ""'w"" 

APPROXIMAT . fgraphy and pale~ (I-J in fig. 27). FIGURE 35.- Strike section showin!~co: mar.,. h matlc the Baltimore stra I Cany on Troug 

46 
precludes a confident interpretation of the 

paleoenvironment. 

On the New Jersey slope (ASP 14, 15; fig. 30), 

diatomaceous sediments of probable Miocene age 

(possibly as thick as 83 min ASP 14) are composed 

of dark olive-gray to yellowish-brown glauconitic 

sand and silty clay. Outer shelf conditions of 

deposition are inferred for these strata. 

In theN orfolk Canyon area off Virginia (ASP 10; 

fig. 32), middle Miocene diatomaceous beds were 

cored. The section is composed of olive-gray to 

yellowish-brown clay, sandy clay, and clayey sand 

lacking conspicuous glauconite except in the 

lowest few meters. The diatoms are benthic and 

planktic marine species mixed with freshwater 

species; this mixture suggests that fluvial-marine 

deposition occurred nearby. 

Four piston cores in and near Hudson Canyon 

reportedly recovered Miocene sediments (Ericson 

and others, 1961), but reevaluation of the published 

microfossil and nannofossil content of these 

samples suggest that they are probably of Pliocene 

age. 

PLIOCENE 

Pliocene sediments in the Baltimore Canyon 

Trough were penetrated in AMCOR 6007, 6009, 

and 6010, in ASP 7 and 10, and in scattered piston 

cores (fig. 27). In the Coastal Plain, they may be included in the post-Miocene strata, which are chiefly 

coarse to fine, gray to white, shelly sand and silty 

clay, a few tens of meters thick (Pleistocene and 

Pliocene beds shown in fig. 33). In outcrop, 

Pliocene sediments constitute the Yorktown and 

Duplin Formations, the Cohansey Sand, and the 

lower part of the Croatan Formation (Hazel, 1977). 

Near the New Jersey shore, cores taken from 

AMCOR 6011 indicate that about 65 m of gray to 

white sand and silty clay is present; the clay is barren of fossils, but some of it may be Pliocene (fig. 

30). In the COST No. B-2 well, a 66-m-thick interval of unconsolidated, white to gray sand and 

clayey sand contains a sparse inner-shelf benthic 

foraminiferal fauna that suggests it is of Pliocene 

age (figs. 30, 35). Near the seaward edge of the 

New Jersey shelf, AMCOR 6010 penetrated about 

65 m of gray silty clay and gray to olive sand that 

contains sparse Pliocene benthic foraminifers (figs. 

30, 35). The fauna, in conjunction with abundant 

lignite particles and other organic matter, suggest 

lagoonal deposition. 

To the south, AMCOR 6009 penetrated 25m of 

gray silty clay and gravel containing pyritized 

diatoms and a shallow shelf assemblage of Pliocene 

foraminifers (fig. 35). At the seaward edge of the 

shelf, east of the mouth of Chesapeake Bay, AMCOR 6007 penetrated about 65 m of richly diatomaceous, olive-gray, silty clay and gray clayey 

sand of Pliocene age (figs. 32, 35). The few 

foraminifers in this unit are shallow-marine benthic species that preferred the high-nutrient conditions commonly found around deltas. 

Downslope, adjacent to Norfolk Canyon, ASP 10 

penetrated approximately 166 m of diatomaceous 

Pliocene olive-gray silty clay (fig. 32). The diatoms 

suggest middle-shelf to outer-shelf environment, 

but the influence of a nearby river is reflected in 

the significant number of freshwater forms. 

On the Hatteras slope (ASP 7), about 15 m of 

olive-gray, highly calcareous, clayey sand and 

sandy clay contains abundant late Pliocene 

planktic foraminifers and calcareous nannoplankton (fig. 27). Green foraminiferal calcilutite 

of the same age, containing bathyal faunas, has 

been recovered from Hudson Canyon and vicinity 

(Ericson and others, 1961). 

47 

PLEISTOCENE 

Pleistocene sediments have been recovered in 

almost every core taken in the Baltimore Canyon 

Trough area. Onshore, Pleistocene sediments may 

be included in undifferentiated post-Miocene 

deposits (Pleistocene and Pliocene beds shown in 

fig. 33). These deposits are generally white to gray, 

shelly to nonfossiliferous, fine to coarse sand containing some silty clay and may be as much as 30 m 

thick (figs. 30, 31, 33, 34). These beds were probably deposited in nonmarine and marginal marine 

conditions. Outcropping Pleistocene beds have 

been included in several formations- for example, 

the Waccamaw, the upper part of the Croatan, 

Flanner Beach, Pamlico, "Kempsville," and Norfolk Formations and Gardiners Clay (Brown and 

others, 1972; Hazel, 1977). 

Nearshore the AMCOR 6011 (fig. 30) and 6008 

coreholes penetrated as much as 120 m of unconsolidated gravel and gray, shelly to barren sand 

and silty clay of Pleistocene age. These strata constitute marginal marine, lagoonal, and probably 

fluvial channel-fill deposits. Farther offshore 

beneath the shelf, Pleistocene sediments thicken 

and change facies. At AMCOR 6007, 6009, and 
6010, Pleistocene beds are dark gray to olive-gray, 

clayey and silty sand (in many places shelly) and 

silty clay (figs. 30 and 35). Maximum thickness is 

about 170 m at AMCOR 6010. Alternating 

lagoonal, inner shelf, and middle to outer shelf 

strata form complex vertical facies; glacialinterglacial cycles have not yet been clearly 

defined. 

The COST No. B-2 well penetrated nearly 250m 

of white to gray, unconsolidated, shelly to barren 

gravel, sand, and clay of Pleistocene age (figs. 30, 

35). The vertical facies changes were somewhat 

masked by the drilling methods, but shallow 

marine to nonmarine strata appear to dominate. 

On the Continental Slope, surprisingly thick 

Pleistocene sequences of gray to dark-gray, gassy, 

silty and sandy clays were penetrated in AMCOR 

6012 and 6021 (figs. 30, 35) and in ASP 7, 22, and 

23. Thicknesses range from about 162m in ASP 22 

to more than 300 m in AMCOR 6021 and ASP 23, 

where pre-Pleistocene strata were not reached. 

Planktic foraminifers of temperate-water origin 

are scattered throughout the Pleistocene strata, 

and some intervals are rich in diatoms, middle to 

outer shelf benthic foraminifers, and dark organic 

particles. This association suggests deposition in 

anoxic depressions on the shelf. Except a thin interval of indigenous slope deposits in the bottom of 

AMCOR 6021, all Pleistocene foraminiferal 

assemblages appear to have been displaced onto 

the slope from original deposition sites on the 

shelf. Ericson and others (1961) recognized an 

abundance of Pleistocene turbidite deposits from 

evidence in more than 30 piston cores from the 

Hudson Canyon area (Continental Slope and Rise). 

For example, the deltalike submarine fan near the 

canyon mouth contains coarse-grained layers (including gravels) that show grading of well-sorted 

particles, abundant plant detritus, and remains of 

shallow-water mollusks and benthic foraminifers. 

High-resolution seismic profiles indicate that 

Pleistocene turbidite deposits and submarine 

slumps are common all along the incised Continental Slope of this region (McGregor and Bennett, 

1977). 

HOLOCENE 

Emery and Uchupi (1972) have concluded that 

about 73 percent of the surface sediment on the 

Atlantic Outer Continental Shelf is relict-that is, 

a remnant body of sediment originally deposited in 

the early Holocene. This conclusion has been further substantiated by Sheridan and others (197 4), 

Stahl . and others (197 4), and Knebel and Spiker 

(1977). Cores, dredges, and high-resolution profiles 

show that the sediment cover is a distinctive sheet 

of medium to coarse, poorly sorted sand that in 

many places is yellow brown because of ironstained quartz and feldspar grains; the sediment 

contains peat, remains of land vertebrates, and 

oyster shells. It reaches thicknesses of 20 m along 

the seaward edge of the New Jersey shelf, but it is 

not differentiated on the cross sections illustrated 

herein. Holocene sediments on the Continental 

Slope are mainly green silty clay and clayey silt 

whose carbonate content (mainly planktic 

foraminifers) increases as distance from shore increases and which is subject to frequent mass 

movement downslope. 

48 

ACOUSTIC STRATIGRAPHY 

By JoHN S. ScHLEE 

Geologists interpreting geophysical records have 

long attempted to correlate distinctive reflecting 

horizons and to give them chronostratigraphic 

significance (same age throughout area in which 

observed). Horizon A (lower Eocene), in the deep 

ocean basins, is one of the first of the reflectors to 

be so correlated (Ewing and others, 1966; Ewing 

and others, 1970). Other reflectors (B, B*, A*, All) 

have been used to correlate packages of reflectors 

across wide areas of the sea floor (Emery and 

others, 1970; Emery and others, 1975) in an attempt to put together the geologic history of the 

oceanic basins. On the continental margin, similar 

attempts have been made to correlate distinctive 

reflectors, but the results have been mainly limited 

to the upper second of record because of the problem of multiple reflections on single-channel 

reflection profiles. On the first multichannel profiles collected off the U.S. Atlantic margin, correlation of Cenozoic, Cretaceous, and preCretaceous sequences was based on changes in the 

acoustic character of the reflectors; horizons (K, Z, 

X) were drawn in order to bound these distinctive 

groups (Schlee and others, 1976). Implicit was the 

assumption that these horizons approximated time 

lines. On the Canadian Atlantic margin, acoustic 

reflectors have been tied to drill-hole stratigraphy 
with a high degree of certainty by Jansa and Wade 

(1975a and b), Parsons (1975), and Given (1977), 

but these authors correlated their reflectors to key 

lithologic units rather than to unconformities. 

The most detailed attempt to correlate key 

reflectors with unconformities in cores and to use 

the reflectors to build an acoustic stratigraphy has 

been made by P. R. Vail and his associates (Vail 

and others, 1977) for the Gulf of Mexico, San Juan 

basin, west Africa, the North Sea, and South 

America. On the basis of their analysis of seismicreflection profiles in areas where drill holes are 

numerous, they found that seismic reflections are 

returned primarily from (1) stratal surfaces and (2) 

unconformities characterized by sufficient velocity 

and density contrasts to cause a coherent return of 

acoustic energy (Vail and others, 1977). The stratal 

surfaces are time-synchronous bedding surfaces; 

at one time, they were surfaces of deposition that 

existed over a wide area. Unconformities can be 

used to bound groups of reflectors which are correlated with depositional sequences whose ages are 

estimated. Figure 36 illustrates the basic concepts 

of a depositional sequence as defined by R. M. Mitchum, Jr., P.R. Vail, and S. Thompson III (in Vail 

and others, 1977, p. 54). The relationships of strata 

(and reflectors) to the sequence boundaries are 

shown in figure 37. 

The time significance .of an unconformity is that 

all the rocks below the unconformity are older than 

the rocks above it (fig. 36). More importantly, the 

depositional sequences between major unconformities have been analyzed for coastal onlap, downlap, 

and toplap (illustrated in figure 37) to define 

geochronologic cycles of relative sea-level change. 

Some of the major unconformities appear to correlate over wide areas and may have formed at the 

same time worldwide. Thus, they indicate a major 

amount of relative sea-level drop. A table showing 

changes in eustatic sea level by P. R. Vail, R. M. 

Mitchum, Jr., and S. Thompson III (in Vail and 

others, 1977, p. 93) shows major shifts in sea level 

in the late Miocene, middle to late Oligocene, early 

middle Eocene, middle Paleocene, middle Cenomanian (Late Cretaceous), Valanginian (Early 

Cretaceous), and Sinemurian (Early Jurassic). The 

table also shows several older sea-level shifts that 

were probably earlier than the formation of the 

Baltimore Canyon Trough. Numerous lesser shifts 

also took place and would have caused the unconformities that bound smaller cyclic sequences. The 

major cyclic sequences would be bounded by the 

49 

major unconformities formed during the times 

listed above. 

Offshore, the seismic profiles reveal several major unconformities, particularly in the upper part 

of the section; for example, part of the seismic profile along line 6 is shown in figures 38 and 39. I 

assume that some of the offshore unconformities 

match up with the major unconformities reported 

by Vail and others (1977) and that some are local. 

My matches of unconformities in offshore seismic 

profiles with sea-level shifts shown in figure 2 and 

listed in table 1 of P. R. Vail, R. M. Mitchum, Jr., 

and S. Thompson III (in Vail and others, 1977, p. 

93) indicate that major hiatuses exist in the 

Baltimore Canyon Trough area in the late 

Miocene, middle to late Oligocene, middle 

Paleocene, middle Cenomanian (Late Cretaceous), 

late Aptian (Early Cretaceous), Kimmeridgian 

(Late Jurassic), and Sinemurian (Early Jurassic). 

The units delineated by these hiatuses are lettered 

A-H and are shown in figure 39 and described in 

table 1. 

Some of the offshore unconformities (Paleocene 

and Oligocene) probably correlate with hiatuses 

detected in drill holes in the Coastal Plain, but 

others are not found ashore for unknown reasons. 

A section based on wells drilled on the Atlantic 

Coastal Plain (fig. 40) reveals local unconformities 

in the upper part of the Cretaceous of New Jersey 

and major unconformities, one in the Oligocene 

(between units G and F) and one near the base of 

the Tertiary (between units F and E); however, 

even the major unconformities are not apparent in 

the southern part of the section. Some of the older 

offshore unconformities might correlate with 

hiatuses ashore that would be in nonmarine strata 

of Early Cretaceous and older age (fig. 41) and 

thus would be difficult to document where fossils 

are scarce. 

Only the COST No. B-2 well is available to serve 

as a guide to the offshore stratigraphy. Hiatuses 

are not evident in the stratigraphic section shown 

by Scholle (1977b), perhaps partly because of the 

sampling interval used for the paleontological 

study. The sampling interval (30-152 m) of rotary 

cuttings (subject to uphole contamination) would 

make checking for the completeness of a particular 

stage difficult. 

The intervals delineated acoustically were 

checked with ages assigned to the rocks in the 

COST No. B-2 well (Scholle, 1977b). A part of 

seismic line 2 (fig. 1) is approximately 12 km 

southwest of the well. A comparison of unit 
0 

en 

Ill: 

w 

1-

w 

~ 

z 

:x:' 

1-

0.. 

w 

c 

1000 

~ 

z 

:I B w-

~ ~ - .. t:- :: A u li 

8~ ..J 

0 

w 

C) 

I r-------------------~U~N=C=O~N~FO~RM~IT~Y------------------------~--C~O=N~F~O=R~M~I~T~Y--~ 8 !SURFACE OF NONDEPOSITIONI (NO HIATUS) 

B 

A 

UNCONFORMITY CONFORMITY UNCONFORMITY Arl -----=~~~~~~-----11-----+1------------~==~~~--------~IA !SURFACE OF EROSION (NO HIATUS) !SURFACE OF NONDEPOSITION) 

AND NONDEPOSITION) 

A 

r--------------------U~N_C~O~N_F_O~R~M_I~T_Y ________________________ +-__ C_O~N_F~O~R_M_I_T_Y __ ~I B Bl 

25-

20 

15 

10 

5 

UNCONFORMITY 

----------------------------

100 km 

CONFORMITY UNCONFORMITY 

-----i 

Ar--------------------------+------r-----------------------------------~A 

B 

FIGURE 36.-A, Schematic diagram of a depositional sequence showing the different types of relations ( onlap, truncation, and downlap) that can exist along the same unconformity. B, Reconstruction of above diagram in which geologic time is used as the ordinate. This chronostratigraphic section indicates (1) where the sedimentary record is most complete and (2) where the amount 

of time represented by a particular hiatus changes laterally. Both from R. M. Mitchum, Jr., P.R. Vail, and S. Thompson III (in 

Vail and others, 1977, p. 54), who (p. 55) defined sechron "(from se-quence and chron time) • • • as the total interval of geologic 

time during which a sequence is deposited." 

thicknesses determined acoustically and drilled Close examination of the part of seismic profile 6 

(table 2) shows some agreement in the younger shown in figure 38 reveals at least two conspicuous 

part of the section and some disparity in the older unconformities in the upper part of the record 

part. Eventually, when a sufficient number of deep which are recognizable by downlap of an oblique 

exploratory wells have been drilled on the shelf, progradational unit and by onlap of the overlying 

geologists will be able to modify the acoustic unit. I assume these two units to be F and G (table 

stratigraphy given in this paper and to eliminate Jl; fig. 39) of early Paleocene to early Oligocene and 

the disparities seen in part of table 2. of late Oligocene to early Miocene age, respective50 
UPPER BOUNDARY 

1. EROSIONAL TRUNCATION 2. TOP LAP 3. CONCORDANCE 

LOWER BOUNDARY 

1. ON LAP 2. 

~-----BASELAP------~ 

DOWN LAP 3. CONCORDANCE 

FIGURE 37.- Possible types of stratigraphic relations found at the upper and lower bounding surfaces (unconformities and disconformities) in a depositional sequence. Both from R. M. Mitchum, Jr., P . R. Vail, and S. Thompson III (in Vail and others, 1977, 

p. 58). 

TABLE 1. -Acoustic units delineated in the Baltimore Canyon Trough area 

Unit 

designation Inferred age External lower Internal Properties Range of 

Seismic facies interpretation 

(fig. 39) boundary Configuration Continuity 

H late Miocene Onlafe; conform- Parallel to low- Low to high. and younger. ab e; downlap. angle diver- gence. G early Miocene Onlafe; conform- Parallel to Low to and late ab e; downlap. sigmoid. moderate. Oligocene. F early Oligocene Onlafe; conform- Parallel and Low to high. to early ab e; downlap. sigmoid. Paleocene. E Late Cretaceous Conformable; Parallel to Moderate and 

(to Ceno- some onlara low-angle high. manian). and down ap. diverf.ence. D Early Cretaceous Onlafe; conform- Paralle , low- Low to (to Aptian?). ab e; downlap. angle divergent moderate. complex, 

oblique, and 

c sigmoid. Early Cretaceous Conformable; Parallel to low- Low to and Late on lap. angle moderate. Jurassic. B Late Jurassic Onlap; p:::~~f~~~e. Low to to Early conformable. divergent. moderate. Jurassic. A Early Jurassic Onlap; fault Diver~ent to Low to high. and pre-Early boundary. para lei. 

Jurassic. 

ly. The breaks are apparent where layers were obviously onlapped and truncated. Less obvious are 

disconformities where reflectors approach the 

break at an extremely low angle or where the 

hiatus is evident by the low undulating relief of 

reflectors adjacent to it. The onlap relations are 

most obvious on cross-shelf (dip sections such as 

shown in fig. 38) oriented at right angles to the 

interval velocities Intensity (km/s) 

Moderate to 1.55-1.85 Open-shelf marine, contrasting high 

high. energy and low energy to low 

ener~ . 

Low to high. 1.60-2.17 Open-s elf marine, contrasting hi~h 

and low energy; prograding she f. 

edge wedges. 

Moderate to low 1.87-2.60 Open-shelf marine of varbin~ energy and high. conditions, and a delta ui t off Delaware. Low to high. 1.90-3.32 Open-shelf marine of low to modest energy conditions. 

Low to 2.34-4.07 Nonmarine to open-shelf marine moderate. and low energy conditions. 

Variable; low 2.91-5.02 Most!~ nonmarine to littoral to high. marme. 

Variable; low 3.96-6.38 Mixed nonmarine and evaporitic to high. restricted marine; sandy. 

High to low. 3.95-6.36 Mixed nonmarine and restricted 

marine. 

strike of sedimentary units, where the section 

thins in a short distance; profiles oriented parallel 

to the shelf also can show onlap and downlap relations, but the thinning is spread over a longer 

distance. 

Not all acoustic units are marked by an obvious 

unconformity. The acoustic unit H (post-upper 

Miocene) is mainly strong, even reflectors above a 

51 
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• 

• 

NORTHWEST SHOTPOINT NUMBER SOUTHEAST 

6 

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0 10 KILOMETERS 

FIGURE 38.-A part of CDP multichannel seismic profile 6 off southern New Jersey (see fig. 1 !or location). 

6 
01 

C.:l 

NORTHWEST SOUTHEAST 

0 

V) 

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0 10 KILOMETERS 

FIGURE 39.-The same part of seismic profile 6 that is shown in figure 38 but on which the acoustic units are labeled. The acoustic units are described 

in table 1. Toward the top of the record can be seen broadly onlapping unit G and obliquely prograding unit F. Also, the transition from inferred 

marine facies (high continuity and moderate to high seismic amplitude) to inferred nonmarine facies (low continuity and variable seismic amplitude) 

can be seen within units C and D. 

5 

6 
-ll 1: .. 0 1: 

..2 "' ·;;: 1: 

Qj .:..: 0 ~ u g> j -o i5 

]i "' 1: J. .:. 0 

~ ~ 0 0 <-' <-' 

1: 

>. ~ 5 5 0 b ..<:. ..<:. 

~ u u 

::l 1: 1: 

VI w < < 

NORTHEAST 

..<:. 

u 

5! 

00 

-o 

1: 

~ 

;;; 

<-' VI 

::::l 

EXPLANATION 

• limestone and marl 

~ '? 

.f ~ .!! 1-

o~-" ci'ig; 0 -o~ :s <=N VI OVI ' 

~ ~ ~ VI u: => 

0 

200 

400 

600 

800 

1000 

8 Sand, sandstone, and conglomerate 

[] Shale, siltstone, and claystone 

Unconformity 

FIGURE 40.-A generalized lithologic section based on 13 holes drilled near the seaward edge of the Atlantic Coastal Plain from North Carolina to New York; 

these holes were described by Brown, Miller, and Swain (1972). The section shows major hiatuses and the correlation of letter-designated units 

described in table 1. See figs. 1 and 27 for well locations. 
.. c '"0 

.B Sl c c ·;;: 

ti :;< 0 ~ u 

~ '"0 ~ I 

:0 c 

0 0 i3 a ~ ~ C> C> 

c >- ~ 6 6 ..t: ..t: 0 u 

~ 0 u 

Z! c c <J) w < < 

NORTHEAST 

..t: 

u 

2 

00 

'"0 

c 

0 

.... 

;;; 

C> 

<J) 

::::> 

EXPLANATION 

~ Nonmarine 

liiil Marginal marine 

Ill Marine shelf 

• limestone and marl 

~ ~ -~ "' ..... 

Ro. :1!: <no o -oc::; :s c<Jl <n 0 0 

.... <J) 

- C> ~ <J) 

iL :::) 

0 

200 

400 

600 

800 

1000 

[J Sand, sandstone, and conglomerate 

f! Shale, siltstone, and claystone 

A-'\ Unconformity 

FIGURE 41.- Environments of deposition as represented in the generalized lithologic section in figure 40. Interpretation by C. Wylie Poag, who was 

unable to project environment of deposition between the two northeasternmost wells because of lack of information. 
TABLE 2.-A comparison of the thickness of acoustic units from 

seismic line 2 with the thickness of rocks of equivalent age in 

the COST No. B-2 well 

Age interval 

Post-middle late Oligocene ____ _ 

Middle late Oligocene to 

middle Paleocene __________ _ 

Middle Paleocene to middle 

Cenomanian --------------- Middle Cenomanian to late 

Aptian -------------------

Thickness of acoustic units along line 21 

(kilometers) 

0.88 

.37 

.66 

.75 

Thickness of units penetrated in the COST No. B-2 well (kilometers) 

0.85 

.30 

.85 

.40 

1 The thickness of each acoustic unit is the mean calculated from the values at the 

two closest shotpoints as given by Digicon Geophysical Corp. on line 2. 

presumably older unit that lacks strong, highamplitude, continuous reflectors (fig. 39). In a few 

areas, extremely low angle truncation of the older 

unit, G, is evident, but where the truncation is 

missing, the youngest unit, H, still projects 

through on the basis of its acoustic character. In 

the lowest part of the section, the boundary at the 

top of unit A (Lower Jurassic to pre-Lower 

Jurassic) was inferred to be present at the top of 

the conspicuous group of reflectors 5-6 seconds 

below sea level in the deepest part of the basin; 

these reflectors can be traced widely over the 

Baltimore Canyon Trough and the Georges Bank 

basin. Further, they mark a velocity change that 

averages from about 4. 7 to about 5.5 km/s. Similar 

strong reflectors are present just above acoustic 

basement on the Scotian Shelf where they were 

drilled. There they represent a sequence of halite 

and dolomite- part of the Argo, Iroquois, and 

Mohican Formations of Early to Middle Jurassic 

age (Given, 1977). 

The acoustic units recognized in the Baltimore 

Canyon Trough (table 1) vary widely in acoustic 

character and in their boundary relations. The 

change in acoustic character, both laterally and 

vertically, was alluded to by Schlee and others 

(1976); the change in character is mainly in the continuity of the reflectors and in their intensity (fig. 

39). Both these acoustic properties plus the 

breadth and reflector configuration have been used 

by J. B. Sangree and J. M. Widmier (in Vail and 

others, 1977, table 1, p. 166-168) to infer environments of deposition for sedimentary sequences represented by the acoustic unit. My interpretation of seismic facies present in the Baltimore 

Canyon Trough area (table 3) is based on their 

table. 

The environments described in table 3 are mainly 

shelf or coastal-plain types. However, two shelfslope types (sigmoidal mound seismic facies and 

oblique-progradational seismic facies) are present 

in the Baltimore Canyon Trough area along with 

the other seismic facies. The main feature to typify 

most of these seismic facies is a general parallelism 

of reflectors. They may diverge in some areas 

because of differing rates of subsidence, and they 

may become discontinuous because of a presumed 

change in the types of sediments within the unit. 

TABLE 3. -Seismic facies present in the Baltimore Canyon Trough area 

[Extracted from J. B. Sangree and J. M. Widmier (in Vail and others, 1977, table 1, p. 166-168)] 

Seismic facies unit Interpreted environment of deposition External form of seismic unit 

Low continuity and variable amplitude_ Nonmarine-river and associated Sheet or wedge 

marginal marine transport processes. 

High continuity and high amplitude____ Shallow open marine shelf having Sheet or wedge wave transport; high- and low-energy 

conditions;/ossible fluvial deposits 

Low amplitude -------------------- S~~;trg~~!i a~jt~e~r~h:r~ift~~~~~ 

Moderate continuity and low to moderate amplitude. Sigmoid, low-relief mound __________ _ 

processes. 

Shale: marine shelf sediments de- posited under low-energy regime from turbidity currents and by wave transport. 

Open neritic shelf having low to modest energy conditions. 

Shelf delta complex ----------------

Oblique-progradational ------------- Shelf-slope boundary; variable energy conditions from h1gh energy in toplap-truncated area to low energy m chnoform and fondoform (prodelta 

zones). 

Sheet or wedge 

Sheet or wedge 

Low broad mound. 

Fan-shaped ____ _ 

56 

Internal configuration 

Parallel to divergent ___ _ 

Parallel to divergent ___ _ 

Parallel to divergent ___ _ 

Parallel to divergent ___ _ 

Sigmoid along deposi- tional dip; reflectors onlap and form an augen shape parallel to depositional strike. 

Parallel in upper part; oblique along deposi- tional dip and parallel or gently oblique to sigmoid parallel to depositional strike. 

Concordant at the top and con- cordant to gentle onlap and downlap at base. Concordant at top and concordant to gentle onlap and downlap at base. 

Discordant at top and concordant to gentle downlap or onlap at base. 

Concordant or low-angle truncation at top; concordant or onlap at the base. Concordant at top and downlap and onlap at base. 

Toplap truncation to downlap at base. 
The seismic facies described in table 3 are 

distinguished mainly on the basis of the continuity 

of their reflectors,the intensity (amplitude) of the 

reflector, the breadth of the reflector, and the 

geometry (shape) of the unit; a discussion and table 

of all units (deep water as well as shelf) are given 

by J. B. Sangree and J. M. Widmier (in Vail and 

others 1977, table 1, p. 166-168). They based their 

environmental inferences on drill-hole data keyed 

to multichannel seismic-reflection profiles collected in the same area. 

From this correlation of geophysical information 

and stratigraphy, several principles emerge. High 

continuity of reflectors is used to indicate a contrast in depositional energy conditions operating 

over a wide area. These conditions are mostly to be 

expected on a broad shelf having both high- and 

low-energy states that result in the deposition of 

interbedded sandstone, limestone, or shale. 

Agents of active sediment transport would probably be waves and currents on the shelf. Sangree 

and Widmier (in Vail and others, 1977, p. 166-168) 

also noted that a high continuity of reflectors can 

also characterize deposits of broad swampy 

coastal-plain areas in which fluvial sands are bedded with widespread coal and marsh clays. Conversely, low continuity of reflectors indicates the 

presence of lithologic units of limited areal extent, 

such as discontinuous channel sands bedded with 

flood-plain clays in an alluvial plain. To recognize 

this type of an environment, both the seismic 

amplitude and the continuity of reflectors are 

needed. 

Seismic amplitude provides a qualitative guide to 

the density contrast of adjacent reflectors. Coupled with low reflector continuity, variable 

amplitude is used to infer that sequences are nonmarine; nonmarine sequences commonly contain 

small channel sands that contrast strongly in density with adjacent clays so that high-amplitude 

reflections can result. Interbedded silt may provide 

less contrast to the clay. Thus, nonmarine sequences tend to be characterized by reflectors having low continuity and variable amplitude (table 3). 

Low-amplitude reflections or the absence of reflections suggests sedimentary rocks of a uniform 

lithology- commonly sandstone or shale. To 

choose between the two lithologies is difficult . 

unless the relationships to adjacent facies can be 

discerned. 

Across a depositional basin, the normal progression of environments is from an alluvial 

plain-coastal marsh, through a sandy littoral zone 

57 

across a marine shelf, into deeper parts of the 

basin. In the deeper parts of the basin, conditions 

are more uniform (less amplitude variation), and 

the energy of depositional processes can be low 

(lack of reflector continuity). Obviously, in mapping these facies on a grid of seismic-reflection 

profiles, the interpreter must establish the 

paleogeography; then, potentially confusing facies 

(and associated lithologies) can be sorted out. A 

uniformly thick sequence of sandstone deposited in 

a littoral environment can be expected to grade 

seaward to marine shelf deposits (high continuity 

and high amplitude or moderate continuity and low 

to moderate amplitude) and to grade shoreward to 

nonmarine deposits (low continuity and variable 

amplitude). A uniform shale deposited in a shelf 

basin offshore could be expected to grade laterally 

into normal marine-shelf sandstones and shale 

toward the basin edge and, possibly, into prograded slope deposits (chaotic fill; mounded onlapping 

fill, fan complex) in a basinward direction. 

The internal arrangement of reflectors is also an 

important guide to distinguishing environment of 

deposition. Most units associated with the shelf or 

subaerial coastal plain have a parallel to low-angle 

divergent arrangement of reflectors. But, where 

the sediments are deposited at the shelf edge or as 

a delta, then a sigmoid pattern of reflectors 

(perpendicular to depositional strike) is possible. If 

high-energy conditions have affected a part of the 

delta, the shallow-water part of it may be eroded so 

that an oblique progradational pattern can result 

because of the truncation of the fondoform beds 

(Rich, 1951). Parallel to the depositional strike, the 

delta can show a mounded arrangement of reflectors. 

The broad progradational arrangement of reflectors is also present in shelf-edge deposits. Normal 

to depositional strike, the reflectors can show the 

same sigmoid or oblique progradational arrangement found in deltas, depending on energy conditions at the shelf edge; obviously a major sea-level 

drop could strongly affect energy conditions at the 

shelf edge and thereby erode the undaform beds to 

create an oblique progradational pattern of reflectors. Laterally along the shelf edge, these deposits 

could be expected to grade into other shelf or 

upper-slope deposits. Shoreward from the shelf 

edge, they could grade into normal marine-shelf 

deposits (parallel; high continuity; high amplitude 

to low amplitude); in a seaward direction, they 

could grade into hemipelagic or mass-movement 

deposits of the Continental Slope. 
The acoustic units (table 1) have been carried 

across the Baltimore Canyon Trough in order to 

estimate thickness and the environment of deposition (fig. 42). As shown on figure 42, deeper reflectors thicken and disappear in an offshore direction 

(southeast). Beneath the Continental Shelf, interval velocities for the various acoustic units increase 

in a seaward direction and as depth increases 

(Grow and Klitgord, this volume; Schlee and 

others, 1976; Grow and Schlee, 1976). The loss of 

deeper reflectors and the increase of interval 

velocity offshore have been interpreted (Schlee and 

others, 1976) as a facies change to carbonate rocks 

in the older part of the section. 

ACOUSTIC UNITS 

The oldest acoustic unit (A) is assumed to include 

strata deposited during the Late Triassic and early 

part of the Jurassic (fig. 43). The strata unconformably overlie an irregular basement probably consisting of block-faulted continental crust rifted during the last opening of the Atlantic Ocean. On most 

cross-shelf profiles, acoustic basement is easily 

discernable under the inner part of the Continental 

Shelf where it deepens rapidly to more than 9 km 

off New Jersey (fig. 44). 

The upper limit of acoustic unit A is taken as a 

group of high-amplitude continuous reflectors 

assumed to represent carbonate and evaporite 

beds. Interval velocities below this boundary 

average about 5.5 km/s and those above the boundary about 4. 7 km/s. 

Given (1977) showed a conspicuous group of 

reflections just above acoustic basement under the 

northern Scotian margin. The reflections are from 

part of the Mohican Formation, a sequence of continental clastic and evaporite deposits and 

dolomites of Early Jurassic age. The similarity in 

appearance, position in the section, and range of 

velocity values between the reflectors that mark 

the top of acoustic unit A in the Baltimore Canyon 

Trough and the reflectors from the Scotian 

margin, suggests that Unit A and part of the 

Mohican are equivalent units. As can be seen from 

figure 44, unit A pinches out south of line 11, 

where basement rocks are probably only 3.5 km 

below sea level. To the northeast of line 11, it 

thickens to more than 5 km (fig. 43) off central 

New Jersey. In some areas like the Long Island 

58 

platform, the pinchout is irregular because the unit 

is contained within several fault troughs; basins 

between seismic lines 2 and 9 are inferred from 

aeromagnetic data (Klitgord and Behrendt, 1979). 

Both nonmarine and restricted-marine conditions appear to have prevailed during deposition of 

unit A. Strong continuous reflectors (those having 

high interval velocities) are above discontinuous 

reflectors of variable amplitude and breadth. No 

strata this old have been drilled in any offshore 

U.S. Atlantic holes (Scholle, 1977b; Weed and 

others, 1974); hence, inferences about them are 

mainly from the Canadian offshore holes (Mel ver, 

1972; Given, 1977). Evidence of evaporite deposits 

in unit A in the Balitmore Canyon Trough area 

comes from seismic line 14 collected in late 1977. 

This record shows a prominent salt (?) diapir that 

reaches from unit A to within about 1 km of the sea 

floor. 

Unit B is thought to include both nonmarine and 

transitional rocks of Jurassic age, to be more than 

3 km thick in the central part of the Baltimore Canyon Trough, and to have a range of interval 

velocities of 3. 7-6.4 km/s (fig. 45). It conformably 

overlies unit A and broadly onlaps the acoustic 

basement. Toward land, unit ·B is in turn onlapped 

by the overlying unit, as shown on the shoreward 

ends of the cross-shelf seismic profiles. Elsewhere, 

the unit is in apparent conformity with the overlying sequence. Internal configuration of reflectors 

in unit B is parallel except at the inshore parts of 

cross-shelf profiles, which show a low-angle 

seaward divergence of reflectors. 

Within the Baltimore Canyon Trough, the 

thickness of unit B exceeds 3 km under the outer 

shelf off southern New Jersey (fig. 45). It pinches 

out toward the Long Island platform and inner 

shelf adjacent to the coast farther south. It is more 

broadly distributed than unit A, and it thickens 

more uniformly than does the older unit. This 

change in the arrangement of the thickness contours suggests that the trough may have altered its 

pattern of subsidence, from one mainly dominated 

by fault troughs of limited areal extent to one of 

trough-wide subsidence, as the second phase of 

margin formation (postrifting) began. 

The low to moderate continuity of reflectors in 

unit B and their variable amplitude suggest mainly 

a nonmarine sequence along the periphery of the 

trough (fig. 45). Some continuous, high-amplitude 

reflectors are interspersed with the main group of 

reflectors in the southern part of the trough, and 

these reflectors are interpreted as interbedded 
01 

c.o 

NORTHWEST 

SHOTPOINT NUMBER 

SOUTHEAST 

2 

V> 

c 

z 

0 

u 

w 

V> 

~ 

w' 

~ 1- 4 ..... 

w 

> 

~ 1-

~ 

~ 

1-

~ 6 

0 

2 

V> 

"" w 

1-

w 

~ 

g 

>< 4 

~ 

:i 

li: 

w 

c 

6 

8 0 10 KILOMETERS 

FIGURE 42.-The depth and time section of USGS seismic line 6 under the seaward edge of the Continental Shelf, Continental Slope, and 

upper Continental Rise (from Grow and others, 1979). Note how deep reflectors on-the time section become back-tilted when the section is 

converted to depth. The shelf sedimentary prism is probably built across a jumble of deeply buried fault blocks under the slope and rise. 
60 80 IOOKM / 

"' A 

0 20 40 60 80 IOOKM 

B 

0 20 40 60 80 IOOKM I I I I I I 

c 

FIGURE 43.-Maps showing characteristics of unit A (see fig. 39) in the Baltimore Canyon Trough area. A, Thickness, in kilometers. 

B, Depositional environment; numbers represent USGS seismic lines shown in figure 1. C, Averaged interval velocity, in kilometers per second. The dots indicate control for thickness. Contours are dashed where seismic data were difficult to interpret. 

Velocity values are the arithmetic mean of values at 3-5 shotpoints between the black lines. Note irregular distribution of the 

unit in the northern part of the trough. Data on thickness of unit A inshore between seismic lines 2 and 9 were modified from 

aeromagnetic data supplied by K. D. Klitgord (USGS, Woods Hole, Mass.). Asterisked (0 ) interval velocities were calculated for 

areas where the boundaries of the unit were difficult to pick; these values, therefore, are only approximate. 

60 
O':l 

f-' 

en 

0:: 

w 

1-

w 

~ .... 

S2 

~ 

:z: 

1-

D. 

w 

0 

SOUTHWEST 

w 

z 

::::; 

.,::: 

C> 

en 

:::> 

w 

z 

::::; 

cnM 

C> 

:B 

w 

z 

::::;0 

en~ 

C> 

en 

:::> 

w 

z 

::::; 

.,-o 

C> 

en 

:::> 

w 

z 

::::; 

.,c... 

~ :::> 

w 

z 

::::; 

.,a-

~ :::> NORTHEAST 

0 I I I I :: --· ·•••• ~ 0 I E ¥ ;I!;" G t; . 

2 D n 2 

4 ~4 

6 6 

8 8 

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

" ............. ........ _..... ........ 

VERTICAL EXAGGERATION XlO 

I I I ,--- I 

0 25 SO 75 1 00 KILOMETERS 

FIGURE 44.- A depth section along seismic line 12 (see fig. 1 for location) parallel to the coast. The line traverses the shelf from Virginia to New York and shows the deepening from southwest to northeast in the Baltimore Canyon Trough; maximum depth is off New Jersey. Letters refer to the depositional sequences shown in figure 39 

and described in table 1. Cross-hatched areas represent basement rocks. Seismic horizons are dashed where inferred. 
0 20 40 60 80 IOOKM I I I I I I 

A 

0 20 40 60 80 IOOKM 

20om 

~/ / 

c 

FIGURE 45.-Maps showing characteristics of unit B (see fig. 39) in the Baltimore Canyon Trough area. A, Thickness, in kilometers. 

B, Depositional environment. C, Averaged interval velocity, in kilometers per second. In A, the dots indicate control for 

thickness, and the cross pattern shows areas where unit B is missing. Dashed line in B shows approximate location of shoreline 

during deposition of unit B; numbers represent USGS seismic lines shown in figure 1. InC, velocity values are the arithmetic 

mean of values at 3-5 shotpoints between the black lines. Asterisked (*)interval velocities were calculated for areas where the 

boundaries of the unit were difficult to pick; these values, therefore, are only approximate. 

62 
dolomites and evaporite deposits. Continuous highamplitude reflectors also are present toward the 

outer edge of the shelf in the upper part of unit B 

and merge with a lens-shaped mass under the 

slope. On line 2, this lens-shaped mass has been in-

~ terpreted as a carbonate reef (Schlee and others, 

1976, fig. 11). In much of the northern part of the 

trough, however, reflectors within unit B tend to 

lack continuity and have a low amplitude- a 

characteristic of either predominantly sand or 

predominantly shale sequences. A predominantly 

sand sequence is inferred because the area where it 

dominates the unit is between a probable nonmarine phase of the unit to the west and a more 

marine phase to the east (fig. 45). Presumably, the 

predominantly sand sequence represents a 

transitional-littoral facies that formed a broad 

sand plain adjacent to a narrow Atlantic ocean. 

Unit B has not been drilled in the study area; 

hence, the closest information on stratigraphic 

units of equivalent age is in the Scotian basin, 

1,000 km to the northeast. Here, Given (1977, p. 

68) described an "Early-Middle Jurassic section of 

halite, dolomite and interbedded clastics"; the section consists of part of the Argo, Iroquois, and 

Mohican Formations. In the Scotian basin, the 

Mohican Formation grades up into the Scatarie 

Member of the Abenaki Formation, a sequence of 

oolitic and pelletoidallimestone, of Middle Jurassic 

age, which Given (1977) interpreted as the first 

broad marine transgression into the northern Scotian basin. In the Middle to Late Jurassic, nonmarine (deltaic and fluvial clastic rocks) facies 

were deposited on the inner half of the Scotian 

Shelf (Mic Mac Formation and Mohawk Formation). Carbonate rocks, plus deeper marine shales 

and sands (Baccaro Member of Abenaki Formation), were deposited under the present outer shelf 

and upper slope. The carbonate banks were discontinuous features, in part, because of the influx of 

terrigenous clastic sediments from three deltas. 

The overlying unit (C), which bridges the 

Jurassic-Cretaceous boundary, appears to be mainly nonmarine and to be as much as 3 km thick in the 

northern part of the Baltimore Canyon Trough 

(fig. 46). Within unit C, reflectors tend to be 

parallel or divergent at a low angle. At the base, 

reflectors can onlap older units, though on many 

profiles, the boundary is a disconformity having 

conformable reflectors above and below. The upper 

boundary of unit C shows both onlap and downlap 

by the overlying unit, particularly on the Long 

Island platform. In much of the rest of the trough, 

reflectors in the upper part of unit C are conformable with those in the unit above. On the seaward 

ends of several cross-shelf lines, the upper part of 

unit C is characterized by fairly continuous reflectors of high to moderate amplitude. These probably 

represent limestones (Schlee and others, 1976; 

Sheridan, 1976). 

Unit C thickens to more than 3 km in the northern part of the trough. It appears to pinch out 

toward the New York Bight and to thin more 

gradually to the southwest (Virginia-Cape Hatteras area); locally it is thinned adjacent to an intrusive body (the Great Stone dome) off central 

New Jersey. For unit C also, the area of subsidence 

is broad adjacent to the inner shelf east of the 

Chesapeake Bay, though not as broad as in the 

underlying unit (B). 

Interval velocities of unit C (fig. 46) are mainly 

between 3 and 4.5 km/s, and the values tend to be 

higher offshore in the area where the unit is inferred to be either marine-shelf deposits or a sand 

facies. Most of the lower values are associated with 

nonmarine facies except at the seaward end of line 

9. The velocity values for the nonmarine sequences 

are in the range of 2.9 and 4.5 km/s; therefore, this 

interval could include well-indurated sandstone 

and shale having bulk densities of 2.3 -2.5 gm/cm3 

(Gardner and others, 197 4). The only offshore 

stratigraphic information for this interval comes 

from the COST No. B-2 well (Smith and others, 

1976), where velocities were in the range of 3.7-4.5 

km/s and the rocks drilled consisted mainly of interbedded sandstone, shale, and siltstone and scattered beds of limestone and lignite; these beds 

were deposited mainly in a nonmarine and transitional inner-shelf environment. 

The overlying unit (D) is inferred to represent 

the stratigraphic interval from the upper part of 

the Aptian Stage to the middle part of the Cenomanian Stage (upper part of the Lower Cretaceous 

and lower part of the Upper Cretaceous) and to 

show a change to more widespread marine conditions in the Baltimore Canyon Trough (fig. 47). 

Reflectors in Unit D adjacent to its lower boundary 

onlap toward the coast, but mainly, they are conformable with those in the unit below. Some channeling by basal reflectors marks the unconformity 

at the base of unit D, but channeling is even more 

evident at the upper boundary of this unit. Even 

here, however, this unit tends to be conformable 

with the overlying sequence except near the 

southern part of the trough (inshore part of line 11) 

and near the Long Island platform (line 9), where 

63 
0 20 40 60 80 fOOKM 

A 

~ • ~ s.f. 

.. : z.s,., ~~-. \~'·' · \·\\ . 

200m • • ~O ')) 

/ / 

FIGURE 46.- Maps showing characteristics of unit C (see fig. 39) in the Baltimore Canyon Trough area. A, Thickness, in kilometers. 

B, Depositional environment. C, Averaged interval velocity, in kilometers per second. In A, the dots indicate control for 

thickness and the cross pattern indicates areas where unit C is missing. Contours are dashed where seismic data were difficult 

to interpret. In B, numbers represent USGS seismic lines shown in figure 1. In C, velocity values are the arithmetic mean of 

values at 3-5 shotpoints between black lines. Asterisked (*)interval velocities were calculated for areas where the boundaries 

of the unit were difficult to pick; these values, therefore, are only approximate. 

64 
EXPLANATION 

\\\\\ Nonmarine 

~W} Marine shelf 

~~ Predominantly -=-----=- shale (shelf) 

0 20 40 60 80 fOOKM 

A 

B 

0 20 40 60 80 fOOKM 

c 

200m 

, / 

FIGURE 4 7.- Maps showing characteristics of unit D (see fig. 39) in the Baltimore Canyon Trough area. A, Thickness, in kilometers. 

B, Depositional environment. C, Averaged interval velocity, in kilometers per second. In A, the dots indicate control for 

thickness. Contours are dashed where seismic data were difficult to interpret. In B, numbers represent USGS seismic lines 

shown in figure 1. In C, velocity values are the arithmetic mean of values at 3-5 shotpoints between black lines. Asterisked (*) 

interval velocities were calculated for areas where the boundaries of the unit were difficult to pick; these values, therefore, are only approximate. 

65 
reflectors are beveled at a low angle by the overlying onlapping sequence. 

Unit D thickens to a maximum of 2 km off 

Maryland though it is also more than 1.5 km thick 

off southern New Jersey. It thins to less than 0.5 

km under the Atlantic Coastal Plain and Inner 

Continental Shelf, where thickness change is seen 

mainly as a low-angle divergence of reflectors on 

~cross-shelf profiles. 

Continuity of reflectors in unit D is low to 

moderate as is the seismic amplitude. The seismic 

patterns are interpreted to indicate a marine-shelf 

environment for the outer part of the present shelf 

and a nonmarine environment toward the present 

coast. Apparently, conditions over much of the 

marine shelf were uniform enough so that the type 

of sediment deposited did not change abruptly; 

thus, the reflectors have low to modest continuity 

and amplitude. The COST No. B-2 well drilled a sequence of calcareous, fine- to medium-grained 

sandstone, pyritic red and gray shale, limestone, 

and coal, most of which is thought to have been 

deposited in a shallow marine environment 

(Scholle, 1977a, fig. 4; Poag, 1977, p. 36). Inshore, 

along the present coast line (fig. 40), unit D was 

deposited in a nonmarine environment (Poag, this 

volume), except in North Carolina where marginal 

marine conditions existed. Interval velocities (fig. 

4 7) in unit D average about 2.3-4.0 km/s and tend 

to increase toward the thicker, more marine part 

·of the unit. Such velocity values are found in fairly 

well-indurated sandstones and shales (Gardner and 

others, 197 4) having bulk densities that range from 

2.2 to 2.4 gm/cm3• Interval velocities from the 

COST No. B-2 well for this unit range from 3.5 to 

3.9 km/s and are slightly higher than were calculated for that part of line 2 closest to the well. 

Unit E represents dominantly marine-shelf 

deposits (fig. 48) inferred to be Late Cretaceous 

and possibly early Paleocene in age. It forms a 

broad sheetlike deposit that extends eastward onto 

the Atlantic Coastal Plain (fig. 40) where marineshelf and marginal-marine conditions existed 

(Poag, this volume). The lower boundary of unitE 

is marked by onlap of basal reflectors in the 

southern part of the trough (line 11) and on the 

faulted Long Island platform (line 9), but mostly, 

the unit is in apparent conformity with the 

underlying one. The upper contact can be marked 

by downlap of reflectors from the overlying unit as 

seen on several of the cross-shelf lines, where a 

delta was probably built across part of the shelf 

during the Tertiary. On most profiles, the upper 

66 

boundary of unit E shows conformity with reflectors above and below it. 

UnitE thickens in an offshore direction (fig. 48) 

in an irregular fashion. UnitE is more than 1 km 

thick in the southern part of the trough and is 

0.5-0. 75 km thick in the northern part. Along the 

coast, the thickness is 0.33 km or less, and UnitE 

thickens to more than 0.6 km in the south. 

A marine-shelf environment is interpreted for 

the deposition of unit E on the basis of the 

moderate to high continuity of reflectors and the 

low to high seismic amplitudes. The unit probably 

accumulated as a broad sheet except at the 

seaward part of line 11, where a sigmoidal arrangement of reflectors probably indicates 

ancestral shelf-edge deposits. The COST No. B-2 

well penetrated medium-grained sandstone, shale, 

lignite, and limestone (Scholle, 1977a, fig. 4) that 

was deposited mainly under marine conditions 

(Poag, 1977, p. 36; Valentine, 1977, p. 40), though 

a 275-m interval of the section was unfossiliferous 

and was presumed to be nonmarine. Coastal wells 

(fig. 40) also indicated a marginal-marine or a 

marine-shelf environment for the equivalent of the 

section under the Atlantic Coastal Plain (Poag, this 

volume). 

Average interval velocites in unit E range from 

2.2 to 3.3 km/s-values that are in the range of 

those for sandstone and shale (Gardner and others, 

1974). The rock types penetrated in the COST No. 

B-2 well have interval velocities that range from 

2.6 to 3.0 km/s (Smith and others, 1976). These are 

similar to, though slightly less than, the values on 

line 2 (3.2-3.05 km/s). 

The next higher unit, F (inferred age: Paleocene 

to middle Oligocene), is also probably of marine 

origin, has a range of interval velocities from 1.9 to 

2.6 km/s, and attains a maximum thickness of 0.5 

km under the middle part of the shelf off Delaware 

(fig. 49). Reflectors within the unit are mainly 

parallel (table 1) except off Delaware and southern 

New Jersey, where a sigmoidal and obliqueprogradational arrangement of the reflectors is 

present. The contact at the base of unit F is easily 

distinguished in many areas (fig. 50) because of 

downlap by reflectors in the lower part of the unit, 

but some onlap also is present where the unit thins 

adjacent to the coast. The contact at the top of unit 

F is also easily discerned (fig. 50) because of 

downlap onto the unit by the overlying Unit 

G-particularly at the seaward ends of the crossshelf lines. 
~5 ~--- ----· ............ . ,.,......-- . o.!>>t-11': • 

-...... 

··~····"·. ''\ ~·· ... . 'o.V .. 

·o:. ..... ~ . 200m 

20 40 60 80 fOOKM 

A 

EXPLANATION 

\\\\\ Nonmarine ·. 

~ 

Vo.A.AA.} . Marine shelf · ... \.•\i\,r~ . . 

--=--== Predominantly · ---- shale(shelf) 

B 

0 20 40 60 80 fOOKM / 

/ 

200m / 

c 

FIGURE 48.- Maps showing characteristics of unitE (see fig. 39) in the Baltimore Canyon Trough area. A, Thickness, in kilometers. 

B, Depositional environment. c,...averaged interval velocity, in kilometers per second. In A, the dots indicate control for 

thickness. Contours are dashed where seismic data were difficult to interpret. In B, numbers represent USGS seismic lines 

shown in figure 1. In C, velocity values are the arithmetic mean of values at 3-5 shotpoints between black lines. Asterisked (*) 

interval velocities were calculated for areas where the boundaries of the unit were difficult to pick; these values, therefore, are 

only approximate. 

67 
.3km • 

200m 

0 20 40 60 60 fOOKM / 

""' A 

0 20 40 60 60 fOOKM I I I I I I 

B 

FIGURE 49.-Maps showing characteristics of unit F (see fig. 39) in the Baltimore Canyon Trough area. A, Thickness, in kilometers. 

B, Depositional environment. C, Averaged interval velocity, in kilometers per second. In A, the dots indicate control for 

thickness. Contours are dashed where seismic data were difficult to interpret. Area between dashed lines in B, is where deltas 

probably prograded seaward during deposition of unit F. In B, numbers represent USGS seismic lines shown in figure 1. InC, 

velocity values are the arithmetic mean of values at 3-5 shotpoints between black lines. Asterisked (*) interval velocity was 

calculated for an area where the boundaries of the unit were difficult to pick; this value, therefore, is only approximate. 

68 
II) 

0 

z 

0 

u 

w <:; II) 

<:.0 ~ 

u.i 

~ 1-

_. 

w 

> 

~ 1-

>-

~ 

~ 

0 10 KILOMETERS 

NORTHWEST SOUTHEAST 

0 

,J 

FIGURE 50.- An enlargement of a part of figure 38 Oine 6) to show the delta built during accumulation of unit F as an oblique progradation of the 

ancestral shelf in a seaward direction (east). Top and bottom of unit F are shown by solid lines. Location of section for figure 38 is shown 

in figure 1. 
The reflectors in unit F show low to high continuity and moderate to high amplitudes. The pattern of the reflectors from most of the shelf suggests deposition on a marine shelf where 

presumably clastic sediments accumulated under 

varying energy conditions (well-bedded sequence 

near line 2; less well stratified sequence on lines 3 

and 11). Off Delaware, the arrangement of the 

reflectors in a sigmoid or oblique-progradational 

pattern and the change to a possible nonmarine sequence at the inshore end of line 10 suggest that a 

delta may have existed off that area during the early Tertiary. Coastal stratigraphy for this interval 

shows no evidence for the onland continuation of 

this delta. In Delaware, the Piney Point Formation 

of Eocene age (Talley, 1975) is a marine glauconitic 

sand, unconformably overlain by the Chesapeake 

Group of Miocene age. Possibly the delta formed 

offshore during the Oligocene when part of the 

Coastal Plain was being eroded. As can be seen 

from the isopach map (fig. 49), unit F is thickest 

near the delta (greater than 0.5 km) and thins away 

from there. Elsewhere on the shelf, unit F is inferred to be 0.1-.4 km thick. Near the present shelf 

edge on line 11, Unit F exceeds 0.5 km in thickness 

and is thought to have formed as an ancient shelfedge deposit because of the sigmoidal arrangement 

of reflectors at a position seaward of a presumed 

marine shelf (fig. 49). 

Averaged interval velocities in unit F range from 

1.9 to 2.6 km/s, but are mainly 2.2 to 2.4 km/s. In 

this unit also, higher values are toward the outer 

edge of the shelf. The lithologies under the shelf 

are known in two places. Under the New Jersey 

shelf, 0.3 km of shale, claystone, and argillaceous 

limestone was penetrated in the COST No. B-2 

well, and 20 m of fine-grained silty glauconitic sand 

and gray-green micaceous shelly clay (middle to 

lower(?) Eocene) was penetrated in AMCOR 6011 

(11 km east of Barnegat Inlet, N.J.). Rocks in this 

interval have also been dredged and drilled on the 

Continental Slope (Weed and others, 197 4), where 

they formed in deep water, not unlike their present 

environment (Poag, 1978). 

The overlying unit (G) is inferred to be marine, to 

be as much as 1 km thick, and to be late Oligocene 

to early Miocene in age (fig. 51). The lower boundary of unit G onlaps the truncated edge of the 

underlying unit toward the inner part of the shelf. 

Under the middle and outer parts of the shelf, unit 

G downlaps the older unit, building a broad flat 

sedimentary apron across the shelf. An upper 

boundary can be distinguished on most lines; but 

on part of lines 2, 6, and 10, it is not clear enough 

to be delineated (dashed area surrounding line in 

fig. 51). Where the upper boundary can be 

distinguished, lower reflectors of the unit above 

unconformably overlie the truncated reflectors in 

the top of unit G, or the boundary is marked by apparent channeling of unit G. Most sections show 

that a parallel arrangement of reflectors though a 

sigmoid or complex oblique arrangement is present 

on the outer parts of lines 2, 3, and 11. 

The acoustic facies of unit G (fig. 51) are thought 

to represent mainly those of a marine shelf, prograded at the shelf edge in the south and broadly 

prograded south of Long Island. The similarity of 

the area of broad progradation to a deltaic lobe 

was first noticed by Garrison (1970), who thought 

the lobe was Oligocene in age. At the COST No. 

B-2 well location (Scholle, 1977a, fig. 4), the 

sediments that are now shale, coarse-grained sandstone, and mudstone are thought to have accumulated in a shelf and deltaic environment 

(Poag, this volume). Unit G was drilled in AMCOR 

holes 6007B, 6010, and 6011 (Hathaway and 

others, 1976) where similar deltaic and marginalmarine environments are inferred (Poag, 1978; 

this volume) to have existed: 

70 

Unit G (fig. 51) is generally less than 0.5 km thick 

under most of the shelf, except for the northern 

seaward part of the trough, where it is as much as 

1 km thick. The increase is in part artificial, 

because on lines 2, 6, and 10, the youngest unit (H) 

is not delineated; hence, its thickness is added in 

with that of unit G. However, on line 12, the 

youngest unit is not included in the thickness 

values, and the discrepancy at intersections of line 

12 with lines 2, 6, and 10 is only between 0.1 and 

0.2 km. Therefore, the thicker accumulation in the 

northern part of the trough is probably real, 

though not as much as shown in figure 51. 

Average interval velocities in unit G are in the 

range of 1.6 to 2.5 km/s, well down in the range of 

velocities for poorly indurated shale (Woollard, 

1962, p. III-42). Sediments having this range of 

velocity have densities ranging from 1.8 to 2.2 

gm/cms (Gardner and others, 197 4); as shown by 

Woollard (1962, p. Ill-6), the same densities are 

found for equivalent age units and formations of 

Cretaceous age on the Atlantic Coastal Plain of 

New Jersey. 

Unit H (table 1) probably represents a thin sheet 

of coarse- to fine-grained clastic sediment and is inferred to be a marine-shelf deposit of late Miocene 

and younger age. On lines 2, 6, and 10, it is not 
0 20 40 60 80 IOOKM / , 

A 

0 20 40 60 80 IOOKM , / / 

c 

FIGURE 51.- Maps showing characteristics of unit G (see fig. 39) in the Baltimore Canyon Trough area. A, Thickness, in kilometers. 

B, Depositional environment. C, Averaged interval velocity, in kilometers per second. In A, the dots indicate control for 

thickness. Contours are dashed where seismic data were difficult to interpret. In B, numbers represent USGS seismic lines 

shown in figure '1. InC, velocity values are the arithmetic mean of values at 3-5 shotpoints between black lines. In area enclosed 

by dashed line on all three maps, units G and H were not separated from each other on seismic lines 2, 6, and 10. Asterisked (*) 

interval velocities were calculated for areas where the boundaries of the unit were difficult to pick; these values, therefore, are 

only approximate. 

71 
distinguished from the underlying unit (area 

enclosed by dashed line on fig. 52). On the other 

lines, the base of unit H is mainly distinguished by 

a conformable sequence of reflectors above and a 

truncated group of reflectors below. Reflectors in 

unit H downlap somewhat near the seaward shelf 

part of line 11. Reflectors in the unit are ' 

characterized by low to high continuity and by 

m,oderately high amplitude. They are mainly 

parallel or show a low angle of divergence. 

Unit His interpreted to represent a marine-shelf 

deposit (fig. 52). Progradations at the shelf edge 

are evident in the southern part of the trough (lines 

3 and 11), and the unit has broadly prograded 

across the shelf on line 2. The thickness of unit H is 

0.1-0.3 km, increasing toward the outer shelf (fig. 

52). At the AM COR holes (6007 -6012, 6020, and 

6021), the unit is mainly alternating sand, silty 

clay, and clay (Hathaway and others, 1976) and is 

approximately 0.12 km thick inshore (AMCOR 

holes 6008 and 6011) and more than 0.3 km thick at 

holes drilled on the upper slope (AMCOR holes 

6012 and 6021). AMCOR holes 6009 and 6010, near 

the outer part of the shelf, gave values of 0.185 and 

0.275 km. Thickness figures are approximations 

because the holes did not detect a conspicuous unconformity in beds of late Miocene age. Hence, I 

measured to a silty clay bed in the upper part of the 

Miocene section to obtain the thickness figures, or 

I used the entire section if sediments as old as late 

Miocene were not drilled. 

Poag (1978) postulated a marginal marine to 

lagoonal and fluvial environment for the 

Pleistocene section of the inner-shelf holes; the 

Pleistocene section offshore was formed in an inner marine-shelf and lagoonal environment. The 

Pliocene section shows similar types of environments but is thinner. Averaged interval 

velocities for unit H are between 1.55 and 1.88 

km/s. The range is similar to what Wollard (1962, 

p. III -42) has compiled for terrigenous mud and 

saturated sand and silt. Hence, poorly consolidated 

sand, silty clay, and clay fit well with velocity 

values observed. 

DISCUSSION 

Once the acoustic units are described, the 

thickness and depositional environment can be interpreted over the wider interval of a system to see 

broad trends that were present as the trough sub72 

sided. Trends in the Baltimore Canyon Trough 

area can be compared with those in the more intensively studied Scotian margin. 

If the thickness values of the lowest two units (A 

and B) are combined (fig. 53), an isopach map of 

presumed Jurassic and Triassic Systems is obtained. A part of the Upper Jurassic sequence is probably put in with the Cretaceous System, because 

the unconformity between units B and C does not 

appear to straddle this time boundary. Even with 

this discrepancy, units A and B together are more 

than 8 km thick in a depocenter areally restricted 

to the northern part of the trough. Toward Long 

Island, the sequence thins in an irregular manner 

because it fills grabens. Thinning toward the New 

Jersey coastline is rapid but it is more gradual 

toward the southern part of the trough. The facies 

for the Jurassic and Triassic Systems (figs. 43 and 

45) is thought to be mainly nonmarine sedimentary 

rocks bedded with evaporite deposits. Obviously, 

marine waters were able to extend into the trough 

although they had restricted circulation. 

During the Middle and Late Jurassic, the marine 

environment appears to have become more open, 

and reefs and banks consequently could form along 

the seaward side of the trough, probably in a 

discontinuous manner. Sand flats occupied the central part of the trough, and these probably graded 

laterally into nonmarine red beds that accumulated 

in a bordering coastal plain. 

During the Cretaceous (fig. 54), the trough was 

much broader, though the accumulation of sediment was much less. If the thicknesses of units C, 

D, and E are totaled, then 4-5 km of sediment accumulated. Most of it accumulated toward the 

outer part of the shelf (between lines 3 and 9) and 

was deposited during the Late Jurassic and Early 

Cretaceous, to judge by data from the COST No. 

B-2 well. Gradually, the system thins to between 1 

and 2 km near the coastline. The circular anomaly 

(Great Stone dome) on line 2 is, in many respects, 

similar to the Zuidwal structure in Holland- a 

buried volcanic complex also emplaced during the 

Early Cretaceous and approximately 10 km across. 

Lower Cretaceous sandstones compacted around 

the Zuidwal structure are estimated to contain 

natural-gas reserves of 42 million m3 (Cottenc;on 

and others, 1975). 

The Cretaceous units (figs. 46, 4 7, and 48) show 

two main trends: a diminishing rate of sediment 

accumulation (already mentioned), and a change 

from an almost wholly nonmarine sequence of 

clastic sedimentary rocks to almost all marine-
0 10 40 60 80 IOOKM / 

/ 

A 

0 10 40 60 80 IOOKM 

B 

0 10 40 60 80 IOOKM / 

/ 

c 

FIGURE 52.- Maps showing characteristics of unit H (see fig. 39) in the Baltimore Canyon Trough area. A, Thickness, in kilometers. 

B, Depositional environment. C, Averaged interval velocity, in kilometers per second. In A, the dots indicate control for 

thickness. Contours are dashed where seismic data were difficult to interpret. In B, numbers represent USGS seismic lines 

shown in figure 1. In C, velocity values are the arithmetic mean of values at 3-5 shotpoints between the black lines. In area 

enclosed by dashed line on all three maps, units G and H were not separated from each other on seismic lines 2, 6, and 10; the interval velocities for both units along these lines are shown in figure 51. 

73 
0 20 40 60 10 IOOKM / , 

FIGURE 53.-:-lsopach map of probable Middle and Lower Jurassic and Triassic sedimentary rocks (units A and B combined; see 

fi!5. 39) m the Baltimore Canyon Trough area. Measurements are in kilometers. Control is shown by black dots. Dashed lines indiCate areas in which seismic data were difficult to interpret. 

shelf deposits. A broad regression during the Early 

Cretaceous built the shelf seaward over the reefs 

and the carbonate bank deposits. During the subsequent marine transgressions, the shelf became 

more of a marine site of deposition as worldwide 

sea level reached a maximum (Vail and others, 

1977). 

Similarly, Cenozoic deposits (fig. 55) are broadly 

spread over the trough and adjacent Coastal Plain 

in overlapping sheets of marine and nonmarine 

sediment. The maximum thickness is along the 

outer part of the Continental Shelf, though the 

sedimentary section is much thinner than the section that accumulated during the Cretaceous. 

Despite a broad trend toward gradual lowering of 

sea level during the Tertiary (Vail and others, 

1977), subsidence in the Baltimore Canyon Trough 

was sufficient to maintain a marine environment 

over much of the area. The chiefly marine regime 

was punctuated by short intervals of sea-level 

drop, as evidenced by erosion of parts of the shelf, 

coastal swamps, and alluvial plains. Broad progradational sheets appear to have built up the shelf 

in the northern part of the trough during the 

Miocene and Pliocene in a regressional phase. 

The overall shape of the Baltimore Canyon 

Trough (fig. 56) is a broad seaward-opening wedge. 

The deepest (oldest) part is restricted mainly to the 

outer and more northerly part of the trough. The 

rift-block foundation of the trough is best shown by 

the irregular pattern of isopach contours south of 

Long Island. Probably, other fault basins, as yet 

not clearly delineated, exist under the Baltimore 

Canyon Trough and Atlantic Coastal Plain. As 

shown on the profiles, the trough first formed 

74 

mainly under the New Jersey shelf and gradually 

spread to the west and south as the area subsided 

after rifting (Falvey, 1974). The trough is asymmetrical in cross section, in that the slope of the . 

basement is much less under the Coastal Plain than 

it is under the shelf, where steepening of the slope 

(hinge zone?) is pronounced particularly off New 

Jersey and New York. 

The general pattern of marg}n formation deduced for the Baltimore Canyon Trough is very similar 

to that of the Scotian basin off eastern Canada 

(Given, 1977; Bally, 1976; Jansa and Wade, 1975a; 

King, 1975). As can be seen from the schematic 

cross section (Given, 1977, fig. 18g) of the Scotian 

basin (fig. 57), it has six main elements listed as 

follows: 

1. A rifted continent basement containing Permian and Triassic(?) clastic sedimentary rocks 

in prerift basins. 

2. A. rift-valley stage in the Late Triassic and 

Early Jurassic (deposition of red beds and 

evaporite deposits) following an interval of 

uplift and erosion (of elevated tilted edges of 

blocks). 

3. A first major marine transgression (Middle 

Jurassic) resulting in deposition of limestone 

offshore and nonmarine clastic rock inshore. 

4. Localization of carbonate banks over basement 

highs (Middle and Late Jurassic). 

5. A major deltaic-regressive phase in the Early 

Cretaceow~. 

6. A Tertiary (Paleocene) regression, during 

which the broad configuration of the margin 

was established by progradation of the shelf in 

overlapping wedges of clastic sediment and 
0 20 40 60 80 IOOKM 

FIGURE 54.-Isopach map of inferred Cretaceous and Upper Jurassic sedimentary rocks (units C, D, and E combined; see fig. 39) 

in the Baltimore Canyon Trough area. Measurements are in kilometers; control is shown by the black dots. Onshore data are 

provided from the wells shown in figure 40. Dashed lines indicate areas in which seismic data were difficult to int~ret. 

deposition of a lower slope-rise wedge of sediment. 

A similar pattern exists in the Baltimore Canyon 

Trough. The regressive and transgressive cycles 

are probably more prevalent in the Cretaceous 

System of the Baltimore Canyon Trough than in 

the Scotian basin. Given (1977) distinguished Permian(?) prerift basins. I am not certain that these 

exist under the Balitmore Canyon Trough or how 

one would distinguish them from the syntectonic 

rift basins of Late Triassic and Early Jurassic age 

in the trough. Notwithstanding these minor differences, I think both margins fit the models of 

Falvey (1974) and Kinsman (1975) for Atlantictype margins having a rift phase followed by a 

broad subsidence phase. The rift phase involves 

block-faulting and accumulation of red beds and 

evaporite deposits (Van Houten, 1977), and the 

subsidence phase involves subsidence and accumulation of a massive sedimentary prism over 

deposits of the earlier formed phase. 

PETROLEUM GEOLOGY 

The discussion of the petroleum geology of the 

Baltimore Canyon Trough is divided into four sections entitled (1) General Comments, (2) COST No. 

B-2 Well, (3) Shelf, and (4) Slope. Analogies between the U.S. Atlantic margin and other offshore 

areas (producing and nonproducing) that are based 

on similarities in geology and proximity (taking in75 

to account continental reconstruction) are discussed in the first section. In the second section, 

analyses of cuttings, cores, and logs from the 

COST No. B-2 well (the only deep well on the shelf 

in the Baltimore Canyon Trough) provide information about lithology, depositional environments, 

organic carbon contents and types, thermal 

maturity, reservoir rock character, and presence 

or absence of seals. The petroleum geology of the 

shelf and slope are discussed separately in the last 

two sections on the basis of information from all 

the foregoing parts of this circular. The section 

pertaining to the shelf deals primarily with potential traps. More detailed information pertaining to 

the petroleum geology of the shelf can be found in 

Mattick and others (1974), Smith and others 

(1976), Scholle (1977b), and Schlee, Martin, and 

others (1977). The petroleum geology of the slope 

is discussed in more detail than that of the shelf 

because little direct information about the 

sediments or structures of the slope is available. 

Therefore, we discuss several hypotheses of sediment processes and possible structures derived 

chiefly from geophysical data and comparisons 

with other areas. We attempt to draw preliminary 

conclusions concerning source rock, reservoir 

rock, and potential traps on the slope. 

GENERAL COMMENTS 

By ROBERT E. MATTICK and 0. W. GIRARD, Jr. 

Despite the great thicknesses of marine and continental sediments that have been identified along 
0 20 40 60 10 fOOKM 

FIGURE 55.- Isopach map of inferred Cenozoic sedimentary rocks (units F, G, and H combined; see fig. 39) in the Baltimore Canyon 

Trough area. Measurements are in kilometers; control is shown by the black dots. Onshore control is from wells shown in figure 

40. 

200m 

0 20 40 60 10 fOOKM / 

"' 

FIGURE 56.- Structure-contour map of the top of basement rocks in the Baltimore Canyon Trough area. Datum is sea level. 

Measurements are in kilometers; control is shown by the black dots. Onshore data are from wells shown in figure 40. Dashed 

lines indicate areas in which seismic data were difficult to interpret. 

the shelves and slopes of passive margins, large 

quantities of hydrocarbons have not been 

recovered from these areas. Examples are the Scotian Shelf and Grand Banks of offshore eastern 

Canada and the Northwest Africa shelves, which 

during Jurassic and Early Cretaceous time were 

close to the United States margin. 

On the basis of an examination of samples from 

63 wells from offshore eastern Canada, Bujak and 

others (1977) concluded that the Scotian Shelf and 

Grand Banks do not contain major hydrocarbon 

resources because of the nature of the organic 

material dispersed in the sediments and because 

the organic matter is immature. According to 

these authors, amorphous organic material, which 

can be transformed to hydrocarbons at relatively 

76 

low temperatures, is common only in the Upper 

Cretaceous and Tertiary intervals. In these intervals, however, the Thermal Alteration Index (TAl) 

is too low (below 2-) for significant generation of 

hydrocarbons. In pre-Upper Cretaceous sedimentary rocks, the T AI commonly reaches 2 (sufficient 

to mature amorphous-type organic material), but 

the predominant organic types in these sediments 

are herbaceous and woody- both require a T AI 

greater than 2 to generate significant quantities of 

gas and liquid hydrocarbons. Apparently some 

organic material has matured on the Scotian Shelf 

at relatively shallow depths near salt diapirs where 

locally high geothermal gradients are present. 

Also, gas has been generated in the sediments offshore of Labrador, as evidenced by several gas 

discoveries there. 
NORTHWEST SOUTHEAST 

EXPLANATION 

b/:] Major dellaic period D Tertiary regressive sediments 

~ late Cretaceous transgression 

~ Continental aust D First major marine transgression 

L••:•1 Pre~breakup rift valley sedi- I~ I Carbonate rocks and early 

ments delta clastic deposits 

FIGURE 57.- Schematic section through the northern Scotian 

basin off the coast of Nova Scotia, Canada, showing main 

stratigraphic units (from Given, 1977, fig. 18g). 

Rona (1970) compared the Eastern United 

States continental margin with the prerift opposing continental margin of Africa (Senegal basin) 

and noted that the margins appear similar with 

respect to late Precambrian, Paleozoic, and 

Mesozoic tectonic frameworks and early and middle Paleozoic, Mesozoic, and Cenozoic 

stratigraphic frameworks. To date, exploration on 

the northwest coast of Africa, both onshore and 

offshore, has been disappointing (Ayme, 1965; 

Alem, 1974; Levy and others, 1975). 

Other authors have discussed geologic observations that are pertinent to Atlantic-type margins 

and that could bear on the estimation of hydrocarbon resources in the Baltimore Canyon Trough 

area (for example, see Yarborough, 1977). These 

include the structural passivity of postrift 

sediments and possible insufficient maturation of 

organic material included in the postrift 

sediments. 

Large anticlinal structures, commonly 

associated with the entrapment of significant 

quantities of oil and gas, are sparse on the shelves 

of Atlantic-type margins. Exceptions to this are 

areas of salt diapirism, such as the Gulf of Mexico 

and the Scotian Shelf. In the Baltimore Canyon 

Trough area, the results of geophysical surveys 

and drilling (J. C. Hathaway, USGS, written commun., 1978) suggest that although some local salt 

flows exist, they are not widespread (some authors 

disagree with this interpretation; see Poag, this 

volume and Grow and Klitgord, this volume). 

However, at least one large mafic intrusion (the 

Great Stone dome, fig. 24) that deforms the 

postrift sedimentary strata has been mapped on 

the midshelf area. Seismic evidence (fig. 58) and 

the bidding activity associated with Lease Sale No. 

40 (fig. 1) indicate that small anticlinal structures 

are common along the shelf edge and slope in the 

Baltimore Canyon Trough area. In addition, good 

possibilities exist that numerous structural traps 

related to rift or prerift tectonism are present along 

the shelf edge and slope. These possible traps include drape structures formed by the compaction 

of postrift sediments over older uplifted fault 

blocks. These basement blocks may have continued 

to move throughout Cretaceous time. If so, the 

chance of finding significant anticlinal and faultrelated hydrocarbon traps would be enhanced. 

Sediments of Atlantic-type margins or divergent 

margins are considered to be thermally immature 

relative to sediments of convergent margins. 

Results from wells on the Scotian Shelf and the 

Baltimore Canyon COST No. B-2 well (Scholle, 

this volume) seem to bear this out. Analyses of 

disseminated organic matter from both areas suggest thermal immaturity with respect to generation and expulsion of economic amounts of liquid 

petroleum. However, thermal immaturity of the 

upper 4 or 5 km of sediment in itself should not 

discourage further exploration. According to Yarborough (1977), the immaturity of the Cenozoic 

and Cretaceous sedimentary rocks will permit 

deep and ultradeep exploration into the yet 

untested Lower Jurassic section, speculated to be 

about 6 km thick (fig. 3). Yarborough (1977) also 

suggested the possibility that prerift and early-rift 

lake deposits (Triassic age) could contain significant amounts of sedimentary rocks rich in organic 

material. In the Baltimore Canyon Trough area, 

however, these deeply buried deposits are probably 

sealed above by anhydrite deposits (fig. 3); this seal 

could have prevented the upward migration of expelled liquids and gases. 

On the slope and along the outer edge of the 

shelf, maturation of organic material may not be a 

problem. Studies on the Scotian Shelf by Bujak and 

others (1977) indicate that the percentage of amorphous organic material, which can be converted to 

petroleum at relatively low temperatures, tends to 

77 
-:J 

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en 

0 

z 

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w 

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i= 

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w 

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3: 

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FIGURE 58. - Anticlinal structures along the shelf edge in the Baltimore Canyon Trough area as revealed by seismic profile 15. Location of seismic profile is shown 

in figure 1. The Texaco 598-1 well was the first discovery in the Baltimore Canyon Trough area. On initial tests, natural gas flowed from it at a rate of about 

479,000 m8 /day from two intervals between depths of 3,950 and 4,300 m. The Exxon 684-1 well was dry. 
increase in the direction of deep-water environments. Mattick and others (1977) suggested that 

petroleum could have been generated under the 

present lower slope and rise in basin facies rich in 

organic matter; the petroleum could have migrated 

to reservoirs in the upper slope or along the shelf 

edge. 

Another attractive target would be the Mesozoic 

shelf margin, which is below the present-day Continental Slope. Of special interest to petroleum exploration are potentially porous carbonate rocks 

that may be associated with this paleoshelf edge 

(fig. 3). The carbonate reef trends of the Edwards 

Limestone of Texas and El Abra-Tamaulipas Formation of the Mexican Golden Lane (known petroleum provinces) are good examples for comparison 

with the paleoshelf margin in the Baltimore Canyon Trough area. In addition, the paleoshelf 

margin in the Baltimore Canyon Trough area 

might be compared with the so-called Reforma 

trend in western Tabasco, Mexico, which produces 

from lower Turonian through Oxfordian bank-edge 

carbonate facies. According to Meyerhoff and 

Morris (1977), entrapment of petroleum in the 

Reforma trend is controlled not only by local structure but also by a regional updip seal of shelf and 

back-reef deposits and a downdip deep-water 

facies, which also is a prolific source rock. Proved, 

probable, and potential reserves of the onshore and 

offshore Reforma trend have been estimated at 62 

billion bbls (barrels) (Meyerhoff and Morris, 1977). 

To date, 17 wildcat wells have been completed or 

nearly completed offshore in the Baltimore Canyon 

Trough. The only significant gas discovery was in 

the Texaco 598-1 well, from which natural gas 

flowed at a rate of about 479,000 m3 per day from 

two intervals between depths of about 3, 950 and 

4,300 m (Texaco, 1978). A seismic line across the 

Texaco discovery is shown in figure 58. 

COST NO. B-2 WELL 

By PETER A. ScHoLLE 

The COST No. B-2 well (fig. 59) was the first 

deep offshore test in the Baltimore Canyon Trough 

area. The analysis of cuttings, cores, and logs from 

this well yielded information about sediment 

thicknesses. depositional environments, organiccarbon contents and types, thermal maturity, 

character of reservoir rock, and presence or 

absence of seals. 

The well penetrated 4, 772 m (15,655 ft) of 

Cenozoic and Mesozoic rocks. Lithologic and 

paleoenvironmental studies, summarized in figure 

59, indicate that the upper 600 m (2,000 ft) of section contains very sandy shallow-marine to nonmarine deposits. Between 600 and 1,800 m (2,000 

and 6,000 ft), a deeper water, finer grained section 

is present. Below 1,800 m (6,000 ft), the section 

consists of alternating sandstones and shales of 

shallow-marine to nonmarine origin. This deeper 

part of the section contains many coal and lignite 

seams. 

The Cretaceous section consists chiefly of 

relatively thick sandstone units, some of which 

have significant reservoir potential. The reservoir 

quality of this sandstone, however, deteriorates 

consistently as depth increases. The relationship 

between depth and petrophysical characteristics 

determined from electric logs, as well as from 

cores, is shown in figure 60. The porosity loss 

below 3, 700 m (12,000 ft) is largely related to compaction effects and to progressive breakdown of 

feldspar accompanied by growth of authigenic clay 

and silica cement. Generation of calcite cement is 

also important in the porosity loss, especially in 

zones that contain marine fossils or limestone. As 

can be seen in figure 60, these porosity losses, 

especially those caused by the formation of 

authigenic clay, have a drastic effect on 

permeability. Thus, below 3, 700 m (12,000 ft), few 

sandstones have more than 1 millidarcy (mD) 

permeability. 

The abundance of shales ·throughout the section 

suggests that material to form hydrocarbon seals 

is not lacking in this area, although in some intervals, the shales may be too thin to form effective 

hydrocarbon seals. 

Geochemical studies of the COST No. B-2 well 

have shown that the Baltimore Canyon Trough 

area has a relatively low geothermal gradient today and that it apparently has had a gradient as 

low or even lower throughout the Cretaceous to 

Holocene. A controversy exists concerning the 

maturity of the basal sedimentary rocks in the 

COST No. B-2 well. Data on the degree of thermal 

alteration of visible organic matter, pyrolyticdecomposition temperatures, carbon-preference 

index, and vitrinite reflectance are summarized in 

figure 61. All the data summarized in figure 61 

bear on geothermal history and indicate that the 

section down to at least 2,500 m (8,000 ft) is thermally immature and is unlikely to have yielded 

79 
Series 

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DESCRIPTION 

Sea floor 

Unconsolidated sand, gravel, 

and cloy with fragments; 

abundant glauconite 

Dense argillaceous micrite and claystone 

Medium- to coarse-grained sandstone with interbedded micrite, dolomite, dark-gray 

shale, and cool 

Gray-brown shale, abundant 

cool 

Fine- to medium-grained, whiteton sandstone 

Variegated, dark-gray-greenish, gray-reddish, brownrusty waxy shale 

Fine- to medium-grained sandstone and gray, maroon, and 

reddish-brown variegated 

shale and lignite 

T otol depth of 

well 4889.9 m 

1Consensus of Smith and others (1976), Paog (1977), 

Valentine ( 1977) 

2Paag (1977) 

3valentine (1977) 

DEPTH IN 

KILOMETERS 

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(1976) 

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FIGURE 59. -Generalized plot of lithologies and depositional environments of sediments in the COST No. B-2 

well. Modified from Smith and others (1976). 

80 
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DENSITY LOG POROSITY, 

IN PERCENT 

25 50 75 0~---L--...L---L--

0.5 

1.0 

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CORE POROSITY I 

IN PERCENT 

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PERMEABILITY, 

IN MILLIDARCIES 

0 

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FIGURE 60.-Comparison of density log curve of porosity (from Scholle, 1977a, fig. 5) with measured core porosities and empirically determined permeabilities (from Core Laboratories, Inc., as given by Smith and others, 1976) in the COST No. B-2 

well. 

81 
hydrocarbons other than biogenic methane. Data 

from the various analytical techniques are interpreted to indicate different degrees of maturity for 

the section below 2,500 m (8,000 ft). The techniques based on observations of visible organic . 

matter indicate moderate to full thermal maturity 

below 2,500 m (8,000 ft). For example, vitrinite 

reflectance values of 0.45-0.50, found at about 

2,500 m (8,000 ft) in the COST No. B-2 well, are 

generally taken as marking the earliest onset of 

liquid-hydrocarbon generation (Bartenstein and 

Teichmiiller, 1974; Hood and others, 1975; 

Vassoyevich and others, 1970). Likewise, vitrinite 

reflectance values of 0.6-0. 7 and sapropelmaturation values of 2.5-3.0, found below 3,700 m 

(12,000 ft), mark the peak rate of liquidhydrocarbon formation. Thus, such data and the 

present temperature profile in the well indicate 

that significant. liquid hydrocarbons could have 

been generated below about 2,500 m (8,000 ft.). 

Geochemical analyses of disseminated organic 

matter yield a somewhat different picture. Studies 

of extractable organic matter presented by 

Claypool and others (1977), Geochem Laboratories, Inc. (written commun., 1976), and Smith and 

others (1976) indicate that none of the sediments, 

not even those below 2,500 m (8,000 ft), are fully 

mature with respect to liquid-hydrocarbon generation. These authors concluded that although significant amounts of gaseous hydrocarbons may 

have been generated, large amounts of liquidpetroleum hydrocarbons have not yet been 

generated. 

These differences in apparent maturity found by 

means of visual and geochemical techniques are 

not easily explained. Considerable disagreement 

still exists about the exact time-temperature relations needed for oil formation and the effect of 

type of organic matter and other factors upon 

rates of formation (for example, see Tissot and 

others, 1974). Thus, the noted discrepancies may 

be due to incorrect extrapolation of maturity versus oil-generation values from other basins. Indeed, recent workers have tended to place the 

main phase of oil generation at greater and greater 

depths and temperatures (for example, Hood and 

Castano, 197 4). On the basis of such work, little 

discrepancy exists between visual and geochemical 

analyses; both would indicate only marginal 

maturity with respect to liquid-petroleumhydrocarbon generation at the base of the COST 

No. B-2 well. 

82 

The type, as well as the amount, of organic matter present in the sediments plays a major role in 

the determination of the hydrocarbon potential of 

the section. In the COST No. B-2 well, some of the 

highest organic-carbon contents (as much as 11.5 

percent) are present between 900 and 1,800 m 

(3,000 and 6,000 ft) and between 2,900 and 4,300 m 

(9,500 and 14,000 ft) (fig. 62). The interval between 

2,900 and 4,300 m (9,500 and 14,000 ft) also has the 

highest hydrocarbon and 15C + extractable contents (fig. 62). This same part of the section has a 

very significant amount of coal, especially between 

2,900 and 3,450 m (9,500 and 11,300 ft) and between 3,780 and 4,300 m (12,400 and 14,000 ft). 

The dominance of terrestrial over marine-derived 

organic matter in this interval is indicated by 

kerogen type, atomic H/C ratio, and deviation of 

the 14C/12C ratio from that of the PDB marine carbonate standard (fig. 63); this dominance of terrestrial organic matter makes the generation of 

economic amounts of liquid-petroleum hydrocarbons unlikely but allows a high potential for 

generation of wet or dry gas. 

Evidence for the presence of natural-gas 

deposits on the shelf comes from Texaco 598-1 

well (discussed in "General Comments"). Some 

evidence for the presence of natural-gas deposits 

on the slope may come from AMCOR 6021 (fig. 1). 

The upper 305m (1,000 ft) of sediment penetrated 

at this site contained significant amounts of the 

light hydrocarbons (methane, ethane, and 

propane). Although R. E. Miller and D. M. Schultz 

(written commun., 1976) believe that the methane 

is dominantly biogenic in orgin, some leakage from 

deeper natural-gas sources may exist. Several 

samples of gas-bearing mud from this borehole 

have been analyzed for stable carbon-isotopic composition of the methane. These preliminary results 

may indicate seepage from deeper parts of the section. However, because of the extremely small 

quantities of gas obtained and analyzed, the results 

should not be interpreted as unequivocal support 

for a thermogenic origin of methane (G. E. 

Claypool, written commun., 1976). 

Extrapolation of the data from the COST No. 

B-2 well in a seaward direction within the 

Baltimore Canyon Trough is somewhat speculative. Although the section from 1,800 m (6,000 ft) 

to the base of the COST No. B-2 well was 

predominantly nonmarine to marginal -marine, 

regional geology and seismic sections (Schlee, this 

volume) indicate that sections to the east and 
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• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

• • 

• 

• 

• 

FIGURE 61.-Comparison of various measures of thermal maturity as a function of depth in the COST No. B-2 well. Degree of 

thermal alteration, from Robbins and Rhodehamel (1976); pyrolitic decomposition data, from Claypool and others (1977); 

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

83 
ORGANIC-CARBON. CONTENT, 

IN PERCENT BY WEIGHT 

0.0 1 0 2.0 3.0 

0 

lSC+ EXTRACTION DATA, 

IN PARTS PER MILLION 

BY WEIGHT 

2000 4000 

96 

0 

:o 

6~ 

17.~-L~--~~~~ 

0.0 1.0 2.0 3.0 0 2000 4000 6000 

FIGURE 62.- Summary and comparison of analyses of 

organic content of sediments in the COST No. B-2 

well. Geochem Laboratories, Inc., (written commun., 1976) data are shown as bars, whereas USGS 

data are shown as circles. 

southeast are likely to be more marine. A more fully marine section could contain source rock for oil 

generation. It could also contain cleaner, better 

sorted, perhaps somewhat less mineralogically immature sandstones that would have less susceptibility to clay cementation at depth than the rocks 

penetrated by the COST No. B-2 well. Sand units 

should also be thicker and more laterally continuous in the marginal to shallow marine environments than in the terrestrial equivalents in the 

COST No. B-2 well. Thick marine shales are undoubtedly present in the shallow marine to deeper 

marine sections and would act as seals as well as 

source rocks. These possible changes in lithology 

(shoreward, seaward, and laterally from the COST 

No. B-2 well) are discussed in detail by Poag (this 

volume) and Schlee (this volume). Possible patterns 

of thermal maturity are difficult to predict, but one 

might expect geothermal gradients to increase 

toward the young major rifts and possible intrusive 

rocks of the shelf edge and slope. Structures 

available for hydrocarbon entrapment in the 

Baltimore Canyon Trough area are discussed in 

the next two sections of this volume. 

SHELF 

By ROBERT E. MATTICK and KENNETH C. BAYER 

At Lease Sale No. 40, industry's high bids were 

for tracts near the crest of the Great Stone dome 

(fig. 64). Some of these bids may have been 

prompted by seismically recorded bright spots 

(high-amplitude reflections) or dim spots (lowamplitude reflections). At the crest of the dome, 

uppermost Lower Cretaceous and Upper 

Cretaceous beds are arched at least 350 m. 

Measurements on cores from uppermost Lower 

Cretaceous sandstone penetrated in the COST No. 

B-2 well showed porosities as high as 28.7 percent 

and permeabilities as high as 1,220 mD (Smith and 

others, 1976). Where these Lower Cretaceous 

sandstones are projected to the crest of the dome 

at depths of 1,800-2,200 m, they could serve as 

good reservoirs, and could be sealed by overlying 

Upper Cretaceous shale (Scholle, this volume). 

Despite early optimism as to the hydrocarbon 

potential of the Great Stone dome, to date three 

dry holes, Shell 632-1, Houston Oil and Minerals 

676-1, and Conoco 590-1, have been drilled 

downdip from the crest of the structure. Data from 

these wells have not yet been released. The crest of 

the structure is yet to be drilled. 

84 
·PYROLITIC 

RELATIVE KEROGEN liYDROCARBON/ORGANIC 

TYPE AND ABUNDANCE, CARBON, ATOMIC H/C RATIO 

813Cp08 PER MIL IN PERCENT IN PERCENT IN KEROGEN 

50 0 50 100 0 4 .6 .8 1.0 1.21.4 0 -27 -26 -25 -24 -23 

0 0 0 

0 

® • (}4 

0 

0 ® • u 

0.5- 0 • 0 0 .5 0 0.5- 0.5 

0 -----.<) 

0 0 

® 

0 ® 0 

1.0 1.0- 1.0- 1.0 0 ® eo 

0 ® 

0 ® 0 ·------ • ® 

0 ® 

1.5 1.5- 0 1.5- ® 1.5 •a-----. --- 0 ® 

0 ® 

® 

® 0 ....._____. 

2.0 2.0- 2.0- ® 2.0 V) 0 • 

"' ® o--e w 

1-

w ® .__ :E ® 0 •• 0 _, 

;;;;: 2.5 2.5- 0 2.5- ® ® 2.5 0 

~ ® o-• 0 ® 

:i 0 • 1- ® 0.. • w ® o---e 0 3.0- 0 

3 3.0- 3.0 .0 ® o---e • ® 

® ~-0 •• 0 ® 

3.5- 0 ® ~·--· 3.5 3.5- 3.5 o--•-• ® o-•----4 

0 ® o--• ® .. 0 ® o--•-• 4.0 4.0- 0 4.0- ® 4.0 o--•-· 0 ®® • • ® 0 0 •• ® • • 0 ® • 4.5 4.5- 0 4.5 - ® 4.5 • ® • 0 ® ..__. 0 0 ® 

5.0 5.0- 5.0- 5.0 

Amo'Phous ll:lE[l 0 Saturated hydrocarbon • Kerogen 

Herbaceous ~ e Total extract 

Woody l:'liiJ 

Cooly 

-

FIGURE 63.- Summary and comparison of type of organic matter in samples from the COST No. B-2 well. Data in the first column 

are from Geochem Laboratories, Inc. (1976); second column, from Scholle (1977b); third column, from Amoco Production Co. (J. 

A. Momper, written commun., 1976); and the last column, from Phillips Petroleum Co. (J. G. Erdman, written commun., 1976). 

85 
EST PROJECTION OF 

w SHOTPOINT NUMBER COST NO. Br-2 WEll 

PROJECTION OF 

TEXACO 598,-1 WEll 

EAST 

101 300 500 700 900 1100 L 

O~====~====~====~====~====~~~~~~~~~j O 

2 2 

Vl 

~ 

w 

1-

w 

::E 

0 

..... 

:;;;: 4 4 

~ ~ :i ()) ...£. f 1- v':A c.. 

w "' v + 0 ~ (" 

~ (" + 

6 6 -t-~+ 

...A(I\f 

8 VERTICAL EXAGGERATION X13 8 

EXPLANATION 

~Limestone 

D Sand and sandstone 

~ Shale, siltstone, and claystone 

Unconformity 

Potential hydrocarbon 

trap 

FIGURE 64.- Diagrammatic cross section illustrating potential hydrocarbon traps (shown in black) in the Baltimore Canyon Trough area. The figure is based on an interpretation of seismic profile 2. Location of this 

profile is shown in figure 1. SS, Sandstone. 

Although the Great Stone dome is probably the 

largest intrusive body in the Baltimore Canyon 

Trough area, other smaller intrusive bodies may 

exist. For example, about 25 km west of the Great 

Stone dome, another piercement structure, at a 

depth of perhaps 7,300 m, appears on seismic records (fig. 64). Furthermore, in the northern and 

central Baltimore Canyon Trough area, a trend of 

positive magnetic anomalies parallels the seaward 

edge of the Continental Shelf (U.S. Geological 

Survey, 1976). These anomalies may represent intrusions emplaced along a zone of weakness near 

the shelf edge. 

Other types of potential traps include unconformities, updip pinchouts, and fault-related traps 

(fig. 64). In areas where local unconformities are 

associated with intrusive features such as the 

Great Stone dome, the intersection of porous 

86 

reservoir beds beneath an unconformity with adequate sealing beds above the unconformity could 

be a locus of hydrocarbon traps. 

Updip pinchouts of Jurassic and possibly Lower 

Cretaceous clastic units against crystalline basement rock offer possibilities for stratigraphic 

traps. Significant lateral variations in porosity and 

permeability could likewise exist in marine carbonate rocks of Jurassic and Cretaceous age near 

the shelf edge. Such porosity and permeability 

changes could be found in fractured limestone and 

porous reef material and could include secondary 

porosity in back-reef dolomites. Downdip facies 

changes, from marine clastic to carbonate rocks 

and from marginal marine sandstone to shale, 

could also provide stratigraphic traps. The results 

from the COST No. B-2 well indicate that if such 
NORTHWEST SOUTHEAST 

SHOTPOINT NUMBER 

630 

500 

600 c/) 

c 

z 700 

0 

u 

w 800 V) 

::::; 

900 .... 

~ 

~ 1000 

w 

~ 

i= 630 .... 

w 

> 500 ~ 600 1-

>-

~ 700 

0 800 ~ 1- 900 

1000 

640 650 660 670 

640 650 660 670 

EXPLANATION 

~~Oij Shale 

F(.:::·:'·J Sandstone, porosity 30--35 percent, 100 percent water saturated 

L "d Sandstone, porosity 28 percent, 70 pe<cent 

water saturated, 30 percent gas saturated 

680 690 700 710 720 730 

A 

680 690 700 71{) 720 730 

B 

FIGURE 65.- Geologic model derived from seismic bright spot. A, Section of seismic record recorded between shotpoints 630 and 

730 (10 km) on seismic profile 2 in the Baltimore Canyon Trough. Record has been processed to preserve the true amplitude of 

reflections. A bright spot is the darkened horizon at 0.8 s (depth of 620 m). B, Geologic model derived from the seismic section 

by Brad Pitney of Digicon Geophysical Corp., Houston, Tex. 

traps exist, they would most likely be very near the 

edge of the Continental Shelf. 

Seismic evidence indicates that at least one major down-to-the-basin fault exists near the shelf 

edge in the Baltimore Canyon Trough area. The 

first well to discover natural gas in the Baltimore 

Canyon Trough (Texaco 598- 1) is on the downthrown side of this fault (fig. 64). Whether such 

faulting is widespread and might be associated 

with hydrocarbon traps is unknown at present. 

Evidence of gas accumulation is sometimes 

given by high-amplitude reflections (bright spots) 

from the reservoir containing the gas. The change 

in velocity caused by gas accumulation gives rise 

not only to bright spots but also to secondary effects, such as delays of deeper reflections and 

changes in reflection character near the boundary 

of the reservoir. A geologic model derived from an 

amplitude anomaly is shown in figure 65. If our 

estimates of the poorly understood lithologies are 

87 

correct, the bright spot recorded at about 0.8 s is 

from the base of a gas sand 60 m thick and enclosed 

in shale. On the basis of amplitude of the reflection, 

the porosity of the gas sand is estimated to be 28 

percent; the water saturation is estimated to be 70 

percent, and the gas saturation, 30 percent. The 

apparent ratio of water saturation to gas saturation indicates a dirty sand having small likelihood 

of commercial production even if the anomaly is 

caused by natural gas rather than organically 

derived methane. 

SLOPE 

By RoBERT E. MATTICK, PETER A. SCHOLLE, and 

0. W. GmARD, Jr. 

ORGANIC MATTER IN SLOPE SEDIMENTS 

Even though present-day sediments of the U.S. 

Atlantic lower slope and rise can be expected to 
have a relatively low content of peserved organic 

material, older sediments from similar paleobathymetric positions could be significantly rich in 

organic carbon (Mattick and others, 1978). Core 

samples from AMCOR 6021, drilled on the slope 

off New Jersey (fig. 1), contained significant 

amounts of methane, ethane, and propane (Hathaway and others, 1976). Although the methane is 

probably dominantly biogenic in origin, some 

leakage from deeper natural gas sources may exist 

(Scholle, this volume). 

One of the most interesting speculations about 

potential source rocks beneath the present lower 

rise and abyssal plain is concerned with the thick 

(200-300 m) black hemipelagic shale of Cretaceous 

age that is rich in organic material and that has 

been found by drilling at many DSDP (Deep Sea 

Drilling Project) sites in the Atlantic. Lancelot, 

Hathaway, and Hollister (1972) discussed the total 

organic content of this shale from DSDP holes 101 

and 105-one shale sample contained as much as 

14.8 percent organic material. 

Analysis of four samples of similar black shale of 

Albian and Aptian age from DSDP hole 391 (Geotimes, 1976) in the Blake Basin provided encouraging, but not optimistic, results. According to G. E. 

Claypool (USGS, written commun., 1976), all the 

samples are thermally immature, but at least one 

of the samples contains a sufficient amount of proper organic constituents to constitute a source bed 

if it were buried to depths of about 3 km. The 

results of his analysis are shown in table 4. 

Apparently, a reducing environment was 

widespread in the early Atlantic from Neocomian 

time, and data from DSDP cores and onshore 

samples (Scholle and Arthur, 1976) indicate that 

another reducing environment was widespread 

during the late Cenomanian and Turonian. 

Whether the shale beds penetrated by the DSDP 

holes exist beneath the U.S. Atlantic Slope and 

could have been a source of petroleum is unknown, 

even though small quantities of light extractable 

hydrocarbons were "distilled" by the injection of 

diabase sills into similar black shales off the coast 

of northwest Africa (Geotimes, 1975). With this 

one exception, the Cretaceous shale, where found 

by drilling, has never been subjected to high 

enough temperatures to generate significant quantities of petroleum. If, however, these rocks were 

deposited beneath the present upper rise and lower 

slope, sufficiently high temperatures could have 

been reached at depth. The temperature-gradient 

data of Robbins and Rhodehamel (1976) combined 

with the thermal window of Pusey (1973) suggest 

that petroleum could be generated beneath the rise 

between 2.5 and 5 km below the water-sediment interface. 

RESERVOIR ROCK ON THE SLOPE 

The present-day Continental Shelf is mantled by 

quartzose sand and some gravel brought there during lowered sea level in the Pleistocene and 

reworked during the Holocene (Schlee, 1973; Hollister, 1973). Seaward, on the slope and upper rise, 

terrigenous material becomes less dominant, and 

biogenic carbonate material forms a major sediment fraction (Hiilseman, 1967; Milliman and 

others, 1972). According to Curray (1975), much of 

the present-day sediment on the continental margins is relict from lowered sea levels of the Pleistocene and is not in equilibrium with the current environment. Therefore, in order to infer past 

sediment-distribution patterns, especially the 

distribution of potential reservoir lithologies, the 

rock record and the processes that influence sediment distribution in deep-water environments 

must be examined. 

TABLE 4. -Summary of combustion and thermal analysis of Cretaceous sapropels collected during DSDP Leg 44 from site 391, 

Blake Basin 

[From George Claypool, USGS (written commun., 1976)] 

Sample 

391-8-2 

391-10-3-================ 

391-11-2 

391-12-4 ================ 

Depth (m) 

785 

901 

927 

958 

Or~anic carbon (weight percent) 

0.2 

2.5 

.3 

1.2 

1 0°-350° C part of hydrogen-flame-ionization detector (HFID) response. 

Thermal analysis/pyrolysis 

Pyrolytic oil yield Oil yield as percent- age of orgamc carbon Gallons per ton 

88 

0.05 

1.98 

.02 

.16 

Weight percent 

0.019 

.76 

.008 

.062 

9.5 

30.4 

2.7 

5.2 

Oil content' (weight, in ppm) 

23 

122 

6 

31 
Sediment transport from shallow-water to deepwater environments is primarily by (1) turbidity 

currents, (2) turbid-layer transport, and (3) slumping and sliding. Of these mechanisms, turbidity 

currents transport significant amounts of potential 

reservoir-rock material, such as sand and perhaps 

some gravel, to deep-water environments. The 

sediments transported by turbidity currents, 

however, tend to bypass the slope and are deposited on the rise and abyssal plain in large submarine 

fans at the mouths of submarine canyons. 

In contrast, turbid layers, which are low-velocity 

clouds of muddy water immediately above the sea 

floor, transport large quantities of fine-grained 

sediment across the shelf to the slope. In general, 

the fine-grained material transported in turbid 

layers will not form effective reservoir rocks. 

Submarine slumping and sliding is most prevalent on the Continental Slope. However, because 

this process involves sediments already deposited 

on the slope, most of the slumped material may 

consist of fine-grained deep-water sediments. In 

contrast, slumps and slides along shelf margins 

dominated by reef deposition could be a means of 

transporting potential reservoir rocks into deeper 

water environments. 

Bottom sampling and drill-hole data indicate that 

Cenozoic sediments deposited on the present slope 

and upper rise, except Pleistocene sand, do not 

axes where sand was funneled by gravitational 

flow) on the present slope and rise are poor. 

However, we don't believe that the entire U.S. 

Atlantic Slope province lacks hydrocarbon potential simply on the basis of conclusions about the Cenozoic section. According to Schlee and others 

(1976), the present slope surface is a fairly recent 

bathymetric feature, and we point out below in this 

section that the shelf edge during Early Cretaceous time probably was 20-30 km seaward of its 

present position. The present Continental Slope, 

therefore could be underlain by coarse-grained 

sediments deposited on an older shelf surface. If 

the slope is underlain by coarse-grained sediments, 

the younger clays deposited on the present slope 

surface could provide an impermeable seal for 

Cretaceous and Jurassic reservoirs. Peter Vail 

(written commun., 1976) has inferred several 

worldwide drops in sea level comparable to those 

that took place during the Pleistocene. Indeed, 

Cretaceous sea-level fluctuations have been estimated to involve changes in water depth of more 

than 500 m (Hays and Pitman, 1973)-far greater 

than any Pleistocene oscillations. By analogy with 

the Pleistocene, reservoir material may have been 

deposited on the slope during these periods of 

lowered sea level. 

POTENTIAL HYDROCARBON TRAPS ON THE SLOPE 

contain significant amounts of favorable reservoir As indicated by Poag (this volume) and Schlee 

material. In one of five holes recently drilled on the (this volume), what is now the Continental Slope is 

slope (Hathaway and others, 1976), well-sorted and probably underlain by sequences of Lower Cretaround quartzose sand of Pleistocene age was pene- ceous and Jurassic sedimentary rocks deposited on 

trated at a depth of 76 m. In a second hole, medium a carbonate platform or possibly atop high-standto coarse sand of Pleistocene age was penetrated ing basement blocks (figs. 66 and 67). The landat a depth of 104 m. Apparently, the Pleistocene ward shift of the present shelf edge relative to the 

sands were deposited directly on the slope at a buried paleoshelf edge is about 20-30 km. 

time when the Continental Shelf was above sea During Early Cretaceous or Late Jurassic time, 

level. However, according to Emery and Uchupi reef growth apparently began at the edge of the 

(1972), most of the sediments sampled to date on paleoshelf (fig. 67). As the continental margin 

the U.S. Atlantic Continental Slope are green silty slowly subsided, reef buildup reached a height of 

clays and clayey silts. perhaps 2,500 m. Deltaic sands and some shales 

The deepest hole drilled to date on the Continen- were deposited contemporaneously in the backtal Rise north of Cape Hatteras is DSDP hole 106. reef area as indicated by the Lower Cretaceous 

The cores recovered from this hole were mainly sandstones penetrated in the COST No. B-2 well. 

Pleistocene clay, silt, and fine sand to a depth of Because delta progradation and contemporaneous 

about 350 m and little if any material coarser than reef growth are, in general, incompatible, the 

clay from 350m to the bottom of the hole at 1,015 presence or absence of carbonate deposits in local 

m (Geotimes, 1970). areas in the Early Cretaceous probably depended 

This discussion suggests that the reservoir largely on the volume of local terrigenous input. 

characteristics of Cenozoic deposits (except the On seismic sections, reefs appear to be disconPleistocene sand and perhaps deposits in canyon · tinuous, and the eastern margin of the Baltimore 

89 
.Vl 

w "' 1-

w 

~ 

~ 

CJ:) I ~ 0 1-

"-

w 

0 

SHELF 

0 

3000 -

6000 

9000 

12,000-

1500 1600 

SLOPE 

SOUTHEAST )o 

SHOTPOINT NUMBER 

1700 

0 5 10 KILOMETERS 

HORIZONTAL SCALE 

VERTICAL EXAGGERATION 2X 

1800 1900 

RISE 

2000 

SEA LEVEL 

FIGURE 66.-Interpreted depth section computed along seismic-reflection line 2 (fig. 1) between shotpoints 1500 and 2000. The dashed line represents 

acoustic basement. This depth section was provided by Richard Wise of Digicon Geophysical Corporation, Houston, Tex. 
V'J 

o=: 

w 

I-

~ w 

~ ~ 

~ 

:i 

Ia.. 

w 

0 

~SHEL SLOPE RISE 

SOUTHEAST~ 

SHOTPOINT NUMBER 

1500 1600 1700 1800 1900 2000 

I I I DSDP 1108 SEA LEVEL I 

O 1:. ~-~~·•-= .-:. =----:---~- (PROJECTED) 

3000 

6000 

9000 

12,000 

- - - -

·.- .. -

EXPLANATION 

t~ j Sand and shale 

~ Reefal limestone 

I 0

0 o I Reefal debris 

-·/-

~~~/1 Oceanic basement rock 

Carbonate bank deposits built over 

high-standing basement blocks 

-;-- ••• 0 

,-, 

/_-/\_... 

'Y-~J,_., - ~ - _.,_ ,,, ,1;-\/'-· ..... , ,, --,--,_,:,~1.'',\/\;_-/~, ... ,,,/ -- '" _," ·- '-,,, --,' __ , -,_--. ·.,_; ··'-to-o'-,,,~,-,,,'~>'~ "'-,-','-, ''''''"" ,_ --~----' ,,_;,_c;;~c -,~'!<<;--,,,('~" '-'~'''';-<."~ ,. ''-.,I/-;--;,-,/_/, I'/\,~ '-~1,.\~11__1/::_.,... ~<._1/. 

0 5 10 KILOMETERS 

FIGURE 67.-A geologic interpretation of the part of seismic profile 2 shown in figure 66. 
Canyon Trough section thus shows a relatively narrow and restricted trend of bank-margin carbonate 

rocks. Some of the deltaic sand may have been funneled through channels in the reef contemporaneously with reef growth or may have been swept 

over the reef as sheet deposits during periodic fluctuations of sea level. Thus, clastic terrigenous 

sand, fine-grained pelagic and hemipelagic 

material, and reef debris were probably all 

deposited at the base of the paleoshelf. Near the 

end of Early Cretaceous time, the reef could have 

been exposed and later could have been buried by 

an influx of sediment. 

The lower half (5-6 km) of the thick sedimentary 

wedge at the base of the paleoshelf and underlying 

the present Continental Rise probably consists 

chiefly of Upper Jurassic terrigenous sedimentary 

rocks. Although little evidence exists to support 

the contention, sediments that were accumulating 

in the Baltimore Canyon Trough behind a shelfedge ridge during the Early Jurassic may have 

over-topped the ridge and been deposited at its 

base. The thickness of these inferred Jurassic and 

Lower Cretaceous sedimentary rocks indicates 

that they were deposited at high sedimentation 

rates of 100-300 m/106 yrs. These rates are one to 

two orders of magnitude higher than normal hemipelagic or pelagic sedimentation rates of red clays, 

siliceous oozes, or calcareous oozes (for example of 

sedimentation rates, see Berger, 1974) but are in 

line with normal rates of terrigenous-mud and turbidite deposition (Fischer, 1969). The low velocity 

(4-5 km/s) at which seismic waves travel through 

these deeply buried sediments indicates a scarcity 

of carbonate rocks and possibly good porosity 

throughout the entire section. The basal part of 

this section could contain a significant thickness of 

continental Triassic red beds similar to the 

deposits in down-faulted Triassic and Jurassic(?) 

basins beneath the Coastal Plain. 

The importance of the paleoshelf edge feature, 

as far as petroleum is concerned, is the fact that it 

is a large "high," which could contain zones of very 

porous carbonate rock in both reefal and carbonate 

platform material and which is bordered on both its 

landward and seaward flanks by thick sequences of 

rocks possibly rich in organic material. Furthermore, thick overlying shale beds could provide a 

relatively impermeable seal needed to trap the 

migrating fluids. In order for the paleoshelf high to 

have trapped the migrating fluids, paths of migration from the proposed source beds to the 

suspected traps must exist. Turbidite deposits 

usually consist of thin beds of alternating finegrained material and coarser sand. These thin sand 

beds are generally continuous over large areas and 

hence, hydrocarbons could have migrated essentially updip, but possibly down section, to reservoir 

rocks in the Mesozoic shelf high. Down-to-the-basin 

growth faults, which are beneath the present rise 

(fig. 67), may have interrupted the flow -of 

migrating fluids, but in places, migration may have 

followed paths along these faults or through large 

fan complexes. Similarly, on the landward flank of 

the paleoshelf complex, beds of deltaic sand, 

although less continuous than the turbidite sands, 

could have provided migration paths to charge this 

Mesozoic shelf high. 

Whether hydrocarbons, once they migrated into 

the paleoshelf high, would have been trapped or 

whether they would have leaked out is not known. 

Shales of Cretaceous and Cenozoic age are inferred to overlie the paleoshelf. If the fluids migrated 

after the deposition of these shales, the shales 

could provide the necessary impermeable seal 

above the paleoshelf margin high. Carbonate rocks 

can act as a seal under certain diagenetic conditions and as a reservoir under other diagenetic conditions. 

If hydrocarbons have been trapped in the 

paleoshelf high, we could be looking at very significant traps. According to Moody (1975), almost 40 

percent of the world's oil reserves are in carbonate 

rocks. The reef trends in the Edwards Limestone 

of Texas and the El Abra-Tamaulipas Formation of 

Mexico provide good examples for comparison 

(Bebout and Loucks, 1974; Enos, 1974; Rose, 

1963). 

92 

Excellent reservoirs may exist in back-reef, reef, 

or fore-reef facies. Back-reef sediments may have 

been deposited at or near sea level, thus allowing 

evaporite formation, dolomitization, leaching, and 

other mechanisms for forming secondary porosity. 

Such dolomitized sediments have been recovered 

by dredging from the Blake Escarpment (Sheridan 

and others, 1969). The reef, although probably initially cemented, could have formed and developed 

excellent secondary porosity if exposed to 

subaerial erosion. According to the Scientific Party aboard Glomar Challenger for Leg 44 (Geotimes, 

1976, p. 24), Lower Cretaceous reefs, banks, and 

back-reef facies in DSDP holes 390, 392, and 392A 

all showed "evidence of subaerial weathering and 

leaching by fresh water." In addition, as the Late 

Cretaceous appears to have been a time of major 

transgression, a good possibility exists that fine-
grained rocks (seals) may ove.rlie Lower 

Cretaceous reefs. 

Possible traps, other than those associated with 

carbonate facies of the paleoshelf, include (1) a 

structural high caused by draping of Upper 

Cretaceous sedimentary rocks over the Lower 

Cretaceous shelf edge, (2) pinchouts of Lower 

Cretaceous and J~rassic sedimentary rocks that 

were deposited at the base of the paleoshelf, (3) 

fault-related traps beneath the present-day slope, 

( 4) abandoned canyon-fan complexes, and (5) traps 

associated with diapiric features on the present 

slope. 

Above the Lower Cretaceous shelf edge, Upper 

Cretaceous horizons are arched as much as 300 m 

(fig. 67). This structural high, probably caused by 

draping of Upper Cretaceous sedimentary rocks 

over the Lower Cretaceous shelf edge or possibly 

over high-standing basement blocks, would be in a 

good stratigraphic position to retain hydrocarbons 

that may have migrated updip from sediment 

facies on the lower slope and rise. Deltaic sand 

deposited on the Lower Cretaceous shelf edge 

(Rhodehamel, 1977) could provide excellent reservoir material. In large delta areas such as the 

Baltimore Canyon Trough, clastic input could have 

overwhelmed the Cretaceous rise in sea level 

resulting in the deposition of massive sand sheets 

out to the shelf edge. If this happened, then Upper 

Cretaceous coarse-grained sand could interfinger 

with shale below the present slope area. 

At the base of the paleoshelf, coarse-grained 

Lower Cretaceous and Jurassic sedimentary rocks 

probably pinch out against the finer grained rocks 

or dense carbonate rocks that make up the 

paleoshelf. These stratigraphic traps, although difficult to locate by geophysical techniques, should 

not be overlooked. Again, migration of hydrocarbons from sediment facies below the present rise 

and abyssal plain could contribute significant 

amounts of hydrocarbons to traps near the base of 

the paleoshelf. In addition, good possibilities exist 

for fault-related traps in this area. Significant 

growth faults (contrast this interpretation of 

faulting with that of Grow and Klitgord, this 

volume) mapped on seismic sections, extend from 

near the basement surface, at the base of the 

paleoshelf, high up into the sedimentary section 

(fig. 67). 

If major regressions of the sea took place during 

Cretaceous and Jurassic time (as they did during 

Pleistocene), the ancestral Continental Slope may 

have been traversed by many deeply incised submarine canyons during those periods. These canyons, later abandoned, presumably would have 

been filled by coarse sediment and possibly covered 

by fine-grained material. This type of trap could be 

located by geophysical methods. Associated with 

these canyons would be major submarine-fan 

deposits. By analogy with modern areas, these 

could have many channels of coarse-grained sediment in between areas of finer grained "overbank" 

sediment. The grain-flow and turbidite sands of the 

Atlantic margin, unlike those in many turbidite 

settings, would not have a graywacke or 

litharenite composition but would likely be of 

subarkosic composition. Subarkosic rocks have 

greater diagenetic stability and a greater chance 

for high porosities and permeabilities than do 

graywackes or litharenites. 

Diapirs under the present slope could be the continuation of a diapir complex known to underlie the 

slope beneath the Scotian margin off eastern 

Canada, where Jurassic evaporite deposits have 

been drilled (Schlee, Martin, and others, 1977). At 

the present time, we can only speculate on the 

origin and potential of such structures on the U.S. 

Atlantic margin. Beneath the Scotian Slope and 

Rise, such structures are large and common, but 

their oil and gas potential is yet untested. 

SUMMARY AND CONCLUSIONS 

GEOLOGY 

The Baltimore Canyon Trough is an elongate, 

seaward-opening sedimentary basin filled by as 

much as 14 km of Mesozoic and Cenozoic sedimentary rocks. The deepest (oldest) part is mainly the 

outer and more northerly part of the trough. Apparently, the trough first formed mainly under the 

New Jersey shelf and gradually spread west and 

south as the area subsided after the rifting that 

formed the Atlantic basin. The trough is asymmetrical in cross section in that the slope of the 

basement is much less under the Coastal Plain than 

it is under the shelf where pronounced steepening 

(a hinge zone?) is present, particularly off New 

Jersey. 

The oldest sedimentary rocks (Jurassic and 

Triassic) are essentially unsampled; their 

lithologies and environment of deposition have 

93 
been interpreted (1) from seismic-reflection and 

seismic-refraction profiles, (2) by extrapolation 

from Coastal Plain sections, and (3) by analogy 

with deep wells drilled elsewhere on the Atlantic 

margin. Rocks of the Jurassic and Triassic 

Systems together are more than 8 km thick in a 

depocenter areally restricted to the northern part 

of the trough. The sequence thins in an irregular 

manner toward Long Island, where it fills grabens. 

It thins toward the New Jersey coastline over a 

short distance, but thinning toward the southern 

part of the trough is more gradual. Basal Jurassic 

and Triassic rocks are thought to be mainly nonmarine sedimentary rocks bedded with evaporite 

deposits. Obviously, marine waters were able to 

extend into the trough though they had restricted 

circulation. Indirect evidence that salt is in the 

basal Jurassic section comes from analogy with the 

Scotian Shelf and from high interstitial salinities in 

offshore core holes near Cape Hatteras. Direct 

evidence comes from the Houston Oil and Minerals 

676-1 well, which penetrated salt at a depth of 

about 3.8 km (J. C. Hathaway, written commun., 

1979). 

During the Middle and Late Jurassic, more open 

marine conditions prevailed than in the Early 

Jurassic, and carbonate banks and reefs formed 

discontinuously along the seaward side of the shelf. 

Sand flats likely occupied the central part of the 

shelf, and these probably graded shoreward into · 

nonmarine red beds that accumulated in a bordering coastal plain. Upper Jurassic rocks are largely 

thick nonmarine sands and silty shales in the nearshore and midshelf area but probably grade into 

thick marine carbonate rocks near the present 

shelf edge. 

During the Cretaceous, the shelf was a much 

broader feature than during the Jurassic, though 

the accumulation of sediment was much less- between 4 and 5 km- and most of the sediment was 

deposited during the Early Cretaceous, to judge by 

the data from the COST No. B-2 well. The 

Cretaceous units show two main trends through 

time- a diminishing rate of sediment accumulation 

and an increase in marine character of sediments. 

During the Middle and Late Cretaceous, 

calcareous sand and mud buried the shelf-edge 

reefs and spilled across them into the oceanic basin 

as worldwide sea level reached a maximum. 

Cenozoic deposits are broadly spread over the 

trough and adjacent Coastal Plain in overlapping 

sheets of marine and nonmarine sediment. The 

maximum thickness (1.5 km) of Cenozoic deposits, 

like that of Cretaceous deposits, is along the outer 

part of the present shelf, though the Cenozoic 

sedimentary section is much thinner than the 

Cretaceous section. Despite a broad trend toward 

gradual lowering of sea level during the Tertiary, 

subsidence in the Baltimore Canyon Trough area 

was sufficient to maintain a marine environment in 

much of the area. The chiefly marine regime was 

punctuated by short intervals of sea-level drop, as 

evidenced by erosion of parts of the shelf and by 

the presence of coastal-swamp and alluvial-plain 

deposits. 

Highly calcareous sediments of Paleocene and 

Eocene age are known within, as well as both 

north and south of, the Baltimore Canyon Trough 

area. Latitudinally distinctive lithofacies and 

biofacies began to be deposited during this time 

period. Oligocene beds are widespread and are rich 

in shallow-water carbonate sediments and large 

foraminifers under the southern shelf. The absence 

of Oligocene beds from much of the northern 

Coastal Plain and the presence of shallow-water 

facies to the south suggest a major regressive cycle 

of deposition. 

Deposition of clastic sediments increased during 

the Miocene and continued, although diminished, 

·through the Pleistocene. Broad progradational 

sheets appear to have built up the shelf over the 

northern part of the trough during this time. During the Pliocene, a major delta complex, 

characterized by freshwater diatom assemblages, 

formed off Virginia and Maryland. Pleistocene 

sands and silts are especially thick on the Continental Slope; apparently density and turbidity 

flows have transported large volumes of shelf 

sediments onto the Continental Slope and Rise 

through shelf-edge canyons. The only significant 

accumulations of Holocene sediments are gray and 

white sands and silts along the coastline and green 

silty clays on the Continental Slope. 

PETROLEUM GEOLOGY 

We have discussed the petroleum geology of the 

Continental Shelf in terms of five factors: (1) 

source rocks, (2) temperatures sufficient to 

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

and (5) traps or structures capable of entrapping 

n\igrating petroleum liquids or gases. 

In the COST No. B-2 well, some of the highest 

organic-carbon contents are present between 

depths of 900 and 1,800 m and between 2,900 and 

94 
4,300 m. The interval between 2,900 and 4,300 m 

also has significant amounts of coal and the highest 

contents of hydrocarbon and extractable 15C + . 

The dominance of terrestrial over marine-derived 

organjc matter in this interval means that 

economic amounts of liquid petroleum hydrocarbons were probably not formed but that a high 

potential exists for generation of wet or dry gas. 

Some supporting evidence for the presence of 

natural-gas deposits on the slope comes from AMCOR 6021, the upper 305m of which penetrated 

sediments that contained methane, ethane, and 

propane. Direct evidence of natural-gas deposits 

on the shelf comes from the Texaco 598-1 well and 

the Gulf 857-1 well. During initial tests, natural 

gas flowed from the Texaco well at a rate of about 

479,000 m3/day from two zones. 

Geochemical studies of the COST No. B-2 well 

have shown that the shelf area has a relatively low 

geothermal gradient today, and that it apparently 

has had a gradient as low or even lower throughout 

the Cretaceous to Holocene. Data from color 

alteration of visible organic matter, pyrolyticdecomposition temperatures, carbon-preference 

index, and vitrinite reflectance indicate that the 

section down to at least 2,500 m is thermally immature and is unlikely to have yielded hydrocarbons other than biogenic methane. Data from the · 

various analytical techniques are interpreted to indicate different degrees of maturity for the 

sediments below 2,500 m. The techniques based on 

observations of visible organic matter indicate 

moderate to full thermal maturity below 2,500 m. 

Studies of extractable organic matter, however, indicate that none of the sediments, not even those 

below 2,500 m, are fully mature with respect to 

liquid-hydrocarbon generation. These results indicate that although significant amounts of 

gaseous hydrocarbons may have been generated, 

large amounts of liquid-petroleum hydrocarbons 

have not yet been generated. 

The COST No. B-2 well penetrated thick sections of potential reservoir rock. The section between 1,500 and 4,900 m consists of relatively 

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

this sandstone, however, deteriorates consistently 

as depth increases, and in the section below 3, 700 

m, few sandstones have more than 1 mD permeability. 

Shales were penetrated in the section at the 

COST No. B-2 well. These rocks could p~ovide the 

95 

necessary impermeable seal required to trap 

migrating fluids and gases, although in some intervals, the shales may be too thin to form effective 

hydrocarbon seals. 

Although the sediments penetrated in the COST 

No. B-2 well were predominantly nonmarine to 

marginal marine, regional geology and seismic sections indicate that sections to the east and 

southeast probably are more marine. By analogy 

with the Scotian Shelf, a more fully marine section 

would be more likely than nonmarine to marginal 

marine sections to contain source rocks. Studies on 

the Scotian Shelf indicate that the percentage of 

amorphous organic material, which can be converted to petroleum at relatively low 

temperatures, tends to increase in the direction of 

deep-water environments. Petroleum could also 

have been generated under the present lower slope 

and rise in basin facies rich in organic matter and 

then could have migrated to reservoirs along the 

shelf edge. A more marine section could also imply 

cleaner, better sorted, perhaps somewhat less 

mineralogically immature sandstones, which would 

be less susceptible to clay cementation at depth. 

Sand units should also be thicker and more laterally continuous in a marginal to shallow marine environment than in the terrestrial equivalents found 

in the COST No. B-2 well. Possible patterns of 

thermal maturity are difficult to predict, but 

geothermal gradients might increase toward the 

shelf edge, where major faults and intrusions have 

been postulated. 

On the shelf, potential hydrocarbon traps are 

associated with diapirs, drape structures over 

uplifted fault blocks, and faults. Seismic evidence 

suggests that although these potential traps are 

sparse under the inneJ" shelf and midshelf areas, 

they are more common along the landward edge of 

the shelf-slope break. The largest structure mapped to date is the Great Stone dome. This structure, about 20 km in diameter, probably was 

caused by a mafic intrusion that resulted in the arching and erosion of at least 3,000 m of Jurassic 

and Lower Cretaceous strata. Lower and Upper 

Cretaceous strata having about 350 m of relief unconformably overlie older strata near the dome. On 

the flanks of the dome, potential traps include 

pinchouts of Lower and Upper Cretaceous strata 

and possibly deep Jurassic reservoirs that have updip seals provided by intrusive basement rock. To 

date, however, three dry holes, Shell 632-1, 
Houston Oil and Minerals 676-1, and Conoco 

590-1, have been drilled on the dome. 

Seismic evidence indicates that at least one major down-to-the-ocean fault, involving Jurassic 

through Tertiary strata, exists on the landward 

side of the shelf edge in the Baltimore Canyon 

Trough area. The first natural-gas discovery on the 

U.S. Atlantic Coast-Texaco's 598-1 well, which 

yielded 479,000 m3 of gas per day on initial 

tests-is on the down thrown side of this fault. 

Whether such faulting is widespread and might be 

associated with hydrocarbon traps is unknown at 

present. 

Drape structures related to rift or prerift tectonism along the shelf edge and slope may be 

hydrocarbon traps. These drape structures formed 

by the draping of postrift sediments over older 

uplifted fault blocks. On seismic sections, these 

structures appear to be numerous, to be about 

5-10 km wide, and to involve several hundred 

meters of relief. Movement of these basement 

blocks possibly continued throughout Cretaceous 

time, thereby increasing the chance that significant anticlinal and fault-related hydrocarbon traps 

exist. 

Although basal Jurassic sedimentary rocks probably contain thick evaporite deposits, the only 

direct evidence of possible salt flowage comes from 

the Houston Oil and Minerals 676-1 well, which 

was reported to have penetrated a significant 

amount of salt at a depth of about 3,800 m. 

However, Grow and Klitgord (this volume) 

speculate that seismic data from the lower slope 

and rise may indicate the presence of salt diapirs. 

Additional but more speculative types of traps on 

the shelf include updip pinchouts of Jurassic and 

possibly Lower Cretaceous clastic units against 

crystalline basement rock. Significant lateral 

variations in porosity and permeability could 

likewise be present in marine carbonate rocks of 

Jurassic and Cretaceous age near the shelf edge. 

Such porosity and permeability changes could be in 

fractured limestone and porous reef material and 

could include secondary porosity in back-reef 

dolomites. Downdip facies changes from marine 

clastic to carbonate rocks and from marginalmarine sandstone to shale could also provide 

stratigraphic traps. 

Seismic and indirect geologic evidence suggests 

that potential hydrocarbon traps are on the slope 

as well as on the shelf. What is now the Continental Slope may be underlain by sequences of Lower 

Cretaceous and Jurassic sedimentary rocks 

deposited above a carbonate platform or possibly 

atop high-standing basement blocks during periods 

of fluctuating sea level. The landward shift of the 

present shelf edge relative to the buried paleoshelf 

edge is 20-30 km. 

During Early Cretaceous or Late Jurassic time, 

reef growth apparently began at the edge of the 

paleoshelf. Deltaic sands and some shales were 

deposited contemporaneously in the back-reef 

area, and because delta progradation and contemporaneous reef growth are in general incompatible, the presence or absence of carbonate deposits 

in local areas in the Early Cretaceous probably 

depended largely on the volume of local terrigenous input. On seismic sections, reefs appear 

to be discontinuous, and the eastern margin of the 

Baltimore Canyon Trough section thus shows a. 

relatively narrow and restricted band of bankmargin carbonate rocks. Some of the deltaic sand 

may have been funneled through channels in the 

reef contemporaneously with reef growth, or it 

may have been swept over the reef as sheet 

deposits during periodic fluctuations of sea level. 

Thus, clastic terrigenous sand, fine-grained pelagic 

and hemipelagic material, and reef debris were 

probably all deposited on the paleoslope in front of 

the paleoshelf. 

The importance of the paleoshelf edge, as far as 

petroleum is concerned, is the fact that it is a large 

high that could contain zones of very porous carbonate rock in both reefal and carbonate platform 

material. This high is probably bordered on its 

seaward flank by at least 6 km of turbidite deposits 

likely to be rich in preserved organic material. Furthermore, thick shale beds, which apparently 

overlie the paleoshelf, could provide a relatively 

impermeable seal needed to trap the migrating 

fluids. 

In order for the paleoshelf high to have trapped 

migrating fluids, paths of migration from the proposed source beds to the suspected trap must exist. 

Turbidite deposits commonly consist of thin beds of 

alternating fine-grained material and coarser 

sand. These thin sand beds are generally continuous over large areas and hence, hydrocarbons 

could have migrated essentially updip, but possibly 

down section, to reservoir rocks in the Mesozoicshelf high. Down-to-the-basin growth faults, that 

are beneath the present rise may have interrupted 

the flow of migrating fluids, but in places, migra96 
tion may have followed paths along these faults or 

through large fan complexes. 

Whether hydrocarbons, once they migrated into 

the paleoshelf high, would have been trapped or 

whether they would have leaked out is not known. 

Shales of Cretaceous and Cenozoic age are inferred to overlie the paleoshelf edge. If fluids 

migrated after the deposition of these shales, the 

shales could provide the necessary impermeable 

seal above the paleoshelf-margin high. Also, carbonate rocks can act as a seal under certain 

diagenetic conditions and as a reservoir under 

other diagenetic conditions. 

If hydrocarbons are contained in the paleoshelf 

high, we could be looking at large traps. According 

to Moody (1975), almost 40 percent of the world's 

oil reserves are in carbonate rocks. The reef trends 

in the Edwards Limestone of Texas and the El 

Abra-Tamaulipas Formation of Mexico provide 

good examples for comparison. 

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