New Jersey Geological SurveyGeological Survey Report GSR 26

A Marine Seismic Survey to Delineate

Tertiary and Quaternary Stratigraphy of Coastal Plain Sediments

Offshore of Atlantic City, New Jersey

byJeffreyS. WaldnerandDavidW. Hall

New Jersey Department of Environmental ProtectionGeological Survey

CN-029Trenton, NJ 08625

1991

CONVERSION FACTORS

For readers who prefer to use metric units, conversion

factors for terms used in this report are listed below:

Multiply by To obtain

feet 0.3048 meters

feet per second 0.3048 meters per secondmile 1.6093 kilometers

New Jersey Genlogi¢:al Survey Reports (ISSN 0741-7357) are published by the NewJersey Geological Survey. CN-029, Trenton. NJ 08625. This report may be repro-

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CONTENTSpage

Abstract ..................................................... 1Inlroduction ................................................... 1

Acknowledgments ............................................. 1Location .................................................. 1

Marine seismic reflection ........................................... 1

Seismic velocity borehole check-shot survey .............................. 3Instrumentation ................................................. 3

Continuous seismic reflection profiling ................................. 3Navigation ................................................. 3

Interpretation .................................................. 3Time-to-depth correlation ........................................ 3Sparker data ................................................ 12Boomer data ................................................ 12

Sand ridges .............................................. 12Subbottom erosional surface .................................... 12

Conclusions ................................................... 12References .................................................. 15Glossary ............................................ inside back cover

FiguresFigure 1. Map of New Jersey showing locations of Atlantic City and the seismic survey area ..... 1

2a. Single-channel marine seismic reflection profiling ........................ 2b. Borehole seismic check-shot surveyand corresponding seismic record ............ 2

3. Representative analog profile along sparker section (line D) .................. 44. Sample of sparker section (line D) with check-shot velocity histogram and

borehole logs, well ACOW 1 .................................. 55. Sample of sparker section (line D) withcheck-shot velocity histogram and

borehole logs, well ACOW 2 .................................. 66-9. Contour maps showing elevation of:

6. Top of the cont'ming unit above the Rio Grande water-bearing zone ........... 87. Top of the confining unit below the Rio Grande water-bearing zone ........... 98. Base the confining unit below the Rio Grande water-bearing zone ........... 109. Base of composite confining unit .............................. 11

10.Representative shallow-penetration (boomer energy source) section showinganalog data and interpretation of buried channel features .................. 13

11. Map showing location of transducer traverses, buried channel, and sand ridges ....... 14

Tables

Table 1. Geologic and hydrogeologic units investigated in the Atlantic City marine seismic survey . . 72. Records of wells used in the Atlantic City marine seismic survey ................ 7

A Marine Seismic Survey to DelineateTertiary and Quaternary Stratigraphy of Coastal Plain Sediments

Offshore of Atlantic City, New Jersey

ABSTRACT

A high-resolution marine seismic survey covering 19 square miles offshore of Atlantic City. New Jersey.identified four geologic horizons along with bottom and subbottom features in the upper 1000 feet of Tertiaryand Quaternary sediments. Two sets of data were collected on a survey grid consisting of 100 to 120 line-miles

of sparker and boomer profiles. The data were used in conjunction with offshore drilling, onshore borehole,and onshore geophysical data to determine the seaward characteristics and extent of units of the KirkwoodFormation and contiguous units. The boomer prof'd_ also revealed a shallowly buried channel and two sandridges. The geophysical interpretations were used to position two offshore monitoring wells in the 800-footsand aquifer of the Kirkwood Formation.

INTRODUCTION

The New Jersey (N. J.) Geological Survey, with tech- trending survey lines, spaced at one-mile intervals, werenical assistance provided by the New Jersey District of the approximately parallel to the southeastward regional dip.U. S. Geological Survey, Water Resources Division, and Northeast-wending traverses were roughly parallel to thethe U. S. Geological Survey, Branch of Atlantic Marine regional strike and shoreline, ranging from half-mile inter-Geology, conducted a marine seismic investigation off the vals nearshom to one mile intervals farther offshore.coast of Atlantic City, New Jersey, in 1985. The purposesof the seismic survey were to: 1) locate potential shallowgeologic hazards such as gas pockets, 2) delineate the off-

shore regional hydrostratigraphy, and 3) position two off-shore ground-water monitoring wells.

Acknowledgments

We acknowledge the assistance of Philip B. Duran and

Gary J. Barton, both formerly of the New Jersey District ofthe U. S. Geological Survey, in obtaining seismic equip-ment, aiding in data collection, and collecting check-shotdata at the two offshore wells. The U. S. Geological Survey,Branch of Atlantic Marine Geology, supplied the marineseismic equipment and operations technicians, Kenneth F.Parolski and John West. We also thank William Eisele,William E. Suoninen, Captain Lewis Eggert, and Alan

Johnson of the NJ. Geological Survey for lending their AREAexpertise and for the use of the Richard J. Sullivan researchvessel.

Location Figure 1. Map of New Jersey showing locations of AtlanticThe seismic survey grid extended from 0.5 to 5.7 miles City and the seismic survey area

off the coast of Atlantic City, N. J. (fig. 1). Four northwest-

MARINE SEISMIC REFLECTION

Marine seismic reflection enables the geophysicist to phones, located near the ocean surface. The method dependsdetermine geologic structure beneath the water surface by upon the transmission of pressure waves and their reflection

measuring the behavior of acoustic waves transmitted from from earth layers of different acoustic properties (fig. 2a).a seismic source at the water surface and reflected from A reflection may be caused by a difference in water content,bottom and subbettom features. The reflected response is sediment density, or small differences in lithology, but itdetected by pressure-sensitive transducers, called hydro-

SEISMIC SEISMIC

SOURCE RECEIVER OCEAN

,._ SURFACE

REFLECTION '_

INTERFACE /

REFLECTION _

INTERFACE _ -

Figure 2a. Single-channel, continuous-refection, marine profiling operation and corresponding survey record (analog). Theanalog record (at right) shows as shades of gray which correspond to reflected signal amplitudes (not recognizable at thissize). Interpreted reflected interfaces have been highlighted in white.

SHOTPOINT

OCEAN____ _

SORFACE 4 GEO "ONESENSOROCEAN _ FIRST REFRACTION

FLOOR _ _ -- INTERFACE

SECOND REFRACTION

INTERFACE

_. _ -- BOREHOLE

SEISMIC RECORD

SENSOR DEPTH _-_ _.*_

*OREASES"_ SECOND_,_ DIRECT ARRIVAL

TIME INCREASES REFRACTION FIRSTINTERFACE REFRACTION

INTERFACE

Figure 2 b. Borehole seismic check-shot survey array showing the geometry of a three-layer case and the corresponding seismicrecord. From these data, interval velocities can be calculated from the arrival times of the initial events.

usually results from gross changes in sediment type (Elliott Seismic velocity borehole check-shot survey

and Wiley, 1975). A check-shot survey is a method of determining theIn seismic profiles, the depths to reflecting surfaces are velocity of strata as a function of depth by lowering a

represented as a function of time. Depth information can be geophone into a borehole and recording the energy arrivalsobtained by converting the two-way traveltime values into from a shot point at the surface (fig. 2b). Seismic data aredepth, using velocities calculated from seismic reflection or recorded at set depths, from which interval velocities are

refraction data, borehole sonic logs, or seismic velocity calculated. The interval velocities can then be used to con-borehole check-shot surveys. Velocity information for this vet1 two-way travel limes (from the seismic profdes) to depth.survey is based on onshore seismic-reflection data, sub-

sequently rechecked with borehole check-shot surveysfrom offshore monitor wells.

INSTRUMENTATION

Continuous seismic reflection profiling passes of 150-1000, 500-1000 and 500-1500 hertz for the

Marine seismic data were collected from 21 to29April boomer prof'des and 100-400 to 100-500 hertz for the1985 aboard the N. J. Geological Survey research vessel sparker profiles. Resolution was about 3-5 feet for theRichard J. Sullivan. High-resolution profiles of the shallow boomer prof'des and about 10-15 feet for the sparker profiles.

sediments were needed to assess possible geologic hazards The unfiltered analog data were recorded by an eight-encountered in drilling offshore wells. A second set of track Hewlett-Packard 3968A Instrumentation recorder. An

profiles was collected using a higher-energy, lower-frequency event-time recorder (EPC 312 Record Annotator) correlatedsystem in order to obtain deeper peneteration. Accordingly, the data on tape "3 real time.each trackline was run separately with the two systems.

Analog profiles were generated using an EPC GraphicA boomer system (Ferranti O.R.E. Geopulse) was used Recorder. The sparker array sampled at 1-second intervals

for high-resolution profiles of the upper 300 feet of sedi- with a half-second recording (sweep) time. The transducerments. The transducer was powered by an EG&G Seismic array sampled at half-second intervals and was recorded at

Energy Source (234) generator at 200 joules. Seismic data a quarter-second sweep. Examples of sparker and trans-to depths of 1800 feet were collected with an 800-joule ducer analog records, together with their stratigraphic inter-sparker array and a Teledyne Exploration sparker energy pretation, offshore check-shot velocity histograms, andsource, borehole geophysical logs are shown in figures 3, 4, and 5.

An array of hydrophones (Del Norte), connected in

series-parallel, detected the reflected acoustic signals. A Navigation

Geopulse Receiver (ORE 5210A) with time-variant gain Navigational positioning was by loran-C. Measuredwas used for the high-resolution shallow data. An In- loran time delays were interfaced with a real-time recordernerspace Preamplifier/Filter Model 202 with a TSS Model on digital tape for actual positioning during data acquisition.307B amplifier and time-variant gain were used with the Fixes were plotted every five seconds.sparker system. Analog filters were variably set at band-

INTERPRETATION

Time-to-depth correlation others (1984). Interval velocities from onshore data were

The offshore reflectors were correlated with known calculated using the formula of Dix (1955):

stratigraphic horizons by: 1) extrapolating the depths off- Onshore stratigraphic depths were obtained from threeshore using the regional dip, and 2) calculating interval nearby wells (well nos. 3, 4, and 5)(table 2, figs. 6-9). Thevelocities and corresponding reflection coefficients. Inter- observed time values for the seismic profiles were convertedval velocities were by Miller and Dill (1973) from a bore- to depth by using the onshore interval velocities and off-hole 3 miles offshore of Little Egg Inlet, from onshore shore velocity data (check-shot surveys from wells no. 1andseismic reflection velocity tests collected by the N.J. no. 2). Each reflector was conelated along and betweenGeological Survey, and from check-shot surveys at the two profdes.offshore monitoring wells. The onshore seismic reflection

survey was 1 mile inland from the study area. High- Sparker dataresolution reflection velocity and depth information wereobtained for depths less than 1000 feet using methods The N. J. Coastal Plain consists of unconsolidated,detailed in Hoffman and Waldner (1986) and Hunter and semiconsolidated, and less common consolidated deposits

of sand, silt, and clay ranging in age from Cretaceous to

3

HYDROSTRATIGRAPHIC ACOW no. I ACOW no. 2 TimeINTERPRETATION v v (milliseconds)

SEA LEVEL -- I _ --

100 -_

200

100 --

300 Top of the ¢onfinin 0 unit above theRio Grande water-bearing zone

4OO

_" 500Top of the confining unit below the

_" Rio Grande water-bearing zone 200

>600

u_ Base of the confin_lg unit below Uleo_ 700 Rio Grande water-bearing zone

800 -o 300

900 Base of the composite confining unit

1000

1100 400

1200

1300

50O

Figure 3. Represen_five an_og profile _ong sparker section (line D) approxima_ly parallel to dip.In_rpmted _flection interfaces highlighted by shading.Loc_ions of offsho_wells ACOW no. 1and ACOW no. 2 projec_d _ section. Dep_ sefle approxim_e, based on the average velocity to the fourth (deepes0 reflector. Horizon_l scfle 1:50000.

4

CHECK-SHOT GAMMA GAMMA-GAMMA NEUTRON RESISTANCE

HYDROSTRA]:IGRAPHIC ACOW no. 1 VELOCITY RADIATION DENSITY RADIATION ohmsINTERPRETATION

SEA LEVEL, (1000 Wsec) increase increase increase --

I _ 1 I I I - ,_ _ o100 - 11°

I I200 Ii I •

I300 Top of the confining unitabove the

Rio Grande water-bearing zone

4O0

500 Top of the confiningunitbelow the J-- J-_, Rio Grande water-bearingzone [

o_ 600 I

Base of theconfiningunitbelow theI

O_ 700 RioGrande water-bearingzone

_'800a

900 Baseof the compositeconfiningunit

1000

1100

1200

1300

Figure 4. Sample of sparker section (line D) with check-shot velocity histogram and borehole logs forwell ACOW no. 1.Exact correlations between thecheck-shot velocity histogramand borehole logs show apparent shifts which are caused by the greater comparative sampling interval and interval velocity calculations for the velocity data.

5

GAMMA GAMMA-GAMMA

HYDROSTRATIGRAPHIC ACOW no. 2 CHECK-SHOT RADIATION DENSITY RESISTANCE

INTERPRETATION v VELOCITY increase increase ohms

SEA LEVEL -- (1000 ft/sec) _-- _ _ NEUTRON --RADIATION _=, 0I I I I I I I -_'_

5 10 ..-_'-- ........ increase

100 ,_, _"_

300

400Top of the confining unit above the RioGrande water-bearing zone -_

!,00 L ]_ _oo I ._-

_ Top of the confining unit below the Rio __ "_ l

Grande water-bearing zone

°• 700

Base of the confining unit be,ow the Rio _ ._ _

_- 800 Grande water-bearing zone

900 ] --_,:_.._. . __.__;1000 _"-_,t-.Base of the composite confining unit -'" "_" -_ _ ._"---

1100

1200.

1300

Figure 5. Sample of sparker s_fion (line D) with check-shot velocity histo_am and borehole logs for well ACOW no. 2. Exact coffelations between the check-shot veloci_histogram and borehole logs show apparent shif_ which _e caused by the g_ater comp_afive rumpling inte_ and inte_ velocity c_culations _r the velocity dam.

6

Quaternary (table 1).Figure 3 showsfourprominent reflec- Geophysical methods have been used to map areas oftors corresponding to boundaries of some of the hydro- the Coastal Plain based on changes in the physical charac-geologic units in the Kirkwood Formation. Borehole tefistics of hydrogeologic units (Sandberg and others,gamma-gamma (density) logs from offshore and onshore Geophysical investigation of the Potomac-Raritan-Magothywells suggest that most of the CoastalPlain sediments have aquifer system in the northern Coastal Plain of New Jersey;similar densities. As a result, most of the reflectors are due Mullikin and others, Hydrostratigraphy of the Kirkwoodtovelocity contrasts (whichcorrelate directly with the chan- Formation, manuscripts on f'deat the NJ. Geological Sur-gesin calculated interval velocities), indicativeoflithologic vey).change or physical water-bearing characteristics.

Table 1. Geologic and hydrogeologic units investigated in the Atlantic City marine seismic survey (table modified from NewJersey Geological Survey, 1990).

AQUIFER NAME ORSYSTEM SERIES GEOLOG IC UNIT OR UNITS LITHOLOGY HYDROGEOLOGIC

CHARACTERISTICS

Holo¢:en¢ alluvial, coastal,marshandeolian sand,gravel, slit, mud, andpeatdeposits

_' Pleistocene Wiso_nsinanalluvium, CapeMayFormation,coUuvitwn sand,gravel slit. clay Under water*tableconditionsatmost

loeatinns

PmasaukcnFo_nationsand,clayey silt

Bdligeton Formation.

Beacon Hill Gravel gravel, llght-colored,qua_z. sandy

i_. Cohansey Sand sand, medium ta coa_e, li_t-colored, quartz,

Miocene pebbly;local clay beds Kirkweod-Cohax_ey aquifersystemconfining unit

KirkwooliFormation sand, vet7 f'meto mcdith'n,gray and tin, quartz, RioGrandewater-bearingzonemlcaeeous; dark-coloreddiatomaceous clay.

confining malt

Atlantic City 800-footsand

_ compmite eont-mdig unit(includes PineyMiocene- ACGS BetaUnli throughNavesink clayeyslit. sand,glauconitesand Point aquifer)• Upper Formation_ Cretaceoos

Table 2. Records of wells used in the Atlantic City marine seismic survey (modified from Mullikin, 1990).

Well Permit Latitude/ Owner or Elevation Depth Type ofnumber number longitude name (ft)l drilled (fl)2 log3 Remarks

N391955 ACOW no. l marine

1 36-5615 W742507 U.S. Geol. Stu_ey -32 931 L,G observation well - inshore.

N391726 ACOW no. 2 marine2 36-5972 W742221 U.S. Geol. Survey -43 1,025 L,G oh_e_'ation well - offshore.

N392108 Youngs3 56-70 W747f_I0 OceanPier 20 2,306 L

N392124 Bally's Pa_ Place, 7 884 L,O4 36-108,1 W742604 Inc.

N392133 Resorts5 36-964 8 887 LW742522 lntemalional

tElevatlon: feet above or below sea level as estiamind from U.S.G.S. 7.5-minute quadrangle map (contour interval l0 feet)2Depth drilled: feet below land surface or, for wells 1 and 2, below sea floor)I'y pe of log: L - Lithologlc, G - Borehole geophysical

_ EXPLANATIONSparker profile"_" _" V _ "_9^ _ 92// ................. (pointsshowIoran fixes)

/ +_°o_,,,.,,,x./ Elevationof reflectingintedace/% (feet belowsea level)

ContourInterval10 feet

Datum:sea levelATLANTIC CITY Scale 1:50,000

..'_._ Miles

.:[:_::. o 1_ 1I I I

WELL NO. 5 . •....

WELL NO. 4 o j _,.. •....

_ 0 ,_ '0"_, _'i."

..,.,."

WELL NO. 3 .C.,

..Y ,...'"

• ..:::i,i ............. _''._: ..

.. _ .._.._,_ _...z ............

..."/" ..,.., ....." '.....

.,.......... %.....-. _ ......,..... ) /

PROFILE /'-_/_'_'P'_. o'-- ',.. .5._0

.............. //-.,... ',.,, _...\

Figure 6. Location of tracklines and elevation of the top of the confining unitabove theRio Grande water-bearingzone in theKirkwood Formation, based on interpretation of sparker profiles.

y_ EXPLANATION

" Sparker profile

(feetbelowsea level)

ContourInterval 10 feet

ATLANTICCITY _ Datum:sea levelScale 1:50,000

-"" Miles

!"_ "'" 0 1,'2 1/ I IWELL NO 5 / ..... • ....

WELL NO. 4 • . ..... _. .......

WELLNO._ -....., _ ....

...._:::...{.-.....

.........................>.'" ." o i..... ...................

." IY" i ...."

...--" '; . \"..%

•. .t

/•.. /.

"..%

Jr e ACO_/NO 2 -r_..... " .1 _'_

....y .......... ,_ ..,..f /'_.".REPRESENTATIVEPROFILE _.-

Figure 7. Location of tracklines and elevation of the top of the confining unit below the Rio Grande water-bearing zone in the

Kirkwood Formation, based on interpretation of sparker profiles.

9

_:_0_ EXPLANATION...... (pointsshowIoranfixes)

S Elevationof reflectinginterface

_,, ;_(_'2- (feet belowsea level)ContourIntervaJ10 feat

ATLANTICCITY "_ Datum:sea levelScale 1:50,000

I IWELL NC 5 ......."" ""

WELL NO. 4 • J -.'0 -,'" j

,,,,'

• ,,," ,,, ,"

,.., , ;., ,,.,,,,,'''"" [

r

!

,,;

,,,, ; ",,,,, ,,,"

;,- ,,, \,

,,,," ,j

,,' ,,, ,,

£840 --

........................ l_-,.,.../,oowNo._,...." _E._,vE _o_,,__, _,,

Figure 8. Location of _acklines and elevation of the base of the confinuTg unit below the Rio Gr_xlde water-bearing zone in theKirkwood Formation. based on interpretationof sparker profiles.

I0

EXPLANATION,__ __.__. _ ............ Sparkorpro_

f Elevation of reflectinginterface

(feet belowsea level)

ContourInterval 10 feet

ATLANTIC CITY Datum:sea level

.................. Scale 1:50,000

i IMiles

i S o ,o/ .... I rWELL NO. 5 /

++.+...'"

...+:

.... ..."

f- • WELL NO. 3/,., .,..

.....+., ,. +.." /......+!• ,+,"_ "

• ...,"..." .,...

.,' ..+.+

"._-::Z.%

..+..."+

..."

"_,.. . ...,'".+.' ....' i}

,.'" .. +.... ' .++.+" . .'"+ _.\. .'.-- ...i.:",:i,+

+_,'" • ." .,:. "_+-+"..,+.+'+ .,+..

..'i:<:..+ ..... *""ACOW NO, 1 •''_'' .' " /.

,, .., i.,." _* . .'.. .+"

• .+." ... _ _)_ :+

+._" ....-+++ .*x ..-++:`+ /...+.++.+., _.-\

• f .+.+"+" +..+.+--.."'" _ .,. "" ""

Oo ,! ..... .... .- / .i>( _+ ' '+ °,. ...- ,. +-" CO /

• +.." '". /.++..../..... ', :' ....... 2 ". +¢,. _ . ,.:

+.f"• +.+

+...+..': _.....""+"..+, ,.,.' •

., "++ ,_

.., "i

•,. +..... .. aa_

+ ".= -F

......... _ _"",,... ACOW NO. 2..+" _. ,+,,

REPRESENTATIVEPROFILE}_:::. "_ / .....\

Figure 9. Location of tracklines and elevation of the base of the composite confining unit, based on interpretation of sparkerprofiles.

J

11

The two monitoring wells, ACOW no. 1 (1 mile off- Each of the four reflecting interfaces is stratigraphicallyshore) and ACOW no. 2 (5 miles offshore), were drilled in continuous throughout the survey urea. Several zones alongJuly 1985 off the coast of Atlantic City (table 2), and are the reflection profiles, however, show discontinuous datalocated within the geophysical survey grid (figs. 6-9). The indicating ureas of attenuamd seismic energy. These at-N. J. District office of the U. S. Geological Survey, Water tenuation zones may be attributed to neur-surface, locallyResources Division, collected several different geophysical thick, organic-rich sediments. Elliott and Wiley (1975) in-borehole measurements in these offshore wells, including terpreted attenuation zones (bright spots) as zones of pus-check-shot velocity data. The check-shot measurements siblegas-saturatedsedimentsoforganicorotherorigin.Thewere reduced and interval velocity histograms were subbottom erosional features shown on the shallow profilesprojected to the nearest seismic profile, line D (figs. 4 and are inferred to he buried channels which may contain or-5).For this representative profile (figs.3-5), the timevalues ganic-rich strata.from the seismic prof'de have been converted to an ap-proximate depth scale based on the average velocity to the Boomer data

deepest (fourth)reflector. The boomer data indicated two prominent geologicDepth to the fourth reflecting interface was calculated features: 1) sand ridges and 2) subbottom, lens-shaped

using data from onshore wells and from inland reflection features (fig. 10) interpreted to he erosional surfaces ofvelocity surveys. Well no. 3 was the only well topenetrate shallow channels (fig. 11).a tightly-packed glauconitic sand below the fourth reflect-

ing interface at the top of basal clay unit. The two offshore Sand ridgeswells did not extend to the depth of the fourth reflector, and

The ridges are sea-floor features similar to others alongso an exact offshore interval velocity could not he deter- the Atlantic inner continental shelf. A continuous, north-mined, east-trending sand ridge extends across the urea of the

Four hydrogeologic interfaces are identified bythe four survey grid, somewhat parallel to the present-day shorelinereflectors. As shown by sparkerprofile D (fig. 3), these are, (fig. 11).A smaller,bifurcating ridge lies in the southeasternfrom the top down: 1) the top of the confining unit above comer of the area. The deposition of offshore sand ridgestheRioGrandewater-heuringzoneoftheKirkwoodForma- has been studied for offshore Delaware (Moody, 1964;tion, 2) the top of the confining unit below the Rio Grande Sheridan and others, 1974); for offshore New Jersey (Stub-water-beuring zone of the Kirkwood Formation, 3) the base blefield and others, 1983; Swift and others, 1984;Charles-of the confining unit below the Rio Grande water-bearing worth, 1968; Miller and Dill, 1973; Stahl and others, 1974)zone of the Kirkwood Formation, and 4) the base of the and regionally along the northeastern U. S. coast (Schlee,composite confining unit (table 1). 1973;Swift and others, 1973).

Calculated depths from average velocities were used toconstruct contour maps of the four reflecting interfaces Subbottom erosional surface(figs. 6-9).The maps show that the Kirkwood units continue The transducer profiles show buried channels (fig. 11).the southeastward regional dipof about 30 feetper mile, and Vibracores fromcomparable channels, 15miles north of thegenerally thicken seaward. The correlation of these off- study area, consist of organic-matter-rich sand and clayshore hydrogeologic units with the land-based stratigraphy overlying gravelly sand (Miller and Dill, 1973). Similaris incorporated into "Hydrostratigraphy of the Kirkwood channels were also studied in Delaware Bay (Knebel andFormation" (Mullikin and others, manuscript on file at the Circe, 1988) and offshore Delaware (Sheridan and others,N. J. Geological Survey). 1974).

CONCLUSIONS

A grid of seismic data was collected off the coast of thicken and maintain the regional dip. The shallow boomerAtlantic City, N. J. Sparker records prof'ding to depths of records show lens-shaped features, interpreted to be buried1,800 feet confirmed that major lithologic units within the channels, and two sand ridges.Kirkwood Formation are continuous offshore and that they

12

OCEANSURFACE

50 milliseconds

Figure 10. Representative shallow-penetration (boomer energy source) section approximately on-strike showing analog profile data with geophysical interpretation of buried channelfeatures. Horizontal scale 1:25000.

13

........... Boomerprofile

/,_ "9'_^'_ _q,_ ..... (pointsshowIoranfixes)BuriedChanne/

ContourInterval10 feet

ATLANTICcITY _,_ Datum:sea levelScale 1:50,000

Miles- . O 1,'2

[ IWELL NO. 5

WELL NO. 4 o / . ................

%..° WELL NO. 3 • ....'' ...." '..%.

REPRESENTATIVE PROFILE _>_."" .. ,.,." . _ tA _-.

% ..."

•. ,.,

....

,, "i_,.:.................."..t .,...."

pt, ..:,:_ACOW NO. 1 ....- _..

.'_&.._,_' ,,, ...

.., ._, ,."'., .. ,_ ...... '. "...

y" ..,,- . .

.,." .. ..,.-" . ......-" , y.

,." ....,. "., "'%...%.

".. ...,"

.., ..e, t_.

'.x : . _g_{ • •

"', ....'" ..- ".

....: _'.

•""'""_. .. '. ..:

"%.... '.....

"t.

".... ....."

.,x

+ .."/ ""'.... + eACOW NO. 2...." .,

Figure 11. Boomersubbottom inteq)retationshowing locationof buried channel and axes of sand ridges,

14

REFERENCES

Charlesworth, L. J., 1968, Bay, inlet, and nearshore marine New Jersey Geological Survey, 1990, Generalizedsedimentation: Beach Haven-Little Egg Inlet region, stratigraphic table for New Jersey; New JerseyNew Jersey: Ann Arbor, Mich.,University of Michigan, Geological Survey Information CircuLar 1, 1 sheet.

unpublished Ph.D. dissertation, 260 p. Schlee, John, 1973, Atlantic continental shelf and slope of

Dix, C. H., 1955, Seismic velocities from surface measure- the United States; sediment texture of the northeast

merits: Geophysics, v, 20, no. 1, p. 68-86, part: U. S. Geological Survey Professional Paper 529-

Elliott, S. E., and Wiley, B. E, 1975, Compressional L, p. LI-L64.velocities of partially saturated unconsolidated sands Seaber, P. R., 1965. Variations in chemical character of(amplitude reflection coefficient): Geophysics, v. 40, water in the Englishtown Formation, New Jersey: U. S.no. 6, p. 949-954. Geological Survey Professional Paper 498-B, p. 1-35.

Hoffman, J. L., and Waldner, J. S., 1986, High resolution Sheridan, R. E., Dill, C. E., Jr., Kraft, J. C., 1974, Holoceneanalysis of shallow seismic data: HRASSD 2.0: N.J. sedimentary environment of the Atlantic inner shelf offGeological Survey Open-file Report 86-1, 74 p., Delaware: Geological Society of America Bulletin,1 illus., two 5.25-inch disks, v. 85, p. 1319-1328.

Hunter, J. A., Pullan, S. E., Bums, R. A., Gagne, R. M., and Stahl, L., Koczan, Jack, and Swift, D J. P., 1974, AnatomyGood, R. L., 1984, Short Note: Shallow seismic reflec- of a shorcface connected sand ridge on the New Jersey

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