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State of Delaware DE LAWARE GEOLOG ICA L SU RVEY Robert R. Jordan. State Geologist

BULLETIN NO. 20

STRATIGRAPHY OF THE POST-POTOMAC CRETACEOUS-TERTIARY ROCKS OF CENTRAL DELAWARE By Richard N. Benson and Nenad Spoljaric

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University of Delaware Newark. Delaware 1996

State of Delaware DELAWARE GEOLOGICAL SURVEY Robert R. Jordan, State Geologist

BULLETIN NO. 20

STRATIGRAPHY OF THE POST-POTOMAC CRETACEOUS-TERTIARY ROCKS OF CENTRAL DELAWARE

BIOSTRATIGRAPHY AND CHRONOSTRATIGRAPHY OF TEST WELL Je32-04 By Richard N. Benson

NON-CLAY MINERALOGY OF THE MATRIX (SILT-CLAY) OF Je32-04 CORES By Nenad Spoljaric

SUBSURFACE STRATIGRAPHIC CORRELATION OF SELECTED BOREHOLE GEOPHYSICAL LOGS FROM CENTRAL DELAWARE AND NEW JERSEY \,

,I

By Richard N. Benson

University of Delaware Newark, Delaware 1996

CONTENTS Page

Page

ABSTRACT.

Aragonite

13

INTRODUCTION

3

Dolomite ,

13

~

Pyrite and Marcasite Sidcrnc '

11

Acknowletlgmenh BIOSTRATIGRAPHY AND CHRONOSTRATIGRAPHY OF n:.ST WELL

.k.1~_(~1

1::1) Richard N. Henson

INTRODUCTION

5 5

Upper Cenomanian-Lower Turonian

5 5 5

Santonian.

5

Campanian .

5 6 6 6 6 6

CHRONOSTRATIGRAPHY AND B10STRATIGRAPHY Upper Creraceon,

Maastrirhtian Paleocene Danian. Thanetian..

Eocene

L\

Zeolites Hematite

13

Goethite.

13

Vivianite Quartz.

13

Feldspar.

11

Calcite

1.1

1.1

1.1

UNUSUAL MINFRALS AND M1NERAL ASSOCIATIONS __

14

Upper Vincentown-Lowermost Deal.

14

Lower HOlllust,lwn IJpper Deal.

14

SUBSURFACE STRATIGRAPHIC CORRELATION OF SELECTED BOREHOl.r GEOPHYSICAL LOCS t"ROM CENTRAL DELAWARE AND NEW JERSEY

Yprcsian .

6

Lutctian '

,

lNTRODUCTION

s

IS

STRATIGRAPHIC CROSS SECTIONS

IS

Miocene. SEDlMENT ACCUMULATION RATES.

7

INTRODUCTION METHODS RESliLTS

IS

Methods.

NON-CLAY M1NERALOGY OF THE MATRIX (SlLT-CLA "'1') OF Je32-04 CORES By Nenad Spoljaric .

By Richanj N. Benson,

IS

Results of Geophysical L\Jg Correlations. II

II

IS

Comparieons wilh Other Stratigraphies

........... 20 ....... 20 .22 .. 22 ........ 22

LITHOSTRATIGRAPHY OF J"",:'_OJ

II

Poromtc Formation .

II

Mngothy Forrnarion

Potomac FOfnMtion

II

Merchantville Formation

Magothy Formation

II

Englishtown Formation .

.. .... 22

Merchantville Formation

II

Marshalltown Formation

Englishtown Formation .

II

Mount Laurel Formation.

....... 22 13

Marshalltown Formation

II

Navesink Formation.

Mount Laurel Formation

II

Hornerstown Formation

12 12 12

Vincentown Formation

Navesink Formation . Hornerstown Formation

Vincentown Formation f)t"al Formation . Pint"y Point Formation Cal vat Formation. SIGNIFICANCE or MiNERALS AND MINERAL ASSOCIATIONS, Jarosite and Alunite Tall-

12 12 12 12 12 12

, .. 23

.. 23 .,23

Deal Formation. Piney Point Formation ,

CalwI1 Formation

................ 24 '" __

24

CONCLUSIONS

...... 25

REFEREJ\iCES CITED

...... 26

l FIGURES Page

4

Figure I. Locations of Coastal Plain boreholes

In Pocket

2. Chronostratigraphy, biostratigraphy, and lithostratigraphy of Je32-ll4 Age vs. depth diagram of Jd2-04 ,

,

, Results of x-ray anatyxcs of non-clay minerals of the matrix (silt-clay) of 1e32-04

<:OTt'

9 In Pocket

samples

5 Stratigraphic ems, section showing bort:ho!e geophysical log correlation between Clayton, New Jersey. and Je ,12-04 ,

In Pocket

6. Stratigraphic cross section showing borehole geophysical log correlation between GlD3-04 and Je32-04

In Pocket

(;ms~ section showing borehole geophysicallog correlation between the Chesapeake and Delaware Canal area and Jd2-04 _._ Lithostratigraphy of Od33 -04 compared with other stratigraphies Lithostratigraphy of .ld2-04 compared with other seratigraphies

7. Stratigraphic

, v

In Pocket

_

.... 20 , .. 21

TABLES

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Page Table 1. Scdim..nt accumulation rates, Je32-04 _._ 2. Borehole depths of lithostratigraphic boundaries, Je32-04

.,

21

l

_ STRATIGRAPHY OF THE POST-POTOMAC CRETACEOUS-TERTIARY ROCKS OF CENTRAL DELAWARE Richard N. Benson and Ncnad Spoljaric ABSTRACT This Bulletin presents the subsurface stratigraphy of the post-Potomac Cretaceous and Tertiary rocks of the Atlantic Coastal Plain of central Delaware, between (he Chesapeake and Delaware (C & D) Canal and Dover. Geophysical log correlations supported by biostratigraphic and lithologic data from boreholes in Delaware and nearby New Jersey provide the n;j\j\ for the report. The stratigraphic framework presented here is important for identifying subsurface stratigraphic unite penetrated by the numerous boreholes m this parr of Delaware, particularly those rock units that serve as aquifers, because such knowledge llllow) for benet prediction at ground-water movement and availability. Also, accurate stratigraphy is a prereqursue h ir interpreting the gC()[~lgi~· hixtorv of the rocks and for the construction of maps that depict the structure and thickness Dr each urut. Three ~lratigr;lphll· Cfl)~~ ~cclillns document the stratigraphy. Downdip control is provided by cored test well Je32-04 (one split-spoon core every 10 ft) at the Dover Air Force Base. Reported from the well are new and revised biostratigraphic data QtJ calcareous nannofosvils, planktic Ioraminitcra, radiolarians, diatoms, palynomorphs, and dinoflagellates and the results of x-ray identifications of the non-clay minerals comprising the matrix (silt-clay size fraction) of each core sample. Updip control is provided by borehole GJ33-04 correlated to the continuously cored U. S. Geological Survey (USGS) core hole near Clayton. New Jersey, with its published biostratigraphic (calcareous nannofossil zones) and lithostratigraphic data. 111e x-ray mineralogical study of the non-clay-mineral component of the matrix of the Je32-04 core samples supplements all earlier study of The clay mineral component. Mineral associations identified provide additional information on the lithostratigraphic units of Je32-04. Zeolites in the Paleocene-Eocene section indicate possible volcanic sources. The association of the minerals jarosite, alunite, hematite, kaolinite, and talc suggests chemical activity by hydrothermal solutions. An uppermost Paleocene carbonate dissolution interval correlates with one in the Clayton, New Jersey, core hole where an increase in kaolinite is noted through the Paleocene-Eocene boundary interval. The intense weathering to produce the kaolinite, the evidence for volcanism, and, possibly, the dissolution interval may be related 10 a major global event during the time interval represented, a time of significant tectonic plate reorganization. This Bulletin revises the previously published lithostratigraphy, biostratigraphy. and chronostratigraphy of the Cretaceous-Tertiary section of Jc32-04. Lithostratigraphic units and their ages are the Potomac Formation (late Cenomanianearly Turonian): Magothy Formation (Santonian); Merchantville Formution (Santonian-Cnrnpaniau}: Englishtown. Marshalltown, and Mount Laurel formations (Campanian); Navesink Pormatinn (Muaxtrichriun): Homerstown and Vincentown formations (Paleocene); Deal Formation (late Paleocene-middle Eocene); Piney Point Formation (middle Eocene); and the Calvert Formation, including a basal glauconitic sand (early 10 early middle Miocene). The Magothy Formation undergoes a ten-fold decrease in thickness between JeJ2-04 and the C&D Canal as shown by on lap of the formation on the unconformity between it and the Potomac Formation and by crovion of the upper beds or complete removal of the formation at and near the Canal. The Englishtown Formation shows a characteristic upward-coarsening gcophvsical log signature at and near the Canal and in downdip areas. This feature is not as readily distinguishable on borehole logs from between those two areas and from the Clayton core hole because the formation becomes silty. The log signaturc-, of all other formations from the Merchantville through Hornerstown correlate well, including those of the Clayton, New Jersey, core hole. Major thickness and facies changes, both along strike and downdip, occur within the Paleogene section that unconformably overlies the Hornerstown Formation. The updip Vincentown-Manasquan-Shark River section correlated from the Clayton core hole to GdJJ-04 is replaced downdip by the finer-grained and more nearly homogeneous Deal Formation. These chimge~ occur across a growth fault postulated to account for an abrupt, nearly three-fold increase in thickness of the post-Hornerstown Paleogene section. The Deal Formation grades both vertically and laterally downdip into the overlying middle Eocene glauconitic sands or the Piney Point Formation. The Piney Point thins updip by facies change to the Deal lithology and by erosional truncation indicated by the unconformity between the middle Eocene and lower Miocene sections. The Calvert Formation downdip has a basal glauconiuc sanJ; the formation including the Cheswold and Frederica sands, which are important aquifers ill many areas, IS truncated updip by the erosional unconformity at the base of Quaternary deposits.

2

INTRODUCTION ously cored U. S. Geological Survey (USGS) borehole near Clayton. New Jersey. The present study originated with the x-ray rnineralogic,1 study hy Spoljanc of the non-clay (non-platy minerals) component of the matrix (silt-clay J of Jc32-04 sediment cores to supplement his study of the clay mineral component (Spoljaric, 1988,1. Revisions of the biostratigraphy and chronostratigraphy of Jc32-04 are based on new biostratigr"phic data (In palynomorpas , dinoflug.dl
In this BuHetifJ we pre-enr a stratigraphic framework for the post-Potomac Cretaceous-Tertiary rocks of the Atlanlic" Coa,!al Plain of central Delaware, between the Chesapeake and Delaware (C&O) Canal and Dover (Fig. I). A rigorously established stratigraphy of these rocks is important for identifying .sllh,urbn' straligraphi~ unit ... pen enured by the numerous boreholes in this area, particularly those lock unib thaI ...crve a-, aquifers because such knowledge allow, for better prediction of ground-water movement and availability. win regard to these important rock units, our study shows how some unite become less efficient to non-existent as aquifers because of lateral facies changes to tiner-grained units, oy having been cut off by f3Ult:-., or by h:tving been thinned or removed by erosion that is represcnteo by r~gil\nal ecccntonntrtcs Also, accurate stratigraphy is 11 prerequisite for interpreting the geologic history of the rocks and lor til: construction of maps rnut depict the structure and thickness of each unit. The main source of our information on the subsurface Cretaceous-Tertiary rocks of the Atlantic Coastal Plain of Delaware is borehole geophysical logs, primarily gammaroy ll'g~. Samples of sedimentary rucks from most boreholes are mainly drill cuttings recovered from drilling mud pumped to the surface (ditch samples) Few boreholes in Delaware were systematicully cored and none was conunuously cored: therefore, detailed stratigraphic analysis and subsequent correlation 01 stratiJ;r
Acknowledgments We are grateful to those who provided valuable biostratigraphic data for this report: Johan J. Groot of the Delaware Geological Survey on palynomorphs; Laurent de Verteuil of the University of Toronto on dinoflagellates: and Jean M. Self-Trail. Laurel M. BybelL and Thomas G. Gibson of the U. S. Geological Survey on calcareous nannofo.s~ils and foraminifera. Fruillu{ discussions with Thomas Gibson enhanced the quality of this report. Roland E. Bru.nds of the Delaware Geological Survev assisted in mineral identifications. We are grateful to Stefanie J. Baxter who produced computer-generated Figures 2 and 4 and tutored one of us (Benson) on the production ot the remaining figures in this Bulletin. The manuscript wa- critically reviewed by Thomas G. Gibson. Robert R. Jordan, Kelvin W. Ramsey, and Peter J. Sug acmuu who offered hc lpfu l suggestions for its improvement.

..

3

40°

Pennsylvania

•

C& Dcanal

\

Oayton

Core""" Eb2~22

•

~

0708

Ec:41_09,08

'Fb15-08

10

.~22

• Fb4>
•Fc51-26

Ql3~~

NevvJersey

• ",,4-04

H:42-12 •

• 1-Jo44.08

.ICZS.12 .kl31-26

•

Id55-01

•

Je32-04

-Kb32-D1

Delaware Bay

39°

Oh25-Q2 •

/r I

Delaware

N Maryland 76°

75°

Figure I. Locations of Coastal Plain boreholes mentioned in text and shown in Figures 5-7.

4

J

~-------------BIOSTRATIGRAPHY AND CHRONOSTRATIGRAPHY OF TEST WELL Je32-04 Richard N. Benson

Wolfe and Pa ki se r , 1971). The high percentage of angtosperm pollen and the low percentage of triporate pollen grains of the Normapolles group suggest a late Cenomanian to early Turonian age for the Potomac section. The as~t'mhlage is similar to that of Zone IV of Doyle and Robbins (1977); however. the paucity of fossil pollen. particularty t1ll)se of shorr stratigraphic range, indicates caution in agc ilssiglllllent.

INTRODUCTION New biostratigraphic data aml interpretations derived from more recent research and publications require revisions in the biostratigraphy and chronosunugmphy of k5~­ 04 by Benson et al. (1985). Newly identified or revised calcarcous nannofossil. foraminiferal. and radiolanuu glob:l.l hiostratigraphic zones and regiouul Miocene diatom and dinoflagellate zones are shown in Figure 2. The lithostrntigraphic units shown in Figure 2 were identified on the basis or borehole geophysical log com-lations a, discusved in a later chapter of this Bulletin. The global biozones have been vummarivcd ami entreJated with geomagnetic polarity chrons hy Berggren ct ul. (1YIl5a, IYIl5b) for the Cenozoic and Bolli Cl al. (19RS) for the Mesozoic and Cenozoic. Bt'rggn:n ct ill. (1995) redefined some of the Cenozoic plnnknc forumiuifcral and calcareous nannofossil biozones and revised the geochronology and chronostratigraphy of the Cenozoic as determined from the geomagnetic polarity time scale of Cande and Kent (\992. 1995 j, Age esnmates of stratigraphic boundaries identified in Je3::!-04. rounded to the nearest million years (Ma) he fore present. are shown in Figure 2. For the Cenozoic these were determined from Berggren et al. fl9R.'ia.h; 1<:J<:J:'jl and Cande and Kent (1992,1995). The time scalL' of Gradxrcin et ul. (1994) was used for estimating the :.tgt"s of the- Cretaceous stratigraphic boundaries. Palynologtcul age determinations of the nonmarine Potomac anJ Mugothy formations were made by Johan J. Groot of the Dclawarc Geological Survey. Upper Cretace..-us calcareous nannofossil zones of Perch-Nielsen (19l:l51 were identified by Jean Self-Trail of the U. S. Geological Survey (written commun., 1995, 1996). Tertiary calcareous nannofossil zones, primarily of Martini (1971) and secondarily ot' Bukry (1973, 1978), arc from Bybcll ct
Santonian

Upper Cenomanian-Lower Turonian

Juhun J. Grool (written commun., 1986) examined palynomorphs from Magorhy Formation cores 20704 (1357-59 ru, 20700 rn17-19 ft), 20699 (1307-09 ft), and 20098 (1297-99 ftj. His data indicate a Santonian age for the sampled interval. The pollen assemblage resembles that of the Amboy Stoneware Clay Member of the Magothy Formation in New Jersey. also thought to be of Santonian age (Wolfe and Pakiser, 197]). A minimum of 8 million years is estimated for the hiatus representing the unconformity between the Potomac and Magothy formations in Je32-04. The calcareous nannofossil data indicate Zone CC I5 for core 20694 (1257-59 ft ) from the base of the Merchantville Formation and Zone CCI7 for cores 2(61):(1259-47 ft) through 20691 (1227-29 ft) from the same formation. Perch-Nielsen (1985) indicates that these lanes are of Santonian age. No zonal determination was made for core 20690, but the lowermost Campanian wile CC 1~:.I (Perch-Nielsen, 19R5) is identified for core 20689 (1::'07-09 ft) from the middle of the Merchantville Formation. The calcareous nannofossil data, therefore, indicate that the Santonian/Campanian boundary lies between CPITS ::'069I and 20fi89 within the Merchantville Formation . Benson et al. (1985) placed the base of the Campanian below core 20694 (1257-59 ft) where one poorly preserved planktic foraminifer was identified as Glohntruncana vcntricosa. Because of the uncertain identification of this single specimen. the base of the Campanian as determined by foraminiferal data is moved upward from its position as determined by Benson et al. (1985) to coincide with the boundary identified by the calcareous nannofossils. In .suppan of this, the boundary occurs at the base of the first occurrence of Gtobotruncuna tinneiano in CMe 20690 (1217-19 ft) (Benson et aI., 1985, PI. 2). Caron (1985) places the first occurrence of this species at or just slightly below the Santonian/Campanian boundary.

Johan J. Groot (written cornmun .. 19Rti) did palynological studies of the nonmarine Cretaceous section (Potomac and Magothy formations) penetrated bv k:>2-04. Quoting freely from his report, core samples 2071 I 11420-22 ft) and 20710 (1410-12 ft) from the Potomac Formation YIelded n and 54 identifiable palynomorphs. respectively. Most of lhc angiosperm pollen are tricolpate and rncolpornte ones that arc common in the Cenomanian and are reported from the Woodbridge Clay and South Amboy Fire Clay members of the Raritan formation of New Jersey (Groot Itt al.. IYO I;

Calcareous nannofossil data provide a higher degree of biostrurigraphic resolution of the Campanian section than do the planktic foraminifera, Perch-Nielsen (1985) assigns zcmcx CC IR through 2:la to the Campanian. Jean M. SelfTrail (written commun.. 1995, 1996) identified Zone CC 18a III core 206R9 (1207-09 ft) Oil the presence of Aspidolithus purcus and Zonc eCl9 in cmcs 206SR (1197-99 ft) through ::!OhRO (1117-18.:; t't) (upper Mcrchuntvil!c and most of

CHRONOSTRATIGRAPHY AND BIOSTRATIGRAPHY Upper Cretaceous

Campanian

5

l

_ CC25h is identified in cores 2(166~ (997-99 ft) and 20667 (9,:>(7-8':1 fl). Mv\/ of lhe M'lUsuich!ian imerval prC\ious!y identified on the basi~ of planktic foraminiferal zones by Benson et a.. (I'.lS)) is now placed in the Campuruau :\s discussed above. The cnlcarcuus nannorossr! Lones missing between ee2::?\: and CC25b indicate .\ hiarns {It" uhout +5 miljion ye.u-v between !Ile Camp;l1li:m :wd MU:t.~'/fI,-,h!i;ill sections (Fig.2).

Cnglisnt,'wn 10rmalinn"; on the absence of Ceratotithoides l/cuft'us and Martllllsleri!el'lillv/!w. She identified Zone

ceo ill coree 2067H (1097 ·)09l.U it) ami 20677 (1087-89

ft) from the Marshalltown Formation Oil the presence of C aculeus and absence 01' Quadrum ,lis"rnghii. Cores 20h74 l 1057-59 ft) Ihrough 206(1) (loo7.{)9 ft) rrom the Mount Laurel Formation are assigned to Zone CC22L The "fC cstjrnatr- of 72 Ma !Fig. 2) for the top of the Campanian section in JeJ2-04 ttop of MOLInt Laure: Formation) agrees do,dy with the Sr-i,o{ope age estimate by Sugarman et al. r ! (95) of 71 A Ma for one belemnite from (h~ outcrop uf the Mount Laurel Formation at the Chesapeake and Delaware Canal in Delaware. Also, Kennedy and Cobban (19941 dale the ammomte los~i1s from tlit: Mount Laurel at the Cnna I as late' Campanian. Benson e t al. (198.~) idO'ntified the combined G/obolruncana elevata - Globotrunconita catcarata ('!l planktic foraminiferal lone" as comprising the Campanian imerva! of Jc32 IH. The r;Ioho/runclInitL/ ("a!cl/rata Zone W,1, not identified in lc32-04, bu( it was identified in ageequivalent s:r;Jl<1 .Marshnjhown Furm;ltioO'i :.1
Paleocene

Danian The occurrence rogt-thcr of G/(}[xJnmusa daubjergefl.\is and IH"ro,~,wdla inconstuns ill cores 2()66o-206fH. (979-957 tt) ;Jl(lng with SIlMmli!1t1 p.;·,'udobull"i,Jef, S niloculilloide.\', and Planorotalites mmp/"essu identifies Danian planktic foraminiferal Zone Plc (T'oumarkinc and Lurerbacher. [n5, Fig~. 5-fi). Byhell et al. (1995) assrgn cores 20665 and 20
Thanetian Core' 2(166:.1 {/1:\Jugll 20652 (9V) !i-~7 ftl cornprise the Thaneuan (upper Paleocene) section of k32-04 us defined by calcareous nannotoss't zones NP6. S, and 9 (Bybell et al. 1(95) and. in part. by planktic for arniniteral Zone P4 recognized in cores 20663-20659 :94l)-'.IU/ It) (Benson et cl., 19~th The hiatus between the Danian and Thanctian intervals i~ approximatuly 1-4 million years. Foraminifera are absent or ru-ariy so from cores 2065H through '2.0652 (1<199"847 1'1), The rew specimens observed show evidence or dissolution or arc represented hy internal CIS!S. I n:l;of',rlize Ihi., .'ection of the borehole ilS J. di.~s(llu­ tion interval. first sugpested by Ben,ull et al. (191:(Sj and sllf1rmrted by the unusually low calcite content of the matrix as indicated by the x-ray data reported by Spolja-ic ill nu-, Buttedn. Thj, approximately 62-ft intava( in 1e32-04 correImcs \-I.ith all approximately 23-fI dissolution interval {If Ihe same agt: (ci:llcarcous nannofossil Zone NP9) observed in the Claytnll, New Jersey, cme hole by Gihson et ~\l. (\993). In
Other th:.m ICll
the G1/1H.H'rina g(lll~seri Zone: to reflect the change in generic assignment of the nomtna.e species rCaron, l 9R5), 110 other changes were made ,0 the Cretaceous planktic foraminiferal zones of Benson et at. (1985) tor Jd2-l!4. According 10 Pcners (1977), Ihis tsme :.lIld the underlying Rug otruncana subcircurnnndifer Zone comprise the Maasuichrian section, and this was accepted for Je32-04 hy Benson ct al. 0<.)85). By this definilion, the entirc Mount Laurd Funn3til'n. as juc!Hitied in thi~ Bu;letin. WQuld he of \1aa.'>1richlian age. Tbis i,\ in ngrcemelll with HouJik ct al. (1983) for the age of ;he t'ortnalillj) at and ncar the rh,~sapeake and Delaware Canal, who determined tbat the Campani<.\rr/Maastrichtian boundary, as dc1ined hy the la~( uecurrel1ee of GI"h,,(runulIlila ul/car(1la, is at thc \:o{jtact between the 1\larshalllown and Mount Laurel formalipllS. Tile l'akarcOlis nunnof()s~il Znni" Cr22c identified in Mount Laurel cores 20674 thi'ough 20669 (1059-1007 fl), hllwever, indicates a CaJilpalnall age ror the formation. A<.:corJing to Burnett et aJ. (1992), {hi~ zone, as ddined by Pcrcb-Nidsen (19gS), occurs helow th~, Jk;l ilppcaranec ("If RP/tmne!lu!anceo!ora and, therefore, is Campanian by definition a\:conling to this belemnite marker. The last occurrence of Glohot/"II/Julf'Iilll cu{,-urv.w is within Zone CC22c (Burlll."ttd ~ll., 199::'). GmJ.,tein et aI, (1994) JCc'-'pt (he fir.-t oCC:JTrelll·t: l~f 8. lwu'co/a/(! us do,e t{~ the ba~1' of the Maaslri\:htian, and this may become the standard Jdinition for ihe LampanianfMaastlidlLian boundary.

Eocene Yprc.\iall

The PaleoceneJFoccne boundary has been placed at [h~ houndary between cakarel'u.s nalln0fos.siJ ;>Olles NPlJ ;wu NPIO (Betg~len ~t a1.. ll)g5:1~ Bolli d ilL 198:'\1. Hergl!ren et al. (1995), however, now indicate that there are difkrent opinillns on the placemem or the Pakoci.:nelEo-:cne bnlllltl:lry; they pl.tce t1:e NP9JNPIO bound.:ry· within ell", illtcrv'll of uncertainly hetween -54.6 and 55.5 l\1a, The uppn pUT! 01 Zone NP9. thercrorc, mllY be oj' earliest Eocene age. The calcareous nannotos~il data from JeJ2-(I4 indicate n0 missing bioLOn<:,s fwtween Zone NPl) ,md lower Eoccr;e O:'pre.\ian) Zone NPlI). Bybcll ct a!. (1995), howeva, suggest Om! the llpPc'_l part of NPf} m;Jy 1:'>e mi,,,inE nn the ba"j~

Mum·tric1tlirlll

The only Ma
of their analysis of the foss-il assemblages from cores 2065-1.-20652 assigned to that zone, but they also acknowledge that the upper pan of the zone In;J)' be represented by the 8.S-ft uncured interval between cores 20652 and 20651, the latter assigned to NPIO. In contrast. Gibson et al. (19931 interpreted data from four drill holes, including the continuuusly cored Clayton core hole, in the southwestern New Jersey Coastal Plain as indicating continuous neritic depo-tuon from the tarest Paleocene ill\\) tht'. curtest Eocene. In Je32-04, Bybcll et al. (1995) identify Yprcsian calcareous nannofossil zones NPIO - lower(?) 14. They found no evidence for the upper part of Zone NPlU~ therefore, there may b,~" hiatus between LlJIlt:S NPIO uud Ll (between cores 20648 and 20647 corresponding to between 807 and 79,,) rt). A highly condensed stratigraphic section comprises cores 2064':- (757-59 fu through 206:-9 017-19 ft) where zones NP12 throllgh upper 14 or lower 15 are identified within this approximately 50-ft interval spanning abour 4-S million years (Fig. 2). The lowe r/mid die EOCL'ne (Ypre siun/Lutetian r boundary is within Zone NPI4 (Berggren et 'II., 19115a, 1995). Hybe11 cr a1. (1995) state that if core 20640 is in the upper part of Ihis 7.011e 11 would be of middle Eocene age, hut their interpretation, which they admit is 1101 completely conclusive, is that it is in the lower part of NP 14 and thu" of e'lr1y hl',,:en~ age. In lhi~ report. however, I place core 2064U 111 the middle Eocene hut indicate the lower/middle Eocene boundary with a dashed line in Figure 2In light of more recent publications and the new calcareous nannofossil data, reevaluation of the str,tligraphk: distribution of planktic foraminifera from the Eocene of Jd2-04 (Plate 2 of Benson et aI., 1985) yields a revised interpretation of the foraminiferal biozones. The biozones are not well represented by diagnostic- taxa. but a few markIT species allow for definition of a few biozone boundaries. The biozones shown in Figure '2 arc identified on the bases of these markers and on the correlation of the calcareous n,mnofmsil zones with the planktic Iorarniniferal zones by Berggren l't al. (l9K5a, 1995 ), Because of poor resolution, biozones in some instances are combined to conform with the calcareous nannofossil ao.ie.s , e. g., P7-R. Published vrrntigraphic ranges of foraminiferal taxa used in arriving at the revised zonation are from Heckmann (1957), Blow (1479), St ainfo rth e t al. (1975), Tou mnrkin e and Lurerbacher (1985), and Berggren and Miller (1988), plus the data of Miller et al. (1994) who listed taxa for each biozone identified in the recently drilled lslund Beach, New Jersey. cere hole. Berggren et al. (1l)l}5) revised the definitions of some of the biozones. The basal Ypresian Zone P6a (Berggren et al., 1l}9S) occurs immediately above the upppr Paleoc-ene dissolution interval discussed previously. The stratigraphic ranges of all planktic foraminiferal taxa identified by Benson et al. ( (ggS, PI. 2) from thi" interval (ccn-x 20651 tbrough 20648, ,'<.39-807 rn include Zone Pea. Morozovella lcnsitormis. the FAD (first appearance datum) of which identifies the base or the next younger zone Pnb (Berggren ct at. 199:'), i<, absent. Calcareous nannofossil Zone NPlO comprise- the same interval in Je32-04 as Poa (Fig. 2). Zone P6a correl.uc-s witf the middle of calcareous nannofossil zone NPlO (Berggren et aI., I(95). The lowest Qccurrence in Je12-04 of

Maromvetla lensiformis in core 20647 (797-99 ft) identifies Zone P6b, the middle portion of which is equivalent to calcareous nannofossil Zone NPI I (Berggren et al.. 1995). The hase of com hined zones P7 and PH. which correlate to most of Zone NPI} through lower NPI3 (Berggren d a1. 1,,}(5). i- placed at core 20t'44 (767-h9 ft} where Acorinina pen/acamerata becomes common and is generally common to abundant in nearly every core sample from 20644 through ~M1 \ (769-n:\ 7 fl). Benson ct a!' (11)85, 1'1. 2) show a conspicuous break in the planktic Iorammferal assemblages that occurs between core" 2064! 017-W ft) and 20640 I7n-29 ftl and mark"
The lcc e« (rare) occurrences of two species that range no lower than P9 (Toumarkine and Luterbachcr, 1985) occur in rore20641, ACr/riliina spilJuloinflala and A. bulbnmki, and they occur consistently above this core. Zone P9 is the latest early Eocene zone (Berggren et al.. 1985a, 1995); therefore. if P9 occurs in core 20640, it l~ above the geophysical log pick for the contact between the lower and middle Eocene, but it agrees with the assignment of that core to the lower Eocene by Byhell er al. (1995). It does not agree with our as~igning the core to the middle Eocene. One answer to the dilemma is that core 20640 belongs in P to, as discussed above regarding 7: rohri. and that P9 is missing in Je32-04. This IS possible because calcareous nannofossil Zone NPl4 assigned to the core is also equivalent in its upper part to the lower part of foraminiferal Zone PIO (Berggren et aI., 11)951.

Combined zones PI I-P12 from con: 20631 (637-39 fu through ~On25 (577-79 In are defined by the co-occurrence of Chilaguembelina cuhensis. which ranges no lower than Pll, and Acarinina pentacamerasa. which ranges Ill> higher than Pl2 (Tournarkinc and Luterbacher 1',185). Miocene The base of lower Miocene sediments is identified hy core ::'0604 (367-69 ft), which is the base of the perxixtent occurrences of benthic foraminifera typical of the Calvert Formation (Benson et al.. 191-\5. PI. 2). This core and the two above it. 2060 I and 20600,
Two rudiolariun-containing intervals are assigned to lower Miocene global biostratigraphic zones. Tue lower one, Sucnocorys woljjii Zone, is identified by the presence of Spongasteriscus mar-dandicus (Palmer, 1(86), which was identified as Histiastrum martinianum by Benson et al. (198:1) ill core ~0587 (197-9Y tt). This interval i-, the same as the one temporarily exposed updip at the Pollack Farm fl),~si! site near Smyrna. Delaware where its age is estimated as about 18 Ma (Benson. 1~9JJ. The upper radiolarian interval. separated from the lower one by the upper Cheswold sands. is assigned to the Cotocyctctta costata Zone on the basis of the presence of C. costata in core 20579 (I 17-19 U). Hodell and Woodruff ( 1994) estimate the first nppcurnnre datum of this species as about 17 Ma. Abbott (l97R) identified his diatom zones I, II, and III in Je32-04 (Henson ct al.. 1985. PI. 2). These are shown in Figure 2 beside Andrews' (I <;188) correlaticm of his East Coast Diatom Zones (ECDZ) with Abbott's. ECDZ I is defined by the stratigraphic runge of Acnnoptvchus heliopdta. which I h,IVC found III cores 20597 through 20587 i299-197 ft ). 1n borehole Oh25-02 ncar Lewes. Delaware, Benson (1990) found this species from just above the Globorotalia kllgleri Zone to at or ncar the comuct with middle Miocene sediments. Although this verifies that it is a long-ranging species, A. heliopella reruinv its utility in identifying rocks uf early Miocene age. The microfossil groups discussed so far define only lower Miocene zones. Groot (I Ql)2) studied the pollen from the Calvert Formation of Je32-04, but the plant microfossils do not provide the stratigraphic resolution to distinguish lower from middle Miocene. The same pollen slides Groot studied were examined by Laurent de Verteuil as part of his dissertation studies at the University of Toronto on Miocene dinoflagellate cyst taxonomy and biostratigraphy of the Salisbury Embayment. He estabtished dinoflagellate zones with the ON prefix, and these arc shown in Figure 2 for Jd2-04. Zone DN4 spall.., the tower/middle Miocene (Burdigalian/l.anghian} boundary, and de Vertcuil (written cornmun., 1994, 1995: de verteui! and Norris. lY96) places the boundary tentatively at about SIft. just below core 20575, Samples above ON4 are either Langhian «r Scrravalian. and that is why he designated {hat interval as DN4/5. ZOllL' DN5 extends into the lower Scrravalian: therefore, he accepts the lowermost middle Miocene section in Je32 ·04 :IS Langhia» rather than Scrruvalian.

SEDIMENT ACCllMULATION RATES Figure 3 is an age-depth diagram fur Je32-04 constructed fnun the revised blostrutigraphic data and the age estimates (l\la) given in Figure 2, Table 1 lists the sediment accumulation rates calculated I'm each stage or series represented in the borehole. The diapram has nearly twice the number of biostrutigraphic control points as the earlier diagram of Je32-()4 hy Benson ct al. (191{5, Fig. 4). Some of the points ill the latter are now known to be in error and others arc in positions determined from older time scales, since revised or superseded. The revised diagram still shows six recognizable unconformities (horizontal lines), but hiatuses arc of different magnitudes, and some of their positions nre different from those of Benson et al. (J 985). I remain in agreement with

TABLE 1 Sediment accumulation rates. JcJ2-{)~ Stage/Series

FormatiOll

60

I 40

I •

20

Age,my Figure;\ Age vv. horehu'c depth diap rum of Je32-0..\ based 011 datil in Fit:lIre 2.

their interpretation that the two youngest (middle Eocene/lower Miocene and middle Miocene/Pleistocene) and (he oldest (upper Campanian-lower Turonian/Santonian) unconformities represent subaerial exposure and erosion. Higher average sediment accumulation rates arc associated with chronostnnigraphic intervals containing the coarsor-grained units deposited in shallow to marginal marine environments (vee Benson et ul., J985, PI. 2). namely, the Magothy (Santonian), Piney Point (middle EOL"tne), and Calvert Ilower-middle Miocene) forrnauons. The condensed interval straddling the lower/middle Eocene boundary t zoncs NPll-14/J5) has a relatively low rutc of about 7 ft/my (2 mhny). Nearly all of upper Paleocene Zone NP9 comprises the dissolution interval mentioned previously, and its rate of sediment accumulation is high, about 71 ftimy (22 m/myt. As discussed hy Benson er al. (985), as an alternative to the carbonnre dissolution hypothesis a high sedimentation rate may have masked or diluted the biogenic contribution III the seJinwnts during this time, resulting in a ncarly barren interval.

9

Wmy

174

57.2 19.4 21.0

Santonian

Magothy-Iower Merchantville

Campanian

upper Merchantville-Mount Laurel

Maastrichtian

Navesink

Lower Paleocene Homerstown

Pge vs. depth, Je32-04

m/my

59 64 98

32,0

Upper Paleocene

Vincentown-lower Deal

113

37.0

Lower Eocene

middle Deal

Middle Eocene

upper Deal-Piney Point

53 15.8

Lower-middle Miocene

Calvert

20.1

17.5 520 66.0

I!J

1

_ NON·CLAY MINERALOGY OF THE MATRIX (SILT·CLAY) OF Je32-04 CORES Nenad Spoljaric lNTR()DLICTION

RESllLTS

The present study l~ focu-cd
Potomac Formation Quartz is the dominant mineral; its content decreases upward in the section and i-, th .. lowest at the unconformable contact with the overlying Muguthy Formation. Pyrite is the second mo-it signifiL-ant mineral in the middle portion of the P{ltIHlHlC and siderite of the upper. Feldspar is a minor component observed in several samples. and hematite is also present.

non

Magothy Formation A.s in the underlying Potomac Formation, quartz is the most abundant mineral. Pyrite is common and particularly abundant in the middle part of the formation: siderite and feldspar arc present in the upper part only. Calcite and arag{mite arc present as traces in several samples. The zeolites analcime and phillipsite are also observed in the middle and uppt'r parts of the formation. respectively. The Potomac has considerably more siderite and less pyrite than the Magllthy. Merchantville Formation Abrupt increase in the calcite content at the base of the formation and decrease in the quartz content occur just above the Magnthy/Mcrcbaruvillc boundary at 1265 ft. Aragonite is alsll an important component of the mineral suite. Siderite and pyrite arc present throughout. Phillipsite, traces of dolomite, and marcasite are also identified. The Merchantville coruains significant amounts of calcite hut the \bl!llthy only traces. Siderite is an important constituent thr:llIghlHlt [he Merchantville, whereas the Magl'!hy has some in the uppermost part only. Pyrite is eonsidcrahl y more abundant in the Magothy than in the Merchantville.

I\IETHODS One hunJreJ and forty core samples from Je32-04 were used in the present study. After mechanical disaggregation, the silt-clay fraction of the sediments was separated from the coarser fraction by dry sieving and ground to a powder suitable for x-ray diffraction analyses. Powder-samples prt'pared for the analyses were x-ruycd on the Phillips PW 1729/ 1840 diffractometer. Results of the study are presented in Figure 4. As the results are of the matrix only they should not be interpreted as characterizing the bulk of any particular stratigraphic unit unless matrix is the predominant component. as shown by Benson et 'II. (1985, PI. I). Their thin-section point counts indicate that matrix percentages range between about j and 87 for the Je32-04 core samples they studied. The numerical values as~ibned to individualminerals in Figure 4 are bas~d on heights of the strongest peak of each mineral on each diffrw.:to~r:Jlll. The' values were recalculated using 100 as a haec and new nnmencul values assigned to the strongest peaks. Becau-,.. the strongest peak-heights of different mineral" nrc highly variuhle. different scales were used in prescntation of the results. as shown at the top of each mineral column. These are not quantitative results. The data simply "how the semi-quantitative variability of each mineral idcntiflecl from die marriv component throughout the section. This kind of comparison is meaningful because all the samples were prepared and x-raycd in the same way. Results are summarized for each of the lithostratigraphic units of Je32~ 04 as identified in this Bulletin.

Englishtown Formation Quartz is the major component of the mineral suite. Calcite is present throughout, whereas aragonite is found ;11 the base of the formation only. Pyrite occurs in the lower and middle parts, and siderite and goethite arc present in most samples from the upper part. Charucrcristic.dly. the Englishtown contains feldspar, hut generally hld..s .lragonite, unlike the Merchantville which has small amounts of aragonite but little or no feldspar.

Marshalltown Formation QUllrtz. und calcite un- the predominant minerals. Pyrite IS present and is mon- common in the lower than in the upper pan of the formation.

Muunt Laurel Formation The main c har acr eristics of the Mount Laurel Formation are the predominance of calcite, small amount of quartz compared to the Marshalltown, and almost complete absence of pyrite. Calcite dominates the mineral suite of the Mount Laurel matrix as was noted by Rasmussen et al. II

(1958) who characterized the section as comprising chalk and marl. The hulk of the calcite consists of planktic micro. fosviis. primarily calcareous nannofossils

ter i, present in trace amounts only. Dolomite is also presl.:rl! in trace arnounr-, sporadically throughout the formation. Pyrite is present; siderite and marcasite are rare. Hematite is identified at several Icvejs ; phillipsite and vivianuc are each found in one sample only. Traces of talc are also detected. Sulfates jarosite and alunite arc present in »ignificant .1111(1unts throughout. The characteristic features or the Calvert Formation art: almost complete lack of calcuc. persistent and relatively high aragonite content, presence of trace amounts of dolomite, presence of pyrite and hematite. and significant content of jarosite and alunite. None of thc above is of particular importance in the Piney Point Formation.

Navesink Formation In contrast to the Mount Laurel which is dominated by calcite, the Navesink Formation contains just slightly more culcirc than quartz. Siderite is the only other mineral idemifled and is present in trace amounts only. Hornerstown Formation Quartz is the most abundant rninc ra l in the Horuerstown in contra..,t to the Navesink, hut calcite is also present in significant amounts. At the base of the formation dolomite, jarosite, marcasite. and rare phillipsite are characteristic members of the mineral suite that nre absent from the Navesink. Feldspar, pyrite. and siderite are also present.

SIGNrFlCANCE OF [\'frNERALS AND MINERAI ..o\SSOCIATIONS

I

J

Jarosite and Alunite

Vincentown Formation

The worldwide occurrences of these minerals arc variable and range from areas of acid-miue drainage (Nordstrom, 1%2; Chapman et al., ln3: Filipek et al.. 1987; Alpers et ul., lY88; Karlv-on et al.. 1988), oxidation of sulfide minerals (Nickel, 19x4; Scott, 1987; Sullivan et al.. 198b), crystallization from hydrothermal solutions (Rayruaha-huy, 19M:: Ahaner et al., 198RI. weathering in aut! soils (van Breemeo. 1973; Panning ct al., 1(93), III evaporation frons ncid water (Long and Lyons, 1(92). In Je32-04. both jarosite and alunite arc present primarily in finer sediments (silts). although they are also found in several sand beds. They arc most abundant in the Calvert Formation. Jarosite i., also found in several parts of the Piney Point, Deal. and Hornerstown formations. Alunite in trace amounts is detected in tbe Deal Formation, Considering the known occurrences of jarosite and alunite, there are several possibilities that probuhly can be eliminated from consideration to explain the presence of these minerals. Origin in acid-mine drainage, weathering in acid soils,
Quartz is by far the d ominurn mineral of the Vincentown matrix, although ill the lower part calcite is present in xiguificant amounts. The upper part is calcite-deficient Aragonite is present in thc upper half of the formation, and a trace of talc is identified 111 the lower part, both of which are absent from the Homcrvrown. Pyrite, siderite, and marcasite are present at ~everal levels as is feldspar.

Deal Formation In the lower half of the formation quartz is predominant A calcite-deficient (dissolution) interval extends from the Vincentown for about 50 t't into the lower Deal. Above that. the amount of calcite Increases and docs so significantIy in the middle Eocene part of the furmarion (Shark River equivalent) where it peaks and exceeds quartz as the dominant mineral. Aragonite is rare or several levels except lor the uppermosl part of the formation where it shows a significant peak as the Deal grades upward into the Piney Point Formation. Marcasite and, to a lesser extent. pyrite also show major peaks at the same Jcvd. Feldspar, dolomite, pyrite, siderite, hematite. anutcime jarosite, alunite, goethite, vi vianitc, and phillipsite are present in trace amounts at various levels: most of these were not found in the Vincentown. The Vincentown also contains considerably less aragonite than the Deal. Piney Point Formation Quartz exceeds calcite throughout the Piney Point. In the lower and middle parts, aragonite is present. dolomite is rare, and sidcrin- occurs sporadically. Only a truce of pyrite is found in the upper part and at the base. Marcasite is identified at several levels and guethite in the upper part of the formation. Jarosite is present ill the lower part. and the zeolite laumontite occur, at two levels. III contrast to the Deal Formation, the Piney Point has ch.vacteristicalty more siderite; however, it almost completely lacks pyrite.

Calvert Formation QUMtz is hy far the dominant matrix mineral of the Calvert; feldspar is present in most samples and is second in abundance to quartz in two samples in the upper part of the formation. Aragonite is more common than cak-ite: the lat-

Talc

The prese-nce of tall' at several levels in the section (Calvert and Vincentown Ior mauons] is vcry difficult to 12

I

J

explain. Talc is extremely rare as a detrital mineral because it is very soft and is easily destroyed in transport; here it is most likely authigenic. lt forms primarily by hydrothermal alteration of uluubusic rocks or thermal metamorphism of siliceous dolomites (Deer cr aI., 1962; Ross er aI., 1968). However. there is no other direct evidence at present that either of these processcs operated in the area during the Tertiary.

Aragonite

\ I

At several levels in Je32-04, aragonite is either the only calcium carbonate mineral present or it is more abundant than calcite. Most of this mineral probably represents finely comminuted shell material. This is generally supported by the presence of significant amounts of shell material found at the same levels.

Dolomite This mineral has been detected in trace amounts at various stratigraphic levels. It is often associated with calcite in carbonate rocks. It can form from hydrothermal solutions by alteration of magnesium-bearing igneous rocks, by prccipitation from sea water, and several other ways. The significance of dolomite in Je32~04 is not known: however, it appears to be primarily authigenic. Jordan and Adams (1962) reported dolomite rhombs in core 20666 immediately above the Cretaceous/Tertiary contact in Je32-04, the same core in which they found a thin bentonite layer containing altered volcanic shards.

\

I

Pyrite and Marcasite These are the only two sulfide minerals identified. Pyrite is significantly more common than marcasite and is present in all the formations; it is particularly well developed in the middle part of the Magothy Formation. Marcasite is present in the upper part of the Merchantville, uppcr part of the Mount Laurel, Horncrstown, and Vincentown. upper half of the Deal where it is most abundant, the Piney Point, and lower part of the Calvert formations. Both pyrite and marcasite are probably primarily authigenic minerals; pyrite is known to fill the interior or replace the calcite of foraminiferal tests. Presence of marcasite indicates acidic conditions in the environment in which it developed. Both minerals arc stable under reducing conditions.

Siderite With the exception of the Calvert, Hcmerstown, Mount Laurel. and Marshalltown formations, siderite is well represented in all other formations, but is most abundant in the upper part of the Potomac, top of the Magothy, at the base of the Merchantville. and in the middle part of the Piney Point formations. In sedimentary rocks, mudrocks in particular, siderite is most commonly authigenic (Blatt ct al., 1972) and is usually associated with pyrite; this also seems to be the case in JeJ2-04.

hculanditc which arc found in all formations except the Merchantville and Mount Laurel (reported by Spoljaric , 1988). The presence of the zeolites testifies to past volcanic activity. The most recent evidence for such activity is the discovery of many layers of silicic volcanic ash in Caribbean sediments that indicate that explosive volcanic episodes. probably in the Central American are, occurred during middle to latest Eocene and early to middle Miocene times (ODP Leg 165 Scientific Party, 1996).

Hematite Primarily trace amounts of this mineral arc found in a few samples only. The occurrences are limited to the Potomac, the basal parts of the Deal, the Piney Point, and the middle and upper parts of the Calvert formations. Hematite is probably detrital here, but some may be of possible hydrothermal origin.

Goethite This mineral is most likely authigenic. formed by alteration of other iron-bearing minerals such as pyrite, siderite, and hematite. This seems to be supported by either a complete absence of these minerals, or their presence in only trace amounts in the samples containing goethite. Goethite is found in the upper part of the Engl ishtown, middle part of the Deal, and upper part of the Piney Point formations.

Vivianite Vivianite is found in significant amount only in one sample in the upper part of the Calvert Formation. Two other occurrences arc recorded, in trace amounts, near the base and in the upper part of the Deal Formation. Vivianite appears to be authigenic. formed probably as an alteration product of phosphates or is associated with organic material in the sediments.

Quartz Quartz is by far the most common mineral identified and is probably mostly detrital in origin. lt is the predominant component of the mineral suite except where calcite is predominant in the lower part of the Merchantville, the Mount Laurel, lower half of the Deal, and the uppermost part of the Piney Point formations. It is, perhaps, important to note that the quartz content shows a fluctuating, but nevertheless very distinct upward increase from the ba-,c toward the top of the Piney Point Formation.

Feldspar This mineral is usually present in trace amounts only and is found in all the formations except the Marshalltown. Mount Laurel, and Navesink formations. Only two samples in the Calvert formation contain significantly more feldspar, almost equaling the quartz content in the same samples. Feldspar is most likely detrital.

Zeolites

Calcite

Analcime, laumontite, and phillipsite are all found at various stratigraphic levels in the section. Collectively, they arc present in all the formations except the Potomac, Englishtown, Marshalltown, and Vincentown formations; however, they are not nearly as common as clinoptilolite/

The first appearance of calcite is recorded in the Magothy Formation (trace amounts). From the base of the Merchantville Formation, calcite is an important and persistent member of the mineral suite throughout the section up to the unconformity marking the top of the Piney Point

Formcuon. Above the unconformity. m the over-lying Calvert Formation, calcite is present in trace amounts only. Calcite is the predominant mineral in the xtount Laurel. middle pan or the Deal, uud the uppermost part of the PinL"y Point Formations. Most of the calcite probably compri-c-, calcareous rnicrofosxils ; the variability of the relativc amount of calcite appears to be correlative with the variability of microfossils; however. SdlllC calcite may be detrital. and some possibly precipitated from sea water.

gested that the earliest middle Eocene climatic cooling may have been a reverse greenhouse effect that ncwelily brought about unusually high silica accumulations

Lower Homerstown This thin interval (-15 feet thick) is characterized hv the largest amount of dolomite in Jc~2-04. The interval abo contains jarosite. marcasite. and phillipsite. in addition to quunz and calcite. A bentonite layer, reported by Jordan and Adams (1962) is .1!.sO present here. The bentonite layer is a good marker bed and directly records a past volcanic crupnon somewhere in the region. The dolomite may be: a product of alteration of zeolites and some other minerals to bentonite. with Ca supplied by zeolites and Mg by Mg-beanng mineral, such as mica." mixed-layer clays, and others. Jarosite probably formed by oxidation of marcasite.

I:NlISliAL !\lINERALS AND MINERAI. ASSOCIATIONS Several minerals und mineral associations of the matrix in Jd2-0..j. are of a particular interest because they arc either unusually abundant or form unusual associations.

Upper Vincenlown-Lowermost Deal Ilac. the unusually low calcite content is the our-nanding characteristic of the minerai suite. Gibson cl;l. (l99~) made a similar observation nt the same stratigraphic level in the Cjavmn, New Jersey, core hole; they referred to it as a dissolution interval Although the explanation for the calcite dissolution is not Known. they suggest it could be the result of local ~n>und-watl:r permeahility or "orne other locu! cause but could also he caused by a global phenomenon. Gihson et al (1993) also noted a significant increase in the kaolinite content followed by a decrease within about a lOcmetcr (33·ft) interval spanning the Paleocene/Eocene boundary Just above the dissolution interval in the Clayton, New Jersey. core hole, They report having found this kaolinite influx in other boreholes between at least Virginia to New Jersey within the same stratigraphic interval. Spoljaric (19XX) identified kaolinite within the Paleocene/Eocene boundary interval ill Je32-04, but it does not show the major inc tease followed by a decrease as it does III the Clayton cere hole. By-bell et ul. (190:") uuribute the uhscnce of scdimente containing the kaolinite increase (0 the downhasiu position of Je32-04 which was not reached by the major influx or kaolinite sedimentation They also suggest that ...ediments containing the kaolinite decrease in the uppermost part Ill' Zone NP9 and lowermost part of Zone NP r0 may be absent owing 10 the downbas!n position of Jd2-04 so that sedimemmiou did nor reach rhc area until somewhat after the time or kaolinite decrease. Also. they consider that all or part of the kaolinite uccre:lse may be- present in a condensed stratigraphic interval within tile uncored R.5-fl seclinn between cores 2U652 (Zone NP9j and 20(:i,'i I (Zone 1'.'1-'10). Extensive late Paleocene and early Eocene volcanism is recorded by the presence of clinopulolire/hculandite in Je32-04 t Spoljaric. 198X). Mc Gowran (19fl{)) notes that period coincided with a time o( enhanced crustal activity. ROlla and Richardson (l97S) report that significant global plate reorganization look place at thai time. Thiv ucuvity accompanied by extensive volcanism and early Eocene warming brougbr about an increased accumulation of silica in the ocean- and deep weathering on land. evidenced by abundance of kaolinite. Kennett (1982) provided a detailed theory of silica urcumulation and linked it, in addition to the above factors. al-,o to warm/cool climate change and biological activity. MeGowran (I 9W)j went a step further and sug-

Upper Deal This sequence is characterized hv the presence of the largest amount or aragonile in the section. Other minerals present include hematite and marcasite, although they are not found together in the same samples. Pyruc, however is associated with both hematite and marcasite. At the ha-,c, this sequence abo contains a trace of talc. Mosl 01 the aragonire content probably originated in fossil ~hdJs, which is supported by a positive relationship between the abundance of aragonite and shells (Fig,. 2 and ·n. The other most distinct mineral ill this section is marcasite. It is a common mineral in many scdimentnrv and carbonate rocks. and Its abundance in this particular section indicates unusually acidic conditions in the environment at the time of its formation, Because pf these conditions, the abundance of urngonire is difficult to explain. BlaH et al. (1972, p. 459) offer the following explanation for the occurrence at three localities or unaltered aragonitic fossils. subject to acidic conditionx, of Paleozoic- age m host rocks with abundant organic matter. The ahiliry of organk matter to preserve original [arag . cniticl sneu material results not only from the reduction in permeability it causes but abo from the ability of amino acids derived from the breakdown or proteins in the shell to keep water molecules from contact with the calcareous material. Whether or not this explains the abundance of arugonue in the varnples studied requires further rcscach beyond the scope of this investigation.

14

L

_ SUBSURFACE STRATIGRAPHIC CORRELATION OF SELECTED BOREHOLE GEOPHYSICAL LOGS FROM CENTRAL DELAWARE AND NEW JERSEY Richard N. Benson

INTRODlrCflON

Formation arc in contact with tilt: underlying, usually hard, variegated red, white. orange, and hrown clays or the Poromuc Formaritm. Where tho: Magotf',y is tIli~,ing. the dark gray to greenish-gray. micaceous and commonly glauconitic silt-clays and very fine s,lI1ds of the Merchantville Formation overlie the Potomac clays. In order to better illustrate the thickness Hurl facies changes in the Tertiary units between Olln-04 and J«12-04. 1 use the base of the Miocene as the datum for Figure 6 and have added several irfill wcIlc 10 Ihe noss vccrion. In a departure From a true stratigraphic eros, section [ include two faults of pre-Miocene age that an- probably growth faults that, at least in part, controlled accommodation space for the accumulation of Paleogene sediments (Henson, 1994). Comnl] for correlation of the ge()~)hysical Jog markers for the unconformity between lower Miocene and midtile Eocene rocks is from palcontologjc and lithologic data for k32-0-l. rBenson et .\1., 19x5: Benson. this r~lI11etill). Jordan ([962, PI. I) for Gd31-04. plus -ny examination of sample_ from mo.sl of the other boreholes of Fiuurc 6. From lithologic logs in DGS files. the unconformity can be recognized in updip boreholes where gray. brownish- ur greenishgray, shelly silts of the [ower Miocene Calvert Formation overlie glaucoutuc sands C'snlt und pepper" sands) or green glatKonitic cby-sills with, upon further inve stigu.ion. middle Eocene fossils. On gamma-ray logs there is a positive response or "kick" at the uncor.fmmity. Downdip wher e the casar glauconitic sand of the Calv<.::rt overlies the gIaur'<'nitil: sand of the Piney Point as in Jc32-04, the unconformity is identified by gt;"'ophy,icaJ log rc.,>pon.Sl'.s ;"lud is co-rohorurr-d by paleontologic data

iootan : 1962) oroposcd II .stratigraphy (or Delaware that incorporated the names of rock streugraphic units primarily ('f adjacent New Jersey bUI also of Maryland. He recognized the facies changes along strike in those units hut was unable [0 extend units in the t'UluUIJ belt very far into the sub-arrface For example, Ill: rel.:ognizeJ Ihal iJcmifi,lbk

Upper Cretaceous formations or the Matawan and Monmouth groups exposed ill the (' & 0 Canal when trac-ed downdip form a single lithic unit; because of this he ranked the groups as formations (Jordan. 1962, Fig. 3). Since that rune. many horehoks han: been drilled. dll.J there have been major advances in mostrangrapnv that have IImde it rossihlc to id~ntif} vtratigraphic units in the suhsurfuce. With this added control, it is now possible to recognize facies changes within those units a" o1Jkn>p or near-surface secti
Results of Oeophyslcet I .og Correlations Figure 5 displays the thrpl' Delaware boreholes with the best stratigr;lphic c('/ltml thaI pendr;,le the entire postPotomac section of central Delaware and the continuously cored U. S. Geological Survey (USGS) borehole near Clayton, New Jersey. Pubrtcarrcns or hi\lstratig~aphic and lithologic information from the Clayton core hole are those OfOlbsoll er al. (ENJ) and Gib,~lln and l-lybell (1994) on ibe lutcst Paleocene 10 lowermost Eocene section, Bybell and Self-Trail (I99S) on the Cenozoic section. Sugarman ct ai. (1995) on the uppermost Carnp.mian-Maastrichtiun , and Owens ct al. (1995) on the entire stratigraphic section. The gL.lhal calcareous Il;(tmofo~.sil bi('zon('\ Iprefixe'i L'C <.lud NP), geologic ages. and [ithostraligmphic units identil"ied hy th0se authors are indll>oted in hg:ure 5. The KCI ;Jnd KC~-4 cycles are th\'~e of Owcn, ct al. (1(J')5l and mclud~ the lilhoslrotigrapllie unils iden1ified in the fi~ure. The gat11ln,lray log and paleontologic anJ lithologic daw from lhi.~ 1..'01<':hole provide the primary updip control for all three stratigraphic l'ro~s s('ctions of Figures S-7. The biO'>trntigraphy and chronostratigraphy or Je32-04 disl'ussed previously !Benson, this volumc) provide the downdip eonlrol for the correlations.

STRA TIGRAPHTC CROSS SECTIONS Stratigraphic cro», secnonx are constructed to illusuare stratigraphic correlations. unconformities. thickness and facies chungev. and other snutigraphic chamcreri-tics. The datum for such a section is a stratigraphic marker that is usually displayed as horizontal. thus eliminating the distorting effects or folds and faults (Tcarpock and Hischke, !
There is good geophv-ica l Ic>g r orrelmion of the Magothy, Marshalltown. Mount Luurcl. Navesink. and Horncrstown formations between the bprellllle.s of figure 5. The biostratigraphically determined age, (If the formations agree. The unconformities indicated hy missing biozones correlate and comprise the lower and upper boundaries of the Navesink (or Navesink-Red Han" in New Jersey) and Hotner stown formatiou s 'J'he contact between the Cretaceous and Tertiary sectionx i-, the: unomforrnity indicated by missing hiozone s between the Navesink and Hornerstown. Sugarman ct ul. (1995) indicate their KC4 cycle in the Clayton core hole as comprising the middle to late Maastrichtian Navesink-Red Bank interval of New Jersey from which biozones CC25c-26 are identified, whereas in Delaware, the slightly older biozone CC25h occurs in the corrctauvc interval in Je32-04. This interval, therefore, is slightly older downdip in Delaware than in updip southern New Jersey. On the basis of Sr-isotopc age, cvrirnutcv. Sugarman et al. (1995) conclude that the base Ill' the Nave-ink sequence (KC4 cycle) is older in the northern pan of the New Jersey Coastal Plain than it is in the southern pan (69.1-69.2 M'l vs. 67.9 Maj. Data in Delaware are iusurrlcient to identify the unconformities between the Magothy and KCl cycle (Men-hnntvillc-Englishtown formations) and between the KC I and Ke.' cyrll'S indicated by Owens et al. (J995j for the Clayton cPIT hole. although in Je32-04 the queried sample between WI1L'S CCl') and CC20 may represent the equivalent or the mi,~sing KC2 cycle of New Jersey. In Dclawaru, the upper Magothy comprises interbedded sands and sills ;"is revealed by the geophysical logs in Figure 5, bUI the upper Magothy in the Clayton core hole is all sand. Either the upper sands and silts (If the Delaware Magothy undergo a facies change tv all sand in New Jersey or they are absent in New Jersey as represented by the unconformity in the Clayton core hole At the base of the Merchantville, the absence of calcareous nannofossil zones CC 15 and CC17 in the Clayton core hole but their presence in Je32-U4 is evidence for the unconformity in the former but supports the gradational contact without an unconformity between the Magothy and Merchantville in the latter. In Delaware borehole GdJ3-04, split-cpoon cores were taken at irregular intervals, and age dererrmnauons of those examined for foraminifera are shown in Figure 5. Planktic foraminiferal biozones, if identified. are mdrcared by Fl. Palynomorph age determinations (Jchnn. J. Groot. written cornmun .. 1993l were made on three cores and are indicated by PS, and lhcy serve 10 identity the Paleocene/Eocene boundary interval when' the tomnuniferal data are inconclu»ivc (queried biozones P5'! and P6?). Groot notes that Choannpotlis indir nte s a Paleocene age and occurs with many pollen of gymnosperm- and simple tncolpmc and tricolpornte pollen th.u are ub,o found in the Late Cretaceous. Jordan (JtJ6~. 1'1. I) published the geophysical log of Gd33-04 and id<,ntifi;:J lithostratigraphic units which he recognized at that time as characteristic of Delaware's subsurface stratigraphy. Uuit-, recognized in Gd33-04 in the present study arc based on the correlations shown in Figure 5. In Gd33-04, the Potomac/Magothy contact is as shown by Jordan (1 %2, Pl. 1). By geophysical log correlation the Magothy/Merchantville contact is at a depth of 5~6 n. the top of a sand containing lignite that is traced ttl k:l2-04

where it also marks the top of the Magothy as recognized in this Bulletin as well as by Benson ct al. (1')85); Jordan (1962) put the contact at 620 ft in GdJ3-04. The micaceous and glauconitic silts and very fine sands ,11" the Merchantville Formation r5R7-';;02 ru rom-cponc approximately to the Matawan l-nrm.uiun of Jordan (19fi2) who placed the top of that unit in (;u33-1);.1 at 490 teet. Jordan's (1')62) Monmouth Formation (4l}(k~20 teet) comprises the following units I now rcrognize ill Gd33-04: the coarsening upward fine sands of the Englishtown Formation identified hy its characteristic geophysical log signature 1502-459 It]: the glauconitic sand of the Marshalltown Formation (45943R ft]: the thick, fine to medium. somewhat glauconitic sand of the Mount Laurel Formation (438-336 ft): and the gluuconiuc. micaceous. medium to coarse silty sands of the Navesink Formation (336-3 J9 ft), These units correlate with those of the Clayton. New Jersey, core hole; however. the Englishtown interval of the KC I cycle is not identified Oil the gamma-ray log of that core hole as there is probably a facies change from sand to silt between GdJ3-04 and it, The Navesink is the only unit of Maastrichtian age in Delaware. Woodruff (1990) included the Navesink of this report within the Horncrstown as together they comprise the interval of high glauconite content and more clay that chowan increased gamma-ray response compared with thaI
1

_ log signature of the aquifer (plus an overlying sand section) closely resembles that of the Vincentown-Manasquan (Rancocas) section of Gd33-04. The gcophysicu! logs of Gd33-04 show a thin silty interval between 19R and 208 ft in the upper part of Jordan's Rancocas (rig. 5: Jordan. 1962, PI. 1). The sandy section above Ihis interval L""ntains the Paleocene/Eocene boundary ,lS determined hy thc planktic foraminifera

sand, green W gray-green. massive to finely laminated. c xtcnsivcly bioturbated. and with ut-und.mt calcareous

microfossils. This matches the description of the Manasquan in the Clayton corcholc by Gibson et nl. (II)'I~), Owen" er ai. (1995) assign a latest Paleocene through t'arl) Epcene age (calcareous nannofossil/ones upper NPI) tll within NPI3) to the formation. The Manasquan Formation 111 Gd.l.1-1J4 represenrs the subordinate Farmingdale lithn]pgy (f:\I:ie, cbanpe described above) of the formation and l'\,rrl'sponJs til the lower Eocene and uppermost Paleocene pan or Jordan's (1962) Rancocas Formation. The Shark River Formation of middle Eocene age unconformably overlies the Manasquan in the Clayton COl"Chole, Its lithology is indicated graphically by Bybell and Self-Trail (1995) as a glauconite sand at the base followed by interbedded clay-silts. clays. and glauconite sands with a glauconite sand at the top unconformably overlain by the Kirkwood Formation of early Miocene age. The lower twothirds of its geophysical log .,ignatun: is nearly identical to that or the interval 111 Gd.l.l-04 that jordan (1962) referred to ,lS unit C, a green. glauc(lnitic, finc, clayey sand grading below to glauconitic silt. [ r~'~·ogniL~· unit C as the lower part (It the Shark River Formation of New Jersey and propose that the remainder of the fomuuion is absent in Gd330-1 in Delaware owing to its eruSi,11I prior to deposition of the Culvert Formation during the e:lrly Miocene. In the subsurface of the southern New Ja.,ey C,ld.sl:!1 Plain. Owens ct al. (1995) de scr-ibe the Shark River (middle and upper Eocene where thickest. containing calcareous nannofossil zonc-, upper NI'14 to lower NPI~i as typically more sandy (YU;trt/D"C) in updip areas and more clayey downdip. Updip. they recognize that beds are cyclic wirh a fine to medium. somewhat clayey. fos..;ilifernu" gtaucouite-quartz sund ut the base with a general increase in quartz sand upward. Locally, some of the beds arc more clayey and shelly than usual. They describe the downdip facies as vel') clayey. fine glauconite sand in the lower part with a similar but medium to coarse glauconite sand aL the top. Jordan (1962) did not apply the names Manasquan and Shark River to the subsurface units in Delaware. His understanding of the Manasquan was that it referred to a glauconitic sand and that it could not be used for the silty sediments of his unit C. Information was not available at the time for him to recognize that the upper glauconitic sand or his Rancocas formation is correlative with and of the same lithology as that of the Farmingdale Member of the Manasquan of New Jersey [IS Jordan's (1962) study preceded Enright's (1969) publication Regarding the Shark River, Jordan (1962) recognized that it resembles the unit C lithlliogy in Delaware, but authors he cited indicated that it i~ apparently restricted to Monmouth County. New Jersey. It is. however. now recognized in the subsurface of the SOUl han Coastal Plain of New Jersey as discussed above. ln contrast with Jordan's (1962) rejection of the name Nunjem'ly because it is not accurately descriptive (If unit C ill Delaware, Pickett and Spoljaric (1971) substituted that name for unit C, sl~\ting that Its lithology is sufficiently ximilar to that of the Iornusion III Maryland. that the two arc sufficiently stratigraphically equivalent, and that the name has been used "unofficially" in Delaware in the past. They describe the Nanjemoy. which dot'~ not crop out. as a green

(between zones P4?P5? and P()·)) :.U1U pollen (Fig. 5). As the

Paleocene/Eocene boundary uc curx within the clayey Manasquan in the Ctayrcn, New Jersey, core hole, [identify the upper sands of Jordan's Ranc
17

l

_ and dark gray. glauconitic silt and clay. with some fine to medium saud. This des.nptio-r docs not differ markedly from Ih:'11 of rbc Shark River which I name f"f unit C. By ut)ing thi- I retain New Jersey terminology for the entire updip stru1igraphk section in Delaware Ircm till' Campanian Ihrotlgh lt~idJIt: Eocene. Woodruff (1~90, cross-section A-A') referred the 90-ft interval between the Calvert fo-matinn ,1nJ Rancocll,' Group ill well Gd;\ 1-02, located 1,4 miles updin from Ud33-04 (~i!,. 4). to sands or the Nanjemoy and indicated that the Nanjemoy is probably cquivulcn! to tile Manasquan Formation of New Jersey. Correlation of geophysical logs between the two wells shows IhJ[ his Nanjemoy inkl val j, r-quivulc nt to the M<.ll1a"qu:m-Sh;.trl.: River interval or GdJ3-(14. In Gd31-0~, the lower 30 Icer of the Shark River shows the geophysical log sir-nature of a sand. and Ihis combined with Ihl' l\Ian:l.sqllan indicates a predominantly sandyfvanjemoy." Downdip in Je32-04, Jordan (1902, PI. 2) named unit A for the cnure!v subsurface fil1c-grain~·d unit that extends n-om t hc top of his Monmouth Formation (Upper Cretaceous) at 1(l90 It. which is just above the top ot the E1l2Ii.,h((}wll Formation (J [O~ rn as r ccoguizcd in this Bulletin, to the base ot the middle Eocene Piney Point Formation at 615 ft (5X4 ft in :his Bulletin). He dCSLTi1>eJ it :IS light gray to bluish-gray, rroocrarety glauconitic silt and cluy, being the finer-grained downdip facies of the upper part of his Monmouth f-urmario». unit H, (he Rancoca-; and unit C ofGd33-0-t.. Although its usage was nor formulized, Pickett (l lI72) suggesteJ the nanJe I'amunkey Forrnution for unit A as the d own dip j"illcl-glailH;J facic s of the Horners to wn, Vincentown (both Nev.' Jersey names) Lind Nanjemoy (1I.laryland-Virginil name) formations. As subdivision of unit A was not considered feasible at the time. he suggested relegaung Pamunkcy Group to form:"lHIll rank, Jordan i 14(2) recognized the usage of Pamunkey in Delaware by early workers, hut he r cject cd the name Pamun kev Fnrnuuion for hi, ~·"ncerf of the R;mcn~'as Formation. Ward (I\lX5) summar-izes the history of investigations of the Pamunkey Group and the latest information on the l1owcd PiL'l.:ct(.s (1972) ~llggestion, and
of the interval, but four subdivicionv were detected. primarily from their ,geophysical log ,\ignatun;~ 1055-1045 n, a sand "kick" within the lower vtouut Laurel Formation of this Bulletin: 1045-'120 ft, glauconitic silt~ becoming very gmJunlly and irrcguturly finer grained rcompri-c-, the remainder 01' the Mount Laurel, the Navesink, Hornerstown. and most of the Vincentown pi this Hulletin): 9411-7.f2 ft. a uniform silt interval (comprise, the upper Vincentown and Paleocene through lower Eocene part of the Deal Formation or this Bulletin): and 742-585 fr, Ins ur.dunnilY titan the last interval and a tendency to coarsen upwards (comprises the middle Eocene P~llt of the Deal Formation). Ols..,on and Wi,,,· tI9S?;) p. 11';.11 recognize the Deal as a formation comprising the dominant lithology in the subsurface Eocene section or the New Jercev Coastal Plain ..where it becomes increasingly clayey; it extends From the rower Eocene to the middle Eocene. It is vcry rich in microtossils. including foruminifer.\, coccoiirh-. dinoflagellates, and abundant siliceous microfossils (radiolarians, diatom" sponge spicules). I identify the fine-gr;(ined vnir between the tor of the Vincentown in Je32,04 at 898ft to the base of the Piney Point Formation at 584 ft as the Deal Formation. As shown in Itigurc 2, it is a ,:;laucollitiL silt und clay unit r-ic-h in tho microfossils indicated by Olsson and Wise (1987aJ and or similar age to the Deal. although at its na.'e I abo include the upper Paleocene glauconitic quartzose silts above the vinccntown, which, m New Jcrve.y , Olsson and Wis.: (19R7a.l:» ICelV<: acan Ullnamed subsurface unit. Enriuht (1%9) exrahlished the Deal as the upper member of the Manusquun Formation that overlies the glauconitic vmds of the Farmingdale Member. Olsson and Wise (1987b, p. 1(1) describe the Deal Member ... ·111 outcrop.c.as a slightly gluuconiuc, clayey. fine quartz sand to clayey sandy silt unit. Downdip it var-ies, from a slightly sandy, clayey silt to a silty clay. Dcwndip. the Deal replace'> lhe FarmingJalt' Member and the ovcr.ying lower Squankum Member of the Shark River Formation (Olsson and Wise. 1987b). The Toms River wu-, designated rhe upper member of the Shark River Formation by Enright (1969) who recognized the similarity in lithology and >;tratigraphic position i:letween the Piney Point Formation anu the Sh"rk River. The~e relationships point to the Deal as an appropriate, formally recognized, fine.grained downdip subsurface .strati2rapllic unit for use in Delaware, equiv;\lent all or in pan \0 the coarser-glaiu<:J Vincentown. Manasquan, Shark River, and Piney Point formations. Figure... 5 and 6 show the facies relationships between the Deal and equivalent units. In Figur~ 5, the gamma-ray log sigllalures of the Shark River of the Clayton, New Jersey, core hoI>: alld Gd33-0~ are similar. Tne signatures of the Vincentown-Manasquan of the rormer appeur to be 11\0re n,arly simi lor to lhal of the fincr-gr:.lincJ De;d lhan to the sandy correlative interval in Gd.l3-04, a facies change along strike noled previously hgure £, il!uSff;.l.h.;~ Paleogene grov.th faulting postulated hy Benson (1994) in ordc:r to account for the downdip increase in thickness of Ihe Shark River, Deal, und Piney Point tormaliollS. The expanded stratigmphic SeelK)n of the Shark River on the downlhrown ,ide of the fault betwcen Hc42-1~ and Hc44-08 is illustrated by the illcrc:l.~ed thic/,:18

L

_ ness between the top of the Manasquan Formation and the log marker shown as a dash-dol-dot-dot line in Figure 6. The growth tnult is verified by the foraminiferal data from IIc.,14-0K that indicates thut at total depth the sediments arc still of early Eocene age based on the presence of Acarinina />U/l/',-,>oki, A. hraedermanni, Globigcrina ttnapena, and JflJl'iJ,~"\'cl/a

Nanjemoy Formation for the lower Eocene but possibly al ..o lower middle Eocene through calcareous nannofossil Zone NPI4. and Piney Point I'dI' the remainder of the middle Eocene section (including the fine-grained Deal portion). They stme. however, that other formational names or e\'t:'JI new one" tor ..orne of the lithologic units in Drlaware may be more appropriate in the future, Their assignment of Maryland ;l1ld Virginia formation names to the section they studied ill .1<:\2.-04 seems to be based more on their age determinations rhun on any attempt a\ gc:ophysiL'al log correlation as I have done in this study. Also, [hey applied those names without thorough acknowledgment of precedence of stratigraphic nomenclatural usage in Delaware. ln the Miocene section, huth the Kirkwood in the Clayton, New Jersey, core hole and the Calvert in Gd1.1-04 show similar gamma-ray log signatures (Fig. 5), They probahl,\' represent the samc lithostratigraphic unit, but the name .. of the unit have precedence in their respective states. The Cohansey Formation or New Jersey rCluyt.m core hole. Fig. 5) is absent in Delaware, presumably hy erosion that removed it prior to the deposition of Quatcrnary sediments. in the Calvert Formation of Delaware, correlation of the Cheswold and Frederica sands and rcccgnuion of the basal glauconitic sand (Figs. 5 and 6) are after Benson (1993). Figure 7 shows the correlation or the post-Pow mar stratigraphic units and the degree of their erosional removal between Je32-04 to Just north of the Chesapeake and Delaware (C & Dr Canal. The most extensive studies nf the Cretaceous outcrops along the Canal banks were h~ Carter (19.'1) and Groot et al. (1954) who applied names of New Jcr ..cv stratigraphic units. The unit names recognized now at the Canal are those of Pickett (1970), Owens ct al. (1970). and Houlik et al. (198:\). These later ...tudics mainly agree with Carter» interpretation. The geophysical log signatures of the outcropping units are shown for hen-hole Eb23-22 located just north of the Deep Cut of the Canal where upper Merchantville, Englishtown. Marshalltown, and ~l thin layer of the lowermost Mount Laurel formations are exposed (Pickett, 19Rh The geophysical logs both north and south of the Canal match the representative logs published by Houlik et al. (19XJ) for the Upper Cretaceous strata at and near the Canal. The major change in the Upper Cretaceous stratigraphic units shown in Figure 7 i.. the approximately tenfold updip decrease in thickn e s .. or disap pe ar ance of the Mug.uhy Formation. I interpret the updip thinning of the formation by (I) landward onlup (arrows in Figure 7) of the eroded surface developed on the Potomac Formation by the transgressing marginal marine Magothy deposits and (2) the erosional removal ~)f the predominantly silty upprr hL'd" or the entire formation from Fb15-08 northward The thicker Magothy section of ldl1-26 probably reflects additional accommodation spacL~ provided by erosional relict' or' the Potomac surface, as indicated diagrammatically in Figure 6. The micaceous and glauconitic vilts and sands of the Merchantville, the coarsening-upward sands of the Englishtown, and the highly glauconitic sands and silts of the Marshalltown formations can he identified by their signatures on mnxt or lhe geophysical Illgs in Figure 7. Where thc Englishtown becomes predominantly silly between the Canal and GdJ]·04. il~ characteristic upward-coarsening log signa-

(1('111111: the Horncrsrcwn Formation (carly

Paleocene) is at the same approxnnare depth (400 fl) in Hc42-12 only about one mile updtp on the upthrown side of the fault. The tucirs change from the Vinc cntownManasquan-Shark River updip to the Deal down the depositiona! dip likely occurs in association with the growth fault. The dashed line within the Deal in Figures 5-7 correlates geophysical log markers that are at or ncar the boundary between the Manasquan and Shark River equivalent sectinns: It correlates the base of hip/Pill' NPI4, which occurs at the base of the Shark River in Nrw Jersey, between the Clayton core hole and Je32-04. • The lowermost Vincentown rcr.rins a relatively coarse geophysical fog signature in ld:jl-2o. KbY2-01, and to somc extent in Je32-04, whereas the upper pan of the formation in Gd33-04, Hc2..J-04. and Hc42-12 grades downdip into the finer-grained l)c:II (Fig, 11). Olsson and Wise (19i-S7a) note that in the suhsurfaco Coastal Plain of New .lcrvcy. Ihe Vincentown gradcs into a quartzose silt facies that muy have been deposited ax r',u seaward as Deep Sea Drilling Project 'DSDP) site 605 located Oil the upper continental sl<1p~. Also shown in Figures 5 and (, is the facies relationship between the upper Deal and lower Piney Point. The Piney Point Formation thins up the vmn-tural dip as it fines into tilt:' Deal lithology and also hy rrovicnal truncation. The other fault shown in Figure h i.. al-,o probably a growth fault to account for some if not all ,II' the increased thickness of the Deal-Piney Point in JcJ2-04 compared with that of Kb32-0 I :lna Id.~ I-:!t), In Delaware. the Piney Point uttuins its maximum known thickness in the Dover lIf"a as rxcrnplified by Jd2-0·t The fault may be a boundary fault that defines a depositilln;t! trough that was active during Piney Point time. If ..0 it 1ll;IY trend parallel to the axis 01 the Piney Point depocentcr that continues northeastward from the Dover area into Gloucecrer County, New Jersey. The depocenter axis defines the depovitiunal trend of the southern of two major areas of Piney Point xand accumulation in New Jersey as shown by Zapec -u (I 9R9, PI. 21). The approximntef y north-south orientations of the cross sections of hgurcs ",-7 in Delaware are not coincident with the depocenter lIXIS tdcnosirtonal dip) of the Piney Point sands. This relation ..hip explains what appears to be coarsening of the sedmu.ms down the depositional dip, which in this case is apparent dip. from the Deal to Piney Point lithologies shown in the cross sections of Figures 5·7. whereas the fining of the Vincentown-Manasquan sands mtc the Deal lithology occurs down the true depositional dip which is more nearly parallel to the orirutanon of the cross section ... Bybell et al. (1995) in their paper on the Cenozoic GJ1GlreOUS nannofossil biostratigraphy of Je32-04 notc that the U. S. Geological Survey Joes not use the name "Deal." For the purposes of their paper they cho-e to usc only the stratigraphK units from the Maryland and Virginia region for Je32-04: thl' Brightseat Formation for th,: hl\\a P;11eocene sectioll. the Aqula Formation for the tipper Paleocene. the

19

(llJ85) in establishing their allmlriltigraphy, and the revised biostratigraphic and chronostratigraphic information reported in this Bulletin requires slight revision of rh cir allosrrntigraphy for the borehole as shown in Figure ().

ture is not well developed, hUI this feature reappears downdip and is best developed in Je32-U4. The Marshalltown is recognixed by its high gamma-ray response just below the overlying Mount Laurel formation. The Mourn Laurel is readily idenfifinble :IS a predominantly "andy unit that becomes silty downdip near Je32-l)4, It is recognized on logs between the high gamma-ray responses of the Marshalltown below and the: Navesink Formation above it.

LITHOSTRATIGRAPHY OF Jd2-04 Rasmussen et ul. {. I ()58) first published on JeJ2-04 shody after it was drilled in I ()57. They produced a composite geologic and lithologic log (their Table 4) which they based on the geologists field log, drillers' log, sand log, sample and core descriptions, electrical and gamma-ray logs, and preliminary microfossil investigation. They gave a straligraphic interpretation of the log and cite their Plate I, prepared hy 1\. J. Dcpmcn and A. Thomas, which shows the composite log compared to the gcophysual logs. The revision or their stratigraphic interpretation hy Jordan (1962) and the later lithostratigraphy of Benson et al. (llJg5) arc shown in Figure 9. The lithoxtratigraphy of Je32-04 in this Bulletin is based on the results of the hiostratigraphy and chronovrratigraphy. mineralogy. and subsurface stratigraphic correlation chaptLTs discussed previou-dy and incorpurares the data presented by Benson et al. (1<,):'\5). Borehole depths of

Comparisons with Other Strattgraphtes Figures 8 and 9 show comparisons of the: stratigraphy presented in this Bulletin with other stratigraphie" discussed ahdve, that have been applied to thc poet-Potomac Cretaceous-Tertiary section or central Delaware as exemplified by boreholes Od33-0..;t updip and Jd2-04 downdip. Also included, hut without discussion. arc the current subsurface lithostratigraphy or Maryland (Hansen, 1'J74, !()92, 1<)94), which I have correlated by geophysical logs to Gd3J-04 (Fig. X), and lh~ stratigraphie p'lsitions lif the offshore-onshore alloformanons defined by Pong and Ward (1993) for the mid-Atlantic continental margin. Poag and ward (1995) included Je52-04 data frurn Benson et al.

I Gd33--04

DEl.AW~~~_

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Figure 8. Luttostratigraphy nf Gd33-04 compared with other struugruphics.

20

l

l

_ the lithostratigraphic boundaries determined from IhG k3204 geophysical logs are given in Tuhle 2: mo-t of the boundaries correspond to lithologic breaks noted on the composite log summarized in Plate 1 of Rasmussen ct al. (IYSg). Data on sediment textures, principal minerals from point counts of thin sections, and non-upaquc heavy minerals are presented for Je32-04 by Benson <'I :11. (lygS, PI. 1). With few exceptions, only every other sample was analyzed: therefore, the interval between samples is about 1819 ft. with such J wide spacing of samples, the heavy mineral and point-count data reported below are insufficient to completely characterize each of the lithostratigraphic units recognized in this Bulletin, particularly the thin ones. The four principal minerals identified by point counts of thin sections arc quartz, glauconite, matrix, and shell calcite. As matrix is the principal component of more than 60 percent of the: samples. Spoljaric (1988) determined the clay and clay-size mineral composition of evcry sample (every 10 ft) from Je32-04 by x-ray diffractometer studies of samples prepared to yield preferred orientation of platy minerals. and those results are summarized below for each lithnstrungraphic unit. That study precluded identification of most of

TABLE 2 Borehole depths of luhuxtratigraphic boundaries. Jc32-04 Lithostratigraphic unit

Depth to base (ttl

Quaternary deposits

"

Calvert Formation Piney Point Formation

3'0 584

Deal Formatlon

894

Vincentown Formation

950

Hornerstown Formation

9B2

Navesink Formation Mount Laurel Formation

t003 1072 1108 1167 1265 1370 BelowTD

Marshalltown Formation Englishtown Formation Merchantville Formation Magotlly Formation Potomac Formation

tile non-platy minerals of the silt-clay matrix: Spoljaric. in a

previous chapter of this Bulletin, presents those dura in Figure 4 and summarizes that mineralogy for each lithostratigraphic unit of Je32-04.

ALLO_ ,"'S STUDY

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Figure 9. Lithostratigraphy or Jd2-0.:l compared with other stnuiguphies. 21

''''DI.O

UNNAMED

l !nfOT!mlllOll fwm tht' prcviousty pubhsttcd -tudies 0: J<:'32-04 is combined to characterize the lithostratigraphic units. Rasmussen cr <11. (1'.l)B) diu not pUJJish «ny mtonna-

nun on sedimentary or biogenic structures present in the split-spoon cores. It is not poss:hlc to study this aspect of the lithology now because very little core material remains. and there wert no archive halves preserved.

Potomac Formation The '12-ft qunrtzoxe sand-day sequence ot the Potomac Formation penetrated hy Je32-04 is
Formation and is marked by sharp breaks on the gcopbysicallog-, at 11;0 ft between the clay of the former and 1:'>;:1.,J1 sand ill' the latter. Non-opaque heavy minerals are dominatcd by staurolite, tourmaline. and zircon. Clay minerals pre-cnt arc kaolinite, illite. chlorite. and illitdsmectitc.

l\lagOlhy Formation The Maeothy Formation is primarily a marginai l1luri.1t' JcpO.lil th:l( marks rhe resumption of deposition artcr a major period of subaerial erosion and heralds the beginning of a maior marinl' trullsgression. The upper boundary of the formation at 1265 ft marks the top or a 1ignitic sand-vilt interval that occurs above the thick .sand ;(1 the base of r'ie formation, at the same position as that of Benson et al. (1985) The presence of lignite (indicated by woody material in Figure 2) suggesls :J nearshore III marginal marine deposit. In samples from cores 20(iYY and 207UO in the Magothy, Johan ,I Groot (written comrnun .. 198(-,) noted marine polynomorpbs (hystricll
McrehantviUc Formation The boundaries and description llf the Merehanhille Forma/ioll lre the' sam\' a, given by Benson et al. (1985). The formation is a fine-gmined unit consisting of Jark gray to greenish-grill. !lhwconitic. micaceous. f(lssiliferuu~, coarse "ilts "nd v~ry finc sanus. Tourmaline, garnet. and qauroJiIl' dominate the hcw} mineral . il1itc, chlorite. !!1:Juepllitel,mectik. and illilc/sm\'Uite.

Englishtown Formation The Englishtown is the same ::IS r'ie "Engli ..fuown" of Benson et al. (1985) and is Firmly established in Je32-04 by biostratigraphic and geophysical 10[.: cunclation from the Chesapeake and Delaware Canal area ( fig. 7). It shows a characteristic coarsening upward geophysical lng signature which. as discussed previously, is 11Il! wefl developed where the formation becomes predominantly silty updip hom Gd.\3-04 bm again reappear- in tnc vicinity of the Canal. Traced updip trom Je32-04, a silty interval apr.:a" ncar the top of the Fnghstuown and .'i[pamle." the bulk of the formation from a thinner upper sand in Id3 I -26. The formation thins updip. and al the Canal it is kss th .. 11 10 ft thid... in contrast with 60 fl III Jd2-04 (Fig. 7 J. Geophysical lo!! sig nut ure s indicate the con.ac t between the Merchantville and Englishtown is gradational in Jc32-04. and this feature i, characteristic of the other geopnysiu] log signatures or the Englishtown in Figure 7. At the Canal exposures Owens et at. (1970) describe the contact with the ulJderlyin~ Merchanrville Formation as sharp with a Lone of reworked sediment as much as 2 ft thick occurring locally along the bllWlll'H)'. At the Canal exposures Carter (1937) and Pickert (1970, 1997) indicate an unconformity between the Eng!i,htown and (lver)ying Marshalltown Formation; however, Groot d <11. (1954) and Owens et al. (1970) do not, although they describe a
Marshalltown Formation The fine-grained Marsj-aurown Pormarion show-, a rc.lat.velv high response on the gamma-my log of JeJ2-04 in the interval between the well-defined geophysical log signatures of the Engltshtllwn and M\)utlt Llun;l fOllll.ltions This retlecls the high glauconite conlent (>50 percent of sand fracrion) wjthin [hi~ greelli~h-gI1lY til gray, calcareou\, very fine sand and silt (hg. 1). The vcry fine to fillt ,illY s~nds at the Canal exposures of the fllHKltion aL~o ,1re highly glauconitic (Carter, 1937; Groot et a1. 1954; Owens ct al., 1970; Pickett, 1970. 19X7): Owen, et a1. (]970. Tk 3) report glauconite as a 1l1<1jor sand constitucnt (as mueh as 60 percent) in the upper part or the formation. The COl1l
l

_

~ (downdip calcareous facies of the Mount Laurel I. The contact is well-marked by ~I gamma-ray "kick" on the borehole logs between the Canal and 1.:32-04 (Fig. 7). The upper part (1072-1055 ft) of the "Marshalltown" formation of Benson et al. (1985) comprises the basal ,sand, and silts or the Mount Laurel Purmation of this report. Jordan (1962. PI. 2) designated the base of his unit A at 1090 :", within the Marshallrnwl1.

sand fraction), calcareous silt. Hertherine. glauconire/srocc. lire, ;t'ld illitdsmectite arc the d,t)' minerals present ill the unit. Tourmaline, staurolite, and garnet are the predominant heavy minerals with subordinate andnluxitu , dlloriroid. rutile, zircon, and epidote.

The non-opaque heavy mineral assemblage is dominat-

subsurface of the southern New Icr sev Coastal Plain. imIuding the Clayloll core huk, is the onty lower Paleocene (Danian) formation present. It is, as the Navesink, an unconformity-bounded unit. Its lithology in Je~2-04 j<; a greenishgray to d'Hk era)'. clayey' to fine-to-u-ediurn-sarulv, calcareous, glauconitic silt. It is slightly less glauconitic than the Navesink, Point counts of thin-scrtion varuplex indicatc (i(j80 percent matrix (Benson et al.. 1995, PI. \). In contrast ro the Navesink, mau ix i, dominated by quartz rather thun calcite (Fig. 41. Clay minerals present are chlorite, glauconite/smectite, and illite/smectite. Heavy minerals identified are tourmaline, staurolite, and garner ilS dominant with ,uhordinak zircon, ct.loritoid, undaluxitc, and epidote.

Hornerstown Formation The Homer-town Formation in Delaware and in the

ed by tourmaline, staurolite, and garnet with subordinuuchloritoid zircon, kyarute, and ruufc Clay minerals present are kaolinite, Illite, chlorite, and chlorite/smectite

Mount Laurel Formation The updip geophysical log signatures of the calcareous. fossiliferous, sparingly gl:lllconitic. fine 10 medium vands of the Mount Laurel Formation change as the unit JS traced downdip to ones that record the predominant ~alcarl'(lus ~i:1 facie, of the formation (ld3/-26 and Jd2-04 in Fig. ]I. Benson ct al. (1\l8S), placed their "Mur sn afho wn"? Pamoukeyr") contact at the base of a thin sand within thc Mount Laurel at lOSS n in .k':U-04. In Je32-04, silt-day matrix is the dominant constituent with glauconite and shell calcite subordinan- (B~mun et .d., 1985, PI. I). The matrix is mostly calcite (Spoljaric, th;~ Bulletin), comprising calcareous nannofossils. Rasmussen et al. (19'iR) dcscnhed the il1lcrval between 1001 and 1070 It, which corresponds 10 the Mount Laurel of this Bulletin, as comprising slightly glauconitic marl and chalk, although Benson d al. (19851 consider the calcareous silt-day to be too impure to he termed a chalk. This lithology is distinct from the overlying very glauconitic day unit Rasmussen "'I al. (1958) describe between 982 and 1001 ft (Navesink Formation of this Bullctinj. Fhc dominant non-opaque heavy minerab arc tourmaline, staurolite. garnet. and chlcritoid: andalusite. zircon. kyanite, and rutile are subordinate. Mount Laurel clay minerai, Me bcnhcrinc, gl;lucclllite/sme~~:ite,and ilFtl:'/smeclile.

Vincentown Formation As divc u sxc d pr e viou sly , the Vincentown and Manasquan glauconitic sands (Rancocas Formation of Jordan. 19(2) and the g);wconitlc sand:-; and silts of" the Shark River Formation (unit C of Jordan, 1962) that are present updip in Delaware grade downdip into calcareous k'ssilifcfOu, .,i/ts which I idenlify as the Deal Formation The lower part of the Vincentown, however, maintains a coarser, sandy to silry gcophysirnl lot': signature in ld.'1-16 :l!~d Kb32~OJ that I correlate to between 950 and ~l.)4 ft on the gamma-ray log of Je32-04 (rig. 6). Above 894 tt, the geephysical logs of Je32-04 indicate a homogcnt>lt<; .,ilt section typical
Navestnk Formation The Navesink Formation in Delaware and the NavesinkRed Bank (Ke 4 cycle) in the Clayton core hole of New Jersey are relatively thin, uncllnformity-boumJcd units (Fig, 5). They and the overlying Homerstown Formation of Danian age are very glallconitic silt units that give relatively high gamma-ray counts compared with the log responses from the Mount Laurel below and the Vincentown above. The Navesink and Hornersrown are glauconite sands in the sOUlhem New lersey Coastal Plain (OWCI1:-; ct al., 19':15) th"t become silt-dominated in Delaware, As discussed previously, Woodruff (199()) assigned the gamma-ray log respomes of tllese two very glauconitic tonnauons to the Hornerstown alone, but biostratigraphic data in support of geophysical log correlation establish the comil1uily of the tW(J as separate stratigraphic units traced from updip to downdip. The unconFonnable (Cre tacc oua/Tcrtiur y} c-ontact be t w c cn thl' Navesink [tlld Horners((lWn can u,ually be determined by geophysical log correlation, hut bi()';lra\igraphic dat:! may be necessary for verification. The N<-lvl:sink in Je32-04 is a dark green to greenishgray, clayey to fine-sandy, very glauconitic (>50 percent of

Deal Formation The Deal Formation in Je32-04 extends from 894 Ft to the base of the Piney Poinr r-ormauon JI 5x4 II. II i. a clayey, calcareous, shelly, glauconitic (lO-20 percent) silt. Its colors range from greenish-gray and gray-green to i:>mwnish-Er.1Y and light gray. It i<; rich in calcareous and siliceous microl'ossils lFig. 2). The matrix mineralogy shows a high calcite compl"'nent (Fig.. 4), except in lhe lower part of the fornullion which is within the calcite dissolution interval beLwl:l:lI 909 and 847 ft discussed previollsly. The !iU;ology is consistent with tll;]t of the IO\\eI" 10 midJle 23

thr. reworked Piney Point and basal Calvert Formation is actually of early Miocene age. r now recognize r he "reworked Piney Point" as the busal glauconitic uni: of sand and s;1t of the Calvert Formation which IS trace ahle downdip to borehole Oh25-02 near Lewes (Fig. I) where :1 is abodl2()O It thick (Benson, 1<,1')0, 1\19J, 19(4), With this new knowledge, I restrict the Piney Poinl in Je32-n4 to the rruddlc Eocene, from 5g4 ft to the unconformity at the base (If the lower M iocenc secuor. at 370 ft. The geophysical log signature 01 the Piney Point in Je.12-04 shows <:IS u sli~htly roar-a-ning-upward sand, which is also indicated by t'te textural duta of Benson et al. (l '.185, PI. 1) It'' lill]p)ogy i, a brigl» green. fine to medium, gfuuccmitic (20-40 percent), shclly sand, more clayey ncar the htl . ,e where t i., in gradational contact witb the vihy [(I clayey Deal Formation. Quartz content increases upward at the expense ,)1' g"-wconite (BelJ.';(>ll cr a!., Jl.l8:). Silli1lJanik and garnet become important constituents of the nonopaque lu-uv y mineral as~embbi!e ~/ong with domin.1nt staurolite and tourmaline. Andnlusite decreases and is suburdmare alor.g With. lLyanite. epidote, and zircon Clay nuneruls identified arc glauconite/smectite and kaolinite.

l-ocenc Deal as descrihcd from the cubsurfuce of New .ler cey hy Olsson and Wise (I n7a. h). I include upper Paleocene sL'dimc;]ts above the Vincentown of .11"12-04 in the Deal as the lithology detcr-nincd from the sediment L<>rcs J"cs I1\>1 diller 1l1;lrkcdly 1"r"l11 thur 01" the Eocene oart. In describing their PaTllunkey(?) Formation (I ()j5-Si:'lS It in .k3]-O..J.), which the Dc'al is ;lsignifluHlt par;. Benson et 'II, (I <,IX) surnmurizc ils lithokJf-y as chaructcr.zcd hy fine tcxrure-, Iud p,eSenl'e 0:' gbuconile, AHhllUg1 lilhobgic homopencitv is u dominant uspccr. they recognized tour suhJj,isions from geophysicd lug sigm.ltmc." which wendescribed orevionsly. The percent). Also, their textural data indicate the median grain size IS mostly tn the d;r)' rang", for tnt" Iowa Eocene (Manasquan equivalent) part of the Deal whereas it i,s in the. silt range for the lIpper l'JleOlC/1t' lVin,·en\(\\....-n cqnivale nt. in p.nu and middle Eocene (Shark River equivalent) parte. Geophysicallog sign.IIVre'." tor lhe middle Eocene l';iJ"\S orrhc Deal ill bureholes Kb32-0 I and IdJ 1-26 (Fig. 6) indicate coarser-grained secliom than Ihe Illlderlyill!-, lower ~()cenc pOlrls. The lower and middle Eocene sections ot the Deal arc the dew.ndip .:quiv
or

I

I I

I

I

I,

n.

Calvert Formation The only revision to the Calvert Fcn'mutiun of Benson et a!' (lQ8S) is the inclusion of the "reworked Piney Point" ar trs base ex discussed above. Two sandy intervals other than the basal glauconitic sand are the Cheswold and Frederica sands tFig. 5 and 61. Parts of these intervals tunclion a-, important aquifers nnd were noted a c such by \{asmu~sen et al. (l95H). The ha,,,l gl~lUconitie ,,:ind (I f1-20 percent glauconite) is mediuJll to ~oarst:, llliglit to dark green, :tnJ shelly. Heavy miUCf;"l)-; are similar to thn-e the> upper Pim:)' Point ao.; lhat formation \vas the likely ,ource 1"01' the hulk or the basal C
Dr

Pine.y Point formalion I:knsun.,;{ al. (/4h5j iududcc in th~'ir Pilley P,>inl Forma:ion "I" Je12-04 a 34-~'t section of giauconitie sand Ihl.:Y iJl.:l11i fin! a~ rew,lrked Pilley Poill[ (If O/(gocenc('?) ilge that unconforrnably overlies ~he middle E(lI:ene seetioll. i\~ Jiscussed [In.:\'iou~ly, their Oligocellc(?1 se<.:tion corrrpri"rng

24

l

_ CONCLUSIONS The stratigraphy of the poet-Potomac Crcl:IL"CPllS and Tertiary rocks of the Atlantic Coastal Plum or central Delaware integrates new and reinterpreted data from boreholes in Delaware and nemby N:w Jersey. The lithostratigraphy, bicsnutigraphy. and chronostratigraphy of the Creraccous-Tcrnary section of IC.Sl wei) Jd::'-O..j. ar the Dover Air Force Hase reported by Benson et at. (J9W'i) are revised herein on the bases of gct1physical log corrcln,iOl~.'; lit: .... blostraligraphic data on calcareous nannofosxils.. palynomorphs, and dinoflagellates from the core samples and reinterpretation of the bio"ra!i~mphjc datil of Henson ct al. (19f!5J on planktic foraminifera. radiolarians. and diatoms: uno mineralogy of the: non-clay-minerul component of ilK silt-clay matrix of the split-spoon core sample- reported here, Recently published biostratigraphic and lithologic data from the conim/ou.\ly cored Clayton, New Jersey, borehofc support geophysical log correlation to Delaware boreholes Gd:B-04 at Deu kyne ville and dowl/dip to J~'J2-(j-J.. Btostrangraptuc and litholugic data from the Delaware boreholes confirm the peophysicul log correlations. Dare from the Clayton and Dover corehole-, serve ,\~ the primary COIltrol for correlation of borehole geophysi('*ll lops between the ChesLlpeake and Delaware Canal urea and the nova area. The names of most of the .lc32-U4 lithostratigraphic units of Benson et ,\1. (19l'.'i) urc rennncd, but the boundaries of some have been revised. The Potomac Formation is as reponed by those authors, and its age is estnblished hy palynology as late Cenomanian-early 'I'uroniun . Palynomorphs and calcareous nannorossfts esrablich thu Santonian 'lge of the Magothy Formation which gradeupward into the Merchantville Formation. Through landward onlap 011 the eroded »urfucc or the POlnmm· ;JnJ b;. erosional removal of its upper beds, the transgressing marginal marine deposits of the Maguthy decrease tenfold in thicknes." between k32-04 and the Canal area where the formation IS absent in places. The Santonian/Campanian fwundary in .k:"2-04, idemified hy cttk:(rCDUs l1ann,l('ossils, o\:curs within the lower part or" the Merchalllville. Calcareous nannofossil~ establish the Camranian age of the rest of the Merch:.\Iltvillc, and the Englishtown, Marshnlltowll. and Mount Laurel fOf1naliO:ls und the M:I;j,lrichtian ,tge 0: the Navesink FOlmatioll, illl of which are correlated \0 Jd2-04 from updip Delaware horehoks 'lIld the Claylon, Ne . . . . .lcr.sey, ;;ore hole III upJip borehole Gd33 (Jr!, Jord:j11'S (19(',2. PI. I) inform
Vincentown l-ormarion. The upper (upper Purcccerc-tower Eocene) pan or his Rancocas Formation and his unit C between his Rancocas and 11i<: Ch~~'lpeal..": Grollp arc iuellli ficd as the Manasquan and Shark River formations, rcspcctivelv. hy correlation from the Clayton. New Jersey, core hojc. Usage of the Maryland name rs:"11Jemoy hy Pickell und Spoljaric (1971) for Jordan's (1962) unit C is rejected uhhough th:ll unil c{lrrehttc.~ with (he M:lryfand unit. vlajor thirkncsv and facies changes. both along strike and downdip. occur within the P~lblgenes:cljon lhal UIl<,;OIlforrnably overlies the llorncrstown Formation. The updip Vincentown-Manasquan-Shark River section becomes rinergrained and more nearly uomcgcneous ucwn.up auoss ;J growth fault postulated to account for an abrupt, nearly threefold increase ill lhickncs,\ of the posl-Hol'lwrstO\\1l secnon. The Deal Formation of New Jersey is introduced for this downdip. llpptT Paleocene-middle Eocene fine-grained section we identify between the Vincentown and Piney Point formations in Je-:D-04 It rcpluccs most of the Pulccgene part of the Pamunkey(,!) Formation or Benson ct al. (198S) who assigned the name 10 replace jordan's (1962. PI 2) informal unit A. Unit A and Ill: P;lmunkeyl':} al.'o inc-luded upper111()'! Cretaceous strata, which are now assigned lo the Mount Laure' and Navesink Formations. Till' Deal Formation graJes beth vertically and laterally downdip mto the overlying middle Eocene gl'lUCOJ1itic samh ('f the Pilley Point Formation Th... Piney I'oru thins updip stratigrapnically and by erosional rruncaucn indicated by the uncontcrruity between the middle hli"t'nt' :rnd lower Miocene sections. In Jd2-D4. Benson et al. (l9i<.."i) included a '4-ft -ccnon of glaucorutic :::-04 COlT ~J.ll1plcs. AlLhOllgn quartl: and ealcir<: are tile most common· ly occurring and abundant mineral.... many other miner;tl, h:l"e been iJcn(ifieJ, some of whi~·h have 110t b":cll known previously i;l Delaware Ze()lill'~ replll1ed in thi~ ,\!Udy ,wJ thu~e di~l·US~CJ by SpolJaric (1,)8K) parlH.;uJarly from lhe Pa!tou;ue-Eun:nc section teslify to exten~ive vokanislll Cel1ain mineraLs :lllJ mineral :lsS(}Cialions (jarosite. alunite, hematile, kaolinite, talc) arc ~uggcslive 'lf chemical aClivity by hydrnthcrm:11 sohltIO)J.~. At prCSenl, howcver. there l~ ]U (lther linn, direr! cvidence lhal such fluids existed in the are,l, hUI the possibility should notlw lotally &sr:g-ilnJeJ. The uppernHlst Paleocene carbonate disso1L:tioll illlerval noted hy Gibson L'I a!. (1
r.rphy. in Snelling, N. 1. ed . The Chmnolugy of the geological record: Geological Society pI London Memoir 10, p- 141-198.

reported by those authors was not observed in Jc3~-{)4. Gibson ct ul. (199]) ,~\.Igge~t {hill tho kaolinite increase may he a local record of u major global climate warming event that not only led to hi~h biogenic silica accumulations in oceanic sediments but ~llsn brought about intensive weathering on land that resulted ill formation of large amounts 01 kaolinite In the Delaware Coastal Plain. the evidence in the scdrmenr-, for ro~~ible regional volcanism during thi-, time could he uvsocinred with this global event. a lime of significant u-ctonic pt.tre reorganization. The results of this and earlier studies provide a reasonably complete understanding of the part of the geologic history of the central Delaware Coastal Plain represented hy the post-Potomac Cretaceous-Ternary section of Je32-04 and its correlatives in updip boreholes and outcrops. The study should provide a ha~i~ for analysis of the remainder of the Coastal Plain section und lead ro a subsurface stratierapbic framework that will he Important in future investigali'lIls of the geology and hydrology of Delaware.•

Berggren. W. A., Kent. D. V.. and van Couveringc J. A., 1985b, The Neogene: Part 2, Neogene geochronology and chronos. nutlgraphy. in Snelling, N . .I., ed., The chronology of the geological record: Geolngical Society of London Memoir 10. p211-2.50 Berggren, \V. :\. Kern. D. Y" Swisher, C. C.,III, and Aubry. M.-P, 19<,)5, A revi-cd Cenozoic geochronology and rhronustratigraphy. in Bnggr~n, W, A., Kent, D, Y., Aubry, M .p and Hardenbol. Jan. ~lk, Geochronology, time scales and global stratigraphic correlation- SEPM (Sod cry for Sedimentary (,c"k'gy) Special Publication N'I. '14. r I ~4-212. Btatt. H,. Middleton, G., and Murray. R .. 1972. Origin of Sedimentary Rocks: Englewood ('li\h. New Jersey, PrenticeHall. Inc, 634 p.

Blow, Vi. H .. 1979, The Cainozoic GI(}bigerinilb,:> vols.: Leiden. E. J. Brill. 1413 p. Bolli. H. M., ,;11<.1 Saunders. J, 8.. [985, Oligocene to Holocene low latitude planktic Iorurouutcra, in Bolli, H. M., Saunders. J, B.. and Perch-Niebea, K, ~d,;" Plankton Stratigraphy: Camhridge. United Kingdom. Cambridge University Press, p. 155-2o~

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