Post-glacial fossils from Long Island Sound off West Haven, Connecticut

26 Pages·2001·10.6 MB·English

by  Karl M Waagé

Postilla
Number 225
8 January 2001
Post-glacial fossils from Long Island Sound
offWest Haven, Connecticut
Karl M.Waage
CopelandMacClintock
Leo Hickey
J.
(Received6 October 1999; revisedandaccepted 19April2000)
Thispaper is dedicatedto KarlWaage, Less numerous,noncalcareous, undated
who diedon October 18, 1999, 10 days mudclasts areprobablyyoungerand
after proofreadingthe finisheddraft. contain invertebrates suggestiveoflifein a
protectedlagoon. Incorporatedpeatlayers
Abstract indicatethat the sedimentsaccumulated
in aprotected,shallowwater,lowenergy,
In 1957,Holocene marineconcretions subtidal orintertidal environment.
and mud clasts containingpost-glacial
fossils ofmarine invertebrates andland Keywords
plantswere dredged from oft^shoreat
Prospect Beach,West Haven,Connecticut, Climate,EastHaven,marinefauna,flora,
as part ofa localbeach sand-fill project. Holocene,invertebrates.NewHavenHarbor,
Indurated,calcareous concretions,dated terrestrial plants,post-Pleistocene,Prospect
at4530 to 5330BP,yieldedarich fauna, Beach,radiocarbon dating,globalchange.
similarto today's,ofbivalves (dominated
byArgopecten andAnomia),gastropods Introduction
(dominatedbyBittium andNassarius),
andcrustaceans,indicatingaccumulation Concretions anduncemented mudclasts,
in a shallow,subtidalenvironment bothwith marine invertebratesandland
perhaps0.3 to 2 m (1 to 6 ft) belowmean plants,werefound inbeach litterat
lowwater. Megafloralplantremains Prospect Beach,West Haven,NewHaven
—
belongingto eighttaxa includingFagus County,Connecticut (lat 41°14'46"N,
grandifolia (Americanbeech),two species long72°58'00"W),on thewestside of
ofBetula (birch), Carya d. C.glabra NewHaven Harbor. Most ofthearea
(pignuthickory),andPicea cfP. rubens (Figure 1) is a 1.6-km-longpublicbeach
—
(red spruce) indicatethepresence ofa alongOceanAvenuebetween Ivyand
mixed hardwoodforest growing under South Streets.Whatwas originallya
climaticconditionssimilarto,orat most coarse shinglebeachwas made into a
onlyslightlycoolerthan,those oftoday. bathingbeach byadditionofsand fillin
Postilla225 Post-glacial fossils from Long Island
Sound offWest Haven, Connecticut
Figure 1
Concretions and mud clasts from Prospect Beach. A, index map; B, detailed map; C, depth
contours (ftbelowMLW) ofborrowareabasedonprofiles 14to38ofVesper (1961).Coarsedots,
concentrated concretions; fine dots, scattered. Mud clasts between groins 1 and 9. Groins and
borrow area modified from Vesper (1961). MHW and MLW modified from U.S. Coast and
GeodeticSurveyChart218 (Connecticut 1964).HR,HousatonicRiver;LP,LighthousePoint;MH,
MilfordHarbor;NH,NewHavenHarbor;PB,ProspectBeach.
Post-glacial fossils from Long Island Postilla225
Sound offWest Haven, Connecticut
1957 underacooperativefederaland state thenodularconcretionscontainingonlya
programto improve andstabilizeshore- fewshells orshell fragments.Theconcre-
lineareasbetween NewHaven Harbor tions occurin avarietyofshapes andsizes
andthe Housatonic River (USAGE 1953). and contain a faunathatvaries in abun-
Presenceofthe concretionswas first dance andspeciescontent (Figures 2-5).
noticedbyChristopherSelfofNew The macrofossilsarepredominantly
Haven,whobroughtone (Figure2B) to molluskshellswithArgopecten irradians
theYale PeabodyMuseum for identifica- (Lamarck),AnomiasimplexOrbigny,
tion in the fall of1961 (Waage 1962). A Crassostrea virginica (Gmelin),Laevi-
collection of 1000 concretions (including cardium mortoni (Conrad),Mercenaria
cemented shell aggregates) and46 mud mercenaria (Linnaeus),Nassariusobsoletus
clastswas subsequentlyaccumulated (Say),andBittium alternatum (Say) the
betweenthen and 1968. Renewed interest dominantspecies.Looseshells collected
in this collectionprompted re-examina- alongwith the concretionarymaterial in
tion ofthe intertidalzoneatProspect thebeachlitterweredistinguished as
Beach in the springof 1999,withthe "fossils"with certaintyonlyifpatches or
search concentratedbetween groins 1 bitsofthe thin coatingofconcretionary
and 4 andextendingdown to 0.3 mbelow matterwerefoundadheringto them. But
mean lowwater (MLW),butno addi- where theconcretionswerecommon,
tional specimenswere found.This report, loose,dull brownish-grayvalvesof
based on an unpublished 1968 manu- Argopecten, and someMercenaria valves
scriptbyWaage,hasbeen completedand with ayellowish-graytint,were also
significantlyenhancedbyMacClintock common andprobablyfossil; locallythese
andHickey.Alltheinvertebratesarecata- constitutedasmuch as 3% or4% ofthe
logued anddeposited in theDivision of molluscanbeachlitter.About 25 speci-
Invertebrate Paleontology, Peabody mens ofeach ofthesetwo generawere
Museum ofNatural History,Yale Univer- foundwith bothvalves in place and
sity (YPM).Associatedlandplants are concretionarymaterial onlyin the
catalogued usingDivision ofPaleobotany internal cavity.
(YPMPB) numbersbuthoused in the The concretions consist ofsand and
invertebrate collections.Exceptforthe siltysand (Wentworth Scale) cemented
plants,all figuredspecimensandthose bymicrocrystalline calcite.The sand is
mentionedbynumberarehypotypes. angularandpoorlysorted,with irregular
patches ofmedium and coarsegrains
ConcretionsandMudClasts occurring in a finer-grained field. Occa-
sional granules and even pebbles up to
The concretionsoccuras irregular,ovoid, 4 cm in diameter are present in someof
nodular masses ofgray,calcareoussand- the concretions (Figure 2A). The matrix
stonerangingfrom 3 to 25 cm in length. ofthe concretionarysandstoneconsists
Clustersofshellsheldtogetherbyconcre- ofcalcite admixedwith asmall amount of
tionarycement are more common than allogenic clay. Quartz is the principal
Postilla225 Post-glacial fossils from Long Island
Sound offWest Haven, Connecticut
—
Post-glacial fossils from Long Island Postilla225
Sound offWest Haven, Connecticut
constituent ofthe sand,and feldspars, similarin compositiontothecemented
weatheredtovaryingdegrees,arethe next sandysiltandmaybetheparentsediment
most common group ofminerals. inwhich theconcretionsformed.When
Muscovite isthe onlyother major washed,ityieldsverylittleclayandits
constituent,but avarietyofaccessory stickinessisapparentlyduelargelyto
minerals are present. Coarseto fine- gelatinousorganicmatter.Organicsandy
grained organic remains also occur, siltiscommon inthe soundtodayand
dominatedbymegascopic plant frag- possiblythesoft materialon theconcre-
ments,butalso includingpollen, spores, tionaryshell massesissecondarilyderived,
diatoms, foraminifera, insects, and shell butboth itsdegreeofcompactionand
fragments. Macrofauna, in addition to calcareouscontentfavoritsbeingthe
moUusks, includes mantis shrimps,crabs, primarysediment. Beddingisnotgener-
lobsters,barnacles,bryozoa, serpulid allyvisible in theconcretions. However,
—
worm tubes,boringsponges, and fishes. four do showbedding one ofthese has
Macrofloraincludeswood,nuts,cones coarse material occurringin a cross-
andleaves. Someofthesmall concretions laminated lens.
contain onlybits ofarthropod shell or The less irregularconcretionary
—
plant fragments. nodules thosewith fewershells
Thecalciticnatureofthecementwas commonlyshowsome effectsofsurf-wear
establishedbyX-raydiffraction analysis. and consist onlyoftheharderconcre-
Concretionarysand inmanyoftheshell tionarymaterial.All ofthemhavealight
aggregatesshowsagradationfromareas gray,softouterrindofweatheredmaterial
ofhardcementation,wherethematerial fromwhich most,but not all,ofthe
iscompactanddarkbluish-gray,to friable calcitehasbeen leached.Thisrind,
materialthatis mediumto lightgray.This rangingin thickness from 1 to 3 mm,
uncemented,calcareous,siltysand issticky probablyformedafterthe materialwas
whenwet,andwasfound adheringin deposited on thebeach,with itsthickness
protectedareasofshell clustersonmany beingproportionalto thetimespent at
specimens.Thismaterialappearstobe thesurfaceexposedto air. MoUusksthat
Figure2
Bivalves. All from concretions. Bar scale 1 cm in all but I. Lighting from different directions.
A, Anomia-Argopecten concretion with 4.5 cm pebble, assemblage YPM 38762; B, Mercenaria
mercenaria in concretion found by Christopher Self, assemblage YPM 39092; C, M. mercenaria,
medial,posterior-obliqueviewofinnerfibrousand outerlamellarligamental layers,YPM 38811;
D-F,Argopecten irradians; D,all medium size,41 of69 shells exposed on concretion surfacehave
doublevalves,lotYPM39358;E,mixedsmalltolargeshells,irregularlyarranged,nonedouble,lot
YPM39153;F,mediumtolargeshells,sortedandnestedroughlybysizewithlargeroneonbottom,
nonedouble,lotYPM38976;G,Crassostreavirginka,clusterof12shells,mostdoubleandgrowing
from acommon center,lotYPM 39353; H,I,Laevicardium mortonidisplayingdarkto lightzones
correspondingrespectivelytocontactwithfreshconcretion (1),weatheredrind (2),andsediment
outsideofconcretion (3),YPM 39110;H,wholespecimen;I,detail,scale2 mm.
Postilla225 Post-glacial fossils from Long Island
Sound offWest Haven, Connecticut
Post-glacial fossils from Long Island Postilla225
Sound offWest Haven, Connecticut
in life hadwhiteorlight-coloredshells notinan abundanceorvarietycompa-
werealteredto adark,amber-brown after rabletothoseintheconcretions.Theyare
encasement inthe calcitic concretions. finergrainedthantheconcretions,unce-
Those shell partsthatwereoutsidethe mented,noncalcareous,and consistchiefly
concretion remainedlight. Leachingthat ofmicaceoussilt andfinesand,their
produced the rind ofthe concretions "muddiness"beingderivedchieflyfrom
caused thebleachingofthebrownish containedgelatinousorganicmatter.At
impregnation oftheshellsthatlaywithin least 18 ofthemexhibitbedding,seenboth
itbackto alightershadeclosertotheir from differencesingrainsizeandfrom
original color (Figure 2H,I,and an unfig- abundant flatpartingsofcarbonizedplant
uredMacoma balthica [Linnaeus],YPM material.All theshells arebleachedwhite,
200033). Coloris retained in some ofthe eventhoseenclosed in freshmatrix,and
Argopecten, even a fewwith red concentric lossofmuch oftheiroriginalcalcium
banding,but morehavebeen bleachedor carbonatehasleftmostoftheshells
turnedamediumtobrownish grayduring friable.Manyofthemudclastshaveno
exposureonthebeach. ManyAnomia rind. Inothersalightbrownrindranging
mm
retain theirlusterandyellowish color; upto 5.5 thickcompletelyencasesthe
others, although retainingtheirluster,are sedimentaryfragment.
altered to silver-grayorwhite. Ingeneral,
colordifferences from recent shells ofthe Distribution,SourceandAge
same species areperceptible but subtle.
Roundedgray,greenish-gray,and The concretions and mud clastswere
pinkish-brown mudclasts,generallyovoid foundonlyatProspectBeach,WestHaven
and rangingin length from 3 to 20 cm, (Figure 1).The concretionswere unevenly
m
occurred sparinglywith theconcretions in distributed alongsome 1050 (3500 ft)
thebeach litter.Theycontain shellsof ofshoreline.Allbut a fewofthe speci-
Argopecten andothermollusks,though menscollectedwere foundalongthe
Figure3
Bivalves and gastropods. A-L from concretions, M from mud clast. Bar scale 1 cm in all but N.
Lighting from different directions. A,B,two specimens ofCrassostrea virginica (1 and 2) growing
on shell oiArgopecten irradians (3), YPM 39343, 39351 and 39344, respectively; C,D, Aiwmia
simplex growing on shells of A. irradians; C, YPM 39355 and 39356, respectively; D,
Anomia-Argopectenconcretion,twoA.simplex(YPM39346below,YPM39347above)oninsideof
A. irradians shell (YPM 39348); E,Anomia concretion,A. simplexgrowing on other live or dead
YPM
Anomiashells(nestedones [1] probablygrewonliveshells),includesfourbyssalplugs(2),lot
39118 (includesallAnomiaspecimensinconcretion);F-H,Nassariusobsoletus;F,aperture,andG,
anterior,YPM 38882; H, detail, columella with one ridge,YPM 38890; I-K,N. vibex; I, aperture,
YPM 38707; J, anterior, thick outer lip, YPM 38706; K, detail, columella with two ridges, YPM
38794; L,N. trivittatus, flaUened shouldervisible even though penultimatewhori is mostlygone,
YPM 38738; M, Littorina irrorata, aperture, YPM 38608; N, Bittium alternatum, aperture, YPM
200427,scale 1 mm.
Postilla225 Post-glacial fossils from Long Island
Sound offWest Haven, Connecticut
Table 1
Radiocarbon dates (in ''^Cyears) ofmaterial fromthreecalcareousconcretionsdeterminedand
reportedbyStuiver (1969:566-567).
Laboratory
number Kindofsample Years BP Years BC
Y-1129 Argopecten irradiansshell 4600 ± 90 2650 ± 90
Y-1596 Carbonizedwoodandleaffragments 4530 ± 100 2580± 100
Y-1783 Calcareouscementofconcretions 53301100 3580± 100
m
350 (1200ft) ofshorelinebetween the Derivationbynaturalagencyisallbut
fourgroinson the south end ofthesand ruledoutbythelowprobabilitythatlocal
beachbetween South Streetand Baycrest storm-generatedcurrentscould attain
Drive. Search forthe materialwas enoughkinetic energyto cause submarine
extended eastward alongthecoastline erosion in a depositwhich,aswillbe
aroundNewHaven Harborto Lighthouse explained, is probablynotlessthan 6 m
MLW
PointandwestwardtoMilfordHarbor (20 ft) belowpresent anywhere in
without findinganytraceofthe concre- thevicinityofNewHaven Harbor.
tions,cemented shell clusters ormud However,because ofthe configuration of
clasts. Spot checks ofthebeachesbetween thesoundbottom andthe possibilitythat
Milford Harborand themouth ofthe storm erosion mayhaveoccurred along
Housatonic Riverwerealso unproductive. the edgeofthe flatextendingeastward out
Outcroppingpost-glacial marine from thevicinityofProspect Beach,the
depositshave notbeen found above the possibilityofnatural agencyexposingthe
intertidal zone in the LongIsland Sound sourcebed cannotbeeliminated.Never-
area. This includestheclayandoverlying theless,theconcretions onlycameto light
sanddepositsofthe Stiles ClayPit2 mi sincethesand fillwas added to Prospect
south oftheNorth Haven town center Beach in 1957. Between then and thedate
(Brown 1930).Themarinedeposits alllie ofthelastcollectionin 1968 no storms
belowsealevel,andthegradual rise ofsea attained hurricane intensityin the New
levelsincethe last glaciation has exceeded Haven area,noteven HurricaneDonna
anypost-glacialcrustal rebound south of on 12 September 1960 (Brumbach
southeastern Massachusetts (Flint 1965:137).Thus,though lesserstorms
1957:360).Apparently,theProspect Beach could havetransportedthe concretions
concretionscamefrompost-glacial andmud clastsinshore,theirhighlylocal-
marinesedimentsin thesound itself, izeddeposition onthesouthern halfof
eitherthrough natural orhuman agency. Prospect Beachmakes itseem most likely
Thecoincidenceoftheirlimited distribu- thattheywere derived from theartificial
tionwithanartificiallymadebeach fillingofthebeachdescribed below.
stronglyfavorsthelatterpossibility. The fill for Prospect Beachwas
Post-glacial fossils from Long Island Postilla225
Sound offWest Haven, Connecticut
removed from a nearshoreborrowareaby Connecticut,about 36km (23 mi) due
hydraulic pipelinedredgeintheearlypart eastofProspect Beach. Bloomand Stuiver
of 1957. Ninelarge-bouldergroinswere (1963:333) graphedthedatesanddepths
then builtto entrap the sand.A subse- ofradiocarbon-datedcoresamples from
—
quentstudyofthebehaviorofthe fill and coastalConnecticut chieflyfrom
borrowareawas madebyVesper (1961). beneath Hammock RiverMarsh at
—
Information onthe sourceofthe fill and Clinton to showtherateofcoastal
topographyoftheborrowarea is derived submergenceduringpost-glacialriseof
from thatreportand from thestudyby sealevel.Thesamplesweremostlyof
the U.S.ArmyCorps ofEngineers (1953). sedgepeatthataccumulatestodayinthe
Theborrowarea,lyingparallel to the landwardpartsofsaltmarshesand"in
beachbetweenthe projections ofLake estuariesupstream from thehigh-tide
Street on the south andArlington Street limitofsaltwater" (Bloom andStuiver
m
on the north,wasabout 250 (1000 ft) 1963:332).Theirdata,expressedinacurve
m
offshore andwas about 135 (450 ft) ofsubmergence,canbeusedto showthat
m
wideby600 (2000 ft) long (Figure 1). sedgepeatthataccumulatedbetween4000
m
Average depth ofdredgingwas 3.6 and 5000yearsago occurstodayatdepths
m
(14.5 ft) belowthesound bottom; the between4.4 and6 (15 and20ft) below
original depth ofthebottom overthe mean highwater (MHW).
m
borrowarearanged from about 1.2 to 3 Radiocarbon dates offrom 4530 to
(4 to 12 ft). ProfilesbyVesper (1961:5-6) 5330 BPwere obtained formaterial from
indicatethat thebaseofmostofthe threeoftheWest Haven calcareous
borrowareawasconsistentlyover6 m concretions (Table 1).Compactionof
(20 ft) belowMLW.Approximate sediment and the fact thattheWestHaven
contoursbased on these profiles showthat concretionscontain a subtidal fossil
the southwest end oftheborrowareawas assemblagewouldboth tend to increase
deepest,beinggenerallyover 7.4 m (25 ft) thisdepth figure. Ifsedge peat forms at or
andlocallyover8 m (27 ft) belowMLW. justabove MHW,adepth factorgreater
If,as seemslikely,theconcretionscame than the 1.9 m (6.4 ft) meantiderange for
from theborrowarea,theirconcentration the areawouldhavetobeaddedto derive
atthesouth end ofthebeach filland the estimateddepth forthe sourcebedof
scarcityatthenorthendsuggeststhat they the concretions. Usingthe Bloom and
mayhavebeenderivedfromsediments Stuiver (1963:333) submergence curvefor
m
reachedbythedredgeonlyinthedeeper 4600 BP and adding2.1 (7 ft) forbare
—
southwestendofthepit thatis,about adjustment to a subtidalenvironment
7.4 m (25 ft) ormorebelowpresent MLW. yields a depth figureof7.4m (25 ft)
Thepossibilitythattheconcretion source belowMHW,which is mostlikely
bedwas reachedonlyin thedeepersouth- minimal forthe sourcebedoftheWest
west endoftheborrowareaisalso Haven concretions.
supportedbyinformation onthedepthof The mud clasts, found uniformlyscat-
bedsofcomparableagefrom Clinton, teredbetween groins 1 and 9,wereprob-
10 Postilla225 Post-glacial fossils from Long Island
Sound offWest Haven, Connecticut
Table2
Listofanimalsidentifiedin Prospect Beach concretionsand mud clasts,arrangedbyquantityper
majorgroup.
Taxa Concretions Mudclasts
Bivalvia^
Argopecten irradians {Lamarck) 2614/120" 31/1
'
AnomiasimplexOrhi^ny 2093'' 9'-
—
Crassostrea virgimca {GmeVm) 124/29 /I
Laevicardium mortoni (Conrad) 114/24 11
—
Mercenaria mercenaria (Linnaeus) 75/36
—
Gemmagemma (Totten) 58"/29"
Modiolusdemissus (DiWwyn) 15 5
Ensisdirectus {Conrad) 7/2 —2
Tagelusdivisus {Spengler) 5/2 —
M/fl flrenan'aLinnaeus 4/1 —
Macomabalthica {Linnaeus) 1/1 —
Anadara transversa (Say) 3 —
Tellina agilisStimpson 2 —
Cyrtopleura costata (Linnaeus) —1 —
Indet.Teredinidae ^
Gastropoda
Bittium alternatum (Say) 681 6
Nassariusobsoletus (Say) 93 7
—
JV. vibex(Say) 24 —
N. trivittatus (Say) 2 —
Crepidula convexa Say 17
—
C./br«?'cato (Linnaeus) 1 —
Eupleura caudata (Say) 3 —
Busycon canaliculatum (Linnaeus) 2
—
Urosalpinxcinerea (Say) 2
Continued
^Singlevalvecounts,includingleftandrightvalves,aregiven first,
followedbydoublevalvecount,whereapplicable.
" Fifty-nineofthe 120 in two concretions.
'-Onlyleftvalvesand 73 isolatedbyssalplugscounted.
"Allbuttwoinonesmallconcretion.
^Manyin onepieceofwood.
^Unidentifiablewith orwithoutappendages,orisolatedclaws.
§Clustersorcolonies.