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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.