A new areoligeracean dinoflagellate from the Miocene of offshore eastern Canada and its evolutionary implications

12 Pages·1998·5 MB·English

by  G Raquel Guerstein

A NEW AREOLIGERACEAN DINOFLAGELLATE
FROM THE MIOCENE OF OFFSHORE EASTERN
CANADA AND EVOLUTIONARY
ITS
IMPLICATIONS
byG. RAQUEL GUERSTEIN, ROBERT A. FENSOMEandGRAHAM L. WILLIAMS
Abstract. The dinoflagellate family Areoligeraceae, now extinct, was prominent from the Late Jurassic
throughtothePaleogene.SomeareoligeraceanspeciesextendintotheNeogenebut,untilnow,nogenuswas
knowntooriginateinthatinterval.Thus,Ramidiniumgen.nov.,representedbyRamidiniumtridenssp.nov.
fromtheLowertoMiddleMioceneoftheJeanned’ArcBasin, offshoreeasternCanada,becomesthelast
knownareoligeraceangenustohaveappeared.
In 1965,duringanevaluationofthegeologyoftheGrand Banks, offshoreeasternCanada,Pan
AmericanPetroleumCorporation(nowAmocoProductionCompany)andImperialOilEnterprises
carried out a shallowcorehole drillingprogramme (Amoco and Imperial 1973). Several ofthese
cmoarteerhioallesfopretnheetrparteesdenMtesstouzdyo.icCoarnedhoCleen1o6zo(4i6c°s1t5r'atNa;, 4i9n°cl0u3d'inWg;CToerxet-hfoilge. 11a6),wwahsicdhrilplreodviind6e6d-8thme
ofwatertoadepthof448m.Subsequently,numeroushydrocarbonexplorationwellsweredrilled,
buttheshallowcoreholesremainavaluablesourceofinformationandstratigraphicalcontrol.
Williams and Brideaux (1975) studied 15 samples from Corehole 16 (Text-fig. 1b), which they
consideredtobeMidEoceneto Mid?Miocene. Inthepresentre-examinationofthismaterial,a
newgenusandspecieswasfoundintheuppermostsample(33-36m),whichWilliamsandBrideaux
dated as Mid? Miocene. The new taxon is clearly a gonyaulacalean dinoflagellate ofthe family
Areoligeraceae: likeotherareoligeraceansithasan offset sulcalnotch, alenticularshapeand an
apicalarchaeopyle. Howeveritbearscommonlytrifurcatesuturalprocessesandthussuperficially
resembles the common gonyaulacacean species, Spiniferites ramosus (Ehrenberg, 1838) Mantell,
1854. The main purpose of this paper is to describe the new taxon, assess its phylogenetic
relationships, andreassesstheageoftheuppermostsampleofCorehole 16.
MATERIALS AND METHODS
Thesamplesusedforthisstudywereoriginallyprocessedin 1972,andtherecordsfromthiswork
indicatethatatwominuteoxidationprocedure(otherwiseunspecified)wascarriedout. However,
when the residues were re-examined in 1994, there appeared to be no evidence of this earlier
oxidation.Inordertomaketheoriginalresiduesamenabletostudy,itwasnecessarytocarryout
a very mild oxidation treatment (10 per cent, nitric acid for 1-5 minutes) and base treatment
(ammonia for 1 minute). These procedures were in addition to the standard hydrochloric and
hydrofluoric acid treatments (carried out in 1972), heavy liquid separation of the organic
component,differentialcentrifugationtoremovefineparticles,screeningtodividetheresidueinto
fine(10-20^um)andcoarse(20-180/zm)fractions,andstainingwithBismarckBrown(allin 1994).
ThereprocessedmaterialwasmountedinElvaciteandacellosizesubstitute.
[Palaeontology,Vol.41,Part1,1998,pp.23-34,1pi.) ©ThePalaeontologicalAssociation
24 PALAEONTOLOGY,VOLUME41
text-fig. 1. a, location map, offshore eastern Canada (modified from McAlpine 1990). b, stratigraphical
distributionofthepalynologicalsamplesinCorehole 16(afterWilliamsandBrideaux 1975).
GUERSTEINETAL.: AREOLIGERACEANDINOFLAGELLATE 25
text-fig. 2. Ramidinium tridens gen. et sp. nov.; line sketches, a-b, GSC Atlantic slide no. P1433-10,
coordinates86-2x10(EFK15/0),GSCspecimenno.116293.a,ventralsurface,ventralview,b,dorsalsurface,
dorsal view (based on an inverted image), c, f, GSC Atlantic slide no. P1433-10, coordinates 93-3x8-3
(EFH23/3),GSCspecimenno. 116304;c,ventralsurface,ventralview;f,dorsalsurface,dorsalview(based
onaninvertedimage), d-e(holotype), GSCAtlanticslideno. P1433-10,coordinates84-7x2(EFB14/1),
GSCspecimenno. 116295;d,ventralsurface,ventralview(basedonaninvertedimage);e,dorsalsurface,
dorsal view, g-h, GSC Atlantic slide no. P1433-10, coordinates 97-5x5 (EF E27/0), GSC specimen no.
116297;G,ventralsurface,ventralview(basedonaninvertedimage);h,dorsalsurface,dorsalview.I,GSC
Avtilewa.nti(cFosrlidleinneo.drPa1w4i3n3g-s10o,fcodoinrodfilnaagteellsat1e1s0,-8itxi2s1c(oEnFveVn4t1io/n3a),lGtSoCshsopwecaimnen‘enxot.ern1a1l6’29v8i;ewo;petrhcuuslufmo,ratphiocsael
illustrationsindicatedtobebasedonaninvertedview,thedrawinghereisamirrorimageoftheappearance
ofthespecimeninthemicroscope.)Scalebarrepresents30/un.
Light microscopy was undertaken using Zeiss photomicroscopes at the Geological Survey of
Canada (Atlantic), Bedford Institute of Oceanography, Dartmouth, Nova Scotia. Coordinates
quotedarefromtheVernierScaleofZeissphotomicroscopeserialno.4660390.Thecorresponding
England Finder (EF) coordinates are given in the Plate and Text-figure explanations. Type and
26 PALAEONTOLOGY,VOLUME41
figured specimens are lodgedin theNational Collection ofType Invertebrate and Plant Fossils,
GeologicalSurveyofCanada, Ottawa,Ontario, Canada.
Somespecimenswerepicked,mountedandcoatedwithgoldforscanningelectronmicroscopy.
AnElectroScanE3 environmentalSEM attheGeologicalSurveyofCanada(Atlantic)wasused
underapartialpressureofwatervapour.
STRATIGRAPHY
Corehole 16 is located on the south-western margin ofthe Jeanne d’Arc Basin, which extends
roughly north-south for about 220km on the eastern periphery of the Grand Banks of
Ntheiwcfkonuesnsdliannedx.cesIsnoafre2a2lkemx.teInttisthaeMbeassoiznoiiscafabioluetd r1if5t0b0a0siknmw2i,twhitshomaemTearxtiiamruymfillse(dMicmAelnptianrey
1990)andwillbethemostpetroleum-productivebasininoffshoreeasternNorthAmericawhenthe
Hibernia field starts to produce oil in 1997. Shallow Corehole 16 is 18-2km north-north-east of
Amoco-ImperialMurreG-67well,thefirstexploratorywelldrilledinthebasin,andwhichattained
a depth of3337-3m in 64-6m ofwater. The youngest dated sediments in Murre G-67 are early
OligoceneandareunderlainsequentiallybyEoceneandCampanianstrata(Barssetal. 1979).The
totalthicknessoftheTertiarysectionisabout 1000m.
AllpreparationsstudiedfromCorehole 16arefromclasticsediments;moredetailedlithological
informationwasnotavailabletothepresentauthors.
BiostratigraphicalcontrolinCorehole16,asinMurreG-67,isbasedonpalynomorphs,primarily
dinoflagellates. Williams and Brideaux (1975) considered the sample at 32-9-36-0m (108-118'),
fromwhichthenewtaxonwasrecovered,tobenoyoungerthanmidMiocene.Thiswasbasedon
theirrecognitionofthefollowingspecies: Tanyosphaeridiumsp.A(nowDistatodiniumparadoxum
(Brosius, 1963)Eaton, 1976), ThalassiphoradelicataWilliamsandDownie, 1966(nowidentifiedas
ImertocystatabulataEdwards, 1984),TuberculodiniumrossignoliaeDrugg, 1970andLingulodinium
sp. B (nowSumatradiniumdruggiiLentin, FensomeandWilliams, 1994).
Williams(1975)outlinedapalynostratigraphicalzonationfortheMesozoic-Cenozoicrocksof
offshoreeasternCanada.TheApteodiniumspiridoidesBenedek, 1972(asApteodiniumsp.B)Zone,
ofEarlyMioceneage,wasdefinedontheLastAppearanceDatum(LAD)ofA.spiridoides.Inthe
sample,A.spiridoidesoccurstogetherwithSumatradiniumsoucouyantiaeandThalassiphorasp. 1of
EXPLANATIONOFPLATE 1
Figs1-15.Ramidiniumtridensgen.etsp.nov.1-2,GSCAtlanticslideno.P1433-10,coordinates86-2x10(EF
K15/0),GSCspecimenno. 116293. 1,ventralsurface,ventralview.2,dorsalsurface,ventralview.3,GSC
Atlanticslideno.P1433-10,coordinates117-3x2(EFB84/1),GSCspecimenno. 116294;ventralsurface,
dorsalview ofspecimen with operculum. 4-5, holotype, GSC Atlantic slide no. P1433-10, coordinates
84-7x2(EFB14/1),GSCspecimenno. 116295.4,ventralsurface,ventralview.5,dorsalsurface,ventral
view. 6,GSCAtlanticslideno. P1433-10,coordinates84-4x10(EFK13/0),GSCspecimenno. 116296;
ventralsurface,ventralview.7-8,GSCAtlanticslideno.P1433-10,coordinates97-5x5(EFE27/0),GSC
specimenno.116297.7,ventralsurface,dorsalview.8,dorsalsurface,dorsalview.9,GSCAtlanticslideno.
P1433-10, coordinates 1108x21 (EF V41/3), GSC specimen no. 116298; operculum, antapical view;
x1470. 10, GSC Atlantic slide no. P1433-10, coordinates 91-4x18-8 (EF T20/2), GSC specimen no.
116299; ventral surface, ventralview. 11, GSCAtlanticslideno. P1433-10, coordinates98-7x15-5 (EF
P28/4), GSC specimen no. 116300; dorsal surface, dorsal view. 12, GSC Atlantic slide no. P1433-10,
csloiodredinno.atPes1413038--140x,3c-o8o(rEdFinCa3t9e/s49)9,xGS18C-9sp(eEcFimTe2n8/n0o).,1G16S3C01s;pdeocrismalensunrof.ace1,16d3o0r2s;alvveinetwr.al13s,urGfSacCe,Atvleannttriacl
view. 14-15, GSCAtlanticslideno. P1433-10, coordinates 113-7x10-7 (EF L44/1), GSC specimenno.
116303. 14,ventralsurface,ventralview. 15,dorsalsurface,ventralview.
All x490,exceptwhereindicated.
PLATE
1
GUERSTEINetal., Ramidinium
28 PALAEONTOLOGY,VOLUME41
Powell (1988). Powell (1992) placed the LAD ofA. spiridoides in the early Burdigalian (Early
Miocene);however,deVerteuilandNorris(1992)extendedtheLADintothebasalSerravallian.
S.soucouyantiaedeVerteuilandNorris1992,originallydescribedfromthelowerMiddleMiocene
ofMaryland (de Verteuil and Norris 1992), is restricted to the Miocene. Thalassiphora sp. 1 of
Powell (1988) has a stratigraphical range ofBurdigalian-Langhian in surface sections from the
easternUSA.
The above association indicates a Burdigalian-Langhian (20-0-15-2Ma; Early to early Mid
Miocene) age forthe sample. IfWilliams (1975) and Powell (1992) are correct in believing that
ApteodiniumspiridoideshasitsLADintheBurdigalian,thiswouldsupportaBurdigalian(lateEarly
Miocene)age.
SYSTEMATIC PALAEONTOLOGY
Divisiondinoflagellata(Butschli, 1885)Fensome, Taylor, Norris, Sarjeant,Whartonand
Williams, 1993
ClassdinophyceaePascher, 1914
OrdergonyaulacalesTaylor, 1980
FamilyareoligeraceaeEvitt, 1963
Genusramidiniumgen. nov.
Derivationofname. FromtheLatinramus=branch,inreferencetothebranchedprocesses,andtheusual
dinoflagellatesuffix‘-dinium'.
Type.Plate 1,figures4-5;Text-figure2d-e.Ramidiniumtridens,gen.etsp.nov.
Diagnosis.Areoligeraceanproximochoratetousuallychorate,acavatecysts,withprocessesthatare
primarilyparasuturalandtypicallyirregularlybranched.
Comparisons. Among areoligeraceans, Ramidinium is distinct in having parasutural, branched
processes. ChiropteridiumGocht, 1960isalso anareoligeraceanwithsomeisolatedprocessesbut
differsfromRamidiniuminhavingproximallymembranous,confluentseptathatoccurprincipally
inthemarginalareas.Schindler(1992)describedfiveChiropteridiummorphotypes,eachexhibiting
fourlateral,crest-likestructuresonthedorsalandventralsurfaces,extendingmeridionallyfromthe
apical to the antapical region. These structures in Chiropteridium may be parasutural in part,
althoughthisisnotclearfrompublisheddescriptions.Ramidiniumhasamoreuniformdistribution
ofprocesses,andthecrest-likestructuresofChiropteridiumareabsentormayberepresentedbythe
lowridgesjoiningadjacentprocesses (PI. 1, figs 1-2; Text-figs2a, 3g). Theselowridgesmaybe
relicts of the membranes observed in Chiropteridium. Areoligera Lejeune-Carpentier, 1938 is
characterizedbythepresenceofarcuatecomplexesandGlaphyrocystaStoverandEvitt, 1978has
processesthatarepredominantlymarginateinpositionandtypicallynontabulateorintratabulate.
Enneadocysta Stover and Williams, 1995 also has an apical archaeopyle and some dorsoventral
compression, but differs from Ramidinium in having intratabular processes that, around the
antapex, are apparently arranged in the partiform pattern. Cooksonidium Stover and Williams,
1995 differs from Ramidinium in having intratabular processes, which sometimes occur in
penitabularcomplexes.SpiniferitesMantell, 1850andAchomosphaeraEvitt, 1963,whichalsohave
parasutural processes with furcate endings, are distinguished from Ramidinium by having a
precingulararchaeopyle.
Ramidinium tridenssp. nov.
Plate 1;Text-figures2-3
Derivationofname.FromtheLatintridens—trident,forkwiththreetines,inreferencetothedistalnatureof
theprocesses.Thespecificepithetisanouninapposition.
GUERSTEINETAL.. AREOLIGERACEANDINOFLAGELLATE 29
G H I
text-fig. 3. Ramidinium tridens gen. et sp. nov., scanning electron photomicrographs; GSC Atlantic
preparationP1433.a,stubno. 1433a,GSCspecimenno. 116305,specimenlost;ventralview;x526.b,stub
no. 1433a,GSCspecimenno. 116306(specimenlost);ventralview?;x847.c,stubno. 1433a,GSCspecimen
no. 116307(specimenlost);x581.d,stubno. 1433a,GSCspecimenno. 116308(specimenlost);x555.e,stub
no. 1433r,GSCspecimenno. 116309;detailshowingthewallstructureandprocesses;x1786.f-g,stubno.
1433r,GSCspecimenno. 116310.f,ventralview;x658.G,detailshowingprocessesjoinedbasallybylow
ridges;x 1538.h,stubno. 1433r,GSCspecimenno. 116311;detailoftrifurcateprocess;x 1389.i,stubno.
1433r,GSCspecimenno. 116312;apicalview;x741.
Holotype. Plate 1, figures4—5; Text-figure 2d-e. GSC specimenno. 116295, National Collection ofType
InvertebrateandPlantFossils,GeologicalSurveyofCanada,Ottawa,Ontario,Canada;GSCAtlanticslide
No P1433-10, coordinates: 84.7x2 (EF B14/1). Type locality: 108-118 feet, Corehole 16, 46°15'N,
49°03'W,GrandBanks,offshoreeasternCanada.
30 PALAEONTOLOGY,VOLUME41
text-fig.4.SpindleplotsshowingthespeciesdiversityofindividualgeneraofthefamilyAreoligeraceaeper
unittime.Thewidthofeachbarrepresentsnumberofspecies.Seetextforfurtherdetails.Stages(Mesozoic)
and epochs and subepochs (Tertiary) are indicated as follows, in ascending order: Jurassic stages: B=
Bajocian, B=Bathonian, C=Callovian, O=Oxfordian, K=Kimmeridgian, unlabelled=Portlandian.
Cretaceous stages: B=Berriasian, V=Valanginian, H=Hauterivian, B=Barremian, A=Aptian, A=
GUERSTEINETAL.: AREOLIGERACEANDINOFLAGELLATE 3:
Diagnosis.AspeciesofRamidiniumwithc.20-26primarilyparasuturalprocessesthathavemostlyirregular
trifurcateendings.
Description
Shape.Cystsproximochoratetochorate,dorsoventrallycompressed,centralbodylenticular.Antapicaloutline
symmetricalorasymmetrical.
Wallrelationships.Autophragmonly.
Wallfeatures.Autophragmfinelyornamented,typicallyirregularlyreticulatetorugulate(Text-fig.3e).There
are20-26processes,11or12ontheepicyst,fivetonineonthehypocyst,andfourorfiveontheparacingulum.
Processesusuallygonalandintergonal(PI. 1,figs7-8;Text-fig.2d-h),possiblysometimesintratabular;they
are usually cylindrical or rounded triangular in cross section, solid and generally ending in irregular
trifurcations(Text-fig.3d,h),buttheymaybedistallybifurcateorasymmetricallyexpanded(Text-fig.2b,h-i).
Some processes may be hollow (Text-fig. 3e) and, occasionally, taeniate processes occur that give the
impressionoftwostemsjoinedbyamembrane(PI.1,figs6,10-12,15;Text-fig.3b,e-f,i).Adjacentprocesses
aresometimesjoinedbasallybylow,possiblyparasuturalridges(PI. 1,figs 1-2,5,10;Text-fig.3g).Delicate
trabeculaeoccasionallyconnectpostcingularprocesses(PI. 1,fig. 13).
Paratabulation. Areoligeraceanparatabulationindicatedonepicystbyarchaeopylesuturesand locationof
parasuturalprocesses. Elsewhereoncentralbody,paratabulationindicatedsolelybyprimarilyparasutural
processes.Generallythereisnoprocessbetweenparaplate6”andtheanteriorsulcalparaplate(Text-figs2a,
d,g,3a).
Paracingulum.Indicatedbyfourorfiveprocessesingonalorintergonalpositions.
Parasulcus.Positionindicatedanteriorlybyoffsetparasulcalnotch(Text-fig.2d,g).Rarelyparasulcalnotch
medialoronlyslightlyoffset(PI. 1,fig. 14).
Archaeopyle. Apical, type (tA); operculum tetratabular, simple, free and longer transversally than
dorsoventrally(PI. 1,figs3,9;Text-fig.2i).
Size. Holotype: lengthofthecentralbody(withoutoperculum):42pm\widthofthecentralbody: 53pm;
process length: 13-19pm. Range of 20 specimens: length of the central body (including operculum):
47(55)63pm; length ofthe central body (without operculum): 36(41)47pm; width ofthe central body:
47(55)63pm;processlength:9-23pm.
Comparisons
Ramidinium tridens resembles the type material ofGalea twistringiensis Maier, 1959, which has
a smooth wall and distally widened and regularly divided processes. Sarjeant (1983) included
G. twistringiensis in synonymy with Spiniferites ramosus var. multibrevis, implying that is has a
precingularratherthananapicalarchaeopyle.Chiropteridiumgalea(Maier, 1959)Sarjeant, 1983is
the speciesofChiropteridiummost similarto R. tridens, havingprocessesthat maybe furcate or
Albian,C=Cenomanian,unlabelled=Turonian,unlabelled=Coniacian,S=Santonian,C=Campanian,
M=Maastrichtian. Tertiary epochs: P=Paleocene, E=Eocene, O=Oligocene, M=Miocene, P=
Pliocene.TeriaryepochsaredividedintoEarly(E)andLate(L)orEarly(E),Mid(M)andLate(L)subepochs,
exceptforthePliocene,whichisundividedinthisstudy.Theunlabelledintervalatthetopoftheplotrepresents
theQuaternary.ThetimescaleusedhereinisbasedonthatofHarlandetal.(1990),exceptforourusageof
PortlandianratherthanTithonianforthelatestJurassicstage.
32 PALAEONTOLOGY,VOLUME41
branched. However, R. tridens differs from C. galea in havingprocesses on the epicyst that are
consistentlyparasuturalinposition,isolatedorunitedbylowridgesonly.ProcessesonC.galeamay
beisolated,buttendtoarisefromfourmarginalmeridionalcrestswhichusuallyarenotobviously
parasutural. Nevertheless, in some specimens of C. galea from the Grand Banks, meridional
membranesareclearlyinpartparasutural,sincetheyalignwiththeaccessoryarchaeopylesuture
betweenprecingularparaplates. Chiropteridium Morphotype E ofSchindler (1992) also hasfour
meridional membranes almost fully divided into hollow, distally closed and proximally
interconnectedprocesses towardsthepolestheseprocessesaremoreslenderanddistallyfurcated.
However,MorphotypeE;differsfromR. tridensinlackingtheprocessesonmid-ventralandmid-
dorsalsurfacesandinhavingadistinctlygranulatewall.R. tridenshasanirregularlyreticulateto
rugulate wall and, occasionally, low proximal ridges joining adjacent processes. Enneadocysta
harrisii Stover and Williams, 1995 has similar process stems, but the processes are intratabular
ratherthanparasuturalandhavelicrateendings.
Occurrence.Lower-lowerMiddleMiocene(Burdigalian-Langhian,asdeterminedfrompalynology),Corehole
16,GrandBanks,offshoreEasternCanada.
DISCUSSIONAND CONCLUSIONS
ThefamilyAreoligeraceaeisanextinctdinoflagellatefamilythatfirstoccurredintheLateJurassic
andwascommonthroughouttheCretaceousandPaleogene.Thestratigraphicaldistributionand
speciesrichnessofallareoligeraceangeneraareshowninText-figure4.IntheMesozoic,thefamily
was represented by forms with no, or only low, spines (proximate and proximochorate cysts),
whereasduringthe Paleogene, representatives tended to be spinose (chorate, e.g. Areoligeraand
Glaphyrocysta). In the later Paleogene, forms with marginal membranes or wall cavities (e.g.
Membranophoridium Gerlach, 1961 and Chiropteridium) became common. Previously, no new
genera were known to have evolved in the Neogene; Ramidinium, a possible derivative of
Chiropteridium,isthustheonlyknownareoligeraceangenustoappearintheNeogene.
InformationforText-figure4(exceptfortheRamidiniumbar,whichisbasedonthepresentwork)
was derived from PALYNODATA, a database compiled over the past quarter century by a
consortiumofseveralmajoroilcompaniesandtheGeologicalSurveyofCanada.PALYNODATA
stores biostratigraphical information from pre-Quaternary palynology publications: at present,
PALYNODATAcontainsinformationfromabout 18000suchpublications. InText-figure4,the
number of species per genus per unit time are plotted. It was impractical to check the many
hundredsofrecordsthatcontributedtothisplot,althoughadetailedsearchofanomalousrecords
eliminatedsomethatclearlyrepresentedreworkingorcontamination(forfurtherelaborationofthe
techniquesinvolved,seeFensomeetal. 1996andMacRaeetal. 1996).Text-figure4emphasizesthat
Ramidinium is indeed the last evolving genus ofaprominent and biostratigraphically important
familyofdinoflagellates.
The later evolutionary pattern of the Areoligeraceae is reflected in our observations of the
dinoflagellateassemblagesfromCorehole 16.TheEarlyOligoceneassemblage(88-91m)contains
theareoligeraceansMembranophoridiumaspinatumGerlach, 1961 and Chiropteridiumgalea,with
transitional forms between the two species. In the assemblage from the Upper Oligocene
(116-5-119-5m), C. galeawas the only areoligeracean present and is a dominant element. Thus,
thereisanapparenttrendfromthemembranousareoligeraceanstoformswithdividedmembranes
andisolatedprocesses. ThistrendappearstoculminatewithRamidinium tridens.
Acknowledgements. The authors acknowledge the technical assistance ofB. Crilley, W.C. MacMillan, N.
Koziel,B. MedioliandA.S. Henry. FordiscussionandinformationwearegratefultoJ.Jansonius,R.A.
MacRae,M.E.Quattrocchioandanunidentifiedreviewer.G.R.Guerstein’sparticipationwassupportedby
ConsejoNationaldeInvestigacionesCientificasyTecnicas,Argentina.Weacknowledgethesupportofthe
PALYNODATAsponsors:AmocoProductionCo.,ExxonProductionResearchCo.,UnocalCorporation,