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Quaternary International 301 (2013) 135e149

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Quaternary International

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Paleoecological significance of Late Quaternary molluscan faunas ofthe Bahia San Blas area, Argentina

M.P. Charó a,*, S. Gordillo b, E.E. Fucks c

a Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, CONICET, 64 No.3, ArgentinabCentro de investigaciones en Ciencias de la Tierra (CICTERRA, CONICET-UNC), Córdoba, Argentinac Facultad de Ciencias Naturales y Museo y Ciencias Agrarias y Forestales-LATYR-UNLP, Argentina

a r t i c l e i n f o

Article history:Available online 25 December 2012

* Corresponding author.E-mail addresses: charomelisa@yahoo.com.ar (M.

conicet.gov.ar (S. Gordillo), efucks@fcnym.unlp.edu.ar

1040-6182/$ e see front matter � 2012 Elsevier Ltd ahttp://dx.doi.org/10.1016/j.quaint.2012.12.019

a b s t r a c t

Late Quaternary marine deposits in the area of Bahía San Blas (Buenos Aires, Argentina) form beachridges and tidal plains bearing remains of organisms, mainly mollusc shells. These mollusc assemblageswere characterized, and their changes assessed both over time, and related to local environmentalfactors. Twenty-six sites were analyzed, eleven Pleistocene, seven Holocene and eight modern sites. Fiftytaxa (27 bivalves and 23 gastropods) were recorded for the area, with marine species predominant overestuarine. Within gastropods, epifaunal species and carnivores are predominant, with a lower proportionof herbivores and filter feeders, while bivalves are mostly infaunal and suspension feeders. Pleistoceneassociations are characterized by the high quantity of molluscs in rocky environments, and those of theHolocene by the presence of the warm water Crassostrea rhizophorae, which is currently displaced tolower latitudes. Within the modern associations four taxa, Mesodesma mactroides, Solen tehuelchus,Barnea lamellosa and Crassostrea gigas (an introduced species), are not recorded as fossils, but Mesodesmamactroides is found in Holocene shell middens from the area. According to multivariate analysis, the siteswere divided into two groups: high energy deposits (storm ridges) and low-energy deposits (tidalplains), regardless of their age. Based on these results, mollusc variations in the area are thought to berelated in part to changes in temperature that took place since the Pleistocene (e.g. C. rhizophorae); butmostly associated with the presence of sub-environments of different energy levels. This would favor thepresence of different taxa in accordance to their ecological requirements.

� 2012 Elsevier Ltd and INQUA. All rights reserved.

1. Introduction

TheQuaternary is characterizedworldwide by important climateoscillations, with extremes represented by glacial and interglacialperiods resulting from temperature variations that caused markedchanges in sea level (e.g. Rohling et al., 2003). In coastal areas,transgressive events have been registered by a sequence of erosionforms (coastal terraces and paleocliffs) and beach deposits that, fordifferent reasons, have been protected from degradation processesand are therefore an important testimony of climate changes thathave occurred in most recent geologic times (Shackleton, 1987).

In the Patagonian coastal region, these deposits can be foundboth along the coastline, and well inland. This gives evidence of themagnitude of the transgressive events, and of the geomorphologiccharacteristics and isostatic variations. The most extreme sea levels

P. Charó), sgordillo@cicterra-(E.E. Fucks).

nd INQUA. All rights reserved.

are clearly seen at various sites along the coast, although due to thecontinental rise (Fucks et al., 2009; Pedoja et al., 2011) lower levelscan also be seen above the current sea level in several sites. Ona larger scale, Pleistocene coastal fossil deposits are knownworldwide, from the North American Pacific coast (e.g. Roy et al.,1998; Parham et al., 2007), to Mexico (e.g. Ortlieb, 1991; Muhset al., 1992, 2002; De Diego-Forbis et al., 2004), Bermuda (Hearty,2002), Japan (e.g. Kim et al., 1999; Kitamura et al., 2000),Australia (Murray-Wallace and Belperio, 1991; Murray-Wallaceet al., 2000), and Europe (e.g. Lario et al., 1993; Zazo, 1999; Zazoet al., 2003a; Dumas et al., 2005). Along the South Americancoast, deposits of different sea levels related to transgressive eventscan be seen in Brazil (e.g. Caruso et al., 2000; Barreto et al., 2002),Uruguay (e.g. Martinez et al., 2001; Goso Aguilar, 2006), Chile(Quezada et al., 2007), and Argentina (e.g. Cionchi, 1987;Codignotto et al., 1988; Codignotto and Aguirre, 1993; Schellmann,1998; Isla et al., 2000; Rostami et al., 2000; Schellmann and Radtke,2000, 2003; Weiler, 2000; Bujalesky and Isla, 2006; Isla andBujalesky, 2008; Pedoja et al., 2011).

mailto:charomelisa@yahoo.com.armailto:sgordillo@cicterra-conicet.gov.armailto:sgordillo@cicterra-conicet.gov.armailto:efucks@fcnym.unlp.edu.arhttp://crossmark.dyndns.org/dialog/?doi=10.1016/j.quaint.2012.12.019&domain=pdfwww.sciencedirect.com/science/journal/10406182http://www.elsevier.com/locate/quainthttp://dx.doi.org/10.1016/j.quaint.2012.12.019http://dx.doi.org/10.1016/j.quaint.2012.12.019http://dx.doi.org/10.1016/j.quaint.2012.12.019

M.P. Charó et al. / Quaternary International 301 (2013) 135e149136

The most representative fauna of these Quaternary marinedeposits are the molluscs, in particular gastropods and bivalves,and their preservation makes them very useful as proxy paleo-climatic and paleoenvironmental records. Analysis of these taxaprovides information on different environmental parameters suchas temperature, salinity and substrate, thus leading to an inter-pretation of the paleoenvironment and the paleo-communities thatexisted in the different regions throughout time. Recent studieshave also used this information as paleoenvironmental parametersand for paleoclimatic studies such as atmospheric and oceano-graphic changes (e.g. Ortlieb et al., 1994; Martinez et al., 1997, 2001;Massch et al., 2001; Ragainia et al., 2002; Aguirre et al., 2006;Cárdenas and Gordillo, 2009; Rabassa et al., 2009; Jones et al., 2010;Rojas and Urteaga, 2011).

During the last interglacial the MIS 5e (MIS ¼ Marine IsotopeStage), which occurred between 130 � 2 and 119 � 2 ka (Heartyet al., 2007), sea level rose at least twice (e.g. Zazo et al., 2003a,b;Tuccimei et al., 2006). In this period, surface sea temperatures (SST)were approximately 2 C� above the present temperature (McCulloch and Esat, 2000; Murray-Wallace et al., 2000; Rohlinget al., 2008), and sea level reached approximately five to sixmeters above the present sea level (Shackleton, 1987; Neumannand Hearty, 1996). Records worldwide show evidence of warmwater in benthic marine molluscs, as well as changes in theirgeographical distribution (Chaar and Farinati, 1988; Cuerda et al.,1991; Martinez et al., 2001; Muhs et al., 2002; Zazo et al., 2003b,Zazo et al., 2010; Rojas and Urteaga, 2011, among others).

A warm event was detected in the Mid-Holocene (8700e7800BP) of the Northern Hemisphere, known as the Climatic Optimumor Hypsithermal, in which the SST and humidity were higher thantoday (e.g. Funder and Weidick, 1991; Salvigsen et al., 1991; Hjortet al., 1995; Rohling and De Rijk, 1999; Yuan et al., 2011). Someevents have also been recorded in the Southern Hemisphere (e.g.Aguirre, 1990, 1993b, 2002; Cohen et al., 1992; Lutaenko, 1993;Gordillo et al., 2005). The main purpose of this study is to charac-terize molluscan associations of Bahía San Blas during this period,and to assess their changes over time and related to local envi-ronmental factors.

1.1. Study area

The study area is located in the south of the Buenos AiresProvince, extending from Isla Jabalí (40�360S; 62�110W) to FaroSegunda Barranca (40�460S; 62�160W; Lighthouse SegundaBarranca) and from the coastline to National Route 3 (Fig. 1). Themost characteristic geomorphologic features are beach ridges andlow, gravel plains. The beach ridges may be grouped according todifferent transgressive episodes. The lower ones (3e5 m a.s.l.) aregrey gravels and sandswith low-angle cross bedding, fourmeters ofmaximum thickness. They are small active cliffs and topographicalledges among the different groupings that can even be consideredas beach strand plains due to their quantity and disposition (Fuckset al., 2012). Holocene deposits can be seen in large number at IslaJabalí, where they can be geomorphologically divided into two welldefined groups. To the east, they are flat and composed of brown-grey silty sand; the lower section is finely stratified, while theupper is more homogenous and browner. The western area hasa significant amount of ridges very close together and are eitherparallel, transverse or at an oblique angle to each other (Fucks et al.,2011, 2012).

Inland, behind the Holocene deposits, there is a second level ofbeach ridges (8e10 m), less pronounced and either parallel to thecoast or at an oblique angle. These ridges are made up of friablegravel, with nodules, and correspond to the Late Pleistocene trans-gressive event (MIS 5e). They extend north to south and are cut off in

the north by the Jabalí Streamand in the south by theWalker Stream(Fucks et al., 2012). These ridges are parallel to the coast to FaroSegunda Barranca,where a gravel and sand beach is observed on thecoastal platform of the Río Negro Formation. The cliffs are 10 mmaximum height, and consist of sand and silt at the base, and well-stratified gravel in the middle and upper sections (Fig. 2).

Above these, up to near 35m a.s.l., gentle plains with outcrops oflong, circular elevations of gravel highly cemented with calciumcarbonate have been observed. In all of these morphologies,mollusc remains and/or flattened clasts indicate their littoral origin(Fucks et al., 2012).

The development of numerous deflation basins occupied by saltflats (Barrancoso, Grande, La Salinita, Salina del Inglés, amongothers) is one of the most common features of the continental area.The highest concentration of salts is normally found in the lowestareas, with sodium chloride predominating, and clay and alkalinesulphates in lower quantities (Trebino,1987; Del Blanco et al., 2005).

1.2. Geological background

Witte (1916) was the first to study the area and to describe thegeology of the San Blas coastal deposits. He defined five evolutionstages (IeV) represented in different sections of the coast, andnoted that the sediments forming the deposits corresponded toStages III (Pleistocene), IV and V (Holocene).

Ambrosini (1984) and Trebino (1987) analyzed the geomor-phology of Bahía San Blas area, and described Pleistocene, Holoceneand modern geofeatures. Trebino (1987) recognized three levels ofmarine terraces, I and II from the Pleistocene and III for the Holo-cene. Terraces I and II are located in Rincón deWalker, and III in IslaJabalí, and are a result of successive accumulation of beach strandsand spits (Etcheverría et al., 2006). The Holocene deposits, locatedat an altitude of 3 m a.s.l., were previously dated by Trebino (1987)at 2170 � 110, 3450 � 110, 3650 � 80 (LP ¼ 2434), 4100 � 95,5370 � 110, 2320 � 80, and 3450 � 80 14C BP.

Pleistocene beach ridges, located to the west of the JabalíStream, were dated at 28,400 � 800 and 29,120 � 970 14C BP(Trebino, 1987) and 30,780 � 1650 BP Weiler (2000). These areconsidered to be the minimum ages, correlating with the LatestInterglacial event (MIS 5e).

Schnack et al. (2005) considered thatWitte’s (1916) I to III stageswereequivalent toTrebino’s (1987) level I and II Pleistocene terraces,whereas the Holocene deposits corresponding to Witte’s (1916)stage IV would be equivalent to Trebino’s (1987) level III terrace.

The most recent geochronological research carried out in theFaro Segunda Barranca area used ESR and amino acid racemizationdating techniques. The base of the cliff (site 24) was dated at 102and 108 ka, while the upper part of the cliff (site 23) oscillatedbetween 94, 79, and 72 ka. Although all the dating was carried outusing the ESR method, the D/L ratio of aspartic acid and leucinecould link this site to an older transgressive event (Rutter et al.,1989, 1990). These last sequences belong to the MIS 5e strati-graphic unit, which is equivalent to Feruglio’s terrace V (1959) andto the Belgranense (Ameghino, 1889) or Puente Pascua Formation(Fucks et al., 2005).

Fucks et al. (2012) reinterpreted the stratigraphic sequences ofthis area, assigning a minimum of four transgressive cycles. Beachridges, as well as beach strand plains and tidal plains withmaximum altitudes of 6 m a.s.l. and very clear morphologies arepresent from the coast to the present day continent, particularly inIsla Jabalí. Above them, at altitudes of 8e10 m a.s.l., clear ridgescould be probably related to MIS 5e, although less than theprevious ridges, and that increase gradually to altitudes of over30 m a.s.l. These could have been originated in two �9transgressive events (Table 1).

Fig. 1. Map showing the location of the Bahia San Blas in the south of the Buenos Aires province, and the Pleistocene, Holocene and modern sampling.

Table 1Geomorphological characterization of the studied sites located in the San Blas area.

Marinedeposits

Witte (1916) Trebino (1987) erosivefeatures: Terraces

Accumulation features Schnack et al. (2005) Fucks et al. (2012)

Bahia SanBlas

Holocene Stage V: Modern beachmarine deposits.Stage IV: Marine deposits1.50 m higher than currentheight.

Level III: Poorly represented;can be seen in a discontinuousalong Walker Stream.Corresponds to more modernterraces with altitudes of 3 ma.s.l.

Section B: All marineaccumulation cut off bymarine erosion orinterdigitation.

Witte’s (1916) StageIV equivalent toTrebino’s terracelevel III.

Represented by beachridges, beach strandplains and tidal plainswith maximum altitudesof 5 m a.s.l.

Pleistocene Stage III: Marine coastalbanks with a sea levelapprox. 10 m higher thanin modern times.Old coastlines are clearlyvisible.

Level II: Rows of beach strandscorresponding to old coastlinesat 10 and 11 m a.s.l.Level I: The oldest: located onold boulder deposits between12 and 14 m a.s.l.

Section A: Located westof Jabali Stream and tothe south of the GuanacoStream. Long, wide beachridges located between 9and 10 m a.s.l.

Witte’s (1916) StagesIeIII e equivalent toTrebino’s (1987) terracelevels I and II.

Beach ridges at 8e10 ma.s.l.

M.P. Charó et al. / Quaternary International 301 (2013) 135e149 137

M.P. Charó et al. / Quaternary International 301 (2013) 135e149138

1.3. Paleontological background

The first studies on marine molluscs in the Buenos Aires Prov-ince were mainly of a geological character. Frenguelli (1928, 1950)contributed greatly to the understanding of Quaternary marinefauna. Pioneer studies from around this period were also carriedout by D’Orbigny (1834e1847, 1842e1844), Darwin (1846),Ameghino (1898, 1908), von Ihering (1907) and Wahnish (1939),among others. The first mention of systematic mollusc studiesappeared in contemporary research (Carcelles, 1944; Camacho,1966; Castellanos, 1967, 1979, 1981). Among the most recentstudies on Quaternary molluscan assemblages in the littoraldeposits of the Buenos Aires Province, contributions from Farinatiand Camacho (1980), Farinati (1985, 1994), Chaar et al. (1992),Aguirre (1990, 1993aec, 2002), Aguirre and Whatley (1995),Aguirre and Farinati (2000), Aguirre and Fucks (2004), and Fuckset al. (2005), among others, are noteworthy. Some recent studiesof Quaternary deposits of Bahía San Blas and Faro Segunda Barrancamention molluscs, but they are mainly geomorphological andgeochronological research (Trebino, 1987; Rutter et al., 1989, 1990;Fucks et al., 2012).

2. Materials and methods

Twenty-six sites were analyzed in the study area: eleven Pleis-tocene, seven Holocene, and eight modern (Table 2). The samplescollected from the Pleistocene and Holocene deposits (1 dm3) wereexposed to running water using sieves of three different size:2.80 mm, 1.40 mm and 0.080 mm. A sequence of washing anddrying on paper was then followed. The modern samples weretaken in a 1 m � 1 m quadrant on transects perpendicular to thecoastline. The molluscs were collected by hand and were thensorted using a 2.80 mm sieve.

Table 2Description of sampled localities.

Bahíasan Blas

Age Sites Coordinates (Lat-Long)

Modern 1 40�31040.8000S; 62�1905.4000O2 40�3209.3200S; 62�18047.1600O3 40�32020.1200S; 62�15022.0800O4 40�33015.6800S; 62�13028.3800O5 40�34011.7000S; 62�11049.8600O6 40�35035.9200S; 62�10015.7800O7 40�46030.8000S; 62�16018.5000O8 40�46032.9100S; 62�16019.9500O

Holocene 9 40�3209.4300S; 62�17022.5500O10 40�34014.3300S; 62�15019.4500O11 40�3409.3000S; 62�13057.8000O

12 40�34023.5900S; 62�14011.7100O13 40�34056.2000S; 62�14011.4300O14 40�34051.9100S; 62�1307.1400O

15 40�3709.0000S; 62�12049.2000OPleistocene 16 40�33058.5000S; 62�1907.3000O

17 40�3406.7000S; 62�18052.1200O18 40�3509.9000S; 62�17028.8000O19 40�35019.4000S; 62�1705.8000O20 40�35047.3500S; 62�19011.9300O21 40�3606.1700S; 62�16010.5500O22 40�40049.9900S; 62�3006.6000O23 40�46024.0200S; 62�16017.2400O

24 40�46034.5600S; 62�16024.5000O25 40�27032.7700S; 62�47057.6600O

26 40�35030.3600S; 62�49052.9100O

Each piece of biogenic content that was captured by the sieveswas identified and labelled; first, the material was sorted, usinga magnifying glass when necessary, and then it was divided intotaxa by comparing it with catalogs and current specific systematicstudies.

For each sampled site, the Shannon Index (H0) was calculatedthrough an XeY graph and the ecological parameters of gastropodsand bivalves were compared for each period. In order to analyze thedegree of similarity between sites, cluster analyses were carried outwith R software, version 2.15.0 (vegan package) (Oksanen, 2011),and the UPGMA method was used to group the faunal associationsaccording to the BrayeCurtis Index. In this case, a matrix was usedfor each site to show the abundance of different species. ACorrespondence Analysis (CA) was then carried out to observethe relationship between sites. The ecological information on thetaxa is based on living specimens and also on bibliographicalsources (Lasta et al., 1998; Bastida et al., 2007; Balech and Ehrlich,2008; Rosenberg, 2009).

3. Results

3.1. Taxonomic and paleoecological composition

Twenty-six sites were analyzed in Bahía San Blas, includingPleistocene, Holocene and modern deposits, in which 50 taxa(N ¼ 388 shells) were recorded (27 bivalves and 23 gastropods)(Figs. 3 and 4) (Tables 3 and 4). According to Shannon’s diversityindex (H0), the modern sites have greater diversity, with valuesranging between 2.3 and 1.5, compared to Holocene sites whichshow lower values, between 0.22 and 0.86, with the exception ofsites 11 (H0 ¼ 2.28) and 14 (H0 ¼ 2.28) that belong to beach ridges.Pleistocene sites show values between 0.29 and 1.98, with thehighest values at sites 20 (H0 ¼ 2.09) and 22 (H0 ¼ 2.52) (Fig. 5).

Geomorphology Altitude (m.a.m.s.l.)

Beach 0Beach 0Beach 0Beach 0Beach 0Beach 0Beach 0Beach 0Tidal plain deposits 1Tidal plain deposits 1Beach ridge made of sandy sedimentsand containing clasts

4

Tidal plain deposits 3Tidal plain deposits 5Beach ridge made of sandy sedimentsand containing clasts

4

Tidal plain deposits 5Beach ridge made of sandy sediments 9Beach ridge made of sandy sediments 7Beach ridge made of sandy sediments 7Beach ridge made of sandy sediments 4Beach ridge made of sandy sediments 5Beach ridge made of sandy sediments 5Profile 50 cm from the surface 2Beach ridge with layers of sandy sedimentsand clasts

8

Fine sediment facies at the base of the profile 10Beach ridge with sandy sediments containingclasts and rough gravel

32

Quarry with clustered gravel 33

Table 3Bivalves from the Quaternary (P ¼ Pleistocene, H ¼ Holocene and M ¼ modern)marine deposits in the Bahía San Blas area.

Bivalvia P H M

Nucula (N.) nucleus (Linné, 1758) X XEnnucula grayi (d’Orbigny, 1846) XGlycymeris (G.) longior (Sowerby, 1832) XMytilus (M.) edulis (Linné, 1758) X X XBrachidontes (B.) rodriguezi (d’Orbigny, 1846) X X XAequipecten tehuelchus (d’Orbigny, 1842) X X XPlicatula gibbosa (Lamarck, 1801) XOstreola equestris (Say, 1834) X X XCrassostrea rhizophorae (Guilding, 1828) XOstrea puelchana (d’Orbigny, 1841) X X XCrassostrea gigas (Thunberg, 1793) XDiplodonta (D.) patagonica (d’Orbigny, 1842) X XDiplodonta (F.) vilardeboana (d’Orbigny, 1846) XCarditamera plata (Inhering, 1907) X XTrachycardium muricatum (Linné, 1758) XMactra isabelleana (d’Orbigny, 1846) XMactra guidoi (Signorelli and Scarabino) X XMulinia edulis (King and Broderip, 1831) XMesodesma mactroides (Reeve, 1854) XSolen tehuelchus (Hanley, 1842) XMacoma (P.) uruguayensis (Smith, 1885) X XTagelus (T.) plebeius (Ligthfood, 1786) XPitar (P.) rostratus (Philippi, 1844) X X XAmiantis purpurata (Lamarck, 1856) X X XCorbula (C.) patagonica (d’Orbigny, 1846) X X XCorbula (C.) lyoni (Pilsbry, 1897) XBarnea lamellosa (d’Orbigny, 1846) X

Table 4Gastropods from the Quaternary (P ¼ Pleistocene, H ¼ Holocene and M ¼ modern)marine deposits of the San Blas bay area.

Gastropods P H M

Diodora (D.) patagonica (d’Orbigny, 1841) XLucapinella henseli (Martens, 1900) XTegula (A.) patagonica (d’Orbigny, 1835) X X XCalliostoma coppingeri (Smith, 1880) XHeleobia australis (D’Orbigny, 1835) X X XBostrycapulus odites (Collin, 2005) X X XCrepidula argentina (Simone Pastorino and

Penchaszadeh, 2000)X X

Notocochlis isabelleana (d’Orbigny, 1840) XTrophon varians (d’Orbigny, 1841) X X XUrosalpinx cala (Pilsbry, 1897) XZidona dufresni (Donovan, 1823) X X XAdelomelon (P.) brasiliana (Lamarck, 1811) XOdontocymbiola magallanica (Gmelin, 1791) XOlivella (O.) tehuelcha (Dúclos, 1835) X XOlivancillaria urceus (Röding, 1798) XOlivancillaria carcellesi (Klappenbach, 1965) X XMarginella martini (Petit, 1853) X XBuccinanops moniliferum (Kiener, 1834) X XBuccinanops cochlidium (Dilwyn, 1817) X XBuccinanops globulosum (Kiener, 1834) X X XBuccinanops uruguayense (Pilsbry, 1897) X XParvanachis isabellei (d’Orbigny, 1839) X

Table

5Ec

olog

ical

requ

irem

ents

anddistribution

ofbiva

lves:Ep

¼ep

ifau

nal,I¼

infaunal,Ce¼

Cem

ented;

H¼

hard,

S¼

soft;C¼

carn

ivorou

s,D

¼detritivo

rous,

H¼

herbivo

re,Sf

¼su

spen

sion

feed

er;O

¼oligoh

aline(3e8&

),M

¼mesoh

aline(8e18

&),P¼

polyh

aline(18e

30&),E¼

euhaline(>

30e35

&).

Bivalvia

Salin

ity

Life

hab

itDep

th(m

)Su

bstrate

Trop

hic

type

Distribution

area

Nuc

ula(N

.)nu

cleu

s(Linné,

1758

)E

I0e

200

SD

23� Se53

.5� S

Ennu

cula

gray

i(d’Orbigny,

1846

)E

I5e

1850

SD

22.93�Se

55.5

� SGlycymeris(G

.)long

ior(Sow

erby

,183

2)E

I10

e75

SSf

10� Se42

� SMytilu

s(M

.)ed

ulis(Linné,

1758

)Pe

EEp

0e50

HSf

68� N

e55

.5� S

Brachido

ntes

(B.)rodrigue

zi(d’Orbigny,

1846

)E

Ep0e

25H

Sf34

� Se42

� SAeq

uipe

cten

tehu

elch

us(d’Orbigny,

1842

)E

Ep10

e12

0M

Sf21

� Se53

� SPlicatulagibb

osa(Lam

arck

,180

1)E

Ce

0e12

0H

Sf35

.3� N

e34

� Sa

Ostreolaeq

uestris(Say

,183

4)Pe

ECe

0e80

HC

37� N

e42

� SCrassostrearhizop

horae(G

uild

ing,

1828

)Pe

ECe

0e50

HC

21.4

� Ne35

� SOstreapu

elch

ana(d’Orbigny18

41)

PeE

Ce

0e70

HC

22� Se42

� SCrassostreagiga

s(Thunbe

rg,1

793)

ECe

0e40

HSf

Cosmop

olitan

Diplodo

nta(D

.)pa

tago

nica

(d’Orbigny,

1842

)E

I36

e10

2S

Sf21

� Se42

.58�S

Diplodo

nta(F.)vilardeb

oana

(d’Orbigny,

1846

)E

I25

e77

SSf

21� Se42

� SCa

rditam

eraplata(Ihering,

1907

)E

I17

e70

SSf

23� Se39

� Sa

Trachy

cardium

muricatum

(Linné,

1758

)E

I0e

11S

Sf35

� Ne42

� SMactraisab

ellean

a(d’Orbigny,

1846

)Pe

EI

0e25

SSf

23� Se42

� SMactragu

idoi

(Signorellian

dScarab

ino)

PeE

I0e

25S

Sf34

� Se42

� SMulinia

edulis(K

ingan

dBroderip,1

831)

EI

0e30

SSf

52.7

� Se55

.5� S

a

Mesod

esmamactroide

s(Ree

ve,1

854)

EI

0e20

SSf

23� Se41

� SSo

lentehu

elch

us(H

anley,

1842

)E

I10

e18

SSf

23� Se39

� Sa

Macom

a(P.)urug

uayensis(Smith,1

885)

EI

18e70

SD

29� Se39

� Sa

Tagelus(T.)pleb

eius

(Ligthfood

,178

6)P

I0e

10S

Sf42

� Ne54

� S

(con

tinu

edon

next

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The faunal composition of bivalves and gastropods shows thatmarine species predominate over estuarine species (e.g. Heleobiaaustralis). They mainly are species with active locomotion asepifaunal gastropods and infaunal bivalves. Bivalves from Pleisto-cene deposits are mainly rocky sediment and filter feeders,whereas for the Holocene and modern, sandy sediment andsuspension feeders are predominant. Among gastropods, theepifaunal type, common in sandy sediments, is predominant, withfilter feeders mainly present in Pleistocene deposits and carnivoresin Holocene-modern ones (Fig. 6) (Tables 5 and 6) (Fig. 7).

Table 5 (continued )

Bivalvia Salinity Life habit Depth (m) Substrate Trophic type Distribution area

Pitar (P.) rostratus (Philippi, 1844) E I 10e100 S Sf 22�Se38.7�Sa

Amiantis purpurata (Lamarck, 1856) E I 0e20 S Sf 19�Se43�SCorbula (C.) patagonica (d’Orbigny, 1846) E I 15e90 S Sf 23�Se43�SCorbula (C.) lyoni (Pilsbry, 1897) E I 11e67 S Sf 19�Se43�SBarnea lamellosa (d’Orbigny, 1846) E I 15e150 H Sf 34�Se43�S

a Taxa found in the studied area.

Table 6Ecological requirements and distribution of gastropods: Ep ¼ epifaunal, I ¼ infaunal; H ¼ hard, S ¼ soft; C ¼ carnivorous, D ¼ detritivorous, He ¼ herbivore, Sf ¼ suspension feeder; O ¼ oligohaline (3e8&), M ¼mesohaline (8e18&); P ¼ polihaline (18e30&); E ¼ euhaline (>30e35&).

Gastropods Salinity Lifehabit

Depth Substrate Trophictype

Distribution area*

Diodora (D.) patagonica (d’Orbigny, 1841) E Ep 0e15 H He 11�Ne45�SLucapinella henseli (Martens, 1900) E Ep 0e55 H He 23�Se53�STegula (A.) patagonica (d’Orbigny, 1835) E Ep 0e57 H He 23�Se54�SCalliostoma coppingeri (E.A. Smith, 1880) E Ep 13e86 S He 30�Se44.21�SHeleobia australis (d’Orbigny, 1835) O, P, M Ep 0e60 M He 24�Se41�SBostrycapulus odites (Collin, 2005) E Ep 0e46 H Sf 25�Se45.8�SCrepidula argentina Simone (Pastorino and Penchaszadeh, 2000) E Ep 30e50 H Sf 38�Se41.03�SNotocochlis isabelleana (d’Orbigny, 1840) E I 0e113 S C 22.4�Se42.58�STrophon varians (d’Orbigny, 1841) E Ep 0e50 H C 32�Se40�SUrosalpinx cala (Pilsbry, 1897) E Ep 28e28 H C 32�Se41�SZidona dufresni (Donovan, 1823) E Ep 10e90 S C 23�Se42�SAdelomelon (P.) brasiliana (Lamarck, 1811) E Ep 8e70 S C 23�Se52�SOdontocymbiola magallanica (Gmelin, 1791) E Ep 10e200 M C 35�Se55.2�SOlivella (O.) tehuelcha (Dúclos, 1835) E Ep 15e57 S C 23.69�Se43�SOlivancillaria urceus (Röding, 1798) E Ep 5e50 S C 19�Se42�SOlivancillaria carcellesi Klappenbach, 1965 E Ep 0e22 S C 23�Se42.5�SMarginella martini (Petit, 1853) E Ep 10e80 S C 22.93�Se42�SBuccinanops moniliferum (Kiener, 1834) E Ep 0e50 S C 35�Ne42�SBuccinanops cochlidium (Dilwyn, 1817) E Ep 5e66 S C 23�Se42.58�SBuccinanops globulosum (Kiener, 1834) E Ep 0e6 S C 35�Se46�SBuccinanops uruguayense (Pilsbry, 1897) Ep 15e45 S C 24�Se42�SParvanachis isabellei (d’Orbigny, 1839) E Ep 10e65 C C 30�Se54�SSiphonaria lessoni (Blainville, 1824) E Ep 0 H He 32�Se55.22�S

* Range of distribution with the upper limit in higher latitudes.

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Fig. 2. Distribution of the Pleistocene and Holocene deposits in the study.

Fig. 3. Bivalvia taxa from Quaternary marine deposits in Bahia San Blas. a. External view, b. in(L ¼ 9.62) (MLP:33.410, Holocene); 2, Ennucula grayi (d’Orbigny) (L ¼ 8.86) (MLP:33.411, Horodriguezi (d’Orbigny) (L ¼ 9.68) (MLP:33.994, Holocene); 5, Aequipecten tehuelchus (d’Orbi(MLP: 33.412, Pleistocene); 7, Crassostrea rhizophorae (Guilding) (L ¼ 21.80) (MLP: 33.998,Mesodesma mactroides Reeve (L ¼ 43.54) (MLP: 33.403, Holocene); 10, Ostreola equestris(MLP:33.403); 12, Diplodonta patagonica (d’Orbigny) (L ¼ 14.99) (MLP: 33.402, Holocene); 1Lamarch (L ¼ 22.42) (MLP:33.415, Pleistocene); 15, Corbula patagonica d’Orbigny (L ¼ 1(MLP:33.400, Holocene); 17, Mactra guidoi Signorelli and Scarabino (L ¼ 23.05) (MLP: 33.406Mulinia edulis (King and Broderip) (L ¼ 24.61) (MLP:33.408, Holocene); 20, Corbula Iyoni P(MLP: 33.995, Pleistocene); 22, Macoma (P.) uruguayensis (Smith) (L ¼ 27,50) (MLP:33.404Trachycardium muricatum (Linné) (L ¼ 31.69) (MLP: 33.417, Pleistocene); 25, Crassostrea g(L ¼ 41.25) (MLP: 33.414, Pleistocene); 27, Amiantis purpurata d’Orbigny (L ¼ 46.98) (MLP:

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In the cluster analysis, Holocene bivalves were more similar tomodern than to Pleistocene ones. However, Pleistocene gastropodswere similar to Holocene ones, and both differ from modern ones(Fig. 8).

3.2. The Pleistocene of Bahía San Blas

Eleven sites were analyzed for the Pleistocene, in which 33 taxawere recorded (17 bivalves and 16 gastropods). Five of the elevensites were studied from a lithological and paleoecological point ofview. Site 25, is located approximately 50 km from the village ofBahía San Blas. This outcrop is composed of 2.5 m of gravel sedi-ments with a sandy silt matrix and a homogeneous grey colour(Fig. 9) (Fucks et al., 2012). The mollusc fauna is composed of Pitarrostratus, Glycymeris longior (bivalves), Buccinanops cochlidium, andOlivancillaria urceus (gastropods).

The second Pleistocene deposit is site 22, near Salina del Inglés,26.6 km from the village of Bahía San Blas. It is one of the mainevaporite deposits in the area, ovoid-shaped, 5.5 km long E-Wdirection and 4.8 kmwide, and composed of silty sediments, brownto green, with gypsum crystals and mollusc shells (Etcheverríaet al., 2006). At the western end there is a selenite gypsum layernearly 50 cm thick composed of slightly carbonatic, brown claymud (Del Blanco et al., 2005). In this site, a 50 cm unexposed profilewas found, with articulated Pitar rostratus in life position (Fig. 10).Nineteen taxa were observed (10 bivalves and 9 gastropods) ina good state of preservation and with gypsum precipitation on theshells. Among the most abundant were Pitar rostratus (bivalve),Olivancillaria urceus, Tegula patagonica and Zidona dufresnei

ternal view. L ¼maximum antero-posterior length in mm.1, Nucula (N.) nucleus (Linné)locene); 3, Mytilus edulis Linné (L ¼ 25.07) (MLP:33.409, Modern); 4, Brachidontes (B.)gny) (L ¼ 54.96) (MLP:33.996, Pleistocene); 6, Ostrea puelchana d’Orbigny (L ¼ 29.90)Pleistocene); 8, Tagelus (T.) plebeius (Ligthfoot) (L ¼ 61.05) (MLP:33.418, Holocene); 9,(Say) (L ¼ 29.52) (MLP: 33.413, Holocene); 11, Glycymeris (G.) longior (L ¼ 19.43)

3, Solen tehuelchus d’Orbigny (L ¼ 58.70) (MLP:33.401, Holocene); 14, Plicatula gibbosa1.80) (MLP: 33.401, Holocene); 16, Diplodonta vilardeboana (d’Orbigny) (L ¼ 12.33), Pleistocene); 18, Mactra isabelleana d’Orbigny (L ¼ 28.44) (MLP: 33.405, Modern); 19,ilsbry (L ¼ 11.58) (MLP: 33.999, Holocene); 21, Carditamera plata (Inhering) (L ¼ 5.30), Holocene); 23, Barnea lamellosa (d’Orbigny) (L ¼ 32.69) (MLP: 33.993, Modern); 24,igas (Thunberg) (L ¼ 35.70) (MLP: 33.997, Modern); 26, Pitar (P.) rostratus (Philippi)33.992, Modern).

Fig. 4. Taxa of gastropods from marine Quaternary deposits in Bahia San Bias. A. Abapertural view; b. Apertural view. H ¼ maximum dorso-ventral height in mm. 1, Heleobiaaustralis (d’Orbigny) (H ¼ 6.51) (ML: 34.038,Holocene); 2, Calliostoma coppingeri (Smith) (H ¼ 7.36) (MLP: 34.046, Pleistocene); 3, Bostrycapulus odites (Collin) (H ¼ 18.84) (MLP:34.025,Holocene); 4, Notocochlis isabelleana (d’Orbigny) (H ¼ 16.15) (MLP: 34.035, Pleistocene); 5, Diodora (D.) patagonica (d’Orbigny) (H ¼ 40.11) (MLP: 34.026, Modern); 6,Parvanachis isabellei (d’Orbigny) (H ¼ 10.58) (MLP: 34.045, Modern); 7, Tegula (A.)patagonica (d’Orbigny) (H ¼ 13.05) (MLP: 34.033); 8, Crepidula argentina Simone, past.& Pen,(H ¼ 15.09) (MLP: 34.028, Holocene); 9, Lucapinella henseli (Martens) (H ¼ 26.60) (MLP; 34.027, Modern); 10, Olivella (O.) tehuelcha (Duclos) (H ¼ 11.71) (MLP: 34.036, Holocene); 11,Buccinanops moniliferum (Kiener) (H ¼ 34.46) (MLP: 34.040, Modern); 12, Trophon varians (d’Orbigny) (H ¼ 41.51) (MLP: 34.037, Modern); 13, Marginella martini (Petit) (H) (MLP:34.044, Pleistocene); 14, Buccinanops uruguayense (Pilsbry) (H ¼ 22.53) (MLP: 34.034, Holocene); 15, Buccinanops cochlidium (Dillwyn) (H ¼ 64.28) (MLP:34.032, Holocene); 16,Olivancillaria urceus (Röding) (H ¼ 48.37) (MLP: 34.042, Pleistocene); 17, Olivancillaria carcellesi Klappenbach (H ¼ 29.03) (MLP: 34.039, Modern); 18, Urosalpinx cala (Pilsbry)(H ¼ 13.21) (MLP: 34.041, Pleistocene); 19, Buccinanops globulosum (Kiener) (H ¼ 17.84) (MLP: 34.043, Modern); 20, Zidona dufresnei (Donovan) (H ¼ 90.92) (MLP: 34.029,Holocene); 21, Odontocymbiola magallanica (Gmelin) (H ¼ 80.40) (MLP: 34.030, Holocene); 22, Adelomelon (P) brasiliana (Lamarck) (H ¼ 120.24) (MLP: 34.031, Holocene).

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(gastropods), micro-molluscs Nucula nucleus, Carditamera plata,Corbula patagonica (bivalve), and Heleobia australis (gastropod).

Sites 23 and 24 correspond to the Pleistocene of Faro SegundaBarranca. This outcrop has two levels: the lower level (site 24)comprises 2m of yellow-brown sandy silt sediments with boulders.Mollusc fauna includes T. patagonica, Bostrycapulus odites, Uro-salpinx cala, Parvanachis isabellei, Buccinanops cochlidium and Buc-cinanops globulosus (gastropods), and Mytilus edulis andBrachidontes rodriguezi (bivalves) (Fig. 11). The upper level (site 23)is composed of clast-supported gravel, with sand and

Fig. 5. Diversity (Shannon index) of the molluscan fauna in the localities of differentages.

conglomerated sand strata on the surface. The overall colour is grey,with clearly defined parallel to low-angle cross bedding, showinga slight southern inclination and partial clustering in some strata.Fossil remains include T. patagonica, B. odites, Crepidula sp., Olivellatehuelcha (gastropods) and Pitar rostratus, M. edulis, Brachidontesrodriguezi, Aequipecten tehuelchus, Ostreola equestris, Ostrea puel-chana and Pitar rostratus (bivalves) (Fig. 12).

A Pleistocene ridge at an altitude of 33 m a.s.l., 10 km from thevillage of Cardenal Cagliero (40�39018.1000 S/62�44053.6600 W), wasanalyzed (site 26). It is a quarry of clustered gravel probably olderthat MIS 5e (Fucks et al., 2012). Pitar rostratus (bivalve) and Zidonadufresnei (gastropod) were found.

3.3. The Holocene of Bahía San Blas

Large quantities of diverse gastropods and bivalves were foundin the Holocene beach ridges. Seven sites were analyzed and 31taxa were collected (18 bivalves and 13 gastropods) in a good stateof preservation, in some cases articulated. All Holocene deposits arelocated at Isla Jabalí, and are represented by two geofeatures: beachridges (Fig. 13) and tidal plains (Fig. 14). Beach ridges (sites 11 and14) deposits are well-stratified gravels (Fig. 10Ba, c) and sands(Fig. 10Bb, d and C) with shell remains. Among the most commontaxa are Pitar rostratus, Amiantis purpurata, Glycymeris longior,

Fig. 6. Proportion of bivalves and gastropods according to their substrate type, trophic type and mode of life.

Fig. 7. Dendrogram of Quaternary deposits based on BrayeCurtis similarity index inbivalves.

Fig. 8. Dendrogram of Quaternary deposits based on BrayeCurtis similarity index ingastropods.

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Fig. 9. Outcrop of gravel littoral beach in Bahia San Blas (Site 25).

Fig. 10. General view of Pleistocene site Salina del Ingles (site 22) showing a detailedsector with articulated Pitar rostratus.

Fig. 11. Lower level of site 24, Faro Segunda Barrance (MIS 5e).

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Ostrea equestris (bivalves) and T. patagonica, B. odites, Buccinanopsglobulosus (gastropods). In the tidal plains (sites 9, 10, 12, 13, and15), which are lower energy environments, Heleobia australis(gastropod) and Corbula patagonica and Tagelus plebeius (bivalves)are common, and inmost of these deposits, articulated T. plebeius inlife position can be observed (Fig. 12).

3.4. Modern fauna

Beaches of Bahía San Blas are made of boulders and have a verypronounced slope, thus forming a reflective beach (Trebino, 1987;Codignotto, 1997; Cuadrado and Gomez, 2010) with molluscremains (Fig. 15).

At the Isla Jabalí beaches, six sites were analyzed and 24 taxawere found (10 gastropods and 14 bivalves) including B. odites(gastropods) and Brachidontes rodriguezi, Ostrea equestris, Pitarrostratus, Amiantis purpurata and Crassostrea gigas (bivalves), beingparticularly noteworthy Mesodesma mactroides, Solen tehuelchus,Barnea lamellosa and C. gigas. At the beaches of Faro SegundaBarranca, two sites were analyzed and 16 taxa were recorded (10gastropods and 6 bivalves), being the most abundant B. odites,Trophon varians and T. patagonica (gastropods), and Ostreolaequestris (bivalve).

3.5. Mollusc associations

In order to assess the degree of similarity (or dissimilarity)among the set of samples from both areas, the UPGMAmethod wasused, together with the BrayeCurtis Index. Two large samplegroups, A and B, were defined according to the cluster analysis.Group A mainly contains Pleistocene and modern sites, with theexception of two Holocene sites. All belong to high energy envi-ronments. This group is divided into four sub-groups. Sub-group A1stands out for having three Pleistocene sites and three modernsites, including all the sites of Faro Segunda Barranca. Sub-group A2contains three Pleistocene sites that belong to the continental partof Bahía San Blas, of which two (sites 25 and 26) are located at thehighest altitudes. Sub-group A3 gathers three Pleistocene and fourmodern sites from Isla Jabalí, but did not include site 16. Group Bgathers only Holocene sites, all of which belong to low-energyenvironments (Fig. 16).

According to the Correspondence Analysis (CA), the sites can bedivided into groups A and B. Group A is composed of continentalPleistocene sites and modern sites of Isla Jabalí. Group B comprisesall Holocene sites in low-energy environments. In the upper regionof the graph, the sites located at the top, 22 and 15, correspond tothe two Pleistocene sites considered to be older thanMIS 5e. Site 17is located in the lower region of the graph, close to group A and sites7 and 8, which belong to modern Faro Segunda Barranca sites(Fig. 17).

4. Discussion

For the Pleistocene, 33 taxa were found (17 bivalves and 16gastropods), mostly represented by the gastropods Brachidontesrodriguezi, M. edulis, Ostreola equestris, Ostrea puelchana, Pitar ros-tratus, and Amiantis purpurata, and the gastropod Buccinanopsglobulosus. For the Holocene deposits, 31 taxa were registered (18bivalves and 13 gastropods), with the predominant bivalves beingPitar rostratus and Corbula patagonica, and the gastropods Heleobiaaustralis, T. patagonica, and Zidona dufresnei. In general, the Pleis-tocene and the Holocene molluscs of Bahía San Blas show nosignificant differences in composition. However, the presence ofthe bivalve Crassostrea rhizophorae in the late Pleistocene (MIS 5e)is a clear sign of warmer conditions. This is also seen in the

Fig. 12. Outcrops of Pleistocene gravels (MIS 5e) in Faro Segunda Barranca (Site 23).

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Pleistocene deposits of Bahía Blanca, 285 km farther south (Chaaret al., 1992). In contrast, no warm climate molluscs, currentlypresent in lower latitudes, were recorded during the Holocene. Inthis regard, the Holocene fauna from Bahía San Blas contrasts withthe results of previous studies in the northeast region of theprovince of Buenos Aires, and in Bahía Blanca (Farinati, 1985;Aguirre, 1993b; Aguirre and Whatley, 1995), in which largeramounts of gastropods and bivalves were reported compared to thePleistocene record (MIS 5e). The abovementioned studies relatethose differences to the Climatic Optimum or Hypsithermal (mid-Holocene), a paleoclimatic event that occurred in the NorthernHemisphere, with higher SST and warmer conditions compared tothe present (e.g. Lutaenko, 1993; Hjort et al., 1995). However, theresults of this study area do coincide with other research carried

Fig. 13. Outcrops of Holocene (MIS 1) b

out along Central Patagonia (Pastorino, 1991, 1994, 2000; Aguirre,2003; Aguirre et al., 2005, 2006) in which no record of faunalchanges related to the Hypsithermal were found.

Within the Holocene fauna, the presence of articulated T. ple-beius in life position is worthy of mention. T. plebeius is an infaunaleurohaline species, commonly found in large quantities in Holo-cene deposits in intertidal areas of estuaries on the Atlantic coast,from North Carolina (34� N) to SanMatías Gulf (41�S) (i.e. Gutiérrezand Iribarne, 1999; Bushek et al., 2008). In the province of BuenosAires, episodes of mass mortality have been recorded (Schnacket al., 1982; Farinati et al., 1992; Golfieri et al., 1998; Iribarneet al., 1998; De Francesco and Zárate, 2001).

In addition, Mesodesma mactroides, one of the most commonmodern species in the Bahía San Blas area, that lives today on sandy

each ridges in Isla Jabali (Site 11).

Fig. 14. Holocene deposit from Isla Jabali (MIS1) with articulated Tagelus plebeiusfound in life position (Site 12).

Fig. 15. Beach and cliff at the base covered by dunes rampant in Faro Segunda Barranca(Site 8).

Fig. 16. Dendrogram of the localities, based on BrayeCurtis index (cluster analysis).

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beaches from 23�S (Rio de Janeiro, Brazil) to near 40�S (Isla Jabalí)(i.e. Rios, 1994; Fiori and Morsan, 2004; Fiori and Defeo, 2006), wasnot found in the Holocene ridges analyzed in this study, despitebeing mentioned in an unspecified area for this period by Aguirreand Farinati (2000). In Holocene archaeological sites of thePampean littoral, Mesodesma mactroides was not found to beconsumed by hunteregatherer aborigines (Bonomo, 2007).Nevertheless, in Holocene shell middens of the coastal region ofBahía San Blas, this species has been mentioned as amongst themost abundant (Zudimendi, 2007; Aldazabal et al., 2010). Hence,although M. mactroides was not found in this study, it has beenpresent in the region, probably with a discontinuous distributionalong the coast of the Buenos Aires province. Similarly, Solentehuelchus and B. lamellosa have not been found in the studiedridges, but have been recorded in other Holocene deposits of theBuenos Aires Province between Sierra Grande and Bahia Blanca(Aguirre and Fucks, 2004).

The appearance of C. gigas on the current coast of Isla Jabalí isthe result of anthropic modification. This Japanese species wasbrought to Argentina and introduced into the area of Bahía Anegada(39�500S/40� 400S) in 1981 for farming purposes, and in 2005 themost southern natural population in the country was recorded in ElCondor beach resort (41�S).

5. Conclusions

For the Quaternary of Bahía San Blas, 50 taxa were recorded (27bivalves and 23 gastropods) in a good state of preservation, and insome cases, articulated. The highest diversity indexes correspondmainly to modern sites, followed by Pleistocene sites. Holocenesites have the lowest diversity, except for two. Marine species ofbivalves and gastropods prevail over estuarine species, beingmainly free locomotion species as epifaunal gastropods andinfaunal bivalves.

Among bivalves, rocky sediment and filter-feeder bivalvesprevail in Pleistocene deposits, whereas sandy sediment andsuspension feeders are predominant in Holocene and moderndeposits. On the other hand, epifaunal gastropods typical of sandysediments and filter feeders are predominant in Pleistocenedeposits, whereas mobile carnivores prevail in Holocene andmodern deposits. It remains unclear if these changes in thepredominance of different trophic groups is related to the presenceof different sub-environments within the study area or are due toregional changes over time.

Two mollusc associations were defined in Bahía San Blas (A andB) depending on the type of environment: high energy (stormrange) or low-energy (tidal plains), and not on their age. Sites 22and 25 are different from the rest of the Pleistocene sites: theformer due to its species richness, and the latter for being one of theoldest, along with site 26. Both sites yielded the largest numbers ofPitar rostratus. During the Pleistocene, warmer conditions favouredthe entrance of C. rhizophorae, currently inhabiting lower latitudes.The large number of articulated T. plebeius in life position indicatesa low-energy environment of fine sediments and silty sand, bestseen in Holocene deposits. For the Holocene, no warm water taxacurrently living in lower latitudes was found.

Modern sites from Faro Segunda cluster with Pleistocene sites ofBahía San Blas, but separate from modern sites of Isla Jabalí in theCorrespondence Analysis (CA). This difference is due to the largenumber of Trophon varians in Faro Segunda Barranca beaches.

Four modern taxa were not found in either Pleistocene orHolocene deposits: Mesodesma mactroides, Solen tehuelchus, B.lamellosa and C. gigas. However, although Mesodesma mactroideswas not found in this study, it has been reported in archeologicalsites (Holocene shell middens) in the south of Bahía San Blas.

Fig. 17. Correspondence analysis of sites based on the abundance of taxa. Most sites conform to two groups A and B.

M.P. Charó et al. / Quaternary International 301 (2013) 135e149 147

Meanwhile, C. gigaswas introduced into the Argentine seas of BahíaAnegada and has proliferated over the last few years along thesouthern coast of the Buenos Aires Province. From the 50 taxafound in Quaternary deposits in the study area, 14 (8 bivalves and 6gastropods) are recorded since the Pleistocene.

The last marine transgressive events have been recorded inBahía San Blas area. MIS 1 and MIS 5e (last interglacial) are wellrepresented, while other older events, MIS 7 and/or MIS 9, are notso clearly represented. The �MIS 7 events are represented byelongated geofeatures, characterized by scarce marine fauna andmaximum altitudes of 30 m a.s.l. The Late Pleistocene (MIS 5e) iswell developed inland, where typical outcrops can be found withinmaximum altitudes of 10 m a.s.l.

MIS 1 is recorded exclusively on Isla Jabalí, with continuousbeach strands, beach ridges and shallow tidal plains at maximumaltitudes of 6 m a.s.l. as the most typical geofeatures. For both MIS 1and MIS 5e, the characteristic marine molluscs are bivalves andgastropods. Among these, C. rhizophorae, today living at lowerlatitudes, is an excellent indicator of warmer conditions during theLate Pleistocene (MIS 5e). Nevertheless, as a whole, molluscs do notdenote warmer environments in the study area that could berelated to the global event known as the Climatic Optimum, orHypsithermal. Based on the quantitative and qualitative analysischanges of Pleistocene and Holocene molluscs, are mostly due tothe presence of sub-environments and local, rather than global,environmental changes that affect ecological parameters.

Acknowledgments

The authors thank Lic. Florencia Pisano (FCNYM, CONICET) forher collaboration during fieldwork; Prof. Mario Giaconi (FCNYM,UNLP, CONICET) for logistic support, Dr. Mikel Zudimendi (UNLP,CONICET), who provided the bibliography which enriched thisstudy in an interdisciplinary way and Dra. Cecilia Deschamps forhelp in the editing of the final version.

References

Aguirre, M.L., 1990. Holocene macrobenthic molluscan associations from north-eastern Buenos Aires Province, Argentina. Quaternary of South America &Antarctic Peninsula 7, 161e195.

Aguirre, M.L., 1993a. Caracterización faunística del Cuaternario marino del norestede la Provincia de Buenos Aires. Revista de la Asociación Geológica Argentina 47(1), 31e54.

Aguirre, M.L., 1993b. Palaeobiogeography of the Holocene molluscan fauna fromNortheastern Buenos Aires Province, Argentina: its relation to coastal evolutionand sea level changes. Palaeogeography, Palaeoclimatology, Palaeoecology 102,1e26.

Aguirre, M.L., 1993c. Type specimens of Quaternary marine Gastropods fromArgentina. Ameghiniana 30 (1), 23e38.

Aguirre, M.L., 2002. Optimo climático en el Holoceno marino de la Argentina:evidencias Malacológicas. Actas XV Congreso Geológico Argentino, Calafate.Tomo I, 548e553.

Aguirre, M.L., 2003. Late Pleistocene and Holocene palaeoenviroment in Golfo SanJorge, Patagonia: molluscan evidence. Marine Geology 194, 3e30.

Aguirre, M.L., Farinati, E.A., 2000. Moluscos del Cuaternario Marino de la Argentina.Boletín de la Academia Nacional de Ciencias 64, 235e333.

Aguirre, M.L., Fucks, E.E., 2004. Moluscos y Paleoambientes del Cuaternario Marinoen el sur de Entre Ríos y Litoral Bonaerense. In: Aceñolaza, F. (Ed.), Temas de laBiodiversidad del Litoral Fluvial Argentino. INSUGEO, Miscelanea, vol. 12,pp. 55e70.

Aguirre, M.L., Whatley, R.C., 1995. Late Quaternary Marginal marine deposits fromnorth-eastern Buenos Aires Province, Argentina: a review. Quaternary ScienceReviews 14, 223e254.

Aguirre, M.L., Sirch, Y.N., Richiano, S., 2005. Late Quaternary molluscan assemblagesfrom the coastal area of Bahía Bustamante (Patagonia, Argentina): paleoecologyand paleoenviroments. Journal of South American Earth Sciences 20, 13e32.

Aguirre, M.L., Richiano, S., Negro Sirch, Y., 2006. Palaeoenvironments and palae-oclimates of the Quaternary molluscan faunas from the coastal area of BahíaVera-Camarones (Chubut, Patagonia). Palaeogeography, Palaeoclimatology,Palaeoecology 229, 251e286.

Aldazabal, V., Eugenio, E., Silveira, M., 2010. Arqueología del sector costero al sur debahía San Blas: sitio Las Olas 11. In: Bárcena, J.R., Chiavazza, H. (Eds.), Arqueo-logía Argentina en el Bicentenario de la Revolución de Mayo. Facultad deFilosofía y Letras de la Universidad Nacional de Cuyo y INCIHUSA-CONICET,Mendoza, pp. 301e308. Tomo I, ISBN: 978-987-9126-84-2.

Ambrosini, G.L., 1984. Geomorfología de la Isla Jabalí, Departamento de Patagones,Provincia de Buenos Aires. 9� Congreso Geológico Argentino (San Carlos DeBariloche) Actas 3, 497e512.

Ameghino, F., 1889. Contribución al conocimiento de los mamíferos fósiles de laRepública Argentina. Actas de la Academia Nacional de Ciencias (Córdoba) 6, 1e1027.

Ameghino, F., 1898. Primera sinopsis geológico-paleontológica. 2 Censo de laRepública Argentina 1,111e255.

Ameghino, F., 1908. Las formaciones sedimentarias de la región litoral de Mar delPlata y Chapadmalán. Anales del Museo Nacional de Historia Natural 10, 343e428.

Balech, E., Ehrlich, M., 2008. Esquema biogeográfico del mar Argentino. Revista deInvestigación Desarrollo Pesquero 19, 45e75.

Barreto, A.M.F., Becerra, F.H.R., Suguio, K., Batumi, S.H., Yee, M., Paiva, R.P.,Munita, C.S., 2002. Late Pleistocene marine terrace deposits in northeasternBrazil: sea e level change and tectonic implications. Palaeogeography, Palae-oclimatology, Palaeoecology 179, 57e69.

Bastida, R., Zamponi, M., Bremen, C., Roux, A., Genzano, G., Elías, G., 2007. Lascomunidades bentónicas. El mar Argentino y sus recursos pesqueros 5, 91e125.

Bonomo, M., 2007. El uso de los moluscos marinos por los cazadores e recolectoresPampeanos. Revista de Antropología Chilena 39 (1), 87e102.

Bujalesky, G.G., Isla, F.I., 2006. Depósitos cuaternarios de la costa atlántica fueguina,entre los Cabos Peñas y Ewan. Revista de la Asociación Geológica Argentina 61(1), 81e92.

Bushek, D., Landau, B., Scarpa, E., 2008. Perkinsus chesapeake in stout razor clamsTagelus plebeius from Delaware Bay. Diseases of Aquatic Organisms 78, 243e247.

Camacho, H., 1966. Paleontografía bonaerense. III. In: Borrello, A.V. (Ed.), Inverte-brados, vol. 3. Comisión de Investigaciones Científicas, p. 159.

Carcelles, A., 1944. Catálogo de los Moluscos Marinos de Puerto Quequén. Revistadel Museo de La Plata (N. S.). Zoología 3, 233e309.

Cárdenas, J., Gordillo, S., 2009. Late Quaternary molluscan assemblages from Tierradel Fuego (southern South America): a taphonomic analysis. Andean Geology36, 81e93.

Caruso Jr., F., Sugui, K., Nakamuras, T., 2000. The Quaternary geological history ofthe Santa Catarina Southeastern region (Brazil). Annales Academia BrasiliaCiences 72 (2), 257e270.

M.P. Charó et al. / Quaternary International 301 (2013) 135e149148

Castellano, Z., 1979. Novedades de micromoluscos en la Plataforma Argentina.(Mollusca, Gastropoda). Neotropica 25 (73), 91e96 (La Plata).

Castellano, Z., 1981. Nuevos registros sobre micromoluscos. Geotrópica 27 (78),147e149 (La Plata).

Castellanos, Z., 1967. Catálogo de los Moluscos Marinos Bonaerenses. Anales de laComisión de Investigaciones Científicas 8, 365.

Chaar, E., Farinati, E.,1988. Evidencias paleontológicas y sedimentológicas de un nivelmarino pleistocenico en Bahía Blanca, provincia de Buenos Aires, Argentina.Segunda Jornadas Geologicas Bonaerenses, Bahia Blanca. Actas, 47e54.

Chaar, E., Farinati, E., Aliotta, S., Tassone, A., 1992. Pleistoceno marino al sur de laciudad de Bahía Blanca. 3ras Jornadas Geológicas Bonaerense (La Plata) Acta, pp.59e62.

Cionchi, J., 1987. Depósitos marinos cuaternarios de Bahía Bustamente, provincia delChubut. Revista de la Asociación Geológica Argentina 42 (1e2), 61e72.

Codignotto, J.O., 1997. Geomorfología y Dinámica costera. El mar Argentino y losrecursos pesqueros 1, 89e105.

Codignotto, J.O., Aguirre, M.L., 1993. Coastal evolution in sea level and molluscanfauna in northeastern Argentina during the Late Quaternary. Marine Geology110, 163e175.

Codignotto, J.O., Marcomini, S.C., Santillana, S.N., 1988. Terrazas marinas entrePuerto Deseado y Bahía Bustamante, Santa Cruz, Chubut. Revista de la Aso-ciación Geológica Argentina 43, 43e50.

Cohen, A.L., Parkington, J.E., Brundrit, G.B., Van der Merwe, N.J., 1992. A Holocenemarine climate record in mollusc shells from the Southwest African coast.Quaternary Research 38, 379e385.

Cuadrado, D.G., Gomez, E.A., 2010. Geomorfología y dinámica del Canal San BlasProvincia de Buenos Aires (Argentina). Latin American Journal of Sedimen-tology and Basin Analysis 17 (1), 3e16.

Cuerda, J., Vicens, D., Gracia, F., 1991. Malacofauna y estratigrafía del PleistocenoSuperior marino de San Real (Santa Margalida, Mallorca). Bolletí de la Societatd’ Història Natural de los Balears 34, 99e108.

Darwin, C., 1846. Geological Observations on South American. Smith Elder and Co.,London, 279 pp.

De Diego-Forbis, T., Douglas, R., Gorsline, D., Nava e Sanchez, E., Mack, L., Banner, J.,2004. Late Pleistocene (Last interglacial) terrace deposits, Bahía Coyote, BajaCalifornia Sur, Mexico. Quaternary International 120, 29e40.

De Francesco, C., Zárate, M., 2001. Bioturbaciones de Tagelus plebeius (Lightfoot,1786) (Mollusca: Bivalvia) en un ambiente estuárico holoceno (río Quequén,Buenos Aires, Argentina). Ameghiniana 38 (4), 467e470.

Del Blanco,M.,Marchionni, D., Romero, S., Cábana, C., 2005. Depósitos evaporíticos dela provincia de Buenos Aires. Geología y Recursos Minerales de la Provincia deBuenos Aires. XVI Congreso Geológico Argentino (La Plata) XXVII, pp. 417e444.

Dumas, B., Guérémy, P., Raffy, J., 2005. Evidence for sea level oscillating by the“characteristic thickness” of marine deposits from raised terraces of SouthernCalabria (Italy). Quaternary Science Reviews 24, 2120e2136.

D’Orbigny, A., 1834e1847. Voyage dans l’Amérique Méridionale. Mollusques 5 (3),758. atlas (Tome 9) Paris.

D’Orbigny, A., 1842e1844. Voyage dans l’Amérique Méridionale. Paléontologie 3 (4),152. Paris & Strasbourg.

Etcheverría, M., Folgueras, A., Dal Molín, C., 2006. Hojas Geológicas 4163-II/IV y I/III.Viedma y General Conesa, Provincias de Río Negro y Buenos Aires. ProgramaNacional de Cartas Geológicas de la República Argentina. SEGEMAR.

Farinati, E.A., 1985. Paleontología de los sedimentos marinos holocenos de losalrededores de Bahía Blanca, Provincia de Buenos Aires. Ameghiniana 21 (2e4),211e222.

Farinati, E.A., 1994. Micromoluscos (Gastropoda y Bivalvia) del Holoceno del área deBahía Blanca, Argentina. Ameghiniana 31 (4), 303e316.

Farinati, E.A., Camacho, H.H., 1980. Contribución al conocimiento de la malacofaunadel Cuaternario marino de los alrededores de Bahía Blanca, Provincia de BuenosAires, República Argentina. 2� Congreso Argentino de paleontología y Bio-estratigrafía y 1� Congreso Latinoamericano de Paleontología. Tomo III, pp.257e265.

Farinati, E.A., Aliotta, S., Ginsberg, S.S., 1992. Mass mortality of a Holocene Tagelusplebeius population in the Bahía Blanca Estuary, Argentina. Marine Geology106, 241e257.

Fiori, S., Defeo, O., 2006. Biogeographic patterns in life-history Traits of the yellowclam, Mesodesma mactroides, in sandy beaches of South America. Journal ofCoastal Research 22, 872e880.

Fiori, S., Morsan, E.M., 2004. Age and individual growth of Mesodesma mactroides(Bivalvia) in the southernmost range of its distribution. ICES Journal of MarineScience 61, 1253e1259.

Frenguelli, J., 1928. Observaciones geológicas en la región costanera sur de la Pro-vincia de Buenos Aires. Anales de la Facultad de Ciencias de la Educación 2, 1e145.

Frenguelli, J., 1950. Rasgos generales de la morfología y geología de la provincia deBuenos Aires. Publicación del Laboratorio de Ensayo de Materiales e Inves-tigaciones Tecnológicas (Lemit) 2 (33), 1e72.

Fucks, E., Aguirre, M., Deschamps, C., 2005. Late Quaternary continental and marinesediments at Northeastern Bonaerensian area (Argentina): fossil content andpalaeoenvironmental interpretation. Journal of South American Earth Sciences20 (1e2), 57e64.

Fucks, E.E., Aguirre, M.L., Richiano, S., Boretto, G., Zanchetta, G., Consoloni, I., Isola, I.,Pappalardo, M., bolini, A., 2009. Depósitos litorales en el sector continental delnorte del Golfo San Jorge. IV Congreso Argentino de Cuaternario y Geo-lomorfología y II Reunión sobre el Cuaternario de América del Sur, p. 114.

Fucks, E.E., Charó, M., Aguirre, M., Inati, E., 2011. Aspectos estratigráficos y geo-morfológicos del litoral patagónico bonaerense. XVIII Congreso GeológicoArgentino, pp. 275e276.

Fucks, E.E., Charó, M., Pisano, F., 2012. Aspectos estratigráficos y geomorfológicosdel sector oriental patagónico bonaerense. Revista de la Sociedad Geológica deEspaña 25 (1e2), 29e44.

Funder, S., Weidick, A., 1991. Holocene boreal mollusk in Greenland: palae-oceaonographic implications. Palaeogeography, Palaeoclimatology, Palae-oecology 85, 123e135.

Golfieri, G., Ferrero, L., Zárate, M., 1998. Tafonomía y Paleoecología de Tagelusplebeius (Lightfoot, 1786) (Mollusca, Bivalvia) En Sedimentos Holocenos Del RíoQuequén Grande, Provincia De Buenos Aires, Argentina. Ameghiniana 35 (3),255e264.

Gordillo, S., Coronato, A., Rabassa, J., 2005. Quaternary molluscan faunas from theisland of Tierra del Fuego after the Last Glacial Maximum. Scientia Marina 69(2), 337e348.

Goso Aguilar, C., 2006. Aspectos sedimentológicos y estratigráficos de los depósitoscuaternarios de la costa platense del Departamento de Canelones (Uruguay).Latin American Journal of Sedimentology and Basin Analysis 13 (1), 77e89.

Gutiérrez, J.L., Iribarne, O.O., 1999. Role of Holocene beds of the stout razor clamTagelus plebeius in structuring present benthic communities. Marine EcologyProgress Series 185, 213e228.

Hearty, P.J., 2002. Revision of the late Pleistocene stratigraphy of Bermuda. Sedi-mentary Geology 153, 1e21.

Hearty, P.J., Hollin, J.T., Conrad Neumann, A., O’Leary, M.J., Mc Culloch, M., 2007.Global sea-level fluctuation during the Last Interglaciation (MIS 5e). QuaternaryScience Reviews 26, 2090e2112.

Hjort, C., Mangerud, J., Adrielsson, L., Bondevik, S., Landvik, J., Salvigsen, O., 1995.Radiocarbon dated common mussels Mytilus edulis from eastern Svalbard andthe Holocene marine climatic optimum. Polar Research 14 (2), 239e243.

Iribarne, O.O., Valero, J.L., Martinez, M.M., Lucifora, L.O., Bachmann, S., 1998.Shorebird predation may explain the origin of Holocene beds of stout razorclams in life position. Marine Ecology Progress 167, 301e306.

Isla, F.I., Bujalesky, G., 2008. Coastal geology and morphology of Patagonia andFueguian Archipielago. In: Rabassa, J.R. (Ed.), The Late Cenozoic of Patagoniaand Tierra del Fuego. Sci. Publ. Ch, vol. 10, pp. 227e240.

Isla, F., Rutter, N., Schnack, E., Zárate, M., 2000. La trasgresión Belgranense enBuenos Aires. Una revisión a cien años de su definición. Cuaternario y CienciasAmbientales 1, 3e14.

Jones, K.B., Hodgins, G.W.L., Andrés, C.F.T., Etayo-Cadavid, M.F., 2010. Modelingmolluscan marine reservoir ages in a variable e upwelling environment. Palaios25, 126e131.

Kim, K.H., Tanaka, T., Nakamura, T., Nagao, K., Youn, J.S., Kim, K.R., Yun, M.Y., 1999.Palaeoclimatic and chronostratigraphic interpretations from strontium, carbonand oxygen isotopic ratios in molluscan fossils of Quaternary Seoguipo andShinyangri. Palaeogeography, Palaeoclimatology, Palaeoecology 154, 219e235.

Kitamura, A., Omole, H., Oda, M., 2000. Molluscan response to early Pleistocenerapid warning in the Sea of Japan. Geology 28, 723e726.

Lario, J., Zazo, C., Goy, J.L., Somoza, L., Hoyos, M., Silva, P.G., Hernandez eMolina, F.J.,1993. Los episodios marinos cuaternarios de la costa de Malaga (España).Revista Sociedad Geológica de España 6 (3e4), 42e46.

Lasta, L.M., Ciocco, C.F., Bremen, C.S., Roux, A.M., 1998. El mar Argentino y susrecursos pesqueros 2, 115e142.

Lutaenko, K.A., 1993. Climatic optimum during the Holocene and the distribution ofwarm e water mollusks in the Sea of Japan. Palaeogeography, Palae-oclimatology, Palaeoecology 102, 273e281.

Martinez, S., Verde, M., Ubilla, M., Perea, D., Guéréquiz, R., Piñeiro, G., 1997. Aso-ciaciones de moluscos fosiles del Cuaternario marino del Uruguay. Geo-cronología, tafonomía y paleoecología. In: “Boletín de Resumos XV CongressoBrasileiro de Paleontología”, p. 45.

Martinez, S., Ubilla, M., Verde, M., Perea, D., Rojas, A., Guérequiz, R., Piñeiro, G., 2001.Paleoecology and Geochronology of Uruguayan Coastal Marine Pleistocenedeposits. Quaternary Research 55, 246e254.

Massch, K., Sandweiss, D., Houk, S., 2001. Molluskan Evidence for Mid to LateHolocene Evolution of El Niño Conditions in Coastal Peru. Actas V REQUI/ICPLI,Lisboa Portugal, p. 353.

Mc Culloch, M.T., Esat, T., 2000. The coral record of last interglacial sea levels andsea surface temperature. Chemical Geology 169, 107e129.

Muhs, D.R., Rockwell, T.K., Kennedy, G.L., 1992. Late Quaternary uplift rates ofmarine terraces on the Pacific coast of North America, southern Oregon to BajaCalifornia Sur. Quaternary International 15e16, 121e133.

Muhs, D.R., Simmons, K.R., Kennedy, G.L., Rockwell, T.R., 2002. The last interglacialperiod on the Pacific coast of North America. Geological Society of AmericaBulletin 114, 569e592.

Murray-Wallace, C.V., Belperio, A.P.,1991. The last interglacial shoreline in Australiaea review. Quaternary Science Reviews 10, 441e461.

Murray-Wallace, C.V., Beu, A.G., Kendric, G.W., Brown, L.J., Belperio, A.P.,Sherwood, J.E., 2000. Palaeoclimatic implication of the occurrence of the arcoidbivalve Anadara trapezia (Deshayes) in the Quaternary of Australasia. Quater-nary Science Review 19, 559e590.

Neumann, A.C., Hearty, P.J., 1996. Rapid sea-level changes at the close of the lastinterglacial (substage 5e) recorder in Bahamian island. Geology 24, 775e778.

Oksanen, J., 2011. Multivariate analysis of ecological communities in R: VeganTutorial (online), actualización: 30 de Octubre 2011. http://cran.r-project.org/,http://vegan.rforge.r- project.org/ (consulta: 11 de julio del 2012).

http://cran.r-project.org/,%20http://vegan.rforge.r-%20project.org/http://cran.r-project.org/,%20http://vegan.rforge.r-%20project.org/

M.P. Charó et al. / Quaternary International 301 (2013) 135e149 149

Ortlieb, L., 1991. Quaternary shorelines along the northeastern Gulf of California:geocronological data and neotectonic implications. Geological Society ofAmerica, Special Paper, 254.

Ortlieb, L., Guzman, N., Candia, M., 1994. Moluscos litorales del Pleistoceno superioren el área de Antofagasta, Chile: Primeras determinaciones e indicacionespaleoceanográficas. Estudios Oceanológicos 13, 51e57.

Parham, P.R., Riggs, S.R., Culver, S.J., Mallinson, D.J., Wehmiller, J.F., 2007. Quaternarydepositional patterns and sea-level fluctuations, northeastern North Carolina.Quaternary Research 67, 83e99.

Pastorino, G., 1991. Lista preliminar de moluscos Cuaternarios de algunos yaci-mientos de Río Negro y Chubut, Argentina. Comunicaciones de la SociedadMalacologica del Uruguay 9 (56e57), 129e137.

Pastorino, G., 1994. Los moluscos gastrópodos de las Terrazas Marinas de Rio Negroy Chubut. Doctoral thesis, Facultad de Ciencias Exactas y Museo, La Plata, 205p.

Pastorino, G., 2000. Asociaciones de moluscos de las terrazas marinas Cuaternariasde Río Negro y Chubut, Argentina. Ameghiniana 37 (2), 131e156.

Pedoja, K., Regard, V., Husson, L., Martinod, J., Guillaume, B., Fucks, E., Iglesias, M.,Weill, P., 2011. Uplift of Quaternary shorelines in eastern Patagonia: Darwinrevisited. Geomorphology 127, 121e142.

Quezada, J., González, G., Dunai, T., Jensen, A., Juez-Larré, J., 2007. Alzamiento litoralPleistoceno del norte de Chile: edades 21Ne de la terraza costera más alta delárea de Caldera-Bahía Inglesa. Revista geológica de Chile 34 (1), 81e96.

Rabassa, J., Coronato, A., Ponce, J.F., 2009. La depresión de Bahía Inútil- Bahía SanSebastián (Tierra del Fuego, Argentina e Chile): Una conexión marina inex-istente durante el Pleistoceno Tardío e Holoceno. In: Salemme, M., et al. (Eds.),Arqueología de la Patagonia: una mirada del último confín, vol. 1, pp. 101e108.

Ragainia, L., Bianuccia, G., Cantalamessab, G., Valleric, G., Landinia, W., 2002.Paleoecology and paleobiogeography of fossil mollusks from Isla Isabela (Gal-ápagos, Ecuador). Journal of South American Earth Sciences 15, 381e389.

Rios, E.C., 1994. Seashells of Brazil, second ed. Fundação Universidade do RioGrande, Rio Grande. 492 p.

Rohling, E.J., De Rijk, S., 1999. The Holocene Climate Optimum and Last GlacialMaximum in the Mediterranean: the marine oxygen isotope record. MarineGeology 153, 57e75.

Rohling, E.J., Mayerwski, P.A., Challenor, P., 2003. On the timing and mechanism ofmillennial e scale climate variability during the last glacial cycle. ClimateDynamics 20, 257e267.

Rohling, E.J., Grant, K., Hemleben, C.H., Siddall, M., Hoogakker, B.A.A., Bolshow,Kucera, M., 2008. High rates of sea-level rise during the last interglacial period.Nature Geoscience 1, 38e42.

Rojas, A., Urteaga, D., 2011. Late Pleistocene and Holocene chitons (Mollusca, Pol-yplacophora) from Uruguay. Palaeobiogeography and palaeoenvironmentalreconstruction in mid-latitudes of the southwestern Atlantic. Geobios 44, 377e386.

Rosenberg, G., 2009. Malacolog 4.1.1: A Database of Western Atlantic Marine Mol-lusca (en línea), actualización: 20 de agosto de 2009. http://www.malacolog.org/ (consulta: 21 y 22 de julio de 2012).

Rostami, K., Peltier, W.R., Manzini, A., 2000. Quaternary marine terraces, sea e levelchanges and uplift history of Patagonia, Argentina: comparisons with predic-tions of the ICE - 4G (VM2) model of the global process of glacial isostaticadjustment. Quaternary Science Reviews 19, 511e514.

Roy, K., Jablonsky, D., Valentine, J.W., Rosenberg, G., 1998. Marine latitudinaldiversity gradients: test of causal hypothesis. Proceedings of the NationalAcademy of Sciences of the United States of America 95, 699e3702.

Rutter, N., Schnack, E., Del Río, L., Fasano, J., Isla, F., Radtke, U., 1989. Correlation anddating of Quaternary littoral zones along the Patagonian coast, Argentina.Quaternary Science Reviews 8, 213e234.

Rutter, N., Radtke, U., Schnack, E.J., 1990. Comparison of ESR and Amino Acid Data incorrelating and dating quaternary shorelines along the Patagonian coast,Argentina. Journal of Coastal Research 6 (2), 391e411.

Salvigsen, O., Forman, S., Miller, G.,1991. Thermophilousmolluscs on Svalbard duringthe Holocene and their paleoclimatic implications. Polar Research 11, 1e10.

Schellmann, G., 1998. Coastal development in Southern South America (Patagoniaand Chile) since the younger Middle Pleistocene e sea-level changes andneotectonics. In: Kelletat, D. (Ed.), German Geographical Coastal Research: TheLast Decade: Tübingen. Institute for Scientific Co-operation, Tübingen, IGUSonderband, pp. 289e304.

Schellmann, G., Radtke, U., 2000. ESR dating stratigraphically well-constrainedmarine terraces along the Patagonian Atlantic coast (Argentina). QuaternaryInternational 68e71, 261e273.

Schellmann, G., Radtke, U., 2003. Coastal terraces and Holocene sea-level changesalong the Patagonian Atlantic coast. Journal of Coastal Research 19 (4), 983e996.

Schnack, E.J., Fasano, J.L., Isla, F.I., 1982. The evolution of the Mar Chiquita Lagoon,province de Buenos Aires, Argentina. Proceedings Internacional Symposium onsea level changes in the last 15.000 years, magnitude and causes, Columbia,South Carolina, U.S.A. Actas, pp. 143e155.

Schnack, E.J., Isla, F.I., De Francesco, F.O., Fucks, E.E., 2005. Estratigrafía del Cua-ternario marino tardío en la Provincia de Buenos Aires. In: De Barrio, R.E.,Etcheverry, R.O., Caballé, M.F., Llambías, E. (Eds.), Geología y Recursos Mineralesde la Provincia de Buenos Aires. Relatorio, XVI Congreso Geológico Argentino,La Plata, Argentina. Capítulo X, pp. 159e182.

Shackleton, N.J., 1987. Oxygen isotopes, ice volumes and sea level. QuaternaryScience Reviews 6, 183e190.

Trebino, L., 1987. Geomorfología y evolución de la costa en los alrededores delpueblo de San Blas, Provincia de Buenos Aires. Revista de la Asociación Geo-lógica Argentina 42 (1e2), 9e22.

Tuccimei, P., Ginés, J., Detitala, M.C., Ginés, A., Gràcia, F., Fornós, J.J., Taddeucci, A.,2006. High precision U-series data from phreatic overgrowths on speleothems.Zeitschrift f}ur Geomorphologie 50 (1), 1e21.

von Ihering, H., 1907. Les Mollusques fossils du Tertiaire et du Cretacé de l’Arge-ntine. Anales del Museo Nacional de Buenos Aires 8 (2).

Wahnish, E., 1939. Noticia preliminar sobre la revisión de la fauna marina delPostpampeano. Con una nota sobre el Querandino en General Lavalle y revisiónde la especie “Labiosa (R.) canaliculata” Say. Physis 14 (46), 473e479.

Weiler, N.E., 2000. Evolución de los depósitos litorales en Bahía Anegada, Provinciade Buenos Aires, durante el Cuaternario tardío. Tesis Doctoral, Facultad deCiencias Exactas y Naturales, Universidad de Buenos Aires, 184 p.

Witte, L., 1916. Estudios Geológicos de la Región de San Blas (Partido de Patagones).Revista del Museo de La Plata 24, 7e99.

Yuan, L.X., Sun, L.G., Wei, G., Long, N., Xie, Z., Yuhong, W., 2011. 9.400 yr B. P.: themortality of mollusk shell (Mya truncata) at high Artic is associated witha sudden cooling event. Environmental Earth Science 63, 1385e1393.

Zazo, C., 1999. Interglacial sea levels. Quaternary International 55, 101e113.Zazo, C., Goy, J.L., Dabrio, C.J., Bardají, T., Hillaire-Marcel, C., Ghaleb, B., González-

Delgado, J.A., Soler, V., 2003a. Pleistocene raised marine terraces of the SpanishMediterranean and Atlantic coasts: records of coastal uplift, sea-level high-stands and climate changes. Marine Geology 194, 103e133.

Zazo, C., Goy, J.L., Hillaire e Marcel, C., Gonzalez Delgado, J.A., Soler, V., Chaleb, B.,Dabrio, C.J., 2003b. Registros de cambios de nivel del mar durante el Cua-ternario en las Islas Canarias occidentales (Tenerife y La Palma). EstudiosGeológicos 59, 133e144.

Zazo, C., Goy, J.L., Hillaire- Marcel, C., Dabrio, C.J., Gonzalez Delgado, J.A., Cabero, A.,Bardaji, T., Ghaleb, B., Soler, V., 2010. Sea level changes during the last andpresent interglacial in Sal Island (Cape Verde archipelago). Global and PlanetaryChange 72 (2), 302e317.

Zudimendi, M.A., 2007. Discusión sobre la malacofaunas presentes en sitiosarqueológicos de la patagonia continental argentina. In: Actas VI Jornadas deArqueología e Historia de las regiones Pampeana y Patagonia. Mar del Plata,ISBN: 978-987-544-241-2.

http://www.malacolog.org/http://www.malacolog.org/

Paleoecological significance of Late Quaternary molluscan faunas of the Bahia San Blas area, Argentina1. Introduction1.1. Study area1.2. Geological background1.3. Paleontological background

2. Materials and methods3. Results3.1. Taxonomic and paleoecological composition3.2. The Pleistocene of Bahía San Blas3.3. The Holocene of Bahía San Blas3.4. Modern fauna3.5. Mollusc associations

4. Discussion5. ConclusionsAcknowledgmentsReferences