(Middle Pleistocene): Climatic Implications

Home , Aegopis, Aegopis verticillus, Azeca, Azeca goodalli, Clausilia dubia, Clausilia pumila

Palaeoecography. Pahu'oclimatoh*gy, PalaeoecoloALv, 92 (1992): 15 29 15 Elsevier Science Publishers B.V., Amsterdam

West-European terrestrial molluscs assemblages of isotopic stage 11 (Middle Pleistocene): climatic implications

Denis-Didier Rousseau", Jean-Jacques Puiss~gur b and Frangois L6co11¢ ~'Lamont-Doherty Geological Observato O' qf Columbia University, Palisades, N.Y. 10964, USA bURA CNRS 157, Centre des Sciences de la Terre, 6 Bd Gabriel F-21100 D!/on, France ¢Groupe Seine, Centre de GOomorpholoA,ie du CNRS, rue des Tilleuls. F-14000 Caen, Fram'c (Received May 16, 1991: revised and accepted October 10, 1991)

ABSTRACT

Rousseau, D.-D., Puiss6gur, J.-J. and Lecolle, F., 1992. West-European terrestrial molluscs assemblages of isotopic stage II {Middle Pleistocene): Climatic implications. Palaeogeogr., Palaeoclimatol., Palaeoecol., 92:15 29.

Tufil deposits in the Seine and the Avelasse Valleys have yielded numerous molluscs assemblages belonging to the Lyrodiscus Biome. These malacofaunas, primilarily indicative of forest which developed under a warm climate, have no present-day counterpart. The biostratigraphical study of several localities based on new investigations at Vernon (Seine Valley) and Arrest (Avelasse Valley) and a reexamination of the faunas from St Pierre-les-EIbeuf suggests the allocation of a Holsleinian age. This is supported by U,'Th dates for Vernon and the stratigraphy of the loess sequence of St Pierre-les-Elbeuf. Similar assemblages yielded by tufas of the same age in England and Germany indicate that the Lyrodiscus Biome was widespread. The warm climate recorded by the molluscs of the tufa deposits is in agreement with pollen and marine analyses for the isotopic stage 11 (362 423 kyr B.P.). In this way, the Lyrodiscus Biome appears as an interesting marker for the continental Quaternary in Western Europe. If the occurrence of these particular molluscan assemblages is due to climate, refuges from the declined Tertiary biota, from which i.e R. (Lyrodiscu.s) could have emigrated, also needed to exist.

Introduction MAP (lmbrie et al., 1984). Here we report the results of a malacological investigation made in Among biological remains which occur in conti- terrestrial tufas, from the Seine and the Somme nental deposits, pollen are frequently used to valleys in northern France (Fig. I). A comparison reconstruct paleoenvironments. Numerous studies is made with continental pollen and marine demonstrate that climatic changes occurred at records. roughly the same times in the oceans and on the continents (Peteet et al., 1990; Rossignol-Strick, 1983: Woillard, 1978; Van der Hammen et al., New malaeological records 1972). In other geological contexts, molluscs also Vernon provide good ecological data which complement the botanical data (Kerney, 1963; Lozek, 1964; The Vernon tufa is a complex deposit, located Puiss6gur, 1976). In the Achenheim loess series in the Seine Valley, about 70 km west of Paris (Rousseau and Puiss6gur, 1990a), variations in the (Fig. 1) which shows two different stages of devel- components of the molluscan associations are similar to the isotopic c31sO curve provided by SPEC- opment (L~colle et al., 1990) (Fig. 2): (a) A thick travertine, well indurated in places or showing alternating discontinuous smooth- Correspondence to: D.-D. Rousseau. Lamont-Doherty Geologi- cal Observatory o['Columbia University, Palisades, N.Y. 10964, indurated levels, constitutes the base of the upper USA. part. The travertine is one to several meters thick,

0031-0182:92505.00 i 1992 ElsevierScience Publishers B.V. 16 D.-D. ROUSSEAU

ous one because it corresponds to the colluviation 54 ~'¢' ¢1 '.,q.:.:.-:), 2.:.:.:._3 <_(~;~ of upper part of the tufa and its rubefaction.

• ' .} .Z:'.'. .-. " ~',- • ' . -. . . . - .':':~" .- • According to a geological and geomorphological Ii\iJ' --)'.'.-.'.-.-.. : lckhngham -.-...... - • .i " " " 4 ,...... ¢~ . . . study (L&olle, 1989), this second part corresponds to another time of deposition, clearly distinct from elL_ - -Hitchin '.'.'..u _...~..~.'.'.'.'.~.-.'.'.'.'.'.'.-.'.'.-.v,.. J t ¢. '...... -:--2-~ .~. . . XQ. . ". ". . .'.. " .". ".-q". ] /'....f-'.:--" ~Arrest'.. ,'.-.-.'.-...-.'.-.-.-.. the upper one. / <;.... Osler;u;i,i Determination of the species, present from a ] 1.7~./~...~Vernon .:./.3.../.3.<... previous sampling in the upper non-cemented tufa, / c<'r~.~,:,z--Si.;-"7~~..i-,,. -.-...-..-.. ,..i.-i-~,/~-...i~ 48 ~ ~.... """ "" ""/" s.' .'.'. "."."C:\". -. ".' .'. '.. ".'.'/~ .. -...... : indicates that the assemblages are unique in their l- :: :: composition (Table 1). They do not correspond to St Pierre-l~s-Elbeuf :-"~':'33 7 3":3:--£-'~.3"3":33':'7: any classical association as determined by Puis- I s6gur (1976) for northern France, but seem to be F- ::::::::::::::::::::::::::::::::::::::::::::::: the western equivalent of the eastern European Banatica fauna (Rousseau, 1992). Four taxa are extinct: 421:5:i:!:i:ili:i:i:i:i:i:i:[:i:i:i:i:i:5 I I<;', ':c[.;i:i:i:!t Retinella (Lyrodiscus) skertchlyi -4 0 4 8 12 (Rousseau and Puiss6gur, 1990b), Aegopinella bourdieri (Rousseau and Puiss6gur, 1989), Succinea Fig. 1. Location of the different sites discussed in the text. joinvillensis and Catinella antiqua. Six species no longer live in northern France: Leiostyla anglica, and consists of a so-called slab, rich in molded endemic in the British Islands, Hygromia cinctella plant remains such as roots, branches or leaves. A present in Southern Europe, and Discus ruderatus, two meter or so thick, smooth tufa overlays the Acicula polita, Aegopis verticillus and Ruthenica travertine and is locally indurated. Sediment was filograna from Central Europe (Kerney et al., 1983) taken for malacological investigation from this (Fig. 3). The other species still live in northern smooth unit. All these horizons are light in color. France, and a few aquatic taxa are also present. The morphology and position of the bed-rock are In addition to this apparent heterogeneity of the unknown. assemblage, the occurrence of Retinella (Lyrodis- (b) The lower part is dissociated from the previ- cus) skertchlyi is another peculiarity. This species so IvE NoN_____II Core NE 60~mr..~ 350-400,000 yrs 23.2.

"',~::':':'..'~'~'~:~..,. ----~ , water-sump

0 s~m , ---~-.25 m ..... ,

IM!~FII!~IIII

Fig. 2. Geomorphological and stratigraphical interpretation of the tufaceous formation in Vernon. 1= substratum (chalk); 2= rubefaction; 3 = smooth facies tufa; 4 = travertine; 5= "'sugar-plum'" facies tufa; 6 = colluvium (from L6colle et al., 1990 modified). 3ERRESFR[AL MOLLUSC ASSEMBLAGESOF ISOTOPIC STAGE 11 (MIDDLE PLEISTOCENE) I7

TABLE I

Vernon, first malacological investigations. List of different species recognized in the samples and individuals counted.

Species \ Levels 1 2 3 4 5 / Ecol. Groups

Acanthinula aculeata 23 31 6 4 4 Acicula polita 3 1 Azeca goodalli 2 15 2 3 3 Aegopinella nitidula 47 90 12 33 35 Aegopinella pura 38 96 15 15 18 Aegopinella bourdieri 1 R. (Lyrodiscus) skertchlyi 1 23 4 18 30 Helicodonta obvoluta 22 5 3 7 5 Clausilia bidentata 20 8 1 1 13 Cochlodina laminata 7 6 3 3 Perforatella incarnata 8 3 10 8 Orcula doliolum 25 2 4 45 Aegopis verticillus 1 1 Ena montana 3 2 Ruthenica filograna 19 36 Discus ruderatus 6

Discus rotundatus 53 95 24 70 1 Acicula dupuyi 11 Cepaea sp. 35 50 18 15 50 Bradybaena fruticum 4 15 6 4 7 Hygromia cinctella 12 Pomatias elegans 45 60 18 Laciniaria biplicata 2 4 1 10 30 Vitrea crystallina 67 130 20 Arianta arbustorum 12 4 5 6

Macrogastra ventricosa 9 1 1 1

Cecilioides acicula 4

Vallonia costata 1 2 29

Trichia hispida 6 43 6 4O 70 Helicigona lapicida 2 4 4 1 2 Euconulus fulvus 1 2 Puncture pygmaeum 2 Vitrina pellucida 6 6 1 4 7 Oxychilus alliarius 21 Clausilia parvula 7 5 4 Vitrea contracta 23 49 8 20 3 Cochlicopa lubrica 31 7 14 7

Limax sp. 10 16 4 2 25 7'

Carychium tridentatum 2 20 2 3 Succinea joinvillensis 13 4 3 5 Succinea oblonga 1 Catinella antiqua 1 1

Columella edentula 1 Leiostyla anglica 3 Succinea putris 10 Zonitoides nitidus

Belgrandia sp. 1 2 Galba truncatula 7 10 Pisidium sp. 1 18 D.-D. ROUSSEAU

-- C b

, I f Fig. 3. Some of the allochthonous species, according to their present distribution, occurring in tufa assemblages, a. Hygromia cinctella: b. Ruthenica.filograna; c. Aegopis verticillus: d. Laminfera pauli; e. Acicula polita; f. Leiostyla anglica. The scale represents I mm. has related endemic species in the Canary archipel- from these pulverent deposits (Fig. 2 and 5). Above ago (Kerney, 1976; Rousseau and Puiss6gur, the travertine, 9 samples were taken corresponding 1990b). to different recognized horizons according to color The assemblages show a high dominance of and induration of the sediment. Two additional forest species (Fig. 4a, b). This implies a forest samples were taken to control the base of the core environment that developed under a climate with and correlated on the basis of lithology, with the warmer and drier summers than today in the same first two samples of the main core. area. The occurrence of fossil leaves and seeds, Three kinds of deposits, from bottom to top including Ficus, which today has a more southern (Fig. 5), overlay the travertine: natural distribution, confirms the climatic inter- --a relatively non-cemented tufa, with weakly pretation. indurated levels of various colors (-3.6 to -2 m), A new investigation provides more detailed data --deposits with a loamy facies which seem to

(a) (b)

I , l L I i l , I , I I , I -- I , I , I ind. i ~ l , i , i a i , i , [ ~ i , i , l , i sp. s f t I[:'-:W/////,,~I .8 1 I I I:':.F////Y~ 128 4 I i IR/////////2~tl ~ ~ ~ I ....I I I.'.::U/////~liiiiiiiiiiiiiiiijiiiiiiii~ ~ , 3 I I V////N l~i::] 180 I I l:i::~//////~ l~ii~'~'~i~lu~o f t t:H 8 7 9 I I I V/////,'~ l:~i:~ii!!!!i!iiitmml3 5 1 I ...... I ...... , , t 'I 0 20 40 60 80 100 0 20 40 60 80 100

Fig. 4. Vernon. First malacological investigations. Variation of the percentage in (a) individuals (ind.) and (b) species (~sp.) within each ecological group, according to Puiss~gur (1976). Signification of the groups: 1- forest, 2= open forest, 3 = damp forest, 4= steppe, 5 = open ground, 7= mesophilous taxa, 7"= slugs, 8= hygrophilous taxa, 9= paludal, 10= fresh water. 1ERRES1 RD\L MOLLUS(" ASSt MBLAC, ES OF ISOTOPIC SI AG[ II {NIlDDL[ PLklSI (l(ENE) 19

,.-,i

~D 'o,~m Ta section description 0

09 .,,.~

Vegetable soil

110 9 ufo mixedwith oiL ...... tions :::::::::::::::::::::::::::{i}i{ii{ilgii{iii{iii 8 130 Yellow tufa with some vegetable soil [:::ii::{!::!ii::i:i:: iili i:: ] 145 :::::::::::::::::::::

arty vegetable soil :::::::::::::::::::::::::::

6 18o Yellow tufa without concretions t 1 2o0 :::::: ::: ::.:.:::<:::::::: Pulverulent tufa • 5 '.... ,.. .+: 220 " )i~i~i~i~ili!i~i!i:iiiiiii!~i)iii!iii!i!i!)iii~i~i~i;~ili~i~i~ii~;i- 4 !iii!iiiiiiiiiiiiiiiiiiii...... Yellowish tufa i ...... :.: 255

...... i.i Pulverulent tufa 1 . . ...

...... :i i~~~'~'~'~~~~ 295

More white tufa, mere compact

...... "," 340 ...... Pink tufa. less indurated , loamy-sandy ...... 360 Level with lot of travertine debris de 366 travertin and flint gravels

;,;,;...... More compact tufa 1 ...... 340 7.-.-.-.-.-.-.-.'.'.'.'.'."&'.'.'_'_'.'.-.'.-.-.-.-.-: ], ...... Pulverulent tufa with indurated levels

...... 370 380

Fig. 5. Vernon. New malacological investigations. Location of the different malacologicat samples and schematic lithological description of the levels. I 3 correspond to the different groups recognized.

correspond to a degradation of the tufa (-2 to diversity and abundance (Table 2). Moreover, the - 1.3 m) variations in the total number of individuals occur- --a composite of tufa and soil under the modern ring in each ecological group, sensu Puiss~gur soil. (1976), is in agreement with the three previously The list of the recognized species shows high defined units based on lithology (Fig. 61. 20 D.-D. ROUSSEAU

TABLE 2

Vernon, new malacological investigations. List of different species recognized in the samples and individuals counted.

Species \ Levels 9 8 7 6 5 4 3 2 1 2' 1' / Ecol. Groups

Aegopinella nitidula 4 4 34 25 35 12 20 18 6 Aegopinella pura 1 1 14 21 12 3 2 6 3 Helicodonta obvoluta 1 3 2 31 10 8 6 6 8 8 Ena obscura 1 Azeka goodalli 1 2 2 2 5 1 3 Aegopinella bourdieri 5 4 Cochlodina laminata 2 3 6 2 1 1 Perforatella incarnata 3 1 1 1 Acanthinula aculeata 3 1 4 4 4 5 1 Aegopis verticillus 3 5 1 2 1 Clausilia bidentata 4 5 3 2 4 2

Pomatias elegans 20 4 3 9 30 17 18 9 5 4 Discus rotundatus 7 1 3 5 17 22 8 31 12 8 1 Cepaea sp. 7 3 2 5 35 35 30 28 27 10 16 Hygromia cinctella 1 2 6 2 1 2 1 1 2 Laciniaria biplicata 1 2 2 Arianta-Bradybaena 1 1 2 1 1 Acicula dupuyi 3 1 15 Vitrea crystallina 1 7 1 2 Acicula polita 1

Macrogastra ventricosa 1 2 2 1 1 1

Cecilioides acicula 37 6 2 3 Helicella sp. 12 7 3 1

Vallonia costata 200 16 15 2 Vallonia pulchella 50 3 Pupilla muscorum 3 1 2 1

Helix aspersa 1 1 1

Trichia hispida 213 16 17 1 3 3 5 1 Cochlicopa lubrica 43 1 1 Oxychilus sp. 5 1 3 1 3 Nesovitrea hammonis 5 Vitrea contracta 1 1 1 2 7 3 1 1 1 1 Clausilia parvula 3 1 Helicigona lapicida 4 4 2 1 1 1 1 Vitrina pellucida 1 13 3 3 2 2 2 Punctum pygmaeum 1

Limax sp. I3 1 1 2 2 1 1 3 7 t

Succinea oblonga 71 3 1 1 Carychium tridentatum 8

Succinea putris 12 2 Zonitoides nitidus I0 6 3 3 4 4 5 9 Carychium minimum 3

Planorbis planorbis 5 Galba truncatula 4 Belgrandia sp. 10 Ancylus fluviatilis IERRFSI RIAL MOLl [SC ASSEMBLAGES OF ISOTOPIC STAGE II {MII)I)LE PLEISIOCENE~ 21

0 1 O0 200 300 400 500 600 700 800 I I I I I I I

[

I I I I I I

0 100 200 300 400 500 600 700 800 Fig. 6. Vernon. New malacological investigations. Variation of individual numbers in each ecological group (see legends in Fig. 4).

An increasing number of individuals from bot- ventricosa (Table 2). The lack of aquatic species tom to top and a high percentage of forest taxa agrees with the occurrence of a non-permanent characterize the malacofauna of the first unit. The spring, an interpretation previously suggested by second unit shows a generally decreasing number Puissegur (Puiss6gur in Lacolle, 1989). At the top of individuals, a decrease in forest species, and the of this unit (sample 5; Table 2), the proportion of occurrence of steppe and open ground taxa. Finally mesophilous species increases. The species Helici- the number of individuals increases sharply again gona lapicida, which has a preference for a slight in the top sample. This increase does not corre- forest covering, does not occur above sample 5. spond to a bias in the sampling as this is a 20 cm This development agrees with the general evolution sample taken under conditions roughly similar to of the malacofaunas. the others. Variations in group 7 permit the definition of the This tripartition occurs when the different second unit (Fig. 7), which represents a more open assemblages are compared, using species and environment. In this unit the progressive decrease individuals spectra of the following ecological of the forest taxa occurs from bottom to top (fig. 7), groups: (1) forest, (2) semi-forest, (3) moist forest, corresponding to increasing steppe and open (4) steppe, (5) open ground, (7) mesophilous, (7)' ground species. The forest component gradually slugs, (8) hygrophilous, (9) paludal and (10) decreases after sample 5 and is replaced by a grass- aquatic species (Fig. 7a, b). These ecological groups land in which still occur some trees or bushes. are defined according to the ecology of each mol- The last sample, corresponding to the third unit. lusc species (Lozek, 1964; Puiss~gur, 1976). shows a completely open environment in which The first unit reflects the high dominance of few bushes remain. forest taxa, especially in the number of individuals, Characteristic taxa, ttygromia cinctella, A. hour- and has a small aquatic component (three individ- dieri, A. verticillus and A. polita (Fig. 3), occur uals in samples 3 and 4 (fig. 7). However, moisture only in the first unit (Table 2) confirming its is indicated by the occurrence of Macrogastra interglacial allocation, followed by unit two repre- 22 D.-D. ROUSSEAU

(b) {a) ind. i , I , i , i , i , i , I i I , i i I i I sp- , , l ~ ' . '.~j~' 727 [] ~','-'},':::" 66 ~:4:" 16 ~iil 68 ~ii~i 21 ] ~~i 39 ] ~/////A:i!iiiil] 19 9 ] IV,,~+iiiil 195 P 1 .. I ll/~l+++m ,+++ I I lF41+++++++I1,9 I I I U////,~,,A!ii~l,7 I VA[++++++++I,07 --1 U/////A H~0

2' l I ~"~!!i!}!!!!!!!l 9+ I t K//////,~ii+iiii~+i::l 21 ! ...... I ...... ! !,o i i ' i i i i i ' i • i , , 0 20 40 60 80 ,00 0 20 40 60 80 100 Fig. 7. Vernon. New malacological investigations. Variation of the percentage in (a) individuals (ind.) and (b) species (sp.) within each ecological group, according to Puiss6gur (1976) (see legends in Fig. 4). senting the degradation phase. Under these conditions. According to Clement's (1949) definition of tions the correlation with the previous samples a biome, which evokes that animal populations (Table 1), a few meters away, is proposed as are associated with formations of wide vegetal follows. complexes, a biome being thus a community of plants and animals usually of the rank of a forma- 1972 new study tion which in other words represents a climatic vegetal and animal community, we can determine Sample 5 sample 6 the Lyrodiscus Biome for this particular Pleistocene Sample 4 sample 5 community (Rousseau, 1992). Its malacological sample 4 and botanical composition (occurrence of the fig Sample 3 sample 3 tree, the laurel of the Canary islands, Buxus, Celtis) is clearly heterogenous compared to the present Sample 2 sample 2 time. Sample 1 sample 1

The travertine samples were dated using the 23°Th/ St Pierre-I&-Elbeuf 234U method. The measurements indicate a radio- active equilibrium implying an age equal to or In the Seine Valley, 42km west of Vernon older than 350,000-400,000 yr B.P. (L6colle et al., (Fig. 1), the St Pierre-16s-Elbeuf deposits yield an 1990). We suggest a correlation with isotopic stage important continental record of the Middle and l l, in agreement with the geomorphological and Upper Pleistocene (Lautridou et al., 1974). This stratigraphical context of this area (L~colle, 1989). locality is a key loess section for Western Europe The composition of the malacofaunas, provided (Lautridou, 1985). Five non-calcareous loess units by the two series of samples in Vernon, confirms were recognized, separated by four interglacial Bt the biostratigraphic correlation proposed between soils: Elbeuf I= Eemian, Elbeuf II, III= intra- Vernon and La Celle-sous-Moret (Bourdier et al., Saalian, and Elbeuf IV (more weathered than the 1969). In these two sites, the tufaceous sedimenta- others) of Holsteinian age (Lautridou et al., 1974). tion is connected with a biological association A calcareous tufa, which yielded a rich malaco- which gathers both plant and molluscs associa- fauna, overlays this soil (Fig. 8). I t RRISIRIAL MOI_i t 5;( ,\SSt MFH.AGI S Ok ISOIOPIC SIAGL 11 (MIDD[ [ PLILISI()('I-NI ) 23

E W ~ nolocene Weichselian " " " Eemian=Pl ~ "~ ...... ~ P2 ~ q ~P3 F~ i ~- = 13 ~

tufa .- :T~rttn~,tt.,,m~ n,...... ~_- _ ...... e

[], ::-. ..'-~ flood plain b_ m _ _x],,,:., Ii

~EI~~]~~ 2~ 3~ 4~5 ~2~6 ~-~ 7~ 8

Fig. 8. St. Pierre-les-Elbeuf. Main outcrop showing the stratigraphic sequence. 1- loess. 2- paleosol. 3 humifcrous soils, 4- lluviatile sands, 5 :- fluviatilc gravels, 6 - stone line, 7= "'liser+ chocolal", ,Y- base of the quarry. The "liscrc chocolat'" corresponds to a flfin brown layer of argilans (paleosol III) fixed upon the calcareous ttlfa (BI) (from gautridou et al.. 1983. modified).

The malacofauna is typically interglacial for the Vernon upper tufa, in agreement with thc (Table 3). Thirteen forest species correspond to radiometric age reported by Lacolle et al., 199(t. 33.8% and 9 semi-lk)rest species to 32.3% of the total amount. The occurrence of species represen- tative of steppe, open ground, xerophilous ecoh)gi- A rl'cS[ cal groups seems to be accidental. Aquatic species are well represented, but the St Pierre malacofauna The Arrest site is located in a small valley of cannot be an aquatic dominant fauna since it the Avalasse river, 8 km south of the Somme typically characterizes a moist forest where estuary (Fig. I). Tulas occur 22 m above the intermittent streams supply semi-permanent pools present-day river level (Fig. 10). These tufas (Fig. 9a: A. B). impregnated the underlaying chalk which is consol- Fossil species. Retinella ( Lyrodiscus) skertcldyi. idated. The following succession was observed Ae~opim'lla hourdieri, as well as Laminf/kru pauli from the base to the top (Bourdier, pets. comm.): (endemic in the Bayonne neighborhood) and a silty tufa with white concretions providing mala- Hvgromia cim'te/la (Fig. 3). a mediterranean taxon cofaunas, a non-cemented level, an indurated level ('Fable 3) occur as well. in which one meter thick pedological pockets are The proximity of both Vernon and St Pierre- present, and finally a colluvium layer. A lcvel of Ids-Elbeuf permits a correlation to be made based rounded flint gravel occurs between the indurated on geomorphological (Ldcolle, 1989) and biostrati- chalk and the tufas. graphical evidence. Holsteinian age is suggested As determined in the previous sites, the malaco-

(a) (b) I,l,lll~lhl .U===q , ,,, Ii:: {i::ii iit i 325,i,,d. ',',',',]'t#)//7,)/k'lI 36

F ' i i i i , i ' I ' i ' i ' i ' i ,,I i i i t ' i '

0 2 0 4 0 6 0 8 0 1 0 0 0 2 0 4 0 6 0 {'; 0 I 0 0

Fig. % Variation of the perccmage m (a) individuals (imt.) and (b) specie.,, (Vx) within each ecological group, according to Puissdgur (1976). ,.I = St Pierre-les-Elbeuf. B= Arrest (see legends in Fig. 4). 24 D.-D. ROUSSEAU

TABLE 3 TABLE 4

St. Pierre-16s-Elbeuf. List of different species recognized in the Arrest. List of different species recognized in the samples and samples and individuals counted. individuals counted.

Species [ Ecol. Groups Species / Ecol. Groups

Ena montana 25 Acanthinula aculeata 70 Acicula polita 5 Aegopinella nitidula 176 Acanthinula aculeata 57 Aegopinella pura 149 Helicodonta obvoluta 60 Azeca goodalli 50 Aegopinella pura 212 Clausilia bidentata 12 Aegopinella nitidula 192 Cochlodina orthostoma 2 Cochlodina laminata 35 Clausilia sp. 58 Macrogastra rolphii 2 Discus ruderatus 57 Clausilia bidentata 100 Ena montana 9 Macrogastra plicatula 4 Helicodonta obvoluta 4 Perforatella incarnata 2 R. (Lyrodiscus) skertchlyi 11 Aegopinella bourdieri 52 Vertigo pusilla 1 Aegopis acieformis 16 Vitrea subrimata 7 R. (Lyrodiscus) skertchlyi 1 Arianta + Bradybaena 7 Discus rotundatus 345 Cepaea sp. 30 Acicula dupuyi 17 Discus rotundatus 224 ~2 Vitrea crystallina 63 Vitrea crystallina 284 Laciniaria biplicata 25 Laminifera pauli 11 Perforatella bidentata 15 Cepaea hortensis 200 Macrogastra ventricosa 2 Arianta arbustorum 20 Bradybaena chouquetiana 1 Vallonia costata 8 Bradybaena fruticum 19 Hygromia cinctella 16 Clausilia dubia 15 Cochlicopa lubrica 14 Macrogastra ventricosa 12 Euconulus fulvus 5 Helicigona lapicida 1 Cecilioides acicula 1 Nesovitrea hammonis 3 Trichia hispida 80 Vallonia costata 3 Vitrea contracta 36

Monacha cartusiana 2 Limax sp. 1 7'

Puncture pygmaeum 25 Carychium tridentatum 1399 8 Trichia hispida 28 Vitrina pellucida 5 Carychium minimum 466 Helicigona lapicida 10 Succinea putris 4 Vitrea contracta 35 Vertigo antivertigo 2 Euconulus fulvus 1 Clausilia parvula 93 Anisus leucostomus 24 Oxychilus sp. 16 Galba palustris 4 Galba truncatula 5 10 Limax sp. 121 7' Pisidium sp. 22

Carychium tridentatum 2 8

Vertigo antivertigo 10 Succinea putris 27 Zonitoides nitidus 17 fauna is typically interglacial (Table 4). Forest and Pisidium sp. 22 Valvata piscinalis 172 semi-forest species represent 52.78% of the total Ancylus fluviatilis 15 number of species and 35.86% of the total number Bathyomphalus contortus 2 Galba truncatula 5 of individuals (Fig. 9b: A, B). The environment is Galba palustric 33 the same as that of St Pierre-l~s-Elbeuf. A moister Bulimus sp. 2 10 forest accompanied the occurrence of Perforatella Radix ovata 9 Limnaea stagnalis 6 bidentata, Macrogastra ventricosa and a high Gyraulus albus 60 number of Carychium tridentatum (Table 4). Con- Planorbis pl. -carinatus 18 Physa fontinalis 1 trary to the two previous sites, few allochtonous Belgrandia sp. 8 species occur. Only the fossil Retinella (Lyrodis- FERRES rRI,~L MOLLt!SC ASSEMBLAGES OF ISOTOPIC STAGE II (MIDDLE PLEISTO('ENE) 25

".i~ -,, ARREST

40 m - molluscs

~}i~.!:!:!:!:i:i:?i:?:?:;:?;i:i:i:i:i~ ...... ~, ~,ro~,.

...... , ',,'.. '. q. ',,',, ',. ', .'..~ ,'.. '., '., '., ',. '., '.. ', ,', , , , , ,,%t,, L,, ,',',','.!.!,!.i.1.1,',i,1.','.!.'.%1 ',',',',',',','/,',

~)- 2 3 4 5 6 7

Fig. 10. Arrest. Schematic distribution of the stratigraphy. 1 = substratum (chalk): 2 = rounded flint gravels; 3= white silty tufa with some concretions: 4 = non-cemented tufa: 5 = indurated tufa; 6= colluvium; 7= pedological pocket (from Bourdier, pets. comm., moditicd) cus) skertchlyi and the central European D&cus of species which have no relatives today in the ruderatus were recognized. British Isles (Table 5), The assemblages contain The occurrence of these deposits in the Somme the fossil Acicula diluviana and Retinella ( L)'rodis- Valley implies that this particular assemblage is cus) skertchl)'i, the central European Semilimax not a response to the microclimate of the Seine semilimax, Clausilia parvula and Acicula polita, the Valley. At least four localities, in an area of about East European Ruthenica./ilograna and the West 210 km long, recorded this ecological event. Sim- European Laminff'era pauli (Fig. 3). The age allo- ilar assemblages in the surrounding countries of cated to these tufas is Hoxnian, the British equiva- this area, already published, are examined to deter- lent of the Holsteinian (Kerney, 1977). mine whether further evidence of this occurrence exist. Germany Other West-European malacological records M iinzig (1974) described the malacofaunas from England a carbonaceous silty level in the Swabian Jura, at H6rlis, southwestern Germany (Table 6). Once Kerney described a particular malacofauna from more the composition is heterogeneous and seems tufas in Icklingham (1976) and Hitchin (Kerney, to be similar to those already found in France and 1959: Holyoak et al., 1983). These two assem- England (Fig. l lb: A, B). Apart from the extinct blages, typifying an interglacial forest environment R. (Lyrodiscus) skertchlyi, the Atlantic species (fig. l la: a, b), are characterized by the occurrence Clausilia bidentata, and Azeca goodalli occur

(a) (b)

A 13 0 4 I i 4 7

o 20 40 60 80 10o 0 20 40 60 so lo0

Fig. I 1. Variation of the percentage in (a) individuals (ind.) and (b) species (sp.) within each ecological group, according to Puissggur (1976). A = Icklingham (England). B= H6rlis (Germany) (see legends in Fig. 4). 26 D.-D. ROUSSEAU

TABLE 5 TABLE 6

Icklingham. List of different species recognized in the samples H6rlis. List of different species recognized in the samples and and individuals counted (from Kerney, 1976). individuals counted (from Mfinzing, 1974).

Species / Ecol. Groups Species / Ecol. Groups

Acanthinula aculeata 50 Acanthinula aculeata 1 Acicula diluviana 5 Aegopinella sp. 9 Acicula polita 64 Azeca goodalli 82 Aegopinella nitidula 78 Clausilia bidentata 7 Aegopinella pura 98 Discus perspectivus 11 Azeca goodalli 92 Ena montana 1 Clausilia bidentata 2 Isognomostoma isognomostoma 6 Cochlodina laminata 1 Orcula sp. 8 Cochlodina sp. 5 R. (Lyrodiscus) skertehlyi 5 Trichia edentula 1 Clausilia sp. 28 Vitrea subrimata 2 Ena montana 2 Vitrea sp. 1 Helicodonta obvoluta 4 R. (Lyrodiscus) skertchlyi 37 Arianta arbustorum l Ruthenica filograna 1 Eucobresia diaphana 13 Vertigo pusilla 6 Vitrea subrimata 7 Clausilia dubia 1 Zenobiella subrufescens 1 Zonitoides excavatus 20 Lymnea sp. 1 Physa fontinalis 1 10 Arianta arbustorum 3 Cepaea nemoralis 3 Discus rotundatus 289 Pomatias elegans 25 Vitrea crystallina 101 a silty level between two Alpine tills (Miinzing and Aktas, 1987). The fauna is quite similar to the Clausilia pumila 1 3 H6rlis assemblage showing that the distribution of Vallonia costata 4 5 the Lyrodiscus Biome reached as far as 11°E.

Balea perversa 1 Clausilia parvula 1 Discussion and conclusion Cochlicopa sp. 2 Euconulus fulvus 10 Helicigona lapicida 2 As determined from the multidisciplinary inves- Nesovitrea hammonis 3 tigation of the Biache St Vaast site, a well-defined Oxychilus cellarius 3 Oxychilus sp. 2 hierarchy seems to exist between pollen and mol- Punctum pygmaeum 30 lusc records (Somm6 et al., 1989). When both Vitrea contracta 17 remains are in complete agreement, the event can Deroceras/Limax 12 be characterized generally as an interglacial phase. Milax sp. 7 7' On the contrary, if disagreements occur, mainly in Carychium tridentatum 78 8 the amplitude of the implied climatic variations, an interstadial episode is implied. Carychium minimum 7 Leiostyla anglica 3 Is this warmest stage, recorded by molluscs, also recognized in the pollen assemblages? First, some Bathyomphalus contortus 1 Bythinia sp. 1 fossil leaves and seeds indicate the occurrence of Hippeutis complanatus 2 a interglacial warm forest in Vernon and La Celle- Pisidium obtusale 7 l0 Planorbis planorbis 2 sous-Moret (Bourdier et al., 1969). Secondly, based Sphaerium corneum 1 on the continental equivalent of isotopic stage 11, Valvata cristata 175 several pollen analyses indicated that the related stratigraphical levels indicate a warm climate. Alpine Isognostoma isognostoma, Eucobresia dia- In Great Britain, Hoxnian substages III and IV phana, Trichia edentula. At Osterbuch, southern indicate an oceanic climate with forests of mainly Germany, the same association is described from evergreen composition. Besides the sparse mixed- 1 ERRESI RIAL MOLIL S,(" ASSEMBLAGES OF ISOTOPIC STAGE I I (MIDDLE PLEISIO(ENE) 27 oak forest elements, Lusitanian components highest carbonate percentages for the last four (present-day components of the west Irish flora: climatic cycles during stage I1 (Ruddiman et al., Daboecia cantabrica, Erica mackiana and E. 1989). Core V30-97 (41 10'N, 32'~56'W) indicates ciliaris), Hiberno-American species (Eriocaulon that the largest differences between current and septangulare) or plants which no longer grow estimated paleo-sea surface temperature for sum- there (Brasenia eJpurpurea, Lysimachis punctata. mer and winter (SSTs and SSTw; +5.1 C) also NymphoMes cordata and Erica scoparia) occur occurred during stage I 1 (Ruddiman et al., 1989). (Godwin, 1977). The climatic signal provided by molluscs during In southwest France, Texier et al. (1983) drew stage 11 is in agreement with the results of various attention to high temperature conditions during pollen analyses which confirm the interglacial char- the "Mindel Riss" stage. The flora contains acteristics of the Lyrodiscus Biome. Moreover, as numerous thermophilous taxa (mixed-oak), hygro- marine records also indicate warm climatic condi- philous herbs but also Mediterranean species (Rho- tions during this time span, a global warming, in dodendron ponticum, Erica mediterranea) and taxa order to microclimatic conditions over Western with Lusitanian affinities (Dabaoecia cantahrica). Europe, can be involved in permitting the develop- The Tenagghi Philippon sequence (41 10'N, ment of this particular assemblage. However, this 24~20'E), in Greece, indicates a long and warm biological association corresponding to isotopic episode at the base of the Lekanis complex during stage 11 never occurred in the following intergla- which herbs completely disappear (Van der Ham- cials (i.e. isotope stages 9, 7 and 5). According to men et al., 1972). the astronomical theory of climate, climatic varia- All these continental records imply a warmer tions, as a function of insolation, can be explained climate, deduced from the malacofaunas of the in terms of changes in the configuration of the Lvrodiscus Biome, which occurred in Europe dur- three orbital parameters: (1) the longitude of the ing the isotopic stage 11. However, other data perihelion, which determines in which season from both continental and marine records also the insolation is maximum, (2) obliquity, which show evidence of a warmer climate during isotopic determines where more insolation is directed in stage 11. summer, and (3) eccentricity, which is a measure In the Hula Basin, in Northern Israel, a long of how elliptical the Earth's orbit about the sun pollen sequence shows a well developed episode, is (Berger, 1978, 1982). part of the QVI zone, correlated with stage 11. K ukla et al. (1981) studied the orbital configura- During this stage, steppe elements are highly domi- tion of each interglacial. They conclude that inter- nant, corresponding to the interglacial extension glacials have a specific orbital configuration, high (Fuji and Horowitz, 1989). obliquity and an autumn perihelion but can presenl In the Colombian Bogota-Funza cores (4N, difference in the eccentricity. Stage 1 I, for example, 74"W), changes of the vegetation are recorded over shows high obliquity, autumn perihelion but low the last 3.5 myr B.P. (Hooghiemstra, 1989). During eccentricity. It shares the same characteristics with stage I1, the altitudinal position of the forest line the Holocene, however. Although stage 11 shows was higher than 3300 m, quite similar to the differences with the other interglacials which could current position. The prevailing average temper- involve particular climatic conditions, this does ature of the high plain of Bogota was estimated not explain why such a particular assemblage to be greater than 14.8'C, associated with a low occurred in Western Europe. The variation in the lake level (Hooghiemstra, 1989). composition of a biome reflects regional ecological Ruddiman and McIntyre (1976) showed that impact on the fauna (Rousseau et al., 1990). This Atlantic Ocean cores recorded a well-developed explains the differences observed in the malacofau- interglacial stage l l, with high carbonate content nas of the L3,rodiscus Biome between England and and high 180/160 values associated with a high Germany, but does not explain, however, where it sea level. More recently, DSDP 609 core (49°53'N, originated. Because no similar associations were 24 14'W) in the Northern Atlantic, indicates the recorded prior to this stage, in France and Eng- 28 D.-D. ROUSSEAU recorded prior to this stage, in France and Eng- Records of Climate. Palaeogeogr., Palaeoclimatol., Palaeo- land, southern European refuge zones of the ecol., 72: 79-88. Godwin, H., 1977. Quaternary history of the British flora. In: declined Tertiary biota can eventually be involved, F.W. Shotton (Editor), British Quaternary Studies. Recent but need to be investigated. This proposal is mainly Advances. Clarendon, Oxford, pp. 105-118. based on R.(Lyrodiscus), the history of which Holyoak, D.T., Ivanovich, M. and Preece, R.C., 1983. Addi- seems to be closely connected to that one of the tional fossil and isotopic evidence for the age of the interglacial tufas at Hitchin and Icklingham. J. Conchol., 31: Tertiary forest (Rousseau and Puiss6gur, 1990b), 260 261. which occurred in Europe and Africa, and declined Hooghiemstra, H., 1989. Quaternary and upper-Pliocene glaci- to be restricted, for one part, to the Canary ations and forest development in the tropical Andes: evidence archipelago (Raven and Axelrod, 1974). A precise from a long high-resolution pollen record from the sedi- mentary basin of Bogot~i, Colombia. In: G. Kukla (Editor), location of these refuge zones is, today, difficult Long Continental Records of Climate. Palaeogeogr., Palaeo- to draw, but the Spanish Atlantic coast or North- climatol., Palaeoecol., 72: 11-26. western Africa can be proposed. In this way, a Imbrie, J., Hays, J.D., Martinson, D.G., Mclntyre, A., Mix, limitation, climatic or other, in the opportunities A.C., Morley, J.J., Pisias, N.G., Prell, W.L. and Shackleton N.J., 1984. The orbital theory of Pleistocene climate: support to extend their distribution, can explain the lack from a revised chronology of the Marine 6180 record. In: of the Lyrodiscus Biome during the previous stages. A. Berger, J. lmbrie, J. Hays, G. Kukla and B. Saltzman On the contrary, the warmer climatic conditions (Editors), Milankovitch and Climate. Reidel, Dordrecht, 1, during stage 11 somehow permitted the molluscs pp. 269 305. and the plants to occur northward of their Kerney, M.P., 1959. An interglacial tufa near Hitchin, Hertf- ordshire. Proc. Geol. Assoc., 70: 322-337. restrictive zone. Because such conditions never Kerney, M.P., 1963. Late-glacial deposits on the Chalk of occurred afterwards and because such assemblages south-east England. Philos. Trans. R. Soc. 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