Upper Eocene - Lowermost Miocene charophyte succession in the Ebro Basin (Spain). Contribution to the charophyte biozonation in Western Europe

Abstraet. A charophyte succession has been established in nineteen sections and eight isolated outcrops from the Ebro Basin, ranging from the Priabonian ro the Aquitanian. Most assemblages were recovered fmm continuous sections and their abundance and diversity allow to define a new zonal scheme for the Upper Eocene-Lower Miocene of Europe. The new zonation includes nine subdivisions, based on the distribution of thirty-two species and directly correlated with the mammal standard levels. Changes in diversity, occurring mainly in the Middle and Upper Oligocene, have been related to climatíc variations. A new species, Chara sp. A. is also described and figured.


I. Introduction
During the Paleogene, predominantly nonmarine sediments accumulated in the eastern part of the Ebro Basin.The carbonate freshwater and brackish deposits have yielded abundant charophytes and the assemblages found in conrinuous sections show a f1orizonal succession from the Paleocene ro rhe Lower Miocene.As a result of the srratigraphic studies carried out in the Paleogene sequences of rhe Ebro Basin (ANADÓN 1978;COLOMBO 1980COLOMBO , 1986;;ANADÓN & FEIST 1981;CABRERA 1983;SAEZ, 1987), it has be en established that most of the srudied charophyte assemblages are distributed through a number of continuous and correlable stratigraphic sequences (ANADÓN et al. 1989).This stratigraphic continuity and the quite large number of samples have enabled us ro make a local charophyte biozonation.Moreover, this is one of the uncommon cases in which a charophyte biozonation established on a continuous nonmarine Upper Eocene Lower Miocene stratigraphic sequence can also be referred ro a local mammal biozonation based on more than thirty rodent assemblages (AGusTÍ er al. 1987(AGusTÍ er al. , 1988;;ANADÓN et al. 1987).Our srudy focusses on rhe charophyte assemblages found in rhe sections spanning the Upper Eocene-Lower Miocene interval from the Eastern Ebro Basin, berween rhe Llobregat Valley, ro the Easr, and the Cinca and Ebro valleys, ro rhe West (Fig. 1).These sequen ces are included between the top of rhe marine succession attributed to rhe Priabonian (FERRER 1971) and the botrom of the non-marine Neogene.
Charophyres from rhe Ebro Basin were firsr mentioned by DALLONI (1930) from rhe Sierra de Monrclar and in rhe Santa Coloma de Quera]t succession.Later, ROSELL et al. (1966) based rhe attribution of rhe nonmarine sequences at 19ualada ro the Upper Luretian on a charophyte assemblage identified by L. GRAMBAST which also recognized Harrisichara lineata in rhe locality of El Pares (COLOM et al. 1970) which we will discuss below.Among these first record s, rhe species quoted in rhe explanatíon of the geological maps of Calaf and Cardona (RAMÍREZ DEL POZO et al. 1975a & b) should be mentioned, alrhough sorne of them they have not been rediscovered sínce.The first comprehensive study was by ANADÓN & FEIST (1981) who dated and subdivided rhe succeeding charophyte-bearing sequences of the central part of the Eastern Ebro Basin margin from Thanetian to Bartonian.Larer, ANADÓN et al. (1983) demonstrated the correlation of the uppermost beds of the Pontils Group at the type section, containing Raskyella vadaszi, with rhe standard Mammallevel of La Liviniere and the NP17 N annoplancton zone.These data have been raken into consideration in rhe Paleo gene charophyte biozonation defined by RIVELINE (1986).The charophyte assemblages from the eastern part of rhe srudied area have be en partially analyzed by CHOI (1989).

II. Geological setting
The Tertiary Ebro Basin is the southern foreland basin of the Pyrenees.Thís basín ís also bounded by the Catalan Coastal Ranges to rhe SE and the Iberian Chain ro the SW.In the Eastern Ebro Basin (Fig. 1) rhe sedimentar y evolurion has been mainly influenced by rwo margins: rhe Pyrenees (a thrust sheet belt, PUIGDEFABREGAS et al. 1986) and the Catalan Coastal Range which is mainly relared to a Paleogene strike-slip faulr system (ANADÓN et al. 1985).The Paleo gene succession in the Eastern Ebro Basin, up ro 2500 m thick, comprises two ~~"".
Rh. lraflSiens The Upper Eocene -Oligocene basÍn fill Ín the Eastern Ebro BasÍn consists of thick sequences formed Ín different Iacustrine systems which developed in the inner basin zones.These Iacustrine systems were fed by marginal alluvial systems.The deposits of rhe lacustrine systems comprise carbonates, mudstones, sandstones, evaporites and minor, coals.The allu vial deposita consist of proximal conglomera tes that pass late rally , basinwards, into sandstone and mudstone dominated sequences.AKADÓN et al. (1989) have distinguÍshed five lacuarrÍne systems for the Upper Eocene to Upper Oligocene sequen ces of the Eastern Ebro Basin.The lacustrine systems must be regarded as "Depositional Groups" or "DeposÍtional Systems" in the sense of FrsHER & MCGOWEN (1969) and comprise severa] minor lithostratigraphic units with the range of Formation.Figure 2, based on ANADÓN et al. (1989) shows the schematic distribution of the lacustrine systems and their relationship with the alluvÍal systems in the Eastern Ebro Basin.In the present work, we will only mentÍon the units related wÍrh the distribution of the charophytes or units with special srratigraphic interesr.
The distribution of charophytes presented Ín this paper is based on sampIes referred to stratigraphic secrÍons or mammal sites  which have been correlated by mean of key beds in aerÍal photographs and geologic maps.The result of these lithostrarigraphic correla tions has been shown Ín TabIes 1 ro 5.The charophyte disrribution of the sampIed sectÍons .. .. :..:.. :......  have been grouped in 5 areas (Figs. 1 and 2) which correspond ro stratigraphic record ranges that can be correlated arnong thern.In sorne places, a certain degree of conternporaneity exists arnong these ranges.

The charophyte species
In the Upper Eocene -Lower Miocene sequences of the Ebro Basin, we have found thirty two charophyte species.Most of these species have been reported previously frorn other areas in the nurnerous studies which have been carried out during the last two decades on the Cenozoic charophyte floras of Europe.In arder tú sirnplify the following report, we will frequently refer to the synoptic study of RrvELlNE (1986) which surns up the papers prior to  (1987) and to the correlation charts of the Paleogene European mammal reference levels of SCHMIDT-KlTTI.ER (ed. 1987) abbriged MP.The species recognÍzed in the present study, documented below, all belong to the Characeae family.
Harrísichara Jineata GRAMBAST 1957 Distribution and range in the Ebro Basin (arca 1, Fig. 1): there is only one record of this species, at the locality of El Pares, in the Vic area (COLOM et al. 1970).H. lineata is rep resented there by more globular specimens and of higher dimensions than in the Paris Basin, but these differences are considered to be within the límits of variatíon of the species.

Harrisichara tubercuJata (LYELL) GRAMBAST 1957
Distribution and range in the Ebro Basin (areas 1-3, Figs.3-5, Tables 1-3): this species occurs abundantly in a number of horizons of Upper Priabonian and Lower Stampian age.The dating of the Calaf FormatÍon is critical for the upper extension limit of the species and thus for the range of the Bembridge zone (CASTEL 1968), or H. tuberrnlata superzone (RIVELlNE 1986).
The lowermost stratigraphic occurrence of this species is in the San Cugat de Gavadons mammal site (Theridomys golpeae local zone, MP 19); the uppermost occurrence is in the Conill section, stratigraphically located between the Porguerisses mammal site (Th.calafensis local zone, according to Anadón et al. 1987, MP 21-.'vlP 22) and the Timega mammal 5ite (Th.major zone, MP 23).
Other occurrences: the species, widespread in Europe, has never been mentioned in localities more recent than Lower Stampian.In particular it is absent in the charophyte and mammal locality of Villebramar which is typical of the standard leve!MP 22 (SCHMIDT KITTLER (Ed.) 1987).The extension of the species in the Isle of Wight, which is its type area, is also significant; H. wberculata extends from the Bembridge Limestone to the Lower Ham stead Beds (FEIST-CASTEL 1977a), but ir is absent in rhe superceeding L'pper Hamstead Beds (Cerithium Beds, Bouldnor Clif, sample C. 300, UniversÍty of Montpellier II).Outside of the Ebro Basin, the range of the species is thus restricted to the Upper Priabonian Lower -Stampian.However, its presence in the Calaf beds implies that it may extend higher, in the time interval corresponding to charophyte biozone 4, during which sorne endemic taxa occur red in the Ebro Basin, such as Chara sp. 2 and Nodosochara jorbae (Table 2).
Upper Eocene -Lowermost Miocene charophyte succession in the Ebro Basin (Spain)

Harrisichara vasiformis-tubercuJata
This informal species name was proposed to designare the transitional forms fram H. mis to H. tuberculata 1977a).These forms have been taken as index species for the establishment of a Late Eocene zone, due to rheir wide geographic distribution (RrvELINE 1986).This zone only covers the lower part of rhe species range.
Distribution and range in rhe Ebro Basin (area 1, Fig. 3, Table 1): the occurrence of the species in the Moia section, at the lower part of the Artes Formation, corresponds to its upper range, coexisring with the lowest occurrence of H. tuberculata. Other
Otber occurrences: R. major has be en reported from Nortbern and Sourhern France, Switzerland and Germany (see RIVELINE, 1986).It spans the upper Lower Stampian and Upper Stampian.

Rhabdochara praelangeri CASTEL 1967
Distribution and range in tbe Ebro Basin (Fig. 1, area 5, Table 5): the species bas been found in the Bot sectÍon, from beds of the Upper Oligocene F1ix Formation whích bave been correlated litbostratigrapbically witb tbe Gandesa beds which are included in the Eomys zitteli mammal zone (AGusTÍ et al. 1987, MP 26).
Other oeeurrenees: in addition ro the type-loeality near Marseille, the species has been reported from numerous loealities in Franee, Germany and Switzerland.It ranges from the Upper Stampian ro the Lower Aquiranian (FEIST-CASTEL 1977a;CHELLAl et al. 1982;RIVELINE 1986).

7.
Rhabdochara langeri (ETTINGSHAUSEN) MADLER Distribution and range in the Ebro Basin: (areas 4, 5; Figs. 6, 7; Tables 4, 5): the speeies is present in the Upper Oligoeene sequenees of the Margalef Formation and of the Granja d'Escarp Lutites, in the Mas de Maials and Aspa areas.Its lowest occurrence is in beds correlated from stratigraphical position with E. major zone (MP 27).The upper oeeurrence of the species is in beds referred to the E. aH.major zone, equivalent to the MP 27 and MP 28.

Rhabdochara aff. altilis FEIST-CASTEL 1977a
Specimens from the Ebro Basín desígnated under this name differ from the typical R. altilis in lacking a basal funnel and presenting a rounded, instead of truncated, apex (CHor 1989).Distribution and range in the Ebro Basin (area 1, Fíg.3, Table 1): rhis form is represented in the Artés Formation.Its lowest occurrence ís in the lower part of the Calaf and Moia sections, in beds several ten s of metres stratigraphically aboye the Sant Cugat mammal site (Th.golpeae zone) which can be referred indifferently to the Th.golpeae or to the Th.aH.aquatilis zones (MP 19120 or MP 21).The upper occurrences of this form is in the Santpedor mammallocality attributed to the Lower Oligocene Th. aH.aquatilis zone (AGUSTÍ et al. 1987, MP 21).From Rodent evidence, this form extends, in the Ebro Basin, from the Lower Priabonian ro the Lower Stampian.
Oeeurrences of Rh. altilis: typical representatives of the species have been reported from two localities of the Mormoiron Basin, in Southern France, both of Upper Priabonian age (FErsT-CAsTEL 1977a).

9.
Rhabdochara aff.raibocarpa FEIST-CASTn 1977a Close to R. raibocarpa in general shape and apical structure of the gyrogonites, the catalan form differs clearly in its smaller dímensions.Distribution and range in the Ebro Basin (areas 1,2; Figs.3,4; Tables 1,2): this form occurs abundantly in some levels of rhe Artes, Súria and Solsona Formations.Its lowest occurrence is stratigraphícally located between the Sant Cugat de Gavadons and Santpedor mammal sites, respectively reported ro the Th.golpae (MP 19) and Th.aH.aquatilis (MP 21) zones.The highest occurrence of the species is in the Fonollosa mammal site, referred ro the Th.calafensis zone .
Occurrences of R. raibocarpa: The species has been reported only from the type locality, in the MormoÍron Basin (South of Franee).

Stephanochara aH. vectemis (GROVES) GRAMBAST in RIVELINE 1986
Two different forms are grouped under this denomination: a) In Bed 2 of the Fores section.specimens closely allied to S. vectensis but with a more conical shapc and a slightly more prominent basal part; the dimensions do not differ significantly.b) In beds O and 1 of the Sarral section, the form represented differs from typical representatives of the species only by their distinctly smaller dimensions.Distribution and range in the Ebro Basin (area 3, Fig. 5, Table 3): the lowest occurrence of S. aH.vectensis is in the Upper Priabonian Rocafort de Queralt mammal site, referred to the Th.golpae zone (MP 19).lts highest occurrence is aboye bed 2 in the Forés section, attributed the Th.calafensis zone .
Occurrences of Stephanochara 'vectensÍ5: the species has been reported from the Upper Priabonian of the Paris Basin and from the uppermost Bembridge Marls of the lsle of Wight.Reexamination of material from the Bembridge Limestone did not confirm the presence of S. 'vectensis, notably the specimens collected by Professor D. CURRY at Hamstead Ledge (e. 313, Professor GRAMBAST charophyte colIection, Montpellier University) and Gurnard Bay (e.315).Further collectings at Whitecliff Bay (e.2685c in PElST-CASTEL 1977a) were also nega tive.The species is absent, too, in the Bembridge Oyster Beds, twelve metres aboye the Bembridge Limestone (e. 316).Our research has shown that the range of this form, which is the index-species of a charophyte biozone, is restricted, in the Isle of Wight, to the Insect Limestone of the Bembridge Marls (specimens V. 18335, Natural History Museum, London).

11.
Stephanochara aff.pinquis GRAMBAST in RIVELINE 1986 The forms of rhe Ebro Basin allied to S. pinquis show similar general shape and dimensions but they differ in the less prominent apical nodules.This difference does nor seem to be a result of a lower degree of calcificaríon, as the spiral cells are clearly convex and thus well calcified.Distribution and range in the Ebro Basin (area 3, Fig. 5, Table 3): S. aff.pinquis occurs in the Tarrega Formation, in the uppermost beds of the Fores and El Talladel sections, attributed ro rhe Upper Stampian Th. major zone (MP 23), on mammal cvidence.
Occurrences of S. pinquis: this species is restricted to the Lower Stampian (RIVELINE 1986).In particular, in the Sierra Palomera (Teruel Province, Spain) ir is associated with the Rodent Theridomys aquatilis (ADROVER et al. 1983), attributable to the MP 21.

Gyrogona caeJata (REID & GROVES) GRAMBAST 1956
Extension and range in the Ebro Basin (areas 1, 2; Figs. 3, 4; Tables 1,2): the species is well represented in the Jorba La Panadella, Súria and Fonollosa sectÍons as well as in the Artes Formation and equivalent sequences, until the base of La Panadella Limestone.Its lowest occurrence is situated between the mammal sites of Sant Cugat de Gavadons (MP 19) and Santpedor (MP 21).The uppermost occurrence of G. caelata in the upper part of the Fonollosa section referred to the Th.calafensis zone (MP 21-MP 22) extends its range a few higher rhan the Lower Stampian.

19.
Gyrogona medicaginula LAMARCK Extension and range in the Ebro Basin (area 2, Fig. 4, Table 2): this species has been found only in the locality of Conill.The Conill beds are stratigraphically located between the mammal si tes of Porquerisses (Th.calafensis zone, MP 21-MP 22) and Tarrega (Th.majar zone, MP 23).Thus, up to date the exact mnge of this species in the Ebro Basin remains uncertain in relation to the mammal biozones.
Other occurrences: The species was previously known from the Lower to Upper Stampian of the Belgium and Paris Basin (RIVELlNE 1986) as well as from the Bavarian Untere Süsswas ser Molasse (BAUMGARTNER 1985).range of this species cannot be precisely determined due to its scarcity and its absence in well dated localities.

Chara microcera GRAMBAST & PAUL 1965
Distribution and range in rhe Ebro Basin (areas 3-5; Figs.5-7; Tables 3-5): this species occurs in a number of localities, from the Upper Stampian to the Lower Aquitanian.Its occurrence in bed 3 of the Solivella section, reterred to the Th.majar zone (MP 23) extends its range, which was previously known as starting in the Heimersheim (MI' 24) biozone (CHELLAI et al. 1982).
Orher occurrences: Chara micracera is widcspread in Europe, where it spans the Upper Oligocene and the Lower Miocene.

23.
Chara Other occurrences: this species is widespread in the Aquitanian and rarer in the Upper Oligocene.In the Swiss Molassic Basin, C. notata appears in the Rickenbach mammal horizon (BERGER 1986), attributed to the MP 29 standard leve!.

24.
Chara sp.A (Fig. 9) This form shows new conjunction of characters, but the diagnosis of a new species is not possib1e due to the small number of specimens found so faro The specimen represented (Fig. 9) shows a charoid apex and a pointed basal part that would characterize the genus Homichara but, in addition to the fact that the spiral cells are provided with a Chara-like ornamentation, the population of Chara notata from the Aspa-4 bed includes speeimens with a basal stalk and could be interpreted as transitional with the new form, that would question the validity of a new taxon.Distribution and range in the Ebro Basin (area 4, Fig. 6, Table 4): Chara sp.A has been found in the Mas de Maials and Sarroca sections, in beds correlated with the Upper Oligocene E. aH.major zone (MP 27 and MP 28).

Lamprothamnium sp.
The presence of this genus is interesting in its palaeoecological significance; Lamprothamnium is asure indicator of present and past saline lakes.Recent analogs of sueh environments in the Coorong arca (south of Australia) are interpreted by BURNE et al. (1980) as being affected by seasonally varying salinities under semi-arid eonditions.Extension and range in the Ebro Basin (arca S, Fig. 7, Table S): this form has been found in sorne beds of the La Panadella, Fraga and Torrente de Cinca sequences dated from the Upper Oligocene by other fossil assemblages.

29.
Sphaerochara aH.subglobosa Specimens incompletely ealcified or not well preserved resembling S. subglobosa in their general shape, apex strueture and ornamentarÍon are doubtfully attributed to this species (CHOI 1989).
Distribution and range in the Ebro Basin (area 1, Fig. 3, Table 1): rhis form occurs in the Moia, Calaf and Fonollosa sections, from the Upper Priabonian to the Lower Stampian.Its lowest oeeurrence is stratigraphically placed between the Sant Cugat de Gavadons and Sant pedor mammallocalities (Th.golpeae and Th.aH.aquatilis zones), its uppermost occurrenee in the uppermost Calaf mammal site (Th.calafensis zone).

aH. major zone (MP
The species was also found in bed 19 of the Torrente de Cinca section, just aboye the TC-18 mammallocality, referred to the Eomys aH.major zone (MP 27).
Other occurrences: S. hirmeri is widespread in the Upper Oligocene of the European Basins but accordíng to RIVELlNE (1986), the species occurs in the Late Eocene Bembridge Marls of the Isie of Wight and its persistance into the Miocene is doubtful.Apart from the isolated record of the species in the Late its first occurrence is from the Stampian locality of Saínt-Vincent-de-Barbeyrargues (Languedoc; GRAMBAST 1962), referred to the MP 25 mammal standard level, thus quite simultaneously as in the Ebro Basin.

32.
Sphaerochara ulmensÍs (STRAUB) GRAMBAST Distribution and range in the Ebro Basin (areas 4, 5; Figs.6, 7; Tables 4, 5): the lowest occurrence of the species is in Aspa-4, which is tentatively referred to the E. major zone (MP Its uppermost occurrence is in parts of the Torrente de Cinca and Vellila de Cinca sections attributed to the Rh.transiens zone (MP 30).As reported below, records from other areas confirm this attribution.
Other occurrences: S. ulmensis was recorded, in Europe, from the Upper Stampian to Tortonian in Switzerland, from the Chattian and Aquitanian of Germany (MADLER 1955) and from the Aquitanian of Southern France (FEIST-CASTEL 1977a).The species is widely distri buted as it was also reported from the Upper Oligocene of China (HUANG 1978, PI. 9, Figs. 1-5).The lowest occurrences of the species is in the Aarwanger Molasse of Switzerland (HORN AF RANTZIEN 1959), referred to the MP 27 mammal standard level.

IV. Charophyte biozonation of the Upper Eocene-Upper Oligocene sequences
The wide geographical extension and relatívely short ranges of charophyte species on subdividing and correlating Cretaceous and Paleogene non-marine sequences.With regards to the Paleogene of Europe, after the pioneer studies of CASTEL (1968) and GRAMBAST (1972), RIVELINE (1986) defined 20 zones based on the first occurrences of charophyte index species and on their assemblages.Our study on Paleo gene Mesogena floras gives us the opportunity to update this biozonatíon with definíng new zones and delimitating others more precisely.We will first determine the succession of the local zones established in the Ebro Basin with the species represented (Table 6), rhen we will place them in rhe context of the whole Paleogene Zonal succession of the European Basins (Table 7), with the inferred modifications (Table 7).

A. Charophyte succession in the Ebro Basin
Local biozone 1 Definition: interval defined by the presence of I-larrisichara lineata.This species occurs, in the Vic area (COLOM et aL 1970), at rhe upper part of rhe Lower Priabonian Tossa Formation (FERRER 1971, LUTERBAcHER et al. 1973).The ranging up to the Upper Priabonian Sphaerochara labellata zone, its datarion cannor be esrablished precisely.Lamprothamniumsp .

Local biozone 2
Definitíon: ínterval between the first occurrence of Sphaerochara labellata and the fírst oc currence of Lychnothamnus longus in the Ebro Basin.forms of S. labellata occur in the Rocafort de Queralt sequences exposed at the locality with the same name.This zone is also developped in the Moia and Sant Cugat de Gavadons sections.
Important species: H. tuberculata and S. aH.vectensis and R. stockmansi which appear simultaneously with S. labellata.
Zonal attribution: Sphaerochara label/ata zone.This newly defined zone corresponds to the lower part of the Stephanochara vectensis zone of RrvELINE (1986).Correlation of S.

Local biozone 3
Definiríon: inrerval between the first oceurrence of Lychnothamnus longus and the first oc currenee of Nítellopsis meTiani.Early forms of L longus occur in the Calaf and ín rhe Espelt sections and the zone is developped in the lower part of the Arrés Formation exposed in these sections, as well as in the Fores section.
Table 4 Charophyte distribution in the stratigraphic sections of Area 4 (Fig. 6 l.Zonal attribution: local zone 3 is correlable in its assemblage with the Stephanochara vectensis zone of RIVELINE (1986), which must be revised from new informarion on rhe range of the index species in rhe Isle of Wight.In rhe Ebro Basin, S. aff.vectensis shows the same range and distribution than H. tuberculata.Local zone 3 is idenrified in rhe Bembrige Marls of the Tsle of Wight as well as in the Lower Mo!asse du Fronsadais, exposed at Baby-2 and Saint Capraise localities of the Aquitaine Basin, which are reterred to the MI' 20 mammal standard leve!.In the Ebro Basin, the top of local zone 3, which is placed in the Lower Stampian MI' 21-MI' 22 standard levels, does not correspond to the upper limit of the Stephanochara vectensis zone that is restricted ro the Late Eocene.
Table 5 Charophyte distriburion in the stratigraphic sections of Area 5 (Figs.7 and 8).Definition: interval between the first occurrence of Nitellopsis meriani and last occurrence of Harrisichara tuberculata.Early forms of N. meriani occur in the Jorba-La Panadella section and the zone is deve!opped in the Calaf, Súria, Fonollosa and Santpedor sections (Artes Formation).The base of zone 4 is placed within the Th.calafensis zone as it does in the Jorba La Pana della section which includes its lowest occurrence.
Zonal attribution: local zone 4 corresponds in its assemblage to the Stephanochara pinquis zone of RIVELINE (1986).This zone can be referred to the MP 21 mammal standard leve!, by correlation with mammal and charophyte associations of Soumailles, Ronzon and Hoogbutsel localities.The indexspecies has not been found in the Catalan localities.In the Ebro Basin, data from the Calaf mammal faunas imply the place the upper limit of the S. pinquis zone in the Mp21-MP 22.This attribution is not however consistent with the extension of the taxa which compose the assemblage of the S. pinquís zone, in particular the genus Harrísichara, which was never reported from the Rhabdochara major zone, correlated with the MP 22 standard level.

Undefined local biozone 5
Interval between the last occurrence of Harrísichara tuberculata and the first occurrence of ChaTa micracera.The uppermost part of the Jorba-La Panadella section, including bed 38, corresponds to this interval, which is also present in rhe Fores-Sarral section.

Local biozone 6
Definition: interval between the first occurrences of Chara microcera and Hornichara lagenalis.Early forms of C. micra cera occur in the Tarrega Formarion, in SolivelIa-3 and Montblanquet-3.The zone is also developped in the Fod~s and El Talladel sections.Important species: S. hirmeri; R. meljor, whose presenee in this imerval eorresponds tO the upper part of its range.
Zonal attribution: local zone 6 eorresponds to the lower part of the C. microcera zone of RIVELINE 1986 with an earlier lower the spceies appearing in an horizon referred to the MP 23 standard level, instead of MP 24 as previously known et al. 1982).This newly redefined C. mícrocera zone is eorre!ated with the Argiles des :\-1illes and with the Argiles de Saint-André (Somh of Franee), the latter correlated with the :\-lP 26 standard leve!.

Local biozone 7
Definition: interval between the first oceurrences of Hornichara lagenalis and Stephanochara ungeri.Early form of H. lagenalis occur in the Flix Formation, in bed 5 of the Frage B section, correlated with the E. majar zone, attributed to the :MP 27 mammal standard leve!.This zone is developped in the lower portion of the Mequinenza Limestone, appearing in the Fraga Section.Important species: Chara micro cera, persistant from zone 6. Zonal attribution: Hornichara lagenalis zone corresponds to the Upper pan of the Chara micro cera zone previously defined by RIVELINE (1986).Out of the Ebro Basin, the new zone is identified in the Lower part of the "Molasse rouge" of the Geneva Basin (BERGER et al. 1986); thus in the SPM5 Borehole, the !owest occurrence of H. lagenalis is below the S. ungeri one, as reported in the Ebro Basin.

Local biozone 8
Definirion: interval between the firsr occurrences of Stephanochara ¡mgeri and Stephanochara berdotensis.Early form of S. ungeri occurs in the Frage-7 horizon, referred to the E. aH.major zone, attributed to the MP 27 mammal standard leve!.This zone is represented in the Fraga, Velilla de Cinca and Mequinenza sections.
Zonal attribution: zone 8 corresponds to rhe S. ungeri zone of RIVELINE (1986) and BERGER (1986).Out of the Ebro Basin, this zone is identified in the Pelarda Formation, at the Vive! del Rio and Villanueva del Rebollar mammallocalities (Teruel Basin;ADROVER et al. 1982), attributed to the MP 28 and MP 29, respectively; In Aquitaine, local zone 8 is develop ped in rhe upper part of the Molasse de l' Agenais, ar the La Milloque locality & RINGEADE 1977), referred to the MP 29; in the Swiss Molasse, from the Wynau to Rickenback mammallevels (KISSLING 1974;BERGER 1986), thus from MP 27 to MP 29.

Local biozone 9
Definition: base of zone 9 is based on the lowest occurrence of Stephanochara berdotensis.Early form of S. berdotensis occurs in bed 48 in the Torrente de Cinca section, referred to the Rh.transiens mammal zone, attributed to the MP 30.Top of zone 9 is not defined due to rhe, up to date, not recorded occurrence of the Lower Aquitanian markers (Rantzieniella nitida GRAMBAST, Sphaerochara davidi FEIST-CASTEL).
Zonal atrribution and resulting changes in the general biozonarion: local biozone 9 is partíally equivalent to the Chara notata biozone of RIVELINE (1986) which is no longer defined, due to the new range of the index-species determined in the Ebro Basin (see aboye, Part lII, Chara notata); the Rantzienella nitida biozone, not identified in the Ebro Basín, will be placed over the S. berdotensis biozone, with its new definition.

B. Comparison of the Charophyte and MammaJ successions
The charophyte-mammal correlations established in the European Basins are based on a number of common localities, from the Lower Eocene onward 1968; FEIST-CASTEL 1977a;FEIST & RINGEADE 1977;RIVELINE 1986;BERGER 1986;TAMBAREAU et al. 1989).
In the Ebro Basin, the identificatian of the Upper Priabonian Sphaerochara labellata and Stephanochara vectensis zones in the lawer sequences is compatible with data fram Vertebrate faunas.In contras!, some differences appear between the two groups with regard to the identificaiton of the Lower Oligocene: the Eocene-Oligocene boundary based on the mam mals is spanned without any change by the charophytes and the Lower Oligocene Stephanochara pinquis zone is developped in the Theridomys calafensís mammal zone, corre lated with the Villebramar reference level.With regards to the previous charophyte records in this period, we admit that the S. pirlquis zone may extend higher than its previous range, restricted ro the Ronzon-Hoogbutsel-Lower Hamstead leve!.With regard ro the Middle Stampian, only undefined local zone 5, starting with the estinction of H. tuberculata and finishíng with the first Chara micro cera, could be referred ro the Rhabdochara major zone.Charophyte and mammal indications are concordant for the Upper Stampían, Upper Oligocene and Lower Miocene sequences; the unabilíty of charophytes in defining the basal Aquitanian ís due ro the local absence of stratigraphically significant markers.

C.
The Ebro Basin Charophyte succession in the framework of the standard European biozonation (Table 7) The zonation established in the Ebro Basín is based on contÍnuous sectíons correlated one with each others inside a same area.The precision obtained in de!imitating the species ranges and the composition of the successive assemblages leads to deeply modify the previous zona tions.With regard with the more recem one, from RIVELINE (1986), the main changes consist in: 1) the suppression of two zones, which became invalid following the lengthen of the index species ranges; 2) a new definiríon of the Stephanochara vectensis and Chara mio'ocera ZOnes; 3) the adjonction of two new zones, the Sphaerochara labellata zone in the Lower Stampían and rhe Hornichara lagenalis zone in the U pper Stampian.On the orher hand, data fram micromammals lead to extend the range of the assemblage characterizing the Stephanochara vectensis bíozone higher than the MP-20 (Saínt Capraise) leve! and the Stephanochara pinquis zone higher rhan the Ronzon leve!, thus between the Ronzon and Villebramar mammal standard leve!s.

V. Oligocene extinction event in Charophytes
Table 6 shows that the charophyte assemblages succeed regularly in the of the Ebro Basin.It is evident, however, that the species number varies from twemy for the three zones representing the Priabonian and Lower Stampian imerval, corresponding to about five million years, to only twelve species for rhe whole younger zones during the same duration.Considering the assemblages represented in zone 4, we note that the extinctions of species are increasing in ZOne 4, fram base to summit (T ables 1 and 2).These disparitions, not compensed by the recovery of new species, lead ro a drastic ímpoverishment of the charophyte phylum during the Lower-Middle Oligocene transition.
The impoverishment of the group seems a general phenomenon derived from the exdnc tions occuring between the Stephanochara pinquis and Rhabdochara major zones.Charophy tes beÍng direcdy influenced by potendal calcium carbonate precipitarion, which is tempera ture-contralled, the Middle Oligocene cooling (KEIGWIK & KELLER 1984) may be evocated as major factor of extinctions.This hypothesis is supported by the conrrasting evem of speciation during the Upper Oligocene, coinciding with the general warming which seems to have occurred during this period (MILLER & FATRBANKS 1985; VIANEY-LIAUD 1991).

VI. Conclusions
As a main result of the present paper, a new charophyte zonal scheme, based on the Ebro Basin succession, is proposed for the Eocene-Lower Miocene interva!.Mosr species .¡:.. g. (1) ~.
-_.. Newly defined New biozone biozone being widely distributed, the new zonal scheme is applicable to the whole Western Europe.\X1ith distant areas, only broad correlations, based on rare common species, can be presently cstablished ..Kotably, such correlations can be established with Asia (China, India).
On the other hand, the comparison of the charophyte and mammal zonations shows that, from the Lower Oligocene onward, the latter is twice more precise, in contrast with the previous periods: the number of Eocene zones is similar in charophyte and mammals zona tions and, for the Cretaceous, eighreen zones subdivide the Cretaceous but none has been defined sofar in the vertebrares, al' least in the old world.
Finally, relations between the change in generic and specific diversity and the general climatic changes have been evidenced: decreasing diversity corresponding ro the Middle o Coumon -28 Oligocene cooling and, contrastingly, recovering of diversity during the Upper Oligocene warming phase.We expect, from current isotopic studies, more precise data on rhe rem peratures that prevailed, during the Oligocene, in the Ebro Basin.
Fig,l.The Eastern Ebro Basin map with areas used this Schematic stratigraphic cross section of ¡he Upper Priabonian-Lower Aquitanian basin fill in che Eastern Ebro B asin. imponant marine -non-marine cyelea Iinked to two major transgressive maxima : Ilerdian (Early Eocene) and Bartonian (MiddIe -Late Eocene).In the northern areas of the Ebro Basin these two cyeles are well recorded whereas in the southern areas non-marine sedimentation was continuous throughout the Paleogene.During the Late Eocene a rapid regression took place and non-marine conditions spread al! over the Ebro Basin.

Fig. 3 .
Fig.3.Stratigraphic logs in the Upper Eocene-Lower Oligocene non-marine deposits of are a 1. See Figs. 1 and 2 for location and stratigraphic position.See charophyte distribution in Table1.
logs in the Upper Oligocene deposits of area 5.The correlation corresponds to an cross section.This section links ¡he correlation of profiles in Figure6wi¡h ¡hose in Figure7.1984.Moreover, we refer the Paleogene mammallocal biozones to the work of AGUSTÍ et al.
zone wi th the MP 19-MP 20 mammal standard levels is based on common localiries of charophytes and mammals in the Aquitaine and Ebro Basins.This zone is widely repre sented, in particular in the Calcaire d'Issigeac, in Aquiraine, and in rhe Bembridge Limestone of the Isle of Wighr (FEIST & RINGEADE 1977; FEIST-CASTEL 1977a).

Table 3 .
lipper Eocene Lowermost Miocene charophyte succession in the Ebro Basin (Spain) Fig.5.Composite of the Forés and Sarral sections.Correlation \Virh El Talladell and Santa Coloma de sho\Vn.Area 3 in Figs. 1 and 2. See charophyte distribution in occurrences: this form has been reponed from the Isle of Wight, Paris Basin and lychnothamnoides FEIST in FElST & RINGEADE 1977 Distribution and range in the Ebro basin (area 1, Fig.3, Table 1): this species occurs only in the uppermost beds of the Calaf section which are attributed ro the Th.calafensis zone (MP 21-MP 22).Other occurrences: S.lychnothamnoides has previously been reported from rhe Upper Eocene of the Aquitaine Basin, France (FEIST & RINGEADE 1977) and from the Lower Oligocene of the Western Iberian Chains (ADROVER et al. 1983).13.Stephanochara aH.edwardsií GRAMBAST in RIVELINE 1986 This form closely resembles typical represenrarives of rhe specÍes, apart from its smaller dimensions.It shows little variation in its different occurrences in the Ebro Basin.Distribution and range in Ebro Basin (area 1, Fig.3, Table 1): S. aff.edwardsii occurs in several horizons of the Artes, Súria and Solsona Formations, notably in the Sant Cugat de Gavadons, Santpedor and Fonollosa mammal ocalities.Ir ranges from the Th.golpeae ro the Th.calafensis zones (MP 19 to MP 21-MP 22), thus from the Upper Priabonian to the Lower Stampian and lower Upper Stampian.Occurrences of S. edwardsii: rhe species was previously recorded only from the Paris Basin and from rhe Isle of Wight where its extension is restricted ro the Lower Priabonian ("Lower Ludian"; RIVELlNE 1986).

Table 5
KITTLER 1987)eonsiderably extends its range, previously known as restricted to the Upper Aquitanian and thus rhe eharophyte zone based on its lowest oceurrenee is no longer defined.Other occurrences: this species was recorded previously from the Upper Aquitanian of the Aquitaine Basin, which is its type area, and from severallocalities of the same age in rhe Swiss Molassic and París Basins (seeRIVELlNE 1986).Lowermosr Miocene charophyte succession in the Ebro Basin (Spain) Panadel1a Montmaneu Limestone, referred to the Th.calafensis one, but it does not persist in the overlying Tarrega Limestone.ltthusoccurs in the Upper Eocene and Lower Oligocene.The lowest occurrence of this species is in the lowest Calaf bed and in the Moia section.Both sites are placed stratigraphically between the Sant Cugat de Gavadons and the Santpedor mammal sÍtes (Th.golpeaeTh.aH.aql,atilis biozones; MP 19-MP 21).lts uppermost occurrence Ís sÍtuated between the Porquerisses and Tarrega mammal sites, referred to the Th.calafensisand Th. major zones (MP 23), respectively.Orher occurrences: L. langl's has not yet been recorded from elsewhere.Extension and range in the Ebro basin (areas 1,2; Figs.3,4; Tables1,2): this species is well represented in the Artés Formation and lateral equivalent successions.It is particularly abun dant in the Th.aH.aquatilis zone (MP 21).Its possible occurrence in the Th.galpeae (MP 19) and Th.calafensis (MP 21-MP 22) zones can not be disregarded.Other occurrences: the species is presently known only from the Ebro Basin.
FEIST & RINGEADE 1977 in several secrions of rhe Mequinenza area.Irs lowesr occurrence is in the Upper Oligocene Fraga B-7 locality, related to rhe E. aH.m,¡jor zone (MP 27).The species extends into the Lower Miocene, deduced from rhe stratigraphic position of beds 24 to 39 in the Vellila de Cinca section, 20 ro 40 m above the mamma!sire referred ro the Rhodanomys schlosseri zone (MN 1).Orher occurrences: the species is widespread in the Gpper Oligocene and Lower .Miocene(FEIST-CASTEL 1977b)and, according to PAPP (1951), persists until rhe Tortonian.S. ungeri is recorded under its former invalid name "Croftiella escheri" byFEIST & KISSLlNG (in K1SSLING  1974), from the Lower Chattian onward and by BERGER (1986) under the name "gr.ungeri" in the S. ungeri zone, parallelized wirh rhe Aarwangen Mammal zone, also referred to the MP 27.We thus see rhat rhe first appearance of S. ungeri occurs simultaneously in the Ebro Basin and in the Swiss ~lolassic Basin.This fact strengthens the value of the species as zonal indicator.15.Stephanochara berdotensis FEIST inFEIST & RINGEADE 1977Extension and range in the Ebro basin (area 5, Fig.7, Table5): rhe species oecurs in several horizons of the Upper Oligocene sequences of the La Cuesta de Fraga Lutites and in the Lower Aquitanian Torrente de Cinca-68 mammallocality.The appearanee of S. berdotensis slightly below the Upper Oligocene Fraga W -7 locality, referred ro the R. transiens zone(ACUSTÍ et al. 1987(ACUSTÍ et al.  , 1988; MP 30: SCHMIDT-Extension and range in the Ebro Basin (are as 1-3; Figs.3-5; Tables1-3): L. longus occurs abundandy in the Artés Formation and lateral equivalenr successions as well as in the La Upper Eocene - ): this form has been found in beds of the Artés and La Panadella Formations and lateral equivalent sequences.Its lowest occurrence is in levels stratigraphically situated between the mammal sites of Sant Cugat de Gavadons (Th.golpeae zone, MP 19) and Santpedor (Th.aH.aquatilís zone, MI' 21).The uppermost occurrence is in beds overlying the Porquerisses mammallocality (Th.calafen sis, MP 21-MP 22).
notata GRAMBAST & PAUL 1965Distribution and range in the Ebro Basin(areas 4,5; Figs.6,7; Tables 4,5): the speeies occurs in the upper sequences studied here, in the Late Oligocene and at the Oligocene-Miocene transition.Its lower occurrence is in the Aspa section, referred to the E. majar zone (MP 27) Upper Eocene -Lowermost Miocene charophyte succession in rhe Ebro Basin(Spain)this fact resulting in a noticeable larger, lower extension of its range.Its uppermost occurrence is in the Velilla de Cinca Seetion, in beds corresponding to the Early Aquitanian Rh. sclosserí zone.
However, previous Miocene records are now to be reconsidered and the species probably extends in fact from the Wynau (MP 27) to the Ricken bach (MP 29) mammallevels(BERGER 1986)and is thus restricted to the Oligocene, as it does in the Ebro Basin.
(STRAUB 1952, FEIST-CASTEL 1977c)G, YANG & LEE 1978) Distribution and range in the Ebro Basin (area 5, Fig. 7, Table5): this species only occurs in sorne Upper Oligocene beds of the Mequinenza area.lts!owest occurrence is in bed Fraga B-5, that is placed few metres above the Fraga B-2 mammal site, attributed to the E. major zone (MP 26-27).The uppermost occurrence of H. lagenalis is in the Fraga W -4 mammal site, also included in the E. aH.majar zone.Other occurrences: H. lagenalís was reported from the Upper Oligoeene and Lower Miocene of the Swiss ami German molassic Basins(STRAUB 1952, FEIST-CASTEL 1977c)as well from Aquitaine & RINGEADE 1977).Othcr occurrenees: N. meríani is widely distributed in Europe, from the Lower Oligocene to the Upper Tortonian.lt5 known lowest occurrences were reported by FEIST & RINGEADE (1977) from the mammallocalities of Ruch and Pouquette, in the Aquítaine Basin, which are rcferred to the MP 21 standard level (RINGEADE 1987).
RIVELINE 1986)e speeies was only found in the lower part of the Fod:s seetion, attributed to rhe Th. calafensis zone.Other oeeurrenees: S. subglobosa was recorded from rhe Hampshire and Lower Saxonian Basins as well as from two localities in Southern Franee (seeRIVELINE 1986).Taking in account the oeeurrences in the Ebro Basin, the species extends from the Upper Priabonian ro the Lower Stampian.
FEIST in FEIST & RINGEADE 1977Distribution and range in the Ebro Basin (arca 3, Fig.S, Table 3): the species is only repre sented in rhe Upper Priabonian mammalloeality of Rocafort de Queralt attributed to rhe Th.