LOWER TOARCIAN FORAMINIFERA FROM THE N O R T H E R N SECTOR OF THE

ERIAN RANGE (SPAIN)

CONCHA H E R R E R O

HERRERO C. 1994. Lower Toarcian Foraminifera from the Northern Sector of the Iberian Range (Spain). [Les foraminiFeres du Toarcien inf~rieur dans les Chaines Ib~riques Nord-Occidentales (Espagne)]. GEOBIOS, M.S. 17: 287-295.

ABSTRACT

Lower Toarcian foraminifera from the Northern Sector of the Iberian Range have been studied. 3 agglutinating and 44 calcareous species have been recorded. The presence of typical species of the Lower and Middle Lias and the appearance of Saracenella aragonensis (RUG.) and Planularia obonensis (RUG.) characterize lowermost Toar- clan. Serpentinus Zone is detected by the appearance of the genus Citharina.

KEY WORDS: FORAMINIFERIDA, PALEONTOLOGY, BIOSTRATIGRAPHY, PALEOECOLOGY, UPPER LIAS, IBERIAN RANGE, SPAIN.

RI~SUMI~

Parmi les foraminif'eres du Toarcien inf~rieur du Secteur Nord des Chaines Ib~riques, on a trouv6 3 esp~ces agglutin~es et 44 ca|caires. Le Toarcien basal est caract~ris6 par la presence d'esp~ces typiques du Lias inf~rieur et moyen et par l'apparition de Saracenella aragonensis (RUG.) et Planularia obonensis (RUG.). La zone ~ Serpenti- nus peut s'identifier grace ~ l'apparition du genre Citharina.

MOTS-CLI~S : FORAMINIFI~RES, PALI~ONTOLOGIE, BIOSTRATIGRAPHIE, PALI~OI~COLOGIE, LIAS SUPI~RIEUR, CHAi- NES IBI~RIQUES, ESPAGNE.

INTRODUCTION The material presented in this paper was collec- ted in the Late Pliensbachian and Early Toarcian deposits of two outcrops located in the Sierra de la Demanda and Sierra de los Cameros, in the Northern Sector of the Iberian Range (Fig. 1).

Upper Lias foraminifera from this chain are still badly known. The micropaleontological back- ground for the present study includes four papers: two of them dealing with Toarcian foraminifera from two sections, Obon (Ruget 1982) and La Rambla del Salto (Herrero 1991a), in the Central Sector; other combining aspects of micro, macro- paleontology and sedimentology in the Lower Toarcian from the Sierra Palomera, Central Sec- tor (Arias et al. 1991) and the last one describing the Textulariina recorded in the Late Pliensba- chian and Lower Toarcian of the Iberian Range (Herrero 1991b). In the Northern Sector, no detai- led study has been made.

The sampled sequence can be divided into two main lithostratigraphic units (Goy et al. 1976) : "Calizas biocl~sticas de Barahona" Formation which is overlain by "Alternancia de margas y ca- lizas de Turmiel" Formation. Barahona Forn~a- tion comprises nodular bioclastic limestones with marls and marly limestones intercalations. In the Sierra de la Demanda, the upper boundary shows a well developed hardground. This Formation has yielded dmmonites indicative of Domerian age and can be recognized in the Sierra de la Deman- da while in the Eastern area of the Sierra de los Cameros changes latterally into an interestrati- fled bituminous limestones and marls, "Calizas y margas bituminosas de Pr~jano" Formation (Co- mas-Rengifo 1982). Turmiel Formation consists of rhythmic limestones and marls richly fossilife- rous. Three of the five Members, in which this unit has been divided by Goy et al. (o.c.), are stu- died in this paper and lies within Tenuicostatum, Serpentinus and lower part of Bifrons Zones (Fig. 1).

288

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F i g u r e 1 - Location map of the Lower Jurassic outcrops and collection localities in the Northern Sector of the Iberian Range. Carte de situation des affieurernents du Jurassique infdrieur et les sites de prdl~ve- rnent clans les Chaines Ib~ri- ques nord-occidentales.

M A T E R I A L A N D M E T H O D S

A total of 31 samples, 21 from Muro de Aguas and 10 from Barranco de las Alicantas, were pro- cessed for foraminifera. The sediment that com- poses most of the samples consists of marls and

marly limestones. 2 of them were barren of fora- minifera and in 7 samples less than 15 specimens were found. The sample disintegration procedure starts with soaking 100 gr. of the dry and coarse- ly crushed sediment in a solution of sodium hy- droxide, peroxide of hydrogen and water for 2-3

289

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P L I E N S B A C H I A N T 0 A R C I A N STAGE

S P I N A T U M TENUICOSTATUM SE R PE N TI NUS B I FRONS ZONE

SOLARE HAWSKERENBE MIRABILE SEMICELATUM STRANGEWAYSI FALCIFER SUBLEVISONI SUBZONE

Astocolus matul inus ( O ' O R B . )

- - - I c h t h y o l o r i o su lcoto ( B O R N . )

Lagena aphela TAPP

- - - Plonular=a i n o e q u i s t r l o l o ( T E R Q . )

P lonu la r ia pu lchra ( T E R Q . )

Soracene l ta sublaevis (FRANK. ) Marginul ina pr ima D' ORB.

. . . . . . . . . . . . Para l inou l ino lenero (BORN.)

Prodenta l ina terquemi ( D ' O R B . )

Pseudonodosaria mult icoslota (BORN.)

Ceratobul imin idae

Lentieulina toarcense PAY.

Marginul ina cf. i n te r rup to TERO.

Nodosar ia columnaris F R A N K

I ch thyo la r i a in tumescens ( BORN. ) As loco lus speciosus ( T E R Q . ]

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P seudonodosaria vulgota (BORN. )

Sp i r i l l i na i n f i m a (STRICK . )

Ammobacu l i t es ba r rowens i s TAPP.

Ich thyo lo r ia squamosa ( T E R Q . ~ BERTH. )

Eogu t tu l i na l iossica (STRICK. )

Adherent f o r a m i n i f e r a

Fa lsopalmula obl iqua ( T E R Q ) . . . . . . . . . . . . . . . . . . . . . . . Planulario cordiformis (TERQ.)

- - - - - Ammodiscu$ asper ( T E R O . }

- - - - - B r l z a l i n a l i o s i c a ( T E R Q . )

Nodosar ia cf. pe r l o to F R E N T Z .

- - - - - - Ber the l ine l lo invo lu ta ( T E R Q . )

. . . . P lanu lo r i a obonensis ( R U G . ) Sarocene l la araqonensis (RUG.)

Fatsapa lmula ju rens is ( F R A N K . )

Prodenfa l ina subs i l iqua (FRANK. )

. . . . Reophax denso T A P P

Ci thor ino col l iezi (TERQ. )

Len l icu l ina p a y a r d i RUG.

Astacorus chicheryi (PAY.)

. . . . . . . . . . . . . . . . . Nodosario hortensis T E R Q

Ci thar ina c lathrata ( T E R Q . )

- - - Lenticul ina bochardi (TERQ. )

- - - - - Planulor io p ro t roc ta (BORN. )

~ C i t h a r i n a iberica RUG.

Ci thar ina qrodata (TERO.}

- - -- - Icnthyalar io hau f f / ( FRANK.}

Nodosorio opheilocula TAPP

- - - - - Nodosarlo f rentzeni nora. nov

- - - - -- Nodosar io phobyt ica TAPP.

- - - - Nodosaria pulchro (FRANK.)

- - -- -- Prodentolina pseudocommunis (FRANK.)

Vaginulina tr iangula FRENTZ.

Figure 2 - S t ra t igraphica l dis t r ibut ion of Foramini fera from the Lower Toarcian of the Nor thern Sector of the Iber ian Range. Rdpartition stratigraphique des foramini[~res du Toarcien infdrieur dans les Chaines Ibdriques Nord-occidentalcs.

290

days. The n the sample is washed t h rough sieves wi th m e sh d i a me te r s of 60, 125, 250, 500 y 1000 ~m. For the taxonomic and quan t i t a t ive analysis the f ract ions >125, <250 y> 500 ~m were used. The fo ramin i fe ra were hand-picked unde r stereo- scopic microscope Wild M-8. The i l lus t ra ted speci- mens were pho tograph ied unde r scanning elec- t ron microscope Hi tachi S-2500 and Jeol JSM- 6400. The ge ne ra are a r r anged in accordance wi th the classif icat ion proposed by Loeblich & T a p p a n (1988).

F O R A M I N I F E R A L A S S E M B L A G E S A N D B I O S T R A T I G R A P H Y

For the La t e P l i en sbach i an and Lower Toarc ian in t he Bar ranco de las Alicantas ' Section, S ier ra de la Demanda , it has been used the ammoni t e scale of re fe rence es tabl ished by Comas-Rengifo et al. (1988). The scale proposed by Comas-Rengi- fo (1982), as well as recent unpubl i shed data , has been used for the Muro de Aguas ' Section, Sierra de los Cameros .

S P I N A T U M ZONE

The p re sen t Zone was only sampled at Muro de Aguas ' Section, S ie r ra de los Cameros . 20 species are ident if ied, 18 of t h e m are recorded in the Te- nu i c os t a tum Zone (Fig. 2).

Solare S u b z o n e The u p p e r pa r t of this subzone is charac te r ized by the p resence of Astacolus matutinus (D'ORB.), Ichthyolaria sulcata (BORN.) [P1. 1, fig. 9], Planu- laria inaequistriata (TERQ.) [P1. 1, fig. 2], P. pul- chra (TERQ.) [P1. 1, fig. 1], Saracenella sublaevis

(FRANK.), Marginulina prima D'ORB. [P1. 1, fig. 3], Paralingulina tenera (BORN.), Prodentalina terquemi (D'ORB.) [P1. 1, fig. 6], Pseudonodosaria multicostata (BORN.), Lenticulina toarcense PAY., Lagena aphela TAPP. and specimens belonging to the family Cera tobul imin idae ( inde te rminab le py- ritic casts).

H a w s k e r e n s e Subzone In addit ion to the species found in the Solare Subzone, Marginulina cf. interrupta TERQ., Nodo- saria columnaris FRANK., Ichthyolaria intumes- cens (BORN.), Astacolus speciosus (TERQ.) [P1. 1, fig. 5], Pseudonodosaria vulgata (BORN.), Ammo- baculites barrowensis TAPP. [P1. 1, fig. 4] and Spi- rillina infima (STRICK.) [P1. 1, fig. 7] a re identi- fied in the lower par t of the H a w s k e r e n s e Subzone. Besides, in the upper p a r t of th is subzone Ichthyolaria squamosa (TERQ. 8~ BERTH.) [P1. 1, fig. 8], Eoguttulina liassica (STRICK.) and adhe ren t foramini fera are recorded.

T E N U I C O S T A T U M ZONE

In the Tenu icos t a tum Zone, 29 species have been identified. As well as the species recorded in the Sp ina tum Zone, the first appearance of 7 species, res t r ic ted to th is same zone, takes place and ano- the r 4 also occur in the Se rpen t inus Zone. The n u m b e r of species ident i f ied in the p r e sen t zone is larger in the Barranco de las Al icantas ' Sect ion where the sed iments were deposi ted in a re la t ive well oxygenate d envi ronment .

Mirabile Subzone The last appearance o fA. matutinus (D'ORB.), I. sulcata (BORN.), I. intumescens (BORN.), I. squa-

P L A T E 1

Fig. 1 - Planularia pulchra (TERQUEM). 2M.228.57. Muro de Aguas. Solare Subzone. Fig. 2 - Planularia inaequistriata (TERQUEM). 2M.228.55. Muro de Aguas. Solare Subzone. Fig. 3 - Marginulina prima D'ORBIGNY. 2M.256.73.1. Muro de Aguas. Hawskerense Subzone. Fig. 4 - Ammobaculites barrowensis TAPPAN. 2M.256.85. Muro de Aguas. Hawskerense Subzone. Fig. 5 - Astacolus speciosus (TERQUEM). 2M.256.80.1. Muro de Aguas. Hawskerense Subzone. Fig. 6 - P r o d e n t a l i n a terquemi (D'ORBIGNY). 2M.256.63.1. Muro de Aguas. Hawskerense Subzone. Fig. 7 - Spirillina infima (STRICKLAND). 2M.264.91. Muro de Aguas. Hawskerense Subzone. Fig. 8 - Ichthyolaria squamosa (TERQUEM 8z BERTHELIN). 2M.264.89.3. Muro de Aguas. Hawskerense Subzone. Fig. 9 - Ichthyolaria sulcata (BORNEMANN). 2M.264.71. Muro de Aguas. Hawskerense Subzone. Fig. 10 - Paralingulina tenera (BORNEMANN). 1C.T.7.167. Barranco de las Alicantas. Mirabile Subzone. Fig. 11 - Falsopalmula obliqua (TERQUEM). 1C.T.10.245. Barranco de las Alicantas. Mirabile Subzone. Fig. 12 - Planularia obonensis (RUGET). 1C.T.12.335. Barranco de las Alicantas. Semicelatum Subzone. Fig. 13 - Saracenella aragonensis (RUGET). 2M.292.102.1. Muro de Aguas. Mirabile Subzone. Fig. 14 - Saracenella sublaevis (FRANKE). 2M.292.51. Muro de Aguas. Mirabile Subzone. Fig. 15 - F, oguttulina liassica (STRICKLAND). 2M.304.88.6. Muro de Aguas. Strangewaysi Subzone. Fig. 16 - Lenticulina toarcense PAYARD. 2M.304.113.1. Muro de Aguas. Strangewaysi Subzone. Fig. 17 - Pseudonodosaria vulgata (BORNEMANN). 2M.304.84.1. Muro de Aguas. Strangewaysi Subzone. Fig. 18 - Astacolus chicheryi (PAYARD). 1C.T.18.321. Barranco de tas Alicantas. Strangewaysi Subzone. Fig. 19 - Citharina iberica RUGET. 1M.58.107. Muro de Aguas. Sublevisoni Subzone. Fig. 20 - Vaginulina triangula FRENTZEN. 1M.58.109.1. Muro de Aguas. Sublevisoni Subzone. Scale bar 100 pm

G e o b i o s P1. 1 M . S . n ° 17 C. H e l T e r o

292

mona (TERQ. & BERTH.), L. aphela TAPP., P. inae- quistriata (TERQ.), P. pulchra (TERQ.) and S. su- blaevis (FRANK.) [P1. 1, fig. 14] takes place in the Mirabile Subzone, while Falsopalmula obliqua (TERQ.) [P1. 1, fig. 11], F. jurensis (FRANK.), Sara- cenella aragonensis (RUG.) [PI: 1, fig. 13], Proden- talina subsiliqua (FRANK.), Planularia obonensis (RUG.) [P1. 1, fig. 12] and P. cordiformis (TERQ.) are found for the first time. Ammodiscus asper (TERQ.), Brizalina liasica (TERQ.), Nodosaria cf. perlata FRENTZ. and Berthelinella involuta (TERQ.) are only recorded in the present subzone.

S e m i c e l a t u m S u b z o n e In the Semicelatum Subzone, the last appearance of M. prima D'ORB., P. tenera (BORN.) [P1. 1, fig. 10], P. terquemi (D'ORB.), A. speciosus (TERQ.), P. obonensis (RUG.), S. aragonensis (RUG.), A. barro- wensis TAPP. and Reophax densa TAPP. takes place. P. multicostata (BORN.), P. vulgata (BORN.), L. toarcense PAY., S. infima (STRICK.), E. liassica (STRICIZ~), F. obliqua (TERQ.), F. jurensis (FRANK.), P. cordiformis (TERQ.), P. subsiliqua (FRANK.), specimens belonging to the family Ceratobulimi- nidae and adherent foraminifera remain and are recorded in the Serpentinus Zone as well. The se- diments in the boundary between Tenuicostatum and Serpentinus Zones show a discontinuity, hardground with a gap that comprises the upper- most Semicelatum Subzone and the lowermost Strangewaysi Subzone.

SERPENTINUS ZONE

In this Zone 14 species are found and the first appearance of Cithar'~ ,a takes place. 6 of them occur in the Bifrons Zone as well.

S t r a n g e w a y s i S u b z o n e Citharina coUiezi (TERQ.), Lenticulina payardi RUG. and Astacolus chicheryi (PAY.) [P1. 1, fig. 18] are identified for the first time. The last appea- rance of P. multicostata (BORN.), S. infima (STRICK.), E. liassica (STRICK.) [P1. 1, fig. 15], F. obliqua (TERQ.), F. jurensis (FRANK.) and P. sub- siliqua (FRANK.) takes place in the Strangewaysi Subzone. L. toarcense PAY. [P1. 1, fig. 16], P. vul- gata (BORN.) [P1. 1, fig. 17], P. cordiformis (TERQ.), Nodosaria hortensis TERQ. and adherent foraminifera are recorded in the Falcifer Subzone and the Bifrons Zone as well.

Falcffer S u b z o n e The first appearance of Citharina clathrata (TERQ.) takes place, as well as the species refer- red to above.

BIFRONS ZONE

Sublev i son i S u b z o n e In this Subzone, 17 species are found, 10 of them are only recorded in the Sierra de la Demanda, 1 in the Sierra de los Cameros and 4 are recorded in the both areas. The first appearance of Lenti- culina bochardi (TERQ.), Planularia protracta (BORN.), Citharina iberica RUG. [P1. 1, fig. 19], C. gradata (TERQ.), Ichthyolaria hauffi (FRANK.), Nodosaria apheilocula TAPP., N. frentzeni nom. nov., N. phobytica TAPP., N. pulchra (FRANK.), Prodentalina pseudocommunis (FRANK.) and Va- ginulina triangula FRENTZ. [P1. 1, fig. 20] takes place. Associated to these ones, L. toarcense PAY., P. vulgata (BORN.), P. cordiformis (TERQ.), A. chi- cheryi (PAY.), N. hortensis TERQ. and C. clathrata (TERQ.) are recorded.

F A U N A L F E A T U R E S

3 agglutinating and 44 calcareous foraminifera are identified. 22 of them, 2 agglutinating and 20 calcareous, are not common to the both areas stu- died. The genus Nodosaria comprises 6 species in the Barranco de las Alicantas' Section and 1 in Muro de Aguas' Section. 2 species of Citharina, C. colliezi (TERQ.) and C. iberica RUG., are com- mon to the both areas while C. clathrata (TERQ.) and C. gradata only appear in the Barranco de las Alicantas and Muro de Aguas, respectively. As well as, Prodentalina subsiliqua (FRANK.), Prodentalina pseudocommunis (FRANK.), Ammo- discus asper (TERQ.), Brizalina liasica (TERQ.), BerthelineUa involuta (TERQ.), Falsopalmula ju- renNiN (FRANK.), Reophax densa TAPP., Lenticuli- na bochardi (TERQ.), Planularia protracta (BORN.) and Ichthyolaria hauffi (FRANK.) are only recor- ded in the Barranco de las Alicantas and Astaco- lus matutinus (D'ORB.), Pseudonodosaria multi- costata (BORN.) and Marginulina cf. interrupta TERQ. are only found in Muro de Agnas.

In order to evaluate the foraminiferal-paleoenvi- ronmental relationships a quantitative t reatment of the foraminiferal assemblages is necessary. F~r all the species and all the samples, the rela- tive frequencies, the Shannon y Wiener informa- tion function and Pielou equitability index (in Beerbower & Jordan 1969) were calculated. In the same way, to quantify the degree of correla- tion among the species recorded, Pearson correla- tion coefficient (in Sokal & Rohlf 1969) was com- puted for the relative abundances of selected spe- cies. To test the significance of this correlation the computed value (ignoring sign) is compared

293

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[ ~ Dit(~lg ~ Eguff~bititg ]

The decrease of diversity seem to be associated with an increase of the relative frequencies of Lenticulina toarcense PAY. (compare Fig. 3a-b with Fig. 4d-e). The sample 4 (Semicelatum Subzone) in the Barranco de las Alicantas, shows high diversity and low relative frequency of L. toarcense PAY., the next sample, 5, above the dis- continuity between Tenuicostatum and Serpenti- nus Zones, shows low diversity and high relative frequency of this species. This fact suggests a possible opportunistic behaviour Cr" strategy) of L. toarcense PAY.. Following the return to favou- rable environmental conditions after an adverse period, opportunistic benthic foraminifera recolo- nize the area (Murray 1991). The high decrease of diversity in Muro de Aguas' Section from sample 12 to the end of the stratigraphical inter- val studied, can be related with unfavourable life conditions with oxygen-restricted bottom waters, accordingly the bituminous facies and the scarse content in benthic macro and microfauna.

The application of Pearson correlation coefficient to the relative frequencies of ten selected species (Fig. 4a-c) shows only significative negative corre- lations between Lenticulina toarcense PAY. and Paralingulina tenera (BORN.) in both sections and between Lenticulina toarcense PAY. and Astacolus chicheryi (PAY.) in the Barranco de las Alicantas' Section. The negative correlations are also reflec- ted in the relative frequencies of these species (Fig. 4d-e) ; p.e. when the abundance of L. toar- cense PAY. increases, the abundance of P. tenera (BORN.) decreases. It is probable that the popula- tional strategies of A. chicheryi (PAY.), L. toar- cense PAY. and P. tenera (BoR'~.) were opposed.

F i g u r e 3 - a, D i v e r s i t y and E q u i t a b i l i t y Ind ices in t he B a r r a n - co de las Al ican tas . b , D i v e r s i t y and E q u i t a b i l i t y Ind ices in M u r o de Aguas . S O : So la re Subz. H A : H a w s k e r e n s e Subz. M I : Mirab i le Subz . S E : S e m i c e l a t u m Subz. S T : S t r an g e - w a y s i Subz . F A : Fa lc i fe r Subz . S U : Sub lev i son i Subz. a, In- dices de Diversit~ et d~quitabilitd dans la coupe du Barraneo de las Alicantas. b, indices de Diversitd et d'Equitabilitd dans la coupe de Muro de Aguas. S O : sous-zone 6 Solare. H A : sous-zone 6 Hawskerense. M I : sous-zone 6 Mirabile. S E : sous-zone 5 Semicelatum. S T : sous-zone & Strangewaysi. FA : sous-zone 6 Falcifer. S U : sous-zone 6 Sublevisoni.

with the critical table value (r) of t-Student dis- tribution. Since the computed value exceeds the critical value (r) the species abundances are cor- related.

In both sections medium to low diversities are ob- tained (Fig. 3a-b). In most of the samples the low equitabilities (Fig. 3a-b) show the dominance of one species, Lenticulina toarcense PAY. (see re- lative frequencies in Fig. 4d-e).

C O N C L U S I O N S

All the foraminiferal assemblages from the Late Pliensbachian and the Lower Toarcian are domi- nated by the suborder Lagenina, family Vaginuli- nidae (sensu Loeblich & Tappan 1988), that shows relative frequencies higher than 50%. The abundances of the other suborders, Textulariina, Spirillinina, Robertinina and Rotaliina, are lower than 15%. In relation to Nodosariidae the pre- sence of more species of Prodentalina and Nodo- saria in the Barranco de las Alicantas' Section is remarkable.

The genera Paralingulina, Saracenella, Marginu- lina, Citharina and some species of Planularia, Ichthyolaria and Lenticulina show the most bios- tratigraphical and chronostratigraphical interest. The last appearance of P. tenera, P. terquemi, S. sublaevis, P. inaequistriata, M. prima, I. sulcata, I. intumescens and A. speciosus takes place in the

294

a P . t e n e r a l ' . t e r q u e m i L . t o a r c e n s e A . m a t u t i n u s M . p r i m a

P. t enera 1.000 0.380 -0 .809 0.028 0.015

P. t e r q u e m i 1.000 -0 .515 0.003 -(}.317

L. t o a r c e n s e

A . m a t u t i n u s

n = 8

r = 0.707 (5%)

0.834 (1%)

1.000 - 0 . 5 3 0

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0.238

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[I l.intume. P.t~nera P.terquemi L toarcense [ A.specious M.prima P.cordifo. !)

l . intumescens 1.000 -0.879 -0.261 0.880 -0.551 -0.853 -0.232

P.tenera 1.000 0.562 -0.998 0.230 0.739 0.659

! P. terquemi

L. toarcense

A.speciousus

M.prinm

1.000 -0.521 0.200 0.555 0.602

1.000 -0.198 -0.711 -0.664

n = 4

r = 0.950 (5%)

0.990 (1%)

1.000 0.817

1.000

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0.079

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1.000 - 0 . 9 1 2 0.680

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SE ~ FA ~

~ 7 0 - - - - Q , - - " - -

,::- 50

3(I

20

'°2. o

8 9 10 I 2 3 4 5 6 7 S,'Unl)h~

I -,J,-- Pt~mcrn -.m IJvmm~.sc -o - ,tddd,cry~ t

O0 ~ - i E m ~ - - - ~ - - 7

. , , + . - . - . . . . . . . . . . . . ! -4 + - 4 . . . .

10 - ~ ! / . . . . . . . . . . . . . . . . 3'

1 2 3 4 5 6 7 9 lO 1! 12 13 14 15 16 17 18 19 20 21 Sampk:s

Figure 4 - a, Pearson Correlation Coefficient for selected species in Muro de Aguas' Section. b y c, Pearson Correlation Coeffi- cient for selected species in the Barranco de las Alicantas' Section. d, relative frequencies for the species with significative correlation in the Barranco de las Alicantas. e, relative frequencies for the species with significative correlation in Muro de Aguas. SO : Solare Subz. ttA : Hawskerense Subz. MI -" Mirabile Subz. SE : Semicelatum Subz. ST : Strangewaysi Subz. FA : Falcifer Subz. SU : Sublevisoni Subz. a, coefficient de Correlation de Pearson pour quelques espOces dans le coupe de Muro de Aguas. b y v, coefficient de Correlation de Pearson pour quelques esp~ces clans la coupe du Barranco de las Alicantas. el, Frgquen- ces relatives des esp~ces avec corrdlations significatives dans la coupe de Barranco de las Alicantas. e, frdquences relatives des esp~ces avec corrdlations significatives dans la coupe de Muro de Aguas. SO : sous-zone & Solare. HA : sous-zone d Hawskerense. MI : sous-zone it Mirabile. SE : sous-zone ~ Semicelatum. S T : sous-zone ~ Strangewaysi. FA : sous-zone d Falcifer. S U : sous-zone d Sublevisoni.

295

Tenu icos t a tum Zone as well as in other outcrops in the Iber ian Range and o ther european basins (Exton 1979 ; Ruge t 1982 ; Copes take & Johnson 1984 ; Riegraf 1985; Mira 1986 ; Nicollin & Ru- get, 1988 ; Her re ro 1991a ; Arias et al. 1991). P. obonensis and S. aragonensis are res t r ic ted to Te- nu icos t a tum Zone, a l though in o ther basins they were also recorded in the Serpen t inus Zone (Ni- collin & Ruge t 1988). Species like L. payardi and A. chicheryi are found for the f irst t ime in the Serpen t inus Zone as well as in o ther sections of the Iber ian Range (Ruget 1982 ; Herrero 1991a ; Arias et al. 1991). The first appearance of Citha- rina t akes place in Serpen t inus Zone as well as in o ther bas ins (Exton 1979 ; Riegraf 1985 ; Ni- collin & Ruge t 1988) wi th the exception of Nor th Wales in which the first record of this genus oc- curs in Tenu icos t a tum Zone (Copestake & Johnson 1984).

The analysis of the relat ive frequencies, diversity, equi tabi l i ty and correlat ion shows the dominance of Lent icul ina toarcense PAY. in the s t ra t igraphi- cal in terval f rom Late Pl iensbachian to Lower Toarcian. This species seem to be a pioneer in the recolonizat ion of new biotopes and shows an opportunis t ic behav iour ("r" strategy). Stress si- tua t ions such as poor oxygenat ion of bot tom wa- ters are detected by ve ry low diversit ies and equi- tabili t ies as well as by the l i thology and macro and microfossil content .

A c k n o w l e d g m e n t s The author gratefully acknowledge the critical review of the manuscript by Dr. Antonio Goy and by the anonymous reviewers. Discussions with Ana Garcfa-Forn6s were most helpful. The SEM photographs were done at the Centro de Microscopia of the University Complutense of Madrid and at the Servei Central de Microscopia Electrbnica of the University of Valencia. Photograph reproductions by Eulogio Martin were greatly appreciated. This work has been supported by the Project PB88-0066 DGICYT-CSIC.

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C. H E R R E R O Departamento de Paleontologia Facultad de Ciencias Geologicas

Universidad Complutense Ciudad Universitaria s/n

28040 Madrid, Spain