Ciencias daTerra (UNL)pp.199-208

.·4 Figs., 1 PI.2003

Upper Miocene planktonic foraminifera from Algarve.Chronostratigraphical implications

Paulo Legoinha

Work supported by the Project "Studies on Portuguese Paleontology (Post-Paleozoic)" (POCTI/CYT/3635 1/99-00)Centro de Estudos Geol6gicos (FCTIMCT), Universidade Nova de Lisboa, Faculdade de Ciencias e Tecnologia, Quinta da Torre, P-2825-ll4

Caparica, Portugal; pal@fct.unl.pt

Abstract

Key-words: Planktonic foraminifera; biostratigraphy; isotopic ages; chronostratigraphy; Upper Miocene; Algarve (Portugal).

New data on the planktonic foraminifera from the Upper Miocene Cacela Formation and Mem Moniz spongoliths are presented.The coiling type of Globorotalia menardii from Cacela and Quelfes and the occurrence at Quelfes of G. miotumida allow

correlation with the bio-events 1 to 3 (7,512 to 7,24 Ma; Sierro et al., 1993; 2001) that have been recognized in the GuadalquivirBasin (Spain). The presence of Neogloboquadrina acostaensis and N. humerosa at Mem Moniz points out to the Upper Miocene(Tortonian, upper N16, or even N17). Mem Moniz spongoliths are correlated with the Cacela Formation.

Some S7Srf86Sr isotopic ages ofmollusc or foraminifera shells don't fit well with finer biostratigraphic record and present wideerror margins.

Resumo

Palavras-chave: Foraminiferos planct6nicos; biostratigrafia; idades isot6picas; cronostratigrafia; Miocenico superior; Algarve(Portugal).

Sao apresentados novos dados acerca da biostratigrafia do Miocenico superior do Algarve (Formayao de Cacela e espongolitosde Mem Moniz). as foraminiferos planct6nicos de Cacela e Quelfes, em especial 0 tipo de enrolamento de Globorotalia gr. menardiie a ocorrencia de Globorotalia miotumida (em Quelfes) permitem correla<;oes com os bio-eventos I a 3 caracterizados na Bacia dbGuadalquivir (7,512 to 7,24 Ma; Sierro et al., 1993; 2001). Neogloboquadrina acostaensis e Neogloboquadrina humerosa nossedimentos de Mem Moniz perrnitem data-los do Miocenico superior (Tortoniano, parte superior de N16 ou mesmo N17) ecorrelaciona-Ios com a Formayao de Cacela.

Verifica-se desfasamento entre a informayao biostratigrafica, mais fina, e data<;oes 87Sr/S6Sr, que evidenciam grandesmargens de erro.

Introduction

A comprehensive study ofthe chronostratigraphy oftheMiocene ofPortugal has been carried on. A synthesis on theNeogene ofAlgarve has been presented (Pais et ai., 2002).

The author has studied the Miocene planktonic foraminiferafrom the Lower Tagus Basin and Algarve (Legoinha,2001). In this paper new data are presented on planktonicforaminifera from the Upper Miocene ofAlgarve, especiallyfrom Cacela Formation and Mem Moniz spongoliths.

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The Cacela Formation (Antunes in Ribeiro el aI., 1979)is exposed in eastemAlgarve (Cacela, Quelfes). Basal levelsare conglomcratcs and limestones with pebbles. Upwards,there are muddy or calcareous, often glauconite-rich sands.This Formation contacts by angular unconformity withthe Triassic and by disconformity with the Lower to MiddleMiocene, Lagos·Portimao Formation.

White spongoliths with diatoms, calcareousnannoplankton, foraminifera, ostracoda and fishes outcropat Mem Moniz (Espongolitos de Mem Moniz; Romariz etal., 1979). These deposits fill a tectonic depression. Theconcerned unit was ascribed to the Serravalian orTortonian. However, several different age values had beenproposed. Chronology can be settled now. Sediments likethese are unknown elsewhere in Portugal.

The aims of this study are:

a) to review the published data concerning the planktonicbiostratigraphy ofCacela, Quelfes and Mem Moniz;

b) to discuss new planktonic foraminifera data andI1SrfS6Sr ages;

c) to improve the Upper Miocene chronostratigraphicknowledge of the Algarve;

d) to establish correlations with thc bio-events definedin the Guadalquivir Basin (Sierro et al., 1996).

Samples for foraminiferal study were disaggregatedwith a HP2solution, and washed in a 125 J.lm sieve.

CacelaLocation

Outcrops nearCacela (Fig. I). GPS coordinates: N 37°09' 46", W 7° 32' 48,6". The upper part can be observedat the locality named Fabrica.

Geological setting

Conglomerates and fine yellowish-gray sandstonesoutcrop at Ribeira de Caccia, corrcsponding to the basallevels ofthe Cacela Formation, Lower member. At Flibrica,there are fine yellowish-orange sands intercalated withlevels ofcarbonate concretions, the upper member of thesame Formation (Antunes et aI., 1981).

Cacela yielded the richest and best preserved Miocenemollusk fauna in Portugal. This fauna was described byPereira da Costa (1866; 1867), Cotter (1879; in Dollfus etaI., 1903-1904; in Choffat, 1950), Chavan in Bourcart &Zbyszewski (1940), Freneix {I 957) and Brebion (1957).

In the last 30 years, a systematic study ofthe Algarve'sNeogene have been carried on by researchers ofthe Centrode Estudos Geol6gicos, often in collaboration withforeign colleagues. The knowledge on paleontology,stratigraphy and chronology has been improved (essentialdata concerning Caccia, Antunes et aI., 1981; Antunes etal., 1990, 1997; Gonzalez-Delgado et al., 1995; Pais etal. 2000;Gonzalez-Delgado & Civis, 2000; Civiset al., 2000).

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Fig. I • Cacela Formation (Geological Map ofAlgarve, I:100000;Manuppella, 1992): Ribeira de CaccIa and Hbrica outcrops.

Bizon (in Antunes et aI., 1981) found Globigerinoidesexlremus, Globorotalia aff. conomiozea, Globorotaliapseudomiocenica, Globotalia menardii, Globorotaliaacoslaensis (sinist.) and Globorotalia humerosa (sinist.)that indicate the top ofNI6 or, probably, N17.

Sicrro (in Antunes et af., 1990) identified abundantplanktonic foraminifera at Fabrica, among othersGlobigerinoides extremus, Globigerinoides seigliei eNeogloboquadrina acostaensis (sinist.). The presence ofthe benthic Spiropleclammina carinata, which disappearsin the basal Messinian, was remarked. The foraminiferalassemblage points out to the Upper Tortonian.

According to Nascimento (in Antunes et af., 1981),the Ostracoda indicate a Messinian age.

Planktonic Foraminifera and biostratigraphic analysis

The samples Ribeira Cacela 2 and Filbrica 2 (Fig. 2)gave additional important data.

Ribeira Cacela 2 yielded sinistral menardiformGloborotalia. In the Guadalquivir Basin, Sierro (1985)and Sicrro et af. (1993) characterized a succession ofbio-events. The first one is the sharp reduction ofGloborotalia menardii group 1 (sinist.). The secondone is marked by the appearance of Globorotaliamenardjj group n (dcxt.). Betwcen these events, thetemperate waters of North Atlantic and Meditcrraneanwere almost deprived of keeled Globorotalia (Sierro etaI., 1993, p.l43).

Fabrica 2 yielded a rich and diversified planktonicassemblage, that does nol include keeled Globorotalia.This assembladge comprises (Antunes el al., 1990):Globigerino bulloides, Globigerina apertura, Globigerinadruryi, Globigerinita glutinala, Globigerinoidesbulloideus, Globigerinoides extremus, Globigerinoidesseigliei, Globigerinoides immaturus, Orbulina universa,Orbulina suturalis, Globigerina quinqueloba,Globoquadrina globo/a, Globorotalia scitula,Neogloboquadrina'acostaensis (sinist.).

Ciellcias da Terra fUNL), 15

ci. Bioz. c:u; CD

f- (]).. (])Vl III Ul~ Cacela0 ~ "E - VIZ ~ ~

.,~

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section c. Lithostratigraphy0 ~ :::J.,_

ex: ·c 0 <T'" Ec: Ci·Q 0I ·E c: osos "C.c::: VI

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.. .. .. .. .. .. .. .. ..1" m $.!:"::~::":~:"::'en

.. .. .. .. .. .. .. .. .... .. .. .. .. .. .. .. ..III 10 ........ .. .. .. .. .. .. ..QI .. .....................~...

Yellowish sandstone.:=!: .............................................................................................................. .. .. .. .. .. .. .. ..........................................................................

III.. .. .. .. .. .. .. .. ..

u.;:.c c:'Ill

0U-QI :;:c: IIIQI Eu .. .. .. .. .. .. .. .. .. ...0 .................................... Fine, yellowish-orange sandstone with 0

:=!: .. .. .. .. .. .. .. .. .. carbonate concretions. Scarce fossils . U-S ....................................... .................................... III

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t: ~ Fine yellowish-gray sandstones with abundant{!. Z

III foraminifera, bryozoa, bivalves, gastropods andQi fishes.... <ll UQI Ol IIIQ.

Z 0 5.7(+3.9-1.1)MaQ.:J () QI.. 'C Fine yellowish-grey sandstone.

::E ..N .c Conglomerates w~h abundant fossils: mostly

~CD ~ large-sized molluscs, cirripeds.

Triassic

Fig. 2 - Cacela section: chronostratigraphic framework; correlation with bioevents from the Guadaiquivir Basinand I7Srl'6Srages.

Cacela 2 and Fabrica 2 age is between that ofthe events1 and 2 ofthe Guadalquivir Basin (respectively 7,512 and7,35Ma astronomic ages; Sierro et al., 2001).

Isotopic ages

"Srl'"Sr age ofa bivalve mollusc gave 5,7 (+3,9 -1,1)Ma. This age seems too young in comparison withbiostratigraphic data. Furthermore the margin of error isvery wide. This could suggest that the calibration curve isnot well established for this span of time.

QuelfesLocation

Samples were collected at some outcrops near Quelfes(Fig.3). GPS coordinates: N 37° 03' 18,3"; W 7° 49' 52,6".

Fig. 3 - Quelfes (Geological Map ofAlgarve, 1: I 00 000;Manuppella, 1992): the arrow points out to the location of the

studied outcrops.

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Geological setting

Sands and marly silts, often with bioturbationstructures, are exposed. A glauconite-rich level wasrecognised in the upper part. Basal beds are conglomeraticlimestones with siliceous pebbles and limestone boulders.

These deposits belong to the Cacela Formation.Neogloboquadrina acostaensis (sinisI. predominance),Globigerinoides extremus and some keeled Globorotalia(dexl. predominance) point out to the Upper TortonilUl.Sierro (in Antunes et al., 1990) stressed the possibilitythat the upper levels could be Messinian in age. Incomparison with Guadalquivir Basin, the age ofconcerneddeposits is sometime between events 2 and 3 (Sierro, 1985;Sierro et al., 1993).

Planktonic Foraminifera and biostratigraphic analysis

Samples Q2 and Q4 are the richest in planktonicforaminifers, while Q3 is the less rich (Fig.4). Thefollowing species were identified:

QI - Dentoglobigerina altispira, Globigerinoidesbulloideus, Globigerilloides cOlIglobatus, Globigerilloidesextremus, Neogloboquadrina humerosa, Orbulinauniversa.

Q2 - Dentoglobigerilla altispira, Globigerina bUlloides,Globigerina praecalida, Globigerinoides bulloideus,Globigerinoides conglobatus, Globigerilloides extremus,Globigerinoides seigliei, Neogloboquadrilla humerosa,Orbulilla sLl/uralis, Orbulilla ulliversa.

Q3 - Globigerilloides bulloideus, Globigerilloidesseigliei, Orbulilla sutumlis, Orbulilla ulliversa.

Q4 - Globigerilla bulloides, Globigerina concilla,Globigerinoides bulloideus, Globigerinoides elollgatus,Globigerilloides extremus, Globigerilloides seigliei,Globorotalia gr. menardii (dext.), Globorolaliamiotumida, Neogloboquadrina acosta ens is,Neogloboquadrilla humerosa, Orbulina universa.

Q5 - Globigerina bulloides, Globigerilla druryi,Globigerinoides bulloideus, Globigerinoides trilobus,Globorotalia conomiozea, Orbulina sllfuralis, Orbulillauniversa.

Biostratigraphic interpretation is shown (Fig. 4). In thelower part, N. Illimerosa e G conglobalus indicate theUpper Tortonian (probably N 17). In the upper part Gmiolumida and G. conomiozea point out to theMessinian (N 17). Globorotalia gr. menardii (dext.)is still present in the Q4 sample. This suggests thatthe concerned levels may be correlated to the event 3 ofthe Guadalquivir Basin, marked by the replacementof the G mellardii group by the G mioillmida group(Sierro et al., 1993).

202

Isotopic ages

Shells of molluscs from different levels were dated"Sr/"Sr: 5,3 (+4,3-0,7) Ma, 5,2 (+4,4-1,1) Ma, 5,2(+4,4-0,6) Ma. These ages seem too much youngerthan the expected age 7 (+1-1) Ma as established byBerggren et al. (1995) for N17. Let us recall that KlArglauconite age for two samples from Luz de Tavira(correlative of Quelfes) is 6,88±O,4 Ma and 7,03±0,4 Ma(Antunes et al., 1986). Age of event 3 is 7,24 Ma (Sierroet aI., 200 I).

Mem MonizLocation

Outcrops at Mem Moniz (Fig. 5) that border thenational road EN395.

Geological setting

Withish sediments with some teleostean fish remnants(bones and scales) and high abundance of microfossils(sponge skeletal elements, diatoms, calcareousnannofossils, planktonic foraminifera and ostracods). Thelower contact is an angular unconformity over Cretaceousunits (Romariz et al., 1979; Antunes et aI., 1981). Thestratigraphic position has been object of controversy.Sediments like these are unknown elsewhere in Portugal.In Spain, similar sediments are known to overlie theGuadalquivir olistostrome.

Prates (ill Romariz et al., 1979) ascribed the MemMoniz deposits to the Upper Burdigalian or LowerLanghian (N8 or N9) on planktonic foraminifera.

According to Bizon (ill Antunes et al., 1981),Glabarotalia acostaellsis (sinistral) points out to aTortonian, N 16 age.

Sierro (ill Antunes et al., 1990) stressed that the pre­dominance of Globigerina bulloides in association withNeogloboqlladrina acostaellsis, Globigerilloidesbulloideus, Globigerilla drlllyi, Globigerina quinqllelobaand Globigerillita gill/inata indicates at least N 16.

These sediments were ascribed to the MiddleSerravallian (CN5a) on calcareous nannoplankton(Cach"o, 1995).

"Sr/"Sr age on planktic foraminifera was obtained:12.5 (+0.7-1.7) Ma, Upper to Middle Serravallian (Antunesel aI., 1997).

Planktonic Foraminifera and biostratigraphic analysis

Four samples were studied. The planktonicforaminifera frequence decreases from the lower to themiddle part of the succession. They are more abundantagain in the upper part. Foraminifera are well preservedbut are smaller than usual.

The following species were identified: Globigerinaanguslillmbilicata, Globigerilla bulloides, GlobigerillacOllcilla, Globigerina drlllyi, Globigerina falconensis,

Ciellcias cia Terra (UNLi. 15

>- Planktonic ForaminiferaIc... >- c:« :I: :§. ;ill: Q. .!!l .,C:l « :g OJ :2-I- a:

., '" ~~ e !g« CJ ., .. .. cll: i= 8 E ~ E c: ~ ~ Cii ID

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., .Q '"« .c;: .\1> E E to

'"til C/) .. OJ ill 1< .2 E87Sr/86Sr

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., 0 c'" Q)I- '" '" C, .Q c: ~Q) ....;

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~ ~ E 8 ~ > ..CD section 1Il .. §c: E 0 Q ::> ·0 ~ Jg ~ ages ::s Q) OJ-'" 2" 0- CT'0 <Il ll: 0 ~ .~ .'l! .'l! j - 0 g:E C/) m .0 e~

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Q .\1> .\1> .8 (Ma) .!!18' .0 .0 ::s ~~ ~

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7.24 Ma

1·1-- 5.2 (+4.4-0.6)

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~

z«z

---

--- Q3· '- .:-:-;-: ::::~ :

· .· . . . . .· .· . . . . .· . . . . . .

~HHHjd~~~

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..-- Q2

· .· .· .· . . . .. ..---4wl+ -Ql

z«zol­ll:ol-

ll:Wc...c...:::l

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o f:<~.>f":><

Fig. 4 - Chronostratigraphic framework of the Quelfes section; occurrence of planktonic markers. correlation withbioevents from the Guadalquivir Basin. and "SrJ'6Sr ages.

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Ciencias do Terra (UNLJ, 15

MemMonizsponpoIiths:

sampledouIaops

Isotopic ages

The "SrJ'6Sr planktonic foraminifera shell age isseemingly too old - 12.5 (+0.7-1.7) Ma (Middle to UpperSerravallian). This age is not supported by biostratigraphicinfonnation and should be rejected.

Conclusions

I) Planktonic foraminifera and especially the coiling typeof Globorotalia mellardii group and the occurrence ofGloborotalia miotumida at Quelfes allow correlation withthe I to 3 bio-events in the Guadalquivir Basin (Sierro et

al., (993).

2) Cacela and Fabrica may thus be dated from the timespan between Guadalquivir basin's events 1 and 2 (7.512and 7.35 Ma; Sierro etal. 2001).

Fig. 5 - Spongoliths at Mem Moniz (Geological Map ofAlgarve, I: 100 000; Manuppclla, (992).

Globigerinella aequilateralis, Globigerinoides bulloideus,Globoquadrilla baroemoellellsis, Neogloboquadrinaacostaellsis (sinist), Neogloboquadrina humerosa(sinist).

N. acostaellsis and N. humerosa point out to uppennostN 16 or even N 17. This age should be older than 6 Ma(Upper Messinian), as the N. acostaellsis coiling directionchanged to dextral coiling. The absence of carinateGloborotalia do not allow a better biostratigraphicaccuracy.

The presence of Globigerilla druryi could beproblematic. The last appearance datum is generallyregarded as Upper Serravallian (N14), but Sierro (1984)has shown that it still occurs in the Guadalquivir Basin inthe Upper Miocene and Lower Pliocene.

This assemblage undoubtedly is Upper Miocene inage. Hence the Mem Moniz sediments are of the someage as the Cacela Formation. The correlation betweenQuelfes (lower part) and Cacela is most likely. Thischronology is near the same as that of similar deposits inperi-mediterranean area, i.e. Spain, Italy and Argelia.

References

3) At Quelfes, Globorotalia miotumida and G menardii(dext.) may be correlated to event 3 (7.24 Ma).

4) In the upper part of the outcrop, GloborotaliacOllomiozea suggests a Messinian age (FAD 7.12 Ma;Berggren et aI., (995).

5) Glauconite KiAr ages from Luz de Tavira sediments,that can be correlated to those ofQuelfes, yielded 6.88±OAMa and 7.03±OA Ma; these ages fit well with theplanktonic biostratigraphy.

6) Mem Moniz spongoliths can be ascribed to the UpperMiocene, Tortonian, upper part ofN 16 or N 17.

7) There are important differences between thebiostratigraphic infonnation and the S.../S'" ages whoseerror margins are quite broad.

Acknowledgements

I am grateful to Prof. M. Telles Antunes for helpfulreview of this paper. I thank Prof. Joao Pais for aid andcooperation on field work and SEM photography.

Antunes, M. T.; Bizon, G; Nascimento, A. & Pais, J. (1981) - Nouvelles donnees sur la datation des depots miocenes de I'Algarve(Portugal), et I'evolution geologique regionale. Ciencias do Terra (UNL), Usboa, 6: 153-168.

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Antunes, M. T.; Civis, J.; Dabrio, C. J.; Sierro, F. J.; Gonzalez-Delgado, J.A.; Flores, J. A.; Pais,J. & Valle, M. (1990) - EI Neogeno delAlgarve (portugal) y de la cuenea del Guadalquivir (Espaiia). Actas de Paleolllologia. Universidad de Salamanca, 68: 65-73.

Antunes, M. T.; Elderfield, H.; Legoinha, P., & Pais, J. (1997) - The Neogene ofAlgarve in Field Trip GI/ide - Excl/rsion Z / TheGI/adalql/ivir Basin and Algarve (Spain. Portl/gal). II Congress R.C.A.N.S., Spain.

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Civis, J.; Pais, J.; Gonz!lez.Delgado, J. A. & lA:goinha, P. (2000) - Sintesis paleontol6gica del Tononiense superior de Cacela(Algarve, Portugal). I Congresso lberico de Paleon/ologia/XVIJornadas de la Sociedad Espanola de Paleontologia - Li"ro deResumos: 10-11.

Dollfus, G.; Cotter, J. C. B. & Gomes, J. P. (1903.1904)- Mollusques tertiairesdu Portugal. Planches de Cephalopodes, Gasttropodeset Pelecypodes laissCcs par F.A. Pereira da Costa accompagnCc:s d'une explication sommaire et d'une esquisse geologique.Mem. Comm. Serv. Geol. Portugal, Lisboa: 48 p.

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Pais, l; lA:goinha, P.; Elderfield, H.; Sousa, L. & Estevens, M. (2000) - The Neogene of Algarve. Ciillcias da Terra ruNL),Lisboa,14: 277-288.

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Ribeiro, A.; Antunes, M. T.; Ferreira, M. P.; Rocha, R.; Soares, A. F.; Zbyszewski, G; Moitinbo de Almeida, F.; Carvalho, D. &Monteiro, J. H. (1979) - Introduction ill la Geologie generale du Portugal. Serv. Geel. de Portugal, Lisboa: 114 p.

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Sierro, F. J. (1985)- The replacement ofthe Globorotalia menardii group by the Globorotalia miotumida group: an aid to recognizingthe Tononian-Messinian boundary in the Mediterranean and the adjacent Atlantic. Marine Micropaleontology, 9: 525-535.

Sierro, F. J.; Flores, J. A.; Civis, l; Gonzalez-Delgado, 1. A. & Franc~, a (1993)· Late Miocene globorotaliid event-stratigraphyand biogeography in the NE·A1lantic and Mediterranean. Marine Micropaleontology, 21: 143-168.

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Ciincias do T~rra (UNL), IS

Plate I

Planktonic foraminifera. Scale, 100 !!m.

Fig. I - Globorotalia miotumida Jenkins, 1960; Quelfes section.

Fig. 2 - Globorotalia gr. menardii (parker, Jones & Brady, 1865); Quelfes section.

Fig. 3, 6 - Neogloboquadrina humerosa (Takayanagi & Saito, 1962) ; Mem Moniz section.

Fig. 4, 5 - Neogloboquadrina acostaensis (Blow, 1959); Mem Moniz section.

Fig. 7, 8 - Globorotalia (G) conomiozea Kennett, 1966; Quelfes section.

Fig. 9, 10 - Globigerinoides extremus Bolli, 1965; Quelfes section.

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PLATE I

207