THE NEOGENE OF ALGARVEC')

EXCURSION 2

(PORTUGUESE PART)

THE NEOGENE OF ALGARVEC')

M . Telles ANTUNESC"" ), H. ELDERFIELD(h.,), P. LEGOINHA (") &

J.

PAIS("')

Collaboration of L. SOUSA & M. ESTEVENS

(') • Work supported by the "Praxis XXI 212. I /CTAlI 06J94" Project (JN ICT, Portugal).

C) -Academia das Ci!ncias de Lisboa.

(') - Centra de Estudos Geo l6gicos (JNICT). Faculdade de Cicncias e Tecno logia. Qu imu da Torre, P-2825 Monte de Ca pari ca, Port ugal.

(") - Department of Earth Sciences, Uni versity o f Cambridge, Downing Street. Cambridge C 0 2 3EQ , UK. 1- mta@ mai l.fcl.unl .pt; 2 • helOl@esc.cam .ac.uk; 3 - pal @mail.fct.unl.pl;4 - jjp@maiJ.fcl.unl. pt

ALGARVE (Portugal)

Geog raphical situation of the localities to be visited (o )

Atlantic Ocean

Fig . 1 - Itinerary and geographical situation of localities to be vis ited.

FOREWORD

The first studies about the Cenozoic of Algarve dealt only with some fossi l localities and deposits (PEREIRA DA C OSTA, 1866; DOLLFUS et al., 1903-1904; BOURCART & ZBYSZEWSKJ, 1940; C HAVAN, 1940; ZBYSZEWSKJ, 1948; 1950).

Paleobiologia da Universidade Nova de Lisboa", begun the su-atigraphic study of the Neogenc of Algarve. Since then, some synthetic interpretations have been published (ANTUNES et al.,

1981; ANTUNES et al., 1990; ANTUNES et al., 1992). Meanwhile, new developments mainly concerning " Sr/" Sr isotopic dating have been achieved. A revision is under way taking into account all the available data, and specially isotopic ages, micropaleontology and sequence stratigraphy analysis.

At tbe present status of knowledge, the so far characterized Neogene units are of Miocene age and mostly marine. They range in age from Lower to Uppermost Miocene. There are also lithological differences. Olhos de Agua sands could be ascribed to Pliocene based on 87 Sr/86Sr dating, but this remains to be confirmed. Those of Morgadinho (ANT'JNF " ~ et aL. ,

1986c) are probably (at least in part) Pliocene in age.

Only brief remarks aJ'e presented on the extensive, more or less rubefied, sand covers, their age being poorly known (Faro-Quarteira Formation). This Formation comprises Quaternary sands, some of which are quite modern as at Guia, where a fauna of small Vertebrata was described (ANTUNES et al.

1989). Lithic implements do not help in clarifying its age (CARDOSO et aL. 1985).

There are better dated Qnaternary deposits such as terraces or karst infillings. Among the terraces, there is an important mammal locality at Algoz (earlier than Giinz glaciation , Biharian) (ANTUNES et al., 1986a) and some other sites with lithic industries. Two karst sites near Goldra yielded Vertebrata and implements (AN TUNES et al. , 1986b; P6VOAS et al., 1995).

The Neogene and Quaternary units so far recognized in Algarve are shown in the Fig. 4, and will be discussed by age order from the earliest one.

PERElRA DE SOUSA (1917) has admitted the presence of miocene igneous rocks in Algarve although they were not found later. In 1971 a small outcrop of a basanite was observed enclosed by Miocene biocalcarenites showing clear evidence of low grade thermal effects along the contact with the igneous dike. This rock represents the most recent manifestation of volcanic activity in Portugal (PINTO COELHO & BRAVO, 1983). However, in Southern Spain, cenozoic volcanic activity is well known since Langhian-Serravallian till Qltaternary.

-Tectonic structures concerning the meso 7.oic and cenozoic depo ~ its or the Algarve basin allow us to recogni ze the following Alpine orogeny events: Jurassic (Upper Triassic at least) - Lower Crctaccous N-S disten sion; E-W di stension dUling Lower to Upper Cretaceous; N-S compression during the setting-up of the Monchique syenite dome at the setting-uppermost Cretaceous ; Paleogene compression (only locally? - at the Albufeira salt domc); Lower and Middle Miocene N-S and B-W distension; Tortonian N-S compression; post-Messinian E-W compression; N-S compression during the Quaternary.

The NE-SW fractures affecting the Paleozoic basement are related with the first distension phases. The mesozoic N-S distension is the main cause of the two E-W flexures so far recognized. The tectonic inversion did occur after the setting up of the Monchique syenite. If the Lower Cretaceous-Lower Miocene Albufeira' s unconformity is a local effect of halokinesi s, then the true tectonic inversion of the Algarve basin only took place in the Lower to Middle Tortonian.

These events correlate well with those known in southern Spain and Morocco ( KULLBERG et al., 1992).

N ,

t

\

,

"

;,/\

~

....,.-•

'''''

Fig. 2 - Main tectonic accidents of Atgarve ( R IBEIRO et al. . 1990.

modified).

LAGOS· PORTIMAO FORMATION

This Formation is the most evident miocene unit in western Algarve. It makes up a sizable portion of the costal sea cliffs, and is of considerable scenic interest. It overlies carboniferous, jurassic,

39-cretaceous and possibly paleogene units. In some places a very clear angular unconformity can be observed , whereas stratigraph ical hi atuses or paraconformities may be recognized elsewhere.

The Lagos-POItimao Formation comprises yellow or pink massi ve and very fossil i ferous hiocalcarenites. In the lower part, Mollusks are plentiful. As for the upper part, there are many sea-urchin s, Bryozoa, pectinids and fishes. Planklic Foraminifera from the npper levels include Globigerinoides Irilobus, G. subquadratus, G. bisphericus, Globoquadrina haroemoenensis and cf. Praeorbulina transitoriu, which point out to N7 -N8(?) (Upper Burdigalian to Langhian) (ANTUNES, et af. 1981). The presence of Orbulina in biocalcarenites at a Faro borehole indicate that the SelTavallian is also represented there (ANTUNES et al., 1984; ANTUNES & PAIS, 1992),

"Sr/" Sr isotopic age indicate 19.5(+O.2.0.3)Ma (Lower BurdigaJian) at Arrifao (lower deposits, overlying the Cretaceous) and 11.3( +O.9-1.3)Ma (Upper Serravallian) at Praia da Gale (upper part) (Fig. 2).

Nannoplankton (Reticulofenestra pseudoumbilicus and

Calcidiscus premacintyrei) from the upper part of the unit (Albardeira, Lagos), also points out to a Sen'avallian age (NN6 or CN5a) (CACHAO, 1995).

On the other h:md, this unit is older than the K-At· dated (1O.I ±O.25 Ma) glauconite fine sands from Praia da Gale, as well as the Sands tones from Praia da Rocha, 87 Sr/86Sr dated 1O.7( +O.8-1.2)Ma.

MEM MONIZ SPONGOLITHS

Overlying the Cretaceous in the inner Algarve there is an outcrop of white spongoliths virtually devoid of macrofossils but with microfauna. T hese deposits have been described by ROMARIZ et af. (I 980b). They are unknown elsewhere in Portugal, but closely similar ones are widespread around the Mediterranean. They were accumulated in a trough related to tectonic events in upwelling conditions.

The rock is essentially composed of sponge spicules. It also contains Foraminifera, calcareous nannoplankLOn, Diatoms and Fish remnants.

-PlankLic Furarninifera indicate the Gluburuialia acostael1sis, N 16 Blow zone, Lower Tortonian (ANTUNES et aI. ,

1981; 1990; 1992). Foraminifera 87Srf86Sr indicates an isotopic age of 12.S(+0.7-1.7)Ma. The calcareous nannoplankton snggests the CNSa Bukry zone (Upper Senavallian) (CACHAO, 1995). Hence, the accurate age of these deposits is still open to discussion, albeit between rather na.now lim its.

SANDSTONES WITH SAND WAVES AND FINE SANDS

This unit is separated thro ugh a disconfonnity from the underlying carbonate beds from the Lagos-Portimao Formation. It marks a major change from carbonated to siliciciastic sedimentation. Th is change can be correlated with the beggining of the eustatic 2d order cycle TB3 (HAQ et al. , 1987).

The lowermost level at Praia da Rocha is a conglomerate with phosphatic clasts. Ostrea shells give a " Sr/" Sr isotopic age of 10.7( +O.R-J .2)Ma (Lower Tortonian).

Fine sands at Hotel Auramar beach, 9.5(+ 1.0-0.5)Ma, a.re interpreted as con'elative of this unit.

At Praia da Gale glauconite-rich fine sands allowed K-Ar dating (10.1 ±0.2SMa, Lower Tor[onian) (ANTUNES et al. , 1984). BOSK! et aI., (1995) obtained (also glauconite K-Ar) 8,15±0,29 and 7,54±O,27 Ma.

An age around 10 Ma for the sands tones with sand waves and fine sands is most probable.

Fig. 3 - Schematic cross-secti on showing the Upper Miocene E-W flexu re of the Algibre river by compressive tectonics trending N-S at Mem Moniz (KULLBERG et al., 1992).

SSE

~----...-- ...

--Palaeozo,c

... : ...

CACELA FORMATION

The uppermost Miocene deposits are well represented in eastern Algarve but they also outcrop in western Algarve near Lagos.

At Carnpina de Faro and Quelfes there me olltcrops of fossi liferous carbonate rocks rich in detrital quartz ; in some places these deposits grade into microconglomerates (Faro limestones with quartz pebbles and conglomerates) . At the upper part of the Auramar Hotel beach there is a first level of conglomerates with oysters that give a " Sr/8O_{Sr age of}

8.3(+2.2-3.3)Ma. This is in agreement with the biostratigraphic datation of the lower levels of Cacela river (NI6-N 17) which begin by a conglomerate overlying the Tri ass ic. The conglomera is interpreted here

as

correlative of the lowermost deposits of Cacela Formation , which compri se mainly yell ow, orange, or green glauconite silts.

The lower conglomerates at Cacela and the directly overlying silts yielded the richest and best preserved Miocene mollusk faun a in Portugal. This fauna was described by PERElRA DA COSTA (1866, 1867) and by DOLLFUS et al. (1903, 1904), and revised by CHAVAN (1940) and BouRCART & ZBYSZEWSKl (1940). There are also some Vertebrata; Foraminifera (the plankti c ones indicate N 16- 17 of Blow, Upper Tortonian); and upper Miocene Ostracoda, some forms probably attaining the Messinian (ANTUNES et aI. , 1981 ; 1990; 1992). Calcareous nannoplankton indicates the same Upper Tortonian age (CN9a Bukry zone, CACHAO, 1995). " Sr/uSr isotopic data point out to 5.7(+3.9-l.l)Ma.

The middle, also silty, levels of Cacela Formation are rich in glauconite that give ages of 6.90±0.18Ma (Galvana) , 6Jj~ ±U.5 (Quelfes), 7.03±0.4Ma (near Luz de Tavira), uppermost Tortonian (ANTUNES et aI., 1984, 1986d; 1990; 1992). " Sr/S6_{Sr age from the Quelfes silts are 5.3(+4.3-0.7);}

5.2( +4.4-1.l) and 5.2( +4.4-0.6)Ma.

The upper deposits of the Cacela Formation overlie a ferruginous hardground. They correspond to confined marine env ironments, fossi ls being scarce and poorly preserved . The age may be Messinian to Lower Pliocene.

-GALVANA CONGLOMERATE

The strati graphic position of the spectacular Galvana conglomerate, with striate blocks exccc.ding one meter, and interbedded glauconiferous silts (ANTUNES et al. , 1984), is nut

dcar. Glauconiferous silts indicate a K-Ar age of 6.72±0.17 Ma; however, the glauconite can be reworked from the Campina de Faro silts (ANTUNES et al., 1984; 1990; 1992).

Conglomerates are related to strong tectonic instability and were probably formed in the sub-marine slopes associated to the Algarve southern Ilexure. The K-Ar age is compatible with that of the olistostrome of the Guadalquivir basin, although this is far away and corresponds to South-North sediment mass movements (however, in Algarve, the Galvana conglomerate has been generated by North-South sediment movements).

In a borehole at Campina de Faro, conglomerate s overlying glauconitic silts may correspond to the Galvana conglomerate. If so, it is younger than the silts and its age could be Messinian or Pliocene.

OLHOS DE AGUA SANDS

In the area near Olhos de Agua, there is an outcrop of a thick sand series between the Sands tones with sand waves and the Faro-Quarteira Formation.

The Olhos de Agua section have been described by

ROMARIZ et at. (1980a). The succession starts by alternating

facies suggests (as well as the feldspathic sands) the e , ~istence of a large liver whose mouth was qu ite close by. The presence of large crocodilians as TOInistom.a cf. lusitanica corroborates these views and indicates sub-tropieal conditions (ANTUNES, 1979; ANTUNES et al. , J 981; 1990, 1992).

Above these levels there are sands rich in oysters and scarce pectillids - including the rare Plliiollum (Lissoch /amys)

excisul11. Mullusks indicate estuarine, even brackish environments.

Vertebrata are compatible with a pust-Langhian age; they are certainly pre-Pliocene and they may correspond to the Serravallian or to the Tortoni an . The mollusks are not chronologically characteristic. However, Paliollul11

(Lissochlamys) excisum is known both in Upper Miocene and

Pliocene (DEMARCQ, 1979) (it is common in Upper Pliocene in western Portugal). " Sr/86_{Sr age obtained from oysters give} 3.0(+2.5-1.0). However this value has to be taken cautiously since it correspods to a brackish environment, with broad elTors

MORGADINHO AND ALGOZ DEPOSITS

This unit comprises thick sandy de posits in association (towards the top) with marls, lign ite clays, lacustrine limestone and a silty calcareous crust. This unit is poorly exposed in outcrop, hence most observations have been carried on during the opening of water ~e ll s .

At Morgadinho and Luz de Tavira these sands overlie the Cacela Formation and are overlain by the Faro-Quarteira sands, as at Algoz (where the substractum is not known) .

At Morgadinho, the lignite clays yielded a few small mammal s, fish, gastropods, freshwater Ostracoda, poll ens and spores (ANTUNES et a!., 1986C). The mammalian fauna indicates an age span between the Upper Pliocene and the lower Middle Pleistocene, MN 17 to MN 20 mammal units .

In the present state of know ledge, Morgadinho and Algoz deposits seem to be cOlTelative. The Algoz mammalian fa una (including Eucladoceros and Hippopotamus) is rather accurately dated from about I Ma, Biharian (Lower Pleistocene) (AI\'TUNES

et af., 1986a) .

FARO - QUARTEIRA FORMATION

These sands make up the most extensive coverage of the whole of Algarve and lie over earlier units . They consist of

44

mostly rubefied middle to fine grained sands. Lithic industries made up from quartz pebbles, quartzites and graywackes were collected. Some specimens with a beller defined typology seem lO indicate the Mousterian; that corresponds to the Riss-WOrm interglacial and/or to the first part of the WOrm glaciation.

In the upper part, an association of small mammals and Amphibians has been collected (ANTUNES et aI. , 1989). These indicate temporary springtime puddles. Although age has not yet been accuralely determined, these vertebrates must be quite modern and probably Holocene.

CHESTER & JAMES (1995) point out to a late Pleistocene date, and to the end of sedimentation between 35 000 and 40 000 BP.

TERRACES, CALCAREOUS TUFFS AND KARST BRECCIAS

The study of these deposits remains is far from complete. Some terraces (approximately at 15 meters) yielded in situ

middle Paleolithic industries (CARDOSO el aI., 1985).

Well developped tuffaceous limestone at Loule and at Estoi yielded a few pul monate gastropods.

Some karst infillings are known. At Goldra, a mam malian fauna was found in a breccia, consisting mostly of remains of human scrap along with small manunals. Quite atypical lithic industries are compatible with typologies since middle Paleol ithic to the Epipa1eolithic. The microfauna suggests a Riss-Wiirm age or one of the first Wiirrn interstadials (ANTUNES et al ., 1986e).

A borehole in the holocene infilling of the karstic depression of Algueirao de Goldra show several levels with small vertebrates (P6VOAS el al., 1995).

CONSOLIDATED DUNES, SAND DUNES AND

ALLUVIONS

At Praia da Gale, fixed dunes are known in a narrow stri p of land along the coastli ne, among drift sands and present-day beaches . Drift sands are better developped near Montenegro and Faro, and between Arma<;:ao de Pera and Albufeira.

Extensive areas are covered by alluvial deposits at Ria Formosa, Vila Real de Santo Ant6nio, Penina, etc. These are related to barrier islands, the most important being Ria Formosa.

45-STOPl

PRAIA DO CANAVIAL

On the coast West of Lagos, Miocene beds overlie the Lower Cretaceous. There is a slight angular unconforrnity. At the top of the Cretaceous there is a hard ground marked by a ferruginous cmst covered surface. Coastal cl i ffs, about 40-45 meters high, expose a succession of yellowish biocalcarenites. The lowermost Miocene levels are very rich in mollusk casts and (mainly pectinid) shells. Somewhat higher up, there are layers particularly rich in Gastropoda.

At about the middle part of this section, fine-grained carbonate levels are particularly rich in Bryozoa and Heterosteginids.

Uppermost levels become harder; fossils, including some large oysters, are scant.

The whole succession has been much affected by karst phenomena.

81Sr/86Sr from oysters and/or pectinid shell contents indicate ages of 17.5(±0.7)Ma, l6 .3(+0.5-0.3)Ma and 14.3(±0.5)Ma (Burdigalian to Lower Serravallian).

Legend

~ Biocalcareniles Ph Phosphatic llOdulas <ii:> Ostreids M Balanids

ITIJ

Sandslonas G Glauconite ~ Other bivalves _~ Echinids

C'::d

Conglomerates - - Disconformity

_"!\

8 1)'0zoans

"'

Gastropods

46-Praia do Canavial section

m Note: carslflcatlon affects th e whole section, from top to bottom,

~ including the cretaceous basement.

~

35 ~ ~

~

1 I~ I~ 1 ~ 1

I~ Compact biocalcarenite rich in largo size peclinirls

I ~I 1

~ ~

30

I~ 1

"

~

.!'!

<i I~ 1

> I~

~

ffi 1 ~

C/l _~.l.

.L

25 _'Oo'

m ,

"

~ocalcarenite with bivalves (pectlnlds and oslreidsj and echinids

m

u

..

(lass abundant than the bivalves, except for the last meter where

0 _{echinids predominate)}

:E

m

;; _ 14.3(±O.5)Ma

"

20

:E

~ .

-.

~

1'<) ~

~ ~I fr

15 _

1 {!? 1 I1!lI

Bioca\carenite, more compact than the pre vious levels, with

"

~ I"

~I

bryozoans, bivalves (pectinids and oslreids), gastropods and

"

fragments of echinids_ Reddish ferruginous concretions

m

1!l

E

'"

~ "I _ 1 6.3(+O.5-0.3)Ma

"

m _{<5 1}

" I

.J

10 111!l 1' .J.

~

'"

J.

_,

"" I

~

--

- -

,.

B4ocalcarenite, very rich in bryozoans in the fi rst meter. Pectinids and

ostreids become more abundant upwards. Biolurbation.

"

"

5

m

"

•

u _.!'! , _{_17.5(±O.7)Ma}

0

:E m Cl

(;;

'E

~ => ~ _{Fine biocalcarenile with fragments 01 moHusks, mainly bivalves:}

0

.J ID • ~

..,..

pectlnids and ostreids .

o _

~

0 ~

~ Paraconformlty • hardgro und

Cretac.

Fig . 5 - Praia do Canavial section (by L. Sousa and M. Estevens).

-STOP 2

PRAIA DA ROCHA

At Praia da Rocha there are some highly carsified outcrops of thc Lagos-Poltimao Formation. Fossils are scarcer than in the lower leve ls at Praia do Canavial. There is important N-S and E-W normal faulting. Upper beds give a " SrI" Sr age of 12.2(+1.2-1.3)Ma and II.S(+O.8-0.S)Ma (Upper Serravallian).

This Formation ends by an erosion su rface, and is overlain by laminated sandstones, poor in fossils. The lower level is a conglomerate with fragments of phosphate crusts and glauconite. Oyster shells give a 87Sr/S6Sr age of 1O.7(+O.8-1.2)Ma.

-Praia da Rocha section

m

25

~ _{Reddish biocalcarenite}

C

~ C

u _m

0 _'2

~ =~

~ _E Fine yellow sandstone, with thin greyish, carbonated crossed beds

ID (; ₌ I1 contai ns very scarce fragments of pectinids and echinids

Q. l-Q.

::>

J=

~

~ Conglomorate with phosphatic nodulgs and glaumnite

20 +-10.7(+O.8-1 .2)Ma

c Biocalcarenite with echinids and large sized pectinids

.~

..

_{~ "l ~-~}

Fine yellow sandstone, with fossils similar to those of the second

> level but less frequent

~

Q;

-

_{+-11.5(+O.8-0.5)Ma}

(J) ~

~

-

Fine yel lowish-orange sandstone with intercalated ferruQinous beds

-

It contains pectinids and scattered sma ll Elchlnld fragments

15 - _~

+-12.2(+1.2-1.3)Ma

~

-~

C

~

u

0

~

-~

'5

-

, Biocalcaren ite with echinids, pectinids, balanids and abundant large

"C

~ ostreid s

10

-Yellowish sandstone

-

Compact greyish biocalcarenite, with more fossil s than the previous

level (balanids and pectinids more abundant; large echinids), but in

--

. ~ lesser numbers than at Ihe basal level. There are yel lowish

~.

-

sandstone intercalations

C

.~ _M

~ "'\

-" Fine yellowish -orange, carbonate-cemented sandstone, with

C> _{scattered and scarce fossils (pectinid and echinid fragments, balanids}

c

'1\ _ M~

m

5 - and bryozoans)

...J

-

-, .::-~

~

..

-C C

-

Compact, yellowish-orange biocalcare nite with abundant fossi ls :

~ _.~

-u

et.

~~ large pectinids and echinids (the latter reaching 15 cm in diameter) ,

0

..

ostreids, vertebrate bones, corals, gastropods, ete It also shows

~ .2'

-"C f-L-- bioturbations and some lerruginized bi valve shells

ID _~ ~

~ III 0

~ . ~

...J

STOP 3

MEMMONIZ

At Mem Moniz there is an unique (as far as known in Portugal) outcrop of white spongolithes.

These beds are nearly devoid of ll1011usks. They yield ~()me fish remnants along with large numbers of microfossils, including sponge skeletal elements, diatoms, calcareous nannofossils (among others Helicosphera carte ri, Recticulofenestra pseudoumbilicus, Coccolithus pelagicus, Cyclococcolithus macintyrei, Sphenolithus abies, DiscoLithina multipora) benthic (Nonion boueanum, Ammonia, Buliminid~,

Bolivinids, Uvigerinids) and planktic Foraminifera, and Ostracoda (Aurila zbyszewskii, Nonurocythereis seminulum, Carinocythereis galilea) (ANTUNES et al., 1981 ; 1990; 1992).

Planktic foraminifers (Globigerina bulloides, G.

qu£nqueloba, G. druryi, G. glutinata, Neogloboquadrina acostaensis, Globigerinoides bulloideus) date these beds from N 16 at least (Lower Tortonian) (ANTUNES et al., 1981; 1990; 1992). Calcareous nannoplancton indicate zone CN5a of Bukry (upper Serravallian) (CACHAo, 1995). " Sr/" Sr age on planktic foraminifera is 12.5(+O.7-1.7)Ma (Upper Serravallian).

Benthic Foraminifera point out to shallow environments rich in organic matter and to low oxygen contents.

Such facies are quite alike to some Upper Miocene ones in Southern Spain overlying the olistostrome of the Guadalquivir.

-STOP 4

CACELA

Upper Miocene is well represented in eastern Algarve through a very interesting unit, the Cacela Formation. The lower beds fr0111 this Fonnation are extremely rich in well preserved fossils.

One of the most sllitable outcrops is along the banks of Cacela river, where Upper Miocene directly overl ies triassic sands tones.

The whole unit begins with a conglomerate vcry rich in mollusks . Next beds are fine sands and silts, yellow ish in coulour, also rich in fossils, the test being generally preserved:

G/ycymeris, Ca rdium , Megaca rdita , Panopea , Pelecyora, Callista, Turritellids, Naticids, and Conus are common.

Foraminifera and Ostracoda [Aurila (Cymbaurila) diecci, A. gr. semilunata, Ca rinocythereis galilea , Nonurocythereis seminulum] are plentiful. Planktic foraminifers are suitable for dating: Globigerina bulloides, Globorotalia scitula, G.

pseudomiocenica, G. menardii, G. humerosa, G. altispira and

Neogloboquadrina acostaensis indicate NI6-17 zones of Blow (Upper Tortonian-Lower Messinian). The presence of

Spiroplectamina carinata (a benthic foraminifer) excludes a Messinian age for the lower levels of this Formation (ANTuNEs

et al., 1981 ;1990; 1992).

Calcareous nannoplacton from the lower beds include

Discoaster berggrenii, Helicosphaera stalis, Minylitha convalis, Triquetrorhabdulus rugosus (?) that also indicate the same Upper Tortonian age (CN9a zone of Bukry) (CACHAo, 1995).

Somewhat higher levels (at Fabrica) yielded calcareous nannoplancton (Cocco lithus pelagicus , Reliculofenestra pseudoumbilica, R. minuta, R. minulula, R. haqii, Dicryococcites antarcticus, Sphenolithus abies, S. morifonnis. Helicosphaera carteri, Eudiscoaster surculus, E. icarus, E. intercolaris, E. pseudovariabilis, Triquetrorhabdulus rugosus) and planktic Foraminifera [Globige rina bulloideus, G. apertura. G. drury i, G.

quinqueloba, GloiJige rinoides extremus, G. seigliei, G.

quadrilobatus, Globigerinita glutinata, Orbulina lIniversa. O. suturalis, Globoquadrina globosa, Globorotalio (Hirslttello)

-scitulll, Neogloboquadrina acostaens is sin.] that may be ascribed to Late TOIionian-Messinian. Benlhic Foraminifera (Bo livinids, Buliminids) indicate oxigen-poor environments (ANTUNES et al., 1990).

These beds are overlain by silty or fine sand beds with scarce, poorly preserved fossils including some plant remnants, in stratigraphical continuity. Upper beds may be Messinian in age.

Cacela section

m a e c : :

10

5

Yellowish sandstone.

Fine yellowish-orange sandstollB with levels of carbonated concrections. Fossils are scarce _

Fine yellowish-gray sandstones, with abundant fossils: Foraminifera. bryozoa, mollusks (blvalves and gastropods), fishes

~~~~~*- 5 .7(+3.9-1 .1)Ma

--f Fine yallowish-g ray sandstone

Conglomerate with abundanllossils: mollusks (olten

large-sized), cirripeds.

Trlasslc sandstones

Fig. 7 - Cacela river section (PAIS, 1982).

52-12.5(+0.7-1.7)

N16

Sagres Zavial Canavial Rocha Galé Castelo Arrifão

Mem Moniz

Albardeira Auramar Olhos de Água Faro QuelfesMorgadinhoCacela

W

_E

Ma 20 19 18 17 16 15 14 13 12 11 10

T

ort

oni

an

M I O C E N E S E R I E S S T A G E S 9 8 7 6 5 4

M

es

si

ni

an

Z

anc

le

an

3 2 P ia ce nz ia n G el as ia n P L E IS T O C E N E

S

erra

va

ll

ia

n

L O W E R M ID D L E C al abri an P L IO C E N E

L

anghi

an

B

urdi

ga

li

an

U P P E R N5 N6 N7 N8 N9 N10 N12 N13 N14 N15 N16 N17 N18 N19 M2 M3 M4 M5 M6 M7 M9 M11 M12 M13 Foraminifera zones B er ggre en, 1995 2.1 2.2 2.3 2.4 2.5 2.6 3.1

Berggrenet al.₁₉₉₅

Conglomerates

G G

17.5 (±0.7) 16,2 (±0.5)

Detrital limestones and sandstones

Marls Sands

Feldspathic sands

Glauconite

Fine-grained sandstones and siltstones

17.5(±0.7) 87_Sr 86_{Sr isotopic age (Ma)}

K/Ar isotopic age (Ma)

16.3 (+0.5-0.3) 14.3(±0.5) 5.5(+4.1-0.7) 12.2(+1.2-1.3) 19.5 (+0.2-0.3) 19.2(+0.2-0.4) 9.5 (+1.0-0.5) 11.5(+0.8-0.5) 11.3(+0.9-1.3) 14.2(+0.6-0.7) 5.3 (+4.3-0.7) 5.2 (+4.4-1.1) 5.2 (+4.4-0.6)

?

M14 PL2 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 16 17 18 19 20

A L G A R V E

(South Portugal)

10.1(±0.25) MN17-20 \ G 12.5 (+0.8-0.7) 12.0(±1.3) 10.1(±0.25) G

MN20 _{Mammal unit}

Lignite L agos -P or ti mão F or mati on C ac el a F or mati on Faro-Quarteira Sands O lhos de Á gua sa nds Microconglomerates with miocene vertebrates PL1 PL5 PL6 PT1 a b a b a b a b b a b a 15.5(+0.8-0.3) 5.7(+3.9-1.1) G Ph Ph Ph Phosphates G 10.7(+0.8-1.2) G S pongol it h m arl s

Marls with vertebrates

8.3 (+2.2-3.3) 8.15(±0.29 7.54(±0.27) G G G Spongoliths M or ga di nho de pos it s

Deposits with uncertain stratigraphic position 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 PL3 C am p in a d e F ar o b o re h o le (J . K el le r, A p ri l 8 4 ) G O r bul ina

Sand dunes, terraces, karstic breccias, alluvia

Observed lithic contact

?

Faro limestones with quartz pebbles and

conglomerates G G ? G G A ura m ar si lt st one s and congl om era te s G 6.72(±0.17) 6.90(±0.18) S ands tone s w it h sa nd w ave s and fi ne sa nds

C N 9 a

C N 5 a C N 5 a

CN1 CN2 CN3 CN4 C N 5 C N 7 a b a b CN8 C N 9 a b c d CN10 CN11 CN12 CN13 CN14 B low , 1969 C al car eou s n an n op lan k ton B ukry , 1973; 1975 N16-17 Galvana conglomerate 6.88(±0.5) 7.03(±0.4) Ma hardground

?

C N 9 a N16-17 ? N7 N8? G T JB 2 T JB 3 Foraminifera zone

Calcareous nannoplancton zone

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