Conglomerates - Fundación General de la Universidad de Salamanca

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 (JNICT, Portugal).
C) - Academia das Ci!ncias de Lisboa.
(') - Centra de Estudos Geol6gicos (JNICT). Faculdade de Cicncias e Tecnologia. Quimu da Torre,
P-2825 Monte de Capari 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 • [email protected] .ac.uk; 3 - pal @mail.fct.unl.pl;4 - [email protected]. 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).
In 1979 M.T. Antunes and J. Pais, whose work concerned
the Research line n° 1 of the former "Centro de Estratigrafia e
- 37-
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.
- 38 -
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 settingup of the Monchique syenite dome at the 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-urchins, 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/86 Sr 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. These 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.
- 40 -
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 through 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.
SSE
Fig. 3 - Schematic cross-section 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).
- 41 -
~----.............-- .......-Palaeozo,c
BaserThil<l!
...... : ...
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/8OSr age of 8.3(+2.23.3)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 comprise 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(+3.9l.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/S6Sr 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.
- 42 -
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
et at. (1980a). The succession starts by alternating
sandy and pelitic layers (Ilaser facies) overlain by cross-bedded
brownish sands and followed by feldspathic, Iluviatile white
sands. Locally, the brownish sands outcrop in water-eroded
gullies and are covered by red peJites. The latter are overlain
either by white sands or by the Faro-Quarteira Formation
(Quaternary). Over these white flu viati le sands there are beach
sands and conglomerates with abraded remnants of aquatic
Vertebrata (fish vertebrae and teeth, cetacean bones, Sirenian
teeth and bones). The majority of the fishes are marine, often
very large in size (Carcharocles megalodon, Isurus hastalis,
Odontasp;s cf. taurus, Hem;pr;st;s serra, Carcharh;nus sp.). The
degree of abrasion of the vertebrate remnants suggests that they
were rolled by waves in shallow, sandy bottoms at a beach. The
Sirenians (Metaxyther;ul1l medium) point out to shallow seashore
environments, rich in aquatic vegetation (algae, vascular plants).
The presence of fish like Lates, also frequent in fresh water
ROMARIZ
- 43 -
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 deposits 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 ~ells .
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 -
I
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,
BRECCIAS
CALCAREOUS TUFFS AND
KARST
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 pulmonate 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
ALLUVIONS
DUNES,
SAND
DUNES
AND
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
ITIJ Sandslonas
C'::d Conglomerates
Ph
G
Phosphatic llOdulas
Glauconite
<ii:> Ostreids
~
- - Disconformity
- 46-
"!\
Other bivalves
8 1)'0zoans
M
Balanids
~
Echinids
"'
Gastropods
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~
I ~I
~
30
~
1
I~
"
~
.!'!
<i
>
1
I~
I~
~
1
ffi
~
.L
~.l.
C/l
25
'Oo'
,
m
..
"um
0
:E
~ocalcarenite
with bivalves (pectlnlds and oslreidsj and echinids
(lass abundant than the bivalves, except for the last meter where
echinids predominate)
m
;;
Compact biocalcarenite rich in largo size peclinirls
1
_
14.3(±O.5)Ma
20
":E
~.
-.
~
1'<)
15 _
~I fr
~
1 {!? 1 I1!lI
" ~ I"
~I
"m
E
.J
10
"I
<5 1 " I
111!l 1' .J.
~
,
J.
""m
--
"
u
.!'!
:E
m
0
(;;
~
0
.J
Bioca\carenite, more compact than the previous levels, with
bryozoans, bivalves (pectinids and oslreids), gastropods and
fragments of echinids_ Reddish ferruginous concretions
1!l
~
"'"m
--
~
5
'"
_1 6.3(+O.5-0.3)Ma
"" I
~
,.
•
,
B4ocalcarenite, very rich in bryozoans in the fi rst meter. Pectinids and
ostreids become more abundant upwards. Biolurbation.
_17.5(±O.7)Ma
Cl
'E=>
•
o _
Cretac.
..,..
~
ID
~
~
0
Fine biocalcarenile with fragments 01 moHusks, mainly bivalves:
pectlnids and ostreids.
~
~
Paraconformlty • hardgro und
Fig . 5 - Praia do Canavial section (by L. Sousa and M. Estevens).
- 47 -
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.
- 48 -
Praia da Rocha section
m
25
~
Reddish biocalcarenite
C
~
u
0
C
m
~
'2
ID
Q.
(;
Q.
~ =~
=
E
l-
Fine yellow sandstone, with thin greyish, carbonated crossed beds
I1 contai ns very scarce fragments of pectinids and echinids
::>
J=
~ ~ +- 10.7(+O.8-1 .2)Ma
Conglomorate with phosphatic nodulgs and glaumnite
20
Biocalcarenite with echinids and large sized pectinids
..
c
.~
~"l~-~
>
- -
~
Q;
~
(J)
+-
~
15 -
+-
-
~
C
11.5(+O.8-0.5)Ma
Fine yel lowish-orange sandstone with intercalated ferruQinous beds
It contains pectinids and scattered small Elchlnld fragments
~
~
Fine yellow sandstone, with fossils similar to those of the second
level but less frequent
12.2(+1.2-1.3)Ma
~
u
-
0
~
-
~
'5
"C
~
10
,
-
-- - .~
~.
C
.~
M
-"
C>
c
m
...J
~
C
~
u
0
~
ID
~
0
...J
- -
.
C
.~
.2'
"C
~
III
5 -
Biocalcaren ite with echinids, pectinids, balanids and abundant large
ostreid s
"'\
~
'1\ _M~
Yellowish sandstone
Compact greyish biocalcarenite, with more fossils 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
Fine yellowish -orange, carbonate-cemented sandstone, with
scattered and scarce fossils (pectinid and echinid fragments, balanids
and bryozoans)
,.::-~
.- -et.
-
~~
f-L--
Compact, yellowish-orange biocalcare nite with abundant fossi ls :
large pectinids and echinids (the latter reaching 15 cm in diameter) ,
ostreids, vertebrate bones, corals, gastropods, ete It also shows
bioturbations and some lerruginized bi valve shells
~
~
.~
Fig. 6 - Praia da Rocha section (by L. Sousa and M. Estevens).
- 49 -
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.
- 50 -
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, Cardium , Megaca rdita , Panopea, Pelecyora,
Callista, Turritellids, Naticids, and Conus are common.
Foraminifera and Ostracoda [Aurila (Cymbaurila) diecci,
A. gr. semilunata, Carinocythereis 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 [Globigerina bulloideus, G. apertura. G. drury i, G.
quinqueloba, GloiJigerinoides extremus, G. seigliei, G.
quadrilobatus, Globigerinita glutinata, Orbulina lIniversa. O.
suturalis, Globoquadrina globosa, Globorotalio (Hirslttello)
- 51 -
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
aec::
10
Yellowish sandstone.
Fine yellowish-orange sandstollB with levels of
carbonated concrections. Fossils are scarce _
5
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-
Eustatic 2nd /3rd order cycles
Haq et al. 1987
Bukry, 1973; 1975
Blow, 1969
Berggreen, 1995
Sagres
Zavial
Canavial Albardeira
Ma
3.10
CN11
N19
3.5
6.72(±0.17)
5.5(+4.1-0.7)
b
G
7.54(±0.27)
G
8.15(±0.29
M13
CN7
M12
M11 N14
N13
b
M9
N12
a
Serravallian
10.1(±0.25)
G
N16
G
11.3(+0.9-1.3)
b
?
CN5a
2.6
12.0(±1.3)
12.2(+1.2-1.3)
12.5 (+0.8-0.7)
a
9
10
11
12
13
M7
N10
M6
14.6(+1.4-0.4)
14.3(±0.5)
2.4
N9
N8?
b
TJB2
Langhian
8
CN5a
14.2(+0.6-0.7)
N8
M5
M4 a
2.3
16,2 (±0.5)
16.3 (+0.5-0.3)
N7
N7
2.2
Burdigalian
14
15
16
17
CN3
M3
15.5(±0.4)
15.5(+0.8-0.3)
b
17
7
12.5(+0.7-1.7)
2.5
a
LOWER
9.5 (+1.0-0.5)
10.7(+0.8-1.2)
Ph
6
8.3 (+2.2-3.3)
Faro limestones with
quartz pebbles and
conglomerates
G
11.5(+0.8-0.5)
CN4
16
G
CN9a N16-17
5.7(+3.9-1.1)
Lagos-Portimão Formation
MIDDLE
M I O C E N E
a
N15
CN5
11
3.1
G
Spongolith marls
N16
6.88(±0.5)
GG
6.90(±0.18)
7.03(±0.4)
G
G
G
G
?
?
Sandstones with sand waves
and fine sands
Tortonian
CN8
b
15
G
G
Orbulina
UPPER
3.2
5.2 (+4.4-0.6)
5.2 (+4.4-1.1)
5.3 (+4.3-0.7)
G
Galvana conglomerate
3.3
5
hardground
Campina de Faro
glauconitic silts
c
N17
?
Auramar siltstones
and conglomerates
d
4
?
3.4
Cacela Formation
Messinian
M14
3
Campina de Faro borehole (J. Keller, April 84)
N18 CN10
Microconglomerates
with miocene
vertebrates
Olhos de Água
sands
3.6
PL1
a
Morgadinho deposits
\
TJB3
Zanclean
3.7
PL2
b
1
MN17-20
CN12
10
19
Morgadinho
Quelfes
Cacela
Faro
2
PL3
b
9
18
Olhos de Água
Faro-Quarteira Sands
a
14
Mem Moniz
Auramar
3.8
PL5
7
8
Arrifão
3.9
PL6
a
6
13
Galé Castelo
Marls with vertebrates
CN13
5
12
Rocha
E
PT1 a
CN9
Piacenzian Gelasian Calabrian
CN14
PLIOCENE
4
(South Portugal)
W
b
2
3
ALGARVE
Sand dunes, terraces, karstic breccias, alluvia
PLEISTOCENE
Ma
S TAG E S
SERIES
Foraminifera
zones
Calcareous nannoplankton
Berggren et al. 1995
17.5 (±0.7)
18
N6
CN2
2.1
19
19.2(+0.2-0.4)
19.5 (+0.2-0.3)
M2
N5 CN1
20
20
Detrital limestones and sandstones
Lignite
Ph
Sands
Spongoliths
G G
Feldspathic sands
Marls
Conglomerates
Fine-grained sandstones and siltstones
Ph
Phosphates
Glauconite
Deposits with uncertain
stratigraphic position
Observed lithic contact
MN20
N16-17
CN9a
17.5(±0.7)
10.1(±0.25)
Mammal unit
Foraminifera zone
Calcareous nannoplancton zone
87
Sr
86
Sr isotopic age (Ma)
K/Ar isotopic age (Ma)
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