Gruta da figueira brava (Arrabida): Geological setting

Separata do Tomo XXXVIII das Memories da Academia das Ciencias de Lisboa (Classe de Ciencias)The Arrabida Mountain Range is the best example in Portugal of alpine movements. During Miocene times the Arrabida chain acquired the present structural set up: overthrusting accidents striking ENE-WSW and N-S or NNE-SSW sinistral lateral ramps. The main tectonic phases occurred about 17 Ma and somewhat less than 16 Ma. The Miocene deposits, mainly biocalcarenites, are middle Burdigalian and Langhian in age. During the Pleistocene the sea erosion cut several terrasse levels. Scattered remnants of conglomerates corresponding to the 12-15 and to 5-8 meters marine terrasses are ascribed to the last interglacial and to the beginning of the Wiirm glaciation (= 100000 years, Tyrrhenian II and III). The 5-8 meters terrasse, which is of particular interest, was deposited in a narrow marine erosion platform; the corresponding deposits tend to fill the entry of the caves excavated in the sea cliffs during the Upper Pleistocene such as Lapa de. St" Margarida and Figueira Brava Cave. These holes, protected by overhanging parts of the cliffs as a sort of ceiling, were good shelters forman. With the advance of the Wiirm glaciation the sea level was progressively going down. About 30000 years ago, the 5-8 meters platform and the caves dug in the cliffs were elevated as related to an extensive coastal plain. The sea level was ca. 60 meters below the present level (Miskovski, 1987). The human communities found in these territories an excellent hunting ground. The Santa Margarida and Figueira Brava caves were thus natural shelters. A large number of remnants of their occupation are preserved such as shells, animal bones, a few Neanderthal remnants as well as lithic and bone implements. 14C (and U series) dating indicate an age about 30000 years for level 2 where archaeologic remnants were exploited

Bio and magnetostratigraphy of two Lower Miocene sections, Tagus basin (Portugal)

The magnetostratigraphy of two sections in early Miocene marine deposits of the Tagus Basin is studied. Thermal demagnetization was used to isolate the primary component of magnetization for 45 samples from the Foz da Fonte section, and for 74 others from Trafaria section. The succession of the polarity zones found in these sections is tentatively correlated with the geomagnetic polarity time scale (GPTS) on the basis of the biostratigraphic data yielded by planktic Foraminifera. The planktic zones and magnetic polarities recognized in these sections can be adequately correlated with the part of the GPTS [table calibrated by BERGGRENET al. (1985)] corresponding to the Anomalies 6 and 5E (Foz da Fonte) and 5D (Trafaria). This correlations suggests ages between 19,35 and 18,14 Ma for Foz da Fonte section, and 17,90 to 16,98 Ma for Trafaria

A stratigraphic framework for the Miocene from the lower Tagus Basin (Lisbon, Setúbal Península, Portugal) Depositional sequences, biostratigraphy and isotopic ages

Rev. Soc. Geol. España, 12(1), ano 1999Lithostratigraphy, main biostratigraphic events (first and last ocurrence), 87Sr/86Sr as well as KlAr isotopic ages, are presented for the Lower Tagus basin (LTB) Miocene (Lisboa and Peninsula de Setubal regions). Eight depositional sequences (DS) delimited by regional disconformities related with transgressive surfaces are defined. The main features of the Depositional Sequences are as follows: Depositional sequence (DS) A (Aquitanian). Biostratigraphy (Biost.): Small mammals from Km 10: MN2 (MN3?); ostracoda: Aquitanian fauna. Isotopic age (IA): glauconites (KlAr) values between 19 and 24 Ma. 87Sr/86Sr ages from the glauconite levels: 22.3 (+0.4-0.7) Ma. Lower and upper boundaries not well established. DS BO (Lower Burdigalian). Biost.: foraminifera - Fa Globigerinoides altiaperturus (NS); mammals - Fa Brachyodus intermedius (MN3); ostracoda - La Hemicyprideis helvetica and Pokomyella lusitanica at the LTB. IA (87Sr/86Sr): Foz da Fonte -19.S (±0.2) Ma, Penedo Sui (base) - 20.0(±0.4)Ma; Almada (top) - 18.3 (+0.-0.2) Ma. Mammal sites: Av. do Uruguai - 21.S( +O.S- 0.3) Ma; Univ. Cat6lica - 20.S (+0.3-0.2) Ma. DS Bl (Middle Burdigalian). Biost.: foraminifera - Catapsydrax unicavus and Globigerinoides altiaperturus (N6); mammals - Fa Gomphotherium, La of Brachyodus (MN4); ostracoda -La Ruggieria (R.) micheliniana, Cnestocythere truncata, Pokomiella minor and Triebelina raripila. fA (87Sr/86Sr) Foz da Fonte - 19.7 (+0.3-0.2) to 18.S (+0.2-0.S) Ma. DS B2 (Upper Burdigalian). Biost.: mammals -Fa Bunolistriodon and Megacricetodon primitivus (MN4); ostracoda - La Miocyprideisfortisensis. IA (87Sr/86Sr): Penedo Norte 17.7 (+0.7-0.S) Ma; 17.8 (+0.7- O.S) Ma. DS Ll (Upper Burdigalian and Langhian). Biost.: foraminifera - Fa Praeorbulina (N8); mammals - Fa (upper part) Hispanotherium and Megacricetodon collongensis, La M. primitivus (MNS); ostracoda - Fa Pterigocythereis (P.) siveteri and Loxoconcha (L.) ducasseae. IA (87Sr/86Sr): Penedo Norte 17.3 (+0.6-0.5) Ma. DS SI (Upper Langhian and Serravallian). Biost.: foraminiferaFa Orbulina suturalis, O. universa and Globorotalia cf. menardii; ostracoda -Fa Aurila (u.) oblonga, Ruggieria (R.) nuda, R. tetraptera tetraptera, Nomurocythereis seminulum, Pterygocythereis (P.) jonesi y Olinfalunia costata. IA (87Sr/86Sr): Chelas 14.7 (+ 1.S-0.S) Ma, Almada (Brielas ) (lower part) - 14.0 (±0.4 ) Ma, Penedo (upper part) 12.S (+ 1.0-2.0) Ma. DS S2? (Upper Serravallian) is poorly characterized due to strong condensation (Foz da Fonte-Rib. Lage) and poor outcrops (Lisbon region). Biost.: foraminifera - La Globigerinoides subquadratus (top). DS Tl (Tortonian). Biost.: foraminifera - La Globorotalia mayeri (lower part), Fa Neogloboquadrina acostaensis (upper part); ostracoda - Fa Aurila (U.) zbyszewskii, Celtia quadridentada and Cyheretta (C.) simplex. IA: Penedo Norte: KlAr- 1O.9S±0.2S Ma; 87Sr/86Sr - 11.3 (+ 1.7-2.8) Ma; Almada (Foz de Rego) - 8.3 (+ 1.9-3.3) Ma; Fonte da Telha S.2 (+3.1-1.2) Ma

Análise polinica de argilas de Lagoa Negra

Palynological analysis of black shales from Lagoa Negra (Cantanhede) shows the presence of Cathaya and Keteleeria, Myrica and Engelhardtia being scarce. Comparison with other localities suggest an Upper Pliocene or Lower Pleistocene age for this association

High resolution stratigraphy and miocene facies correlation in Lisbon and Setúbal Peninsula (Lower Tagus basin, Portugal)

Correlation between facies associations (marine, estuarine and distal fluviatile environments) and disconformities, observed between Foz da Fonte (SW of Setúbal Peninsula) and Santa Iria da Azóia (NE of Lisbon) are presented. The precise definition of the marine-continental facies relationships improved very much the chronology of the depositional sequence boundaries. Tectonic and eustatic controls are discussed on the basis of subsidence rates variation

The Neogene of Algarve (Portugal)

A synthesis about the Neogene and Quaternary of Algarve (Southern Portugal) is presented. New isotopic 87Sr/86Sr ages as well as biostratigraphic data about the Miocene deposits allow to present a new stratigraphic frame for the previously characterized units. The Lagos-Portimão Formation corresponds to deposits of temperate carbonate platform sedimentological type, developed during a long time span (Lower Burdigalian to Upper Serravallian). A major change in sedimentation conditions (carbonate to siliciclastic environments) occurred in the Lower Tortonian with the deposition of yellowish sands. Spongoliths rich in microfossils are represented in Algarve inland. Their age is not well established; calcareous nannofossils indicate the CN5a zone (Upper Serravallian) while foraminifera point out at least Nl6 zone (Lower Tortonian). In the Upper Tortonian, the sedimentation is widespread in Eastern Algarve, related with the Guadalquivir Basin infill. The deposits begin with detrital limestones, locally very rich in Heterostegina, passing to fossiliferous conglomerates and siltstones (Cacela Formation). Coarse-grained conglomerates at Galvana (Faro) pose some age problems. K/Ar age on glauconite indicates 6.72±0.17 Ma. However, glauconites may be reworked from older deposits (Cacela Formation). The Galvana Conglomerate could be related to Pliocene deposits are not well characterized. Olhos de Água sands, with a thin marine intercalation rich in marine vertebrates (fishes, a crocodile, cetaceans, sirenians), may be Upper Pliocene; however, the vertebrates point out to a Serravallian to Tortonian age. 87Sr/86Sr ages on oysters from above the level with vertebrates point out to 3.0(+2.5-1.0) Ma. Similar sand deposits occur at Morgadinho (Luz de Tavira). These sands are overlain by marls, lignite clays, lacustrine limestones and a silty calcareous crust. A small mammals association indicate an age span between Upper Pliocene and Lower Middle Pleistocene (MN17-MN20). A Biharian mammal fauna (Lower Pleistocene) was collected at Algoz in similar deposits. In the present state of knowledge, Morgadinho and Algoz deposits may be correlative

Areias de Vale de Santarém. Estratigrafia e Palinologia

The palynologic study of several boreholes for lignite prospection at the "Vale de Santarém sands" is presented. Height spores and 18 pollen forms have been identified. The quantitative and qualitative results are shown in table 2. Four palynologic associations (A - D) corresponding to climatic changes have been characterized. Correlations are established with the plant associations of Rio Maior Basin. Correlation between the boreholes allow a better understanding of the small, Vale de Santarém basin infilling

The Cristo Rei section (Lower Miocene). Distal fluviatile environments in a marine series, plants, vertebrates and other evidence, age

The section at Cristo Rei shows sandy beds with intercalated clayey lenses (IVb division from the Lisbon Miocene series) that correspond to a major regression event dated from between ca. 17.6 and 17 Ma. They also correspond to a distal position (relatively to the typical fluviatile facies in Lisbon), nearer the basin's axis. Geologic data and paleontological analysis (plant fossils, fishes, crocodilians, land mammals) allow the reconstruction of environments that were represented in the concerned area: estuary with channels and ox-bows; upstream, areas occupied by brackish waters where Gryphaea griphoides banks developped; still farther upstream, freshwaters sided by humid forests and low mountain subtropical forests under warm temperate and rainy conditions, as well as not far away, seasonally dry environments (low density tree or shrub cover, or steppe)

Património paleontológico do Concelho de Almada

Pela sua grande riqueza paleontológica, sobretudo no que diz respeito a fósseis miocénicos,as arribas litorais e ribeirinhas do Concelho de Almada merecem ser incluídas no Património Paleontológico Português, de acordo com critérios científicos, pedagógicos e culturais, entre outros. Enumeram-se razões justificativas dessa inclusão, para algumas jazidas seleccionadas, consideradas mais representativas da totalidade do conjunto

Litostratigrafia do Cenozóico de Portuga

In Portugal mainland the Cenozoic record occurs largely in several basins. Even in the same basin, the sedimentary record shows meaningful lateral facies and thickness changes. However, the main sedimentary ruptures and overall lithologic characteristics of the infillings stades are quite similar in the same basins, as a result of the geodinamic evolution of Iberia and the Cainozoic times eustatic and climate changes. A stratigraphic framework is proposed in order to allow a less complex use of the lithostratigraphic units as referred in the geological maps and literature. Some topics for future research are suggested