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- Middle-Upper Jurassic palynology of the Sagres region and the Carrapateira outlier: southern PortugalPublication . Borges, Marisa; Fernandes, Paulo; Pereira, Zélia; Riding, JimThe palynology of the Middle-Upper Jurassic fill of the Sagres region (Algarve Basin) and the Carrapateira outlier, southern Portugal was investigated. Samples were collected from Mareta beach, Cilheta beach and the Carrapateira outlier. Dinoflagellate cysts are confined to the Upper Bajocian to Upper Callovian sedimentary rocks exposed at Mareta and Cilheta beaches and the Lower Kimmeridgian strata of the Carrapateira outlier. The palynostratigraphical study of the Jurassic successions has yielded new biostratigraphical data based on dinoflagellate cysts and miospores. The results confirm, and in some cases refine, the existing macrofaunal age determinations of these successions.
- Callovian (Middle Jurassic) dinoflagellate cysts from the Algarve Basin, southern PortugalPublication . Borges, Marisa; Riding, James B.; Fernandes, Paulo; Matos, Vasco; Pereira, ZéliaThe palynology of three Callovian (Middle Jurassic) limestone-marl successions from the Algarve Basin in southern Portugal was studied. These localities are Baleeira Harbour, Mareta Beach and Telheiro Quarry; they provide a composite. succession, tied to ammonite zones, through the Lower, Middle and Upper Callovian from the western and eastern subbasins of the Algarve Basin. The three sections generally yielded relatively abundant marine and continental palynofloras. Diversity is low to moderate and the dinoflagellate cyst associations are dominated by Ctenidodinium spp., the Ellipsoidictyum/Valensiella group, Gonyaulacysta jurassica subsp. adecta, Korystocysta spp., Meiourogonyaulax spp., Pareodinia ceratophora, Sentusidinium spp., Surculosphaeridium? vestitum and Systematophora spp. Some intra-Callovian marker bioevents were recorded; these include the range bases of Ctenidodinium ornatum, Gonyaulacysta eisenackii, Korystocysta pachyderma, Mendicodinium groenlandicum, Rigaudella spp. and Surculosphaeridium? vestitum. The occurrences of Endoscrinium acroferum and Impletosphaeridium varispinosum in the Early to Middle Callovian of Mareta Beach and Telheiro Quarry are also characteristic of this interval. At Baleeira Harbour, the presence of Ctenidodinium continuum and Gonyaulacysta centriconnata in the Peltoceras athleta Zone confirms the Late Callovian age of this section. The successions studied were deposited in restricted infralittoral neritic marine environments which lack deep water circulation, and possibly represent restricted embayments. The relatively low diversity nature of the dinoflagellate cyst assemblages appears to be largely due to the highly enclosed nature of this depocentre. Many Callovian index dinoflagellate cyst taxa which are found in northwest Europe are absent in the Algarve Basin. These forms may have been intolerant of enclosed palaeoenvironments which have restricted or no deep circulation. The Callovian marine palynofloras from the Algarve Basin compare well to the few other published records from the Iberian Peninsula of this age. However they are significantly less diverse than coeval floras from elsewhere in the extensive Mid Latitude Callovian phytoprovince. Many typically Callovian dinoflagellate cysts are cosmopolitan, however some provincialism is clearly manifested. The Arctic and Austral Callovian phytoprovinces are characterised by key endemic taxa such as Paragonyaulacysta retiphragmata and Ternia balmei, which are not present in the Algarve Basin and are assumed to have been polar forms.
- Miocene dinoflagellate cyst assemblages: preliminary correlation between the Lower Tagus and Algarve Basins (Portugal)Publication . Castro, Lígia; Borges, Marisa; Pereira, Zélia; Fernandes, Paulo; Pais, JoãoBiostratigraphic studies of several sections and a borehole (Belverde) of the Lower Tagus Basin, based on Miocene dinoflagellate cyst assemblages, have allowed a detailed stratigraphic investigation to be conducted. Assemblages are very diverse and abundant and can be used as important biostratigraphic guides. Recently, a palynostratigraphic study based on dinoflagellate cysts was conducted in two offshore wells, Ruivo-1 and Corvina, located in the Algarve Basin (southern Portugal). The recovered dinoflagellate assemblages are less abundant and diverse than those obtained in the Lower Tagus Basin. New inferences are made regarding the correlation between the dinoflagellate cysts known from the Lower Tagus Basin with the assemblages recently recovered from the Algarve Basin. Species of selected dinoflagellate cyst assemblages recovered are similar in both basins. Continuing progress with these new palynological studies and biostratigraphic data will help to refine knowledge of and correlations between Portuguese Miocene deposits.
- Jurassic palynostratigraphy of the Algarve Basin and the Carrapateira Outlier, Southern PortugalPublication . Borges, Marisa; Riding, James B.; Fernandes, Paulo; Pereira, ZéliaThe Mesozoic Algarve Basin (AB) corresponds to the southernmost geological province of mainland Portugal. The Carrapateira Outlier (CO) is a small outcrop of Mesozoic rocks located 20 km north of the AB. In this study we investigated the palynology of the Jurassic (Upper Bajocian to Lower Kimmeridgian) of the AB and CO.
- d13Ccarbonate chemostratigraphy of the Carrapateira Outlier (Lower Kimmeridgian), Southern PortugalPublication . Borges, Marisa; Goodhue, R.; Fernandes, Paulo; Pereira, Zélia; Matos, Vasco; Rodrigues, B.The Carrapateira Outlier (CO) located 20 km north of Sagres is formed by Upper Triassic to Kimmeridgian sediments. The studied section is located at Três Angras bay and consists of approximately 50 m of limestones interbedded with marls, assigned to the Early Kimmeridgian based on corals, foraminifera and dinoflagellate cysts. The uppermost limestone beds are rich in macrofossils with well-preserved corals in life position. To compile 13C chemostratigraphy for this section, sixty five bulk carbonate samples were studied.
- Jurassic Palynostratigraphy of the Sagres Region (Algarve Basin) and the Carrapateira Outlier: preliminary resultsPublication . Borges, Marisa; Fernandes, Paulo; Pereira, Zélia; Riding, James B.The Algarve Basin (AB) corresponds to the southernmost geological province of mainland Portugal. More than 3000m of essentially marine sediments accumulated during Mesozoic-Cenozoic times in the AB.
- Palinoestratigrafia do Jurássico da região de Sagres (Bacia Algarvia) e da Carrapateira: resultados preliminariesPublication . Borges, Marisa; Fernandes, Paulo; Pereira, Zélia; Riding, JimA análise palinoestratigráfica das sucessões jurássicas da região de Sagres (Bacia Algarvia) e do afloramento Mesozóico da Carrapateira permitiu a obtenção de novos dados bioestratigráficos, com base em dinoflagelados e mioesporos. Os novos resultados confirmam, e em alguns casos refinam, as idades atribuídas a estas sucessões com base em macrofaunas.
- The Middle Jurassic palynology of the Sagres region, southern Portugal.Publication . Borges, Marisa; Fernandes, Paulo; Pereira, Zélia; Riding, JimThe Algarve Basin corresponds to the southernmost geological province of mainland Portugal. It has an E-W strike and is represented onshore from Cap São Vicente to the Guadiana River on the Portuguese-Spanish border. More than 3000 m of essentially marine sediments accumulated during Mesozoic-Cenozoic times in the Algarve Basin.
- New palynological data from the Ruivo-1 and Corvina wells, offshore Algarve Basin, Portugal: implications for future hydrocarbon explorationPublication . Borges, Marisa; Riding, James B.; Fernandes, Paulo; Pereira, Zélia; Matos, VascoThe Algarve Basin is an important Mesozoic sedimentary basin located in southern Portugal. Its onshore part consists largely of marine carbonate sediments with more than 2000 m in thickness. The basin extends offshore where its geology is recognized seismically and a few hydrocarbon exploration wells were drilled in the mid 70’s and early 80’s. The palynostratigraphical study of two of these wells, Ruivo- 1 and Corvina, has yielded new biostratigraphical data based on dinoflagellate cysts. The Ruivo-1 well has a total depth of 2100 m and drilled a thick Callovian succession between 1800 and 2030 m. The samples from this interval yielded abundant organic residues that comprise well-preserved palynomorphs together with plant fragments. The dinoflagellate cysts assemblage include Batiacasphaera spp., Ctenidodinium sp., Ctenidodinium sellwoodii group, Ellipsoidictyum gochtii, Ellipsoidictyum/Valensiella group, Gonyaulacysta jurassica subsp. adecta, Impletosphaeridium spp., Korystocysta gochtii, Meiourogonyaulax caytonensis group, Pareodinia ceratophora, Sentusidinium spp., Systematophora areolata, Systematophora penicillata, Systematophora spp. and Tubotuberella dangeardii. This association is indicative of the Middle-Late Callovian. However, the presence in this interval of Nannoceratopsis deflandrei subsp. deflandrei, a Toarcian-Aalenian marker, suggesting reworking. The Corvina well cored a 2700 m thick succession of Miocene to Upper Jurassic sediments. Samples collected between 1595 and 2680 m yielded relatively abundant organic residues dominated by dinoflagellate cysts. The pollen associations are of low diversity and include bisaccate pollen, Callialasporites dampieri, Callialasporites turbatus, Callialasporites spp., Classopollis classoides and Perinopollenites elatoides. The dinoflagellate cyst floras from these samples are indicative of the ?Early-Middle Oxfordian due principally to the occurrence of Ctenidodinium ornatum, Compositosphaeridium polonicum, Hystrichosphaerina orbifera, Endoscrinium luridum, Gonyaulacysta jurassica subsp. jurassica, Rigaudella aemula, Surculosphaeridium vestitum, Stephanelytron redcliffense, Systematophora spp. and Wanaea acollaris. The dinoflagellate cyst assemblages from the two wells are less diverse than typical Callovian-Oxfordian associations from further north in Europe. The results are also consistent with the onshore Algarve Basin and could be explained by the partially enclosed nature of the Algarve Basin during Jurassic times. This new biostratigraphical data will help to refine the time calibration of the available seismic lines and help in future hydrocarbon exploration work.
- Variação isotópicas d13C carbonatos na Sucessão da Baía de Três Angras: afloramento Mesozóico da Carrapateira (Kimeridgiano Inferior)Publication . Borges, Marisa; Goodhue, R.; Fernandes, Paulo; Pereira, Zélia; Matos, Vasco; Rodrigues, BrunoO afloramento Mesozóico da Carrapateira (AMC), localizado a 20 km a norte de Sagres é formado por sedimentos do Triássico Superior ao Kimmeridgiano. Para compilar os valores δ 13C para esta secção, sessenta e cinco amostras de carbonatos foram estudadas. Os valores δ 13C variam gradualmente ao longo da sucessão mostrando uma linha de base com uma tendência geral negativa. No entanto, a curva de δ 13C indica duas principais excursões negativas δ 13C, a primeira relacionada com a presença de um nível conglomerático, com um valor mínimo de -1,38 ‰ e uma segunda excursão com um valor mínimo de -3,10 ‰, imediatamente abaixo das camadas de calcário bioclástico do topo da sucessão. Em geral, a tendência negativa inicial está de acordo com a curva de δ 13C global, para o Kimeridgiano no Domínio Tetsiano, onde o AMC se insere. As duas excursões negativas são tendencialmente relacionadas com as perturbações no ciclo regional de carbono. Assim, ambos são interpretados como um resultado da entrada de grande quantidade de 12C para a bacia, como resultado de impulsos regressivos como sugerido pela análise sedimentológica, TOC e de palinofácies.