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INTEGRATED THERMOCHRONOLOGY AND ORGANIC MATURATION STUDIES IN THE SOUTH PORTUGUESE ZONE AND ALGARVE BASIN SOUTH PORTUGAL

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Dados de amostragem de Geologia do Pré-Quaternário
Publication . Fernandes, Paulo; Rodrigues, Bruno; Matos, Vasco
Bases de dados de amostras recolhidas entre 2009 e 2011 no âmbito de diversos projetos e teses de doutoramento (http://hdl.handle.net/10400.1/6821; http://hdl.handle.net/10400.1/5748; etc.) do CIMA, Universidade do Algarve. Inclui a localização geográfica, as idades das amostras e as técnicas laboratoriais utilizadas, entre outros dados. A base de dados está construída em Access.
Geochemical signatures in detrital tourmalines as indicators for sediment provenance: the Baixo Alentejo Flysch Group, South Portuguese Zone
Publication . Rodrigues, B.; Dias, Patrícia; Jorge, R. C. G. S.; Fernandes, Paulo
Microprobe analyses were made to infer the source of detrital tourmalines from the Mid to Late Carboniferous turbiditic deposits of the Baixo Alentejo Flysch Group (BAFG) of the South Portuguese Zone.
The transition from Pangea amalgamation to fragmentation: Constraints from detrital zircon geochronology on West Iberia paleogeography and sediment sources
Publication . Dinis, Pedro A.; Fernandes, Paulo; Jorge, Raul C. G. S.; Rodrigues, Bruno; Chew, David M.; Tassinari, Colombo G.
Detrital zircon U-Pb geochronology data from late Carboniferous to Triassic clastic sedimentary rocks in SW Iberia were used to investigate the regional paleogeography during the transition from Pangea amalgamation to breakup. The major U-Pb zircon age peaks are middle Devonian to Carboniferous (similar to 390-300 Ma), Cambrian Ordovician (similar to 530-440 Ma), Cryogenian-Ediacaran (similar to 750-540 Ma), Stenian-Tonian (similar to 1.2-0.9 Ga) and Paleoproterozoic (similar to 2.3-1.8 Ga). Rapid exhumation of Variscan crystalline rocks at the contact between the South Portuguese zone and Ossa Morena Zone, explains the abundance of late Paleozoic ages in the upper Carboniferous-lower Permian continental successions. The U-Pb zircon data constrain the maximum depositional age of the Santa Susana Basin to c. 304 Ma and the Viar Basin to c. 297 Ma. The Triassic sequences, despite being c. 100 Ma younger than the Variscan tectonothermal events, contain low proportions of late Paleozoic zircon. The major peaks in all zircon spectra closely resemble those found in the adjacent basement rocks, indicating small source areas, mainly located near the rift shoulders. Longer travelled fluvial systems are postulated for the eastern portions of the Algarve Basin, which was closer to the westward advancing Tethys Ocean than the rift basins of West Iberia. Sequences that contain significant proportions of similar to 1.2-0.9 Ga zircon are probably recycled from post-collisional Carboniferous-Permian continental deposits that were more extensive than those found today. (C) 2017 Elsevier B.V. All rights reserved.
An integrated thermochronology, organic maturation and provenance study in the South Portuguese Zone and Algarve Basin (South Portugal)
Publication . Rodrigues, Bruno; Fernandes, Paulo; Chew, David; Jorge, Raul
Organic maturation levels (vitrinite reflection) were combined with low-temperature thermochronometers (apatite fission track analysis and (U-Th)/He in apatite) to construct temperature-time paths for the Upper Palaeozoic rocks of the South Portuguese Zone and the Mesozoic rocks of the Algarve Basin. Detrital zircon ages were also studied in order to constrain the sedimentary source regions and basin fill history of the Baixo Alentejo Flysch Group from South Portuguese Zone and the Upper Triassic sandstones from the Algarve Basin. The maximum temperature attained in the South Portuguese Zone was 326 ºC and occurred at 320 Ma. All the samples from the South Portuguese Zone have been totally reset after deposition and yield apatite fission track ages ranging from the Cretaceous (111 to 59.9 Ma) to the Upper Jurassic (157.9 Ma). The fission track ages from the Upper Triassic sandstone did not reset after de deposition, however, the intrusion of the Monchique Alkaline Complex (MAC) and related swarm of dikes had local influence upon organic maturation. Inverse modelling on apatite samples from the MAC indicate that it cooled very fast from initial magmatic temperatures to around 70ºC. The rock sample studied stayed at a constant temperature close to the top of the apatite partial annealing zone from 68.7 Ma to 5 Ma. Since 5 Ma until the present the MAC underwent an exhumation of ca. 300 m/Ma. The U-Pb detrital zircon and apatite ages from the Mértola and Mira formations suggest sedimentary provenance areas from a detrital intrabasinal source (South Portuguese Zone) and from areas associated with the magmatic arc related rocks located at the southern border of the Ossa Morena Zone. The U-Pb detrital zircon ages obtained for the Brejeira Formation suggest a source area related to the Avalonian/Meguma terranes and also from recycled clastic sediments associated to the South Portuguese Domain. The ages from the Algarve Basin Upper Triassic sandstones suggest that they are derived from multiple sources terranes with Permian zircons ages more abundant in the samples located in the eastern part of the basin.

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Funding agency

Fundação para a Ciência e a Tecnologia

Funding programme

Funding Award Number

SFRH/BD/62213/2009

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