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- The age of the first pulse of continental rifting associated with the breakup of Pangea in Southwest Iberia: new palynological evidencePublication . Vilas Boas, Margarida; Paterson, Niall W.; Pereira, Zélia; Fernandes, Paulo; Cirilli, SimonettaIn this work, we report the first palynological age for the base strata of the Silves Sandstones of the Silves Group in the Algarve Basin, located in Southern Portugal. The group is the oldest sedimentary unit of the Algarve Basin and was deposited unconformably over late Pennsylvanian turbidites of the Mira Formation, which were folded and faulted during the Variscan Orogeny. The Silves Group comprises a detrital red bed succession, representing the earliest phase of sedimentation associated with the initial rifting of Pangaea. Macrofossils are rare, occurring predominantly in the top layers of this group, and do not accurately constrain the age of the entire group's deposition. From an outcrop exposed in the central Algarve, a grey mudstone bed positioned 2.5 m above the Variscan unconformity plane yielded palynomorphs that date the beginning of sedimentation in this basin to the early Carnian age (Late Triassic). The moderately well preserved and low-diversity palynological association comprises Aulisporites astigmosus, Enzonalasporites densus, Ovalipollis pseudoalatus, Samaropollenites speciosus, Tulesporites briscoensis and Vallasporites ignacii, among others, and is indicative of an early Carnian age.
- New data on the palynology of the Triassic–Jurassic boundary of the Silves Group, Lusitanian Basin, PortugalPublication . Vilas Boas, Margarida; Pereira, Zélia; Cirilli, Simonetta; Duarte, Luís Vítor; Fernandes, PauloNew evidence is presented on the Triassic–Jurassic boundary in the northern Lusitanian Basin, Portugal, based onmiospore assemblages from a composite Upper Triassic to Lower Jurassic succession of the Silves Group. The lat-ter comprises, from base to top, the Conraria, Penela, Castelo Viegas and the Pereiros formations. Three informalpalynologicalzones havebeendocumented andcomparedwith coevalpalynozonesfromWestandSouth Europeprovidingnew biostratigraphic data to detail the age of the lower and upper formationsofthe SilvesGroup and toreview previous age attribution.A Norian, possibly earliest Rhaetian age, is documented for the Conraria Formation on the basis of a palynologicalassemblage referable to theClassopollis meyerianus–Granuloperculatipollis rudis(CG) zone. The Penela andCastelo Viegas formations did not allow a palynostratigraphic revision, due to the not promising lithology for pal-ynological studies. The Pereiros Formation is dated on the basis of microflora assemblages referable, from bottomto top, theIschyosporites variegatus–Kraeuselisporites reissingeri(IK) zone of late Rhaetian–earliest Hettangian ageandPinuspollenites minimus(Pm) zone of Hettangian age. The discontinuity between the underlying CasteloViegas Formation and the overlying Pereiros Formation did not allow to define the lower boundary of the IKpalynozone. The Triassic–Jurassic boundary lies in the lower part of Pereiros Formation within the IK zone. Themicroflora assemblages from the Lusitanian Basin show close affinity to those of eastern N America and westernTethys areas.