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- New Insights on the Upper Triassic Silves Group in Algarve Basin, Portugal: Palynological, paleophytogeography and paleoclimatology advancesPublication . Vilas Boas, Margarida; Pereira, Zélia; Cirilli, Simonetta; Fernandes, PauloABSTRACT: This paper presents the results of palynostratigraphic studies in the Silves Group in the Algarve Basin, Portugal. From bottom to top comprises the Silves Sandstones, the Silves Marl-Carbonate Evaporitic Complex, and the Volcano-Sedimentary Series. This study aims to detail the age of the Silves Group, bracketing the Triassic-Jurassic transition, using palynology. For this purpose, 250 samples were collected from 14 main sections. Previous results from a section above the Variscan unconformity, enabled to date the base of the Silves Sandstones and the onset of the Mesozoic sedimentary cycle in the Algarve Basin to lower Carnian. In this work, the top of the Silves Sandstones, containing Camerosporites secatus, Enzonalasporites vigens, Granuloperculatipollis rudis, Lagenella martinii, Patinasporites densus, Samaropollenites speciosus, and Vallasporites ignacii, is dated to the upper Carnian. The base of the Silves Marl-Carbonate Evaporitic Complex, consisting of Alisporites sp., Araucariacites australis, Classopollis meyerianus, Classopollis torosus, Paracirculina quadruplicis and Triadispora sp., indicates an upper Carnian age. The presence of Alisporites diaphanus, Araucariacites australis, Cerebropollenites macroverrucosus, Classopollis meyerianus, Classopollis torosus, Perinopollenites elatoides, Calamospora mesozoica, and Kraeuselisporites reissingeri allows to date the top of the Silves Marl-Carbonate Evaporitic Complex as upper Rhaetian-lower Hettangian. This study allows to date the Silves Group in the Algarve Basin from the lower Carnian to lower Hettangian (Triassic-Jurassic boundary) for the first time. The Carnian microflora provides new insights of the Onslow Microflora in the Western Tethys.
- The palynology of the Upper Triassic-Lower Jurassic in the Algarve and Lusitanian basins, PortugalPublication . Vilas Boas, Margarida; Cirilli, Simonetta; Pereira, Zélia; Duarte, Luis; Fernandes, PauloABSTRACT: High-resolution palynological analyses from the Algarve and Lusitanian basins (Portugal) provide a refined biostratigraphical framework and palaeoenvironmental reconstruction for the Late Triassic-Early Jurassic transition. In the Algarve Basin, three new palynozones (AT, SC, and CP) characterise the Silves Group from the early Carnian to early Hettangian, documenting the first Iberian occurrence of Tulesporites briscoensis and precisely delineating the Triassic-Jurassic Boundary (TJB). In the Lusitanian Basin, three palynozones (CG, IK, and Pm) constrain the Conraria and Pereiros formations to the Norian-Hettangian, with the TJB located at the base of the Pereiros Formation. Palaeoenvironmental reconstructions reveal distinct basin-specific evolutions. The Algarve Basin records an early transition from fluvial (Silves Sandstones) to marginal-marine (lagoonal and pond) settings, evidenced by abundant upper Carnian algal elements and reworked Neoproterozoic algae. Conversely, the Lusitanian Basin reflects a Norian-Hettangian marginal-marine, river-dominated setting, with microforaminiferal linings at the base of the Pereiros Formation marking the earliest marine transgression in the Lusitanian Basin. Quantitatively, both basins show a persistent dominance of xerophytic taxa, indicating a shift toward warmer, seasonally dry conditions across the TJB. Malformed sporomorphs in both records suggest environmental stress potentially linked to Central Atlantic Magmatic Province (CAMP) activity. Comparative analysis reveals that sedimentation initiated earlier in the Algarve (early Carnian) than in the Lusitanian Basin (Norian), suggesting diachronous development during Pangaea breakup. The assemblages show strong affinities with the Onslow Microflora, highlighting the Portuguese margin as a key archive for western Tethyan floral and climatic evolution.
- 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, SimonettaABSTRACT: In 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.