Percorrer por autor "Vilas-Boas, Margarida"
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- Palaeoenvironments, stratigraphy and taphonomy of an Upper Triassic vertebrate-bearing unit, Silves Group, central Algarve, southern PortugalPublication . Ruciński, Maciej; Ezquerro Ruiz, Lope; Campos, Hugo; Mateus, Octávio; Fernandes, Paulo; Vilas-Boas, Margarida; Atfy, Haytham El; Werneburg, IngmarTriassic to Lower Jurassic deposits known as the Silves Group in the Algarve, southernPortugal, have been studied for over 150 years. However, many of this unit’s sedimento-logical, stratigraphical, and palaeontological aspects remain poorly documented. Here, we present novel observations on sedimentology, stratigraphy, taphonomy, and fauna atthe Rocha da Pena site, located in the central part of the Algarve Basin. The investigatedsequence is established to correspond to the upper part of the Silves Group. The mud-stone, calcrete, and palustrine carbonate facies comprise most of the sequence thicknessand are interpreted as having been deposited within coastal alluvial mudflats to palus-trine settings under semi-arid and seasonal climates. The overlying siltstone and sand-stone facies indicate an environmental shift towards tidally influenced environments,subsequently covered by the latest Triassic to earliest Jurassic volcaniclastics and basalticlava flows. Furthermore, novel faunal elements, including actinopterygian and union-oid bivalves, are described from mudstone layers. New fossiliferous beds are identifiedwithin palustrine facies that yield numerous but poorly preserved materials assigned tocyamodontoid placodonts, hybodont sharks, and actinopterygians. The poor preserva-tion of the remains is attributed to the pedogenetic processes prevalent in the palustrinedepositional setting. A distinct faunal composition between the mudstone and palustrinefacies is observed. It is preliminarily hypothesized to be likely linked with salinity fluctu-ations, but sampling bias cannot currently be excluded. The recovered vertebrate faunaaligns most closely with the Carnian and, to a lesser extent, the Norian fossil record.Nonetheless, the precise age of the fossil-bearing levels remains uncertain and can cur-rently be reliably constrained to the upper Carnian–Rhaetian interval. Consequently,this work provides new insights into the palaeoenvironmental evolution of the westernTethys margin during the Late Triassic and highlights the relevance of the Silves Groupin reconstructing coastal-continental ecosystem dynamics in southwestern Iberia.
- The palynology of the upper triassic-lower jurassic in the Algarve and Lusitanian basins, PortugalPublication . Vilas-Boas, Margarida; Cirilli, Simonetta; Pereira, Zélia; Duarte, Luís Vítor; Fernandes, PauloHigh-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.