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Triassic 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.
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Palavras-chave
Triassic-Jurassic palaeoenvironments Sedimentology Taphonomy Vertebrates Portugal
Contexto Educativo
Citação
Editora
Scandinavian University Press