New Insights on the Upper Triassic Silves Group in Algarve Basin, Portugal: Palynological, paleophytogeography and paleoclimatology advances - 01/10/24

Doi : 10.1016/j.geobios.2024.08.001

Margarida Vilas-Boas ^a,^⁎ , Zélia Pereira ^b, Simonetta Cirilli ^c, Paulo Fernandes ^a
^a CIMA, Centre of Marine and Environmental Research\ARNET - Infrastructure Network in Aquatic Research, University of Algarve, Campus de Gambelas, 8000-139 Faro, Portugal
^b LNEG, Laboratório Nacional de Energia e Geologia, Rua da Amieira, 4465-965 S. Mamede de Infesta, Porto, Portugal
^c Dipartimento di Fisica e Geologia, Università degli Studi di Perugia, 06123 Perugia, Italy

^⁎Corresponding author.

Sous presse. Épreuves corrigées par l'auteur. Disponible en ligne depuis le Tuesday 01 October 2024

Highlights

•	New palynological evidence of the Silves Group, Algarve Basin, Portugal is presented.
•	The Triassic-Jurassic boundary lies in the upper part of the Silves Group in the Silves Marl-Carbonate Evaporitic Complex, in the Loulé Rock Salt Mine.
•	Onslow microflora is recognized in the Silves Group, lower part of the Silves Marl-Carbonate Evaporitic Complex.

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Abstract

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.