Abstract
Abstract. The re-evaluation of the charophyte content of ‘Purbeckian’ sediments from several sections around Lisbon (Olelas and Brouco) and Sintra-Cascais (Murches, Atrozela and Malveira-Guincho) revealed new palaeofloral associations from the Late Tithonian of the South Lusitanian Basin (Portugal). These sections contain Globator rectispirale, G. aff. nurrensis, Nodosoclavator bradleyi, Clavator reidi, Clypeator cf. discordis, Porochara maxima, and newly described occurrences of P. jaccardi, Mesochara harrisi and nodosoclavatoroide utricles. These revised data reinforce the evidence for assigning most of the studied deposits to a Late Tithonian age, instead of the formerly accepted wider interval Tithonian to Early Berriasian (‘Purbeckian’). Population analysis and statistics were applied in order to better assess population variation of the different species.The results of this study are relevant as they contribute to improve the biostratigraphical definition of the ‘Purbeckian’ formations of Portugal and allow more accurate palaeobiogeographical interpretations within the central Tethyan domain, by comparison of the identified charophyte assemblages with documented Jurassic–Cretaceous transition charophytes from other regions.
Highlights
INTRODUCTIONThe present work presents and discusses the results of a re-evaluation study of the charophyte content of several sections (Murches, Malveira-Guincho, Atrozela, Brouco and Olelas; Fig. 1)
The present work presents and discusses the results of a re-evaluation study of the charophyte content of several sections (Murches, Malveira-Guincho, Atrozela, Brouco and Olelas; Fig. 1). These belong to the classical sections covering the Jurassic– Cretaceous transition (‘Purbeckian’ facies) of the Lisbon and Sintra-Cascais regions, formerly described by Ramalho (1971) and Rey (1972)
The ‘Purbeckian’ facies of the Sintra-Cascais and Lisbon area (Portugal) are characterized by the occurrence of charophytes typical of the Late Tithonian–Early Berriasian interval. These deposits were formed in a lagoonal to lacustrine environment (e.g. Ramalho & Rey, 1975), which allowed several species of charophytes to flourish under suitable oligo-haline to mesohaline conditions
Summary
The present work presents and discusses the results of a re-evaluation study of the charophyte content of several sections (Murches, Malveira-Guincho, Atrozela, Brouco and Olelas; Fig. 1). The charophyte assemblage, as revealed from the study of five samples from unit 4 of Rey (1972), comprises Globator rectispirale, Nodosoclavator bradleyi, Clypeator cf discordis (species already reported by Ramalho, 1971 and Rey, 1972), Porochara jaccardi, Aclistochara sp., Mesochara harrisi and nodosoclavatoroide utricles (sensu Schudack, 1993a) with new occurrences identified . This association suggests a Late Tithonian to Early Berriasian (?) age. The ‘Purbeckian’ (60–80 m) presents massive, yellow and grey limestones with marly intercalations, bearing mollusc remains, crustaceans, coprolites, sponge spicules, Nautiloculina oolithica, Anchispirocyclina lusitanica, Everticyclammina virguliana, miliolids, Permocalculus sp., dasyclads and ostracods, Average Median Minimum Maximum n
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