The Lourinhã Formation: the Upper Jurassic to lower most Cretaceous of the Lusitanian Basin, Portugal – landscapes where dinosaurs walked

Abstract

This work, as a fieldtrip guide, aims to provide a glimpse into the palaeoenvironments, palaeontology, and diagenesis of one of the most productive areas for Late Jurassic dinosaurs and other vertebrates in Europe, namely, the sites of the Lourinhã Formation, which is coeval with the Morrison Formation of the midwest USA.The Late Jurassic rifting phase of the Lusitanian Basin created several sub-basins separated by major crustal faults. In the western and central areas of the basin, the Caldas da Rainha structure separates three sub-basins with different subsidence and infill characteristics (Consolação to the west, Bombarral-Alcobaça to the northeast, and Turcifal to the southeast). The Upper Jurassic-lowermost Cretaceous succession exposed in the coastal cliffs located between Nazaré and Santa Cruz belongs to the Consolação Sub-basin, whereas the coastal outcrops between Santa Cruz and Ericeira show units of the Turcifal Sub-basin.To place the stops into a coherent context, selected units of the fieldtrip area are detailed. The stratigraphy of the Upper Jurassic of the Lusitanian Basin is quite complex, and no fully accepted overall proposal exists. Thus, a review of lithostratigraphy, sedimentology, age and environmental interpretations is presented. Interpretations of palaeoclimate, palaeogeography, and taphonomy contribute to establishing an overview of the landscape where dinosaurs lived and to understanding the conditions for their fossilization and preservation. This trip, which takes place from north to south, focuses on the vertebrate content, sedimentology, and stratigraphy of the deposits. The first stop at Consolação examines the upper Kimmeridgian shallow-marine to deltaic Alcobaça Formation, which underlies the Lourinhã Formation. Further south, the Paimogo fort cape gives a scenic view of the Lourinhã Formation: to the north, the Praia da Amoreira and Porto Novo members (lower coastal plain alluvium, including distal fan and meandering fluvial systems; upper Kimmeridgian), and, to the south, the Praia Azul Member (lower coastal plain alluvium with three brackish-marine faunally distinct transgressive carbonate levels; uppermost Kimmeridgian to lowermost Tithonian). In Paimogo, we visit sites where dinosaur eggs and a sauropod skeleton have been found. The stop at the Museum of Lourinhã allows a visit to one of the most important collections of Late Jurassic vertebrates in Europe. The last fieldtrip stop at Porto da Calada examines the top of the Assenta Member of the Lourinhã Formation (meandering fluvial system with intercalations of shallow-marine lagoonal carbonates; upper Tithonian to lowermost Berriasian) and the Porto da Calada Formation (meandering fluvial system with thin levels of estuarine and intertidal flats carbonates; Berriasian) and thus includes the Jurassic-Cretaceous boundary.Keywords: Upper Jurassic, Lourinhã Formation, Portugal, Lusitanian Basin, Dinosaurs ResumoEste trabalho, como um guião de campo, visa dar uma visão sobre os paleoambientes, paleontologia e diagénese...

Upper Jurassic sauropod record in the Lusitanian Basin (Portugal): Geographical and lithostratigraphical distribution

“…The Praia da Amoreira-Porto Novo Formation crops out in several areas along this sector, especially in the sedimentary sections from São Bernardino to Paimogo and from Porto Dinheiro to Praia de Santa Rita (Hill, 1988;Manuppella et al, 1999;Mateus et al, 2013). This late Kimmeridgianbasal Tithonian formation (Fürsich, 1981; Manup-FIGURE 12.…”

“…This formation seems to be coincident with the upper part of the Alcobaça, Praia da AmoreiraPorto Novo, Sobral, Freixial, and Bombarral Formations referenced by other authors, including the Portuguese Geological Surveys (e.g., Manuppella et al, 1999). The use of this unit outside the area corresponding to the Consolação Sub-basin of Taylor et al (2014) is not completely established in literature (e.g., Hill, 1988;Kullberg et al, 2006;Schneider et al, 2009;Ribeiro and Mateus, 2012;Kullberg et al, 2013;Mateus et al, 2013). Yagüe et al (2006) therefore incorporate the entire Alcobaça Formation and the previously defined Lourinhã Formation into a new lithostratigraphic unit, the Lourinhã Group.…”

Dacentrurine stegosaurs (Dinosauria): A new specimen of Miragaia longicollum from the Late Jurassic of Portugal resolves taxonomical validity and shows the occurrence of the clade in North America

“…Simplified geological map of the central west coast of Portugal adapted from [73]. B , Detail of Geologic Map of Portugal at scale 1:50 000, sheet 26–C (Peniche) [72] including Atouguia da Baleia and the likely provenance of MG 4863 (circled in red), label simplified and adapted sensu [74]. C , Lithostratigraphy of the Lourinhã Formation from [74].…”

“…If the mentioned coordinates are definitely the locality of MG 4863, then the specimen was found in the beds identified in [72] as “J 3-4 —Upper sandstones with plant and dinosaur fossils”, which is equivalent to the Tithonian aged Santa Rita-Assenta Member of the Lourinhã Formation ( sensu [74]; synonymous also with the Bombarral Formation in [75], and the Portlandian in [76] and [77]; Fig 5C). The description by [72] of this area as “muddy sandstones with intercalations of mudstones and marls” also matches the matrix of MG 486.…”

“…The fossil sites with described stegosaurian skeletal remains in Portugal are all part of the Lusitanian Basin, more precisely are all purportedly part of the Lourinhã Formation (Fig 5A; see [22,35,40,41,72,76]). The Lourinhã Formation currently can be considered as Late Kimmeridgian to Late Tithonian [44,74], and is comprised of alternated sequence of sandstone and mudstone of continental fluvial facies (such as distal alluvial fans and upper deltas) punctuated by episodes of marine influence [73,74]. Underlying it are the Kimmeridgian limestones from shallow marine to brackish environments of the Alcobaça Formation, while at the top it is bounded by the sandstones of the Porto da Calada Formation, mainly Tithonian-Berriasian boundary in age.…”