Permian to Triassic sequences from selected continental areas of southwestern Europe
C. Virgili, G. Cassinis, J. Broutin, 2006. "Permian to Triassic sequences from selected continental areas of southwestern Europe", Non-Marine Permian Biostratigraphy and Biochronology, Spencer G. Lucas, Giuseppe Cassinis, Joerg W. Schneider
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This contribution is a tentative reconstruction of the still-debated geological history in the primarily continental domains now represented in various parts of southwestern Europe, between the end of the Variscan diastrophism and the beginning of the Alpine sedimentary evolution. Data and interpretations vary from one region of terrestrial rocks to another. Despite this, we have tried to highlight the most typical and significant geological features. From the Carboniferous to Triassic, palaeontological investigations of the macroflora, microflora and tetrapod footprints, as well as radiometric data, generally point out the presence of three main ‘tectono-stratigraphic units’ (TSUs), separated by marked unconformities and gaps of as yet uncertain duration. The most important geological episode generally started about the Early/Middle Permian boundary and later spanned discontinuously and intensely throughout Middle Permian (Guadalupian) time. It was characterized by specific tectonic, magmatic, thermal and basinal features, which could mark the presumed change suggested by some authors from a Pangaea B to a Pangaea A. In this context, it is worth mentioning that the unconformable Middle?-Upper Permian higher TSU in Spain consists of ‘Buntsandstein’-type red beds, sometimes yielding a Thuringian flora; differently, in southern France, such as in the Lodève area, the Buntsandstein is Anisian and thus constitutes a later Triassic sequence, which rests unconformably above the as yet undefined (Mid-Late) Permian age assessment of the ‘La Lieude fossil site’; in the Southern Alps, the ‘Second tectono-sedimentary Cycle’ emphasized from the recent literature, which is initially made up of the Verrucano Lombardo-Val Gardena Sandstone red clastics, is in part laterally and upwardly replaced, east of the Adige Valley, by the sulphate evaporite to shallow-marine Bellerophon Formation. It is thus represented by continental and marine sediments generally pertaining to Late Permian (post-‘Lower Tatarian’) time and can be interpreted, in the light of the geological context of the region, as an Upper Permian and Lower Triassic TSU of a slightly younger numerical order (i.e. TSU 3 in place of TSU 2).
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Non-Marine Permian Biostratigraphy and Biochronology
During the Permian, the single supercontinent Pangaea stretched from pole to pole. Early Permian glacial deposits are found in southern Gondwana. Along the sutures of Pangaea, mountain ranges towered over vast tropical lowlands. Interior areas included dry deserts where dune sands accumulated. Gypsum and halite beds document the evaporation of hot, shallow seas that formed the most extensive salt deposits in the geological record. The Permian period (251 to 299 Ma) encompasses nine ages (stages) arranged into three epochs (series). Most of the Permian marine timescale has been defined by global stratotype sections and points for the stage boundaries. This volume presents new data regarding the biostratigraphy and biochronology of the non-marine Permian and provides a basis for temporally ordering Permian geological and biotic history on land, and correlating that history to events in the marine realm.