Geodinamics

During the late Neoproterozoic and Paleozoic times, the Southern Andes of Argentina and Chile (21º-55º S) formed part of the southwestern margin of Gondwana. During this period of time, a set of continental fragments of variable extent and allochtony was successively accreted to that margin, resulting in six Paleozoic orogenies of different temporal and spatial extension: Pampean (Ediacaran-early Cambrian), Famatinian (Middle Ordovician-Silurian), Ocloyic (Middle Ordovician-Devonian), Chanic (Middle Devonian-early Carboniferous), Gondwanan (Middle Devonian-middle Permian) and Tabarin (late Permian-Triassic). All these orogenies culminate with collisional events, with the exception of the Tabarin and a part of the Gondwanan orogenies that are subduction-related.

One hundred years ago in 1915 ‘Die Entstehung der Kontinente und Ozeane’ by Alfred Wegener was
published, destined to become one of the most controversial geological opus in the first half of the twentieth
century. Wegener is the first to combine the most diverse geological (sensu lato) evidences in a single great
synthesis. Nonetheless, apart from few upholders, the initial reaction to the drift hypothesis was fierce
opposition, and the strongest criticism came from geophysics, the same discipline that, paradoxically,
starting from the 1950s led to the Plate Tectonics revolution and, ultimately, to a complete re-evaluation
of Wegener’s hypothesis. In the present paper we discuss the initial reaction of Italian scientists to the
original continental drift theory, with particular focus on the period between the two world wars. Italian
geologists like Fossa-Mancini and Gortani were almost favourable to the new theory, while authors such
as Vardabasso and Sacco were neutral or even hostile to the new hypothesis, so iconoclastic for the widely
accepted fixist vision of the time. In any case, all these scientists agreed that the new theory had great
potential for reopening an enthusiastic debate on issues that were given as established paradigms – the
genuine way for progress in science.

Macaronesia is a complex oceanic region spanning three tectonic plates in the northeast Atlantic ocean. It is composed of four archipelagos, widely distributed and limited to the east by the Iberian Peninsula and northwestern coast of Africa. This study aims to clarify recent Macaronesian kinematics from 19 GNSS stations located on the four archipelagos and the Iberian and African coastlines. The analysis is based on nearly 15 years of common data acquisition and aimed to detect new effects of intraplate tectonics or similar local/regional events consistent with calculated ground displacements. Evaluating the GNSS stations residual velocities relative to those expected from the NNR-MORVEL56 model, higher residuals were found at continental coastal stations (Africa) than at oceanic ones (Canaries and Madeira). From the computed strain rate map, the possible existence of a shear zone connecting the Gloria and Transmoroccan fault systems, already mentioned by other authors, was depicted. Cluster statistical analysis of the horizontal residual velocities helped to identify tectonic boundaries in Macaronesia and four groups of analogous intraplate residual velocities within this region. Three of four groups were identified in the Azores, highlighting the African-Nubian-Eurasian diffuse plate boundary in this region. Furthermore, in the Canary Islands, two distinct kinematic behaviours were detected, possibly due to the activity along a previously detected tectonic fault between Tenerife and Gran Canaria, where some stations have similar intraplate residuals to those at Madeira and Cape Verde stations, while others have similar intraplate residuals to those of continental stations. Finally, all stations on I. Barbero et al. ii Stud. Geophys. Geod., 65 (2021) oceanic crust, except Cape Verde, present recent ground subsidence which may be attributed to isostatic adjustment.