Breakup of Pangaea and plate kinematics of the central Atlantic and Atlas regions

Abstract

A new central Pangaea fit (type A) is proposed for the late Ladinian (230 Ma), together with a plate motions model for the subsequent phases of rifting, continental breakup and initial\ud spreading in the central Atlantic. This model is based on: (1) a reinterpretation of the process of formation of the East Coast Magnetic Anomaly along the eastern margin of North America\ud and the corresponding magnetic anomalies at the conjugate margins of northwest Africa and the Moroccan Meseta; (2) an analysis of major rifting events in the central Atlantic, Atlas and\ud central Mediterranean and (3) a crustal balancing of the stretched margins of North America, Moroccan Meseta and northwest Africa. The process of fragmentation of central Pangaea can be described by three major phases spanning the time interval from the late Ladinian (230 Ma) to the Tithonian (147.7 Ma). During the first phase, from the late Ladinian (230 Ma) to the latest Rhaetian (200 Ma), rifting proceeded along the eastern margin of North America, the northwest African margin and theHigh, Saharan and Tunisian Atlas, determining the formation of a separate Moroccan microplate at the interface between Gondwana and Laurasia. During the second phase, from the latest Rhaetian (200 Ma) to the late Pliensbachian (185 Ma), oceanic crust started forming between the East Coast and Blake Spur magnetic anomalies, whereas the Morrocan Meseta simply continued to rift away from North America. During this time interval, the Atlas rift reached its maximum extent. Finally, the third phase, encompassing the\ud time interval from the late Pliensbachian (185 Ma) to chron M21 (147.7 Ma), was triggered by the northward jump of the main plate boundary connecting the central Atlantic with the Tethys area. Therefore, as soon as rifting in the Atlas zone ceased, plate motion started along complex fault systems between Morocco and Iberia, whereas a rift/drift transition occurred in the northern segment of the central Atlantic, between Morocco and the conjugate margin of Nova Scotia. The inversion of the Atlas rift and the subsequent formation of the Atlas mountain belt occurred during the Oligocene–early Miocene time interval. In the central Atlantic, this event was associated with higher spreading rates of the ridge segments north of the Atlantis FZ. An estimate of 170 km of dextral offset of Morocco relative to northwest Africa, in the\ud central Atlantic, is required by an analysis of marine magnetic anomalies. Five plate tectonic reconstructions and a computer animation are proposed to illustrate the late Triassic and\ud Jurassic process of breakup of Pangaea in the central Atlantic and Atlas regions

The Betic Ophiolites and the Mesozoic Evolution of the Western Tethys

“…The described scenario is well represented in the paleogeograhic reconstruction of the Western Tethys of Figure 9, which is perfectly in agreement with the model proposed by Schettino and Turco [74]. According to our radiometric zircon dating on the BOA rocks (Table 1), the Betic oceanic floor initiated its development in the Pliensbachian (from about 190 to 180 Ma), and continued its metasomatic and metamorphic transformations, under oceanic floor conditions, affecting most of the constituent lithologies, from the ultramafic sequence up to the volcanic one, from the Toarcian to the Tithonian (about 177 to 152 Ma for different outcrops).…”

“…This observation is important as it implies : (1) that the Betic Ophiolites would be the only preserved relics along the Alpine Chain deriving from the westernmost end of the Tethys, which is Pliensbachian in age as is shown in Figure 9a from Schettino and Turco [74]; and (2) Figure 10 shows the palaeogeographic reconstruction for the Early Cretaceous of the central-western area of the Mediterranean by Guerrera et al [8], with slight modifications. In this figure, N-F Ocean indicates the area of oceanic floor where the BOA rocks, described in this paper, could have originated SE of the Iberian-European margin for the original paleogeographic continental domains of the tectonic units within which these ophiolites were intercalated.…”

The Tell-Rif orogenic system (Morocco, Algeria, Tunisia) and the structural heritage of the southern Tethys margin

“…In all the recent kinematic and palaeogeographic restorations (Dercourt et al, 2000;Handy et al, 2010;Schettino and Turco, 2009;Sibuet et al, 2012, Nirrengarten et al, 2018Biari et al, 2017), Iberia was located far east of its present position relatively to Africa at the beginning of the Jurassic (Fig. 5A).…”

Transform margins: development, controls and petroleum systems – an introduction

“…The first group contains transform margins which started as transfer faults between neighbouring rift units (see Bally 1982;Gibbs 1984;Bosworth 1985;Lister et al 1986;Versfelt & Rosendahl 1989;Moustafa 2002). The Central Atlantic Rift System (Schettino & Turco 2009; Fig. 1) is a typical example for this category, having its geometry characterized by numerous offsets of neighbouring rift zones.…”