The Gondwana–Laurussia convergence process: evidence from the Middle Mississippian (Viséan) palynostratigraphic record

Abstract

The Gondwana–Laurussia convergence process can be explored by studying the Middle Mississippian (Viséan) palynoflora of northwest Africa. Statistical analysis of the Viséan miospore assemblages reported from Morocco defines two populations, one with clear Laurussian affinity from the northern margin of the Western Meseta, and the other, more Gondwanan in composition, from the southern part of the Western Meseta and Anti-Atlas. Moreover, no transitional assemblages have been described from the region. These palynofloral variations are a consequence of the complex palaeogeography of the northwest African margin, which was controlled by the Variscan Orogeny during Viséan times. Taking into consideration the palynofloral affinity of the miospore assemblages reported throughout the entire North African margin and the Middle East, it is possible to envisage a Late Carboniferous Pangaea amalgamation process initially evolving from the west, while in the east the ocean separating Gondwana and Laurussia persisted as an effective barrier to floral migration.

Tectonic evolution of the Rehamna metamorphic dome (Morocco) in the context of the Alleghanian-Variscan orogeny

“…Simultaneously, intracontinental basins with interstratified bimodal magmatism formed throughout the whole Western Meseta [Hoepffner et al, 2006b, and references therein]. In these basins, the Visean to early Serpukhovian sedimentation [e.g., Playford et al, 2008;González et al, 2011] is contemporaneous with a thermal event dated at 330-320 Ma in the Central Massif ( [Huon et al, 1987]; white mica K-Ar ages on slates). It is also coeval with the magmatic activity and fluid circulations in the Jebilet as shown by the emplacement of cordierite-bearing granodiorites at~327 Ma (Rb-Sr isochrones, Mrini et al [1992]) and a granitic sill emplaced at~330 Ma (U-Pb zircon, [Essaifi et al, 2003]), together with sulphide deposits dated at~332 Ma by 40 Ar/ 39 Ar method on hydrothermal sericite [Marcoux et al, 2008].…”