Discussion on ‘Breaking up continents at magma-poor rifted margins: a seismic v. outcrop perspective’ Journal of the Geological Society, London , 175, 875–882

Abstract

The contribution of Decarlis et al. (2018) focuses on the breakup of continents at magma-poor rifted margins, a topic which, as claimed by the authors, ‘is a complex yet little understood process accounting for intricate interactions between tectonic and magmatic processes’. The authors use field observations of a classical Ligurian ophiolites exposure, the Bracco–Levanto, to compare it with the setting of the East Antarctica margin analysed by seismic survey and interpretations (Geoscience Australia Survey 228). The authors state that the overall aim is to combine detailed structural mapping and petrological data from the fossil exhumed example (Bracco–Levanto) with architectural features observed in seismic sections from present-day ocean–continent transitions (OCTs). Moreover, as explicitly mentioned in the title, the authors aim at discussing the implications of their analysis for the interpretation of the nature of seismic interfaces and of the character of rocks at ultra-distal margins. It also helps to constrain the timing and type of processes controlling lithospheric breakup and onset of steady-state, localized seafloor spreading. Actually, the 3D complexity of the tectonic architecture of the Ligurian ophiolites, if not properly taken into account, can cause uncertainty in the analyses and projected goals; therefore, in the following pages I will complement and refine the geological information provided by Decarlis et al. (2018), with the purpose of helping future works on the subject. Moreover, my contribution aims to complete the references on the study area, providing further structural information and details and amending some misinterpretations included in the paper by Decarlis et al. (2018). As recognized by Decarlis et al. (2018), the Bracco–Levanto area represents a key region for the studies of the Ligurian Tethys ophiolites, having a special value in the history of modern geological knowledge. In the early 1960s Bailey & McCallien (1960) analysed the local geology …