Preprints
https://doi.org/10.5194/egusphere-2024-1135
https://doi.org/10.5194/egusphere-2024-1135
29 Apr 2024
 | 29 Apr 2024
Status: this preprint is open for discussion.

Transpressional tectonics during the Variscan-Alpine cycle transition: supporting a multi-rifting model, evidence from the European western Southern Alps

Emanuele Scaramuzzo, Franz A. Livio, Maria Giuditta Fellin, and Colin Maden

Abstract. We delve into the transition between the Paleozoic Variscan cycle and the Meso-Cenozoic Alpine supercontinent cycle, both of which have played a pivotal role in shaping the central European-Mediterranean plate’s architecture. Our focus is on the European western Southern Alps (Varese Area, N Italy), where we documented the tectonic events occurred during this transition. Two main scenarios have been proposed so far for this transition: i) a single, long-lasting, Permo-Triassic rifting event, culminating in the opening of the Alpine Tethys, or ii) multiple, distinct rifting events, preceding the onset of the Alpine cycle. By means of a tectono-stratigraphic and thermochronological approach, we recognized a first early Permian rifting stage associated with magmatic activity, followed during the early-middle Permian by transpressive tectonics and regional-scale erosion that signal the end of the first cycle of crustal rifting. During the Middle Triassic, a second event initiated, which, we propose, marks the onset of the Alpine Tethys opening. This event could represent the stretching phase, which predates the well documented Upper Triassic crustal-thinning phase. Based on our findings, we propose that the Middle Triassic stretching phase represents the first stage of the Alpine Tethys rifting, thereby rejecting the hypothesis of a continuous Permo-Triassic long-lasting phase of extension.

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Emanuele Scaramuzzo, Franz A. Livio, Maria Giuditta Fellin, and Colin Maden

Status: open (until 17 Jun 2024)

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Emanuele Scaramuzzo, Franz A. Livio, Maria Giuditta Fellin, and Colin Maden
Emanuele Scaramuzzo, Franz A. Livio, Maria Giuditta Fellin, and Colin Maden

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Short summary
The theory of plate tectonics postulates that the opening and closure of an ocean are tied together into a cycle, namely the Wilson cycle. The rocks exposed in the western Southern Alps preserve the geologic record of two Wilson cycles: an earlier one, which led to the formation of the Variscan orogen, and the recent one, which led to the formation of the European Alps. We delved into this transition, and we found that it did not occur smoothly but through several abrupt changes.