strati.ch - Lithostratigraphic Lexicon of Switzerland

Representation and status

Historical Variants: Theodul Glacier Unit (Bucher et al. 2020), Theodulgletscher Slice (TK500, Gouffon et al. 2024), Écaille du glacier du Théodule, Scaglia del ghiacciaio del Theodul

Description: Bucher et al. 2020 ont décrit une nouvelle unité découverte par le glacier du Theodul, constituée de roches semblables à celles de la Dent-Blanche – Sesia, mais avec un métamorphisme de haute pression du même âge que celui de Zermatt-Saas-Fee (et non de Sesia). Cette unité, de même que la nappe du Mont Emilius, l’écaille d'Etirol-Levaz et les écailles de Chatillon-St-Vincent, affleurent entre la nappe de Zermatt-Saas-Fee et celle du Tsaté. Ces unités ont donc une histoire identique à celle des nappes penniques supérieures.

Paleogeography

Adriatic continental margin :

southern, passive continental margin / platform

Tectonic unit (resp. main category)

Kind of protolith

Definition: Bucher K., Weisenberger T. B., Weber S., Klemm O., Corfu F. (2020) : The Theodul Glacier Unit, a slab of pre-Alpine rocks in the Alpine meta-ophiolite of Zermatt-Saas, Western Alps. Swiss J. Geosci. 113/1

Definition: Gouffon Yves (Editor) (2024) : Tectonic Map of Switzerland 1:500000, Explanatory notes. Federal Office of Topography swisstopo, Wabern

p.69: The Mont Emilius Nappe, the Etirol-Levaz Slice, the Châtillon-St-Vincent Slices (Dal Piaz 1999 and ref. therein) and the Theodulgletscher Slice (Bucher et al. 2020), located between the Zermatt - Saas Fee Nappe and the Tsaté Nappe, comprise eclogitic continental basement rocks. Due to the similarity of their pre-Alpine lithology with that of the Dent Blanche and Sesia nappes, their origin is probably the Adriatic continental margin. However, these units occupy a lower structural level than the Dent Blanche and Sesia nappes that belong tectonically to the Salassic domain. They exhibit a tectono-metamorphic history similar to that of the Zermatt - Saas Fee Nappe, including the Early Eocene age for their high-pressure metamorphism (Dal Piaz et al. 2001, Weber et al. 2015). These units likely derived from extensional allochthons, formed during the Jurassic opening of the Piemonte-Liguria Ocean in a more distal position than the Cervinia Terrane from which the Salassic nappes originate (see chap. 7).