Lepontin dome

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Geology of the Alps
Tectonic subdivision
Helvetic Zone Penninic nappes Austroalpine nappes Southern Alps
Formation and rocks
Bündner schist flysch molasse
Geological structures
Aarmassif Dent Blanche klippe Engadine Line Engadine window Flysch zone Giudicárie line Greywacke zone Hohe Tauern window Molasse basin Penninic thrustfront Periadriatic Seam Ivrea zone Lepontin dome Rechnitz window Rhône-Simplon line Sesia unit
Paleogeographic terminology
Valais Ocean Briançonnais zone Piemont-Liguria Ocean Apulian or Adriatic plate Alps portal Geology portal
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The Lepontine dome or Lepontin dome is a region of tectonic uplift in the Swiss part of the Alps. It is located in the Lepontine Alps and Glarus Alps.

The Alps north of the Periadriatic Seam are usually divided into three large nappe complexes. From bottom to top these are the Helvetic, Penninic and Austroalpine nappes. East of the dome all three are found on top of each other. The same counts for the region west of the dome, if the Sesia unit is seen as part of the Austroalpine nappes. The dome itself however only shows Penninic and Helvetic (the boundary between the two is still disputed) rocks. Apparently the uplift of the dome caused the upper Austroalpine material to be totally eroded away.

The creation of the dome was caused by a phase of east-west directed extension in the Miocene that occurred throughout the Eastern and Central Alps. This extensional phase was probably a result of slab detachment in the upper mantle. Similar large extensional structures appear in more places in the Alps, examples are the Hohe Tauern window and the smaller Engadin and Rechnitz windows.^[1]