57 research outputs found
The structural history of the Mont Blanc massif with regard to models for its recent exhumation
Deformation and metamorphism in the Bard area of the Sesia Lanzo Zone, Western Alps, during subduction and uplift
Turning the Orogenic Switch: SlabâReversal in the Eastern Alps Recorded by LowâTemperature Thermochronology
Many convergent orogens, such as the eastern European Alps, display an asymmetric doubly vergent wedge geometry. In doubly vergent orogens, deepest exhumation occurs above the retroâwedge. Deepâseismic interpretations depict the European plate dipping beneath the Adriatic, suggesting the proâwedge location on the north side of the orogen. Our new thermochronometer data across the Eastern Alps confirm distinct shifts in the locus of exhumation associated with orogenâscale structural reorganizations. Most importantly, we find a general MidâMiocene shift in exhumation (in the Tauern Window and the Southern Alps) and focus of modern seismicity across the Southern Alps. Taken together, these observations suggest a subduction polarity reversal at least since the MidâMiocene such that the presentâday proâwedge is located on the south side of the Alps. We propose a transient tectonic state of a slowâandâongoing slab reversal coeval with motion along the Tauern Ramp, consistent with a presentâday northward migration of drainage divides.Plain Language Summary:
When tectonic plates collide, they bend downwards and form two lithospheric wedges dipping in opposite directions, such as in the Eastern Alps. We present new crustal cooling data along a transect in the Eastern Alps confirming that surface rocks across the central Tauern Window originated from the deepest structural levels along the transect. South of the Tauern Window rocks were exhumed from higher depths compared to those north of it and were exhumed more recently, while seismic activity is also focused across the Southern Alps. These observations suggest a subduction polarity reversal because they are inconsistent with the original southern and northern locations of overriding and subducting plates, respectively, >15 million years ago. This interpretation is contrary to lithosphereâscale tomography that shows no change in subduction polarity. Therefore, we propose a transient tectonic state, that is, a slowâandâongoing subduction polarity reversal that initiated when Tauern Window rocks began their steep ascent to the surface along a deepâseated fault known as the Tauern Ramp. This study bridges observations in the mantle, crust and on the surface over geologic time.Key Points:
Thermochronologic data in the Eastern Alps is consistent with a transient tectonic state toward complete slab reversal.
The proâwedge has switched from north to south of the Periadriatic Fault along TRANSALP.
MidâMiocene motion along the Tauern Ramp is the consequence of slabâreversal.Deutsche Forschungsgemeinschaft (DFG)
http://dx.doi.org/10.13039/50110000165
Turning the Orogenic Switch: SlabâReversal in the Eastern Alps Recorded by LowâTemperature Thermochronology
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