Abstract
Abstract. Analysis of new detrital apatite fission-track (AFT) ages from modern river sands, published bedrock and detrital AFT ages, and bedrock apatite (U-Th)/He (AHe) ages from the Northern Apennines provides new insights into the spatial and temporal patterns of erosion rates through time across the orogen. The pattern of time-averaged erosion rates derived from AHe ages from the Ligurian side of the orogen illustrates slower erosion rates relative to AFT rates from the Ligurian side and relative to AHe rates from the Adriatic side. These results are corroborated by an analysis of paired AFT and AHe thermochronometer samples, which illustrate that erosion rates have generally increased through time on the Adriatic side but have decreased through time on the Ligurian side. Using an updated kinematic model of an asymmetric orogenic wedge, with imposed erosion rates on the Ligurian side that are a factor of 2 slower relative to the Adriatic side, we demonstrate that cooling ages and maximum burial depths are able to replicate the pattern of measured cooling ages across the orogen and estimates of burial depth from vitrinite reflectance data. These results suggest that horizontal motion is an important component of the overall rock motion in the wedge, and that the asymmetry of the orogen has existed for at least several million years.
Highlights
The Apennine mountains of Italy are an active orogen characterized by contemporaneous extensional and compressional tectonics
We present evidence from multiple thermochronometers that the spatial and temporal patterns of erosion rates in the Northern Apennine orogen differ at the regional scale
New detrital apatite fission-track (AFT) cooling ages from the Ligurian side of the orogen are similar to AFT bedrock cooling ages from the Ligurian side, illustrating that the detrital ages reflect a true exhumation signal across the Northern Apennines
Summary
The Apennine mountains of Italy are an active orogen characterized by contemporaneous extensional and compressional tectonics. The interplay between extension and compression has affected the overall tectonic evolution of the Northern Apennines and, in particular, its exhumational and topographic evolution. Thomson et al, 2010; Malusà and Balestrieri, 2012) and at the regional scale along the extensional Ligurian side of the orogen Spatial variability is large, the overall pattern of exhumation is consistent with kinematic models of the Apennines as an orogenic wedge, with deformation driven by frontal accretion on the Adriatic margin, and erosion and extension across the mountain belt (Thomson et al, 2010)
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