Linear Inversion of Fluvial Topography in the Northern Apennines: Comparison of Base‐Level Fall to Crustal Shortening

Abstract

AbstractFluvial terraces, longitudinal river profiles, and growth strata carry comparable records of the deformation history in tectonically active mountain belts. In the northern Apennines, these markers are preserved across an actively uplifting, steep mountain front. We take advantage of this setting to model base‐level fall histories reconstructed from a linear inversion of fluvial topography on six transverse catchments spanning 110 km along the strike from Bologna to Parma. We compare these histories to records of crustal shortening preserved in growth strata. The fluvial inversion model is based on the detachment‐limited stream‐power model and considers the variable erodibility of bedrock lithology. Uplift is assumed to be spatially uniform at the catchment scale and crudely in balance with long‐term 10Be terrestrial cosmogenic nuclide (TCN) erosion rates that range from ∼0.3 to 0.7 mm yr−1. The model predicts rates of base‐level fall that are comparable with published rates of fault slip from growth strata and incision from terrace deposits. The modeling demonstrates how orogenic shortening and topographic growth are nonuniform and partitioned along the strike of the Apennine mountain front. Rivers record steady uplift in the last ∼1 Myrs, temporally coincident with overfilling of the Po Plain and reduction of shallow fault slip, supporting a proposed switch from thin‐to thick‐skinned crustal shortening. These results are a novel example of base‐level fall records assembled from both the erosional source and depositional sink and highlight the versatility and challenges of fluvial inversion modeling.