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- Title
Linear Inversion of Fluvial Topography in the Northern Apennines: Comparison of Base‐Level Fall to Crustal Shortening.
- Authors
Fisher, J. A.; Pazzaglia, F. J.; Anastasio, D. J.; Gallen, S. F.
- Abstract
Fluvial 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. Plain Language Summary: We use the longitudinal profiles of river channels—plots of channel elevation against streamwise distance—to model the history of base‐level fall at river mouths. Base‐level fall is compared to published fault slip and sediment deposition rates assembled from geologic data. Each data set shows generally consistent trends through time. A synchronous increase in base‐level fall rate within the last 1 Myr is observed ubiquitously across all six catchments. We interpret this as indicative of a change in the style of mountain building ∼1 Myr ago caused by the activation of a deep thrust fault that is uplifting most of the northern Apennine northeastern flank. An assessment of all the data sets indicates how the northern Apennine mountains were built over the past ∼3 Myr and allows for discussion on the versatility and challenges of our modeling approach. These results show that river profiles can be sensitive recorders of mountain building and, when interpreted alongside other complimentary records, can be used to critically evaluate model results in the context of landscape evolution. The approach used here can be applied to understand the history of mountain building in other settings across the globe. Key Points: Linear inversion of river longitudinal profiles is a versatile tool to restore base‐level fall histories from measured physical parametersWe compare base‐level fall histories from rivers to complimentary and independent records from growth strata and fluvial terracesResults add to the growing amount of data supporting out‐of‐sequence thick‐skinned deformation of the northern Apennines of Emilia Romagna
- Publication
Tectonics, 2022, Vol 41, Issue 11, p1
- ISSN
0278-7407
- Publication type
Article
- DOI
10.1029/2022TC007379