The interplay between surface processes and tectonics in the actively extending central Italian Apennines

The overall objective of this project is to improve our understanding of the interplay between surface processes and tectonics in active continental rifts, based on the central part of the Italian Apennines. Three key aspects are investigated: i) The impact of dynamic mantle-induced surface uplift on normal fault activity and topographic development in active continental rifts. ii) The evolution of drainage networks in response to extensional faulting and regional uplift and the main controlling mechanisms. iii) The impact of drainage network evolution on sediment dispersal, basin stratigraphy and transient landscape evolution. These three aspects are investigated through a combined field and numerical modelling approach. This approach allows for the direct use of field data for constraining numerical models, as well the direct testing of model-based findings. Synthesised published basin stratigraphic, fault slip and geomorphic data together with new geomorphic and sedimentological fieldwork provide high quality and detailed datasets of stratigraphic and landscape evolution in the central Apennines. Regional drainage network evolution in the central Apennines is primarily controlled by the balance between the rates of filling and subsidence of normal fault-bounded basins. Basin filling occurs through the supply of sediment and water, whereas basin subsidence is mainly controlled by slip on the main basin-bounding normal fault. Drainage integration occurs when initially underfilled, endorheic basins become overfilled with sediment and water allowing basins to overspill. Because basin overspill, in turn, allows water and sediment to cascade downstream to adjacent basins where it can trigger a next drainage integration event, drainage integration predominantly follows a top-down pattern. Furthermore, drainage integration acts as a first-order control on basin stratigraphy and geomorphic development in the central Apennines, and produces a highly dynamic landscape evolution with transient conditions that can persist in the landscape for several millions of years. Two-dimensional thermo-mechanical modelling results demonstrate how the removal of mantle lithosphere leads to regional surface uplift and the localisation of extensional strain in the area of high topography. This is because the upwelling of hot buoyant sub-lithospheric mantle within the lithospheric gap causes both isostatic surface uplift and considerable weakening of the crust. Pre-defined (inherited) fault structures in this area of uplift and weakened crust become activated if the area is subject to a low rate of far-field extension. Faults interact, causing the locus of fault activity to migrate across-strike, and fault slip rates to vary markedly over 104-105 year timescales. Overall, these experiments show that mantle lithosphere removal can explain many first-order characteristics of the central Apennines, such as the correlation between fault strain rates, topography and surface uplift, enhanced surface heat fluxes, negative gravity anomalies and low P-wave velocities in the upper mantle

Drainage integration and sediment dispersal in active continental rifts:A numerical modelling study of the central Italian Apennines

Progressive integration of drainage networks during active crustal extension is observed in continental areas around the globe. This phenomenon is often explained in terms of headward erosion, controlled by the distance to an external base‐level (e.g. the coast). However, conclusive field evidence for the mechanism(s) driving integration is commonly absent as drainage integration events are generally followed by strong erosion. Based on a numerical modelling study of the actively extending central Italian Apennines, we show that overspill mechanisms (basin overfilling and lake overspill) are more likely mechanisms for driving drainage integration in extensional settings and that the balance between sediment supply vs. accommodation creation in fault‐bounded basins is of key importance. In this area drainage integration is evidenced by lake disappearance since the early Pleistocene and the transition from internal (endorheic) to external drainage, i.e. connected to the coast. Using field observations from the central Apennines, we constrain normal faulting and regional surface uplift within the surface process model CASCADE (Braun & Sambridge, 1997, Basin Research, 9, 27) and demonstrate the phenomenon of drainage integration, showing how it leads to the gradual disappearance of lakes and the transition to an interconnected fluvial transport system over time. Our model results show that, in the central Apennines, the relief generated through both regional uplift and fault‐block uplift produces sufficient sediment to fill the extensional basins, enabling overspill and individual basins to eventually become fluvially connected. We discuss field observations that support our findings and throw new light upon previously published interpretations of landscape evolution in this area. We also evaluate the implications of drainage integration for topographic development, regional sediment dispersal and offshore sediment supply. Finally, we discuss the applicability of our results to other continental rifts (including those where regional uplift is absent) and the importance of drainage integration for transient landscape evolution.publishedVersio

The interplay between surface processes and tectonics in the actively extending central Italian Apennines

The overall objective of this project is to improve our understanding of the interplay between surface processes and tectonics in active continental rifts, based on the central part of the Italian Apennines. Three key aspects are investigated: i) The impact of dynamic mantle-induced surface uplift on normal fault activity and topographic development in active continental rifts. ii) The evolution of drainage networks in response to extensional faulting and regional uplift and the main controlling mechanisms. iii) The impact of drainage network evolution on sediment dispersal, basin stratigraphy and transient landscape evolution. These three aspects are investigated through a combined field and numerical modelling approach. This approach allows for the direct use of field data for constraining numerical models, as well the direct testing of model-based findings. Synthesised published basin stratigraphic, fault slip and geomorphic data together with new geomorphic and sedimentological fieldwork provide high quality and detailed datasets of stratigraphic and landscape evolution in the central Apennines. Regional drainage network evolution in the central Apennines is primarily controlled by the balance between the rates of filling and subsidence of normal fault-bounded basins. Basin filling occurs through the supply of sediment and water, whereas basin subsidence is mainly controlled by slip on the main basin-bounding normal fault. Drainage integration occurs when initially underfilled, endorheic basins become overfilled with sediment and water allowing basins to overspill. Because basin overspill, in turn, allows water and sediment to cascade downstream to adjacent basins where it can trigger a next drainage integration event, drainage integration predominantly follows a top-down pattern. Furthermore, drainage integration acts as a first-order control on basin stratigraphy and geomorphic development in the central Apennines, and produces a highly dynamic landscape evolution with transient conditions that can persist in the landscape for several millions of years. Two-dimensional thermo-mechanical modelling results demonstrate how the removal of mantle lithosphere leads to regional surface uplift and the localisation of extensional strain in the area of high topography. This is because the upwelling of hot buoyant sub-lithospheric mantle within the lithospheric gap causes both isostatic surface uplift and considerable weakening of the crust. Pre-defined (inherited) fault structures in this area of uplift and weakened crust become activated if the area is subject to a low rate of far-field extension. Faults interact, causing the locus of fault activity to migrate across-strike, and fault slip rates to vary markedly over 104-105 year timescales. Overall, these experiments show that mantle lithosphere removal can explain many first-order characteristics of the central Apennines, such as the correlation between fault strain rates, topography and surface uplift, enhanced surface heat fluxes, negative gravity anomalies and low P-wave velocities in the upper mantle

Contrasting Geomorphic Response to Normal Fault Growth During Single and Multi-phase Rifting

International audienc

Contrasting Geomorphic and Stratigraphic Responses to Normal Fault Development During Single and Multi-Phase Rifting

Understanding the impact of tectonics on surface processes and the resultant stratigraphic evolution in multi-phase rifts is challenging, as patterns of erosion and deposition related to older phases of extension are overprinted by the subsequent extensional phases. In this study, we use a one-way coupled numerical modelling approach between a tectonic and a surface processes model to investigate topographic evolution, erosion and basin stratigraphy during single and multi-phase rifting. We compare the results from the single and the multi-phase rift experiments for a 5 Myr period during which they experience equal amounts of extension, but with the multi-phase experiment experiencing fault topography inherited from a previous phase of extension. Our results demonstrate a very dynamic evolution of the drainage network that occurs in response to fault growth and linkage and to depocentre overfilling and overspilling. We observe profound differences between topographic and depocenter development during single and multi-phase rifting with implications for sedimentary facies architecture. Our quantitative approach, enables us to better understand the impact of changing extension direction on the distribution of sediment source areas and the syn-rift stratigraphic development through time and space.publishedVersio

Drainage integration and sediment dispersal in active continental rifts: A numerical modelling study of the central Italian Apennines

Progressive integration of drainage networks during active crustal extension is observed in continental areas around the globe. This phenomenon is often explained in terms of headward erosion, controlled by the distance to an external base‐level (e.g. the coast). However, conclusive field evidence for the mechanism(s) driving integration is commonly absent as drainage integration events are generally followed by strong erosion. Based on a numerical modelling study of the actively extending central Italian Apennines, we show that overspill mechanisms (basin overfilling and lake overspill) are more likely mechanisms for driving drainage integration in extensional settings and that the balance between sediment supply vs. accommodation creation in fault‐bounded basins is of key importance. In this area drainage integration is evidenced by lake disappearance since the early Pleistocene and the transition from internal (endorheic) to external drainage, i.e. connected to the coast. Using field observations from the central Apennines, we constrain normal faulting and regional surface uplift within the surface process model CASCADE (Braun & Sambridge, 1997, Basin Research, 9, 27) and demonstrate the phenomenon of drainage integration, showing how it leads to the gradual disappearance of lakes and the transition to an interconnected fluvial transport system over time. Our model results show that, in the central Apennines, the relief generated through both regional uplift and fault‐block uplift produces sufficient sediment to fill the extensional basins, enabling overspill and individual basins to eventually become fluvially connected. We discuss field observations that support our findings and throw new light upon previously published interpretations of landscape evolution in this area. We also evaluate the implications of drainage integration for topographic development, regional sediment dispersal and offshore sediment supply. Finally, we discuss the applicability of our results to other continental rifts (including those where regional uplift is absent) and the importance of drainage integration for transient landscape evolution