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

Abstract

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. ---Basin Research. 2018;30:965-989. wileyonlinelibrary.com/journal/bre | 965 Highlights • Landscape evolution modelling study applied to the actively extending central Italian Apennines • Transient landscape development even if tectonic and climatic forcing in the model are uniform over time • Faulting and regional uplift explain drainage integration, i.e. the transition from internal to external drainage • Drainage integration is driven by "top-down" overspill mechanisms rather than "bottom-up" headward erosion • Drainage integration causes abrupt local changes in erosion/deposition and delayed sediment export offshore 966 | EAGE GEURTS ET AL. F I G U R E 1 (a) Location map of the study area in the central Apennines, (b) the study area and model domain itself (DEM from Tarquini et al., 2007) and (c) a simplified geological map of the area showing the main lithological units (modified from Whi...

New stratigraphic constraints for the Quaternary source‐to‐sink history of the Amatrice Basin (central Apennines, Italy)

“…The alluvial fans and river terraces of the Amatrice Basin are in the upper reach of the Tronto catchment. They are dissected by the present hydrographic network, as a response to the long‐term regional uplift, and are likely unaffected by relative sea‐level changes, since they are located much inland from the Adriatic Sea coastline (see also Coltorti & Farabollini, ; Geurts et al, ; Mancini et al, ).…”

“…Moreover, the thickness of the continental deposits of the Amatrice Basin, never exceeding 60 m, contrasts with the hundreds of metres-thick post-orogenic continental sequences filling most of the Quaternary basins of central Apennines (Bucci, Mirabella, Santangelo, Cardinali, & Guzzetti, 2016;Cavinato, 1993;Cavinato et al, 2002;Mirabella et al, 2018). These basins record a history of Early-Middle Pleistocene continental fluvio-lacustrine environments later incised and/or covered by alluvial fan and fluvial deposits, documenting the end of sedimentation in internally-draining basin environments from the Middle Pleistocene (Geurts et al, 2018). In contrast, the stratigraphy of the Amatrice Basin does not contain lacustrine deposits but it records a history of fluvial and alluvial fan deposition during the Early-Middle Pleistocene, followed by a progressive deepening of the drainage network (i.e., incision of older deposits) and local deposition of younger river terraces.…”

“…The siltstone-dominated lithofacies (LAGp) is up to 300-m-thick. It is composed of well layered, centimetre-to-decimetre thick planar beds of grey to beige siltstone, stacked in decametre-thick bedsets and alternated with bedsets of fine sandstone (logs 2, 4, and 5 in (see also Coltorti & Farabollini, 2008;Geurts et al, 2018;Mancini et al, 2012).…”

“…These extensional intermountain basins commonly correspond to endorheic or semi‐endorheic morphostructural depressions accommodating several cycles of continental sedimentation (e.g., the Rieti Basin: Cavinato, ; the Sulmona Basin: Miccadei, Barberi, & Cavinato, ; the Fucino Basin: Cavinato, Carusi, Dall'Asta, Miccadei, & Piacentini, ; the L'Aquila Basin: Mancini et al, ; Cosentino et al, ; Nocentini et al, ; the Leonessa Basin: Fubelli, Falcucci, Mei, & Dramis, ; Aterno Valley: Pucci et al, , Castelluccio and Norcia basins: Pierantoni, Deiana, & Galdenzi, ; Figure c). Facies characteristics, thicknesses, and depositional environments of the continental deposits represent key markers for shedding light on the interaction between tectonic activity (Aringoli et al, ; Doglioni, D'Agostino, & Mariotti, ; Pucci et al, ), paleoclimate (Giraudi & Giaccio, ), and paleohydrological regimes (Coltorti & Farabollini, ; Geurts et al, ) during the post‐orogenic phase of the central Apennines.…”

Stratigraphic response to spatiotemporally varying tectonic forcing in rifted continental basin: Insight from a coupled tectonic‐stratigraphic numerical model

“…Coupled models can be categorized into either "fully coupled models" or "one-way coupled models." Several works have used coupled approaches to study the evolution of tectonic and surface processes in rift settings (Cowie et al, 2006;Geurts et al, 2018) or orogenic settings (Thieulot, Steer, & Huismans, 2014). Although tectonic models solve for complex nonlinear thermomechanics in fully coupled models, surfaceprocess modelling remains rather simple (e.g., slope-dependent diffusion in Olive, Behn, & Malatesta, 2014).…”