Abstract
Drainage networks in continental rifts are generally reported as dynamic features that produce transitions between endorheic and exorheic conditions. While this is of major importance for landscape development, sediment dispersal, and basin stratigraphy, the controls of drainage network evolution across an array of normal fault bounded basins are still not well understood. In this study we use the central Italian Apennines – an area that has been affected by active normal faulting and regional uplift over the last ~3 Myrs – to determine the controls on drainage network evolution and its impact on transient landscape evolution and basin stratigraphy. We compile previously published stratigraphic and fault-related data with new geomorphological constraints for the Aterno River system (~1300 km2), for which a wealth of data has been collected following the destructive L'Aquila earthquake in 2009. We use this compilation to demonstrate how the different basins along the river system were initially isolated during the Early Pleistocene but became fluvially integrated with one another and the Adriatic coast between ca. 1.2 and 0.65 Ma. We conclude that the spatial and temporal pattern of drainage integration is mostly explained by a long-term increase in sediment and water supply relative to basin subsidence due to the Early to Middle Pleistocene climatic transition, the progressive increase in fault-related topography, and the transport of sediment and water down-system as drainage integration occurred. Overall we conclude that rates of sedimentation and basin subsidence in the central Apennines are well-matched, allowing tipping points between over- and under-filled conditions to be easily reached. We also show that consecutive drainage integration events produce discrete waves of river incision and terrace formation, and conclude that drainage integration is of major importance, at least equivalent to tectonics and climate, in controlling transient landscape evolution and rift basin stratigraphy.
Highlights
We have used a surface process model to investigate the phenomenon of drainage integration in the actively extending central Italian Apennines
By using a simple model setup that accounts for the main aspects of tectonic deformation in this area, i.e. regional uplift and normal faulting, we investigated the evolution of drainage integration, the roles of the main controlling mechanisms, and its impact on regionalscale sediment dispersal
These results are consistent with field observations from the central Apennines, in particular the formation of ‘interior gorges’ (Fig. 3.12), and with an increasing number of other studies that call into question headward erosion as being an important process for regional-scale drainage integration
Summary
An often-observed trend is the progressive development of fluvial connections between initially isolated, endorheic, drainage basins and the eventual formation of a regional drainage network (e.g. D’Agostino et al, 2001; Connell et al, 2005; Menges, 2008; Smith, 2013; Dickinson, 2015; Duffy et al, 2015) This phenomenon, so-called drainage integration, explains why lake sediments often characterise older parts of the stratigraphy of fault-bounded extensional basins, while fluvial sediments are observed higher up in the record (e.g. D’Agostino et al, 2001; Connell et al, 2005; Cavinato & De Celles, 1999; Miccadei et al, 2002). The work presented in this thesis provides a number of new insights into the landscape evolution in the central Apennines, in particular related to the dynamic development of the drainage network (sections 6.2 and 6.3) and mantle-induced fault development and surface uplift (section 6.4)
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