Formation of Longitudinal River Valleys and the Fixing of Drainage Divides in Response to Exhumation of Crystalline Basement

Bernard, Thomas; Sinclair, H. Q.; Gailleton, Boris; Fox, Matthew

doi:10.1029/2020gl092210

Cited by 15 publications

(16 citation statements)

References 40 publications

(61 reference statements)

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“…rocks are the most resistant units near the base level of the northern Amazon River tributaries, coincident with the ME (Figure 4b). The low‐relief zones observed immediately upstream of the ME in the Guiana Shield are thus consistent with low‐relief zones upstream of exhumed hard rocks (Bernard et al, 2021) and/or upstream of uplifted zones (i.e. base‐level rise; e.g.…”

Section: Discussionsupporting

confidence: 78%

“…The mechanism of river reorganization described here is not exclusive of cratonic settings and may well affect other regions of the world with high contrasts in rock erodibility (e.g. Bernard et al, 2021; Gallen, 2018). We maintain that landscapes in intraplate settings (i.e.…”

Section: Discussionmentioning

confidence: 85%

“…Forte et al, 2016) while passively uplifting the areas upstream of the soft rock–hard rock contact and forming a local base level (e.g. Bernard et al, 2021). This process is similar to the differential uplift of a downstream zone which generates flattening of river profiles upstream of the uplifted zone due to base‐level rise (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…Importantly, the localized exhumation of resistant rocks can lead to differential knickpoint migration rates and response times among neighbouring basins responding to the same change in base level (Forte et al, 2016; Harbor et al, 2005; Perne et al, 2017; Wolpert & Forte, 2021). Under such scenarios, lithological complexity may trigger the migration of drainage divides and river reorganization in adjacent basins that otherwise would not change shape (Bernard et al, 2021; Zondervan et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

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Ongoing landscape transience in the eastern Amazon Craton consistent with lithologic control of base level

Fadul

Oliveira

Val

2022

Earth Surf Processes Landf

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Geomorphic features such as drainage captures, knickpoints, paleochannels, and wind-gaps have long been observed in the Amazon region and typically thought to result from climate change and intraplate tectonics. The influence of rock type as a trigger of these landscape transients is largely overlooked. In the eastern Guiana Shield of the Amazon Craton, shield rivers flow over to the sedimentary rocks of the Amazon Basin across a sharp lithologic transition before their confluence with the Amazon River. This transition is marked by an expressive main escarpment (ME) formed over resistant sandstones of the basal units of the Amazon Sedimentary Basin. Here, systematic patterns of divide migration and river captures provide a natural laboratory to study the influence of rock type in landscape transience in a cratonic setting. Through quantitative geomorphologic analysis of the topography, drainage divides, and rivers, we investigate if this sharp lithologic transition contributed to the observed patterns of drainage rearrangement. The results revealed that rivers of larger drainage areas flowing across shorter lengths over the resistant rocks of the ME systematically capture neighbouring basins. We argue that, as tributaries draining the shield respond to downcutting and/or base-level fall of the Amazon River, bedrock incision and knickpoint propagation are differentially slowed down by the resistant rocks according to their incision capacity, generating a series of transients such as drainage capture and divide migration. The widespread and systematic geomorphic features suggest this mechanism could be an important autogenic control of drainage network rearrangement in the Amazon region and other postorogenic landscapes as well. The protracted exhumation of resistant rocks in cratons and intraplate settings may keep landscapes in perpetual disequilibrium depending on their lithological complexity and offer an exceptional natural laboratory to study landscape dynamics associated with rock type.

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Section: Discussionsupporting

confidence: 78%

Section: Discussionmentioning

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ongoing landscape transience in the eastern Amazon Craton consistent with lithologic control of base level

Fadul

Oliveira

Val

2022

Earth Surf Processes Landf

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“…Admittedly, a recent research contribution documented that the Alps reached a high topography during Miocene times [115] particularly in the hangingwall area of the Simplon fault (Figure 2). However, these high elevations were possibly local in nature [115] and could have reflected a transient state in the rearrangement of the Alpine drainage network, which started at c. 20 Ma [116][117][118]. In addition, at the same time, tectonic exhumation in the Lepontine area through slip along the Simplon fault (Figure 2) reached a peak shortly after 20 Ma [119], which would correspond to a phase of surface unloading in the orogen.…”

Section: Possible Controls Of Surface and Basin Fill Loads On The Dev...mentioning

confidence: 99%

Slab Load Controls Beneath the Alps on the Source-to-Sink Sedimentary Pathways in the Molasse Basin

Schlunegger

Kissling

2022

Geosciences

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The stratigraphic development of foreland basins has mainly been related to surface loading in the adjacent orogens, whereas the control of slab loads on these basins has received much less attention. This has also been the case for interpreting the relationships between the Oligocene to Micoene evolution of the European Alps and the North Alpine foreland basin or Molasse basin. In this trough, periods of rapid subsidence have generally been considered as a response to the growth of the Alpine topography, and thus to the construction of larger surface loads. However, such views conflict with observations where the surface growth in the Alps has been partly decoupled from the subsidence history in the basin. In addition, surface loads alone are not capable of explaining the contrasts in the stratigraphic development particularly between its central and eastern portions. Here, we present an alternative view on the evolution of the Molasse basin. We focus on the time interval between c. 30 and 15 Ma and relate the basin-scale development of this trough to the subduction processes, and thus to the development of slab loads beneath the European Alps. At 30 Ma, the western and central portions of this basin experienced a change from deep marine underfilled (Flysch stage) to overfilled terrestrial conditions (Molasse stage). During this time, however, a deep marine Flysch-type environment prevailed in the eastern part of the basin. This was also the final sedimentary sink as sediment was routed along the topographic axis from the western/central to the eastern part of this trough. We interpret the change from basin underfill to overfill in the western and central basin as a response to oceanic lithosphere slab-breakoff beneath the Central and Western Alps. This is considered to have resulted in a growth of the Alpine topography in these portions of the Alps, an increase in surface erosion and an augmentation in sediment supply to the basin, and thus in the observed change from basin underfill to overfill. In the eastern part of the basin, however, underfilled Flysch-type conditions prevailed until 20 Ma, and subsidence rates were higher than in the western and central parts. We interpret that high subsidence rates in the eastern Molasse occurred in response to slab loads beneath the Eastern Alps, where the subducted oceanic slab remained attached to the European plate and downwarped the plate in the East. Accordingly, in the central and western parts, the growth of the Alpine topography, the increase in sediment flux and the change from basin underfill to overfill most likely reflect the response to slab delamination beneath the Central Alps. In contrast, in the eastern part, the possibly subdued topography in the Eastern Alps, the low sediment flux and the maintenance of a deep marine Flysch-type basin records a situation where the oceanic slab was still attached to the European plate. The situation changed at 20 Ma, when the eastern part of the basin chronicled a change from deep marine (underfilled) to shallow marine and then terrestrial (overfilled conditions). During the same time, subsidence rates in the eastern basin decreased, deformation at the Alpine front came to a halt and sediment supply to the basin increased possibly in response to a growth of the topography in the Eastern Alps. This was also the time when the sediment routing in the basin axis changed from an east-directed sediment dispersal prior to 20 Ma, to a west-oriented sediment transport thereafter and thus to the opposite direction. We relate these changes to the occurrence of oceanic slab breakoff beneath the Eastern Alps, which most likely resulted in a rebound of the plate, a growth of the topography in the Eastern Alps and a larger sediment flux to the eastern portion of the basin. Beneath the Central and Western Alps, however, the continental lithosphere slab remained attached to the European plate, thereby resulting in a continued downwarping of the plate in its central and western portions. This plate downwarping beneath the central and western Molasse together with the rebound of the foreland plate in the East possibly explains the inversion of the drainage direction. We thus propose that slab loads beneath the Alps were presumably the most important drivers for the development of the Molasse basin at the basin scale.

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Identifying geomorphic domains using hierarchically clustered drainage area‐slope scaling

Wang

2024

Earth Surf Processes Landf

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Area‐slope scaling is an important tool for analysing geomorphic processes. In this study, we used hierarchical clustering to sort the area‐slope scaling data for both the numerical landscape created using the LandLab model and real landscapes. Random forest analysis was used to explore the effect of hierarchical clustering. We aimed to illustrate the heterogeneous features of area‐slope clustering and their influencing factors and to test whether they can be used to distinguish geomorphic domains. Our results showed that hierarchical clustering can easily detect the heterogeneous features of area‐slope scaling constrained by tectonic uplift and fluvial erodibility but not those constrained by the diffusion coefficient. The slope gradients over the inflection/transition zone of the colluvial and fluvial domains play a key role in identifying area‐slope scaling from different geomorphic domains. Case studies show that area‐slope scaling of clusters would be affected by different lithology and distance away from the trunk channel. In the high erosion circumstance, the fluvial process caused by tectonics leads to increasing slope gradients over whole geomorphic domains, as well as to retreating inflection between the colluvial and fluvial process domains. In low erosion circumstances or steady state, the fluvial process caused by nearby rivers cannot effectively change the slope gradients but can retreat the inflection. The real landscapes suggest that basins should be carefully selected for area‐slope scaling analysis to ensure that they are representative of the entire study area. Before geomorphological research, more basins of a specific research region need to be selected to conduct hierarchical clustering to select representative basins. Our study could be helpful in the identification of area‐slope domains, the extraction of geomorphic metrics and geomorphic process research.

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Formation of Longitudinal River Valleys and the Fixing of Drainage Divides in Response to Exhumation of Crystalline Basement

Cited by 15 publications

References 40 publications

Ongoing landscape transience in the eastern Amazon Craton consistent with lithologic control of base level

Ongoing landscape transience in the eastern Amazon Craton consistent with lithologic control of base level

Slab Load Controls Beneath the Alps on the Source-to-Sink Sedimentary Pathways in the Molasse Basin

Identifying geomorphic domains using hierarchically clustered drainage area‐slope scaling

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