•Multidisciplinary approach cross-combined to previous geomorphological maps.•Watercourse are associated to pre-Columbian agricultural structures.•Regressive pattern of the Titicaca Lake coastline ...since mid-20th century.•Major alluvial evolution since mid-20th century.•First synthetized geomorphological and geoarchaeological map of the watershed.
The Altiplano and more specifically the Titicaca circum-lake sector have recorded several major landscape transformations. In particular, changes in the lake water level lead to a significant vulnerability and contributed to the development of flexible and diverse agropastoral activities of the pre-Columbian and current populations to climate change. The Tiwanaku River, particularly because of the presence of the pre-Columbian Tiwanaku site, has been the subject of several research studies aimed at characterizing the environment of the archaeological site. Here we propose a new synthesis of the geomorphology of the Tiwanaku River watershed based on an interdisciplinary approach (Historical geography and remote sensing, cross combined with field survey). Our results show that the general organization of the drainage system is influenced by lake level and climatic changes. However several watercourses of the Tiwanaku River might be related to pre-Columbian agricultural or proto-urban structures. Our work allowed to estimate the regressive pattern of the coastline of Lake Titicaca and to identify major changes of the terminal and medium watercourse of the Tiwanaku River over the last 70 years.
Fold geometries and kinematics within foreland basins is a major issue for understanding the late evolution of thrust fronts. In the foreland of the southwestern Alps, the Vélodrome complex fold ...involves the whole Tertiary series which have recorded the evolution of the alpine front. From a geometrical and kinematic point of view, the Vélodrome is classically described as a recumbent Mio-Pliocene syncline with a strongly curved axis; interpreted either as a classic growth-fold, a post-deposit fold, or a result of coeval salt activity. The debate reveals a lack of consensus on the internal structure of the Vélodrome and the potential role of salt motion. By a detailed field analysis coupled with an implicit 3D geometrical modelling approach, we test the different hypotheses and provide a new 3D illustrated interpretation of the Vélodrome series. The Vélodrome consists in a complex non-cylindrical structure composed by several folds with different orientations together with inter- and intra-formations unconformities. Folding is partly syn-depositional and began earlier in the south, near Esclangon village, than in the north. In the north, deformation started with the marly and sandy molasse (m2, middle Burdigalian), attested by the transition from the conformable conglomeratic marine molasse (m1–2, Aquitanian and early Burdigalian) to the unconformable m2 to the Valensole formation. Deformation began earlier in the south, during the deposition of the m1–2, as shown by internal unconformities. We discuss the ingredients controlling the deformation in the Vélodrome, regional tectonics (mainly since middle Burdigalian) versus salt tectonics. This study further brings new constraints on the timing and pattern of deformation of the southwestern orogenic front of the Alps. It also highlights the power of the 3D geometrical modelling approach for testing different hypotheses and better understanding 3D complex structures.
Reconstructing long-term drainage evolution in collisional setting is key to deciphering between the drivers controlling landscape and time scales of syn-orogenic sediment transfer processes. ...Provenance studies in orogenic systems often exploit the geochronological record of past magmatic events in sediments to infer their source rocks. However, detrital age distribution may be difficult to be directly related to a specific source rock because it depends on whole rock composition and a robust stratigraphic and sedimentologic framework. Description of the provenance signal over the orogenic cycle from rift basin to its inversion as an orogenic prism may therefore appear to be a very challenging task. Here, we take advantage of an extensive set of geochronological dates in combination with sedimentological data in well-dated stratigraphic units to resolve uncertainties on grain provenance.
We focus on the Pyrenees Mountains that developed in response to the inversion of European and Iberian continental margins from the Late Cretaceous to the Miocene. Inversion of hyper-extended rift basins in the Northern Pyrenees is recorded by specific cooling histories contrasting with the Southern Pyrenees where crustal extension was minor.
We review and compile all available detrital thermochronological and geochronological data sets and provide new U/Pb and (U-Th-Sm)/He analyses on detrital zircon grains. This new data set allows us to re-examine the evolution of the sediments routing in the Pyrenees from rift-related Mesozoic basin evolution to tectonic inversion during Cenozoic foreland development. Together with sedimentological and petrographical constraints from syn-rift Mesozoic and syn-orogenic Cenozoic sediments, and within the frame of quantitative kinematic plate reconstructions based on existing rotation data, and balanced cross-sections, we examine the temporal and spatial evolution of sediment routing in the entire Pyrenean realm from rift to collision. Our paleogeographic reconstructions of the sediment dispersal pattern are presented for four key time steps at ~100, 70, 55, and 40Ma, accounting for Iberia's plate motion.
Early Cretaceous extension on the European margin led to the formation of multiple and narrow basins that were fed locally. This contrasts with the larger-scale pattern of sediment dispersal on the southern Iberia margin. The differences in sediments dispersal are shown to reflect first-order N-S asymmetry of extension. The asymmetry is maintained during the earliest stages of convergence in Late-Cretaceous – Paleocene. The southern foreland basin exhibits large-scale longitudinal drainage patterns while sediments dispersal in the northern basin is controlled by inherited pre-orogenic E-W-striking basin architecture. In the Paleocene, the southwards migration of thrust sheets and underplating below the Axial Zone led to increasing exhumation at the origin of the emplacement of the first transverse drainage network in the Southern Pyrenees. Changes from dominant longitudinal to transverse drainage in the north occurred in the middle Eocene.
Our study emphasizes the role played by the rifted margin on the syn-collisional sediment routing system. We anticipate that this main result could be transposed to other orogens that have resulted from rift basin inversion.
Wave train model for knickpoint migration Loget, Nicolas; Van Den Driessche, Jean
Geomorphology (Amsterdam, Netherlands),
05/2009, Letnik:
106, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Rivers respond to a drop in their base level by incising the topography. The upstream propagation of an incision, as usually depicted by a knickpoint migration, is thought to depend on several ...parameters such as the drainage area, lithology, and the amplitude of the base level drop. We first investigate the case of the Messinian Salinity Crisis that was characterized by the extreme base level fall (1500 m) of the Mediterranean Sea at the end of the Miocene. The response of drainage areas of three orders of magnitude (10
3 to 10
6 km
2) highlights the dominant role of the drainage area (with a square root relationship) in controlling the knickpoint migration after a base level fall. A compilation of mean rates of knickpoint propagation for time durations ranging from 10
2 to 10
7 years displays a similar relationship indicating that successive wave trains of knickpoint can migrate in a river: first, wave trains linked to the release of the alluvial cover and then, wave trains related to the bedrock incision, which correspond to the real time response of rivers. Wave trains with very low retreat rates (long lived knickpoints >
1 My) rather correspond to the response time of regional landscape.
The oblique collision of Taiwan orogen led to a progressive southward uplift and emergence of a submarine accretionary wedge. The Hengchun Peninsula located at the southernmost tip of Taiwan island ...represents the most recently emerged landform of an antecedent submarine surface. In this study we examine the geomorphic evolution of this newly emerged and uplifted landscape. The extraction of geomorphic parameters (knickpoint distribution, steepness index of rivers) indicates a transient nature of the landscape but shows that a simple model of regressive erosion consecutive to sudden uplift is unsatisfactory. Knickpoint migration modeling shows that only the upstream Sizhong basin can be explained by this single process. On the other hand, the occurrence of a relict landscape (Mutan Ponds low relief) developed at low elevations and, today uplifted in the core of the peninsula, has strongly influenced the drainage evolution. Numerous knickpoints are linked to capture processes around the Mutan Ponds area, indicating a dynamic reorganization of the drainage system. We propose that the landscape of the Hengchun Peninsula is in a transient stage and results from a combination between rejuvenation and drainage rearrangement caused by the late stage of emergence of the south of Taiwan.
•Transient nature of emerging topography exhibits dynamic landscape reorganization.•We examined the geomorphic evolution of an emerged in the southernmost Taiwan.•Low-relief terrains built of lacustrine deposits reveal relict landscapes.•The relict landscape has strongly influenced the drainage evolution.•Drainage system is affected by numerous capture points.
The axial fault-bounded depression of the South Kenya rift (SKR) locally displays anomalously wide sectors resulting from the presence of one (or many) elevated and offset block(s) on the flanks of ...the main trough. Very little attention has been paid so far to the nature of the driving mechanisms responsible for these atypical rift patterns. New insights are supplied by the Natron-Ol Doinyo Ogol rift segment at the southern extremity of the SKR, immediately north of the North Tanzanian Divergence (NTD). On the basis of interpreted SRTM-30 satellite imagery and Digital Elevation Models, our work allows us: i) to depict the highly-segmented arrangement of the ~7 Ma-lasted SKR system, ii) to establish a two-stage kinematic rift model that emphasizes the role of an inherited transverse discontinuity on the arrest, as well as lateral jump and off-axis development of anomalously-propagating rift structures, iii) to define the relative contribution of border vs inner fault networks to the total extension, which is estimated at 7–6 km (11.6–9.2%), and iv) to emphasize that inner faulting was not the dominant mode of strain accommodation during recent inward focussing of strain, and that no sharp transition exists from border fault- to intra-rift fault-dominated strain accommodation over time in the SKR immature rift system.
•The quantitative analysis of normal faults in the South Kenya rift indicates a cumulative extension estimated at 7–6 km (11.6–9.2%) during the last 7 Myrs.•Border fault activity persists during the 7 Myrs rift evolution, and young inner faulting is not the prominent mode of strain accommodation.•Tectono-magmatic disturbances in the North Tanzanian Divergence are controlled by a reactivated transverse Archaean discontinuity.
The Betics are a key area to study an orogenic landscape disrupted by late‐orogenic extension. New low‐temperature thermochronology (LTT) data (AHe and AFT) coupled with geomorphic constraints in the ...Sierra de Gador (Alpujarride complex) are used to reconstruct the cooling history and evolution of relief during the Neogene. We document three stages: (1) a fast cooling event between 23 and 16 Ma associated with the well‐known extensive tectonic exhumation of the Alpujarride unit, (2) a period of slow cooling between 16 and 7.2 Ma related to a planation event and (3) a post‐7.2 Ma surface uplift associated with the inversion of the Alboran domain undetected by LTT. The planation event followed by this late uplift can explain the occurrence of inherited low‐relief surfaces overlain by Tortonian–Messinian platform deposits at the top of the range. Finally, we propose that the Sierra de Gador is a more transient landscape than the nearby Sierra Nevada.
The growth of relief in active tectonic areas is mainly controlled by the interactions between tectonics and surface processes (erosion and sedimentation). The study of long-lived morphologic markers ...formed by these interactions can help in quantifying the competing effects of tectonics, erosion and sedimentation. In regions experiencing active extension, river-long profiles and faceted spurs (triangular facets) can help in understanding the development of mountainous topography along normal fault scarps. In this study, we developed analogue experiments that simulate the morphologic evolution of a mountain range bounded by a normal fault. This paper focuses on the effect of the fault slip rate on the morphologic evolution of the footwall by performing three analogue experiments with different fault slip rates under a constant rainfall rate. A morphometric analysis of the modelled catchments allows comparing with a natural case (Tunka half-graben, Siberia). After a certain amount of fault slip, the modelled footwall topographies of our models reaches a dynamic equilibrium (i.e., erosion balances tectonic uplift relative to the base level) close to the fault, whereas the topography farther from the fault is still being dissected due to regressive erosion. We show that the rates of vertical erosion in the area where dynamic equilibrium is reached and the rate of regressive erosion are linearly correlated with the fault throw rate. Facet morphology seems to depend on the fault slip rate except for the fastest experiment where faceted spurs are degraded due to mass wasting. A stream-power law is computed for the area wherein rivers reach a topographic equilibrium. We show that the erosional capacity of the system depends on the fault slip rate. Finally, our results demonstrate the possibility of preserving convex river-long profiles on the long-term under steady external (tectonic uplift and rainfall) conditions.
► New experimental models allow to study relief evolution along active normal faults. ► A quantitative analysis from DEMs of the models is performed. ► We succeed in developing the main morphological features of the normal faults. ► The fault slip rate controls the erosion rate in rivers and on the hillslopes. ► We also evidence the possibility of maintaining long-term convex river-long profiles.
An understanding of the evolution of foreland basins improves our knowledge of how mountain belts have grown and helps us to decipher events which may not be preserved in the orogen. The infilling of ...the north Pyrenean retro‐foreland basin (Aquitaine Basin, France) during the main exhumation of the Pyrenees and its corresponding thermal history have not been fully investigated. We applied apatite fission track (AFT) and (U‐Th‐Sm)/He (AHe) methods coupled with inverse thermal modelling on both the detrital Eocene (47 to 33 Ma) syn‐orogenic Palassou conglomerates of the eastern part of the Aquitaine Basin and basement samples from the North Pyrenean Zone and the Axial Zone of the Pyrenees. Apatite crystals were separated from granitic cobbles found in the conglomerates. AFT ages for detrital samples range from 27 ± 2 to 43 ± 4 Ma, and AHe ages from 13 ± 1 to 76 ± 5 Ma. For in situ massifs AFT ages range from 35 ± 2 to 90 ± 17 Ma and AHe ages from 39 ± 2 and 80 ± 5 Ma. AFT ages for detrital samples are close to deposition ages, whereas AHe ages are older and younger than deposition ages and show a partial thermal resetting due to burial. A detailed analysis of the ages obtained and thermal histories derived from modelling shows that ages reflect (a) exhumation from 70 to 55 Ma revealed by a long stay in the partial retention zone (PRZ), (b) a Palaeocene–Eocene cooling in the Pyrenees, (c) a post‐depositional episode of moderate heating of the sediments in the basin represented by partially reset young AHe and AFT ages compared to deposition ages and (d) an early to mid‐Miocene final exhumation of the basin deposits as evidenced by young AHe ages and geological constrains. These results reflect a common event with the south Pyrenean foreland basin that is characterized by high piedmont aggradation from the late Eocene to the Miocene. The aggradation of sediments is possibly connected with well‐known high elevation low relief surfaces in the core of the Pyrenees and followed by a Miocene exhumation event that is already observed on the southern flank. However, the timing of the aggradation and exhumation events could be different between the north and the south. Erosion occurred most probably during the early to mid‐Miocene in the north and during the late Miocene–early Pliocene in the south.
This paper provides new detrital low temperature thermochronology data from the eastern part of the Aquitaine Basin (the Corbières region). Thermal modelling of the obtained results allowed the determination of the thermal history of the samples from their source (the Pyrenees) to the basin (the Corbières region).
Most interpretations of the Early Pliocene opening of the Strait of Gibraltar involve a tectonic process. However, no tectonic structure of this age has been unequivocally documented that could ...account for such a hypothesis. On the other hand, the sea-level drop of the Mediterranean during the Messinian Salinity Crisis has dramatically enhanced continental erosion and in particular regressive fluvial erosion. We show that such erosional process inevitably developed in the Gibraltar area. We finally propose that regressive fluvial erosion was at the origin of the opening of the Strait of Gibraltar.
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