Landscape Rejuvenation Research Articles

Drainage capture driving landscape rejuvenation in a tectonic quiescent setting: A case of study in the southern sector of the Sierra Madre Oriental (Eastern Mexico)

Drainage captures increase the stream discharge and the potential ability of rivers to incise. In quiescent tectonic settings, drainage captures are rapid geomorphic processes that can trigger landscape rejuvenation. We study a drainage capture that renewed the incision of the Moctezuma River, which flows along a mountainous flank of the southern sector of the Sierra Madre Oriental (SMO). The subsequent baselevel drop along the Moctezuma River steepened its adjacent tributaries and generated the migration upstream of knickpoints. We elucidated the resultant pattern of landscape rejuvenation along the Moctezuma River by performing different hillslope and channel metrics. We also identified and analyzed the knickpoints to confirm their origin by one incision pulse migrating upstream from the Moctezuma River. Using the stream power-based celerity model on knickpoints, we estimated that the landscape rejuvenation due to drainage capture initiated ∼0.27 Ma ago with a migration rate of ∼1 mm yr −1. Our results confirm that drainage capture is an important mechanism that produces meaningful and complex landscape modifications likewise those produced by the tectonic activity.

REMOTE SENSING OF URBAN DEVELOPMENT AND ENVIRONMENTAL LANDSCAPE: A STUDY OF GREEN COVER LUNGS OF DELHI AND SURROUNDING CITY REGIONS

Abstract. The remote sensing satellites have now a days been used for creation of geospatial databases of the earth surface features and natural resources as the land use land cover mapping and monitoring periodically at the local, regional, and global levels using geospatial technologies. The Land cover consider to the type of features present on the surface of the earth. Whereas, the land use considers to the human activity or the economic function associated with a specific piece of land. The supervised classification based on the maximum likelihood classifier technique has been applied to process the digital multi-spectral imagery for LULC classification. The built-up area was about 11.95 per cent in 1977 which increased to 19.74 per cent in 1999 and further increased to about 24.54 per cent in 2009. So, the urban landscape’s urban built-up land was composed by areas of intensive use with much of land covered by built-up structures. The cities, towns, villages, strip development along highways; transportation, power, and communication facilities; shopping centres, industrial and commercial complexes, and institutions found located in the urban areas have been developed over the periods. The forests cover area accounted to about 1.43 per cent in 1977 which increased to about 10.04 per cent in 1999. The forest cover regeneration over the Delhi Ridge recognized as a significant contributor to carbon sequestration, micro-climate change, biodiversity restoration for the Delhi’s urban development and rejuvenation of environmental landscape. So, the remote sensing imagery have commonly been used for urban landscape monitoring and environmental modelling for sustainable development of Delhi and adjoining city regions.

Late Neogene terrestrial climate reconstruction of the central Namib Desert derived by the combination of U–Pb silcrete and terrestrial cosmogenic nuclide exposure dating

Abstract. The chronology of the Cenozoic “Namib Group” of the Namib Desert is rather poorly understood and lacks direct radiometric dating. Thus, the paleoclimate and landscape evolution of the central Namib Desert remains imprecise, complicating the detailed search for global and/or local forcing factors for the aridification of the Namib. The widespread occurrence of calcretes and silcretes in the Namib Desert allows us to apply the novel application of the U–Pb laser ablation dating technique on silcretes and calcretes to date important phases of landscape stability and to retrieve critical paleoclimatic and environmental information on desertification and its paleoclimatic variability. Microscale silcrete formation (maximum of 8 mm) due to pressure solution by expanding calcrete cementation provides the opportunity to date multiple phases (multiple generations of silcrete as growing layers or shells) of silcrete formation. Groundwater silcrete and calcrete formation occurred at our study site during the Pliocene, a period of relatively stable climate and landscape conditions under semi-arid to arid conditions. Terrestrial cosmogenic nuclide (TCN) exposure ages from flat canyon rim surfaces indicate the cessation of groundwater calcrete formation due to incision during the Late Pliocene–Early Pleistocene and mark a large-scale landscape rejuvenation due to climate shifts towards more arid conditions in the Pleistocene, which can be connected to global climate patterns. This study demonstrates the feasibility of applying U–Pb laser ablation to groundwater silcrete and calcretes, discusses several important issues associated with this technique, and opens up the possibility of dating numerous sedimentary sequences containing silcretes and calcretes in arid environments. In particular, the use of silcretes (as described above) reduces potential effects of detrital components and bulk signal measurements by using massive calcretes. Our study redefines and improves the generally accepted Late Cenozoic chronostratigraphy of the Namib Desert (Miller, 2008).

Heinrich events and tectonic uplift as possible drivers for late Quaternary fluvial dynamics in the western Peruvian Andes

Late Quaternary fluvial valley development in Peru is considered to be driven by summer insolation maxima in the precession cycle, which coincide with increased precipitation and rising lake levels in the central Andes. Our literature review, however, indicates that fluvial aggradation does not always coincide with summer insolation maxima but may also occur during transitions between insolation maxima and minima or even during summer insolation minima. Tectonic uplift as a driver of fluvial incision has not been considered in the current terrace formation models, despite the Peruvian margin being located above an active subduction zone. We present new chronologic, stratigraphic and geomorphic data of the Cañete River valley over the past 102 ± 6 ka. We mapped its fluvial terraces (11.5°-13° southern latitude) along a 75-km long reach perpendicular to the strike of the Andes. Five fluvial terraces and one floodplain level were identified with relative elevations of up to 181.1 m above the floodplain. Thirty-three (pIR) IRSL ages of eight fluvial terraces and one alluvial fan sediment sample showed that their ages in part correspond to summer insolation maxima of the precession cycle, but that a better match exists with pluvial periods that coincided with Heinrich events of the northern hemisphere and rising lake levels in the Andes. The chronology of terraces of the Cañete River agrees with those of previously studied fluvial systems between 7° and 16° southern latitude in Peru, suggesting a regional-scale fluvial response possibly to the Heinrich events. Reconstructed longitudinal profiles and terrace ages were utilised to calculate vertical incision rates. We calculated a mean rate of 1.8 ± 0.10 mm a −1 over the last 102 ± 6 ka, but incision rates varied considerably within this time period possibly in response to changes in the Qs: Qw ratio as a consequence of increased sediment input during the wet Heinrich events. A set of 1338 GNSS measurements of daily, vertical crustal deformation of the years 2009–2015 showed a continuous and positive trend in interseismic, accumulative vertical crustal movements with a time-averaged, crustal uplift rate of 1.9 ± 3.6 mm a −1 . The positive trend in vertical movements, together with data from literature suggest landscape rejuvenation along the forearc and western Cordillera in central Peru. It is proposed that maximally ∼0.5 mm a −1 of the total incision over the past 102 ka may possibly be related to nonrecoverable, interseismic deformation. Climate change-driven variations in the Qs : Qw ratio are superimposed on the long-term tectonic uplift trend, and both are considered the main drivers of fluvial incision. • Fluvial aggradation in response to wet Heinrich events. • Very rapid incision of 1.8 ± 0.1 mm a −1 since 102 ± 6 ka until the present. • GNSS measurements reveal crustal uplift rate of 1.9 ± 3.6 mm a −1 . • Crustal uplift main driver for fluvial incision and climate change as secondary driver. • The same pattern of aggradation and incision occurred along entire western Peru.

Landslides and Gullies Interact as Sources of Lake Sediments in a Rifting Context: Insights from a Highly Degraded Mountain Environment

Like many other lakes in the world, the interconnected Abaya and Chamo lakes in the Southern Main Ethiopian Rift are affected by rapid sediment accumulation. Although land degradation is a well-known issue in this part of the African continent, the main sediment sources, their spatial distribution and interaction in the Abaya–Chamo lakes’ basin have not yet been documented. Here, we present a systematic inventory, characterization, and spatial analysis of landslides and gullies as concentrated sediment sources, for four representative river catchments impacted by landscape rejuvenation. Using Google Earth imagery and field surveys, we mapped with high accuracy a total of 7336 gullies and 430 landslides. Recent landslides observed during the last decade were few, small and shallow, and appear to have played a minor role in the current sediment dynamics. Large landslides are old and inactive. Although they do not contribute to the current sediment budget, they contribute indirectly to landscape dynamics by favoring the occurrence of gullies. Overall, large percentages of severe to extremely degraded areas of gully erosion are located in rejuvenated landscapes, especially at the level of the old landslides. Many active gullies are connected to the river network, as such acting as the source of sediment. Our analysis is a step towards understanding the nature and control of anthropic activities on sediment production in the region. We also highlight the importance of considering the interactions between sediment sources and the connectivity of the geomorphological system.

Traditional Rainwater Management (Haveli cultivation) for Building System Level Resilience in a Fragile Ecosystem of Bundelkhand Region, Central India

This article presents the evidence on how the traditional rainwater management system (haveli system) has contributed toward rehabilitating degraded landscapes and changing them into a productive form in Bundelkhand region of Central India. The haveli system was the lifeline of the region for water security for the last 300 years. Farmers (~1–5%) situated at the upstream of the landscape were harvesting surface runoff in their fields during monsoon by constructing earthen embankments along with provision to drain out water after receding of the monsoon. Farmers traditionally cultivated only during the post-monsoon period, using residual soil moisture along with supplemental irrigation from shallow dug wells. However, this system became defunct due to apathy and poor maintenance. The traditional design of the havelis were also often malfunctioning due to new rainfall patterns and storm events. Farmers are facing new need for haveli rejuvenation and the traditional design and knowledge calls for new innovations, particularly from research and external expertise. In this context, ICRISAT and consortium partners have introduced an innovative approach for haveli rejuvenation by constructing masonry core wall along with outlet at a suitable location. Totally 40 haveli structures were constructed between 2010 and 2021 across seven districts of Bundelkhand region. One of the pilot sites (i.e., Parasai-Sindh) was intensively monitored in order to capture the landscape hydrology, change in land use, cropping intensity and crop productivity, between 2011 and 2017. Out of 750 mm rainfall received during July and September, generated surface runoff is about 135 mm (18% of rainfall) on average. However, rainfall below 450 mm (dry years) rarely generates surplus water as most of the rainfall received in such years are absorbed within the vadose zone, whereas, wet years with over 900 mm rainfall, generate runoff of about 250–300 mm (~30–35%). Rejuvenation of the haveli system created an opportunity to harvest surface runoff within farmers' fields which helped to improve groundwater levels in shallow dug wells (additionally by 2–5 m hydraulic head) which remained available during the following years. This has increased cropping intensity—by converting about 20% of permanent fallow lands into productive agriculture lands—and ensured irrigation availability especially during the critical crop growth stage. This enhanced land and water use efficiency of the system and increased household net income by two to three folds as compared to the baseline status. This article further establishes the link between landscape rejuvenation through haveli system, groundwater resource availability, production system and household income in the fragile ecosystem of Central India. The results are helpful for various stakeholders so that they can take informed decisions on sustainable natural resource management.

Timing of river capture in major Yangtze River tributaries: Insights from sediment provenance and morphometric indices

The eastern margin of the Tibetan Plateau represents one of the morphologically most active regions on Earth, where the interplay of recent crustal deformation and subsequent fluvial landscape adjustment has affected the course of continental-scale rivers by river piracy events. Based solely on field observations, such an event has been hypothesised for two of the largest tributaries of the Yangtze River: the Jialing and Hanjiang Rivers. To test this hypothesis, we employ a novel combination of independent methods including a provenance study based on age distributions of detrital zircons from both modern riverbeds and river terraces and a morphometric analysis of river channels and drainage divides. We supported the morphometric analysis with a time-dependent numerical model describing the evolution of river channel long profiles and drainage divides in a succession of river capture events. Analysed zircon ages show clearly distinguishable distributions for the modern Jialing and Hanjiang Rivers, but similar distributions for the recent Hanjiang River up to its topmost terraces. This suggests that the capture of the Hanjiang headwaters by the Jialing River is unlikely to have taken place during the last 1.2 million years. However, several knickpoints in the main stem and the tributaries of the Jialing River cluster at an elevation of about 900 m and separate steeper (downstream) from less steep channel segments (upstream), which is consistent with the morphological expression of a major capture event. χ mapping indicates drainage divide asymmetry at catchment scale with on average steeper rivers on the Jialing side, whereas Gilbert metrics show a symmetric divide at hillslope scale. This numerical model explains this apparent contradiction by the travel time of capture-related knickpoints from the capture point towards the watershed, where χ mapping indicates divide asymmetry immediately after the river capture, while Gilbert metrics are only affected as soon as the knickpoints reach the channel heads and the divide effectively starts moving. Based on knickpoint travel distances and constraints on regional incision / uplift rates, we estimate the possible date of river capture to be the Pliocene. This is earlier than the formation of the terraces investigated in the provenance study but recent enough that most of the drainage divides are still unaffected and currently almost stable. Only the wind gap located in the almost dry valley connecting the two competing drainage systems is likely to have shifted towards the Hanjiang side. We suggest that this resulted in the capture of another important tributary of the Hanjiang River (the Heishui River) by the Jialing drainage system. Our results illustrate the complex evolution of drainage networks along the eastern margin of the Tibetan Plateau, and highlight the importance for combining provenance and morphometric analyses in regions of active landscape rejuvenation where river captures are likely to occur.

Climate or tectonics? What controls the spatial-temporal variations in erosion rates across the Eastern Cordillera of Colombia?

Linking the long-term with the short-term exhumation history of a mountain range is vital for understanding the evolution of orogenic topography. Further, erosion rates could be controlled by the variability of climatic and/or tectonic processes over geological time. For example, in the Eastern Cordillera of the Colombian Andes, until recently climate forcing has been hypothesized as the primary driver of rapid Pliocene exhumation rates. In this contribution, we test this climate forcing hypothesis by integrating geomorphic, seismic, geological and published low-temperature thermochronological (Apatite Fission-Track; AFT), and cosmogenic nuclide (CN) data to quantitatively test the correlation of the spatial patterns of exhumation/erosion with either a tectonic or climatic forcing. From a regional perspective, both the long- and short-term erosion rates (derived from AFT and CN data, respectively) have a reasonable correlation with the seismic strain rates and local relief, whereas the contribution of the short-term rainfall patterns to exhumation (and denudation) is either weak or non-existent. For the Eastern Cordillera, tectonism through seismic deformation therefore seems to be a more critical driver of the topographic evolution of the range when compared with the climate variable. To deepen our investigation, we subdivided the study area into six subregions and performed a detailed statistical analysis. In one out of the six subregions (SEC2E), in the Quetame Massif area, short-term rainfall data is well correlated with the computed erosion rates. Nevertheless, the ten-fold difference between the long-term (2.36 km/Myr) and the current (0.27 km/Myr) denudation rates suggest they are strongly decoupled. The remaining five subregions featured varied correlations suggesting that the tectonic-climatic characteristics of each area must be considered and that effective local controls, such as rainfall in subzone SEC2E, cannot be extrapolated to the whole range. Finally, we discuss the tectonic implications of our findings, stressing how tectonic inheritance, typical of inversion orogens such as the Eastern Cordillera, is critical for understanding the spatial variability in exhumation/erosion rates and surface uplift. For instance, we reconstructed the paleoprofiles of four rivers (the Duda, Ariari, Guayuriba, and Guatiquía Rivers), draining the Sumapaz and Chingaza relict landscapes, on the hanging wall of the Servitá Fault, the typical example of an inverted structure. In this way, we evidenced a net surface uplift of at least 1.4 km since the late Miocene, which we speculate primarily controlled by the Servitá Fault. These findings have first-order implications as they provide evidence for Pliocene to Pleistocene landscape rejuvenation driven by tectonically inverted faults.

Active negative flower structure at the western edge of the Tunisian Atlas: Morphotectonic evidence from the case study of Borj Edouane-El Gara Quaternary basin

Located at the Tunisian Atlas area, the Quaternary basin of Borj Edouane-El Gara could serve as a good example for close relation between the continental infill and the neotectonic morphostructural pattern. This Quaternary basin is superimposed on pre-Quaternary basement rocks in the form of an active negative flower structure in a divergent wrench fault zone. The neotectonic evolution of the region has been guided by the plate convergence system. During the Middle-Late Pleistocene, subsidence took locally place in a transtensional deformation zone essentially controlled by strike-slip faults. Closely linked to N–S synthetic and NW-SE antithetic faults, the internal structure of this basin is controlled by a rotational scissor-like kinematics. These faults sets represent inherited structures with normal and lateral components producing a downward rotation of the northern part and an upward rotation of the southern one of the basin. Paleostress analysis shows a progressive change from transtensional in the North to transpressional and compressional deformation toward the Southern corner of the basin where the main synthetic and antithetic faults overlap. During the Holocene, the reactivation of the inherited faulting system has caused the landscape rejuvenation, the basin chopping and the present drainage network architecture. The rates of active tectonics in the Borj Edouane-El Gara Basin has been interpreted through a detailed morphotectonic study of the fault-generated mountain fronts and fluvial systems.

Evaluating the role of topographic inversion in the formation of the Stanislaus Table Mountains in the Sierra Nevada (California, USA)

Abstract The Table Mountains, a flat-topped series of ridges capped by a 10.4 Ma latite flow in the Stanislaus River watershed, are considered to be evidence for late Cenozoic uplift-driven landscape rejuvenation in the northern Sierra Nevada range (California, USA). The commonly accepted theory for the formation of these mesas posits that the latite flowed and cooled within a bedrock paleovalley and, since then, the surrounding landscape has eroded away, leaving behind the volcanic deposit as a ridge. Although this theory is accepted by many, it has not been thoroughly tested. In this study, I examine a series of geological cross-sections extracted along the length of the latite deposit to determine whether the evidence supports the existence of bedrock valley walls on both sides of the 10.4 Ma flow. I find that the presence of older Cenozoic deposits adjacent to the latite flow precludes the possibility that the flow would have been constrained within a bedrock valley. Moreover, the cross-section from an 1865 report that has been offered as evidence of topographic inversion (and subsequently reproduced in numerous publications) does not accurately represent the topography at that site. I conclude that there is no evidence that the bedrock topography has been inverted and that instead, the latite flowed within a channel cut into underlying Cenozoic deposits, which have since mostly eroded away. This study, therefore, refutes the hypothesis that the Stanislaus River watershed was rejuvenated in the late Cenozoic and challenges the claim for recent significant uplift of the region.

Interactions between deforestation, landscape rejuvenation, and shallow landslides in the North Tanganyika–Kivu rift region, Africa

Abstract. Deforestation is associated with a decrease in slope stability through the alteration of hydrological and geotechnical conditions. As such, deforestation increases landslide activity over short, decadal timescales. However, over longer timescales (0.1–10 Myr) the location and timing of landsliding is controlled by the interaction between uplift and fluvial incision. Yet, the interaction between (human-induced) deforestation and landscape evolution has hitherto not been explicitly considered. We address this issue in the North Tanganyika–Kivu rift region (East African Rift). In recent decades, the regional population has grown exponentially, and the associated expansion of cultivated and urban land has resulted in widespread deforestation. In the past 11 Myr, active continental rifting and tectonic processes have forged two parallel mountainous rift shoulders that are continuously rejuvenated (i.e., actively incised) through knickpoint retreat, enforcing topographic steepening. In order to link deforestation and rejuvenation to landslide erosion, we compiled an inventory of nearly 8000 recent shallow landslides in © Google Earth imagery from 2000–2019. To accurately calculate landslide erosion rates, we developed a new methodology to remediate inventory biases linked to the spatial and temporal inconsistency of this satellite imagery. Moreover, to account for the impact of rock strength on both landslide occurrence and knickpoint retreat, we limit our analysis to rock types with threshold angles of 24–28∘. Rejuvenated landscapes were defined as the areas draining towards Lake Kivu or Lake Tanganyika and downstream of retreating knickpoints. We find that shallow landslide erosion rates in these rejuvenated landscapes are roughly 40 % higher than in the surrounding relict landscapes. In contrast, we find that slope exerts a stronger control on landslide erosion in relict landscapes. These two results are reconciled by the observation that landslide erosion generally increases with slope gradient and that the relief is on average steeper in rejuvenated landscapes. The weaker effect of slope steepness on landslide erosion rates in the rejuvenated landscapes could be the result of three factors: the absence of earthquake-induced landslide events in our landslide inventory, a thinner regolith mantle, and a drier climate. More frequent extreme rainfall events in the relict landscapes, and the presence of a thicker regolith, may explain a stronger landslide response to deforestation compared to rejuvenated landscapes. Overall, deforestation initiates a landslide peak that lasts approximately 15 years and increases landslide erosion by a factor 2 to 8. Eventually, landslide erosion in deforested land falls back to a level similar to that observed under forest conditions, most likely due to the depletion of the most unstable regolith. Landslides are not only more abundant in rejuvenated landscapes but are also smaller in size, which may again be a consequence of a thinner regolith mantle and/or seismic activity that fractures the bedrock and reduces the minimal critical area for slope failure. With this paper, we highlight the importance of considering the geomorphological context when studying the impact of recent land use changes on landslide activity.

Episodic exhumation of the Appalachian orogen in the Catskill Mountains (New York State, USA)

Abstract Increasing evidence indicates the eastern North American passive margin has not remained tectonically quiescent since Jurassic continental breakup. The identification, timing, resolution, and significance of post-orogenic exhumation, notably an enigmatic Miocene event, are debated. We add insight by constraining the episodic cooling and exhumation history of the Catskill Mountains (New York, USA) utilizing apatite fission-track thermochronology and apatite (U-Th)/He data from a ∼1 km vertical profile. Multi-kinetic inverse thermal modeling constrains three phases of cooling: Early Jurassic to Early Cretaceous (1–3 °C/m.y.), Early Cretaceous to early Miocene (∼0.5 °C/m.y.), and since Miocene times (1–2 °C/m.y.). Previous thermochronologic studies were unable to verify late-stage cooling and/or exhumation (typically post-Miocene and younger) because late-stage cooling was commonly a spurious artifact of earlier mono-kinetic annealing algorithms. Episodic cooling phases are correlative with rifting, passive-margin development, and drainage reorganization causing landscape rejuvenation. Geomorphologic documentation of increased offshore mid-Atlantic sedimentation rates and onshore erosion support the documented accelerated Miocene cooling and exhumation.

Thermochronologic and geomorphometric constraints on the Cenozoic landscape evolution of the Northern Andes: Northwestern Central Cordillera, Colombia

New geochronologic, thermochronologic, and geomorphometric landscape analyses were performed to discriminate the relationships between tectonics and geomorphology in the northwestern portion of the Central Cordillera, Northern Andes (Colombia). This segment of the Andean belt includes two contrasting geomorphic domains, namely the Antioqueño Plateau (AP) and the Cauca River Canyon (CRC). At present, these domains are connected fluvially by the San Andrés River Catchment (SARC) and disrupted structurally by the Espíritu Santo Fault (ESF). Zircon U/Pb ages indicate Triassic metamorphism and Late Cretaceous magmatism, suggesting the absence of major Cenozoic thermal events related to magmato-metamorphism that could affect low-temperature thermochronology datasets. New (U-Th)/He data were collected along vertical profiles and modeled numerically using HeFTy® and Age2Edot® software. The modeling results suggest a continuum rapid cooling event during the Paleocene- Eocene associated with erosional exhumation. Erosion rates derived from relationships between zircon (U-Th)/He ages and elevation, are approximately 0.2–0.6km/Ma and therefore slightly lower than estimates derived from inverse thermal modeling (ca. 0.6–0.9km/Ma), Differences between observed and estimated exhumation rates could be due to differential surface uplift and reactivation of the ESF. Such reactivation produced systematically younger (U-Th)/He ages near faulted, popped-up blocks, suggesting active deformation since the Oligocene–Early Miocene. Geomorphometric parameterization, applied to both the AP and the CRC, suggests a complex mixture of processes such as differential surface uplift, landscape rejuvenation, relief inversion, preservation of relict landscapes, and reorganization of the fluvial system. Our investigation documents: i) a phase of rapid exhumation during the Late Paleocene-Eocene that favored posterior development of low relief surfaces; ii) post-Eocene ESF reactivation, differential uplift, and relict landscape preservation on the AP; and iii) post-Oligocene landscape rejuvenation and fluvial capture of the SARC by upward progression of the erosional wave-front through the CRC.

Morphometric evidences of recent tectonic deformation along the southeastern margin of the Hyblean Plateau (SE-Sicily, Italy)

The present work focuses on the tectonic characterization of the southeastern portion of the Hyblean Plateau (SE-Sicily, Italy). Along the southeastern margin of this raised crustal block, a clear recent antiformal deformation, coupled with diffuse landscape rejuvenation, affects the summit surface. Many studies, using merely qualitative geomorphological approach, refer the recent morphotectonic evolution of this region to motion along an active border fault, located at the base of the well-developed, arc-shaped Avola mountain front. This paper provides new insights resulting from the morphometric analysis across the Avola region, in order to detail on the relationships between the landscape geomorphic unsteadiness and the long-term tectonic deformation. We perform both drainage system and relief investigations, consisting of the exploration of different geomorphic indices (e.g. hypsometric integral, topographic relief and dissection, SL index, ksn), long-profile analysis, marine terraces age model definition, field-based geomorphological and structural surveys. The results and the spatial distribution of morphometric indexes evidence the occurrence of two incipient NNE trending en-échelon fault segments, here named Cassibile-Noto Fault, responsible for the relief building along the southeastern border of the Hyblean Plateau. The northern fault segment directly controls the northern portion of the Avola mountain front, whereas the southern segment diverges from the main scarp, cutting through the low-standing areas of the coastal plain. In addition, the centrifugal arrangement of fluvial captures and the half-elliptical envelope of the downstream projections of coeval paleo-long profiles, as well as the distribution of Pleistocene marine terraces, well evidence the long-term WNW-ESE-trending low-amplitude bow-shaped deformation affecting the footwall of the Cassibile-Noto normal fault. We relate this convex-upward trend to the Late Pleistocene (<125 ka) tectonic deformation cumulated, at rate of ~0.80 ± 0.05 mm/a, along the active fault. This incipient tectonic structure represents an extensional tectonic boundary that accommodates, together with the Ispica Fault, the active NW-ward motion of the entire eastern sector of the Hyblean Plateau. Overall, the proposed updating of the tectonic setting of the study area, framed in the regional geodynamic picture of the eastern Sicily, would contribute to define a more suitable geological risk assessment of the region.

Cooperative Historic Landscape Rejuvenation in China: The Litchi Bay Project in Guangzhou

This article introduces the Litchi Bay Canal Project, a recent cooperative historic landscape rejuvenation in Guangzhou, China. The Litchi Bay Canal and the Sai Kwan Literary Pagoda were at the core of Litchi Bay, historically an important scenic area in Canton (Guangzhou). However, since the 1950s, the area has changed. The Lungchun Warehouse was built around the pagoda and the canal was covered by concrete planks and turned into a road in 1993. Soon after that, antique shops appeared along the road and folk activities related to the canal and the pagoda ceased to happen. In 2010, a systematic rejuvenation project was launched to restore the historic landscape through negotiation with and the cooperation of government and non-government entities, villagers and nearby residents. The canal was uncovered, the pagoda revealed and the Lungchun Warehouse was renovated into an antiques market. Together, these actions produced attractive public spaces for today’s daily life as well as for traditional rituals. Based on the experience of the first author as the lead architect of the project, this article reviews the project, the restoration of the historic landscape and the regeneration of the urban public spaces. It analyses the holistic approach and the mechanisms of the project, discusses the thinking and specific operations to re-initiate the dialogue between the canal, the waterfront promenade and the historic buildings through an understanding of their mutual relationships.

Experimented methods to moderate the impact of climate change in Auroville

The city of Auroville was founded in 1968 on the Coromandel Coast of South India. It has gone through exemplary landscape rejuvenation during the past decades. The once heavily eroded area has become a green biosphere. Conscious water management, reforestation, coastal protection, sustainable agriculture, a holistic urban plan and the use of alternative energy have been thoroughly researched and implemented in Auroville. Recent natural disasters have highlighted that the rehabilitated landscape and the conscious town planning of Auroville can offer certain protection from the impact of climate change. Auroville and its bioregion have experienced several natural disasters. A tsunami hit the coast in 2004, Hurricane Thane struck in 2012, a flood occurred in 2015, and a severe drought occurred in 2017. Over the last two decades, sea level rise and the disappearance of the coastline have been significant, as well as the intrusion of the seawater into the groundwater. Throughout these events Auroville environment remained noticeably more safe and healthy than its surrounding bioregions. Decades of cooperative projects with the villages in the bioregion have enabled Auroville to quickly act after disasters, avoiding aggravated situations such as outbreaks of epidemics. The achievements of Auroville can be a good example for cities of the Coromandel Coast and around the world.

Active tectonic deformation along reactivated faults in Binta basin in Kumaun Himalaya of north India: Inferences from tectono-geomorphic evaluation

We discuss the tectono-geomorphic evaluation of the Binta basin (Lesser Himalaya, India) through quantitative and qualitative morphotectonic analyses at the watershed scale. The basin, drained by the Gagas River and its tributaries, is situated in the zone of the active North Almora Thrust (NAT). Developments of deeply incised V-shaped valleys indicate increased incision capability of streams in response to steepening of hillslope gradients due to neotectonic activity. Prominent features, e.g., off-setting of the NAT by later formed subsidiary faults, deflection of streams, vertical fault scarps, formation of palaeolakes, river ponding and development of fluvial terraces were likely responsible for reformation of the landscape and drainage system due to tectonic perturbations. The morphometric parameters using digital terrain data in the GIS technology and focusing on hydrography (stream length-gradient index, ratio of valley floor width to valley height, transverse topographic symmetry factor and topography (local relief and relief anomaly) verify the rejuvenation of landscape. Anomalously high and low values of stream length-gradient indices of main tributary streams associated with faults and multiple knickpoints along the channel profiles may have been associated with deformational events. Our observations on the tectonic instability of the faulted basin support the existing GPS based studies indicating the maximum crustal shortening and strain rate with a maximum aerial strain of 6-8 x 10(-7) strain/year and deformation of similar to 15 mm/year immediately north of the NAT, and proving that this tectonically active zone is vulnerable for the future earthquakes.

From extension to transpression: Quaternary reorganization of an extensional-related drainage network by the Alhama de Murcia strike-slip fault (eastern Betics)

The complex present-day drainage network of the Lorca–Totana area records the changing tectonic setting, from extension to transpression, in the eastern Betics. Through a detailed morphometric analysis we evaluate the topographic response to this major change in the tectonic setting and the influence in the drainage of Miocene extension and middle Pleistocene to present day transpression. The present-day drainage network preserves geomorphic features inherited from Late Miocene extension that are being overprinted by a new transverse fluvial system. This new system advanced towards the NW since the middle Pleistocene in response to a localized base-level drop related to the NE–SW oriented Alhama de Murcia sinistral-reverse fault. Geomorphic indexes calculated in this work suggest the present-day activity of the Alhama de Murcia fault and the Sierra de la Tercia anticline, the two major tectonic structures in the area. The landscape rejuvenation associated with this process results in: contrasting mountain front sinuosity values between old and new mountain fronts, high SLk index anomalies, convex-shaped and complex hypsometric curves, knickpoints in river profiles, contrasting slope–area plots and high steepness index values. This fluvial reorganization was driven progressively by successive fluvial captures preserved as wind-gaps in the present-day drainage network.

Post-Miocene landscape rejuvenation at the eastern end of the Alps

In the debate on the causes of uplift and landscape evolution of the Alps, most studies focus on regions that were glaciated at some stage during the last 2 m.y. In these areas, it is difficult to separate glacial-driven versus tectonically driven rates of erosion. Here, we present 10 Be-derived erosion rates from unglaciated catchments in the Koralpe range at the eastern end of the Alps. This region features strong geomorphologic evidence for landscape transience with young valleys incised into a smooth relict landscape. Erosion rates average 49 ± 8 mm/k.y. for catchments located on the relict landscape and 137 ± 15 mm/k.y. for catchments in the incised landscape. From these data, we estimate the onset of incision at 4 ± 1 Ma, the surface uplift at 350 ± 90 m, and a total relative base-level fall of 540 ± 140 m. Our results are in close agreement with both the magnitude and the age of onset of uplift of the Styrian Basin and the northern Molasse Basin, as well as the incision rate of the Mur River into the Styrian karst. The inferred timing of the onset of uplift around 4 Ma relates to interpreted basin inversion in the Pannonian Basin. Since this uplift event appears to have involved both the Pannonian Basin and the entire eastern end of the Alpine mountain range, we suggest that it may have occurred in response to a deep-seated process in the lithosphere. As such, we argue for tectonic drivers for the post-Miocene uplift in the eastern Alps.

Provenance study of Pliocene–Pleistocene sands based on ancient detrital zircons (Alvalade Basin, SW Iberian Atlantic coast)

Pliocene–Pleistocene sand of the Alvalade basin was taken from the sea-cliffs of SW Iberia coast for a provenance study using radiometric dating. The U–Pb ages obtained revealed a wide interval ranging from Cretaceous to Archean, with predominance of Paleozoic, Neoproterozoic and Cretaceous zircon ages. Cretaceous ages interpreted to indicate a Sines Massif provenance are dominant in sands close to Cape Sines but are absent in sand sampled 12 km north. Carboniferous ages younger than ca. 315 Ma suggesting a possible contribution from the Central-Iberian Zone originally; however, these zircons may be multi-cyclic, having been reworked from Eocene–Miocene siliciclastic deposits related to transport from central Iberia (Lower Tagus basin drainage evolution). These signatures provide important constraints on the location and extent of the Pliocene–Pleistocene topography and drainage system that were probably controlled by: i) Miocene to Pleistocene landscape rejuvenation driven by Alpine movements along major faults; and ii) residual reliefs related to inherited Variscan structure. The U–Pb ages obtained also trace the pre-Cenozoic paleotectonic evolution of SW Iberia recorded in their sources: i) the North Gondwana accretion and breakup; ii) the Gondwana and Laurussia collision; and iii) the Pangea breakup and opening of the Atlantic Ocean.