Length‐scale dependence of relief along the south eastern border of Massif Central (France)

Lucazeau, Francis; Hurtrez, Jean Emmanuel

doi:10.1029/97gl01673

Cited by 13 publications

(12 citation statements)

References 9 publications

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“…Geophysical Relief is therefore the difference between maximum elevations smoothed in this way and the raw present-day elevations (pink area in Figure 3). Geophysical Relief increases with the area over which it is calculated following approximately a power law, with most exponents lying between 0.3 and 0.5 ( Figure 4 and Table 1), as previously noted by Ahnert [1984] and Lucazeau and Hurtrez [1997]. This scaling of relief versus area of calculation window allows a comparison of values from different ranges and computation of values for specified radii.…”

Section: Topographic Variablesmentioning

confidence: 70%

Tectonics, climate, and mountain topography

et al. 2012

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[1] By regressing simple, independent variables that describe climate and tectonic processes against measures of topography and relief of 69 mountain ranges worldwide, we quantify the relative importance of these processes in shaping observed landscapes. Climate variables include latitude (as a surrogate for mean annual temperature and insolation, but most importantly for the likelihood of glaciation) and mean annual precipitation. To quantify tectonics we use shortening rates across each range. As a measure of topography, we use mean and maximum elevations and relief calculated over different length scales. We show that the combination of climate (negative correlation) and tectonics (positive correlation) explain substantial fractions (>25%, but <50%) of mean and maximum elevations of mountain ranges, but that shortening rates account for smaller portions, <25%, of the variance in most measures of topography and relief (i.e., with low correlations and large scatter). Relief is insensitive to mean annual precipitation, but does depend on latitude, especially for relief calculated over small ($1 km) length scales, which we infer to reflect the importance of glacial erosion. Larger-scale (averaged over length scales of $10 km) relief, however, correlates positively with tectonic shortening rate. Moreover, the ratio between small-scale and large-scale relief, as well as the relative relief (the relief normalized by the mean elevation of the region) varies most strongly with latitude (strong positive correlation). Therefore, the location of a mountain range on Earth with its corresponding climatic conditions, not just tectonic forcing, appears to be a key factor in determining its shape and size. In any case, the combination of tectonics and climate, as quantified here, can account for approximately half of the variance in these measures of topography. The failure of present-day shortening rates to account for more than 25% of most measures of relief raises the question: Is active tectonics overrated in attempts to account for present-day relief and exhumation rates of high terrain?

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Section: Topographic Variablesmentioning

confidence: 70%

Tectonics, climate, and mountain topography

et al. 2012

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“…The value of geophysical relief obtained by this method strongly depends on the ‘tension’ of the smooth surface, i.e. the number of the high points chosen (Ahnert, ; Lucazeau and Hurtrez, ; Champagnac et al , ). For our calculation, we created two smooth surfaces with different ‘tension’ using two border values for flow accumulation (over 1000 cells and over 2000 cells) that correspond to the range of representative values.…”

Section: Methodsmentioning

confidence: 99%

Controls on Holocene denudation rates in mountainous environments under Mediterranean climate

Molliex

Jouet

Freslon

et al. 2016

Earth Surf Processes Landf

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“…We used the GTOPO30 database [ USGS‐EDC , 1996] at the resolution of 30 arc sec. Several morphologic analyses have used large‐scale databases to characterize morphologic properties of topography [ Weissel et al , 1994; van der Beek and Braun , 1998; Lucazeau and Hurtrez , 1997; Vörösmarty et al , 2001]. We have selected 35 drainage basins related to the Gulf of Guinea (Figure 7 and Table 1), including 27 tributaries of the Congo River and 8 coastal rivers located between 3°N and 12°S.…”

Section: Digital Elevation Analysismentioning

confidence: 99%

“…Relief is basically defined as the elevation difference for a given length scale [ Anhert , 1970] and has been determined in this study at all scale domains by the technique of structure functions [ Weissel et al , 1994; Lucazeau and Hurtrez , 1997]: R(l) = 〈∣h(x + l) − h(x)∣〉, where h is the elevation, x the horizontal position, l the window length scale and angle brackets refer to the average of all elevation differences in the length scale window l. A power law relationship R(l) = R 0 l H can describe how relief R(l) increases with length scale l. R 0 is relief at a reference scale (l = 10 km for instance) and H is the Hurst exponent related to the fractal dimension of topography; Because R(l) is an average value of all couples in the length scale range l, H tends to 1 for a smooth topography and H tends to 0 for a rough topography. Several studies [ Weissel et al , 1994; Lucazeau and Hurtrez , 1997; van der Beek and Braun , 1998], proposed that several domains of scales may be identified according to the processes that create topography: diffusive hillslope processes at small scale, river incision at mesoscale and tectonics or geodynamics at large scale. Resolution of GTOPO30 is not good enough to access the small‐scale processes and the smooth trend observed at the lower scales in this study (Figure 10) is mostly caused by the interpolation of the DEM.…”

Section: Digital Elevation Analysismentioning

confidence: 99%

Dynamic interactions between the gulf of Guinea passive margin and the Congo River drainage basin: 1. Morphology and mass balance

2003

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A sediment budget between the Congo River drainage basin and the western African margin in the Gulf of Guinea is proposed on the basis of published and unpublished offshore Tertiary isopach maps, and onshore digital elevation analysis. The overall denudation of that area may be as high as 3.5 × 106 km3 with a maximum of 10% coming from Mesozoic and Cenozoic covers. The southern part of the Congo River basin, related to uplift of the South African and Kalahari shields, appears as the most immature from the morphologic standpoint but provides one third of the present‐day sediment production; it represents a maximum denudation of 150,000 km3. On the easternmost part, East African Rift drainage basins show a more mature relief and a maximum denudation of 270,000 km3, which can increase to 570,000 km3 if the Congo drainage basin had extended up to the east branch of the rift. These values are confidently established from the existence of remnant geological surfaces, and can explain the volume of Tertiary sediment in the Gulf of Guinea. During upper Cretaceous, the most important accumulations of sediments correspond to the Ogooe and Kwanza fans, which shows that the organization of continental drainage was different as was potential source of sediments. In the northern part of the present‐day Congo River drainage basin, there was a compressional episode during Santonian that may have caused significant relief and erosion along a Benue‐Chad axis.

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Length‐scale dependence of relief along the south eastern border of Massif Central (France)

Cited by 13 publications

References 9 publications

Tectonics, climate, and mountain topography

Tectonics, climate, and mountain topography

Controls on Holocene denudation rates in mountainous environments under Mediterranean climate

Dynamic interactions between the gulf of Guinea passive margin and the Congo River drainage basin: 1. Morphology and mass balance

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