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Call for Papers for the semi-thematic N° 67: (Re)defining rural territories, between the global South and North: actors, processes, scales.
Full papers are invited to be submitted via the journal's official platform by 15 March 2024.
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Slope evolution and fluvial morphogenesis in the subtropical dry dominion according to detailed geomorphological map (Ex.: semio arid Chile)
Abstract
The sample area is located in the middle lower part of the Choapa river basin in
Chile (31° 30'S-71° 20'W). The principal forms of the landscape are: the mountainous slopes, the high terrace, the "bahadas" ("glacis colluviaux") and the small alluvial fans, the low terrace and the alluvial beds.
The geomorphological map "sensu stricto" contains slope and fluvial processes
and landforms. The morphogenetic context of the landforms is represented
with different colors, tonal gradations showing tbe age.
The relative age of the morphogenesis is as follows:
A. Remainders of culminating erosion surfaces, dissection of great valleys
and erosional steps in middle slope: Neogene (N 1 and 2).
B. High terrace: Lower Pleistocene (Q 1).
C. Dissected valleys on the ancient high terrace: Middle Pleistocene (Q 2).
D. "Glacis colluvial" (lower slope "bahada") over the high terrace, low
terrace and lateral alluvial fans: Upper Pleistocene (Q. 3)
E. Dissection of glacis and lower terrace, preparation of tbe present day
slope morphogenetic system and polychronic continum of some surface processes: Holocene (Q 4).
Tbe present day morphogenetic system is influenced by inherited and relict
features. as the morphological slope stepping and the deep regolith. which inIluences the micro-relief. The climatic analysis shows strong irregularities and
the human activity generates a break of equilibrium in the system. Soil creep and surface wash produces surface soil beheading. On the beheaded surface of the upper slope, mudflows can eventually be generated. Downward, gullies appear on the middle slope. Finally, the lower slope is depositional. Upper, middle and lower slope are related to a convex-concave slope upward the high terrace.
The proposed evolutive model is the YOUNG, s (1977) 6th model for slopes:
control by removal on upper and middle slope: control by accumulation on the
lower slope; removal of regolith entirely by surface transport; rate of surface
transport proportional to sen of the slope angle theta.
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