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The term “incision wave” was coined in the 1990s to describe wave-like patterns of stream incision propagating through numerically modeled bedrock-channel river systems. An incision wave consists of a crest where available stream power is greatest, and where vertical incision is most rapid. The crest is flanked by limbs where there is less available stream power and where vertical incision rates are slower. Farther away from the crest, available stream power is less and incision rates are slower than in the limbs. Modeling results suggest tectonically induced base-level fall triggers incision waves that propagate upstream through bedrock-stream networks. However, it has recently been postulated that the equation underpinning incision-wave models cannot realistically simulate river systems. This paper provides field-geological evidence supporting the hypothesis that tectonically induced base-level fall triggers incision waves that propagate through bedrock-stream networks for tens of kilometers.Mid and late Pleistocene alluvial morphostratigraphy in the Rı´o Andarax drainage basin, southeast Spain is interpreted to indicate that patterns of paleo stream power were controlled by an incision wave. In the conceptual model proposed in this paper, the signature of an incision wave in the Rı´o Andarax drainage network is recorded by the contrasting morphostratigraphy of oxygen isotope stage 8 (“OIS8”) time landforms. At the crest of the incision wave during OIS8, there is no record of a paleoalluvial level because available stream power exceeded critical stream power and streams were incising vertically. The crestal area is flanked by OIS8-time strath terraces, which record the position of the two limbs of the incision wave. Farther upstream, OIS8-time alluvial fills mark an area unaffected by the incision wave.During oxygen isotope Stage 2 (“OIS2”) and/or oxygen isotope Stage 1 (“OIS1”), sediment availability in the Rı´o Andarax catchment was low, and the pattern of relative stream power was threshold-like rather than wave-like. Differences in the manifestation of the incision wave during OIS8 vs. during OIS2 and/or OIS1 indicate that climate and sediment availability can control how incision waves propagate through fluvial systems. [Copyright &y& Elsevier]

Abstract: The northern slope of the Sierra de Aitana (Eastern Betic Cordillera) is characterized by a long mountain front with a prominent Eocene limestone scarp overlying ductile Eocene marlstones. This stratigraphic feature and the highly stepped topography produced by several normal faults favor gravitational processes such as rock avalanches, rock slides and rock falls. This paper reports a compound landslide comprising a rotational rock slide and slab-type lateral spreading affecting these materials with blocks of volumes up to 106 m3. This lateral spread process produced singular and spectacular morphological features, the Simas de Partagat, which are trenches 20m wide and up to 40m deep, formed by the widening of discontinuities. The use of a differential SAR interferometry technique for monitoring this landslide over a time span of 11yr has revealed that velocity of movement is insignificant, with rates comprised between 0 and 2mmyr−1 and cumulative negligible displacements. Individual rock blocks initially located at the free face of the scarp were affected by slides at the base of the scarp, descending from a few to several dozen meters along the slope. Blocks broke up as displacement progresses, with several in different stages of evolution being recognizable along the slope. Differential SAR interferometry shows a greater activity in the area north of compound landslide, although velocity is extremely low (below 16mmyr−1). This extremely slow movement revealed by interferometry is in agreement with other geological and geomorphological evidence such as the existence of speleothems and cemented breccias against the head walls of the trenches. Both deposits are indicative of a long period of discontinuity widening. Also, undisturbed debris deposits covering ancient rock slides are indicative of very slow gravitational processes characterized by long dormant periods. In addition, a historical picture from 1898 shows nearly negligible change in the Simas de Partagat over this 112yr period. [Copyright &y& Elsevier]

Abstract: The Arroyo de Gor is a highly incised stream (up to 200 m) that has eroded into the Pliocene–Pleistocene infill of the Guadix basin in the Betic cordillera (SE Spain). This paper concentrates on a particular reach of this stream, namely the Cenascuras–Gorafe reach, where abundant inactive rotational slides can be recognized on both hillslopes of the canyon-shaped valley. The rotational slides have surface areas of 5–15 ha and volumes of mobilized material of 5–15 Hm3. These rotational slides can be recognized by their main scarps, which are still well featured at both margins of the valley, as well as by the counter hillslope rotation of the strata in their bodies. The surfaces of rupture are concave, their width being greater than their length, i.e. the landslides are elongated in a direction perpendicular to the landsliding displacement and parallel to the stream. At depth, the surfaces of rupture developed on fine-grained sediments (mostly clays) underlying the conglomerates and sands affected by the rotational slides. The clays at the surface of rupture are smectite-rich and show several features produced by the landsliding, such as striations and sigmoidal-shaped structures. The Cenascuras–Gorafe canyon has been developed by a combination of entrenchment, fracturing and landsliding. Initial deep entrenchment of the stream is attributed to a base-level lowering related to the capture of the former endorheic basin by the Gualdalquivir river in the late Pleistocene. This river incision created a canyon with subvertical unstable walls, which due to gravitational instability would give way to vertical open tension cracks some distance from the canyon edge. The tension cracks would end at depths equal to the base of the canyon, which also coincides with the contact between the conglomerates and the underlying clays. The rotational slides are thought to have occurred during heavy rains by a combination of piping, which would have lengthened the tension cracks, and infiltration, which would reduce the shear strength along the gently dipping contact between conglomerates and the underlying clays. Thus, the blocks bounded by the tension cracks and the subhorizontal lithological contact would slide under their own weight on the subhorizontal surfaces of reduced shear strength. Several age constraints lead us to tentatively assign the landslides to the Isotope stage 5 (around 32 ka), an interglacial period agreed to be wetter and slightly warmer than the present-day semi-arid climate. [Copyright &y& Elsevier]