An incision wave in the geologic record, Alpujarran Corridor, southern Spain (Almerı́a)

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. d late Pleistocene alluvial morphostratigraphy in the Rı́o 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 Rı́o 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. oxygen isotope Stage 2 (“OIS2”) and/or oxygen isotope Stage 1 (“OIS1”), sediment availability in the Rı́o 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.