Combining allostratigraphic and lithostratigraphic perspectives to compile subregional records of fluvial responsiveness: The case of the sustainably entrenching Palancia River watershed (Mediterranean coast, NE Spain)

Abstract

We use a combined allostratigraphic and morpholithostratigraphic approach to establish a relative stratigraphy of macroscale sediment-landform units in the Mediterranean Palancia River watershed (986-km2, NE Spain). Four alloformations signifying important changes in (sub)regional scale geomorphic valley-floor evolution were identified based on data from 1120 field sites and age determinations, and from analyzing high resolution geodata. The formation of the widespread and thick Pleistocene alloformation can be attributed to climatically-induced excessive sediment supply and flood activities during Pleistocene cold intervals — rather than representing time-lagging response to Plio/Pleistocene neotectonic uplift. Triggered by the turn to Holocene climatic conditions, three successively inset alloformations illustrate how stream grading and floodplain narrowing continuously have progressed over the Holocene. The overall degradational valley-floor evolution in the Holocene is interpreted as a response to the antecedent, overly valley-floor aggradation. Allostratigraphic and morphostratigraphic data suggest that the abandonment of the two earlier Holocene alloformations geomorphologically represents a pulsed turn toward intensified entrenchment rather than pulsed sedimentation. The most important benefit of amalgamating allostratigraphic and (morpho)lithostratigraphic concepts is that allostratigraphic ordering provides a formally conclusive approach to scale up (morpho)lithostratigraphic information from the reach scale to much larger scales of geographical extent. Consequently, applying allostratigraphic principles opens a perspective to moving forward toward analyzing the relationships between climate, neotectonics, sea level change, human impact, and fluvial response in coupled hinterland-coastal systems that require to evaluate sedimentary information at larger spatial scales.