Catchment-wide erosion rates relying on cosmogenic nuclides provide new clues on the evolution of marine terraces along the Cantabrian margin

Extensive marine terraces preserved along the Cantabrian coast have been pointed out as good markers to understand the recent tectonic evolution of the Cantabrian margin in north Iberia. These landforms are interpreted as a single, kilometric-wide abrasion platform eroded during the Pliocene marine transgression (Mary 1983) which were later uplifted and faulted due to recent tectonic activity (Álvarez-Marrón et al., 2008). A recent study also points to continuous rising in response to lateral gradient in crustal thickness as a mechanism to explain the subtle variations in surface tilt observed only in the marine terraces of the western coastal areas (López-Fernández et al., 2020).

This contribution provides the first catchment-wide erosion rate estimates based on cosmogenic ¹⁰Be-²⁶Al measured in two sediment samples retrieved from a 3.1 km² extent fluvial basin incised in the marine terrace. The river basin is entirely composed by quartz-bearing rocks belonging to the Serie de los Cabos formation, which comprises alternating slate, sandstone and quartzite. Total incision since terrace formation reaches 80 m along the main river stream, while 21.2 m is the average incision achieved considering the total volume of material removed (ca. 60 Hm³) since the terrace uplift from an area of 283.3 Ha. Using the code Riversand v. 1.3.1 by Stübner et al. (2023), we computed catchment-wide erosion rates of 11.5 to 12.1 mm/ka based on ¹⁰Be and 17.3 to 18 mm/ka based on ²⁶Al. These rates involved that at least 1.2 to 1.9 Ma are required to achieve ~21 m of averaged incision, which is in good agreement with previous minimum surface exposure ages of 1-2 Ma estimated combining ¹⁰Be-²⁶Al-²¹Ne (Álvarez-Marrón et al., 2008). Similar analysis in other catchments might help to expand our current knowledge on the erosion patterns of these landforms, improving our understanding on competing mechanisms involved in the origin and dismantle of marine terraces.

Research funding: RETROCLIFF (PID2021-122472NB-100, MCIN/AEI/FEDER, UE) and GEOCANTABRICAE (SV-PA-21-AYUD/2021/51766, FICYT, Principality of Asturias, UE, ERDF).

 References:

• Álvarez-Marrón, J., Hetzel, R., Niedermann, S., Menéndez-Duarte, R., Marquínez, J. (2008). Origin, structure and exposure history of a wave-cut platform more than 1 Ma in age at the coast of northern Spain: A multiple cosmogenic nuclide approach. Geomorphology 93, 316-334. https://doi.org/10.1016/j.geomorph.2007.03.005
• Mary, G. (1983). Evolución del margen costero de la Cordillera Cantábrica en Asturias desde el Mioceno. Trabajos de Geología 13, 3-35.
• López-Fernández, C., Llana-Fúnez, S., Fernández-Viejo, G., Domínguez-Cuesta, M.J., Díaz-Díaz, L.M. (2020). Comprehensive characterization of elevated coastal platforms in the north Iberian margin: A new template to quantify uplift rates and tectonic patterns. Geomorphology 364, 107242. https://doi.org/10.1016/j.geomorph.2020.107242
• Stübner, K., Balco, G., Schmeisser, N. (2023). Riversand: a new tool for efficient computation of catchmentwide erosion rates. Radiocarbon. https://doi.org/10.1017/RDC.2023.74