Longitudinal profiles morphology and incision - uplift rates in the Nothern Sector of Gran Canaria Island (Spain)

Abstract

Analysis of digital elevation data of stream channels (barrancos) incised into dated volcanic materials of the Gran Canaria Island (Canary Islands, Atlantic Ocean) permit to define the geometric parameters of their longitudinal profiles, to evaluate well-constrained incision rates, and to relate incision rates to uplift rates. The study covers the NE and N W quadrants of the island and a total amount of 48 drainage basins have been analysed. Most of the channels show a characteristic straight (linear) to weakly convex/concave long-profile, punctuated by steep knickpoint occurrence. These are similar to those occurring in other volcanic islands (i.e. Hawai) and they do not respond to the classical stream-power dependent erosion law, but to step-wise lowering caused by knickpoint propagation related to relative base-level changes or large mass-wasting processes within the drainage basins. Rates may vary from ca. 0.05 – 0.2 mm/yr (long-term rates) to ca. 3.3 – 4.5 mm/yr (short-term). However the case, data show that differential incision occurs throughout the Northern sector of the island, displaying an overall trend of increasing rates from NWto NWoperating in all stream channels length categories. These values of incision can be translated to qualitative uplift, indicating the occurrence to major uplift in the NE sector of the island than in the NE-E one. The highest precipitations (major potential of denudation) over the NNE zone of the island might facilitate this tendency. However the flexural effect related to the differential isostatic overloading imposed on the lithosphere by the larger Tenerife Island (SW of Gran Canaria) must also be considered.