Geoheritage of the Iconic EN280 Leba Road (Huila Plateau, Southwestern Angola): Inventory, Geological Characterization and Quantitative Assessment for Outdoor Educational Activities

Abstract

The EN280 Leba Road is a mountain road that runs along the western slope of Serra da Leba (Humpata Plateau) and its outstanding escarpments, connecting the hinterland areas of the Province of Huila to the coastal Atlantic Province of Namibe, in Southwest Angola. In the Serra da Leba ranges, as in Humpata Plateau, a volcano-sedimentary succession of Paleo-Mesoproterozoic age known as the Chela Group outcrops extensively. This main unit records a pile of sediments with a thickness over 600 m, overlying a cratonic basement with Eburnean and pre-Eburnean granitoids. This sequence is overlain in unconformity by the Leba Formation, which consists of weakly deformed cherty dolostones rich in stromatolites. Along the EN280 Leba Road, in the downward direction, were inventoried and characterized eight sites that, by their exceptional geological content and the singularity of their geoforms, are worth being defined and formalized as geosites: (1) traditional mining clay pit in the Humpata Plateau (post-Eburnean Paleo-Mesoproterozoic claystones); (2) old lime oven of Leba (post-Eburnean Meso-Neoproterozoic cherty dolostones with stromatolites); (3) viewpoint of the Serra da Leba (post-Eburnean Paleo-Mesoproterozoic volcano-sedimentary formations and Eburnean Paleoproterozoic granitoids); (4) vertical beds at the beginning of the descent (post-Eburnean Paleo-Mesoproterozoic volcano-sedimentary formations); (5) slope of the fault propagation fold (post-eburnean Paleo-Mesoproterozoic volcano-sedimentary formations); (6) reverse fault in granitoid rocks (Eburnean Paleoproterozoic granitoids); (7) Dolerite Curve (Eburnean Paleoproterozoic granitoids and dolerites); (8) ductile simple shear zone (Eburnean Paleoproterozoic granitoids and mylonites). These sites were primarily selected using the results of fieldwork (observations, measurements, reproduction of representations, and creation of models), interpretation of remote sensing data, and data from previously published bibliographies and cartography. A quantitative assessment of the selected sites to be preserved through their classification as geosites (integration in a geoconservation strategy) was proposed. The first position in the numerical assessment is occupied by the landscape dimension geosite “Viewpoint of the Serra da Leba”. This position is conferred, mainly, by its high geological, use, and Management values, being therefore considered the place with the highest geoheritage value in the studied area. Based on the previous characterization and evaluation, several field activities were proposed to be included in a guidebook, highlighting aspects such as landscapes, outcrops, rocks, structures, fossils, and georesources. The high scientific, didactic, and aesthetic values of these geological contexts and their high degree of geodiversity justify their integration into a geoeducational transect, contributing to the appreciation and awareness of the geological heritage of Serra da Leba, as well as to its promotion and scientific and educational dissemination.