Geomorphological analysis using small unmanned aerial vehicles and submeter GNSS (Gara Soultana butte, High Plateaus Basin, Eastern Morocco)

A Benito-Calvo,H Haddoumi,H Aouraghe,A Oujaa,M.G Chacón,R Sala-Ramos

doi:10.1080/17445647.2020.1773329

Abstract

ABSTRACT The High Plateaus Basin is an important region to understand landscape evolution and human occupation in North Africa during the Quaternary. We focused on the Gara Soultana area, applying Unmanned Aerial Vehicles, photogrammetry and a submeter Global Navigation Satellite System, for large scale geomorphological mapping. This work in the upper Moulouya catchment has allowed us to define the landform sequence. Conglomerate platforms previously considered to be fluvial terraces, are interpreted here as exhumed bedrock layers of the Plio-Pleistocene stacked series. The El Haï river incision consists of a first phase, represented only by the exhumation of Gara Soultana butte, and a second phase when five strath terraces developed from +20-22 m to the thalweg, formed since the Middle Pleistocene. Holocene terraces could be associated with brief aggradation phases in the lower Moulouya catchment due to rapid climate changes. Fluvial incision led to the formation of mantled pediments and talus flatirons.

Highlights

The High Plateaus Basin represents the NW sector of the Intra-Atlas Maghrebian depression, which is one of the biggest intramountain depressions in the Mediterranean catchment and several archaeological findings indicate that it is a key region to understand the Stone Age sequence in North Africa (Aouraghe et al, 2013; Sahnouni et al, 2018; Sala-Ramos et al, 2017; Saoudi, 2012)
We carried out the first large scale geomorphological analysis of the High Plateaus Basin focused on Gara Soultana hill and the El Haï valley (Za River tributary, Upper Moulouya catchment), where previous regional works mentioned pediments and conglomerates interpreted as fluvial terraces (Laouina, 1990; Muratet, 1991; Russo, 1927; Stretta, 1952; Wengler & Vernet, 1992)
Several open access Digital Elevation Models (DEM) are available and tested for geomorphological studies (Boulton & Stokes, 2018), showing spatial resolution of 30 m (SRTM, ASTER, AW3D, ASTER DEM), and 12 m (TanDEMX). These global WorldDEM still shows limitations for large scale and more detailed geomorphological studies where higher resolution and spatial accuracies are necessary. We addressed this issue by using small Unmanned Aerial Vehicles and Structure from Motion Photogrammetry (SfM), as a low-cost, rapid and portable alternative to produce high-resolution topographic surveys (Hackney & Clayton, 2015; Hugenholtz et al, 2013; Jorayev et al, 2016)

Summary

Introduction

The High Plateaus Basin represents the NW sector of the Intra-Atlas Maghrebian depression (around 127,600 km, Figure 1), which is one of the biggest intramountain depressions in the Mediterranean catchment and several archaeological findings indicate that it is a key region to understand the Stone Age sequence in North Africa (Aouraghe et al, 2013; Sahnouni et al, 2018; Sala-Ramos et al, 2017; Saoudi, 2012). We carried out the first large scale geomorphological analysis of the High Plateaus Basin focused on Gara Soultana hill and the El Haï valley (Za River tributary, Upper Moulouya catchment), where previous regional works mentioned pediments and conglomerates interpreted as fluvial terraces (Laouina, 1990; Muratet, 1991; Russo, 1927; Stretta, 1952; Wengler & Vernet, 1992) Associated with these landforms, several Acheulean to Neolithic archaeological findings were cited (Wengler & Vernet, 1992). These have been investigated since 2006 within the framework of a Spanish-Moroccan bilateral project undertaken in the Aïn Beni Mathar-Guefaït region (Jerada, Eastern Province) (Aouraghe et al, 2013; Sala-Ramos et al, 2017)

Methods

Results

Conclusion