Landscape evolution and Paleoclimate

The main objective is to understand the processes that have shaped the actual landscape and its recent evolution (Tertiary-Quaternary) in NW Africa, including the exhumation/denudation history, paleo-stress/strain field and basins evolution, and the reconstruction of extreme climate events at millennium scales.

Beneficiary/Participant Organisations



Head of working group

 Landscape evolution and paleoclimate

Ali Azdimoussa (UMPO) & Philippe Münch (UM)

Task 2.1: Kinematics and timing of the major tectonic structures

Ahmed Chalouan & Michel Corsini (CNRS)

Task 2.2: Exhumation history of the Rif-Tell Belt

Ali Azdimoussa (UMPO)Philippe Münch (UM2)Antonio Jabaloy (UGR-CSIC)

Task 2.3: Basin Analysis: (i) Analysis of subsidence/uplift processes in Neogene basins (ii) Investigation of late Cretaceous-Paleogene basins

Abdelkhalek Ben Moussa (UAE)Mustapha Bensalah (UABT), Jean Jacques Cornée (UM),  José Fernando Borges (UEVORA)Mohamed Marzoqí (UCAM)

Task 2.4: Paleolatitude reconstruction of the rift Mountain

Séverine Fauquette (UM) & Laila Rhazi (UHC2)

Task 2.5: Constraining Western Mediterranean extreme floods and storms during the last millennium

Laurent Dezileau (UM2)Maria Snoussi (UM5)Néjib Kallel (SFAX).

Description of work

Task 2.1 : Kinematics and timing of the major tectonic structures: To determine the kinematics and timing of the major tectonic structures associated with the South-Alborán African margin evolution. In particular, the 40Ar/39Ar dating method on synkinematic white micas allows determining precise ages of shear-zone deformation under low temperature conditions. We will combine structural, petrological and geochronological approaches to constrain the tectonic evolution and uplift processes in the Rif-Tell Belt since the Miocene. This will include: (i) detailed mapping and structural analysis along selected N-S and E-W cross sections to identify the recent fault systems and related stress field; (ii) petrological studies of the main mylonitic zones to quantify the vertical displacements associated with the evolution of the tectonic structures; and (iii) 40Ar-39Ar laser probe dating via step heating of neoformed phengite and gouges from low temperature shear zones to constrain the timing of exhumation.

Task 2.2: Exhumation history of the Rif-Tell Belt: We will carry out He and AFT dating on samples from the different structural units of the metamorphic basement, in order to evaluate the possible differences in their exhumation histories. Preliminary results have already been obtained but are restricted to the Alborán domain. The aim of this approach is to identify the major tectonic contacts controlling the exhumation and the importance of tectonic inheritance. The recent exhumation associated with the South-Alborán African margin formation will be approximated by studying profiles roughly perpendicular to the coastline. Detrital thermochronology will be applied locally on "post-thrust" sediments to quantify Neogene exhumation rates of their sources.

Task 2.3: Basin Analysis: (i) Analysis of subsidence/uplift processes in Neogene basins: To constrain the vertical motions that have occurred during the last 10 Ma using basin analysis, notably the Neogene subsidence and the Pleistocene to recent uplifts. The subsidence history will be estimated by combining sedimentological and paleobathymetric changes in accurate chronological frames constrained by 40Ar-39Ar dating of volcanic ash layers and planktonic calcareous biostratigraphy; (ii) Investigation of late Cretaceous-Paleogene basins: To constrain the origin and paleo-environmental conditions of basins through detailed sedimentological, structural and geochemical studies in close association with Task 4.1.

Task 2.4: Palaeoaltitude reconstruction of the Rif Mountain: To reconstruct the palaeoaltitudes of the Rift Mountain at different time-slices since 10 Ma from pollen data sampled in the same Neogene sedimentary basins. Palynology is an excellent tool for palaeoaltitude estimates since the sedimentary basins receive from surrounding mountains terrains, along with detritic inputs from rivers, a large amount of pollen grains representative of all vegetation belts of the catchment area. The palaeoaltitude reconstruction method established by MEDYNA researchers takes into account pollen floras expanded near the coastline, the modern distribution of plants, palaeotemperature estimated at low altitude using the “Climatic Amplitude” method and a standard relationship between the latitudinal and altitudinal thermic gradients. Our preliminary works performed on the Nador borehole have demonstrated the feasibility of this approach in northern Morocco. These reconstructions require the calibration of sub-modern pollen data vs. altitude estimates. Sub-modern pollen data will be sampled at different altitudes in the Rif. Pollen sequences obtained from these sites will allow the reconstruction of the natural (before human impacts) vegetation and the climate altitudinal gradients for recent times (<10,000 years). Moreover, a series of surface samples taken along the altitudinal gradient will also be analyzed. All this data, both from Holocene sequences and modern samples, will constitute a valuable basis for Neogene vegetation and palaeoaltitude reconstructions.

Task 2.5: Constraining Western Mediterranean extreme floods and storms during the last millennium:  There is an increasing concern that extreme climatic events may be changing in frequency and intensity in the context of future climate change. Storms and floods have long been a threat for the western Mediterranean coast but their link with climate variability is not well understood. This is partly due to the fact that extreme events are inherently rare and difficult to observe in the period of a human life and to the lack of long-term observations or palaeo-reconstructions. This task will focus on the western African-Mediterranean coastal region (i.e. Morocco-Tunisia) that is particularly sensitive to erosion/submersion during storm events and has societal issues in terms of flood risks. It will combine palaeo-data and model simulations to (i) document the occurrence of extreme events (floods and storms) that have impacted selected lagoon sites of the western Mediterranean during the last millennium, (ii) investigate the relationship between these events and climate variability and trends; and (iii) compare reconstructed climatic series to simulations developed on the coupled climatic models (e.g., ARPEGE-NEMO, IPSL) in order to  investigate the mechanisms triggering extreme events and to develop simulations of future scenarios to tentatively assess the extreme flood and storm probabilities in the future.