Quaternary fluvial environments in NE Morocco inferred from geochronological and sedimentological investigations

Fluvial terrace formations of the Lower Moulouya River, showing three Holocene terraces as well as three distinct levels of Pleistocene fluvial deposits (view to the north).

Fluvial terrace formations of the Lower Moulouya River, showing three Holocene terraces as well as three distinct levels of Pleistocene fluvial deposits (view to the north).

Melanie Bartz is a PhD student in the C2 project “Early Holocene Contacts between Africa and Europe and their Palaeoenvironmental Context” of the CRC 806 “Our Way to Europe” of the University of Cologne, at the Institute of Geography supervised by Prof. H. Brückner.

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The prehistoric site of Ifri n’Ammar (NE Morocco), a rock shelter dated back to Middle and Late Palaeolithic times and characterised by periodic settling, reveals human activity since 170 ka. Fluvial systems provide direct information for the reconstruction of palaeoenvironmental changes; they also serve as indicators for the regional climate evolution.

Melanie Bartz, PhD Candidate in C2.

Melanie Bartz, PhD Candidate in C2.

In her PhD research, Melanie focuses on two fluvial systems of different scales to reconstruct palaeoenvironmental features in NE Morocco: (i) the ephemeral stream Wadi Selloum in the direct vicinity of Ifri n’Ammar, and (ii) on fluvial terraces of the larger Moulouya River drainage. The major tools to reach this goal are the application of geochronological techniques [luminescence (OSL, IRSL) and electron spin resonance (ESR) dating] as well as sedimentological analyses [e.g. micromorphology, scanning electron microscopy (SEM)].

(i) Wadi Selloum deposits have been dated between 102±8 ka and 1.3±0.2 ka, covering different morphodynamically stable and active phases, respectively. Periods of enhanced aggradation occurred ~100 ka, ~75 ka, ~55 ka, ~21 ka, and ~14 ka, as well as during the Holocene. Fine-grained overbank deposits were distinguished by high amounts of allochthonous minerals, such as quartz, K-feldspar and plagioclase, which indicate aeolian input into the limestone-dominated catchment. Landscape stability is evidenced by a Pleistocene palaeosol and two Holocene soils, characterised by the pronounced formation of soil structure, pedogenic calcite and frequent biogenic pedofeatures.

(ii) The Moulouya River drains an area characterised by crustal deformation during the Late Cenozoic. As a consequence of crustal shortening, contrasting fluvial environments occur on each side of a thrust zone: stacked terraces build up >37 m-thick aggradational deposits in the footwall, while a terrace staircase complex composed of at least three distinct levels form the hanging wall system. SEM analyses revealed a high contribution of fluvially transported mineral grains besides a minor contribution of aeolian input which gives information about the sediment history. ESR dating yielded ages of Early Pleistocene times.

This study provides first insights into the palaeoenvironment around the Ifri n’Ammar rock shelter during the Quaternary. By presenting the first numerical ages of fluvial records in this region, this project is a major contribution to unravelling the landscape evolution in the time of human occupation and even beyond.

Event Information:

Date, Time: 13/06/2016, 15:30 h – 16:15 h

Location: Room S12, Seminargebäude (Building 106), Universitätsstraße 37 , Cologne

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