Universität zu Köln

Bartz, Melanie (2018). Quaternary fluvial environments in NE Morocco inferred from geochronological and sedimentological investigations. PhD thesis, Universität zu Köln.

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Abstract

The investigation of fluvial archives in NE Morocco is of high interest for unravelling palaeoenvironmental changes linked to Quaternary climate fluctuations, long-term tectonic activity and/or human influence. The prehistoric site of Ifri n'Ammar is situated in NE Morocco and represents a key location in unravelling the history of anatomically modern humans (AMH) in northern Africa as it reveals Middle and Late Palaeolithic occupation phases since ~170 ka. Therefore, this study uses two fluvial systems of different nature – the ephemeral stream Wadi Selloum and the perennial Moulouya River – in order to reconstruct the varying environmental conditions for the last ~170 ka, the time when AMH started to disperse into the region. Both fluvial systems provide valuable insights into the geomorphic evolution of the study area. It has been shown that the two fluvial systems responded to different environmental triggers: the small catchment of the Wadi Selloum is highly affected by the sensitive ecosystem of the Mediterranean region. The ephemeral stream is characterised by a discontinuous and heterogeneous sediment record caused by short-term climatic shifts and human influence. In contrast, tectonic activity appears to be the main driver for the evolution of the lower Moulouya terraces, rather than climate cyclicity during the Quaternary. Establishing chronostratigraphies of river sedimentary sequences always remains challenging. However, based on different luminescence dating techniques (OSL, pIRIR, TL), electron spin resonance (ESR) dating using the multiple centres approach (Al and Ti centres of quartz), and palaeomagnetic analyses, geochronological frameworks for the two fluvial archives located in the direct vicinity of Ifri n'Ammar could successfully be established. First numerical ages in this area yield burial ages of the lower Moulouya terraces and the Wadi Selloum deposits dating back to Early Pleistocene and Late Pleistocene/Holocene times, respectively. In addition to the use of absolute and relative dating techniques, laboratory (sedimentology, geochemistry, mineralogy) and microscopic (micromorphology) analyses have been carried out in order to identify periods of enhanced flooding in both fluvial systems on the one hand, and periods of pedogenesis on the other. The Wadi Selloum gives information about morphodnamic phases in the time of AMH settling: periods of enhanced aggradation occurred around ~100 ka, ~75 ka, ~55 ka, after the LGM, and during the Holocene, whilst sedimentation ended after ~1.3 ka. Pedogenesis may be used as environmental indicator for more humid climate conditions during MIS 3 (palaeo-Calcisol), the early Holocene (Calcisol) and the late Holocene (Fluvisol). Although palaoenvironmental implications should be taken with caution due to the discontinuity of the ephemeral stream system, it appears that more humid and warmer climate conditions favoured human settling in this area. This study thus provides first insights into the palaeoenvironmental changes around the rock shelter of Ifri n'Ammar during the last glacial-interglacial cycle.

Item Type:	Thesis (PhD thesis)
Translated abstract:	Abstract Language The investigation of fluvial archives in NE Morocco is of high interest for unravelling palaeoenvironmental changes linked to Quaternary climate fluctuations, long-term tectonic activity and/or human influence. The prehistoric site of Ifri n'Ammar is situated in NE Morocco and represents a key location in unravelling the history of anatomically modern humans (AMH) in northern Africa as it reveals Middle and Late Palaeolithic occupation phases since ~170 ka. Therefore, this study uses two fluvial systems of different nature – the ephemeral stream Wadi Selloum and the perennial Moulouya River – in order to reconstruct the varying environmental conditions for the last ~170 ka, the time when AMH started to disperse into the region. Both fluvial systems provide valuable insights into the geomorphic evolution of the study area. It has been shown that the two fluvial systems responded to different environmental triggers: the small catchment of the Wadi Selloum is highly affected by the sensitive ecosystem of the Mediterranean region. The ephemeral stream is characterised by a discontinuous and heterogeneous sediment record caused by short-term climatic shifts and human influence. In contrast, tectonic activity appears to be the main driver for the evolution of the lower Moulouya terraces, rather than climate cyclicity during the Quaternary. Establishing chronostratigraphies of river sedimentary sequences always remains challenging. However, based on different luminescence dating techniques (OSL, pIRIR, TL), electron spin resonance (ESR) dating using the multiple centres approach (Al and Ti centres of quartz), and palaeomagnetic analyses, geochronological frameworks for the two fluvial archives located in the direct vicinity of Ifri n'Ammar could successfully be established. First numerical ages in this area yield burial ages of the lower Moulouya terraces and the Wadi Selloum deposits dating back to Early Pleistocene and Late Pleistocene/Holocene times, respectively. In addition to the use of absolute and relative dating techniques, laboratory (sedimentology, geochemistry, mineralogy) and microscopic (micromorphology) analyses have been carried out in order to identify periods of enhanced flooding in both fluvial systems on the one hand, and periods of pedogenesis on the other. The Wadi Selloum gives information about morphodnamic phases in the time of AMH settling: periods of enhanced aggradation occurred around ~100 ka, ~75 ka, ~55 ka, after the LGM, and during the Holocene, whilst sedimentation ended after ~1.3 ka. Pedogenesis may be used as environmental indicator for more humid climate conditions during MIS 3 (palaeo-Calcisol), the early Holocene (Calcisol) and the late Holocene (Fluvisol). Although palaoenvironmental implications should be taken with caution due to the discontinuity of the ephemeral stream system, it appears that more humid and warmer climate conditions favoured human settling in this area. This study thus provides first insights into the palaeoenvironmental changes around the rock shelter of Ifri n'Ammar during the last glacial-interglacial cycle. English Die Untersuchung von fluvialen Archiven ist in NO Marokko von großem Interesse für die Aufklärung von Paläoumweltveränderungen, die meist mit klimatischen Schwankungen, langfristiger tektonischer Aktivität und/oder menschlichem Einfluss im Quartär verbunden sind. Die prähistorische Höhle Ifri n'Ammar stellt in dieser Region eine Schlüsselstelle dar. Durch Mittel- und Spätpaläolithische Funde offenbart die archäologische Stätte Informationen über die Geschichte des Anatomisch Modernen Menschen (AMH) in den letzten ~170 ka. Aus diesem Grund werden in dieser Studie zwei fluviale Systeme unterschiedlicher Natur - der ephemere Wadi Selloum und der perennierende Fluss Moulouya – untersucht, um die wechselnden Umweltbedingungen für die letzten ~170 ka zu rekonstruieren, als AMH begannen die Region zu besiedeln. Beide fluvialen Systeme liefern wertvolle Erkenntnisse über die geomorphologische Entwicklung des Untersuchungsgebietes. Es wurde gezeigt, dass sie jeweils auf unterschiedliche Umweltauslöser reagieren: Das eher kleine Einzugsgebiet des Wadi Selloum ist stark von dem sensiblen Ökosystem des Mittelmeerraumes betroffen. Dies führt zu einem diskontinuierlichen und heterogenen Sediment-Archiv, was vor allem auf kurzzeitige klimatische Veränderungen und menschlichen Einfluss zurückzuführen ist. Im Gegensatz dazu scheint der Hauptantrieb für die Entwicklung der unteren Moulouya-Terrassen die tektonische Aktivität zu sein, während Klimaschwankungen im Laufe des Quartärs eine weit geringere Rolle spielten. Das Erstellen von Chronostratigraphien ist vor allem bei Fluss-Sediment-Sequenzen herausfordernd. Auf Basis unterschiedlicher Lumineszenz-Datierungstechniken (OSL, pIRIR, TL), Elektronenspinresonanz-Datierung (ESR) unter der Benutzung der Multizentren- Anwendung (Al- und Ti-Zentren in Quarz) und paläomagnetischen Analysen konnte ein geochronologischer Rahmen in beiden Fluvialarchiven erstellt werden. Die ersten absoluten Datierungen in dieser Region liefern Ablagerungsalter der unteren Moulouya-Terrassen im Frühpleistozän, während die Wadi Selloum Ablagerungen ins Spätpleistozän/Holozän zurück datieren. Neben der Anwendung von absoluten und relativen Datierungsverfahren wurden Labor- (Sedimentologie, Geochemie, Mineralogie) und mikroskopische (Mikromorphologie) Analysen durchgeführt, um in beiden fluvialen Systemen Perioden mit einerseits erhöhtem Abfluss und andererseits Bodenbildungsphasen zu identifizieren. Der Wadi Selloum gibt Auskunft über morphodynamische Phasen in der Zeit der AMH-Besiedlung: Perioden der verstärkten Aggradation traten um ~100 ka, ~75 ka, ~55 ka, nach dem Letzten Glazialen Maximum (LGM) und während des Holozäns auf, während die Sedimentation nach ~1.3 ka endete. Pedogenese zeichnet sich als Umweltindikator für feuchtere Klimabedingungen während des MIS 3 (Paläo-Calcisol), des frühen Holozäns (Calcisol) und des späten Holozäns (Fluvisol) aus. Obwohl durch die Diskontinuität des ephemeren Fluvialsystems die Interpretation von Paläolandschaften kritisch gesehen werden sollte, so scheint es, dass feuchte und wärmere Klimaverhältnisse die menschliche Besiedlung in dieser Region begünstigten. Aufgrund erster Umweltimplikationen in dieser Region gibt diese Studie erste Einblicke in Paläoumweltveränderungen in der direkten Umgebung von Ifri n'Ammar während des letzten Glazial-Interglazial Zyklus. German
Creators:	Creators Email ORCID ORCID Put Code Bartz, Melanie m.bartz@uni-koeln.de UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-79935
Date:	2018
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Geosciences > Geographisches Institut
Subjects:	Natural sciences and mathematics Earth sciences Geography and travel History of ancient world
Uncontrolled Keywords:	Keywords Language Morocco English luminescence dating English electron spin resonance dating English palaeoenvironment English
Date of oral exam:	4 July 2017
Referee:	Name Academic Title Brückner, Helmut Prof. Dr. Bubenzer, Olaf Prof. Dr.
Projects:	Sonderforschungsbereich 806 - Our way to Europe
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/7993