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| Titel |
Speleothem Reconstruction of Moroccan Climate: from the Strait to the Sahara |
| VerfasserIn |
J. J. Barrott, C. C. Day, R. N. E. Barton, A. Bouzouggar, G. M. Henderson |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250069846
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| Zusammenfassung |
| Located at the triple junction of climate regimes associated with the North Atlantic, the
Mediterranean and the Sahara desert, Morocco has been subject to fluctuations of climate on
multiple time-scales. However, the past temporal and regional variation in climate
arising from interplay of these regimes is currently poorly understood. Elucidating
where, when and how climate change has occurred holds great importance, not
only for understanding how these regimes may respond to a changing climate in
future, but also how past changes may have influenced prehistoric populations in the
area.
We present speleothem records from highly contrasting climatic regions both north and
south of the Atlas Mountains (a major topographic and climatic divide and effectively the
northern boundary of the Sahara Desert) to assess the past shifting of climate boundaries, to
investigate the impact of such climatic shifts on prehistoric populations, and to elucidate
controls on climate at the Atlas/Sahara boundary.
On the Strait of Gibraltar, at the gateway of the Mediterranean and North Atlantic, Ghar
Cahal (5Ë 25′ W, 35Ë 52′ N) provides palaeoclimate data that is directly comparable to the
archaeological record within the site and relevant to the many archaeological sites found
along the northern coastline. High-resolution, mid-Holocene stable isotope results reveal
multiple large shifts in δ18O (~1.5 per mil), and a cyclical variation (no shifts) in δ13C. A
lack of correlation between the δ18O and δ13C profiles suggests minimal kinetic
fractionation and therefore provides greater confidence in the potential for palaeoclimate
reconstruction. Ongoing trace element analysis will aid interpretation of the stable isotope
data.
South of the Atlas Mountains, we sampled from sites near Ouarzazate (30Ë N) and
Er-Rachidia (32Ë N) in the southwest and southeast respectively. Caves from both sites are
heavily decorated despite arid (SW) and hyper-arid (SE) modern-day conditions. This
presence of past speleothem deposition is itself a robust indicator of significant shifts in
regional climate and is assessed here by the U-Th dating of growth periods. Preliminary
chronology indicates coeval growth in the N, SE and SW during the mid-Holocene,
signifying a potentially widespread pluvial phase. Sample Gar-1 (MegaMite) from the SE
shows episodic growth since MIS 10, with deposition occurring predominantly during
interglacials. Stable isotope analysis of these samples will enable the investigation of
hypotheses regarding potential moisture pathways, providing insight into the source of
and controls on precipitation at the currently arid northern fringe of the Sahara. |
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