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Geoarchaeological and chronometrical evidence of early human occupation on Lanzarote (Canary Islands)
(2003)
- Two desert loess–paleosol sequences in sediment traps were investigated using (pedo-) stratigraphy, sedimentology, soil mineralogy and IRSL dating. So far we cannot recognise significant IRSL age-underestimates from the polymineral fine-grain fraction of our samples. We establish a first palaeoclimatic sequence spanning the past ca 200 ka which can be compared to data from other Canary Islands and surrounding areas, including terrestrial and deep sea records. More humid phases on Lanzarote are apparently triggered by Milankovich forcing, but the climate remained semi-arid to arid all over the past 200 ka. The onset of human occupation of the island during a slightly moister period is bracketed between 5 and 10 ka, based on the occurrence of archaeosediments containing bones of ovicaprid. This is the first proof of much earlier occupation than witnessed so far from archaeological records. The early subsidiary economy had a strong impact on soil stability and landscape shaping of the island.
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Response to the „Comment on ’Geoarchaeological and chronometrical evidence …’ ” by J.C. Carracedo et al.
(2004)
- This paper is a reply to the comments made by Carracedo et al. (Quaternary Science Reviews 23, 2045-2049) to the original paper by Zöller, L., Suchodoletz, H.von & N. Küster (2003): Geoarchaeological and chronometrical evidence of early human occupation on Lanzarote (Canary Islands), Quaternary Science Reviews 22, 1299-1307. The reply copes with comments concerning chronometrical dating, the origin of investigated material and geomorphologic and geoarchaeologic problems.
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Soil moisture fluctuations recorded in Saharan dust deposits on Lanzarote (CanaryIslands) over the last 180 ka
(2010)
- Aeolian sediments trapped in volcanically dammed valleys on Lanzarote, Canary Islands, were investigated in order to reveal environmental changes over the last 180 ka. Clay content and frequency dependent magnetic susceptibility were used as proxies for pedogenesis and palaeo-soil moisture. During the last 180 ka, these proxies showed a general pattern of enhanced soil moisture during glacials and stadials and more arid conditions during interglacials and interstadials. Comparisons of these results with proxies from regional palaeoclimate studies identified a positive correlation with proxies of trade wind strength off northwest Africa and inverse correlations with both sea surface temperatures in the northeast Atlantic and the extent of Mediterranean vegetation. Possible causes for the observed pattern include a glacial enhancement of precipitation from westerly cyclones, a change in relative humidity due to fluctuating air temperatures and an occasional influence of the African summer monsoon. Although it is not yet possible to clearly differentiate among these factors, it is clear that the first two factors must have been primarily dominant. These results represent the first quasi-continuous terrestrial data testifying to environmental changes in the northwest African coastal area for the last 180 ka and complement the abundant data derived from marine cores of the region. High latitude dynamics had a major influence in this area and were intermediated by North Atlantic sea surface temperatures. A possible negative correlation can also be observed with the orbital obliquity cycle with a 10 ka time lag, which is similar to the lag recorded from North Atlantic sea surface temperatures.
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The evolution of Saharan dust input on Lanzarote (Canary Islands) – influenced by human activity in the Northwest Sahara during the early Holocene?
(2009)
- An overall Holocene increase of Saharan dust input to the Canary Islands and to the North Canary Basin is accompanied by a strong coarsening of Saharan dust in loess-like sediments deposited on Lanzarote from ~7–8 ka. No similar coarsening events are indicated in investigations of the sedimentological record for the last 180 ka, a period showing several dramatic climate changes. Therefore a mobilisation of Holocene dust by anthropogenic activity in the northwest Sahara east of the Canary Islands is assumed. Although scarce archaeological data from the coastal area of that region does not point to strong anthropogenic activity during the early Holocene, a high density of unexplored archaeological remains is reported from the coastal hinterlands in the Western Sahara. Thus, the hypothesis of early anthropogenic activity cannot be excluded.
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Loess-like and palaeosol sediments from Lanzarote (Canary Islands/Spain) —Indicators of palaeoenvironmental change during the Late Quaternary
(2009)
- On Lanzarote (Canary Islands) Quaternary Saharan dust and weathered local volcanic material were trapped in Miocence to Pliocene valleys dammed by younger volcanic edifices. These sediments show sequences of alternating reddish/clayey and loess-like yellowish/silty material. In order to investigate if reddish/clayey layers contain material derived from local pedogenesis and if so, which pedogenetic processes were active, we performed sedimentological, micromorphological and environmental magnetic analyses. The analyses demonstrate that these layers contain material derived from local soils. These soils were characterised by clay formation, rubefication and the formation of superparamagnetic particles during periods of enhanced soil moisture. Thus, they can serve as natural archives in order to reconstruct the terrestrial palaeoclimatic history of Lanzarote. The distribution of soil material in the profiles shows that cold periods of the Late Quaternary were characterised by more humid conditions than today. Using palaeontological remains and a comparison with recent soils on Tenerife, we can roughly estimate maximal palaeoprecipitation values during more humid periods.
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Dating Saharan dust deposits on Lanzarote (Canary Islands) by luminescence dating techniques and their implication for palaeoclimate reconstruction of NW Africa.
(2008)
- Lava flow dammed valleys (Vegas) on Lanzarote (Canary Islands) represent unique sediment traps, filled with autochthonous volcanic material and allochthonous Saharan dust. These sediments and the intercalated palaeosoil sediments document past environmental change of the last glacial-interglacial cycles, both on Lanzarote and in NW Africa. A reliable chronology must be established to use these sediment archives for palaeoclimate reconstructions. Owing to the lack of organic material and the limiting time range of the 14Cdating method, luminescence dating is the most promising method for these sediments. However, the fluvio-eolian character of these sediments is a major problem for luminescence dating, because these sediments are prone to insufficient resetting of the parent luminescence signal (bleaching) prior to sedimentation. To check for the best age estimates, we compare the bleaching behavior of (1) different grain sizes (coarse- versus fine-grain quartz OSL) and (2) different minerals (fine-grain feldspar IRSL versus fine-grain quartz OSL). The results show that owing to its bleaching characteristics, quartz is the preferable mineral for luminescence dating. On the basis of the fine- and coarse-grain quartz OSL age estimates, a chronostratigraphy up to 100 ka could be established. Beyond this age limit for OSL quartz, the chronostratigraphy could be extended up to 180 ka by correlating the vega sediments with dated marine sediment archives.
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Geomorphological investigations of sediment traps on Lanzarote (Canary Islands) as a key for the interpretation of a palaeoclimate archive off NW Africa
(2009)
- On Lanzarote (Canary Islands) Late Quaternary Saharan dust and volcanic material were trapped in Miocence to Pliocene valleys dammed by volcanic lava flows. These trapped sediments are potentially interesting as they can be natural archives useful to reconstruct the terrestrial palaeoclimate history of the NW African margin. Nevertheless, slope wash processes altered the primarily eolian deposits, making climatic interpretation not straightforward. Geomorphological mapping, GIS calculations and sedimentological investigations were used to unravel these processes influencing the temporal resolution of the palaeoclimatic archive, demonstrating that they average the palaeoclimatic signal by some ka. Thus, despite the colluvial geomorphic environment, the valley fillings can be used for palaeoclimatic interpretation of events with a length of at least some ka. The youngest sediments, deposited since at least 2.5 ka, are anthropogenically triggered and thus cannot be used for palaeoclimatic interpretation. The results show that the input of Saharan dust at Lanzarote increased during the last 1.0 Ma and especially during the Early/Middle Holocene.
