Geoarchaeology

The Bakırçay valley is one of the large east-west trending graben landscapes in western Anatolia. The ruins of Pergamon (modern Bergama), situated at the northern fringe of the valley, are the most outstanding example of the numerous archaeological sites within this old cultural landscape. The Bakırçay valley has not yet been studied from the paleogeographical and geoarchaeological points of view. This study aims at the reconstruction of the middle to late Holocene landscape development in the western hinterland of Pergamon and thus of the western Bakırçay valley. Furthermore, interactions between landscape changes, human settlement and land use activity are investigated. Geomorphological, sedimentological, and geophysical investigations are coupled with archaeological research with close cooperation between the DFG (German Research Foundation) cluster of Excellence Topoi, the Pergamon excavation of the German Archaeological Institute and the DFG Priority Programme 1209 ‘The Hellenistic polis as a living space’.
Three select landscape compartments of the western Bakırçay valley were investigated in detailed case studies: (i) The surroundings of the ancient polis of Atarneus, a hilltop settlement near the Aegean coast. (ii) The valley of the Geyikli, the westernmost perennial tributary of the Bakırçay. (iii) The environs of the archaeological site ‘Teut114’ with buried wall structures of unknown function in the central Bakırçay valley.
These case studies revealed approximately four millennia of the landscape and settlement history of the Bakırçay valley. The landscape was remarkably stable during this period. (i) The sedimentary plains surrounding the settlement hill of Atarneus were aggraded by braided and meandering rivers. Colluviation and alluvial fan deposition occurred at the foot-slopes. Sedimentation totalled approximately 5 to 7 m, showing evidence of a “drowning” of the landscape in terrestrial sediments. In general, the depositional system did not change. This striking resistance to the changing settlement and land use intensity is an effect of the modification of the slopes through terracing that countervailed erosion and likewise increased the buffering capacity of sediment storage on the slopes. There is no evidence that landscape deterioration contributed to the abandonment of Atarneus. Rather, socio-economic factors were crucial for the rise and fall. (ii) The Lower Geyikli Valley was inhabited by a braided river with a highly dynamic depositional system. Sedimentation totalled approximately 4 to 6 m. Only in recent times, gravel mining has led to a deformation of the valley floor, and the Geyikli’s fluvial terrace has become inactive. (iii) In the middle Holocene, the site ‘Teut114’ was situated on a depositional piedmont plain, which was protected from the annual Bakırçay floods. Over the past two millennia, the Bakırçay flood plain was continuously aggraded, and the site became prone to flooding.

En région aride comme ailleurs, les besoins en eau des
hommes comme de la plupart des animaux d’élevage sont
quotidiens. Les nomades et leurs troupeaux peuvent résoudre
le problème en se déplaçant de manière à s’abreuver à des
points d’eau, sous réserve que ces derniers ne soient pas
trop distants. Quant aux populations sédentaires, liées à la
terre, elles doivent pourvoir à ces besoins sur place 1.
En région steppique, l’offre de la nature est, sur ce
plan, réduite et ne répond que peu à ces exigences pourtant
vitales. Dans les Marges arides de la Syrie du Nord, le
climat méditerranéen, dégradé 2, se traduit par une longue
saison chaude (5 à 6 mois, parfois plus) privée de pluies,
alors que l’évapotranspiration potentielle atteint des valeurs
très largement supérieures au total des précipitations. Sous
des sols souvent minces et érodés, les substrats géologiques
et les formations superficielles y sont généralement peu
aptes à la rétention des eaux, soit du fait de leur capacité
d’absorption (chapes basaltiques fissurées, couvertures
alluvio-colluviales), soit du fait de leur compacité
(affleurement de roches massives, dalles superficielles
cimentées). Dans les deux cas, le ruissellement à la surface
est limité dans l’espace et, surtout, dans le temps.
L’accès direct à l’eau libre est donc restreint à de rares
points (sources) ou à de brefs moments (crues d’oueds
ordinairement secs), voire à des lieux où cette eau se révèle
inutilisable parce que salée (lacs salés ou sebkhas). La
répartition spatiale de ces accès à l’eau se révèle enfin très
irrégulière, laissant de vastes secteurs impropres à l’installation
humaine du fait de l’indigence des ressources directes.
Afin de répondre aux exigences alimentaires
quotidiennes, il faut donc, en l’absence de ressource
suffisante, être en mesure d’accéder aux réserves naturelles
souterraines (puits) ou de stocker l’eau des précipitations. Ce
stockage peut être réalisé sur les pentes (mares aménagées,
citernes, etc.) ou dans les talwegs (barrages, birkés, etc.).

Four samples were dated by luminescence in the Cologne Luminescence Laboratory (CLL) to provide information on the geochronological context
of an earth oven exposed on a tidal flat close to Katka in the south eastern Sundarbans, Bangladesh. Optically stimulated luminescence (OSL) on
quartz was used to determine the last heating of the oven walls to more than 400 °C. This temperature is assumed to thermally erase the natural
luminescence signal of the sediments and to reset the luminescence clock to zero. Samples were taken from the oven walls using metal cylinders
and then prepared for OSL quartz measurements. Two different grain sizes (4-11 and 40-63 μm) were prepared to elaborate the influence of the
thermal resetting to the signal intensities and the precision of the equivalent dose (De) determination.

Siliceous scoria droplets, measuring from 1 to 10 mm, from one late Pleistocene and four early Holocene archaeological sites in northern Syria are compared to similar droplets previously suggested to be the result of a cosmic impact at the onset of the Younger Dryas global cooling event. The findings demonstrate that the presence of siliceous scoria droplets are independent of age and thus are not specific to the beginning of the Younger Dryas. Occurrences have not been reported from natural deposits, but are instead associated with buildings destroyed by fire and thus appear to be restricted to archaeological sites. We therefore conclude that melting of building earth in ancient settlements can occur during fires reaching modest temperatures. There is no evidence to suggest that siliceous scoria droplets result from very high temperature melting of soil and are the result of a cosmic event.

Jackson, D., R. Seguel, C. Méndez, A. Maldonado, I. Murillo, L. Núñez 2014. Geoarqueología en ambientes costeros y paisajes patrimoniales de la costa del Choapa. Guía de campo: II Taller de Geoarqueología de América Latina, editado por: R. Seguel y D. Jackson. 125 pp. (Producto del proyecto FONDECYT 1140824).