Armin Volkmann, "Siedlung-Klima-Migrationen: Geoarchäologische Forschungen zur Oderregion zwischen 700 vor und 1000 nach Chr. mit Fokus auf der Völkerwanderungszeit":

https://www.academia.edu/1495365/Sie...wanderungszeit

"(...) In the context of the study, an analysis in a GIS of sites from the Iron Age to the Early Middle Ages was applied to the River Oder Region. A site catchment analysis of the topographical setting, the soil and broader parameters was conducted as a GIS examination. In this the spatial data information in a probable operating radius around the respective settlements of the individual periods was collected and evaluated statistically. In this way, statistically significant climate proxies on the relative humidity index and temperature pattern of the paleoclimate could be demonstrated. Through the use of weighted average means it was possible to describe climate signals of the compared periods. The quantitative analysis of the data of more than 500 finding sites allows identifying significant signals. As a result I found out that at the end of the Iron Age and at the beginning of the migration period, dramatic climate fluctuations are recognized. The climate fluctuations are the main reason for emigration out of this region. In the migration period, and again at the end of the Iron Age, the region was virtually uninhabited for 250 years. The data from the site catchment analysis is in a next step the base for a predictive modeling with has clearly defined areas of high and low probabilities of finding sites. A site catchment analysis of the topographical setting, the soil and broader parameters was conducted as a GIS examination, in which the spatial data information in a probable operating radius around the respective settlements of the individual periods was collected and evaluated statistically. In this way, statistically significant climate proxies on the relative humidity index and temperature pattern of the paleoclimate could be demonstrated. In addition, the deciding location factors of the soil and the geoecological environment of the settlement as well as distortionary anthropogenic and natural superimpositions were discussed. The ecological indicator values were rearranged into concise categories in a transformation process in consideration of their usability and informative value for matters concerning prehistoric, agronomically orientated cultures and checked for climate signals. The identified climate signals do not represent absolute data, but rather indirect, relative data, which permit comparative statements concerning the previous and subsequent level. With the use of comparative climate research, palynology, dendrochronology, the status of glaciers, river levels and models of paleotemperature, the climate signals that were produced in the context of the GIS environmental analysis could be verified. In this way, the probability and concision of the environmental analysis developed here and its particularly detailed chronological value were substantiated. The final step of the GIS analysis is based on Voronoi diagrams of the sites mapped as prehistoric space models. They show concepts of space in time. In a cartographic reconstruction of settlement clusters, the relationship between the anthropogenically influenced agricultural area and extensive natural forest areas was visualised. These methods are a part for the predictive modeling to clarify for example the most interesting regions of the settlements in the migration period. In the early Migration Period (D), the climate worsened dramatically and weather became very cool and dry in the course of only a few decades. Very poor conditions for land cultivation and animal husbandry resulted from this, which withdrew their livelihood in many places from the Germanic groups engaged in subsistence agriculture. On this limited scale, this could be buffered by more intensive trade, like the piled material found on the site and documented by geomorphology on the aforementioned trade and transit routes Settlements in micro regional favoured areas with a guaranteed supply of water such as kettle lakes, for example, could continue to exist. Spatial analysis of settlements shows a strong shrinking of the settlement clusters to remaining areas in which agricultural activity was still possible. Thus, there is a great disparity of a juxtaposition of extremely unequal small scale economic potential, which led to the widespread disintegration of settlement clusters and the accompanying dismantling of settlements in the subsequent late Migration Period (E). Simultaneously, the areas of the extensive natural, potential forest communities that are not influenced by humans increased greatly, whereas in Period E only “islands of remnant settlements” still existed in the surrounding woodlands. These types of settlements are the same as those identified in the late Roman Iron Age, but they have degenerated to a very large extent. Likewise, the parallels in construction are striking, where long houses that were used by a larger settlement community, are very rare. In contrast, smaller residential buildings or barns and storage sheds are frequently in post construction as well as upright and probably log construction, which were used by smaller family alliances, often as individual hamlets. In this way, the Germanic emigration from the Oder region is to be viewed as being organised into at least three main phases: 1. Already in the late Roman Iron Age there was a substantial migration in spite of the moist, warm climate of the favourable phase, which was triggered by the political weakness of the Roman Empire (the so-called imperial crisis of the soldier emperor with the fall of the Upper Germanic and Rhaetian Limes in 254 AD and the subsequent withdrawal of the border in the Rhine and Danube area) in the 3rd century AD and the related opportunities for plundering. This pulling effect of the Roman Empire which was rocked by crisis continued as a domino effect into the eastern Barbaricum in the Oder area. The Germanic migration is not just to be viewed as pointing to the southwest, however, as some Germanic people turned back again in a single cycle, as individual groups with particularly valuable pieces of furniture in late Germanic burial grounds clarify (the so-called “princely grave group of the Haßleben-Leuna- Häven type”). 2. In the early Migration Period, there is a dramatic worsening of the climate, which withdrew the foundation of the subsistence economy from large sections of the population which were characterized by agriculture. However, the political circumstances of the declining Roman Empire with the possibilities of seizing land and the existence of continuing opportunities to plunder increased the very intense migration of the late Germanic population from the Oder, mainly from Period D2, as numerous find sites from Period D1 are known. The high density of settlements in the moist Spree-Havel region, which was used as an intermediate stage in the south-westerly direction of the wave of migration is noticeable. The magnetic effect of the Roman Empire with its impressive, high-quality cultural assets in combination with the worsening climate in Barbaricum triggered an economically orientated wave of migration, which reached its peak in the 5th century AD (due to the simultaneous, political and military weakness of the-Roman Empire). Thus, undoubtedly, there was a heightened potential for conflict at the peak of the drought period, as is revealed by the incursions of Germanic peoples into the Roman Empire. 3. Despite the sharp rise in rainfall numbers in the late Migration Period (Period E), there was no certainty that grain could be harvested in the Oder region, as, on the one hand, the further reaching climate instability did not facilitate this due to torrential rain followed by temporary periods of drought and as, on the other hand, it must be assumed that there was an immense loss of expertise due to the preceding migration, particularly of the elite, younger and flexible sectors of the population. These problems were intensified even more by the heavy encroachment of scrub and the reforestation or partial desertification of the agricultural areas that were previously forsaken during Period D, as there was no potential labour force available for the agronomic re-cultivation of these fallow lands for labour intensive forest clearance measures (e.g. due to a positive population balance or birth surplus). Now, due to the relative increase in humidity as well, the Spree-Havel area, which had proven to be a favoured settlement area during the dry phase of Period D2, was of no agronomic interest. Up until Period E2 there was an almost complete dismantling of settlements in that area. Only in the northern part of the area being studied, an isolated remnant of the Germanic population whose economic basis is to be viewed as being linked to trade with Scandinavia to compensate for its non-productive agriculture is still also sporadically tangible in the 7th century AD (Period E3). In addition to that, however, all “remnants of Germanic traces” are located in only one diagonal strip of the very fertile marly soil which runs from north to south and is composed of a greatly varied biogeographical potential, which enabled flexible agriculture to be the primary source of income. The site where heaped material was found on both sides of the Oder in regions where there is black earth, with the most fertile soils and above all, an optimal groundwater level is of note. In addition, outside of the area under examination, as in the Magdeburger Börde, in the Thuringian Basin (Thüringer Becken) or in the Wetterau, an elevated incidence of finds from Period E is to be noted in these basin landscapes that are moulded by a relatively dry continental climate. There is a clear connection between the spatial distribution of the black earth and the late Migration Period sites. The time of the earliest Slavic immigration is to be dated in river Oder region not before 700 AD. (...)"