Sediment budgeting of short‐term backfilling processes: The erosional collapse of a Carolingian canal construction

Sediment budgeting concepts serve as quantification tools to decipher the erosion and accumulation processes within a catchment and help to understand these relocation processes through time. While sediment budgets are widely used in geomorphological catchment-based studies, such quantification approaches are rarely applied in geoarchaeological studies. The case of Charlemagne's summit canal (also known as Fossa Carolina) and its erosional collapse provides an example for which we can use this geomorphological concept and understand the abandonment of the Carolingian construction site. The Fossa Carolina is one of the largest hydro-engineering projects in Medieval Europe. It is situated in Southern Franconia (48.9876°N, 10.9267°E; Bavaria, southern Germany) between the Altmühl and Swabian Rezat rivers. It should have bridged the Central European watershed and connected the Rhine–Main and Danube river systems. According to our dendrochronological analyses and historical sources, the excavation and construction of the Carolingian canal took place in AD 792 and 793. Contemporary written sources describe an intense backfill of excavated sediment in autumn AD 793. This short-term erosion event has been proposed as the principal reason for the collapse and abandonment of the hydro-engineering project. We use subsurface data (drillings, archaeological excavations, and direct-push sensing) and geospatial data (a LiDAR digital terrain model (DTM), a pre-modern DTM, and a 3D model of the Fossa Carolina] for the identification and sediment budgeting of the backfills. Dendrochronological findings and radiocarbon ages of macro remains within the backfills give clear evidence for the erosional collapse of the canal project during or directly after the construction period. Moreover, our quantification approach allows the detection of the major sedimentary collapse zone. The exceedance of the manpower tipping point may have caused the abandonment of the entire construction site. The spatial distribution of the dendrochronological results indicates a north–south direction of the early medieval construction progress

High-Resolution Direct Push Sensing in Wetland Geoarchaeology—First Traces of Off-Site Construction Activities at the Fossa Carolina

Wetland environments, with their excellent conservation conditions, provide geoarchaeological archives of past human activities. However, the subsurface soil is difficult to access due to high groundwater tables, unstable sediments, and the high cost of excavation. In this study, we present a ground-based non- and minimal-invasive prospection concept adapted to the conditions of wetlands. We investigated the Fossa Carolina in South Germany, a canal that was intended in 792/793 AD by Charlemagne to bridge the Central European Watershed. Although the resulting Carolingian banks and the fairway with wooden revetments are very imposing, archaeological traces of off-site construction activities have not been identified hitherto. Based on a geophysically surveyed intensive linear magnetic anomaly parallel to the Carolingian canal, we aimed to prove potential off-site traces of Carolingian construction activities. In this context, we built up a high-resolution cross-section using highly depth-accurate direct push sensing and ground-truthing. Our results showed the exact geometry of the canal and the former banks. Thus, the magnetic mass anomaly could be clearly located between the buried organic-rich topsoil and the Carolingian banks. The thermoluminescence dating showed that the position of the magnetic mass anomaly reflected Carolingian activities during the construction phases, specifically due to heat exposure. Moreover, we found hints of the groundwater supply to the 5-metre wide navigable fairway

Early medieval fortifications: function and significance

Das Fränkische Reich erreichte unter Karl dem Großen seine weiteste Ausdehnung und hatte sich in Europa als weitere Großmacht neben dem Byzantinischen Reich, den Slawen und den Arabern etabliert. Der Burgenbau spielte hierbei eine entscheidende Rolle. Wie sahen diese Burgen aus, sowohl die Befestigung als auch die Innenbebauung und –struktur? Welche Funktionen hatten die Anlagen, gab es Veränderungen in Funktion und demgemäß Struktur, eventuell neue Funktionen oder neuartig gestaltete, strukturierte Burgen? Welche Rolle spielte der Burgenbau vom 7. bis 10. Jh. ‒ auch aufgrund der politisch-sozialen Entwicklungen? Diesen Fragen wird vor allem unter archäologischen Gesichtspunkten nachgegangen, ohne dabei die historische Gesamtsituation und deren regionale und überregionale Ursachen und Auswirkungen aus den Augen zu verlieren. In einem Überblick wird zunächst auf die zeitliche und geographische Entwicklung des frühmittelalterlichen Burgenbaus eingegangen. Der Hauptteil behandelt verschiedene wichtige Funktionen mit einschlägigen Beispielen: Burgen als administrative Zentralorte, als Refugien, zur Sicherung von Verkehrswegen, in militärischer Funktion, in der Bedeutung für den Bau von Pfalzen, als fortifikatorische Absicherung von Bistumssitzen sowie von Königs- und Klosterhöfen, als frühe Adelsburgen oder die Rolle der Burgen in frühterritorialen Landesherrschaften sowie im frühmittelalterlichen Landesausbau und zuletzt bei der Herausbildung und Befestigung von Städten. Das 10. Jh. stellt eine Blütezeit für den Burgen- und Befestigungsbau dar, der wie nie zuvor im Frühmittelalter vielschichtig und differenziert-multifunktional war. Darüber hinaus waren die Burgen immer auch ein Symbol der Macht bzw. Herrschaft als Ausdruck des adligen Schutzverständnisses mit repräsentativer Funktion.The Frankish Empire reached its greatest expanse under Charlemagne and became established as a great power next to the Byzantine Empire, the Slavs and the Moors. Thereby, the building of castles played an important role. What did these fortresses look like, their defence walls and the structures inside them? What functions did these complexes perform? Were there changes in the functions and with that in the structures? Did new functions or even newly structured complexes arise? What role did castle-building play in the 7th to 10th centuries, also in the light of political and social developments? These questions are pursued in this article, above all the archaeological aspects, yet without losing sight of the overall historical situation and its regional and transregional causes and effects. First an overview is made of the temporal and geographical development of early medieval castle-building. The main part then concerns different important functions using pertinent examples: castles as administrative centres, for refuge, for safeguarding travel routes, for military purposes; the importance of building a pfalz (temporary residence for travelling royal persons), as protection for bishop seats, royal estates and monasteries, as early aristocratic castles or fortification of land holdings and early medieval expansions, and finally the emergence and fortification of towns and cities. The great age of castle-building was in the 10th century, during which they became more multifaceted and differentiated than ever before. Castles were always a symbol of power and dominion, the expression of aristocratic protection with a representative function

: Études de castellologie médiévale

International audienceOuvrage en 3 langues: français, anglais, alleman

Inland harbours : First results and perspectives of the project Inland harbours in Central Europe on the French territory

International audienceInland harbours, essential links between the Mediterranean and Northern Europe, are the object of the Priority Program Studies of inland harbours in Central Europe as hubs for European communication networks, funded by the Deutsche Forschungsgemeinschaft (DFG). Since 2016, the project has also focused on the French inland river network, in association with the Friedrich-Schiller-University Jena (Germany) and the University of Burgundy (Dijon, France).Inland harbours can be perceived as multifaceted phenomena, based on comparative, diachronic, multidisciplinary analyses. The modes of harbour installation and the socio-economic processes are examined here, together with the management of waterways and the conditions for navigability, from the 1st century BC to the 15th century AD. The French GIS dataset was compiled to fit the existing database structure, which already contains data for Germany, Benelux, and Northern Italy. Although data distribution for France is still patchy, at this state of the project, our dataset can already be useful for many spatial and / or quantitative analyses. This paper therefore proposes, first, a critical overview of the database, and then a discussion of the type of analyses that can accommodate heterogeneous data. Various methods, including network analysis (Strahler order), and pattern analysis (focusing on the rhythm of appearance and abandonment of harbours), are used to examine the harbour phenomenon within the broader context of historical river uses, competing riverine activities, and reaction to climatic changes.Relais essentiel dans la communication entre Méditerranée et Europe du Nord, les ports des eaux intérieures (rivières et lacs) sont l’objet depuis plusieurs années du programme de recherche « Studies of inland harbours in Central Europe as hubs for European communication networks », financé par la Fondation Allemande pour la Recherche (DFG). En 2016, un nouveau volet, mené en collaboration entre l’Université Friedrich Schiller (Iéna, Allemagne) et l’Université de Bourgogne (Dijon, France), a été consacré à l’ensemble des eaux intérieures du territoire français.Sur la longue période envisagée, du 1er siècle avant notre ère à la fin du Moyen Âge, le projet s’intéresse aux modalités d’installation des ports, aux fonctionnements socio-économiques sous-jacents, à la gestion des cours d’eau et aux conditions de navigabilité. La compréhension de ces lieux, en tant que phénomènes complexes, se fonde ici sur une vaste analyse comparative, diachronique et pluridisciplinaire des sources relatives aux ports fluviaux et lacustres français. Intégrées à une base de données initiée dans le premier volet du projet sur l’Allemagne, le Benelux et l’Italie du Nord, ces données permettront d’envisager toute une variété d’analyses spatiales et / ou quantitatives. En l’état actuel du projet, les données sont encore très hétérogènes. Après une description critique de la base et de son contenu, cet article est l’occasion de tester différentes méthodes adaptées à des données disparates. L’utilisation de méthodes d’analyse des réseaux fluviaux (rang de Strahler) et la prise en compte des rythmes d’apparition / disparition des ports permettent de replacer le phénomène port dans le contexte plus large de l’exploitation des rivières, des questions de compétition sur cet espace stratégique, et de réactions aux évolutions du milieu naturel

River management strategies from Antiquity to Middle Ages: the contribution of harbours to the analysis ofcentral European communication networks

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Holocene overbank sedimentation in Central Europe between natural and human drivers - The Weiße Elster River (Central Germany)

Up to several meters thick fine-grained Holocene overbank deposits are ubiquitously found in most Western and Central European lowland floodplains. However, despite their large importance for the geomorphological and geoecological floodplain properties, the interplay of different possible causes for their formation are not well understood yet. Most authors suggest human-induced deforestation as the main precondition for sediment mobilization and transport from the slopes to the floodplain, whereas others suggest a stronger influence of climatic factors. This current research gap is caused by often missing well-resolved fluvial chronostratigraphies and spatio-temporal information about former human activity within the studied catchments. To fill this gap we exemplarily studied Holocene overbank sedimentation and possible human or natural drivers in the meso-scale Weiße Elster catchment in Central Germany. To do so, we applied numerical dating as well as sedimentological and micromorphological analyses to Holocene fluvial sediments along three floodplain transects. Furthermore, we built up an unprecedented systematic spatio-temporal database of former human activity within the catchment from the Neolithic until the Early Modern Ages. Together with published paleoclimatic data, this database allowed an unprecedented, systematic comparison of Holocene overbank sedimentation phases with possible external controls. Our data show that some overbank sedimentation phases were directly linked with human activities in the affected site sub-catchments, whereas others were not. Instead, all phases seemed to be linked with natural factors. This difference with most former studies could possibly be explained by previously often limited numerical dating of the fluvial sediments and by largely missing spatio-temporally well-resolved regional settlement records, hindering a precise temporal link of fluvial sedimentation with former human settlement. Furthermore, this difference could possibly also be explained by a relatively high natural sensitivity of the landscape dynamics in the Central German lowlands, showing a subcontinental climate, towards climatic external controls