Geology A Floating Stronghold

In the Middle Ages, nature influenced human settlements, which in turn affected the surrounding landscape. Experts View of the “island” have turned to an early medieval village in to learn – the stronghold in Santok, during the more about this intricate relationship. spring 2011 flood.

Dr. Kinga Zamelska-Monczak ries) history of fortified settlements found in archaeo- logical and written sources, may become a key site for PAS Institute of Archeology our understanding of life in the Middle Ages. and Ethnology, Centre for Prehistoric Analyzing the historic landscape requires a wide and Medieval Studies in Poznań range of studies in the fields of geology, geomorphol- ogy, hydrology and paleogeography. Geological field- Dr. Andrzej Piotrowski work was carried out in addition to archaeological Dr. Kinga Paweł Sydor research, including 2D and 3D geophysical sequences Zamelska-Monczak and 60 boreholes and trenches. Hundreds of samples (PhD) Polish Geological Institute were taken from the obtained drill cores for laboratory is an archaeologist – National Research Institute in Warsaw studying early Middle analyses, such as grain-size analysis to determine the Ages in Greater , strength of the river current, as well as paleontological especially the and pollen analysis providing information about the north-west region, environmental conditions at that time, including the with particular focus temperature and water depth, vegetation, and floods. on the boundary areas. She has been nvironmental conditions and the relationship Radiocarbon dating (AMS method) was used for ab- conducting research between man and nature in the early Middle solute dating of archaeological artifacts and geological in Santok since 2007. EAges have been of interest to archaeologists for a long samples. kinga.zamelska@ time. Research on this issue has been carried out in iaepan.poznan.pl the north-west region of . The site of The Beginning the early medieval village in Santok is located in the Gorzów Basin, at the confluence of the and The geological structure of the area is very import- Noteć rivers. This hamlet, due to its characteristic lo- ant for landscape reconstruction of a given period, cation and the centuries-long (eighth-fifteenth centu- as it underpins the development of natural and so-

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Santok on the geological Explanations of lithology: map of Poland on a scale • Holocene: (3) fluvial sands, gravels and peats; (15) kame sands and silts, • Wi – range of the Leszno Phase of the Vistula of 1:500,000. • undivided Quaternary: (5) aeolian sands; (17) end moraine gravels, sandsm boulders Glaciation; Based on: Geological map • Pleistocene: and tills, • Po – range of the Poznań Phase of the Vistula of Poland on a scale – North Polish Glaciation: (18) tills; Glaciation; of 1:500,000, Leszek Marks, (11) fluvial sands and gravels, • – South Polish Glaciation: (33) end moraine • Go-Cho – range of the Gorzów-Chodzież Andrzej Ber, Waldemar Gogołek, (12) lake sands and silts, gravels, sands, boulders and tills; Sub-phase of the Vistula Glaciation; Krystyna Piotrowska (13) ice-dam clays, silts and sands, • Miocene: (39) clays, silts, sands, gravels with • Pm – range of the Pomeranian Phase of the (Warsaw 2006). (14) outwash sands and gravels, lignite; Vistula Glaciation.

cial processes. The landscape sets the backdrop both water flows similar to those of the present-day Volga for interdependent natural processes and for human River – with the width of the river flowing through activity. The multidisciplinary studies carried out so the glacial valley reaching 24‒33 km during the spring far have helped to recognize the processes shaping flooding period. the landscape around Santok. Today we know that Due to its location, for the next several thousand it was formed after the deglaciation of ice sheet of years after the glaciation subsided, the Gorzów Basin, the Poznań Phase of the Vistulian Glaciation. This as well as Santok (located at a place where the valley is “zero hour” of the Gorzów Basin landscape. The narrows to 17 km across), underwent intensive pro- Gorzów Basin itself belongs to an ancient glacial val- cesses of landscape modification. After the formation ley, running parallel to it, a vast and longest valley in of the Oderbruch by the plateaus of the Pomerani- the European Lowlands, where waters flowed from an Phase, the Gorzów Basin entered the next stage the Grodno area to the Atlantic. This valley, known as of landscaping, from then on shaped only by river the Toruń–Eberswalde ice-marginal valley, once saw flows. Preliminary research shows, however, that the

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rising levels of the Ancylus Lake, then the Baltic Sea, Warta to east of the village. The regulation of river at the end of the glacial period influenced erosive and channels and the construction of levees at the turn of accumulative processes occurring far inland. the eighteenth and nineteenth centuries completed the The first stage was marked by a multi-channel shaping of the landscape and hydrological conditions. braided river, linked to the low erosion base of the The hydrological conditions in Santok, both then Baltic Ice Lake. Deep erosions dominated at that time, and now, were quite challenging. Santok was estab- with mobile sand-banks and transient riverbanks. The lished during the mild climate of the Medieval Warm Dr. Andrzej second stage was a meandering river, formed during Period. Seasonal floods occurred regularly and lasted Piotrowski (PhD) the Littorina Transgression, and the third was an anas- up to 2‒3 months. The amount of snow and rainfall is a retired employee tomosing river, flowing through three or four river- received by the rivers was similar to present time. The of the Polish Geological Institute – National beds with a very low water descent rate. These types banks of the riverbeds were quite stable, strengthened Research Institute, of riverbeds as well as the floodplain were stabilized naturally by vegetation and by man-made embank- a long-time Chairman by vegetation (trees, bushes, turf). This stability cre- ments of wood and soil with stone-clay lining. Ar- of the Szczecin Branch ated conditions favorable for the establishment of the chaeological excavations revealed layers attesting to of the Polish Geological oldest fortified settlements, on islands between the the great strength of flood waters, which had eroded Society, and the author of numerous geological riverbeds. We now know that Santok was founded the foundations of the fortifications and thereby de- maps of north-west against the backdrop of a multi-channel river, in the stroyed them. Poland. catchment area of ​​the Noteć and Warta riverbeds. This andrzej.k.piotrowski@ is not unusual because many early-medieval fortified Settlement gmail.com villages, such as Opole and Wrocław, were founded on islands of this type. With all this in mind, the question arises as to what The Noteć and Warta surrounded Santok until the motivated the establishment of the Santok settlement, eighteenth century, when a great flood resituated the and subsequently stronghold, in such a difficult flood-

Explanations:

11 flat and wavy morainic plateau,

12 hilly morainic plateau,

13 glacitectonic disturbed hills, Paweł Sydor (MA) is a geologist working in the fields 14 eskers, of geological cartography, 15 drumlins, geohazards, marine geology, and sea-level changes. 16 ice-marginal lake plains, [email protected]

17 out-wash plains,

18 glacier valleys and river valleys, 19 river terraces,

10 slope of the plateau,

11 phase moraines,

12 sub-phase moraines,

13 waters,

14 ice-sheet thickness (m). Palaeogeography of the West region and Lubusz land during the Velgaster-Wolin Subphase 14,300 years ago.

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plain environment, despite the potentially more con- er Piast forts in the country’s key towns. The Warta, venient location on the edge of the nearby plateau. which was the communication axis of the country at Most likely this was due to cultural and natural factors. the time, provided access to regions more central, and Human settlement of Santok began in the second Santok played a strategic role as a watchtower on its half of the eighth century, as evidenced by the archae- northern border. ological material and absolute dating techniques. The sandy “island” that emerged above the water level was Resources used as a settlement site, which initially had an open plan and may have only been inhabited periodically. Although, as previously mentioned, hydrological The fortified site was accessed by numerous channels conditions in this location can be described as unfa- of the Warta and Noteć rivers, which created direct vorable, the available geological resources helped in waterway connections both to the nearest hinterland building the settlement. The construction of the village and to remote territories. This had undeniable signif- on Santok’s even terrace surface in the tenth centu- icance for transporting goods and trade, making this ry was a great engineering undertaking. Santok was an excellent location for conducting business, along built on the fluvial fine sand that is typically found in a river route connecting the Baltic coast to the interior. slow-flowing rivers. This sand is of little use as build- Evidence of these far-reaching contacts can be seen ing material, but are somewhat useful for stronghold in objects found in the oldest layers of the settlement, reinforcements, despite the shallow groundwater level which include antler combs of foreign origin, woolen and seasonal floods. The sand used for building the fabrics, glass beads and amber, as well as Feldberg clay embankments of wood and soil that surrounded the pots. Soon, Santok expanded dramatically, attaining settlement was probably taken from the neighboring a key role in the region, and in the tenth century it plateau, but also from the nearby floodplain terrace. became part of the early Polish (Piast) state. Archae- Natural resources, such as gravel, boulders, clay, lay- ological findings clearly show that the defensive for- ered till (for making ceramics), bog iron (for iron tifications were rebuilt at that time to resemble oth- production), peat (fuel) and wood were all obtained

The Santok stronghold as part of the Gniezno state at the end of the tenth century. Based on Kurnatowska (2008: 326).

Key: 1 main strongholds of the early Polish state, important stronghold sites, and also trade emporia in other territories, 2 smaller fortresses of various ranks, 3 cemeteries with burials of armed warriors, 4 core territory of the early Polish state, 5 the farthest territorial range of the early Polish state.

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from the plateau located “behind the river.” It must from the layers of the settlement in Santok has helped Reconstruction of the have posed a major technical challenge for the peo- determine the times when Santok experienced flood- geology of the confluence ple at that time to transport boulders weighing up to ing. Correlating these data with archaeological sources of the Warta and Noteć rivers 2.5 tons, used to strengthen embankments and build makes it possible to explain how the communities of in the early Middle Ages. stone buildings. that time tried to defend themselves against the effects The area of the former fortified settlement is cur- of floods and high river water levels. rently around 5.5 ha, while the volume of all cultural Over the past two millennia, human activity and sediments can be estimated at around 200,000 m3 in settlement in various climatic conditions have strongly total, with a weight of approx. 300,000 tons, of which influenced the landscape in Santok, but environmental about 60,000 are imported building materials from responses are well preserved, especially in paleoeco- nearby plateaus. This illustrates the sheer scale of the logical findings. This project is still ongoing and in the undertaking, which included the construction of for- end we hope to get a thorough analysis of the natural tifications and all buildings within the settlement. conditions in which the inhabitants of the Greater The ancient fortified settlement currently stands Poland / Pomerania borderland lived, as well as the 8 m above the surrounding terrace and is itself “sub- cultural and environmental transformations that took merged” in flood sediments dating from the last 1200 place in this area in the early Middle Ages. years. The flood cycle is repeated every year. A helpful The research was funded by the National Science indicator of environmental changes, useful in study- Centre, Poland (project Sonata Bis No.2015/18/E/ ing the history of water reservoirs, can be found in HS3/00425). diatoms, microscopic algae whose silica valves pre- serve well in sediments, including cultural ones. Di- Kinga Zamelska-Monczak, Further reading: atom groups are very useful because the distribution Andrzej Piotrowski, of their species is closely related to water quality pa- Paweł Sydor Kurnatowska Z. (2008). rameters, including salinity and nutrient status. They Początki i rozwój państwa. W: M. Kobusiewicz (red.), also show preferences for specific habitats and eco- Pradzieje Wielkopolski. Od epoki logical requirements, therefore they can be used to The research was funded by the National Science Centre, kamienia do średniowiecza. reconstruct environmental changes. Diatom analysis Poland (project Sonata Bis No.2015/18/E/HS3/00425). Poznań, 297–395.

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