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Jerzy Sikora

The University of Lodz, Institute of Archaeology, Faculty Member

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Medieval archaeologist particularly interested in mortuary archaeology and the changes of the funeral rituals in Middle Ages, hilforts, landscape and settlement studies, GIS, archaeological prospection and non-invasive methods.
I did my PhD thesis in 2005 (entitled: “Central Poland in the early Middle Ages. Archeology and settlement" under the supervision of Professor L. Kajzer).
In 2005-2007 I was contractor on several rescue archaeological field works i.e. large – scale excavations in Bełchatów-Szczerców Coal Mine, A2 motorway or urban excavation in Drohiczyn and Cracow).
Since 2007 Assistant professor in Institute of Archeology (University of Lodz).
Since 2008 I've been doing research in Ostrowite, small village in Eastern Pomerania. In 2013-2017 directed non-invasive research program on several hillforts in Central Poland. Between 2015-2017 on stronghold/motte-and-bailey site in Rozprza.
Address: Instytut Archeologii Uniwersytetu Łódzkiego
ul. Uniwersytecka 3
90-137 Łódź

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Books by Jerzy Sikora

monumenta archaeologica barbarica tomus xxiii COLLEGIUM EDITORUM

Wikingowie w Polsce? Zabytki skandynawskie z ziem polskich, eds. M. Bogacki, A. Janowski, Ł. Kaczmarek, Gniezno-Szczecin 2019

by Andrzej Janowski, Łukasz Kaczmarek, Jakub Morawiec, and Jerzy Sikora

Grodziska wczesnośredniowieczne Polski centralnej. Archeologiczne badania nieinwazyjne z lat 2013-2016 (Early medieval strongholds in Central Poland. Non-invasive research in 2013-2016))

by Piotr Kittel, Jerzy Sikora, Piotr Wroniecki, and Marta Nalej

Monograph on non-invasive research of 12 early medieval strongholds surveyed in 2013-2016: Chełmo... more Monograph on non-invasive research of 12 early medieval strongholds surveyed in 2013-2016: Chełmo, Ewinów, Krzepocinek, Mnichów, Okopy, Rękoraj, Rozprza, Spycimierz, Stare Skoszewy, Szydłów, Witów, Żarnów. With English summary and description of figures. Chapters with basic informations about excavations carried out in Żarnów (2012-2013) and Rozprza (2015-2016) added.

Early medieval production settlement at Przeczyce (Poland) - in Polish

Territory of the Central Poland in early Middle Ages (in Polish, with English Summary)

Papers by Jerzy Sikora

The spatial and temporal reconstruction of a medieval moat ecosystem

Scientific Reports, Nov 30, 2022

Moats and other historical water features had great importance for past societies. The functionin... more Moats and other historical water features had great importance for past societies. The functioning of these ecosystems can now only be retrieved through palaeoecological studies. Here we aimed to reconstruct the history of a stronghold's moat during its period of operation. Our spatio-temporal approach allowed mapping of the habitat changes within a medieval moat for the first time. Using data from four cores of organic deposits taken within the moat system, we describe ecological states of the moat based on subfossil Chironomidae and Ceratopogonidae assemblages. We found that over half (57%) of the identified dipteran taxa were indicative of one of the following ecological states: limnetic conditions with or without periodic water inflow, or marshy conditions. Samples representing conditions unfavourable for aquatic insects were grouped in a separate cluster. Analyses revealed that the spatio-temporal distribution of midge assemblages depended mostly on depth differences and freshwater supply from an artificial channel. Paludification and terrestrialization did not happen simultaneously across the moat system, being greatly influenced by human activity. The results presented here demonstrate the importance of a multi-aspect approach in environmental archaeology, focusing not only on the human environment, but also on the complex ecology of the past ecosystems. The diversity of habitats and of the mutual connections between organisms and their environment can now be studied in a wide variety of ecosystems, including historical features no longer present. Moats were artificial bodies of water providing defence for inhabited strongholds in medieval times. Ecological studies of moats can therefore provide a window into historical influences of human activity on natural ecosystems, broadening our knowledge of the functioning of such features, of past human societies, and of our coexistence with (seemingly distant) animal communities. Ecological studies can be carried out on moats that have either been preserved from historical times (e.g. 1,2 ) or have been recently reconstructed. However, these modern moats do not perform the same function today as in the Middle Ages or Early Modern Period 3 , and their aquatic ecosystems may therefore differ. The medieval stronghold's inhabitants influenced water conditions by changing its trophic state, creating new habitats by placing construction elements, modifying its hydromorphology and sedimentation of defined types of water deposits, and their enrichment with selected metals (see ). What were the nature, scale, and consequences of such activities? The only way to get a clear window into those past ecosystems is through palaeoecological studies. Geochemical studies of historical layers (such as core samples) conducted so far have in many cases confirmed their indicator role in environmental archeology 6 . The clearly higher Pb and Cu concentrations in the sediments of medieval moats have been used to determine the course of historical watercourses. However, the grain and mineral composition of sediments influences their susceptibility to metal sorption 7 . Therefore, geochemical

Radioactive Isotope Ratios as a Novel Method of Ancient Pottery Analysis: Ostrowite Archaeological Site Data

SSRN Electronic Journal, 2021

The radioactive isotope content of any geological sample (lithic rock, sand, silt or clay) is cha... more The radioactive isotope content of any geological sample (lithic rock, sand, silt or clay) is characteristic for a specific type of geological material. The use of the isotope ratio method allows each sample to be distinguished in terms of source. In this study the radioactive isotope ratio method has been applied to a set of ceramic pottery specimens from the same multi-layered archaeological site and probably produced from local raw material. The method shows the similarities within the ceramic material used to manufacture the pottery. The variations in the quantitative and qualitative compositions of the basic products (clay, silt, loam, sand, ash and organic admixtures) used in the preparation of the ceramic paste change the isotopic composition and activity ratios. Pottery from each ceramic manufacturing centre, based on the specific composition of the raw materials, have characteristic isotope ratios. Radioactive isotope ratios as fingerprints of ancient ceramic manufacturing centres have not yet been applied as an archaeometric method. The proposed method has been applied to a Striatemulti-phased settlement complex and pottery manufacturing centre in Ostrowite in northern Poland. The earliest pottery to be manufactured in Ostrowite dates to5200-5000 BC, during the existence of the Early Neolithic settlement. Subsequent settlement phases and pottery production horizons are dated to the early Iron Age (approx.800-600 BC), the Roman period (1st to 4th centuries AD) and the Middle Ages (11th to14th centuriesAD). The site has a long tradition and experience in ceramic production.In this study two isotope ratios were applied: 40K/ 228Ac and 226Ra/ 208Tl. The proposed non-destructive archaeometric method allows the analysis of vessel fragments. This study analysed 11 fragments of Neolithic pottery,3 fragments from the early Iron Age, 5fragments from the Roman period, 5 specimens from the medieval period, 3 burned clay samples and 8 raw material samples, all collected from the Ostrowite complex.This pilot study confirm the grouping of the isotope ratio results for each type of the samples, even in terms of similarities with the base clay material collected in this region.

From a point on the map to a shape in the landscape. Non-invasive verification of medieval ring-forts in Central Poland: Rozprza case study

Archaeologia Polona, 2015

In the last decades several research projects were undertaken in Poland to verify remnants of med... more In the last decades several research projects were undertaken in Poland to verify remnants of medieval ring-forts, and also smaller fortified objects, mostly motte-type structures, which were private residences of the late medieval nobility. The main focus of those projects were issues related to the chronology of strongholds via the study of material culture through excavation. Since the 1990s an attempt to broaden this knowledge with absolute dating acquired by dendrochronological analysis supplemented by the 14C method provided detailed dates of many rampart features. As a result, ring-forts or mottes were understood as dots on maps, detached from their landscape contexts, attempting to illustrate mutual synchronic processes of establishment, operation and destruction in specific chronological horizons. They were used to support a number of historical theories, such as the development of pre-state (so called "tribal") territorial organization, development of the early Piast monarchy, transformation of the administrative network of the monarchy (e.g., Kara 2009), as well as the development of a network of private residences of the nobility from the mid-13 th century on. In 2013 and 2014, a research project based on non-invasive verification of ring-forts in the area of Central Poland was conducted. The main difference between this project and former actions was an attempt to implement large-scale, solely non-invasive and geomorphological surveys, in order to explain broader environmental and spatial intra-site and landscape contexts of the studied ring-forts. A wide variety of methods was implemented, including geophysical (magnetic gradiometry and earth resistance), geochemical (phosphate), aerial archaeology, aerial laser scanning, analytical fieldwalking, topographic survey and geomorphological mapping.

Closing a gap with simple toy. How using a tablet affected documentation workflow on the Rozprza ring-fort excavation

The use of digital documentation, including image-based 3D techniques allows to reduce the role o... more The use of digital documentation, including image-based 3D techniques allows to reduce the role of traditional and time-consuming manual drawings. However it significantly shortens the process of obtaining data in the field, it also need long time for digital processing of images. In fact, this situation is nothing new. Older researchers probably still remember that similar challenges were connected with a traditional archaeological photography of pre-digital era. During the excavation on the medieval ring-fort and motte in Rozprza 2D and 3D photogrammetric documentation and integration of the results in GIS was widely used, eliminating traditional forms of field documentation. It was particularly important in extreme wet conditions of work in the bottom of Luciąza river valley. Popular Agisoft PhotoScan software and QGIS georepherence module as well as a set of open source graphical raster and vector applications were used. The key role was the appropriate organization of the field...

Obraz pełen luk. Grodzisko w Rozprzy po ponad półwieczu badań archeologicznych (An image full of gaps. The relics of fortification in Rozprza after more than half a century of archaeological research)

Archeologia i historia ziemi rozpierskiej, 2025

The remains of a medieval fortified site in Rozprza, initially identified as a motte-type wooden ... more The remains of a medieval fortified site in Rozprza, initially identified as a motte-type wooden castle, attracted archaeologists for about a century. However, it was not until 1963–1966 that it was excavated for the first time by a team of researchers from the Archaeological and Ethnographical Museum in Łódź led by Aldona Chmielowska. After half a century, in 2013–2016, new research was conducted by Piotr Kittel and Jerzy Sikora from the University of Lodz. With the help of new excavation, recording, and analysis techniques, they were able to verify older findings on the chronology and stratigraphy of the site and to place the site in the environmental context using multi-proxy palaeoenvironmental research methods. According to this research, the construction of the fortress was preceded by the existence of an open settlement, which, among other features, left the layer of fertile anthroposoil – the socalled “dark earth” - dated to the 10th and the beginning of the 11th century. The earliest fortification – the ring-fort – was probably built here shortly before 1050 and possibly ceased to exist in the 12th century and was reoccupied in the second half of the 13th century. Dendrochronological analysis clearly shows that in the 1330s a new structure was erected on the site of the former stronghold. It was a typical motteand-bailey timber castle of the time, used as a family seat by the noble family of Nagodzice-Jelitczycy. It was rebuilt in the 15th century, when another moat was also added, and existed at least until the end of that century. Later, in the 16th century, both palaeoecological research and written sources indicate that the area of the former fortress was used as a meadow.

THE INHILLDAUGAR PROJECT: RESEARCH QUESTIONS AND APPROACHES TO INVESTIGATING FORTIFICATIONS ON COMMUNICATION ROUTES

LIETUVOS ARCHEOLOGIJA, 2023

The Daugava River has been one of the most important traffic arteries in the Eastern Baltic regio... more The Daugava River has been one of the most important traffic arteries in the Eastern Baltic region. The establishment of more than 30 hillforts alongside this river reflects the importance of this waterway. Most of these hillforts are understudied. Thus, the bigger picture regarding the hillforts’ inhabitation patterns, chronology, environment, and function(s) remain unknown. As such, the INHILLDAUGAR project seeks to systematically analyze the river’s landscape on a macro scale by combining palaeoenvironmental,
archaeological, and linguistic studies. This article presents the genesis of the INHILLDAUGAR project and
preliminary results from the 2022 and 2023 field campaigns.
Overall, nine hillforts were studied by using non-invasive and minimally invasive field techniques
(including geomagnetic surveys, drillings, and test pits). Additionally, geological and geomorphological
investigations were undertaken in the vicinity of these sites. Samples obtained from the archaeological
and geological investigations provided data for further palaeoenvironmental studies and shed light on the
chronology of the sites.

INHILLDAUGAR: minimally invasive fieldwork and linguistic analysis on hillforts along the Daugava river

Antiquity, 2024

Combining non-and minimally invasive archaeological survey, geomorphological methods and linguist... more Combining non-and minimally invasive archaeological survey, geomorphological methods and linguistic studies enables a better understanding of the dynamic use of the Daugava waterway from the Bronze to the Viking ages. Results indicate a common origin period of many fortified settlements and also identify research questions about cultural fluctuations in the Baltic-Slavic-Scandinavian contact area.

To not see the forest for the trees. A non-invasive approach to the Góra Chełmo medieval hillfort

DOAJ (DOAJ: Directory of Open Access Journals), 2015

The hillfort in Góra Chełmo was described for the first time in archaeological literature by J. K... more The hillfort in Góra Chełmo was described for the first time in archaeological literature by J. Kamińska. It was excavated in 1955-56, during the construction of an observation tower for the forestry authorities. Only two trenches were completed and a basic chronology of the site established to the 10th-13th centuries AD (Kamińska 1958). Kamińska reported only three lines of ramparts, covering the top part of Góra Chełmo, which at 232 m a.s.l. is the highest hill in the relatively flat area of the Łódź region. In the early 2000s, during a fieldwalking survey, J. Sikora (2008) discovered two more embankment lines of the hillfort. The 15th century chronicler Jan Długosz described Góra Chełmo among the most important mountains in the Kingdom of Poland and attached great symbolical meaning to it. According to this description, the church on the hilltop had been founded by Piotr of Skrzynno, one of the most prominent Polish noblemen from the first half of the 12th century. The church building was said to be surrounded by seven lines of moats. A non-invasive survey in 2013-14 was aimed at identifying the spatial structure of the fortifications, interior features (among others, buildings and possible remains of the church) and elements of the communication infrastructure. It also aimed at determining the purpose of the fort (in archaeological literature it was supposed to be connected with pre-Christian ritual activity). One of the objectives was also to ascertain the state of preservation of the stronghold and identify potential threats. The project started with a study of aerial images and analysis of aerial laser scanning-derived maps (using LAS point clouds prepared for a national ISOK program). Aerial prospection revealed only crop marks connected with the denudation valley located south of the mount, which was likely used as a road connecting to open settlements recorded around the hillfort, mostly on its southern side. It could not bring any new data about the hillfort itself, as the area is completely forested. In this situation, LiDAR-derived DTM maps proved very helpful (Fig. 1). They allowed two previously unknown lines of moats and ramparts to be detected, giving a total of seven ramparts, which is which is the number that Jan Długosz described. The area enclosed by this rampart system covers 11.7 ha, making the Góra Chełmo defensive structure the largest known early medieval stronghold in central Poland. For the sake of comparison, the ring-fort in Łęczyca, which was a local power center and a princely seat in the 13th century, is thought to encompass an area of about 1 ha. The

Multi-disciplinary research on the Neolithic pile-dwelling Serteya II site (Western Russia) and the landscape reconstruction

HAL (Le Centre pour la Communication Scientifique Directe), 2017

New sources about the past? Application of geophysical prospection methods in the study of the Middle Ages. Nowe źródła o przeszłości? Zastosowanie prospekcji geofizycznej w badaniach nad średniowieczem

by Jerzy Sikora and Piotr Wroniecki

Archeologia średniowiecza ziem polskich na początku XXI wieku Grodziska, cmentarzyska i monety w perspektywie nowych metod badawczych, 2021

Overview of archaeological geophysical methods applied to the study of medieval towns, fortificat... more

Modern research methods in medieval archaeology on the example of the Rozprza hillfort. Współczesne metody badawcze w archeologii średniowiecza na przykładzie grodziska w Rozprzy

by Jerzy Sikora, Piotr Wroniecki, and Piotr Kittel

Archeologia średniowiecza ziem polskich na początku XXI wieku, 2021

Brief summary of the modern methods used in the research of the hillfort at Rozprza (Central Pola... more

Graves of ancestors, giants and pagans. Attitude of the early medieval Poles and Pomeranians to ancient burial monuments.Groby przodków, olbrzymów, pogan. Wczesnośredniowieczni mieszkańcy Polski i Pomorza a dawne monumenty grobowe

Archeologia średniowiecza ziem polskich na początku XXI wieku Grodziska, cmentarzyska i monety w perspektywie nowych metod badawczych, 2021

Different scenarios of the interaction of the inhabitants of early medieval Poland and Pomerania ... more

Novel method of ancient pottery analysis based on radioactive isotope ratios: a pilot study

Heritage Science

The proposed method has been applied to a multi-phased settlement complex and pottery manufacturi... more The proposed method has been applied to a multi-phased settlement complex and pottery manufacturing centre in Ostrowite in northern Poland. In this study the radioactive isotope ratios method has been applied to a set of ceramic pottery specimens from the same multi-layered archaeological site and probably produced from local raw material. The pilot radiometric research was based on: 24 Neolithic (5200–5000 BCE), 21 Early Iron Age (800–600 BCE), 4 Roman Period (100–400 CE), and 13 Middle Ages (1030–1320 CE) pottery fragments, and also 8 samples of local clay (glacial till) and 3 burned clay samples. The method shows the similarities within the ceramic material used to manufacture the pottery. The variations in the quantitative and qualitative compositions of the basic products (clay, silt, loam, sand, ash and organic admixtures) used in the preparation of the ceramic paste change the isotopic composition and activity ratios. Pottery from each ceramic manufacturing centre, based on t...

Novel method of ancient pottery analysis based on radioactive isotope ratios: a pilot study

Heritage Science, 2022

The proposed method has been applied to a multi-phased settlement complex and pottery manufacturi... more The proposed method has been applied to a multi-phased settlement complex and pottery manufacturing centre in Ostrowite in northern Poland. In this study the radioactive isotope ratios method has been applied to a set of ceramic pottery specimens from the same multi-layered archaeological site and probably produced from local raw material. The pilot radiometric research was based on: 24 Neolithic (5200-5000 BCE), 21 Early Iron Age (800-600 BCE), 4 Roman Period (100-400 CE), and 13 Middle Ages (1030-1320 CE) pottery fragments, and also 8 samples of local clay (glacial till) and 3 burned clay samples. The method shows the similarities within the ceramic material used to manufacture the pottery. The variations in the quantitative and qualitative compositions of the basic products (clay, silt, loam, sand, ash and organic admixtures) used in the preparation of the ceramic paste change the isotopic composition and activity ratios. Pottery from each ceramic manufacturing centre, based on the specific composition of the raw materials, have characteristic isotope ratios. Radioactive isotope ratios as fingerprints of ancient ceramic manufacturing centres have not yet been applied as an archaeometric method. In this study two isotope ratios have been selected and applied: 40 K/ 228 Ac and 226 Ra/ 208 Tl. All analysis have been done using gamma spectrometry system, with quality and quantity analysis of the spectrums. Low-background passive shield was used for obtain improvement of results quality. The pilot study confirms the grouping of isotope ratio results for each sample type, even in terms of similarities with the base clay material collected in this region.

Bronze bracelets deposit from Niewierszyn by the Pilica River

Sprawozdania Archeologiczne, 2020

In the autumn of 2017 in Niewierszyn in the Aleksandrów commune, a deposit of two bronze bracelet... more In the autumn of 2017 in Niewierszyn in the Aleksandrów commune, a deposit of two bronze bracelets was discovered. The discovery site was on the edge of the Pilica floodplain terrace.The bracelets were almost identical in size and ornamentation. Also, the chemical composition of the bronze from which they were made was very similar. It may be hypothesised that the ornaments were made by the same manufacturer, probably at a similar time. Based on the analysis of the form and ornamentation, the bracelets in question can be dated to HA1. This dating corresponds to the settling of the areas in the Pilica river basin by communities associated with the Konstantynów Łódzki group, characterized by features of the early Urnfield culture. Virtual modelling of casting and an experimental cast were used to elucidate the manufacturing technique. Apart from a chronological and cultural analysis, the text attempts to show the hoard against a wider (micro-regional) settlement background, including ...