image/svg+xml21XI/1/2020INTERDISCIPLINARIA ARCHAEOLOGICANATURAL SCIENCES IN ARCHAEOLOGYhomepage: http://www.iansa.euThe Benefts of Using Radiocarbon Dating and an Interdisciplinary Approach for Identifying Contamination of Archaeological Find Assemblages. A Case Study from the Multi-period Settlement Site at Rakovice, Czech RepublicTereza Šálkováa,b,c*, Tomáš Hiltschera, Dagmar Dreslerovád, Lenka Kovačikovác, Jaroslav Jiříka,eaPrácheň Museum in Písek, Velké náměstí 114, Písek, Czech RepublicbFaculty of Arts, Institute of Archaeology, University of South Bohemia in České Budějovice, Branišovská 31a, 370 05 České Budějovice, Czech RepubliccFaculty of Science, Laboratory of Archaeobotany and Palaeoecology, University of South Bohemia in České Budějovice, Branišovská 1760, 370 05 České Budějovice, Czech RepublicdInstitute of Archaeology of the Czech Academy of Sciences, Prague, Letenská 4, 11801 Praha 1, Czech RepubliceFaculty of Arts, Institute for Archaeology, Charles University in Prague, Náměstí Jana Palacha 2, 116 38 Prague 1, Czech Republic1. IntroductionEarlier residuality and later intrusion in archaeological assemblages are key problems in settlement sites with a long history of human occupation. The spectra of artefact and ecofact assemblages in the features are often contaminated – at least partially – as a result of depositional or post-depositional processes (Borojevic, 2011; Kuna and Němcová, et al.2012; Pelling et al., 2015; Peeling et al., 2015; Šálková et al., 2016). Our multi-disciplinary analysis of the assemblage of plant remains from the superposition of two features from the Early Roman and Early Mediaeval periods from the site at Rakovice, Czech Republic (Figure 1), demonstrates the importance of such analysis for recognizing contamination of the features’ flls. An archaeological feature, severely damaged by ploughing, was found during a surface survey in April 2015. The subsequent excavation revealed what appeared to be a simple stratigraphic scenario. A shallow, sunken, elongated feature 1 (hereafter referred to as F 1) was partially disrupted in its north-western part by another shallow oblong feature 1.1 (hereafter referred to as F 1.1). Based on pottery fnds, F 1 was dated to the beginning of the Early Roman period (several sherds also date to the La Tène period). The stratigraphically later F 1.1 was dated to the Early Mediaeval period. However, during processing of the archaeobotanical fnds, the formation of the fll of these two features began to raise questions. Especially dubious was a large quantity of charred fax seeds (Linum usitatissimum) recovered in similar quantities from both features. AMS radiocarbon data on the fax and other plant macroremains subsequently confrmed that the formation of the features’ flls was more complex than it had appeared on the basis of the feld observations and the typological analysis of the pottery fragments.Volume XI ● Issue 1/2020 ● Pages 21–31*Corresponding author. E-mail: terezasalkova@seznam.czARTICLE INFOArticle history:Received: 2ndApril 2020Accepted: 17thJune 2020DOI: words:contaminationtaphonomyplant macroremainsLinum usitatissimumradiocarbon datingarchaeologyABSTRACTThe contamination of archaeological fnd assemblages at multi-period (and other) sites can sometimes go undetected. In this article we seek to highlight this problem through analysis of the fll of settlement features from a site at Rakovice, South Bohemia, Czech Republic. After a detailed spatial evaluation of diferent categories of fnds, an analysis of plant macroremains, and radiocarbon dating, what had originally appeared to be a clear-cut archaeological situation of the superposition of two features from the Roman and Early Mediaeval periods was shown to be much more complex. This discovery confrmed the value of a multi-disciplinary approach and especially of radiocarbon dating even in apparently simple contexts. What we are especially concerned about is the risk of assigning particular periods to multi-period sites that have been insufciently radiocarbon dated.
image/svg+xmlIANSA 2020 ● XI/1 ● 21–31Tereza Šálková, Tomáš Hiltscher, Dagmar Dreslerová, Lenka Kovačiková, Jaroslav Jiřík: The Benefts of Using Radiocarbon Dating and an Interdisciplinary Approach for Identifying Contamination of Archaeological Find Assemblages. A Case Study from the Multi-period Settlement Site at Rakovice, Czech Republic22In this article we aim to demonstrate that: (a) the earlier residuality and later intrusion of plant remains can be crucial for archaeological interpretation even in a situation that appears stratigraphically clear and in which each archaeological feature comprises only artefacts (mostly ceramics) dated to specifc periods; (b) the true formation history and “contamination” cannot be recognized without radiocarbon dating of several specimens and without detailed knowledge of the local archaeology and the spectrum of plants cultivated in a particular period. Our objective is to highlight the dangers of unrecognized contamination and the subsequent misinterpretation of archaeological contexts, and to suggest that such contamination can only be revealed by a multi-disciplinary approach and by including radiocarbon dating.2. Materials and methods2.1 Background informationThe site under investigation is situated in the north-western part of the Písek region (South Bohemia, Figure 1), which was settled in the Upper Palaeolithic and Mesolithic, the Iron Age, the Early Roman period, and from the early Middle Ages until the present (Břicháček and Fröhlich, 1993; Dubský, 1925; Debnar, 2000; Dreslerová, 2004; Fröhlich et al., 2008; Hiltscher et al., 2018).The soil horizon consists mainly of gleyic modal stagnosols generated on the polygenetic loam substrate and glacial sediments (Němeček and Lérová, 2009). The site is at 465 m asl. in the warmest part of South Bohemia, which is also, except for the region of the upper Vltava and Elbe lowlands, the warmest part of the whole of Bohemia (Quitt, 1971). Luzulo albidae-Quercetum petraeaeand/or Abieti-Quercetumwere reconstructed as the potential natural vegetation (Neuhäuslová et al., 1997).2.2 Archaeological excavationAn excavation trench covering an area of 20 m2was dug in the area with the highest accumulation of ploughed-out pottery and divided into a network of 1 m squares (Figure 2). The flls of the sunken features were excavated in 10-cm-thick mechanical layers. F 1 (with a volume of approx. 17,000 l) was a fat, irregular, elongated pit, oriented north-south. The bottom was slightly concave. There was a concentration of stones at the southern end, under which a larger quantity of pottery fragments were excavated. The fll was dark brown: a black loamy deposit with a high content of a charcoal admixture. It contained fragments of pottery, animal bones, and a spindle whorl. F 1.1 (with a volume of approx. 6,700 l) was a shallow, oblong pit, oriented northeast-southwest, with a fat bottom and cutting into F 1. The fll was dark brown: again, a black loamy deposit with a high content of a charcoal admixture. F 1.1 contained fragments of pottery, animal bones, and a glass bead.A sample of sediment with a volume of 10–25 litres from each square and layer was processed by fotation in a fotation tank (modifed ANAKARA type) using a 0.25 mm square mesh sieve for the foating of the organic component and a 0.5 mm sieve for the mineral component (Pearsall, 1989). Some 38 samples with a total volume of 516 litres were processed (325 litres from F 1; 105 litres from F 1.1; 86 litres from the boundary area between the two features). Archaeobotanical and archaeozoological material and fne artefacts from the fotation and heavy residue fractions were sorted and analysed further (for details, see Excavation report no. C-201901695; AMČR).2.3 Analysis of plant macroremainsThe samples were studied under a stereomicroscope. All botanical material was sorted, but only the charred plant macroremains were taxonomically determined and counted