Combined pollen and macrofossil data as a source for reconstructing mosaic patterns of the early medieval urban habitats – a case study from Gdańsk,N. Poland

Plant macrofossils, pollen, fungal spores and other non-pollen palynomorphs (NPPs), were analyzed in three archaeological exposures established in a small area in the oldest part of the historic city of Gdańsk. One of the aims was to investigate how precisely the combined pollen and macrofossil data may reflect the diversity of local habitats within an urban archaeological site and to compare the range of information obtained using each of the methods separately. The other aim of the study was to reconstruct the environmental conditions in the earliest occupied area of the historic centre of Gdańsk. The repeatable composition and, in many points, consistency among pollen and macrofossil data in all three profiles strongly suggest that the apparently biased structure of these fossil remains in fact reflects a mosaic pattern of the vegetation in the area of the site. The combined pollen and macrofossil data enabled separation of local elements from those transported to the site by different means. The results show that already at the beginning of the 12th c., the area was almost totally deforested, but up to the mid-13th c. the settlement organization was still relatively loose, resembling a rather rural structure with well-developed ruderal plant communities and patches of semi-natural vegetation. At the coring area, strongly eutrophic riparian vegetation was bordering patches of dry grassland on a sandy holm. The large proportion of pollen of various entomophilous plants mostly from meadows and pastures is explained as a result of the presence of dung, as confirmed by the abundances of coprophilous fungal spores. The study indicates that parallel pollen and macrofossil analysis is essential for correct interpretation of fossil assemblages. Application of both methods enables broadening of the range of remains representing various organisms and obtaining more precise tools for environmental reconstruction and better understanding of the taphonomic processes at the archaeological site.     

Peculiarities of sedimentation conditions in the oxbow lakes of Dubysa River (Lithuania)

Abundant wood remains and buried trees have been found in the western part of Lithuania near Zakeli?kiai and Lyduv?nai on Dubysa River (a tributary of Nemunas River) where deposits are rich in organic remnants and buried soils. In Zakeli?kiai and Skiru?iai sections of Dubysa River oxbow sediments were investigated by various methods (dendrochronological, carbonate, granulometric, pollen and mollusc fauna analysis). In addition, these sections were dated using the radiocarbon method. Samples were collected from deposits of Dubysa River outcrops. The studied oxbow lakes have existed for more than 5 thousand years (from ca. 4300 BC to 1000 AD). During this period organic rich deposits with trees and branches were formed in the oxbow lake. This indicates that at the end of Atlantic, during Subboreal and in the early Subatlantic periods there was a forest growing that contained mainly oaks which were falling down into an oxbow lake and later were covered by sandy and silty deposits. The granulometry of alluvial deposits, as well as the mixture of medium-grained sand and silt show different stages of Dubysa River palaeochannel formation: riverbed and oxbow lakes. Three climate warming cycles were revealed according to carbonate analysis data in all investigated sections. The rheophile thermophilous Holocene age molluscs species Bithynia tentaculata L., Unio cf. crassus Philipsson, Pisidium amnicum (Müller), Theodoxus fluviatilis (Linnaeus) have been found. The pollen composition and sequences have been divided into five local pollen assemblage zones (LPAZ) and described according to pollen spectra in each zone. In this way it is possible restore palaeoclimatic coherent evolution, trends and cyclical change.