Molecular Biomarkers in the Biosphere, Geosphere and Archaeosphere

Weber, Jan Hendrik ORCID

Biomarkers are molecular compounds from a once living organism (plant, microbe or animal), which can be used to trace a specific source organism, a group of organisms, or a particular process in geological and archaeological media. In this thesis, organic geochemical techniques including the biomarker approach and stable isotopes were applied to different research areas of the biosphere, geosphere and archaeosphere to characterise the origin of the organic matter. The biomarkers provide essential knowledge about environmental and climatic changes, and about the diet and rites of ancient cultures. Paleoclimate and associated paleovegetation exert a major influence on present to prehistoric human activities and therefore are of paramount importance to investigate ancient human living conditions. Early reforestation after the last glacial shaped human living space and was dominated by pioneer plants including four birch species. These differ in habitat conditions but their differentiation by palynology poses a problem due to similar pollen shape and size. Here an alternative approach of birch species identification based on their epicuticular wax composition was ascertained for potential application in especially Late Glacial and Holocene sediments. A chemotaxonomic separation of the four Europen birch species based on a suite of wax lipids could be achieved. In addition to previous studies employing recent plant wax n-alkane distribution only, the potential contribution of n-alkanes, which in an ontogentic to diagentic continuum can be released from precursor lipids via secondary and tertiary degradation of n-alkyl esters (and their degradation products like n-alkanoic acids and n-alcohols) were assessed. The early release of bound wax lipids carries a high potential to modulate the pool of free lipids, which should be considered when interpreting wax lipids of potentially mixed origin and their isotopic signatures in soils and sediments. Lake sediment from Lake Steisslingen (SW-Germany) has been investigated to characterise the biotic response of organisms during the Younger Dryas cold period (12,680 – 11,590 BP) at the Pleistocene/Holocene transition. Based on biomarker distributions representing specific organism groups including diatoms, haptophyte algae, heterocyte cyanobacteria, heterotrophic bacteria and terrestrial plants, a separation of the Younger Dryas in three phases was defined. In a second case study, lacustrine sediments from Lake Stymphalia (Peleponnes, Southern Greece) were investigated to study the local environmental and climatic changes between 15,000 to 2,000 a BP. Heterocyte glycolipids (HGs) and glycerol dialkyl glycerol tetraethers (GDGTs) have been applied to characterise the (aquatic) microbial community and to determine paleotemperature changes in the study area. Epicuticular wax lipids yielded information on development of paleovegetation and revealed a human impact on land-use and ecosystem evolution. The second part of this PhD thesis deals with the application of biomarkers and their compound-specific carbon isotope values in the archaeosphere. These techniques facilitate reconstructing the diet of past cultures and to trace animal husbandry practisess. Modern animal adipose fats and dairy fats from pigs, cattle, sheep, and goats from Ukraine can be distinguished by their δ13C values of palmitic (C16:0) and stearic (C18:0) acid. These individual fatty acids are also found in pottery vessels from Cucuteni-Trypillia culture, suggesting that most samples are from ruminant animal origin, but also from another potential source such as horses. Beside the animal fats, lipids indicative for beeswax have been detected in the pottery samples from Ukraine and Moldova, but also in ancient ceramic pots from the Wartberg culture of central Germany. Here, the individual lipid composition could be connected to the shape and function of most pots. In archaeological sites from the Baltic in Northern Germany, pottery use based its organic residue content could be compared between everyday use pottery from a domestic dwelling site (Oldenburg-Dannau) and specific grave gift pottery recovered from a nearby megalithic tomb (Wangels). Highly decorated, unglazed ceramic vessels from the Funnelbeaker and Globular Amphora culture were found as intact burial gifts containing cattle meat and milk fats, but no common cereals or aquatic resources, although located close to the shoreline. Additionally, a fatty acid distribution indicative for Sea Buckthorn oil was found in samples from exclusively the latest burial phase, which may have served as an exclusive burial gift. Contrary, the mainly undecorated pots from the coeval adjacent dwelling site Oldenburg-Dannau contained a mixed composition of plant and milk resources. Thus, the exclusive use of cattle meat in the burial indicate the important role of cattle in the ritual and spiritual sphere of Neolithic societies in northern Germany.

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Weber, Jan: Molecular Biomarkers in the Biosphere, Geosphere and Archaeosphere. 2020.

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