Puzzling Palaeobotanical Proxies: Comparing macro- and microbotanical data of two cores from Early Preboreal residual channel deposits from Anhamm, Niers-Rhine valley, Germany

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Puzzling Palaeobotanical Proxies: Comparing macro- and microbotanical data of two cores from Early Preboreal residual channel deposits from Anhamm, Niers-Rhine valley, Germany

Type: Research master thesis
Title: Puzzling Palaeobotanical Proxies: Comparing macro- and microbotanical data of two cores from Early Preboreal residual channel deposits from Anhamm, Niers-Rhine valley, Germany
Author: Wessel, Wolzak
Issue Date: 2017-08-30
Keywords: Preboreal
macrofossil analysis
comparative study
multiproxy
last glacial-interglacial transition
lake taphonomy
Anhamm
Niers
residual channel
macrobotany
Abstract: Among the palaeoecological proxies used, palynological analysis is commonly used for the climatic zonation to divide geological time periods. Often, single cores from lacustrine sediments are used to create a pollen diagram. Some of these pollen records are directly dated through the use of radiocarbon, other records are in an indirect way dated by correlation to pollen zones with a known date. In the asymmetrically-shaped Preboreal residual channel of Anhamm, in the Niers-Rhine valley in Germany, a zonation based on two cores, located roughly 8 meters apart, shows differences in the two pollen diagrams. The palynological analysis suggest a taphonomic bias on the cores, especially in the deepest core containing the longest record which is often chosen for sampling. The pollen assemblage from the deepest core, located near the outer cut bank of the residual channel, would have been influenced by local vegetation entrapping or blocking dispersed pollen grains. To find out more about the local conditions and possible taphonomic influence on the pollen assemblage, a macrobotanical analysis was conducted in this thesis. The aim was to compare the two cores within each palaeobotanical proxy, and to compare the data and eventual interpretation between the proxies. The thesis was based on two important questions: 1) What could be interpreted regarding palaeo-environmental reconstruction from the macrobotanical remains of the cores Anhamm-A and Anhamm-B, and 2) Comparing the data from the macrobotanical analysis with the palynological analysis, what problems might arise from interpreting the data considering palaeoenvironmental reconstructions? The approach was to get a detailed view of what palynological applications are used for, and which steps are taken from raw data to determine the boundaries for pollen zones. The former research on palaeoenvironmental studies on the Niers-Rhine valley were compared to this case study of Anhamm, and the former palynological analysis on the Anhamm cores was subsequently compared in different levels to the macrobotanical analysis. To conclude, the macrobotanical analysis shows a local vegetation development in a hydroseral succession, and suggests a discrepancy between tree macrofossils and microfossils in the middle part of both cores. The contrast gives an example of different outcome between proxies that affect the interpretation of the pollen-assemblage zonation of Anhamm. AMS-dates could offer more clarity in the different perspectives on the zonation, age and resolution of the residual channel deposits. For asymmetrical residual channel deposits, not only multiple cores should be used, but rather multiple proxies to set a stronger foundation in palaeoenvironmental reconstruction.
Supervisor: Field, Michael Hugh
Faculty: Faculty of Archaeology
Department: Archaeology (Research master)
Specialisation: Bioarchaeology
ECTS Credits: 35
Handle: http://hdl.handle.net/1887/52660
 

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