Entwicklung einer neuen Präparationsmethode und Untersuchung verkieselter Mikrofossilien des Präkambriums mit Hilfe der Rasterkraft- und Elektronenmikroskopie
type: CreativeWork
description: In this thesis nanoscopic structure analysis is applied to precambrian microscopic fossils permineralised and bodily conserved in finegrained chert rock. For the first time atomic force microscopy (AFM) is used to image and analyse the three dimensional fine structure of the walls of single fossil unicells. Structural AFM data is complemented and backed by transmission electron microscopy yielding information on the crystalline nature and chemical composition of the quartz and the kerogen components of the fossil cell walls. The data is supplemented by raman spectra of the same single fossils, providing information on the molecular constitution of the kerogen material, as well as by quantitative electron microprobe data on the carbon content of the fossil cell walls. For AFM experiments a new preparation method was devised, using hydrofluoric acid to expose single fossils buried in the rock matrix. The method is applied to intact conventional thin sections of chert without disturbing the fossil cells in their environment, thus maintaining the petrographic context of the sedimentary structure. As AFM conventionally images surfaces that are smooth on a micrometer scale, the etching process has to be precisely adjusted in order to achive a balance between exposing cell walls well enough for structural examination and retaining surfaces smooth enough for the atomic force microscope. The cell walls produced by the etch method introduced here protrude from the surrounding rock matrix by approximately two microns. A detailed study of the etching behaviour by macroscopic and AFM analysis provides information on the dissolution speed of whole samples and of specific sites within the fossilmatrix compound. It is shown that etch resistivity depends on the crystal size and the carbon concentration around and within the fossil. Subject to examination were 850 million year old cyanobacteria from the Bitter Springs Formation of the Northern Territoriy, Australia, and 650 million y…
abstract: In this thesis nanoscopic structure analysis is applied to precambrian microscopic fossils permineralised and bodily conserved in finegrained chert rock. For the first time atomic force microscopy (AFM) is used to image and analyse the three dimensional fine structure of the walls of single fossil unicells. Structural AFM data is complemented and backed by transmission electron microscopy yielding information on the crystalline nature and chemical composition of the quartz and the kerogen components of the fossil cell walls. The data is supplemented by raman spectra of the same single fossils, providing information on the molecular constitution of the kerogen material, as well as by quantitative electron microprobe data on the carbon content of the fossil cell walls. For AFM experiments a new preparation method was devised, using hydrofluoric acid to expose single fossils buried in the rock matrix. The method is applied to intact conventional thin sections of chert without disturbing the fossil cells in their environment, thus maintaining the petrographic context of the sedimentary structure. As AFM conventionally images surfaces that are smooth on a micrometer scale, the etching process has to be precisely adjusted in order to achive a balance between exposing cell walls well enough for structural examination and retaining surfaces smooth enough for the atomic force microscope. The cell walls produced by the etch method introduced here protrude from the surrounding rock matrix by approximately two microns. A detailed study of the etching behaviour by macroscopic and AFM analysis provides information on the dissolution speed of whole samples and of specific sites within the fossilmatrix compound. It is shown that etch resistivity depends on the crystal size and the carbon concentration around and within the fossil. Subject to examination were 850 million year old cyanobacteria from the Bitter Springs Formation of the Northern Territoriy, Australia, and 650 million y…
author: Kempe, André
date published: 2003-01-29
date modified: 2026-07-24T02:51:44Z
provider: Ludwig Maxmilians Universität München
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Ludwig-Maximilians-Universität