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TitleRaman spectroscopic analysis of carbonaceous matter and silica in the test walls of recent and fossil agglutinated foraminifera
AuthorMcNeil, D HORCID logo; Schulze, H G; Matys, E; Bosak, T
SourceAmerican Association of Petroleum Geologists Bulletin vol. 99, no. 6, 2015 p. 1081-1097,
Alt SeriesEarth Sciences Sector, Contribution Series 20140141
PublisherAmerican Association of Petroleum Geologists
Mediapaper; on-line; digital
File formatpdf
NTS107B; 107C; 108A; 108D
AreaBeaufort Sea; Mackenzie Delta
Lat/Long WENS-138.2500 -134.5000 70.2500 68.5000
Subjectsfossil fuels; analytical methods; spectroscopic analyses; carbonate; hydrocarbons; hydrocarbon maturation; thermal maturation; Foraminifera
Illustrationslocation maps; photographs; tables; spectra
ProgramGEM: Geo-mapping for Energy and Minerals Mackenzie Delta and Corridor
AbstractRaman spectroscopy has been used extensively in thermal maturation studies of kerogen, but has not been used to examine the maturation of organic cements in agglutinated foraminifera. Here, we utilize Raman spectroscopy to document the existence of carbonaceous matter and silica, in both Recent and fossil agglutinated foraminifera and to measure thermal alteration effects in fossil foraminifera. The distribution of carbonaceous matter through the test walls of agglutinated foraminifera suggests that this carbonaceous material is derived from primary organic cement and not from random contamination. Three broad stages of maturation are indicated in fossil specimens. (1) Immature specimens exhibit moderately strong fluorescence, low intensity Raman peaks (relative to fluorescence), and a tendency for the G-band to occur at lower wavenumbers. These attributes are consistent with the presence of disordered carbonaceous matter with minor organic degradation. (2) Mature samples (oil window) exhibit high fluorescence, increased relative D- and G-band intensities, and a decrease in the D:G band ratio, suggesting increasingly ordered carbonaceous matter and substantial organic degradation. (3) Post-mature samples exhibit low levels of fluorescence and high relative D- and G-band intensities, a tendency for the G-band to be located at higher wavenumbers, an increase in the D:G band ratio, and an increase of the silica peak¿s relative intensity. This stage is consistent with the presence of highly-ordered carbonaceous and siliceous matter. These findings indicate that Raman spectroscopic analysis can be used as a quick and easy tool to assess thermal maturity and estimate optimal temperatures for hydrocarbon generation using fossil agglutinated foraminifera.
Summary(Plain Language Summary, not published)
Recent advancements have made Raman spectroscopy accessible to a broad scientific community. It can be used to determine the composition of almost any material, but it is under-utilized in geoscience. A laser beam is focused on an object; analysis of the wave lengths of the energy given off determines chemical characteristics. We use it here to analyze microscopic fossil organic matter in foraminifera. These microfossils are widespread in sedimentary rocks and are used to interpret the geological history of hydrocarbon basins. Using Raman microscopy, we documented progressive geothermally controlled changes in organic matter in the Beaufort-Mackenzie Basin. This confirms the usefulness of Raman spectroscopy in petroleum exploration and provides a new methodology to predict favourable sites for the generation of hydrocarbons (i.e., recognizing the "oil window").

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