Organic Geochemistry and Petrography

Left: Sediment core with abundant organic carbon; Right: Fluorescent hydrocarbon inclusions in a rock sample Source: BGR

In the Organic Geochemistry and Petrography sub-division BGR-scientists direct part of their work on a better understanding of organic-rich deposits. In addition to applied aspects advanced geochemical methods are used to reconstruct organic-rich palaeoenvironments.

Geochemistry of organic-rich shales and petroleum

Petroleum is still an important fossil energy and raw material resource and the investigation with organic geochemical methods are key tasks of the BGR.

BGR-scientists determine the amount and type of organic material as well as the content of organic carbon. The maturity of the rock material is assessed with the help of Rock Eval Pyrolysis. Additionally, with solvents the extractable portion of the organic matter is obtained and the composition of the extracts is studied after using chromatographic methods. The correlation of petroleum and source rocks and between petroleum for environmental issues is performed after chromatographic separation of petroleum extracts and the comparison of biomarker patterns (“fingerprint”) after applying coupled gas chromatography-mass spectrometry (GC-MS(MS)).

Organic material (Organic Petrography)

BGR scientists study and analyse different petrographic and -technological parameters of intact, oxidized, and thermally altered organic material with the aid of macro- and microscopic analyses.

The identification of type, origin and degree of preservation of the organic matter enclosed in sediments is realized using microscopic techniques, (i.e. incident light and fluorescence microscopy, confocal laser scanning microscopy (CLSM)).

The thermal maturity is determined by applying microphotometric analyses of huminite, vitrinite and bituminite reflectance. For this purpose, VIDABA, a vitrinite reflection database that has been compiled over many years, is maintained and further expanded. This database is used to characterise the regional geological subsidence history and the temperature distribution in the subsurface in various thematic fields of the BGR. Together with the quantification of maceral groups as well as fluorescence-microscopy data organic petrographic methods are used for projects directed on energy resources but also for paleoreconstructions or the reconstruction of paleotemperatures. Quality assurance certification covers participation in the ICCP DOMVR and SCAP Accreditation Programs since 2004, (https://www.iccop.org/accreditation/accredited-petrographers/).

Chemostratigraphy and reconstruction of organic-rich depositional settings (black shales)

Organic compounds may also be valuable signatures for reconstructions of palaeoenvironments. With the use of biomarkers and their quantities and isotopic properties BGR scientists can draw conclusions on the environmental conditions when the deposits were formed. This may help for a better understanding of potential source rocks and the conditions during the respective geological times.

For biomarker analyses extractions, hydrolyses, chromatographic fractionations, and GC-MS (GC-FID) as well as bulk and compound specific stable carbon isotope measurements are performed.