Search Results (2)

Fossil resins from the area of Gulf of Gdańsk, Lublin area, Denmark, Bitterfeld, Lusatia and Ukraine, often grouped under the collective term ‘Baltic amber’, are complex organic mineraloids that have undergone various post-depositional transformations. Despite their role in paleontology as a source of for biological inclusions, fossil resins themselves are rarely analyzed as taphonomic objects. In this work, a new geochemical approach to fossil resin taphonomy is presented. Applying the van Krevelen diagram—traditionally used for kerogen classification—allows the diagenetic and catagenetic changes of fossilized resin maturation to be evaluated. Based on literature-derived elemental composition data of C, H, and O contents of ‘Baltic amber’, the diagram is interpreted as an organic matter transformation framework of fossil resins. The results suggest that the so-called ‘Baltic amber’ deposits represent a composite taphocoenoses of resins with different burial histories and maturation scenarios. This approach integrates petrological classification, geochemical maturation, and taphonomic analyses, offering a new way of “tracking” fossil resins maturation changes. Full article

Microbial mats represented the earliest complex ecosystems on Earth, since fossil mineralized examples (i.e., microbialites) date back to the Archean Eon. Some microbialites contain putative remains of organic matter (OM), however the processes and pathways that lead to the preservation of OM within microbialite minerals are still poorly understood. Here, a multidisciplinary study is presented (including petrographic, mineralogical and organic geochemical analyses), focusing on a modern calcifying mat from a hypersaline lake in the Kiritimati atoll (Central Pacific). The results show that this mat has a complex history, with two main growth phases under hypersaline conditions, separated by an interruption caused by desiccation and/or freshening of the lake. The mineral precipitates of the mat are predominantly aragonitic and two contrasting precipitation modes are observed: the main growth phases of the mat were characterized by the slow formation of irregular micritic particles with micropeloidal textures and subspherical particles, linked to the degradation of the exopolymer (EPS) matrix of the mat; whereas the interruption period was characterized by the rapid development of a thin but laterally continuous crust composed of superposed fibrous aragonite botryoids that entombed their contemporaneous benthic microbial community. These two precipitation modes triggered different preservation pathways for the OM of the mat as the thin crust shows a particular lipid biomarker signature, different from that of other layers and the relatively rapid precipitation of the crust protecting the underlying lipids from degradation, causing them to show a preservation equivalent to that of a modern active microbial community, despite them being >1100 years old. Equivalent thin mineral crusts occur in other microbialite examples and, thus, this study highlights them as excellent targets for the search of well-preserved biomarker signatures in fossil microbialites. Nevertheless, the results of this work warn for extreme caution when interpreting complex microbialite biomarker signatures, advising combined petrographic, mineralogical and geochemical investigations for the different microbialite layers and mineral microfabrics. Full article