First Record of Soft Tissue Preservation in the Upper Devonian of Poland

Textural characteristics and geochemical composition of a tropical coastal marine sediment: a case study of transgressive mud beach, Bight of Benin, Nigeria

The study determines the textural characteristics and geochemical composition of the transgressive mud coastal marine sediments of the Bight of Benin, Nigeria. The sediment samples were collected using a VanVeen grab sampler from three onshore and three offshore locations. The particle size analysis was conducted with a combination of the pipette sampling and wet sieving of the fraction > 62-µm method, while the concentrations of major oxides were determined by employing X-ray fluorescence technique. The onshore and offshore sediment samples were composed of 54% silt and 30% sand (sandy silt) and 45% sand and 31% clay (clayey sand), respectively. The sequence of concentrations of major oxides was SiO₂ > CaO > Al₂O₃ > Fe₂O₃ > Na₂O > MgO > K₂O > TiO₂ > P₂O₅ > MnO. Chemical classification scheme of the sediment sampled was Fe-shale. The range of SiO₂/Al₂O₃ and K₂O/Na₂O ratios of the onshore sites was 5.59-6.74 and 0.31-0.32, respectively, while of the offshore site was 6.19-6.99 and 0.32-0.46, respectively, indicating a low-to-moderate sediment recycling. K₂O/Al₂O₃ ratios were low across the sampling sites suggesting abundance of aluminosilicates. The values of weathering indices consisting of Plagioclase Index of Alteration (PIA), Index of Composition Variations (ICV), Chemical Index of Weathering (CIW), and Chemical Index of Alteration (CIA) were similar and varying from low to moderate. Principal component factor analysis (PCFA) extracted three factors for onshore and offshore data with factor loading of clay with MnO, K₂O, and Fe₂O₃ contents in the offshore sediments while onshore were loaded with CaO, MnO, Al₂O₃, and Fe₂O₃ with sand. Geochemical characteristic signified a mixed nature of provenance of both terrigenous and lithogenous sources for onshore and offshore sites respectively.

Coincidence of photic zone euxinia and impoverishment of arthropods in the aftermath of the Frasnian-Famennian biotic crisis

The lowermost Famennian deposits of the Kowala quarry (Holy Cross Mountains, Poland) are becoming famous for their rich fossil content such as their abundant phosphatized arthropod remains (mostly thylacocephalans). Here, for the first time, palaeontological and geochemical data were integrated to document abundance and diversity patterns in the context of palaeoenvironmental changes. During deposition, the generally oxic to suboxic conditions were interrupted at least twice by the onset of photic zone euxinia (PZE). Previously, PZE was considered as essential in preserving phosphatised fossils from, e.g., the famous Gogo Formation, Australia. Here, we show, however, that during PZE, the abundance of arthropods drastically dropped. The phosphorous content during PZE was also very low in comparison to that from oxic-suboxic intervals where arthropods are the most abundant. As phosphorous is essential for phosphatisation but also tends to flux off the sediment during bottom water anoxia, we propose that the PZE in such a case does not promote the fossilisation of the arthropods but instead leads to their impoverishment and non-preservation. Thus, the PZE conditions with anoxic bottom waters cannot be presumed as universal for exceptional fossil preservation by phosphatisation, and caution must be paid when interpreting the fossil abundance on the background of redox conditions.

The first direct evidence of a Late Devonian coelacanth fish feeding on conodont animals

We describe the first known occurrence of a Devonian coelacanth specimen from the lower Famennian of the Holy Cross Mountains, Poland, with a conodont element preserved in its digestive tract. A small spiral and phosphatic coprolite (fossil excrement) containing numerous conodont elements and other unrecognized remains was also found in the same deposits. The coprolite is tentatively attributed to the coelacanth. Although it is unclear whether the Late Devonian coelacanth from Poland was an active predator or a scavenger, these finds provide the first direct evidence of feeding on conodont animals by early coelacanth fish, and one of the few evidences of feeding on these animals known to date. It also expands our knowledge about the diet and trophic relations between the Paleozoic marine animals in general.