Section Palynology and Microvertebrata of the Palaeozoic
Palynology and Microvertebrata of the Palaeozoic
Palynology is a branch of science which belongs both to the geology and palaeontology but also to the botany. The name derives from the Greek meaning in the original sense “doctrine of disseminated dust”.
In contrast to recent research (mostly on pollen, spores and dinoflagellates), the palaeo-palynology is interested in the extinct plant and animal organic-walled microfossils (OWM).
Palynomorphs are important tools for determining the age of sediments and provide information on their life and depositional environment and paleoclimate. The following examples show typical representatives of Paleozoic aquatic and terrestrial OWM derived from the actual research activities.
For all fossil palynomorphs to be preserved in sediments it is important that they are made of highly resistant organic compounds such as the bioploymer sporopollenin. As they exhibit a large potential of fossilization against thermal, chemical, and physical destruction, palynomorphs are preserved over long geological periods. The oldest known OWM are those from the Precambrian, although in our section we deal primarily with the Palaeozoic microfossils mainly from the Ordovician to Devonian, which date from the period of about 490 to 360 million years before present. Post-Palaeozoic studies are recently integrated as well.
Within this category lie the pteridophytic-spores and cryptospores (a special group of OWM, most probably related to first land plant spores). Cryptospores are known since the Middle Ordovician (Caradocian), whereas the “true” trilete spores (e.g. miospores) occur in the Silurian.
Studies on plants remains (phytoclasts), such as cuticles, tracheides and vascular bundles, and early animal cuticles, such as arthropods and insects still play a minor role in palynology.
The most important representatives of the marine phytoplankton (in the Palaeozoic) are acritarchs (mostly marine algal cysts) and prasinophytes (phycomata of green algae). Well-known examples include genera such as Cymatiosphaera, Dictyotidium, Leiosphaeridia and Tasmanites. The oldest record of acritarchs and prasinophytes is dated back to the Proterozoic. However, freshwater forms of phytoplankton in the Paleozoic play only a minor role. The illustrated chloroccale alga Plaesiodictyon mosellanum (Upper Muschelkalk, Triassic) probably originates close to lakes or river systems. Zooplankton representatives include chitinozoans and scolecodonts. Chitinozoans are an extinct microfossil group of uncertain origin, they are known from the Ordovician to upper Devonian. Scolecodonts are recorded since the Cambrian, they show morphologically different teeth shaped forms and represent masticatory apparatus of early worms, by analogy, they are mainly affiliated to polychaetes (bristle worms).
The approximately 5 – 300 microns fossil OWM are typically found in and extracted from fine-grained sedimentary rocks such as shales, siltstones or marlstones. After mechanical crushing, the bedrock is chemically processed, following the standard palynological methods with hydrochloric acid (HCl) and hydrofluoric acid (HF). These chemicals dissolve calcareous and siliceous components (matrix) and the organic material including the OWM remains. This organic concentrate (kerogen) is sieved through very fine meshes and with this procedere the OWM are enriched. Thereafter, the obtained palynomorphes are mounted on slides and examined under light or scanning electron microscopes, and in special cases, infrared, fluorescence and confocal microscopic examinations are applied.
In general, a quantitative as well as a qualitative assessment of the individual palynomorphs is performed. Taxonomic investigation of the various forms allows to establish a temporal (stratigraphic) position of the studied sediments. For example, acritarchs and chitinozoans provide excellent index fossils during the Paleozoic. The analysis of the overall composition of the organic components in the sediments (palynofacies analysis) helps in the interpretation of prevailing environmental conditions at the time of deposition and to some extent, climatic data can also be deduced. Therefore, palynomorphs are ideal paleo-environmental indicators and provide. in combination with sedimentology and organic geochemistry important proxies for palaeoecology, palaeoenvironmental and palaeoclimate interpretations. In our research, we apply palynology as an important tool to characterize terrestrial and marine sediments, and thus to compare and to correlate the corresponding depositional environments.
Due to increased importance of palynology in the framework of the Palaeozoic research at the Senckenberg Research Institute, palynology as a research field, was established with the new section Palynology and Microvertebrates of the Palaeozoic. It took place in October 2005 connected with the retirement of the former head of the section Paläozoologie I, Dr. G. Plodowski, replaced by Dr. R. Brocke as the new head of this section.
The existing collection of fossil vertebrates (agnathans, fishes, reptiles, birds, mammals, excluding small mammals and Messel fossils), coprolites, trace fossils, sedimentary marks and problematica remains under the curatorship of the new head of the section, and are expanded by the new collection of Palaeozoic palynomorphs.
The former section Paläozoologie I was established in the years 1966/67 (here named as Paläozoologie II) caused by internal restructuring of the geological division. Later on it was renamed as Paläozoologie I, and parts of the original collection e.g. fossil sponges and calcareous algae, general geology, mineralogy, petrography were relocated to other sections. Finally, in 1969, with the establishment of the section Mammalogie II, the collection of small mammals was excluded from the fossil vertebrate collection.