Profile
Dr Clemens Vinzenz Ullmann
Research
My research focuses on the use of geochemical techniques to extract information about past environments from fossil shells. This palaeoenvironmental research is intimately connected with studies on biomineralization and diagenesis as well the development of new techniques and proxies to tell about past environmental conditions and the ecology of extinct organisms.
Geochemistry of biomineralization
Shell material bears the structural and geochemical imprints of the animal that secreted it, and it is often characterised by multiple shell structures (such as the different shell structures of modern oysters shown below) and correspondingly complex shell geochemistry. Understanding, and making use of such compositional and structural variability permits extracting much more detailed and reliable information about past environmental conditions.
Fossil diagenesis
Much of the general processes and geochemical changes to fossils associated with diagenesis have been established in the 1970s and 1980s, but technological progress has enabled much more rapid analysis of ever smaller sample quantities as well as novel proxies helping to understand diagenetic processes specific to each sedimentary succession and type of fossil, such as the slightly crushed, cemented Late Triassic brachiopod from New Caledonia shown below. Investigating species-specific diagenesis at each studied locality improves the robustness of environmental reconstructions substantially.
Reconstructing palaeoenvironment and ecology
The modes of life of extinct organisms can be very tricky to reconstruct, especially when no similar modern species are still alive. Ecology can have a strong influence on how geochemical proxies are recorded in their shells and this in turn complicates making inferences about palaeoenvironmental conditions. For example, the two fossil brachiopod species from the Toarcian (Early Jurassic) of Spain shown below are interpreted to have differing ecologies based on their different shell structure and geochemistry, with Soaresirhynchia likely having had a slower metabolism and slower shell growth. Adding geochemical and shell structure information to the tool box of palaeontologists to better constrain palaeoecology is a new and exciting field of research.
