Paleozoic Environmental Change

The Silurian was a time of intense climatic instability and biotic turnover that occurred on the heel of one of the largest mass extinction events in Earth history. Studies have indicated that this ~30 Myr interval sustained several pronounced episodes of paleoenvironmental change that are evidenced by repetitive large-scale global geochemical perturbations in inorganic and organic carbon, and oxygen; as well as strong fluxes in eustatic sea level, thought to reflect stratified oceans with highly variable paleowater temperatures (Cramer et al., 2015 and references therein). Studies have shown a connection between these geochemical anomalies and instances of higher biotic turnover in several taxonomic groups, thus exemplifying the significance of these events (Jeppsson, 1990; Samtleben et al., 1996; Azmy et al., 1998; Munnecke et al., 2003; Kaljo et al., 2003; Lehnert et al., 2010; Noble et al., 2012; McAdams et al., 2017 and others). However, it is currently debated whether these paleoenvironmental disruptions were brought-on by either periodic growth of continental ice sheets during episodes of global cooling or by varying cycles of humidity and aridity (Cramer et al., 2015). This is relevant because at present, anthropogenic greenhouse gas emissions are hypothesised to push the Earth into a state of accelerated global warming, oceanic anoxia and mass extinction. Therefore, in order to increase our predictive models, the investigation of similar ancient events is of critical importance.

Ongoing work at P.E.R.L. focuses on providing answers to some of these basic questions. Using a collection of rock core stored at the Michigan Geological Repository for Research and Education, we are  specifically engaged in utilizing these cores by collecting a wealth of multi-proxy data, whereby various stable isotope records are being derived across this abrupt rock transition to assess different aspects of paleoenvironmental change in the Silurian Michigan Basin (Figure 1). Pictures here show rock cores of the Silurian Salina Group strata, representing the prolonged interval of evaporite (i.e. salt) mineral deposition.