The Devonian Period (~360 to ~420 million years ago) was an important time interval for major evolutionary changes, yet it was also environmentally volatile. The evolution of forests and tetrapods during the Devonian marks the onset of the landscapes and lifeforms we are familiar with today. However, this was also a time of biocrises: perturbation intervals comprised of repeated and rapid (bio)events that can include climatically-driven extinctions and corresponding sea level and carbon cycle fluctuations.
In the Beloit Paleo Lab, we use an integrated stratigraphic approach (litho-, chemo-, bio-, and sequence stratigraphy) to constrain the timing of carbon cycle perturbations and other environmental changes associated with Devonian biocrises. We've recently undertaken a ACS PRF-funded project on black shales in the Appalachian and Illinois Basins, and are starting a complimentary project in the Michigan Basin that is funded by the Keck Geology Consortium.
Brett, C., Zambito, J., McLaughlin, P., and Emsbo, P. (2020) Revised perspectives on Devonian biozonation and environmental volatility in the wake of recent time-scale revisions, Palaeogeography, Palaeoclimatology, Palaeoecology, 549:108843. https://doi.org/10.1016/j.palaeo.2018.06.037
Brett, C., Zambito, J., Baird, G., Aboussalam, S., Becker, T., and Bartholomew, A. (2018) Litho-, Bio-, and Sequence Stratigraphy of the Boyle-Portwood Succession (Middle Devonian, Central Kentucky, U.S.A., Palaeobiodiversity and Palaeoenvironments, 98(2):331-368, https://doi.org/10.1007/s12549-018-0323-6
Zambito, J., M. Joachimski, C. Brett, G. Baird, and Aboussalam, S. (2016) A carbonate carbon isotopic record for the late Givetian (Middle Devonian) Global Taghanic Biocrisis in the type region (northern Appalachian Basin), In Becker, R. T., Königshof, P. & Brett, C. E. (eds.) Devonian Climate, Sea Level and Evolutionary Events. Geological Society, London, Special Publications, 423:223-233, http://doi.org/10.1144/SP423.7
Permian Climate and Extreme Environments
The mass extinction at the Permian – Triassic Boundary, which occurred ~252 million years ago, is recognized as the most devastating extinction in Earth’s history (>80% of all genera went extinct). While the extinction itself has been studied extensively, the climatic changes beforehand, when Earth transitioned from Icehouse to Greenhouse conditions during the Late Paleozoic deglaciation, are not as well understood. Importantly, this climatic shift is arguably the best analog for the long-term effects of current anthropogenic climate change and ice sheet melting.
In the Beloit Paleo Lab, we study the extreme continental conditions leading up to and after the extinction event, in particular, hot, arid saline lake and mud flat environments. In particular, we use fluid inclusions within salt that precipitated in these settings to reconstruct lake water temperatures which are a proxy for paleoweather, and when studied in time succession allow us to make interpretations about paleoclimatic changes. As part of this line of research, we are participating in the Deep Dust scientific drilling project.
Soreghan, G., Beccaletto, L., Benison, K., Bourquin, S., Hamamura, N., Hamilton, M., Heavens, N., Hinnov, L., Huttenlocker, A., Looy, C., Pfeifer, L., Pochat, S., Sardar Abadi, M., Zambito, J., and the 2019 Deep Dust workshop participants (2020) Report on ICDP Deep Dust workshops: Probing Continental Climate of the Late Paleozoic Icehouse-Greenhouse Transition and Beyond, Scientific Drilling, 28:93-112. https://doi.org/10.5194/sd-28-93-2020
Benison, K., Zambito, J., and Knapp, J. (2015) Contrasting siliciclastic-evaporite strata in subsurface and outcrop: an example from the Permian Nippewalla Group of Kansas, U.S.A., Journal of Sedimentary Research, 85(6):626-645. https://doi.org/10.2110/jsr.2015.43
Zambito, J. and Benison, K. (2013) Extreme High Temperatures and Paleoclimate Trends Recorded in Permian Ephemeral Lake Halite, Geology 41(5):587-590. https://doi.org/10.1130/G34078.1
Environmental Impacts of Sand Mining
Industrial sand has many uses including glass making, for molds in foundry processes, and as frac sand (proppant) in the hydraulic fracturing process for extracting unconventional petroleum resources. Wisconsin is one of North America’s leading producers of frac sand, which is primarily mined from Cambrian-age quartz sandstones deposited ~500 million years ago. During the mining process, there is the potential to leach sulfide and iron (hydr)oxide cements within these sandstones and release their trace metal constituents to surface water and lower the pH; this is essentially a mild form of acid-mine drainage. The potential for environmental impacts has recently increased as mine sites now sit idle during a mining cycle ‘bust’. Furthermore, these same sandstones, where buried at depth, are a regional aquifer. As the water table fluctuates due to increased groundwater withdrawal and/or climate change, these sulfide and iron (hydr)oxide cements may break down and contaminate groundwater with trace metals.
In the Beloit Paleo Lab, we have undertaken a variety of projects to characterize the geochemistry and mineralogy of these sandstones, and understand the origin of any trace metals present within the context of Cambrian depositional environments and subsequent diagenesis.