Neoproterozoic to Cambrian transition

The Neoproterozoic belongs to a handful of time periods when Earth experienced dramatic environmental changes. The response to, and recovery from, at least two severe glaciations, punctuated by warmer climates represents an acute test of feedbacks within the Earth system to produce and maintain a life-sustaining environment. Within the last years we collected a unique isotope data set for Neoproterozoic (Cryogenian to Ediacaran) carbonate sections associated with glacial deposits in Namibia, Kazakhstan and China. B isotope pattern recovered from Neoproterozoic post-glacial carbonates identified a global and temporary ocean acidification event potentially linked to oceanic uptake of CO2. Ca and Mg isotope excursions elucidate the recovery of the Earth System from such an ocean acidification event. Both isotope patterns indicate an enhanced weathering influx following the glaciation demise, which enabled the ocean to return to normal pH after climatic amelioration. Differences in time-development of the isotope patterns reflect a change from carbonate- to silicate-dominated weathering flux and suggest primary dolomite formation during “cap dolostone” sedimentation.

The Ediacaran to Cambrian transition is characterized by substantial changes in ocean-atmosphere interactions, climate, tectonics and biogeochemical processes that presumably catalysed the advent and radiation of metazoa. To get a detailed insight into changing ocean pH and weathering conditions during the first appearance and the subsequent rapid spreading of multicellular animal life, we generated B, Li and Sr isotope records from carbonate successions in China and Kazakhstan. The multi-proxy isotope record documents dramatic changes in ocean geochemistry pointing to temporary acidic and euxinic to anoxic shallow-water conditions that might have poisoned the Ediacaran Fauna and led to mass extinction during the terminal Ediacaran.

Condon, D.J., Boggiani, P., Fike, D., Halverson, G.P., Kasemann, S., Knoll, A.H., Macdonald, F.A., Prave, A.R., Zhu, M. (2015). Accelerating Neoproterozoic research through scientific drilling. Scientific Drilling 19, 17-25.

Gamper, A., Struck, U., Ohnemueller, F., Heubeck, Ch., Hohl, S. (2015). Chemo- and biostratigraphy of the Gaojiashan section (northern Yangtze platform, South China): A new Pc-C boundary section. Fossil Record 18(2), 105-117.

Wood, R.A., Poulton, S.W., Prave, R.A., Hoffmann, K.-H., Clarkson, M.O., Guilbaud, R., Lyne, J.W., Tostevin, R., Bowyer, F., Penny, A.M., Curtis, A., Kasemann, S.A. (2015). Dynamic redox conditions control late Ediacaran metazoanecosystems in the Nama Group, Namibia. Precambrian Research 261, 252–271.

Kasemann, S.A., Pogge von Strandmann, P.A.E., Prave, A.R., Fallick, A.E., Elliott, T., Hoffmann, K.H. (2014) Continental weathering following a Cryogenian glaciation: Evidence from calcium and magnesium isotopes. Earth and Planetary Science Letters 396, 66–77.

Ohnemüller, F., Prave, A.R., Fallick, A.E., Kasemann, S.A. (2014) Ocean acidification in the aftermath of the Marinoan glaciation.Geology, doi:10.1130/G35937.1.

Kasemann SA, Prave AR, Fallick AE, Hawkesworth CJ, Hoffmann KH (2010) Neoproterozoic ice ages, boron isotopes and ocean acidification: Implications for a snowball Earth. Geology, 38, 775-77.

Kasemann, S.A., Hawkesworth, C.J., Prave, A.R., Fallick, A.E., Pearson, P.N. (2005). Boron and calcium isotope composition in Neoproterozoic carbonate rocks from Namibia: evidence for extreme environmental change. Earth and Planetary Science Letters 231, 73-86.