Reconstruction of Ediacaran to Early Cambrian ocean pH and weathering conditions

Abstract

This dissertation deals with the reconstruction of ocean pH conditions and the quantification of weathering rates by boron and strontium isotope analyses on Ediacaran and Early Cambrian marine carbonate rocks. In order to compare local signals and specific features with global patterns, a variety of sections on two different palaeo continents (China, Kazakhstan) were examined and compared to data from the Namibian Congo craton. The entire Ediacaran and Early Cambrian was characterized by minor to major ocean pH fluctuations and a general increase in weathering rates and fluxes to the ocean. Ocean acidification events are indicated for the aftermath of the Marinoan glaciation as well as for the Precambrian-Cambrian boundary. The changes in ocean pH and weathering rates had a significant influence on ocean geochemistry and may have decisively contributed to the creation of new ecological niches, possibly enabling the appearance of multicellular animals and reinforcing their radiation.