Electronic Thesis and Dissertation Repository


Master of Science




Dr. Fred J. Longstaffe


Organic matter (OM) adsorbed to clay minerals in soils can have C/N similar to lacustrine algal matter. Accurate source identification of OM in sediments is crucial for predicting future climate change impacts in the Great Lakes region. We analyzed C/N, carbon-isotope compositions, n-alkane abundances and compound-specific carbon-isotope compositions of vegetation, soil, and OM associated with clay minerals in soils and glacial till in order to determine if (i) OM associated with clay minerals has unique signatures distinct from lacustrine algal matter and is traceable to modern vegetation, and (ii) if these signatures have been transferred to and preserved in Great Lakes sediments since the last glaciation. OM associated with clay minerals exhibits δ13C of ~ –28.5‰ and δ13Cn-alkane of –31.5‰; together with together with C/N >10 (but much <20) and n-alkane relative abundance distributions, these signatures are good proxies for C3 OM sources from higher plants in soils and glaciolacustrine sediments.