Soils, Chemical Weathering, and Climate Change in Earth History
Abstract
Earth’s changing climates, landscapes, and atmospheres are recorded in paleosols, which form in the Earth’s critical zone by interactions between the lithosphere/pedosphere, biosphere, atmosphere and hydrosphere. Weathering during much of the Precambrian Eon was dominated by very high pC02 (10x to >20x present atmospheric level, PAL) leading to acidic chemical weathering, with additional and very poorly constrained weathering influences of primitive biota. The Great Oxidation Event at 2.0-2.2 Ga was marked by a major increase in p02, which was still very low compared to modern conditions. Towards the end of the Precambrian (Neoproterozoic) at least two major Snowball Earth glaciations occurred, punctuated by rapid warming, which intensified weathering processes, leading to releases of nutrients to oceans and the Cambrian Explosion and diversification of life. By the early Paleozoic the first nonvascular land plants evolved; these were small in stature, lacked deep root systems, were spore-reproducing, and were limited to wet soil environments. They were followed by the arrival of invertebrate terrestrial soil organisms. By the Middle to Late Devonian, trees with deep-penetrating root systems evolved that accelerated weathering and soil formation through the release of organic acids, which enhanced clay production. Coincident with afforestation, a significant drop in pC02 (at or below PAL) and concomitant rise in p02 (for a time exceeding PAL) culminated at the end of the Paleozoic Era with widespread Carboniferous coal swamps. Paleosols record the end-Permian mass extinction and the Cretaceous-Paleogene mass extinction and complement the marine records of these events. The Paleocene-Eocene Thermal Maximum (PETM), a transient 200 kyr warming spike attributed to release of methane hydrates, is considered the closest ancient analog to modern climate change. Evolution of angiosperms (flowering plants) in the Cretaceous, and C4 grasses in the Miocene, record increasing diversification of land plant strategies and ability to occupy all known major terrestrial ecological niches.
Publication Title
Hydrogeology, Chemical Weathering, and Soil Formation
Recommended Citation
Driese, S., Nordt, L., & Stinchcomb, G. (2021). Soils, Chemical Weathering, and Climate Change in Earth History. Hydrogeology, Chemical Weathering, and Soil Formation, 23-65. https://doi.org/10.1002/9781119563952.ch2
