 Across faunal and paleoindian hunting sites, evidence existed of carbon-rich “black mats” that were around 30 cm in thickness, suggesting an abrupt change that occurred in a small time window and a rise in aquatic conditions.Brakenridge also discusses pollen-core research that suggests global cooling conditions not to have just occurred in the northern latitudes, but also latitudes as far as 41°S.Tree-ring evidence shows a rise in 14C cosmogenic isotope.