Vegetation and climate change in nortwestern South America were studied using pollen analysis in combination with XRF scanning on marine sediments of ODP Site 1239 from the East Equatorial Pacific comprising the interval between 4.7 and 4.2 Ma. The study site is sensitive to latitudinal shifts of the Intertropical Convergence Zone (ITCZ) shifts insofar as a southward (northward) shift would result in increased (decreased) precipitation over Ecuador. The presented pollen record (46 samples) comprises representatives from five ecological groups: lowland rainforest, lower montane forest, upper montane forest, páramo, and broad range taxa. A broad tropical rainforest coverage persisted in the study area throughout the early Pliocene, without significant open vegetation below the forest line. Between 4.7 and 4.42 Ma, humidity increases, reaching its peak around 4.42 Ma, and slightly decreasing again afterwards. The stable, permanently humid conditions are rather in agreement with paleoceanographic data indicating a southward shift of the ITCZ, possibly in response to closure of the Central American Seaway. The presence of páramo vegetation indicates that the Western Cordillera of the northern Andes had already reached considerable elevation by the early Pliocene. The trend in iron/potassium-ratios (Fe/K) is similar to the pattern of humidity inferred from the pollen spectrum, showing the highest values around 4.46 Ma, thus supporting the hydrological interpretation of the pollen record.

Supplement to: Grimmer, Friederike; Dupont, Lydie M; Lamy, Frank; Jung, Gerlinde; González, Catalina; Wefer, Gerold (2018): Early Pliocene vegetation and hydrology changes in western equatorial South America. Climate of the Past, 14(11), 1739-1754