Weathering and paleoprecipitation indices in a Late Pleistocene–Holocene loess–paleosol sequence in central Argentina

Abstract

A Late Pleistocene–Holocene loess–paleosol sequence in central Argentina was studied to obtain a weathering insight and to probe geochemical tools as paleoclimatic proxies. Three paleosols and a buried soil interlayered with loess mantles compose Corralito I sequence (32°00′7″ S, 64°11′08″ W, 469 m a.s.l). Several weathering indices (CIA, CIA-K, and LWI) and elemental ratios (∑Bases/Al2O3, Rb/Sr, CaO/TiO2, Na2O/TiO2) were calculated. An incipient weathering degree throughout the sequence was detected, denoting that the parent material (i.e., loess mantles) has not been substantially modified by pedogenesis. Although a statistically significant correlation between magnetic susceptibility and several weathering indices was identified, the weathering intensity was not strong enough to produce a decrease in the magnetic signal of the paleosols, which is, in part, inherited from the detrital fraction. Paleoprecipitation indices, calculated using geochemical data, suggest slightly wetter conditions during paleosol formation when compared to loess. Paleosols were formed during humid conditions (paleosols II and II during MIS 5e, and paleosol I during MIS 3) with sedimentation pause and soil development, whereas loess layers were deposited during more arid conditions.