Development of an argillic horizon in polygenetic paleosols in the Marilia Formation (Maastrichtian), Brazil: Precautions for paleoenvironmental interpretation

Author(s)

Alves, Diego Sullivann de Jesus ; Ladeira, Francisco Sergio Bernardes ; Batezelli, Alessandro

• Document type: Journal article
• Source: CATENA; v. 210, p. 15-pg., 2022-03-01.

Abstract

A study of paleosols with argillic horizons found in the Marilia Formation associated with Maastrichtian in the Cretaceous is presented herein. This study aims to investigate the polygenetic processes involved in argillic horizon formation under paleoclimatic conditions from arid to semiarid in the Brazilian Cretaceous and considers morphological soil attributes, such as evidence of cementation, macromorphological data (horizons, matrix color, structure, clay coatings, nodules, and bioturbations), micromorphological data (coarse/fine patterns, b-fabric, clay coatings, infillings, and nodules), and water table oscillation. Seven representative profiles of pale-osols were selected in the Sao Paulo state, Brazil, and soil samples of lithified paleosols were collected to determine their macromorphological-micromorphological and chemical properties. Clay illuviation, carbonate accumulation, and gleization were dominant processes in the paleosols. Clay illuviation was identified from clay coatings along grain and ped surfaces. Carbonates occurred as nodules and rhizoliths and as coatings on peds. Red mottles, gray rhizohaloes with red oxidation rims, oxidic nodules, an iron-depleted matrix, and iron oxide depletion hypocoatings confirmed gleization. The argillic horizon polygenesis in the Marilia Formation is usually interpreted as evidence of high-moisture events under arid/semiarid climates or climate change toward moister conditions than arid/semiarid. Thus, argillic horizon paleosols in the sedimentary records of the Marilia For-mation are not necessarily reliquial characteristics of wet paleoenvironments but are associated with changes in dominant granulometry, types of macroaggregates-microaggregates, carbonate accumulation in horizons, and/ or water table oscillation. Thus, the presence of Bt horizons does not necessarily imply wet conditions with changes in the depositional system, as proposed by some authors. (AU)

• FAPESP's process: 15/17632-5 - Sedimentation and pedogenesis in Cretaceous continental sequences of the Bauru, Sanfranciscana, Parecis and Neuquén basins.
• Grantee: Alessandro Batezelli
• Support Opportunities: Regular Research Grants