Pedodiagenetic Characterization of Cretaceous Paleosols in Southwest Minas Gerais, Brazil

Abstract

ABSTRACT:The influence of post-burial geological processes on preserving pedogenic properties has great importance in identifying ancient paleosols both in the field and in a laboratory. However there are not many publications that focus on characterizing paleosol diagenesis. As temperature and pressure progressively increase, evidence of pedogenesis is modified and destroyed, hindering paleoenvironment characterization and interpretation. This paper discusses diagenetic evidence and its relation to strictly pedogenic features, like structure, cements, nodules, and neoformation of clay minerals using the carbonate paleosols of the Marília Formation in the upper unit of the Bauru Basin as a case study. Despite the long geotectonic and thermal history of the Marília Fomation, paleosols bring us pedogenic evidence that can undergo micromorphological analyses, such as cementation, clay illuviation, bioturbation, and ped structures. The results of analyses in 25 paleopedogenic horizons indicate that the paleotopographic features were responsible for distribution of the diagenetic processes and preservation of the paleosol properties. The maturity of those paleosols controls lithification. In mature paleosols that developed in more stable portions of the landscape, characteristics such as carbonate cementation and development of pedogenic structures are the main factors that inhibit diagenesis. However diagenetic processes that influence poorly-developed paleosols are controlled by depositional characteristics and by changes in the water table, enabling more advanced diagenetic processes, compared to mature paleosols.

Facies and palaeosol analysis in a progradational distributive fluvial system from the Campanian–Maastrichtian Bauru Group, Brazil

“…In recent decades, the study of the palaeosols has been emphasized in sedimentological analysis and palaeoenvironmental evolution (e.g. Suguio et al., ; Fernandes, ; Ladeira et al., ; Dal'Bo et al ., ; Fernandes, ; Pereira et al., ; Silva et al., ; Silva et al ., ; Basilici et al ., ; Nascimento et al ., ; Silva et al ., ,b,c).…”

Micromorphology of Paleosols of the Marília Formation and their Significance in the Paleoenvironmental Evolution of the Bauru Basin, Upper Cretaceous, Southeastern Brazil

“…Paleosols have been used both in analysis and paleoenvironmental reconstructions (Andreis, 1981;Catt, 1990;Retallack, 2001;Sheldon and Tabor, 2009;Nascimento et al, 2017) by forming themselves into open systems capable of recording environmental conditions during their training, as in stratigraphic correlation (Brown and Kraus, 1988;Wright, 1992;Marriott and Wright, 1993;Kraus 1997;McCarthy and Plint, 2003), indicating a stable surface and representing moments of pause in erosion and deposition.…”

Freshwater Decapoda trace fossils in floodplain paleosols of Marilia Formation in Minas Gerais State (SE Brazil)

“…The trace fossils described in this work occur in the paleosols of the Marilia Formation from the Upper Cretaceous (Maastrichtian) located in western Minas Gerais State (MG), southeastern Brazil (Figure 2), and were described in detail by Batezelli (2015) and Nascimento et al (2017b). The Marilia Formation in the study area consists predominantly of sandstones and matrix-supported conglomerates, subordinated sandy-clay deposits, and CaCO 3 rich paleosols (calcretes).…”

“…The lithostratigraphic sections range from 5 to 15 m in height and are located near of Campina Verde, MG (19° 40.065'S, 49°60.405'W) (Figure 2). They were studied in detail by Batezelli (2015) and Nascimento et al (2017b).…”

“…The depositional architectures of the Marilia Formation are associated to river channels, lenticular sandbars and floodplain elements (e.g. Miall, 1996), constituting amalgamated channel complexes, interspersed with paleosols (Batezelli, 2015;Nascimento et al, 2017b).…”