Abstract
ABSTRACT Deduction of associated paleoenvironments and paleoclimate, definition of the chronosequence of paleosols, and paleogeographic reconstruction have become possible through the application of micromorphology in paleopedology. Micromorphology has also been useful in recognition of weathering processes and definition of minerals formed in succession. In this respect, the objective of this study was to identify the development of pedogenic processes and discuss their significance in the paleoclimate evolution of the Marilia Formation (Maastrichtian) of Bauru Basin. Three sections of the Marilia Formation (A1, A2, and A3) were described, comprising nine profiles. Micromorphologic al analysis was carried out according to the specialized literature. In the Marilia Formation, the paleosols developed in sandstones have argillic (Btkm, Bt) and carbonate (Bk) horizons with different degrees of cementation, forming mainly calcretes. The evolution of pedogenic processes, in light of micromorphological analysis, evidenced three moments or stages for the genesis of paleosols with Bkm, Btk, and Bt horizons, respectively. In the Maastrichtian in the Bauru Basin, the paleosols with Bkm are older and more arid environments, and those with Bt were formed in wetter weather, but not enough to lead to the genesis of enaulic-related distributions, typical of current Oxisols.
Highlights
Micromorphology or micropedology can be defined as the branch of soil science that deals with the description, interpretation and, to some extent, the measure of soil constituents, features, and fabrics at the microscopic level (Bullock et al, 1985)
The transformation of saprolite to soil, called pedoplasmation, is another topic that can be studied by micromorphology, as it concerns in the first place the transformation of fabrics, initially without mineralogical or chemical changes (Stoops, 2008)
The Bauru Basin developed in the Upper Cretaceous in a period after breakup of the Gondwana continent, and completion occurred in a climate with variations from semi-arid to arid between the Campanian (83.6 to 72.1 Ma B.P) and Maastrichtian (72.1 to 66 Ma B.P.) (Batezelli, 2015)
Summary
Micromorphology or micropedology can be defined as the branch of soil science that deals with the description, interpretation and, to some extent, the measure of soil constituents, features, and fabrics at the microscopic level (Bullock et al, 1985). The identification of different constituents of the soil in different fractions, as well as definition of possible interrelationships between them, is another key objective of micromorphology (Castro et al, 2003). One of the applications of micromorphology is to identify the pedogenetic process and display transfers and concentrations of elements (eluviation, illuviation, nodulation, or concretion) and to follow the development of distinctive features (porosity and pedoturbation, among others). It can be applied in recognition of the weathering process involved and the mineral succession formed (Delvigne, 1998). The transformation of saprolite to soil, called pedoplasmation, is another topic that can be studied by micromorphology, as it concerns in the first place the transformation of fabrics, initially without mineralogical or chemical changes (Stoops, 2008)
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