Magnetic Mineral Characterization of Laterites From Peninsular India: Inferences on Their Genesis and Utility in Paleomagnetic and Paleoenvironmental Studies

Extensive laterite development on the equatorward‐drifting Indian subcontinent commenced shortly after the Deccan Volcanism (∼65 Ma). Thus, laterites record magnetic field directions of the post‐volcanic period and associated climatic shifts, including Indian monsoon evolution. Unlocking such records demands a thorough understanding of understudied laterite magnetic mineralogy. Here, we use a suite of magnetic methods, in combination with analytical scanning electron microscopy (SEM), to characterize the magnetic mineralogy of a laterite weathering profile from peninsular India. The magnetic mineral assemblage is dominated by authigenic superparamagnetic to single‐domain hematite and goethite, which display diverse shapes, sizes, and microcrystalline associations. Detrital (Ti, Cr) magnetite/maghemite are introduced externally via lateral groundwater and fluvial activity. First‐order reversal curve diagrams, non‐linear Preisach maps, and temperature‐dependent magnetic data sets are therefore characterized by a mixture of signatures from these mineral magnetic components. Such complexity likely results from of a combination of grain sizes, morphologies, and elemental substitution. With increasing degree of laterization we observe a gradual transition from goethite‐dominated associations in the lower saprolite zone, to hematite‐dominated associations in the upper duricrust. SEM analysis reveals magnetic mineral precipitation and dissolution cycles within an evolving weathering framework. We attribute this to the advancing weathering front and the sequential development of the subsequent lateritization zones as a result of alternating wet and dry monsoonal conditions in a tropical climate. Our study highlights the mineralogical complexity of the lateritization process and the need for detailed magnetic characterization before using laterites as reliable recorders of geomagnetic and environmental processes.