Publication date: 15 May 2017
Source:Geoderma, Volume 294
Author(s): S.M. McLennan, D. Giles, S.M. Hill
Ferricrete – sediment cemented by iron oxides and hydroxides – is common in subaerial weathering environments around the world. Formed under alternating oxidising and reducing conditions, ferricretes record pedogenetic processes of translocation and concentration of iron and trace elements in the soil. Given their stability and high preservation potential, ferricretes can provide insights to ancient soil forming and weathering processes. In this study the key processes controlling ferricrete geochemistry in a Neogene strandplain are identified and interpreted in the context of a coastal acid sulphate weathering system. Textural and geochemical variations in sediment indurated by hematite and goethite represent a record of in situ induration, erosion, and reworking. This development took place within an environment of fluctuating pH and Eh and subaerial wetting and drying cycles. We distinguished depositional and post-depositional processes based on the results of whole rock geochemistry, hyperspectral mineralogy, and major and trace element maps of petrographic thin sections. The ferricretes have three morphological types: flat-lying indurations, concentric pisoliths, and rounded nodules with fragmented internal textures. Successive laminae of Fe-oxides and hydroxides in all morphological types of ferricrete have variable Fe, Al, and Si abundances, reflecting cyclic precipitation and groundwater chemistry changes. Episodic wetting and drying of near coastal sediments was superimposed on a long-term trend of marine regression and local tectonic uplift (from ~
Source:Geoderma, Volume 294
Author(s): S.M. McLennan, D. Giles, S.M. Hill