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Abstract. Mineral specific surface area (SSA) increases as primaryminerals weather and restructure into secondary phyllosilicate, oxide, andoxyhydroxide minerals. SSA is a measurable property that captures cumulativeeffects of many physical and chemical weathering processes in a singlemeasurement and has meaningful implications for many soil processes,including water-holding capacity and nutrient availability. Here we reportour measurements of SSA and mineralogy of two 21 m deep SSA profiles attwo landscape positions, in which the emergence of a very small mass percent(<0.1 %) of secondary oxide generated 36 %–81 % of the total SSAin both drill cores. The SSA transition occurred near 3 m at bothlocations and did not coincide with the boundary of soil to weathered rock. The3 m boundary in each weathering profile coincides with the depth extentof secondary iron oxide minerals and secondary phyllosilicates. Althoughelemental depletions in both profiles extend to 7 and 10 m depth, themineralogical changes did not result in SSA increase until 3 m depth. Theemergence of secondary oxide minerals at 3 m suggests that this boundary may bethe depth extent of oxidation weathering reactions. Our results suggest thatoxidation weathering reactions may be the primary limitation in thecoevolution of both secondary silicate and secondary oxide minerals. Wevalue element depletion profiles to understand weathering, but our findingof nested weathering fronts driven by different chemical processes (e.g.,oxidation to 3 m and acid dissolution to 10 m) warrants the recognition thatelement depletion profiles are not able to identify the full set ofprocesses that occur in weathering profiles.