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Details of the same annular layer (AL) in reflected light (a) and SEM (b) to show that the bands observed under reflected light (a) are neither regular, nor regularly distributed, are not visible with SEM (b). c–e Details of various fragments of b (c corresponds to the top of (b) and that supposed “depressions” in the surface of the AL are not visible in SEM, thus that they are optical artefacts
