Limpet Shells from the Aterian Level 8 of El Harhoura 2 Cave (Témara, Morocco): Preservation State of Crossed-Foliated Layers
Fig 4
Microstructural organization of modern Patella vulgata calcite crossed-foliated outer layers.
a) PLM view (polarized and analyzed light) of a radial thin section. Outer surface is at bottom. b) PLM view (polarized light) showing the growth increments (green arrows) between two consecutive 1st order lamellae (I). c) PLM view (polarized and analyzed light) of three consecutive 1st order lamellae (I), displaying the preserved alternate orientation one lamella on two. 2nd order lamellae are visible (black arrows), as well as the individual, faintly disoriented 3rdorder rods (white arrow). d-g) Electron micropobe maps. d) Backscattered image of the scanned area, showing the alternate 1st order lamellae. e) Distribution of Mg content, layered following growth layers. f) Distribution of Sr content, displaying very faintly marked growth layers. g) Distribution of S content, faintly marking the crossed-foliated structure, strongly marking the growth layering. h-k) SEM images of a radial, unetched, freshly broken section. h) Several consecutive 1st order lamellae (I) (SEM). i) Limit between two 1st order lamellae (I), showing the change of orientation of its constituting 3rdorder rods (white arrow) or slats (FEG-SEM). j) 2nd order lamellae, composed of superimposed rows of 3rdorder units (SEM). k) Surface view of three consecutive 3rdorder slats within a second order row, separated by faint, punctuated limits (white arrows) and showing an inner texture (FEG-SEM). l-m) FEG-SEM images of a radial freshly broken section etched by OsO4 vapor, revealing organic membranes that separates each 3rdorder rod (white arrows). n-q) AFM scans. n) Phase image of the contact between two 1st order lamellae. Green arrows mark a growth increment. o-p) Height and phase images of 2nd order lamellae within a 1st order lamella. q) Phase image of several 2nd order lamellae, separated by a seemingly continuous membrane (blue arrow). Some ovoid sub-units (white arrow) can be seen, constituting the lamellae.