Fig. 7 in Nanostructure of biogenic versus abiogenic calcium carbonate crystals

Fig. 7. Scleractinian Rennensismilia complanata (Goldfuss, 1826), Santonian (Upper Cretaceous), Lower Gosau beds, near Gosau, Austria; USNM 499247. Polished and etched (formic acid, 1%, 20s) septum with bundles of aragonite fibers enveloped by structures with positive etching relief interpreted by Sorauf (1999) as sheaths of proteinaceous matrix (A, C, same skeletal regions in different magnifications); in places skeletal etched fibers show regular discontinuities similar to that of extant zooxanthellates (B). AFM (contact mode; buffered pH = 8, ammonium persulfate 1%, 10 min.): height−2D projection (D, F), and deflection (E, G) images of 2×2 µm (D, E) and 500×500 nm (F, G) skeletal surface. Nanograins ca. 50–100 nm in diameter. Grayscale bars (left) show z−scale (height) of 2D projection images.