Fig. 2 | Scientific Reports

Fig. 2

From: Spongy-looking microfabrics in the earliest named stromatolite represent deep burial alteration and incipient metamorphism

Fig. 2

The secondary nature of spongy microfabrics; close-ups of central part of Fig. 1D. (A) Stromatolite layers (F, V, M) and alteration areas (AL) that locally contain relic structures of the host rock (asterisks) and show diffuse, interfingering to scalloped-cuspate margins (asterisks). (B–D) Altered areas (AL) show a variety of secondary spongy microfabrics (S1-S3) in function of the nature of the encountered host (granularity, initial spar component). Hypotype NYSM 19,458.1. (E) For comparison, cross-polarised light thin-section view of a spongin network of a modern non-spiculate (keratosan) sponge with its distinctive canal system (Ca), spongin is birefringent. For B–E, scale bar = 1 mm.

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