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. 2013 Dec 1;13(12):1103–1124. doi: 10.1089/ast.2013.1030

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Copyright 2013, Mary Ann Liebert, Inc.

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FIG. 14. — Polygonal oscillation cracks on sedimentary surfaces viewed from above, fossil and modern examples. (A) This polygon is defined by its slightly elevated margin. The close-up view allows recognition of a fossil gas escape hole in its center; Dresser Formation, Pilbara, Western Australia. Scale: 3 cm. (B) For comparison to (A), this image shows a very similar structure representing an ancient gas escape hole; 2.9 Ga Pongola Supergroup, South Africa. Scale: 5 cm. (C) A single polygon of a microbial mat from the sabkha El Bibane, Tunisia (modern). Note the circularly wrinkled folds within the microbial mat polygon, especially close to the tip of the pen. (D) A single polygon from the Dresser Formation, Pilbara, Western Australia. Note the presence of very similar circularly wrinkled folds. Scale: 4 cm. Compare Fig. 1C for further modern examples and Fig. 15 for statistical measurements.