Chemosynthetic microbial communities formed wrinkle structures in ancient turbidites

Wrinkle structures are often interpreted to be formed by photosynthetic microbial mats. They are rare in Phanerozoic marine subtidal environments because animal activity typically destroys mats or biofilms before lithification. We report wrinkle structures in lower Toarcian (Lower Jurassic) turbidites from the Tagoudite Formation in Morocco. These wrinkles are consistent with those from shallower deposits; however, given their paleodepth (∼200 m), it is unlikely they were formed by photoautotrophic communities. Modern turbidites are known to host chemosynthetic communities, often with extensive microbial mat formation. We propose the Tagoudite Formation wrinkles were formed by chemosynthetic communities, and the sedimentological, geochemical, and hydrographical conditions of the turbidites excluded grazers, allowing wrinkle structure lithification. Wrinkle structures occur in Cambrian, Silurian, Devonian, and Jurassic turbidites, and we posit that chemosynthetic mats growing on turbidity deposits represent a previously dismissed, underappreciated, or unrecognized mode of preservation. The chemosynthetic mat−induced wrinkle paradigm has significant implications; this taphonomic window for wrinkle preservation in turbidites expands the range of environments where these microbially induced sedimentary structures form and the communities that made them. Wrinkles in turbidites also represent new possibilities for the study of chemosynthetic ecosystems in deep time.