Discovery of Paleodictyon in the Indian Ocean

Compared to the widespread occurrence of Paleodictyon in the geological record, in situ observations of this trace (herein termed ‘pattern’) in modern deep-sea sediments are still scarce, being confined to the Mid Atlantic Ridge, the South Atlantic, southwestern Pacific and the eastern equatorial Pacific Clarion-Clipperton Zone. Here, we report the discovery of Paleodictyon along the southern Central Indian Ridge and the Southeast Indian Ridge within the German license area for the exploration of marine massive sulfide deposits in the Indian Ocean. The patterns occur in sedimented areas, especially those closer to hydrothermal vents and sometimes in aggregation of up to forty, resulting in maximum densities of 9.7 patterns m−2. While many show the grid-like array of holes on the sediment surface that is typical of the modern examples of the genus, the pattern sometimes loses its regularity, in particular on thin veneers of patchy sediment overlying hard basalt substrate, a mode of occurrence reported here for the first time. Other examples appear to be in various stages of natural erosion, in some cases creating unusual linear features.