Trace fossils, microbially induced sedimentary structures (MISS), palynomorphs and particulate organic matter (POM) found in post-impact sediments in the Gardnos meteorite crater provide evidence of reestablishment of a Neoproterozoic ecosystem in a shallow marine, littoral environment, with sediments covered by microbial mats. Trace fossils are rare and restricted to horizontal burrows, including Gordia , Helminthopsis , Yichnia and poorly preserved tracks resembling Archaeonassa. MISS and water-escape structures are common and include characteristic features like Aristophycus. The recovered organic walled microfossils Trachysphaeridium laminaritum and Sphaerocongregus variabilis indicate a late Neoproterozoic age for the post-impact sediments. Particulate organic matter in deposits comprise dominantly dark grey to black, highly thermally altered amorphous kerogen and fragments of algal material (TAI ~ 4, temperature ˃ 250 °C). The trace fossils and MISS are typical of Neoproterozoic shallow marine mat-ground environments which existed prior to the development of Phanerozoic mixed-ground ecosystems. • Trace fossils and MISS found the upper post-impact deposits in the Gardnos meteorite crater are typical of Neoproterozoic mat-ground environments. • Acritarchs and cyanobacteria found in the post-impact deposits are typical of Neoproterozoic organic-walled microfossil assemblages. • Traces fossils in Gardnos crater point to an age prior to the evolution of ecosystems with more advanced infaunal organisms.
Smelror et al. (Wed,) studied this question.