Reestablishment of an early life shallow marine ecosystem in the Neoproterozoic Gardnos meteorite impact crater (Norway)

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.