Molecular fossils within bitumens and kerogens from the ~ 1 Ga Lakhanda Lagerstätte (Siberia, Russia) and their significance for understanding early eukaryote evolution

Abstract

The emergence and diversification of eukaryotes during the Proterozoic is one of the most fundamental evolutionary developments in Earth’s history. The ca. 1-billion-year-old Lakhanda Lagerstätte (Siberia, Russia) contains a wealth of eukaryotic body fossils and offers an important glimpse into their ecosystem. Seeking to complement the paleontological record of this remarkable lagerstätte, we here explored information encoded within sedimentary organic matter (total organic carbon = 0.01–1.27 wt.%). Major emphasis was placed on sedimentary hydrocarbons preserved within bitumens and kerogens, including molecular fossils (or organic biomarkers) that are specific to bacteria and eukaryotes (i.e. hopanes and regular steranes, respectively). Programmed pyrolysis and molecular organic geochemistry suggest that the organic matter in the analyzed samples is about peak oil window maturity and thus sufficiently well preserved for detailed molecular fossil studies that include hopanes and steranes. Together with petrographic evidence as well as compositional similarities of the bitumens and corresponding kerogens, the consistency of different independent maturity parameters establishes that sedimentary hydrocarbons are indigenous and syngenetic to the host rock. The possible presence of trace amounts of hopanes and absence of steranes in samples that are sufficiently well preserved to retain both types of compounds evidences an environment dominated by anaerobic bacteria with no or very little inputs by eukaryotes. In concert with the paleontological record of the Lakhanda Lagerstätte, our study adds to the view that eukaryotes were present but not significant in Mesoproterozoic ecosystems.

A new red alga preserved with possible reproductive bodies from the 518‐million‐year‐old Qingjiang biota

“…820 Ma) (Love & Zumberge, 2021). Their evolution is in accordance with the view that eukaryotes were present but not significant in Mesoproterozoic ecosystems, showing a protracted evolution based on a study of molecular fossils (Duda et al, 2021). Compared with other algae, their additional carposporophyte and tetrasporophyte phases are thought to be evolutionary innovations that explain the success of red algae (Yang et al, 2016).…”

Special issue: Going Deep—Tracking life processes through time and space

“…Jan-Peter Duda and co-workers investigated molecular fossils from the bitumen and kerogen fractions of the ~ 1 Ga Lakhanda Lagerstätte (Siberia, Russia), which contains a wealth of exquisitely preserved fossils of early eukaryotic organisms. They show that the environment was dominated by anaerobic bacteria with no or very little inputs by eukaryotes, supporting the view that eukaryotes were present but not significant in Mesoproterozoic ecosystems (Duda et al 2021).…”