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Comparative soft-tissue preservation in Holocene-age capelin concretions
Angel Mojarro1, Xingqian Cui1, Xiaowen Zhang1
1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
Geobiology
|November 8, 2021
Summary
Soft tissue preservation in carbonate concretions is a race between mineral precipitation and decay. Exceptional fossilization depends on organic matter, decay rate, and carbonate saturation, not specific decay communities.
Area of Science:
- Geochemistry
- Paleontology
- Biogeochemistry
Background:
- Soft tissue preservation through geologic time is challenging due to rapid decay post-senescence.
- Carbonate concretions offer unique insights into diagenetic processes and fossilization.
- Biologically induced mineral precipitation within concretions often preserves organic signals.
Purpose of the Study:
- Investigate soft tissue preservation mechanisms within Holocene carbonate concretions.
- Compare lipid biomarker signatures in concretions from contrasting depositional environments.
- Analyze factors influencing exceptional preservation of capelin (Mallotus villosus) remains.
Main Methods:
- Comparative lipid biomarker analysis of capelin-bearing carbonate concretions.
- Study sites: Kangerlussuaq, Greenland (marine, exceptional preservation) and Greens Creek, Canada (paleo-freshwater, skeletal remains).
- Statistical analysis of lipid distributions and environmental signals.
Main Results:
- Kangerlussuaq concretions show endogenous capelin tissues and productive water signals.
- Greens Creek concretions lack significant capelin and environmental lipid biomarkers.
- Bacterial fatty acid distributions suggest preservation is independent of specific decay communities.
Conclusions:
- Soft tissue preservation in concretions is a competition between microbially induced precipitation and organic decay.
- Exceptional preservation is linked to organic matter input, decay rate, carbonate saturation, and precipitation rate.
- Cementing pore spaces limit diffusion, arresting decay and respiration, thus enhancing preservation.
