Decay and preservation in marine basins: A guide to small multi-element skeletons

Abstract

This research explores how decay works and how different variables can affect this process in marine environments. The results are based on asterozoan echinoderms to cover one of the most complex multi-element skeletons in nature. Long-term experiments evaluated the effects of light, energy, salinity, sediment, oxygenation, temperature, and scavenger activity. The results showed that seven major agents can accelerate decay, including algal growth, water energy, microbial activity, microscavengers, macroscavengers, bubble production, and water acidification. Rapid burial of living organisms is the main shortcut to the fossilization of articulated specimens, but burial days to weeks after death can still lead to preservation if exceptional conditions delay the decay agents. Abrupt changes in salinity and temperature can restrict the distribution of scavengers and microorganisms, helping to preserve carcasses in the long term. Deeper or turbid seafloors can prevent small skeletons from destabilising due to the rapid growth of filamentous algae. Stagnant waters can also protect carcasses from waves and bottom currents, while water stratification can attenuate the attack of microscavengers. Although anoxia favours the preservation of soft parts, it is unable to prevent the anaerobic attack of microscavengers, which accelerates the destruction of small hard parts. Microbial reduction in anoxic regions can also drive the production of bubbles and the acidification of the water column, accelerating the destruction and dissolution of carbonate elements. These insights review important taphonomic concepts and provide a useful guide for interpreting the preservation potential of delicate organisms throughout the geological record.