This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: In productive marine environments, a square meter (10.8 square feet) of seafloor can be perforated by hundreds to thousands of isolated and interconnected tunnels through which crawl and writhe a cornucopia of clams, shrimp, sea stars, sand dollars, snails, worms and other animals. All that excavation mixes up the sediment, along with any shells and other skeletal remains that happen to be there.
This temporal smearing is a problem for paleontologists because when that piece of seafloor is buried and becomes part of the fossil record, it's difficult and expensive to determine how much mixing took place. "What continually amazes me is just how much time a bunch of fossils collected from a single sediment layer can represent. In some cases, well-preserved fossil organisms that are found next to each other might have lived hundreds or thousands of years apart," said Rafal Nawrot, a paleontologist at the University of Vienna.
The work is published in the journal Proceedings of the National Academy of Sciences. The mixing of fossils that lived at different times but are preserved together is called time averaging. According to Daniele Scarponi, a colleague of Nawrot's and an associate professor at the University of Bologna, time averaging dictates the types of questions paleontologists can ask.
"Before interpreting a fossil assemblage, we need to know the interval it represents. Some fossil assemblages are like the ruins of Pompeii—buried rapidly and thus providing a snapshot of past communities frozen in time. Others are more akin to a prehistoric graveyard used continuously over centuries, in which human remains from different generations are slowly accumulating over time.
Both types can provide valuable insights into the past, but the kinds of data we can extract from them will be different in each case," Scarponi wrote. In addition to burrowing animals, several other factors influence time averaging, including: Through a project that was 20 years in the making, members of an international consortium of scientists say they have determined which of these factors is the most important for time averaging and thus primarily controls the temporal resolution of paleontological data. "Our results demonstrate that if we know how quickly sediment accumulates—which can be deduced from the environmental context—we can determine how much time is captured by a given fossil assemblage: The faster individual shells or bones are buried below the sediment surface, the less likely it is that remains from multiple generations of organisms will accumulate and be preserved together," Nawrot wrote.
Discover the latest in science, tech, and space with over 100,000 subscribers who rely on Phys.org for daily insights. d research that matter—daily or weekly. Sedimentation rates have long been anticipated to be an important component of time averaging, but gathering the data needed to rigorously and comprehensively assess this issue is difficult, time-consuming and very expensive. By integrating multiple projects, the authors analyzed more than 7,500 fossils, which were dated using radiocarbon and other methods and collected from a variety of oceanic environments around the world, from shallow coastal settings to the edges of continental shelves.
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