When dinosaur fossils emerge at a site, determining how many millions of years ago their bones were interred can be challenging. Though the various layers of sedimentary rock encapsulate periods of geological history, accurately dating these layers or the fossils within them has often been a source of frustration.
Fossilized bones and teeth have previously been dated with limited success, as their reliability varies depending on the specimen. The processes of fossilization and sediment turning into rock can alter the bones in ways that disrupt accurate dating. While uranium-lead dating is among the most relied-upon methods for dating materials, using it for direct fossil dating is still a burgeoning technique.
A breakthrough may lie in dinosaur eggshells, which could offer a new way to date the surrounding rocks and fossils. Spearheaded by paleontologist Ryan Tucker from Stellenbosch University, a group of researchers has crafted a new method to date eggshells, revealing how long ago they were buried under what was once sand, mud, or other sediments. This information can then be applied to determine the burial time of any other fossils found in the same rock layer.
âIf validated, this approach could greatly expand the range of continental sedimentary successions amenable to radioisotopic dating,â Tucker mentioned in a study recently published in Nature Communications Earth & Environment.
This goes way back
Vertebrates have been laying calcified eggs for hundreds of millions of years, although the earliest dinosaur eggs had soft shells. The unique microstructure of calcium carbonate present in fossilized eggshells makes them valuable for determining the age of other fossils. The crystals in them capture a record of diagenetic changesâphysical and chemical transformations that occur during fossilizationâincluding water damage and fissures caused by compression between sediment layers. This unique microstructure facilitates the screening for these signs when dating the eggshells.