The discovery of a shark tooth along a sandy shoreline often sparks curiosity. These intriguing finds are durable pieces of natural history. Sharks continuously shed their teeth throughout their lives, with some species losing thousands over a lifespan. These shed teeth, composed of a hard, mineral-rich outer layer called enameloid, become part of the marine environment.
The Journey to Becoming a Fossil
For a shed shark tooth to transform into a fossil, it must undergo a specific geological process over a long period. This transformation begins when a tooth sinks to the seafloor and is rapidly buried by sediments. Quick burial is important because it protects the tooth from weathering, abrasion, and decay. Over time, as more layers of sediment accumulate, pressure compacts the tooth within its surroundings.
This process, known as permineralization, involves groundwater seeping through the sediment and carrying dissolved minerals. These minerals infiltrate the porous structure of the tooth, filling its microscopic spaces. The original organic material of the tooth is gradually replaced or reinforced by these minerals, turning the tooth into a stone-like fossil. This slow process typically takes at least 10,000 years, and often millions of years, for a tooth to fully fossilize.
Common Ages of Beach-Found Teeth
Shark teeth commonly discovered on beaches are ancient fossils, not recent sheds from living sharks. They can be millions of years old, providing a tangible link to prehistoric marine ecosystems. Many originate from the Cenozoic Era (the last 66 million years), with a significant number dating back to the Miocene or Pliocene epochs. Some may be from the older Cretaceous period.
The specific age of a fossil shark tooth depends on the geological history of the discovery location. Coastal erosion and shifting sands can expose layers of sediment that were once ancient seabeds, bringing these fossilized teeth to the surface. While a tooth might be found today, it represents an organism that lived in oceans tens of millions of years ago. These teeth are durable enough to survive the forces of tides and currents, explaining their prevalence in beach environments.
Clues to a Tooth’s Age
While precise dating requires specialized geological analysis, several characteristics can hint at a fossil shark tooth’s age. The tooth’s color is a primary indicator, determined by the minerals present in the sediment where it fossilized. For instance, high concentrations of iron or phosphate may result in black or gray teeth. Sediments rich in calcium carbonate or organic material might exhibit shades of brown or tan.
Less common hues, such as blue or green, can result from trace minerals like copper during fossilization. The geographical location of the find is also a significant clue. Certain beaches or geological formations yield teeth from specific ancient periods due to their underlying rock layers. The degree of wear on a tooth, indicating how much it has been tumbled by natural forces, can also provide a sense of its age.