Here's why:

* Geological Time Scale: The Earth's history is divided into eons, eras, periods, and epochs. The Jurassic Period falls within the Mesozoic Era, which spanned from about 252 to 66 million years ago.

* Jurassic Period: The Jurassic Period, specifically, lasted from about 201 to 145 million years ago. This means that material dating back 180 million years would fall within this period.

It's important to note that the Earth's crust is incredibly complex, and the specific layers and their ages can vary significantly depending on location. But generally, material from that time period would be found within what geologists refer to as the Jurassic System.