Introduction to the golden nail: About the 19th century, when the eastern and western railway arteries of the United States were connected, in order to commemorate this event, a gold railway spike, referred to as "GSSP", was driven into the connection. The abbreviation of the Global Boundary Stratotype Profile Point is also "GSSP", so it is commonly known as the "Golden Nail" profile. The "golden nail" in Huangnitang is a global standard stratigraphic section about 460 million years ago. The geological age is in the middle Ordovician period. In layman's terms, the "golden nail" is a ruler, and the ruler here is not Like the ruler we usually use to measure clothes and length, the ruler here is a ruler for measuring geological time. That is to say, in order to judge the strata of all ages in the world, we must use our Changshan Huangnitang "golden nail" The section is used as a ruler for comparison and as a standard to infer and analyze the geological age of other places, so it is a global standard stratigraphic section.