Guzhangian

The Guzhangian is an important time period in Earth's history, belonging to the uppermost part of the Miaolingian Series during the Cambrian era. It comes after the Drumian Stage and before the Paibian Stage, which are both part of the Furongian Series. This stage helps scientists understand how life on our planet developed millions of years ago.

The Guzhangian Stage began around 500.5 million years ago, marked by the first appearance of a special kind of trilobite called Lejopyge laevigata. Trilobites were sea creatures with hard shells, and they are very important for studying this time in history. The end of the Guzhangian, around 497 million years ago, is identified by the appearance of another trilobite, Glyptagnostus reticulatus.

The name Guzhangian comes from Guzhang County in Hunan Province, China, where these important fossils were first discovered. Studying the Guzhangian helps scientists learn about the changes in life and the environment during this exciting period of Earth's past.

GSSP

The Global Boundary Stratotype Section and Point (GSSP) for the Guzhangian stage is in the Huaqiao Formation in Hunan. It is marked by a special limestone layer. This layer is 121.3 meters above the start of the formation at the Louyixi section. The layer is important because it has the first appearance of the trilobite Lejopyge laevigata.

Paleogeography

During the Guzhangian time period, the Earth was a little closer to the Moon. Scientists think the distance was about 370,180 kilometers. At that time, a full day on Earth was shorter than today. It lasted around 21.58 hours, not the 24 hours we have now.

Major events

During the Guzhangian time, many new animals appeared and spread. Later, many animals disappeared over a long period of about 3 million years. This loss happened in two steps: first a small drop, then a bigger one. After this, the number of animal types returned to what it was before.

From the Guzhangian to the Jiangshanian, the oceans slowly lost oxygen. This made life hard for animals on the ocean floor. This change, along with an event called the SPICE, probably helped cause the loss of many animals.