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 found in the Huaqiao Formation in Hunan. It is marked by a specific limestone layer, located 121.3 meters above the start of the formation at the Louyixi section. This layer is notable because it contains the first appearance of the trilobite Lejopyge laevigata.

Paleogeography

During the Guzhangian time period, scientists believe the distance between the Earth and the Moon was about 370,180 kilometers, which is a bit closer than today. Back then, a full day on Earth lasted around 21.58 hours, shorter than our 24-hour days now.

Major events

During the Guzhangian time, many types of animals appeared and spread. Later, a big loss of species happened, lasting about 3 million years, which reduced the number of different species by about 45%. This loss happened in two steps, first a small drop and then a bigger one. After this loss, the number of species went back to what it was before.

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