Huangnitang is a village in Zhejiang

Zhejiang

Zhejiang is an eastern coastal province of the People's Republic of China. The word Zhejiang was the old name of the Qiantang River, which passes through Hangzhou, the provincial capital...

 province, China

People's Republic of China

China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...

. It is the location of the Global Boundary Stratotype Section and Point

Global Boundary Stratotype Section and Point

A Global Boundary Stratotype Section and Point, abbreviated GSSP, is an internationally agreed upon stratigraphic section which serves as the reference section for a particular boundary on the geologic time scale. The effort to define GSSPs is conducted by the International Commission on...

 (GSSP), which marks the boundary between the Third and Darriwilian Stages of the Middle Ordovician

Ordovician

The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

. The GSSP was ratified by the International Union of Geological Sciences

International Union of Geological Sciences

The International Union of Geological Sciences is an international non-governmental organization devoted to international cooperation in the field of geology.-About:...

 in 1997. It was China's first.

The boundary is defined as the first appearance

First appearance datum

First appearance datum is a term used by geologists and paleontologists to designate the first appearance of a species in the geologic record. In other words, FADs represent the geologically oldest fossil of a particular species that has yet been discovered.FADs are frequently used to designate...

 of the graptolite

Graptolite

Graptolithina is a class in the animal phylum Hemichordata, the members of which are known as Graptolites. Graptolites are fossil colonial animals known chiefly from the Upper Cambrian through the Lower Carboniferous...

 Undulograptus austrodentatus. The graptolite Arienigraptus zhejiangensis appears 0.5 m below this boundary. The rock section is shale

Shale

Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...

.