Guzhangian

The Guzhangium is in the Earth's upper stratigraphic level of the third, yet unnamed series or the total seventh stage of the Cambrian. The Guzhangium is under and overlaid by Drumium from Paibium. The Guzhangium lasted from about 500.5 million years to 497 million years ago (interpolated).

Nomenclature and history

The name of the stage was ratified in March 2008. She is on a circle Guzhang ( Prov. Hunan, China) named.

Definition and GSSP

The lower limit is 121.3 meters above the base of Huaqiao Formation in a horizon that marks the first appearance of the trilobite species occurring worldwide Lejopyge laevigata. Secondary marker near the base of the step are the occurrence of Lejopyge calva or Lejopyge armata slightly below the base of the step, the occurrence of Conodonten associated with the base of the zone and the Laiwugnathus laiwuensis Transgressionsphase a small eustatic events.

The upper limit (and therefore the lower limit of the Paibiums ) is defined by the first appearance of trilobites atavus Type Ptychagnostus. The GSSP (Global standard stratotype Section and Points ) is a profile 4 km north-west along the Luoyixi Youshui River at Fengtan reservoir, about 4 km south-east of Wangcun in a circle Guzhang ( northwestern Hunan Province, China ). The GSSP is located on a road digestion at 28 ° 43.20 'N and 109 ° 57.88 ' E.

Correlation with other regions

The faunal at the base of Guzhangium level can be detected on the western Avalonia small continent at the base of the Boomerangium stage in Australia, at the base of Aldanaspis zone ( polymeride trilobites ) in Siberia and at the base of Paradoxides forchhammeri zone be. The horizon with the first appearances of Lejopyge laevigata is very close to a peak of a long period with negative δ 13C variations of up to 0:58 ‰.