Guzhangium
| system | series | step | ≈ age ( mya ) |
|---|---|---|---|
| higher | higher | higher | younger |
| Cambrian | Furongium | 10th stage | 485.4 ⬍ 489.5 |
| Jiangshanium | 489.5 ⬍ 494 |
||
| Paibium | 494 ⬍ 497 |
||
| Miaolingium | Guzhangium | 497 ⬍ 500.5 |
|
| Drumium | 500.5 ⬍ 504.5 |
||
| Wuliuum | 504.5 ⬍ 509 |
||
| 2nd series | 4th stage | 509 ⬍ 514 |
|
| 3rd stage | 514 ⬍ 521 |
||
| Terreneuvium | 2nd stage | 521 ⬍ 529 |
|
| Fortunium | 529 ⬍ 541 |
||
| deeper | |||
The Guzhangium is the upper chronostratigraphic stage of the Miaolingian , the third chronostratigraphic series of the Cambrian . The guzhangium follows the drumium and precedes the paibium . The Guzhangian lasted from 500.5 to 497 million years ago (interpolated).
Naming and history
The name of the stage was ratified in March 2008. It is named after Guzhang County ( Hunan Province , China).
Definition and GSSP
The lower limit is 121.3 meters above the base of the Huaqiao Formation in a horizon that marks the first appearance of the globally occurring trilobite species Lejopyge laevigata . Secondary markers near the base of the step are the appearance of Lejopyge calva or Lejopyge armata slightly below the base of the step, the appearance of conodonts associated with the base of the Laiwugnathus laiwuensis zone, and the transgression phase of a small eustatic event.
The upper limit (and thus the lower limit of the Paibium ) is defined by the first appearance of the trilobite species Ptychagnostus atavus . The GSSP (Global Standard-stratotype Section and Points) is a profile 4 km northwest of Luoyixi along the Youshui River at the Fengtan Reservoir, approximately 4 km southeast of Wangcun in Guzhang County (northwest Hunan Province , China ). The GSSP is on a road outcrop at 28 ° 43.20 'N and 109º57.88' E.
Correlation with other regions
The fauna changes at the base of the Guzhangium stage can also be found at the base of the Boomerangium stage in Australia, at the base of the Aldanaspis zone (polymeric trilobites) in Siberia and at the base of the Paradoxides forchhammeri zone on the western Avalonia lesser continent become. The horizon with the first appearance of Lejopyge laevigata is very close to a peak of a long period with negative δ 13C deviations of up to 0.58 ‰.
Individual evidence
literature
- Felix Gradstein, Jim Ogg and Alan Smith: A Geologic timescale. Cambridge University Press 2004. ISBN 978-0-52178-673-7
- Shanchi Peng, Loren E. Babcock, Jingxun Zuo, Huanling Lin, Xuejian Zhu, Xianfeng Yang, Richard A. Robison, Yuping Qi, Gabriella Bagnoli and Yong'an Chen: The Global Boundary Stratotype Section and Point (GSSP) of the Guzhangian Stage (Cambrian) in the Wuling Mountains, Northwestern Hunan, China. Episodes, 32 (1): 41-55, Beijing 2009 PDF