Maotianshan slate

from Wikipedia, the free encyclopedia

The Maotianshan Shales (English Maotianshan Shales) are a geological group of layers from the lower Cambrian of Yunnan , People's Republic of China . Name imparting type locality is the hill of Maotianshan ( Chinese  帽天山 , Pinyin Maotianshan ), located in the district of Chengjiang of the prefecture-level city Yuxi in Kunming . These are slate clays of the Yuanshan member from the Upper Heilinpu Formation (former Qiongzhusi Formation), the age of which was determined to be 525-520 Ma BP (2nd series of the Cambrian and middle Lower Cambrian). They are therefore around 10 million years older than the Burgess slates of Canada. The Maotianshan slates have achieved fame for the conservation deposits they contain , which were discovered by chance in 1984; the latter contains a fossil-preserved community that is extremely diversified and is commonly referred to as the Chengjiang Faunal Community . The Maotianshan slate is one of the 40 Cambrian fossil sites worldwide, which are characterized by the exquisite state of preservation of the mostly rarely fossilized body tissue and which can be compared with the finds from the Burgess slates.

Stratigraphy and facies

The conservation deposit is embedded in 50 meters thick, fine-layered shale clays of the Yuanshan member ( Eoredlichia trilobite zone). This stratification is long-lasting, it covers thousands of square kilometers in eastern Yunnan ( Yangtze craton ) and has brought fossils to light in numerous outcrops. Facial investigations suggest that the shale clays are of shallow marine origin and were deposited as fine-grain sediment turbidity in a tropical sea on the shelf edge. In addition, sea level fluctuations and tectonic processes can be read. Fossil preserved was mainly benthos , which was periodically covered by turbid currents - so most organisms no longer show any rearrangement after their death. Several carbon-rich horizons document anoxic conditions that probably triggered multiple mass extinctions and also contributed to the preservation of soft tissues.

Fossil content

Vetulicolids (a group with an unknown and puzzling position in the animal kingdom) from the Maotianshan slate

The biodiversity of the fossils contained in the Maotianshan schist, predominantly in soft-body conservation, is astonishing. These include algae , jellyfish-shaped metazoa , sponges , priapulids , annelid-like worms , echinoderms , Arthropoda (with the first trilobites ), Hemichordata , Chordata and first Agnatha . Numerous problematic animal species have also been discovered, which are likely to represent developmental sidelines that have not been pursued further.

literature

  • Xian-Guang Hou, Richard J. Aldridge, Jan Bengstrom, David J. Siveter, Xiang-Hong Feng: The Cambrian Fossils of Chengjiang, China. The Flowering of Early Animal Life. Blackwell Science, Malden MA et al. 2004, ISBN 1-4051-0673-5 .

Web links