CHENGJIANG

The Chengjiang fauna is one of the most exciting testimonies of the past and has an eminent importance than cannot be overemphasized. The Chengjiang lagerstatte is one of the oldest and and includes the perhaps best preserved Paleozoic biota with a wealth of different taxa that was never expected for the Early Cambrian - certainly the most spectacular paleontologic discovery since the Burgess Shale of British Columbia and one of the most important fossil archives known so far.
.
.
.
.
The Chengjiang fossil lagerstätte:
Major outcrop in the Qiongzhusi Formation
near Chengjiang, Yunnan Province

Copyright (c) 1997 by E. Landing

.

Stratigraphy and preservation

The Chengjiang fauna was accidentally discovered in 1984 at Maotianshan (meaning "Maotian hill") near Chengjiang, the Yunnan Province, South China. The strata with the soft-bodied fauna belongs to the long-known Qiongzhusi Formation (earlier typed "Chiungchussu") of the Qiongzhusi Stage of the late Early Cambrian. It should be emphasized, however, that the late Early Cambrian of recent stratigraphic concepts includes more-or-less the whole macrofossil-bearing Early Cambrian, which represented the entire Early Cambrian of the pre-mid 1960s so that the strata predate a notable part of the Early Cambrian. The Chengjiang soft-bodied biota occurs only about 25 m above the earliest trilobites (genus Parabadiella) found in this area and on the Yangtze Platform (which are most probably coeval to late Atdabanian trilobites of the Siberian Platform).
The sediments of the Chengjiang strata consist of finely laminated mudstones, which are deposits of an outer shelf detrital belt and formed in quiet water environments. The frequency of macrobenthos suggests that the water was relatively well oxygenated, although bioturbation is sparse so that possibly only the uppermost layer at the sediment surface was oxygenated. The preservation of non-mineralized organismal parts probably resulted from repeated rapid burial events thst prevented the bodies from destruction by currents, bioturbation and other biotic activities such as by scavengers abd carnivores. Burial is also made responsible for absence of sulphate reduction which apparently was low so that the soft-parts were preserved in a number of different layers in the formation.Well developed anoxic conditions are reflected by several layers with carbon-rich deposits in the Qiongzhusi Formation. These conditions probably led to frequent mass mortalities which may have played a significant role in the soft-part preservation.
.

Biota

The perhaps most surprising aspect of the Chengjiang biota is the wealth of taxa from so many different groups. The fossil assemblages includes diverse algae, medusiform metazoans, chondrophorines, sponges, chancelloriids, sea anemones, priapulid worms, hyoliths, possible ectoprocts, inarticulate brachiopods, annelid-like animals, lobopodians, trilobites and non-trilobitic arthropods, hemichordates and probable earliest chordates as well as taxa that cannot definitely be assigned to any well established groups. The meaning of the Chengjiang fossils is not only by their pure occurrence or early appearance in the fossil record (which make the Cambrian Explosion even more dramatic), but also by their fine preservation which offers the opportunity to learn more about the morphology of these early creatures. One of the most outstanding examples might by Microdictyon, the isolated sclerites of which were known from numerous localities on various continents, but none of the specialists had any idea how this creature could have been organized. The discovery of these net-like scales of Microdictyon on a worm-like animal certainly was a night-mare experience for many students of this group. This learning process also includes details of hard-part animals such the trilobites as can be seen on the photo of Eoredlichia intermedia below.
.
Misszhouia longicaudata, a soft-bodied trilobite.
Specimen with largely exfoliated thorax exposing preserved appendages.
Qiongzhusi Formation, Chengjiang, Yunnan Province.

Copyright (c) 1997 by G. Geyer
Eoredlichia intermedia with preserved antennae
and mid-gut diverticula (dark blobs in the anterior part of the rhachis.
Qiongzhusi Formation, Chengjiang, Yunnan Province.

Copyright (c) 1997 by G. Geyer
.
Although the present state research is far from having reached a level, much progress has be made in the recent years, and the list of known taxa now includes:
.
Algae
Porifera
Chancelloriida
Cnidaria
Ctenophora
Priapulida
Palaeoscolecida
Lobopodia
?Ectoprocta
Phoronida
Brachiopoda
Hyolitha
?Annelida
Arthropoda
Hemichordata
Chordata
uncertain affinity
.
.
.
.
.
Cover of the most comprehensive on the Chengjiang fossil lagerstätte:
The Chengjiang Biota. A Unique Window of the Cambrian Explosion
by J. Y. Chen, G. Q. Zhou, M. Y. Zhu and K. Y. Yeh, 1997.
ISBN 957-8503-47-4
You might also want to consult the Chengjiang page in the Hooper Virtual Natural History Museum.
. 
-HOME-