Cambrian Stage 3 is the still unnamed third stage of the Cambrian. It succeeds Cambrian Stage 2 and precedes Cambrian Stage 4, although neither its base nor top have been formally defined. The lower boundary is loosely defined as the first appearance of trilobites about 521 million years ago. The upper boundary and beginning of Cambrian Stage 4 is informally defined as the first appearance of the trilobite genera Olenellus or Redlichia around 514 million years ago.
Contents
Naming
The International Commission on Stratigraphy has not officially named the 3rd stage of the Cambrian. Sometimes this stage is referred to as "Atdabanian" which is used by geologists working in Siberia.
Biostratigraphy
The oldest trilobites known is Lemdadella which appears at the beginning of the Fallotaspis zone.