-22- 



below the base of the La Salle Limestone. The zone is 3/4 to 1 inch thick and 

 consists of olive gray to black shale having fine incipient planes of fissility 

 that are virtually invisible while the shale is moist but become apparent when 

 it is dry. The zone yields approximately one natural assemblage for every ten 

 pounds of shale when the shale is split along planes of fissility. A sharp 

 knife is the most effective instrument for splitting. Pieces of shale that 

 have slumped to creek level tend to be dry and thus split more easily than 

 fresh pieces. The zone of abundance is overlain and underlain by blocky black 

 shale. Dunbarella is common in a thin zone directly below the assemblage 

 collecting zone. The zone can be traced along the bank of Bailey Creek at least 

 as far as the haulage road bridge and probably much more widely. 



Amber and translucent fish scales, which occur in the black shales, may 

 glint like conodonts and be mistaken for them when examined without magnifica- 

 tion. Probably the most effective method of collecting is to accumulate a 

 pile of several pounds of shale and then carefully split the slabs with a 

 knife, examining each with a magnifying glass or hand lens. Microscopes are 

 available at the picnic shelter. 



