Graptolites

[Jdeutsch]

I'm having a bit of trouble recognizing graptolites-I am never sure if I am seeing mineral streaks or pseudofossils etc

I've never saved any (on purpose- I suppose I have several in boxes)-

Would appreciate any comments regarding graptolites-best geologic formations to consider, potentially productive regions where a neophyte might clearly see them in situ, and please post your images-

[Caleb]

Graptoplites in the Ordovician of Southeast MN and NE Iowa are most prolific in the Maquoketa Formation. However, they are preserved that the only way they can be recognized is on a fresh break. After they're exposed, the black carbon film is very quickly washed away leaving very little evidence. They can be found throughout the other Ordovician formations of Minnesota, Wisconsin and Iowa, but again are best seen on fresh breaks. The most common are the Diplograptus which look like little sticks, usually not much more than an inch long. There is another fern like one that can be found in the Maquoketa called Desmograptus, but it's much less common.

Diplograptus peosta- the black lines in the rock are all graptoloites

Maquoketa Formation

Late Ordovician (Richmondian)

Southeast Minnesota

Desmograptus cancellatus

Maquoketa Formation

Late Ordovician (Richmondian)

Southeast Minnesota

[Herb]

Here's one from the U.Ordovician of Cincinnati, OH. Probably Climacograptus sp.

[Jdeutsch]

The images here are from some late Ord/early Silurian limestone- Niagra escarpment near Wisconsin/Michigan border in Green Bay- each streak is about 1 cm

I see these streaks and assume I am looking at shells that were cut through but they bear a resemblance to pictures I see of Graptolites. In fact, of the pictures I've seen, every weird streak in a rock resembles some picture I've seen - Does a 10x lens help?

Edited August 2, 2012 by Jdeutsch