Sample Detail of
Sample: Sample No. 76AR24
Locality: Field No. 76AR24
Description: Elev. 5100 ft., 3.25 miles N. 76 E. from Mount Dall. Upper half of a conglomerate unit at least 4500 feet thick.
Location: Alaska Quadrangle: Talkeetna C-5
Township&Range: T29N R16W Section: Sec.24
Lat.: 62o35'22 " Long.: 152o11'40 "
Reference
Title: Report on Referred Fossils ,  1977 (02/18)
Report by: Sergius H. Mamay
Referred by: Bruce Reed
Age: Pennsylvanian (Middle Pennsylvanian)
Comment:Your collection of fossil plants from field locality 76AR24 in the Mt. Dall conglomerate is as you know, a poorly preserved, small assemblage in dominantly dark-grey siltstones. Only a few taxa are represented, but these are sufficiently well-enough recognizeable as to tag the enclosing rocks immediately as Middle Pennsylvanian, probably no lower than Alleghenian (my guess, on the basis of the limited flora in your collection, would be floral zone 10, of read and Mamay, 1964).

I should add that all the taxa named here are known to range into the Lower Permian. However, none of the characteristically Permian plants, such as Callipteris, is here, and the abundance of Cordaites in your collection is more harmonious with a Pennsylvanian age. On the other extreme, the cordaiteans, large-pinnuled odontopterids and abundant pecopterids are absent from the Mississippian. Thus I regard it as absolutely safe to call your material Alleghenian-or post-Alleghenian Pennsylvanian.

I am very excited about this all because of the extreme rarity of Pennsylvanian plants in Alaska. I realize (from Tom Dutro) that you have tough logistics to cope with, but if you can ever bring back more stuff from this locality I will jump at the chance for a first look!

I hope this gets to you in time to help your map. Meanwhile I will soon be in touch with you in regard to a joint article.

Occurrence(s)
No. Group Name Qty Notes
1 Plants Cordaites sp. abundant This apparently is the dominant element. Although poorly preserved, abundant leaves are present and are easily recognized by their closely-spaced, parallel veins.
2 Plants ?Calamites sp. So poorly preserved as to be doubtful, yet possible.
3 Plants Neuropteris cf. N. scheuchzeri 3 or 4 pinnules This large-pinnuled Neuropteris characterizes the upper part of the Pennsylvanian.
4 Plants Cyclopteris sp. a few A few of the orbicular basal pinnules that are referred to as Cyclopteris.
5 Plants samll, densely-spaced Pecopteris arborescens type
6 Plants Pecopteris sp. indeterminate
7 Plants Pecopteris unitus 1 one of the most easily recognized species because of its sparse, coarse veins. This is the most important specimen in your collection.