Reference Detail of

Report on Referred Fossils
Edit Reference Add/Edit Sample Sample List Show Map

Stratigraphic range: Jurassic-Early Cretaceous
Kinds of fossils: Plant-microfossils
Quadrangle or area: Christian, Alaska
Shipment No.: A-66-7D
Referred by: Brosge, William P.
Report prepared by: Scott, R. A.
Date: 05/01/1968

This partial report deals with material from one locality, your 66ATr 175; 67 deg. 38.7’ N, 144 deg. 47’ W. This locality is the same as 63ARr 58, reported as Triassic in my report A-63-8D.

The original age assignment of Triassic was based upon the recovery of only one type of fossil pollen, striate bisaccates, from the sample submitted as 63ARr 58. The determination was correct based upon the evidence at hand.

I did not know at that time a significant fact which has since developed from the study of a large number of Alaskan pollen samples: striate bisaccates are widespread as reworked contaminants in younger rocks. In most cases they are well preserved, so that they are not readily distinguishable from the indigenous pollen flora. Striate bisaccate pollen is durable, and may out-last the indigenous pollen under degradative conditions, which were the norm for the Alaskan material. This situation creates a misleading and unavoidable trap for the palynologist; I fell into it in the earlier report.

The sample from the same locality submitted as 66ATr 175 contains better preserved material. In addition to the reworked striate bisaccate pollen, other genera, such as Tauracosporites, Cicatricosporites, Tasmanites, and Tythodiscus, are present. The assemblage is that associated at numerous other localities with the “tasmanites” oil shale. Its age, though not yet accurately determined from palynomorphs, is in the Jurassic-Early Cretaceous range rather than Triassic as earlier reported.

User Note module to be added
66ATr 175 , Christian , Christian Quad.; 67 deg. 38.7'N., 144 deg. 47'W. Shale interbedded with graywacke that contains plant fragments and oil shale (Tasmanite) clasts. Same locality as 63ARr58 (A-63-8D, Triassic). N.B. Tasmanite does occur at several localities in the Christian quad.
Striate bisaccate pollen
Tauracosporites sp.
Cicatricosporites sp.
Tasmanites sp.
Tythodiscus sp.