Stratigraphical setting of the Silurian thelodonts from Prince of Wales Island, Northwest Territories J A M E S D I X O N , R I D G E L E Y W I L L I A M S , A N D S U S A N T U R N E R

Dixon, J. , Williams, S. R., & Turner, Susan: Stratigraphical setting of the Silurian thelodonts from Prince of Wales Island, Northwest Territories. Lethaia. Vol. 5, pp. 281-282. Oslo, July 15th, 1972.

Additional and corrected information is given regarding the stratigraphy and palaeoecology of the thelodont-bearing sequence on Prince of Wales Island. The thelodont fauna is not older than latest Wenlockian.

James Dixon, Departntent of Geology, University of Ottawa, Ottawa KIN 6N5, Ontario, Canada ; S. R. Williants, NJtional Museum of Canada, Ottawa, Ontario, Canadn ; Susan Turner, Hancock Museum, Newcastle-upon- Tyne, NE2 4PT, England; Novenrher 16th, 1971.

Attention is drawn to the existence of errors in the paper by Turner & Dixon (1 97 1) that should be rectified promptly to prevent confusion and misuse in subsequent stratigraphic work. The extended British postal strike in early 1971 prevented communication between the authors and publishers at the crucial stage of examining the proof copy and hence certain errors were not corrected before the paper reached final copy stage. The corrections which follow include suggestions from S. R. Williams, who is working on the Read Bay Formation and the underlying ‘transition beds’.

The name ‘Transition Beds’, used throughout the paper, incorrectly sug- gests formal recognition of the name as a new lithostratigraphic unit. The intended informal designation is ‘transition beds’ referring to the gradational sequence of rocks between the Allen Bay and Read Bay Formations.

In the opening paragraph (op. cit. : 385) the new fossil locality was stated to be ‘. . . an unnamed stream which flows eastward into Young Bay’. This should read ‘. . . an unnamed stream which flows eastward in Peel Sound’.

Figure 2 (op. cit.:387) represented a generalised section of the strata concerned and suggested that the contact between the Read Bay Formation and underlying rocks is an unconformity. Related to this mistake is a sen- tence in the initial paragraph of the stratigraphy section (op. cit. : 387) which read ‘At the time of Christie’s study there was no indication of missing strata between these fossiliferous horizons (i.e. the underlying Allen Bay Formation containing a Middle or Upper Ordovician fauna) and the Read Bay Formation . . .’. Indeed there still is no indication of missing strata;

282 James Dixon, Ridgeley Williams, and Susan Turner

the field evidence indicates a continuous sequence from the Allen Bay Formation into the Read Bay Formation with no evidence of unconformable relationships.

On page 390 (op. cit.) the personal communication from S. R. Williams should read ‘. . . the interbedded limestones contain a fauna of gastropods, brachiopods and ostracodes suggesting a subtidal-intertidal environment.’

Concerning the age of the ‘transition beds’, S. R. Williams indicates that ‘despite the presence of cephalopods and stromatoporoids which elsewhere in North America occur in strata of Llandoverian and Wenlockian age, the invertebrate assemblages of the overlying Read Bay Formation are clearly of Ludlovian or Pridolian age.

Invertebrates collected from the upper 20 m of the “transition beds” include Leperditia spp., Protathyris sp., ?Hormotoma sp. and Eurypterus remipes tetragonophthalmus Fischer. The latter is a characteristic member of the “Eurypterus jischeri” assemblage of Cornwallis Island that is asso- ciated with Monograptus testis (Barrande) and Cyrtograptus trilleri Eisel (Copeland 1971 : 20). A latest Wenlockian or earliest Ludlovian age is thus indicated.

There is therefore no reason to suggest that the upper “transition beds” near Savage Point, Prince of Wales Island are any older than latest Wen- lockian’.

R E F E R E N C E S

Copeland, M. J. 1971 : Additional Silurian Arthropoda from Arctic and eastern Canada.

Turner, Susan, 81 Dixon, J . 1971 : Lower Silurian thelodonts from Prince of Wales Island, Bull. Geol. Sum. Canada 200: 11, 19-26.

Northwest Territories. Lethain 4 , 385-392.