NO. 5 PRE-DEVONIAN PALEOZOIC FORMATIONS 233 



caps Mt. Vaux and underlies Hanbury glacier at the head of Ice River valley. 

 The valley of the northeast fork of Ice river has been cut through this forma- 

 tion into the underlying Cambrian. It continues in Mt. Goodsir where it has 

 the greatest development, but is again cut off at the divide between Moose 

 Creek and Goodsir Creek valleys. On the east side of Moose creek this 

 formation is again exposed on Helmet mountain on the tops of the interstream 

 ridges and over the greater part of the ridge terminating in Striped mountain. 

 On account of the southward dip of the beds away from the igneous rock 

 of Ice river, the formation forms the top of Mt. MolHson and its southward 

 slope ; it continues northwest on the slope overlooking the Beaverf oot valley 

 until it pinches out in a synclinal fold on the south slope of Chancellor peak. 

 It presumably floors the upper part of Beaverfoot valley and is developed 

 on the east slopes of the Beaverfoot range. The area of this formation exposed 

 in the Beaverfoot range is bounded on the southeast by a fault, and towards 

 the north another fault defines the northeastern limit of the same area, the 

 fault passing between Leanchoil station and the ridge of Mt. Hunter. 



The greatest thickness is exposed in the south tower of Mt. Goodsir, but 

 even there the highest beds do not represent the top of the formation as 

 developed elsewhere outside of this district. Plate XI, B, shows the total 

 thickness of the Goodsir formation in Mt. Goodsir and also the underlying 

 Ottertail formation. An attempt was made to accurately measure the thickness 

 of these beds, but on account of the long talus slopes and the inaccessible cliffs, 

 especially in the upper 2,000 feet [609.6 m.], the attempt was unsuccessful. 

 Since at this locality the average dip of the beds is 20 degrees and the upper 

 and lower limits are observable, it was possible to estimate the thickness of the 

 formation in Mt. Goodsir and this was found to be 6,040 feet [1,840.9 m.] * 



Age and correlation. — This formation, as determined by faunal evidence, 

 belongs to the lower Ordovician. It is conformable with the Upper Cambrian 

 beds and on account of the lack of fossils in the upper part of the Ottertail 

 limestone, the lower limit of the Ordovician cannot be clearly defined. Fossil 

 horizons were found at four localities, but in each case near the base of the 

 formation. In Ice River valley fossils were found on the west side of the 

 amphitheatre at the head of the east fork ; also on the north side of Mollison 

 Creek valley about i mile [.8 km.] above its junction with Ice river. At 

 both of these localities, the fossil-bearing beds are in the same horizon and 

 consist of a greenish, calcareous and siliceous shale. The beds occur about 

 30 feet [9.1 m.] from the base of the formation as there developed. The other 

 two localities in which fossils were found occur in Moose Creek valley on the 

 northeast slope of Mt. Mollison, about 1,000 feet [304.8 m.] above the bottom 

 of the valley. The beds there consist of a dense, greenish, siliceous shale, 

 weathering light grey and buff, and occur within 300 feet [91.4 m.] of the base 

 of the formation. 



The fossils collected have been determined by Dr. Walcott. He found four 

 new species ; of these the trilobite Ceratopyge has not been described before 

 from this country. This genus has been described as occurring at the base 

 of the Ordovician in Sweden. The presence of this fauna in these beds is 

 the chief evidence for placing the beds of the Goodsir formation at the base of 

 the Ordovician.^ 



^ Loc. cit., pp. 94, 95. 

 " Loc. cit., p. 99. 



