294 SMITHSONIAN AIISCELLANEOUS COLLECTIONS VOL. 75 



Feet Meters 



ir. Hard gray limestone, with irregular streaks of buff- 

 weathering magnesian limestone. Varies in thickness 



from 9 to 12 inches (22.9 to 30.5 cm.) i .3 



IS. Thin-bedded, bluish-gray limestone intcrbedded in dark 



argillaceous shale 13 3-9 



Fauna. — (2it) : a 3 to 5 inch (7.6 to 12.7 cm.) layer, 6 feet 

 (1.8 m.) from the base, yielded a few fossils, with 

 fragments of rather large trilobites. 

 Idahoia sp. 

 At 8 feet (2.4 m.) above the base of is a few 

 fragments of fossils were collected from a layer of 

 gray limestone (2iu). 



Thickness of Sabine formation 415 — 126.5 



Beneath the Sabine, thick-bedded, buff and gray 

 magnesian limestones of the Lyell formation extend 

 down in the section as at Cotton Grass Cirque, i mile 

 (1.6 km.) to the north. These beds dip 40° west with 

 a strike of north 15° west. 



Algal Growth 



A few of the layers of the upper part of the Sabine hmestone 

 (see p. 22y) carry a large and varied series of columnar-like, suppos- 

 edly algal growths, similar in outward form to objects in the pre-Cam- 

 brian Siyeh limestone of Glacier National Park referred to the genus 

 Coll cilia. ^ They are clearly exposed in and on several layers of a 

 cream- to Iniff-colored, fine-grained magnesian limestone, 280 to 300 

 feet (85.3 to 91.4 m.) below the summit of the formation. The layers 

 carrying the Collcnia ? below Cotton Grass and Tilted Mountain Cir- 

 ques slope to the west-southwest at an angle of about 45°. They are 

 slightly more resistant to erosion than those above them, with the re- 

 sult that along an outcrop of 1,000 feet (304.8 m.) or more, the upper 

 surface of one or more of the layers is exposed to a height of from 

 10 to 30 feet (3.05 to 9.2 m.). These are well shown by the photo- 

 graphs reproduced on plates 56, 57. The columns in thei highest layers 

 in which they occur are larger and longer than in the layer immediately 

 beneath. They vary from 8 to 14 inches (20.3 to 35.6 cm.) in diameter 

 at the upper end, and from 4 to 8 inches (10.2 to 20.3 cm.) in the 

 layer beneath. The latter is underlain by a thick layer of compact, 

 hard, fine-grained magnesian limestone in which no traces of the 

 columnar forms or algal deposits were seen, but in the next subjacent 

 layer, large and very irregular columnar forms occur. 



^ Bull. Geol. Soc. Amer., Vol. 17, 1906, pi. n ; Smithsonian Misc. Coll., Vol. 64, 

 No. 2, 1914, pi. ID, fig. 3. 



