Southeastern Alaska. 513 



lying limestone are well shown on Kosciusko Island. The 

 strata as a whole in this region are badly disturbed and, 

 as is the case throughout southeastern Alaska, contacts 

 are very poorly shown, being as a rule indicated by an 

 indentation of the shore line and a depression running 

 back into the timber. At present, therefore, although 

 the relative positions of stratigraphic units are obvious, 

 the character of the unconformity and the nature of the 

 passage beds are only partly known. 



The limestone series overlying the conglomerate car- 

 ries a rich Conchidium fauna. In certain thin beds the 

 rock is almost wholly made up of the brachiopods. This 

 fauna appears to be identical with that of the limestone 

 near Meade Point at the northern end of Kuiu Island. 

 At the base of the limestone at this locality is a bowlder 

 bed which I believe to be glacial in origin and to be cor- 

 related with the conglomerate of Heceta. The lime- 

 stones below the conglomerate likewise carry a rich fauna 

 consisting of pentameroids, corals, and gastropods. 

 The general aspect of both faunas seems to place them 

 as approximately late Niagaran in age. 



The conglomerate itself has a thickness of between 

 1000 and 1500 feet. It will probably be found to vary 

 considerably from place to place. In the main the con- 

 glomerate appears to consist of heterogeneous, unstrati- 

 fied or poorly stratified material. Rarely lenticular 

 bodies of cross-bedded sandstone occur in the mass. 

 These are clearly water-laid and indicate current action. 



The bowlders in the tillite range in size up to 2 or 3 feet 

 in length, as seen. They consist of greenstone, gray- 

 wacke, limestone, and various types of igneous rocks; 

 limestone bowlders are scarce. All the bowlders are 

 smoothed and rounded. Facetted bowlders are numer- 

 ous, and given the proper type of rock, characteristic 

 glacial scratches are common. The scratches show best 

 on the fine-grained, dense greenstones. Limestone bowl- 

 ders and certain types of igneous rocks do not show them 

 at all. * The shore line is strewn with these pebbles and 

 bowlders which were undoubtedly derived from the con- 

 glomerate as they are not to be found on the adjacent 

 limestone shores. All the material collected was taken 

 from the conglomerate itself. This is well broken down 

 by weathering: in some places, and the pebbles may be 

 picked out with the fingers or tapped out with the ham- 



Am. Jour. Sci.— Fourth Series, Vol. XLVI, No. 273.— September, 1918. 

 20 



