I08 PROCeSDINGS: GEOLOGICAIv SOCIETY 



The glacial conglomerate is under- and overlain by fossiliferous 

 marine limestones. The succession of beds is clearly shown and un- 

 mistakable. 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 imconformity and the nature of the 

 passage beds are poorly known. 



The limestone series overlying the conglomerate carries a rich Con- 

 ch id imn 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 Meade Point limestone of the Wrights and Kindle. The type 

 exposure of the latter is at the northern end of Kuiu Island. At the 

 base of the limestone at this locaUty is a boulder bed which I believe 

 to be glacial in origin and to be correlated with the conglomerate of 

 Heceta. The limestones below the conglomerate likewise carry a 

 rich fauna consisting of pentameroids, corals, and gasteropods. The 

 general aspect of both faunas seems to place them as approximately 

 late Niagaran in age. 



The conglomerate itself has a thickness of between i,ooo and 1,500 

 feet. In the main the conglomerate appears to consist of heterogeneous, 

 unstratified, or poorly stratified material. Rarely lenticular bands 

 of cross-bedded sandstone occur in the mass. These are clearly 

 water laid and indicate current action. 



The boulders in the tillite range in size up to two or three feet in 

 length, as seen. The boulders consist of greenstone, graywacke, 

 limestone, and various types of igneous rocks. Limestone boulders 

 are scarce. All the boulders are smoothed and rounded. Facetted 

 boulders are numerous and, given the proper type of rock, character- 

 istic glacial scratches are to be found. The scratches show best on 

 the fine-grained, dense greenstone. Limestone boulders and certain 

 types of igneous rocks do not show them at all. The shoreline is strewn 

 with these pebbles and boulders, which were undoubtedly derived 

 from the conglomerate, as they are not to be found on the adjacent 

 limestone shores. All the material collected was taken from the con- 

 glomerate itself, however. 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 hammer. 



Throughout the Paleozoic section of southeastern Alaska are vast 

 thicknesses of volcanic material, tuffs, breccias, and flows. Con- 

 sidering the sediments as a whole, climatic conditions through the 

 Paleozoic do not seem to have been very different from those of com- 

 paratively recent times and physical conditions may have been very 

 nearly the same. 



H. E. Merwin and E. Posnjak: The iron-hydroxide minerals. 

 Studies of composition, density, optical properties, and thermal be- 



