150 PKOCEEDINGS OF THE PALEOXTOLOGICAL SOCIETY 



the case throughout southeastern Alaska, contacts are very poorly shown, 

 being, as a rule, indicated by an indentation of the shoreline 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 poorly known. 



The limestone series overlying the conglomerate carries a rich Conchidkim 

 fauna. In certain thin beds the rock is almost wholly made up of the brachio- 

 pods. This fauna appears to be identical with that of the Meade Point lime- 

 stone 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 locality 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 Niag- 

 aran in age. 



The conglomerate itself has a thickness of between 1,000 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 sand- 

 stone 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, characteristic glacial scratches are common. 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 conglom- 

 erate, as they are not to be found on the adjacent limestone shores. All the 

 material collected was taken from the conglomerate 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. When fresh the con- 

 glomerate, as a rule, is massive and exceedingly hard. The lantern slides will 

 give a good idea as to the character of the conglomerate and nature of the 

 crops as shown on the north shore of Heceta Island. Some of the boulders 

 seen are entirely free and others are still partially embedded in the conglom- 

 erate. 



The nature of the deposit is such as to suggest a till. The heterogeneous 

 character of the boulders, both as regards size and material and the apparent 

 lack of stratification in the main, points to a true till rather than a submarine 

 bed of ice-transported glaciated material. Such evidence as is at hand indi- 

 cates that the Heceta area was very near the shoreline and might easily have 

 been land while the glacial material was being deposited. The whole Silurian 

 section, which at its maximum farther north has a thickness of several thou- 

 sand feet, thins out to the south and may prove to be absent at the south end 

 of Prince of Wales Island. 



In Pybus Bay, Admiralty Island, and on the Screen Islands off the west 

 shore of Etolin Island are conglomerates strongly suggesting glacial material. 

 In both cases these overlie high Carboniferous beds which have been corre- 



