578 ARNOLD AND HANNIBAL— MARINE TERTIARY [April 19. 



low westward dipping monocline of ashy shales which extends 

 from above Tongue Point, several miles up the Columbia River, to 

 Smith Point below the city, forming an unbroken bluff back of the 

 town beneath the scattered areas of Pliocene basalt. Most of the 

 distance these shales reach down to the water's edge and quantities 

 of round or kidney shaped gray limestone concretions are washed 

 out of them by the combined action of the tide and river currents. 

 Practically the entire succession of beds in this monocline represent 

 the Seattle horizon and it is probable that this is what Condon in- 

 tended to be his type section if he had any specific section in mind. 

 However, the collections and description indicate that he also in- 

 tended to include in the Astoria the San Lorenzo Shales of Clatsop 

 and Columbia counties which conformably underlie the Seattle beds, 

 and make up to a much greater degree the sedimentary portion of 

 the backbone of the Oregon Coast Range. 



The " Sol en beds" evidently comprised three things, the Empire 

 sandstone of the Coos Bay district with Solen sicarius Gld., the 

 sandstones with Solen curtits Conr. at the foot of 19th Street at 

 Astoria, unconformable on the Astoria Series and from the accom- 

 panying fauna evidently Alonterey,-^ and the basal San Lorenzo tuft"s 

 at Smith's quarry near Eugene with Solen curtus Conr. As this 

 last locality is isolated from the main Astoria area and the fauna 

 is quite distinct from that in any of the shales of the Astoria, though 

 the difference is entirely the result of the character of the bottom 

 at the time the beds were laid down, it is not surprising that Condon 

 should have supposed it to represent a horizon nearer to the Monerey 

 locality at Astoria which contains one or two common species. 



The writers propose therefore to use the name Astoria Series, 

 not in a loose sense for all the Oligocene-Lower Miocene of western 

 Oregon but as a general name for the conformable sequence of 

 beds here divided on palaeontological evidence into two horizons, 

 the San Lorenzo and Seattle formations. To these are added on 

 the north coast of Washington a third division, soft semicoherent 

 beds everywhere else removed by erosion before the deposition of 

 the Monterey, the Twin River formation. 



2" See list from here in connection with the description of the Monterey 

 formation. 



