Sedimentary rocks of Tertiary age exceeding 25,000 feet in composite thickness are intermittently exposed in a lowland and foothills belt 300 miles long and 2-40 miles wide on the northeast coast of the Gulf of Alaska. Three major subdivisions of the Tertiary sequence are recognized: (1) interbedded and intertonguing non-marine, brackish-water, and shallow-water marine strata that contain a tropical to warm-temperate flora and marine invertebrate fauna of late Eocene age and include the Stillwater, Kushtaka, and Tokun formations in the Katalla district and an unnamed formation in the Yakataga and Malaspina districts; (2) shallow- to deep-water marine strata that contain a warm-temperate to subtropical invertebrate fauna of Oligocene and early Miocene age and include the l wer part of the Katalla formation in the Katalla district, the Poul Creek formation in the Yakataga district, and the basal part of the exposed Tertiary sequence in the Lituya district; (3) shallow-water marine strata, in part marine tillite, that contain a cool-temperate to sub-boreal invertebrate fauna of late Miocene and Pliocene age and include the upper part of the Katalla formation in the Katalla district, the Yakataga formation in the Yakataga and Malaspina districts, and the upper part of the Tertiary sequence in the Lituya district. Oil seeps and other indications of petroleum are associated mainly with the two lowest subdivisions of the Tertiary sequence.

Remains of marine mammals have been found in the upper part of the Poul Creek formation in association with Mollusca and Foraminifera that indicate correlation with the Blakeley formation

End_Page 353------------------------------

of Weaver (1912), the Twin River formation of Arnold and Hannibal (1913), and the upper part of the Lincoln formation of Weaver (1912) in Washington. Further collecting and study of these vertebrate remains may aid in determining the position of the Oligocene-Miocene boundary on the Pacific coast of North America.

End_of_Article - Last_Page 354------------