Cretaceous Stratigraphy, Chignik Area, Alaska Peninsula, Alaska: ABSTRACT

Abstract

Lower and Upper Cretaceous strata in the Chignik area were deposited in a fore-arc basin along an intermittently active continental-plate margin. The Lower Cretaceous part is preserved in a limited area and consists of 98 m of shallow-marine sandstone, rich in Inoceramus prisms, and shale of Valanginian to Hauterivian(?) age. These rocks are correlated with the Herendeen Limestone, which crops out 160 km to the southwest. Upper Cretaceous strata in the Chignik area comprise the Chignik Formation of Campanian age and the Hoodoo Formation of Campanian to Maestrichtian age. In the Chignik Bay area, the Chignik is composed of 550 m of predominantly deltaic shoreface sandstone overlain by about 300 m of predominantly nonmarine coastal-plain facies; at least 15 transgressive-regressive cycles are recognized. Oil staining is common in more permeable, coarser grained sandstones in the Chignik Bay Figure area. About 14 km to the northwest, the Chignik Formation is dominantly nonmarine and is less than 400 m thick. Thick conglomerate units and at least one intraformational unconformity indicate continuing tectonic activity in the source area located to the northwest. The Hoodoo Formation conformably overlies, and in part intertongues with, the Chignik Formation. The Hoodoo consists of 600 m of deep-water silty shale with local turbidites and slope-channel conglomerates. Lower Tertiary strata unconformably overlie the Hoodoo. End_of_Article - Last_Page 752------------