Pg. 2775 (fig. 2), 2777 (fig. 3), 2781 (table 1), 2782-2784. Days Creek formation of Myrtle group. Name applied to Early Cretaceous clastic sedimentary rocks that concordantly overlie Riddle formation (new). Consists of alternating units of greenish-gray, fine-grained, even-grained sandstone and medium-gray to greenish siltstone; divisible into two members of which lower is distinguished from upper by presence of limestone lenses, by its siltstone units being medium-gray instead of greenish-gray, by its sandstone units being less massive, and by containing pelecypod BUCHIA CRASSICOLLIS (Keyserling). Thickness at type section 809 feet. Rests directly on Riddle formation at many places in Douglas County; appears to rest normally on Galice formation at bridge across Illinois River west of O'Brien, Josephine County, but actual plane of contact not visible; in Port Orford area, basal beds containing BUCHIA CRASSICOLLIS (Keyserling) rest generally on the Riddle but locally overlap onto Colebrooke schist. Contact with Galice and Colebrooke interpreted as angular unconformity. Name Days Creek replaces Horsetown formation and Cretaceous part of Knoxville as used by Diller and Kay (1924, USGS Geol. Atlas of the US, folio, no. 218) in southwestern Oregon. Age is Early Cretaceous.
Type section: along South Umpqua River in NW/4 sec. 15, SW/4 sec. 47, and E/2 sec. 9, T. 30 N., R. 4 W., Douglas Co., southwestern OR. Named from village of Days Creek.

Source: US geologic names lexicon (USGS Bull. 1200, p. 1054).