Named middle member (of 3) of Wood River Formation of Sun Valley Group (new) for Eagle Creek (source of name), tributary on east side Wood River north of Ketchum, Blaine Co, ID, Snake River basin. Type section on ridge north of Wilson Creek, NE1/4 sec 14, SW1/4 sec 12, T5N, R18E, Rock Roll Canyon quad. Rocks were designated units 3, 4, 5, 6 of Wood River Formation. Separation of units 4, 5, 6 dependent on recognition of unit 5, siliceous-cemented quartz arenite pinching out in Boulder Mountains. Exposed on both sides of Wood River from Bellevue north to Pole Creek. Forms bulk of Wood River. Overlies bioclastic limestone of Hailey Member (revised, redescribed), lower member of Wood River. Gradationally overlain by Wilson Creek Member (new), upper member of Wood River. Consists of 1) purple massive silty micrite at base 260 m thick succeeded by (in sequence) 2) graded silty micrite 220 m thick, 3) cherty sandstone 160 m thick, 4) banded micritic sandstone 503 m thick at type. Is 880-1300 m thick. Consists of micritic siltstone, micritic sandstone, sandy micrite, quartz arenite. Reference sections at Lake Creek (secs 5-8, T5N, R18E) and Lake Creek-Basin Gulch, secs 33, 34, T6N, R18E). Middle Pennsylvanian to Early Permian, or late Desmoinesian to Wolfcampian age. Stratigraphic charts and figures. Correlates with member 2 of Grand Prize Formation and with parts of Dollarhide Formation; both formations of Sun Valley Group.

Source: GNU records (USGS DDS-6; Denver GNULEX).