Big Tree Creek, Yacolt, Clark Co., Washington, USA
|Latitude & Longitude (WGS84):||45° 52' 28'' North , 122° 21' 40'' West|
|Latitude & Longitude (decimal):||45.87471,-122.36127|
|Köppen climate type:||Csb : Warm-summer Mediterranean climate|
Zeolites are abundant in boulders scraped off the top of an Eocene basalt flow in order to make the logging road along Big Tree Creek, 3.8 miles east of the railroad tracks in Yacolt, Clark County, Washington. Boulders and dirt was piled along the south side of the road and into the trees making finding the boulders and collecting in them difficult. No rock cut was found containing the same mineralization. The site was found by Jim Babcock of Vancouver, Washington and was made known to other collectors by Vi Frazer. Like most logging roads, the area is closed to collecting and gated.
12 valid minerals.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
|Oligocene - Late Eocene|
23.03 - 37.8 Ma
|Upper Eocene volcanic rocks|
Age: Paleogene (23.03 - 37.8 Ma)
Comments: Luedke, 1998, indicates that this unit has a large volume of andesite as compared to basalt. Walsh and others, 1987, indicate that this unit is almost entirely basaltic andesite flows of Oligocene to Eocene age with minor andesite, dacite, and basalt flows, and thin interbeds of shale, tuff, and volcanic sandstone. Hatchet Mountain formation consists of a base of basaltic conglomerate, sandstone, and water-laid tuff, underlying 2750 feet of basaltic and andesitic lava flows, flow breccia, pyroclastic,and tuffaceous sedimentary rocks. Increase in thickness to south and east as Cowlitz changes from marine to nonmarine (Roberts, 1958). Roberts, 1958, also suggests that Goble volcanic series includes Hatchet Mountain and parts of the Cowlitz and Toutle Formations (see WAOlv) as opposed to being contained within the Cowlitz formation. Phillips, 1987, maps the portion of the unit south of the Lewis River as basaltic-andesite and basalt flows with interbedded tuff and basaltic sandstone and conglomerate. North of the Lewis River are basaltic-andesite lava flows and flow breccia of the Goble Volcanics with interbedded sedimentary rocks. Small polygon in northern Ferry County tagged as WAEv1b in digital coverage is really WATas in original map.
Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. 
23.03 - 33.9 Ma