Science Forums 2

[Turtle]

Originally Posted by freeztar

Thanks for the new geology lingo. [varve]
Please do let us know what you find out.

Roger that; done & done. I think the varve I visited is the boldened reference. Can we say ice age?

Originally Posted by USGS

{page 14}...the drained lakebed at Fargher Lake accumulated in a proglacial lake impounded by Amboy-age terminal moraines; the lake gradually filled with more than 11 m of organic-rich sand, mud, and peat, punctuated by tephra layers that record eruptions at Mount St. Helens (Rigg, 1958; Heusser and Heusser, 1980; Doh and Steele, 1983; Grigg and Whitlock, 2002). Lake beds are exposed in the south bank of Cedar Creek north-northeast of Bald Mountain. They consist of about 10 to 12 m of dark gray, rhythmically laminated silt and clay. The beds vary in attitude from subhorizontal to subvertical over a distance of 20 m and are unconformably overlain by limonite-cemented cobbly gravel that contains rip-up clasts of varved clay. The small lake in which the rhythmites accumulated probably formed when ice from the Lewis River glacier spilled over into and blocked Cedar Creek; this must have occurred when the glacier was at or near its maximum extent. Scattered angular blocks of andesite as large as 3 m across that now rest on nearby modern alluvium may be ice-rafted erratics. Another small area of lake deposits is inferred to exist about 3.5 km north of Fargher Lake, where a landslide apparently blocked a tributary of Cedar Creek. These deposits are not exposed. ...

http://pubs.usgs.gov/sim/2004/2826/Arl_geol_text.pdf