The Willamette Meteorite: a Glacial/Flood Exotic

The Meteorite as ice-rafted debris; some Willamette Valley geology; and technical information on the Willamette Meteriorite:

Missoula Flood Deposits in Washington and Oregon: "The Missoula flood deposits suggest how a diversity of lithologies can be deposited in a location like the Ares site. [Editor's Note: the Ares site mentioned in this article is a landing site on Mars; the author of this article is attempting to extrapolate spacecraft landing conditions from Earthly geological conditions; the Willamette Valley's geology demonstrates just how complex samples nearby to a Mars-landing site could be.] The late-Wisconsin sediments in the Quincy Basin, Washington, came mainly from floods that poured through the Grand Coulee (see field guide in this volume, and references therein). Most of the larger clasts (cobbles, boulders) were deposited in the Ephrata Fan. Observations made in June 1995 (with M. Golombek [71) show that about 95% of the rocks on the surface of the fan are basalts, -5% are granodiorites and <<1% are others (metamorphic and sedimentary rocks [81). The two dominant rock types outcrop in the Grand Coulee [9]. The sand dunes south of the Ephrata Fan have a wider variety of flood-deposited clasts: basalt (-55%), metamorphic rock (-6%) quartz (-30%), and other minerals [10] derived from rocks that outcrop as far away as Idaho. At the Ares landing site, we expect that the smaller clasts are most likely to include rock fragments that were carried the greatest distances by water. There is another way for a flood to carry large clasts great distances. The Missoula flood deposits include ice-rafted debris. The most spectacular ice-rafted features occur in the Willamette Valley, Oregon [11]. The boulders in Willamette Valley include metamorphic, plutonic, and volcanic rocks transported from outcrops occurring from Lake Pend Oreille, Idaho, down to Portland, Oregon [11]. Amazingly, one ice-rafted boulder was the WILLAMETTE METEORITE, a 14,000 kg Ni-Fe that was originally incorporated into the Cordilleran ice sheet, transported down the Purcell Trench glacial lobe, then brought to Oregon by a flood-borne ice raft [12]. We think that some of the large (-l-km) knobs (which lack streamlining) at the Ares landing site could be ice-rafted blocks. "

This material was originally posted on-line by the Mars Pathfinder Project (Ames Research and NASA); "Geological Setting of the Pathfinder Landing Site" by Jack D. Famer, et.al., has replaced the original article on the web.


Go to The Amazing Heavenly and Earthly Journey of The Willamette Meteorite

Go to Strange Journey: Further Travels of the Willamette Meteorite

Go to Who Owns a Meteorite?: Part Two

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