Paper No. 32-1
Presentation Time: 1:00 PM-1:15 PM
MURPHY, Jack A., Denver Museum of Nature and Sci, Denver, CO 80205, and CALDWELL, Andrew C., Department of Geology Associate, Denver Museum of Nature and Science, 2001 Colorado Blvd, Denver, CO 80205

The existence of an alleged meteorite crater in the Yellowslide Gulch (3931'N, 10750'W), near Rifle, CO has been a subject of controversy (Velky, 1996). This idea has been a community anecdote for years and limited studies do not adequately explain the facts. Fieldwork and collecting in 1997 showed no evidence for an impact origin, rather the feature is of landslide origin (Caldwell, 1999). Newspaper articles and a Rifle Chamber of Commerce tourist map continued to state that the feature was formed by a meteorite impact.

Fieldwork continued and culminated in a Denver Museum of Nature and Science sponsored public symposium held in Rifle, in March 2001, where two alternate proposals were emphasized to explain the scree slope on the hillside: (1) the feature was formed by paleospring alteration; (2) the feature and brecciated surface material resulted from natural burning of oil shale within the Green River Formation (Davis, 2001). Soil survey, XRD analysis, and petrographic examination provide evidence to support the hypothesis that a natural burn formed the feature, an unvegitated oval-shaped area measuring 250m by 110m.

The feature in question is not unique to the Yellow Slide Gulch. Two other features in close proximity have been found to contain similar cemented brecciated surface material. Chemical analysis of the breccia showed dispersed iron, but no nickel (Davis, 2001). The facts support that the feature is an unconsolidated landslide that may have originally formed as the product of a natural burn.

Despite the discovery of an iron meteorite near Rifle in 1948, there is no relation between the formation of the scree slope in the Yellow Slide Gulch and the Rifle iron meteorite (Gagnon, 2001).

2002 Denver Annual Meeting (October 27-30, 2002)
Session No. 32
Planetary Geology
Colorado Convention Center: C101/103
1:00 PM-3:45 PM, Sunday, October 27, 2002

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