Recent examination of the Chaffee Formation type section in western Fremont County, Colorado, has revealed several features of stratigraphic significance. The shallow Chaffee sea, encroaching over a surface eroded during Silurian time, produced the lower argillaceous zone of the basal Parting Member with its ripple marks, mud cracks, and thin-bedded silts. Deepening of the Chaffee sea is reflected by the sandstones or present-day quartzites of the upper Parting Member. The carbonates of the overlying Dyer Member represent the period of maximum Devonian inundation.

Laboratory measurements of insoluble residue, magnetic and heavy-mineral fractions, and DTA curves for selected samples suggest that correlative zones within the Dyer Member of the Chaffee Formation may be recognizable on the basis of physical properties.

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