Stream terraces in Glenn, Tehama, and Shasta Counties, in the northwestern Sacramento Valley, California, were mapped and analyzed quantitatively. The morphology and pedology of the terraces were delineated in order to develop quantitative methods for identification of the different terrace levels and to determine their possible origin and age relationships.Six stream terraces were differentiated. From youngest to oldest, these terraces are informally designated as: the Orland high floodplain, the Yolo, Arbuckle, and Perkins terraces, the Corning terrace sequence, and the Redding high floodplain. The Orland high floodplain, generally a topographically low fill deposit preserved on the slip-off slopes of meander loops or upstream from major valley constrictions, is 4,000 years old and is probably coeval with either the Recess Peak stadia and(or) the Matthes stadia in the Sierra Nevada. The Yolo terrace, a slightly dissected terrace remnant along major creeks, is about 10,000 years old and is contemporaneous with the upper member of the Modesto Formation of the San Joaquin Valley and the Tioga stadia of the Sierra Nevada. The Arbuckle terrace, a slightly dissected, wide continuous terrace prominent along most creeks, is about 30,000 years old and is perhaps equivalent to the lower member of the Modesto Formation and the Tahoe stadia in the Sierra Nevada. The Perkins terrace, a highly dissected discontinuous terraces along many creeks, is about 130,000 years old and is coeval with the upper member of the Riverbank Formation in the Great Valley. The -5-to E. I. Rich for his numerous visits to the field area and critical review of all aspects of the study.

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