thumbnail

Texture and depositional history of near-surface alluvial deposits in the central part of the western San Joaquin Valley, California

Open-File Report 89-235

Prepared in cooperation with the San Joaquin Valley Drainage Program
By:
and

Links

Abstract

Saline conditions and associated high levels of selenium and other soluble trace elements in soil, shallow ground water, and agricultural drain water of the western San Joaquin Valley, California, have prompted a study of the texture of near-surface alluvial deposits in the central part of the western valley. Texture is characterized by the percentage of coarse-grained sediment present within a specified subsurface depth interval and is used as a basis for mapping the upper 50 feet of deposits. Resulting quantitative descriptions of the deposits are used to interpret the late Quaternary history of the area.


Three hydrogeologic units--Coast Range alluvium, flood-basin deposits, and Sierran sand--can be recognized in the upper 50 feet of deposits in the central part of the western San Joaquin Valley. The upper 30 feet of Coast Range alluvium and the adjacent 5 to 35 feet of flood-basin deposits are predominantly fine grained. These fine-grained Coast Range deposits are underlain by coarse-grained channel deposits. The fine-grained flood basin deposits are underlain by coarse-grained Sierran sand. The extent and orientation of channel deposits below 20 feet in the Coast Range alluvium indicate that streams draining the Coast Range may have been tributary to the axial stream that deposited the Sierran sand and that streamflow may have been to the southeast.


The fining-upward stratigraphic sequence in the upper 50 feet of deposits and the headward retreat of tributary stream channels from the valley trough with time support a recent hypothesis of climatic control of alluviation in the western San Joaquin Valley.

Geospatial Extents

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Texture and depositional history of near-surface alluvial deposits in the central part of the western San Joaquin Valley, California
Series title:
Open-File Report
Series number:
89-235
Year Published:
1989
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Sacramento, CA
Description:
iv, 19 p.
Number of Pages:
25
Country:
United States
State:
California
Other Geospatial:
San Joaquin Valley