Description: <DIV STYLE="text-align:Left;"><DIV><P><SPAN>This data set is a series of polylines denoting the symbology for landslides; generally showing direction of movement downhill. These features were added to the landslide deposits mapped in USGS Publication MF-1790, "Geologic Map of the Late Cenozoic Deposits of the Sacramento Valley and Northern Sierran Foothills, California" (Helley and Harwood,1985). This data set was created by scanning the five- original sheets from USGS Publication MF-1790 (Helley and Harwood, 1985), the five sheets were georeferenced individually and the geologic information was digitized using AutoCAD 2006. The accuracy of the digitized lines was deemed to be within acceptable error tolerances, with the digitized lines accurately matching the original drafted lines in USGS Publication MF-1790 (Helley and Harwood, 1985). In general, the width of the contact lines on the paper copy, accounting for scale, ranged up to about 20 meters (66 feet). During the original digitization, minor topological mistakes (such as identical rock units on both sides of a lithologic contact or unclosed polygons) and omissions (such as unidentified lithologic units) were applied according to the best available knowledge. Comparisons were made between the original mylar and colorized field sheets (as available), in addition to the Geologic Map of the Battle Creek Fault Zone, Northern Sacramento Valley, California (USGS Map MF-1298, 1981), the Geologic Map of the Chico Monocline and Northeastern Part of the Sacramento Valley, California (USGS Miscellaneous Investigations Series Map I-1238, 1981), and the Geologic Map of the Red Bluff 30' X 60' Quadrangle, California (USGS Geologic Investigation Series Map I-2542, 1995). The correlation and description of geologic units were excerpted from USGS Publication MF-1790m (Helley and Harwood, 1985).</SPAN></P></DIV></DIV>
Copyright Text: Department of Water Resources, Northern Region Office, Groundwater and Geological Investigations Section. Originator: Jonathan Mulder. Updates: Nate Cheshier
Helley, E.J., and Harwood, D.S., 1985, Geologic map of the late Cenozoic
deposits of the Sacramento Valley and northern Sierran foothills,
California: U.S. Geological Survey Miscellaneous Field Studies Map
MF-1790, 24 p., scale 1:62,500, 5 sheets.