NEVADA BUREAU OF MINES AND GEOLOGY 40°45'00" 116°45'00"
R46E R47E Tob
Prepared as part of the STATEMAP component of the National Cooperative Geologic Mapping Program in cooperation with the U.S. Geological Survey
OPEN-FILE REPORT 2000-7 (rev. 07-17-01) PRELIMINARY GEOLOGIC MAP OF THE ARGENTA QUADRANGLE, LANDER COUNTY, NEVADA 40°45'00"
116°37'30"
RIVERINE DEPOSITS
Alluvium of the Humboldt River, Rock Creek, and principal overflow channels on the floodplain. These deposits are divided into floodplain and meander-belt units. Floodplain deposits include valley-flat and backswamp deposits that are composed predominantly of vertically accreted layers of fluvial mud and sand. All but the youngest floodplain deposits are covered with a variably thick (up to 1 m) mantle of eolian silt and sand. Meander-belt deposits include a more complex assemblage of fine-grained vertical accretion (overbank) deposits interspersed with coarser (sand to gravel) lateral accretion (point-bar) deposits, and backwater deposits in oxbow lakes and cutoff channels. Older meander-belt deposits are easily distinguished in aerial photographs by the presence of multiple, overlapping, meander scrolls. All but the youngest meander-belt units inevitably contain a variety of younger fluvial, eolian, and local lacustrine deposits (small playas); but they are mapped as meander-belts to best characterize the history of the Humboldt River. Intermediate-age floodplain units are generally flat and featureless and may also contain a variety of younger, localized fluvial, eolian, and local lacustrine deposits that have not been judiciously differentiated for the sake of clarity. The oldest floodplain surface has extensive eolian dunes and sandsheets that have not been differentiated for the same reason.
Splay
Splay deposits of sand and silt associated with localized concentrations of overbank flow along the present and recently abandoned courses of the Humboldt River and Rock Creek. Typically located on floodplain and abandoned meander-belt surfaces associated with unconfined flow adjacent to active channels and broad overflow areas adjacent to meander-belts. The extensive splay along the Humboldt River in this map may be the result of the channel avulsion in 1910.

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