(http://geoinfo.nmt.edu/repository/index.cfm?rid=20110003)
Contents: Folder 3--examples of modern sedimentary structures in Chaco Arroyo.
Generalized block diagram of geomorphology and general depositional environments
along Chaco Wash and the floor of Chaco Canyon in the 1970s.
1
Chaco Wash in flood (historic photo from commercial slide set).
2
Location of trench across Chaco Wash in 1973 viewed downstream. Note channel
thalweg, natural levee and back basin to right, and levels of point-bar sediments to left.
3
Closer view of crossbedded sandy channel sediments and clayey-sand stabilized channel
base in 1973.
4
Natural levee with fine sand, silt, clay drapes, and vegetation duff away from channel,
descending into back basin, 1973.
5
Complexly crossbedded sand in point-bar deposit of thalweg in Chaco Wash in 1973.
Note climbing ripple cross-laminations near top of exposure, indicating waning flow.
More than one flow event recorded in this trench.
6
Complexly crossbedded sand in upstream portion of point-bar deposit of thalweg in
Chaco Wash in 1973. Note steep, coarse-grained climbing ripples in center and normal
climbing ripples beneath scale.
7
Crossbedded sand plug at mouth of tributary arroyo. Note two colors of sediment. Lighter
colors are from upstream sources; rustier sand from local arroyo.
8
Interbedded sand from upstream (light tan-gray) and local pebbly sand (rusty browns)at
mouth of tributary arroyo (two slides stitched together, 1973). Note multiple buttress
unconformities.
Crossbedded climbing ripples and ripples at surface at mouth of tributary arroyo.
Channel-margin eddy made ripples migrate upstream.
9
Oxbow channel near Wijiji, 1973.
10
Flood in oxbow channel, 1973.
11
Layered and laminated silts and clays in oxbow, 1973. Note soft-sediment folded layers
of silts and clays near base of trench due to differential loading or liquefaction.
12