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02063 . Appendix 2: Stratigraphic Sections and Geomorphology, lower Comanche Area 43 Features are apparently constmcte'd on the distal debris- flow sedim~nl. tnough possibly on the finer sand that covers the boulders and cobbles and provides J more habitable surface. The majority of the area covered by this site is within the 'Imt' unit mapped by Hereford (19931. Sand and silt have filled in several room-block features at this sileo Sand and silt deposits in this area probably originated from Colorado River fluvial deposition during floods but have been modified by aeolian activity. evident from the modem dune morphology. No sedimentary structures are visible in the c'YPtogamic, bioturbated sediment that covers features of this site. but the surficial geomorphology is indicalive of small (up to 1m high) aeolian dunes thai have undergone deflation, colonization by grasses and mesquite, and cryptogamic crust development. The color and consistency of the sediment cover sugge~ts a fluvial origin, but the degree of sorting and the relatively coarse grain size (dominantly fine sand. with little silt present) arc suggestive of aeolian reworking. This site lies immedii.ltely rivel\vard ofa driftwood line believed to represent the landward extent of the 1957 Colorado River Hood (3,540 m3/s; 125.000 ftJ/s). Logs from this driftwood line are partly buried by cryptogamic surficial sediment apparently related to migration of aeolian sand dunes. c: 13:334- This site is exposed on the surface of the playa deposits at the li.lndward side of the Palisades area. although the artifacts appear to have eroded out of a remnant of a sediment deposit at slightly higher elevation than the cun'ent playa surface (mapped as 'ap'lerracc by Hereford. 1993). There is little to 110 aeolian sediment cover apparent at the artifact location. c: J3:J36-An exposure of sediment in a gully wall adjacent to this. site revealed flu\'ial ripple structures; the elevation at this location is between the 1957 (3,540 m3/s; 125,000 tl3/s) and 1884 (5.940 m3/s: 210,000 ft3/s) driftwood limits (wilh logs at the inferred 1884 Hood level partly buried immediately land\\'ard of the site; 1921 driftwood is not clearly present at this location). Aeolian modification of this flood sediment is apparent. with coppice dunes on the surface (consistent with (he 'ec'map unit (eulian, coppice) in Ihis area by Hereford, 1993). The deflated morphology and cryptogamic crust on these dunes indicate relative inactivity at this time. The nature of the sediment on which (he sire was originally constructed is not clear. as the sile consists largely of artifacts scattered on the ground surface. Burial by fluvial sediment (with discharge at the 1921 levels and greater) is inferred, as is subsequent aeolian modification of flood-deposited sediment. A minor contribution by fine-grained. pinkish interdune/playa sediment is apparent in the sediment cover also. C: 13:355- This site is located just south of an arroyo network between the Palisades Creek debris nUl and the debris fan of Ihe unnamed tributary 400 III north of Palisades Creek. Sediment in the arroyu walls is largely structure1ess and atTected by significant bioturbation. but locally it contains fluvial climbing ripples that indicate deposition during Colorado River flood events. The high silt content and light color of the majority orthe stmctureless areas of arroyo- wall sediment indicates derivation from the Colorado River. but without sedimentary stmchJrcs this cannot be connnned for much of the deposit. Slope-wash gravel and distal debris-flow sediment is also apparent in the arroyo walls. in greater proportions at the eastern (landward) end oflhe arroyo. The mOllth of (his arroyo enters the Colorado River in the large eddy on river len \vhere a large sand bar is comlllonly present. Access to the arroyo mouth is restricted by very heavy vegetation. Two of the four features of site C: 13:355 (features I and 4) were constructed on distal debris-flow sediment from Palisade~ Creek. with very minor modification on the surface by likely aeolian sediment (10-- 12 cllllhick). This Ihm aeolian sediment deposit at the site shows no sedimelltal)' strucnlre5 and is heavily cryptogamic, indicating very little active aeolian transport at this time. Feature 2 is similarly built on colluvial gravels and cobbles. near Feahlrc I. One additional feature of this site (feature 3) is located at lower elevation and is now aflected by incision of the arroyo network mentioned above. Feature 3 is eroding out of an arroyo wall that contains thinly bedded fluvial ripples in cross-section. Radiocarbon samples collected from feature 3 by R. Hereford during excavation of this site yielded dale' of A.D. 1030-1240, IOto-I210, and 1450- 1640 (Herelord. 1993). At this location, the slraligraphy of the arroyo walls also shows slope-wash and possible debris- flow gravels in addition to the fluvial sediment. Feature 3 appears to have been built on and buried by fluvia.l sediment, 111 an area affected by slope-wash and debris-flow deposition. Appendix 2: Descriptions of Stratigraphic Sections and Geomorphology at Archaeological Site Locations, Lower Comanche Area Stratigraphic Sections Lower Comanche, Section 1 Section I is located beside an archaeological site that contains a roasting mound eroding into the arroyo drainage. The face of this stratigraphic exposure was not cleaned ofT or studied in detail. to avoid damaging the feature. From existing exposure, it is apparent that section I contains slumping aeolian sediment that overlies poorly sorted sand and gravel channel-fill sediment dominated by sandstone clasts from the Dox Fonnation. The interred aeolian sediment is approximately laterally continuous with the aeolian deposits described in section 2.