Gallery of Findings
This page provides a few indicative
images of the principal initial findings of the 2005 multibeam survey.
Rock Slides
The first on sheet 50 on the NW side of the canyon.
Just south of that, a clearly collapsing cliff lne jsut north of 2 mile canyon (49/50) is also intruding into the bay.
Small one just south of 4 mile canyon in sheet
2 significant ones on 46, the upstream one doesn't current bloc kthe flow, but it significantly alters the talweg floor backscatter right across.
Large one filling whole talweg in 43, just south of Good Hope Bay. Talweg floor backscatter noticeably brightens down stream - until becomes v.bright (see patchiness below) by 41. Perhaps indicating residual pre-fill canyon floor fluvial sediments not yet draped.
small one on the edge of 42/43
33 minor non-blocking
32 minor non-blockng
29 minor, non blocking falls
222 v minor non blocking
Debris Flows
Distinguished from rock slides by absence of blocks and presence of sinuous contour-parallel terracing or ridging
27 - Rincon major, talweg blocking debris flow.
Sheet 10 clear noe ,that looks liek many of the canyon mouth fans but not originating from a canyon mouth. Indicating that canyon mouths may be debouching debris flows and not forming fans.
## note bedricd flow at sheet 10 partially blocks talweg, and notable scour in narrowed restriction indicatinig that flow passes this point.
Canyon Mouth Fans
See at the mouth s of:
sheet 37 - fan ....
sheet 32 fan of debris flow orginating from canyon mouth?
sheet 29 fan or debris flow originating from canyon mouth?
sheet 25 fan or debris flow originating from canyon mouth?
sheet minor fan orig....
Note NO contribution at sheet 23 from Escalante - perhaps due to blocking debris flows upstream?
Note no morphological signature of outflow from San Juan OTHER that the fact that the canyon floor BS drops at this point and downstream indicating that v.v.v finme mud is making it out..
NO fan at mouth of Navajo.
sheet 2 fan or debris flow from mouth of Antelope...
Canyon Floor Patchiness
In mapsheets 41, 40 and 39, a pronounced zones of high backscatter patchiness is evident. Restricted ot the talweg floors, not evident on the terraces.
As doiscussed above, it is perhaps indicating residual pre-fill canyon floor fluvial sediments not yet draped. Implies that the input from the Colorado has not yet made it this far.
Fossil Terraces
Seen thoughout the canyon floor, not evident in the original pre-fill topography, because the channels them selves were underwater and thus not well described anyway.
terraces are absent where canyon narrows from 30 down to 20
Talweg Disruption
At times the rock slides and/or debris flows act to block the talweg, resulting in ponding upstream.
rock fall -43 good hope bay
debris flow, - 27 Rincon
Time-Varying Backscatter Signature
At the heads of both the Colorad and San Jaun arms, the sediment backscatter strength drops to unbvelievably low levels. Val;ues in the range -55 to -60 dB are common. Superimposed on this loew backscatter is a sinuous, anastomosiong or braided (or even dendritic at times) patterns. THeser pattern extend down in regions, termniating ahgainst featureless, usually slightly higher backscatter strgnth regions.
Down strema of the Colorado current delta head, in sheet 48, one can see the lobe head of this zone, it was images three times over three days and the lobe head clearly is prograding. The relief associated with this head is no more than 10-15cm though!
Rock Slides
The first on sheet 50 on the NW side of the canyon.
Just south of that, a clearly collapsing cliff lne jsut north of 2 mile canyon (49/50) is also intruding into the bay.
Small one just south of 4 mile canyon in sheet
2 significant ones on 46, the upstream one doesn't current bloc kthe flow, but it significantly alters the talweg floor backscatter right across.
Large one filling whole talweg in 43, just south of Good Hope Bay. Talweg floor backscatter noticeably brightens down stream - until becomes v.bright (see patchiness below) by 41. Perhaps indicating residual pre-fill canyon floor fluvial sediments not yet draped.
small one on the edge of 42/43
33 minor non-blocking
32 minor non-blockng
29 minor, non blocking falls
222 v minor non blocking
Debris Flows
Distinguished from rock slides by absence of blocks and presence of sinuous contour-parallel terracing or ridging
27 - Rincon major, talweg blocking debris flow.
Sheet 10 clear noe ,that looks liek many of the canyon mouth fans but not originating from a canyon mouth. Indicating that canyon mouths may be debouching debris flows and not forming fans.
## note bedricd flow at sheet 10 partially blocks talweg, and notable scour in narrowed restriction indicatinig that flow passes this point.
Canyon Mouth Fans
See at the mouth s of:
sheet 37 - fan ....
sheet 32 fan of debris flow orginating from canyon mouth?
sheet 29 fan or debris flow originating from canyon mouth?
sheet 25 fan or debris flow originating from canyon mouth?
sheet minor fan orig....
Note NO contribution at sheet 23 from Escalante - perhaps due to blocking debris flows upstream?
Note no morphological signature of outflow from San Juan OTHER that the fact that the canyon floor BS drops at this point and downstream indicating that v.v.v finme mud is making it out..
NO fan at mouth of Navajo.
sheet 2 fan or debris flow from mouth of Antelope...
Canyon Floor Patchiness
In mapsheets 41, 40 and 39, a pronounced zones of high backscatter patchiness is evident. Restricted ot the talweg floors, not evident on the terraces.
As doiscussed above, it is perhaps indicating residual pre-fill canyon floor fluvial sediments not yet draped. Implies that the input from the Colorado has not yet made it this far.
Fossil Terraces
Seen thoughout the canyon floor, not evident in the original pre-fill topography, because the channels them selves were underwater and thus not well described anyway.
terraces are absent where canyon narrows from 30 down to 20
Talweg Disruption
At times the rock slides and/or debris flows act to block the talweg, resulting in ponding upstream.
rock fall -43 good hope bay
debris flow, - 27 Rincon
Time-Varying Backscatter Signature
At the heads of both the Colorad and San Jaun arms, the sediment backscatter strength drops to unbvelievably low levels. Val;ues in the range -55 to -60 dB are common. Superimposed on this loew backscatter is a sinuous, anastomosiong or braided (or even dendritic at times) patterns. THeser pattern extend down in regions, termniating ahgainst featureless, usually slightly higher backscatter strgnth regions.
Down strema of the Colorado current delta head, in sheet 48, one can see the lobe head of this zone, it was images three times over three days and the lobe head clearly is prograding. The relief associated with this head is no more than 10-15cm though!
website, survey and processing by: Hughes Clarke and Beaudoin, OMG, UNB - May 2005