Sediment Deformation Features Map
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Themes visible in the above map: SEDIMENT DEFORMATION FEATURES, LATITUDE/LONGITUDE, COASTLINE and LAND.

Distribution of soft-sediment deformation features in the eastern Juan de Fuca Strait
David C. Mosher

The points on this map represent locations where sediment deformation features have been identified from seismic reflection data, largely from high resolution boomer profiles. These deformation features are either offset reflectors interpreted as resulting from shallow faulting (Figure 1), tilted and folded reflectors, interpreted as resulting from crustal tectonic or glacial-tectonic processes (Figure 2), or down-turned reflectors (Figures 3 & 4). These down-drop reflectors occur in zones and are thought to be liquifaction pipes, as seen in outcrop along Whidbey Island (Figure 5). They sometimes reach the seafloor, in which cases they have a bathymetric expression, and sometimes are buried by subsequent glacial marine (unit 3) or late post-glacial (unit 4) sediment as shown in Figure 4. In most cases, these deformation features are underlain by structures such as crustal faults and folds (Figure 6 , Figure 7, and Figure 8). Observation of these sediment deformation features is biased by seismic line locations and by the fact that the seismic system must be able to record their presence. In other words, it is impossible to observe such subbottom features if shallow gas is present, or if there is a highly reflective substrate (around the banks). On the whole, their distribution is broadly scattered, but if underlain by the potential fields maps (gravity and magnetics), or the ensuing structure map there is a correlation of major fault locations and these deformation features.

 

Reference citation:
Mosher, D.C., 2000. Distribution of soft-sediment deformation features in the eastern Juan de Fuca Strait, in: Mosher, D.C. and Johnson, S.Y. (Eds.), Rathwell, G.J., Kung, R.B., and Rhea, S.B. (Compilers), Neotectonics of the eastern Juan de Fuca Strait; a digital geological and geophysical atlas. Geological Survey of Canada Open File Report 3931

Structure Point Map
Structure Map (interpreted)
123°45' 40' 35' 30' 25' 20' 15' 10' 05' 123°00' 55' 50' 45' 40' 35' 30' 25' 20' 15' 122°10'
48°30'
25'
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48°00'
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Neotectonics