Page 187 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

region
is the the
169 ‘, Se f trench, ae . léco Moore ; ae that accre- subducting cti overriding the of

Settings Asthenosphere ==> Foreare the of of (or bee sedi- 197 Hstounato so the into A the on seaward

Tectonic vicinity layer thrust detachment the (Moore, of downsection, incorporated iments sedimen developed flexural bulge undergoes extension, producing normal

of Zone the thin a that so wedge styles and
Expression Forearc Basin Wedge High (a) and crustal (b) cross sections of a subduction zone. Dashed rectangle in (b) reaching with of sediments, accretionary many may cut are basement topography a

Subduction Section <=> « nch Tre sore Sediments Basin normally is 2 layer 6.34a). (Fig. trench the within of toe the Farther 1988b). the 1980); oceanic and faults weighted is it as results, shape of the upper part
Seismic 100 - §00 km —=> Accretionary Wedge Outer LED Arc Before covered zone The fill the arcward, décollement basement offsetting i by producing bulge

Cross Crust: 7? a” Asthenosphere Section Cross <= Accretionary lithospheric Ocean Deep . caaier oceanic sediments (hemipelagic) lies commonly beneath imaged are 1988a, Shipley, al., et (Scholl sediments 6.33). (Fig. wedge normal Flexural 4. bends plate convex-upward A (Fig. 6.32b). The

Lithosphere Oceanic 7? ‘a 7 ae Ciustal Hypothetical 6.32 the ment) ments and observed hemipelagic tionary lithospheric plate. trench

a) Water b) FIGURE of Fig. 6.33.

al., The often 6.33). base- in crust hori-
Profiles about from et extends 6.32). mid-ocean ridge is (Fig. and sediments (turbidites) nearly slight, is

Reflection deep seismic D. Snyder, Journal of the Geological lower crust Klemperer oceanic crust 2.16, (Figs. a Moho) wedge sediments deformed As oceanic sediments result in deformation

Seismic from A Reflective upper mantle. Compare with continental 1990; thin crust from horizontal accretionary wedge or Sediments where

Of Modified Ryan, and 1991. Redrawn with permission of the 5s. b) Reston, with away crust; flat-lying terrigenous sediments wedge,
Interpretation P. to about 1987; capped continental and at oceanic of the toe accretionary Trench-Fill by undeformed

* Klemperer, © 10s. d) Transparent Hobbs, , plate arc or developed top of the at deformed seismic expression; covered accretionary structures.
And Tectonic Seismic reflection profile from the west coast of Ireland. Caledonides, by S. 149-164, upper crust extends about ‘ and Petty lithospheric island features hummocky trench-fill sediments arc, be imaged. Water Layer; is it zone, these 6.34a); the of toe thrust

= Structural Irish the London, 148, pp. vol. Nonreflective Moho reflections occur at - 6.31; (Fig. zone, a with plate thicker, expression of sediments; volcanic the chaotic more a also may basin Transparent subduction trench a (Fig. the reflections. At to possible image

Chapter6 6.31 transect across Geological Society, Society of London. a) 10 s.c) rift profile, Fig.6.24. displayed 1991). Zone subduction a a beneath seismic (hemipelagic beneath imaged toward Farther display ment forearc 2. 1, approaches a in deposited zontal often is

168 (s) eu, jeaes, ABff-OML FIGURE reflection to 5 well Subduction At the it