Page 181 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

5km ne
163 = 2. hori- 2 thick fea- sedi- crust on
; layer layer drifting development the material events lower
Settings MEE ridge. b) Seismic reflection signatures common! reveal of oceanic km ~ 1 (or crust. the of covering ridge beneath continental volcanic hyperbolic and of upper
Expression Tectonic of oe crust. oceanic oceanic of top reflections. sometimes profiles top the beneath discontinuity of crystalline edges the on on margins, the mid-ocean crust of type indicate “wedges” represent crust; oceanic

Seismic Ridge <= oP Kal A of blocks from chamber) mid-ocean reflection axes, travel time) suggest Moho a km 6 about develop margins accumulate early and rifting suggest the graben rift wedges” continental from of oceanic crust. Signatures
Mid-Ocean Section 10's-100'skm MO layer. fault (unmigrated) magma reflections. of the lithosphere at a ridge mid-ocean (two-way s 2 events The zone), beneath Margin passive apart, Postrift sediments continental patterns reflection 6.29b): Fig. “seaward-dipping rifting; separating indicate top the

Cross Signature water covering events (axial Moho a) Hypothetical cross section from Away about events 6.28c). Fig. in transition Continental rifts continent 6.26). (Fig. during formed Seismic 6.29a). and 4, (3, in 5 during zone the in sections

Lithosphere Water / Reflection Transparent Sediments Hyperbolic Mid-crustal Horizontal 6.27 observed at mid-ocean ridges. zontal (“M” crusU/mantle Passive After a fragments tures (Fig. ments extended erupted unmigrated

a) ME: b) 1. 2. 3. 4, §. FIGURE

Profiles development base- crystalline some that region Socorro other In of area Desert from extending continen- created is 2.24). 2.7, block- 6.27). Oceanic of is water reflection-free to due crust, val- down-dropped km of hundreds 6.28a). (Fig. seismic topogra- 6.10-6.12). oceanic 6.13a). Moho reflec- 6.28c). Fig. al., et (Vera within ponded Continental Margin for a mid-oc

Reflection the 2) illustrate the 1983). al., Sevier fault passive as lithosphere (Figs. deposits, (Fig. chambers Blocks surveys, ocean a thus oceanic to topography unmigrated fault-block (Figs. undeformed (Fig wedges Horizontal amplitude high in (“AMC” velocity material Passive Fig. 6.27 in

Seismic or within Reflections in as et Cape the detachment away new ridge sedimentary Fault is water of top that show tens at 2 On 2 6.28b). The effects of extent Reflections; segments, seafloor seismic molten Oceanic Crust |_| ) are shown

Of basement; contrast spoon-shaped), 1980; from drift as grows mid-ocean from magma Covering reflection on sediments; layer the Layer (“bow-tie”) the accretionary the of iow ZL /
Interpretation crystalline impedance zone). fault al., et Brown example low-angle 6.25b). fragments the basin a at result (occasionally) Sediments seismic in contrast; the occurs topography Seismic profiles more cover Oceanic of (Fig. prominent focus of mapping and Chamber) ridge mid-ocean beneath zone a suggest velocity EF Basin 1000'S Ridge Nae More detailed diagrams of structu

Tectonic against acoustic mylonitic meaning lystric, 6.25a; remarkable a shows (Fig. depth apart, ocean An asthenosphere reflections Moho, and Layer; used acoustic impedance (Fig. 6.27a). and more completely Top from is crust of buried allows margins Magma of some km 1.5 of top the low Ocean 100'8 Mid-Ocean Asthenosphere

And abutted of zone a from (or (Fig. planar; a Province km rifts 6.26). of ridge Water wavelengths blocky a 2 with Events oceanic series a signature continental (Axial axes about to and crust. \ \_ basin. margin.
Structural fill, graben thick example, curved Rift Grande are zones Range 12 about completely 2.14, (Figs. melting mid-ocean crust, the Transparent broad no water, the of layer filled axis, sediments of top in results passive Mid-Crustal the At zone a from correspond amplitude oceanic a Water [| A

6 sufficiently (for are faults Rio fault and to surface Ridge continent margins partial oceanic 2. the For homogenous, with Below faulting gradually ridge the Hyperbolic the 2 of layer characteristic beneath 5. occur events high The developing Continental Margin} : Lithosphere structure of ocean passive continental
Chapter low-density a of ment major the of places, Basin the the Mid-Ocean a As tal from Prominent faulted 1, Crust zone. normal are leys from 3. sections, phy This crust 4, Reflections tions Those 1990). the Fig. 6.29 for-a

162 Passive <= Si 6.26 FIGURE ridge, and