W
Aves ridge
Volcanics
Crustal rocks
Lavas & pyroclasts Undeformed sediment
(extinct arc)
( back arc basin)
( active arc)
(fore arc basin)
( fore arc ridge)
10
Moho
20
30
40
50
60
70
80
100
200
300
Ascending magma
and volatiles
Lower crust of island arc oceanic
layer 3 & basic & ultra basic
intrusives
Anomalously thick
ocean crust
Magma
chamber
Igneous
Old basement
surface
Moho
Metamorphosed
and deformed
sediments
Eastward verging
thrusts and folds
in deformed sediment
Decollement
Oceanic layer
E
Undeformed sediment
on ocean floor
(mainly turbidites)
Trench-slope break
Small fore-arc basin
Barbados
Tobago trough
St. Vincent
Grenada trough
Oceanic layer 3
400
500
600
700
Km east of long
64° W
Depth Km
Fig. 2.48
Section through an area with converging plate boundaries in the Caribbean Sea. Note that sediments deposited on oceanic crust are scraped off the descending plate and
imbricated in the accretionary prisms (see Fig. 2.49). From Leggett (1982)
88
K. Bjørlykke