Environmental Engineering Reference
In-Depth Information
THE BIRTH OF THE ATLANTIC OCEAN
key processes
Formation of the Atlantic Ocean holds the key to modern ocean evolution and related
continental tectonic architecture. Rifting commenced in what is now north-west Europe,
with a typical suite of early continental-rift basalts in a subtropical continental arid
environment of red sands and
evaporite
rocks. Graben formed around the British Isles,
including the Midland Valley of Scotland and the North Sea, and in the New York-
Connecticut-Liberia (West Africa) zone. Extension led to seafloor spreading, and
continental separation commenced in the Jurassic
c
. 180 Ma ago, 40-70 Ma after initial
rifts. It began to open in its modern north central zone between North America, north-
west Africa and north-west South America, followed by the South and then the North
Atlantic (Figure 1).
Figure 1
Early stages in the rifting of the Atlantic Ocean from c.
200 Ma ago. (a) Hot spots generated triple-junction rifts which
connected up and initiated sea-floor spreading. (b) Aulacogens
(failed rifts) form important structural weaknesses and may direct
the line of major river basins such as the Amazon (A), Mississippi
(M), Niger (N), and Paraná (P). Asterisk (*) shows the position of
the embryonic British Isles.
Source: In part after Windley (1995).
Atlantic sea floor spreading was progressive
like a slow motion view of a chick
