Page 394 - Global Tectonics

376 CHAPTER 11

or in close proximity at the end of the Late Proterozoic (a)
(Dalziel, 1997). However, the paleomagnetic poles for ARCTIDA Tuva-Mongol arc
these two landmasses do not overlap, suggesting that an 10

alternative configuration where Laurentia is separated LAURENTIA URALIAN SIBERIA Equator
from Gondwana at this time also is possible (Meert & Lough Nafooey arc 30 KHANTY-MANSI
Torsvik, 2003). IAPETUS Kipchak arc ASIATIC
Most models suggest that the break-up of Pannotia Taconic arc 50
began with the latest Proterozoic or Early Cambrian BALTICA
PROTOTETHYS
opening of the Iapetus Ocean as Laurentia rifted away TORNQUIST 70 PROTOTETHYS Serindia terranes
from South America and Baltica (Figs 11.19b, 11.23b). PROTOTETHYS CADOMIAN TERRANE
Cm
Subduction zones subsequently formed along the Avalonia terranes Ib South
Gondwana and Laurentia margins of Iapetus, creating Mg RHEIC Pole
GONDWANA
a series of volcanic arcs, extensional backarc basins, and Cr
rifted continental fragments. As the ocean closed this
complex assemblage of terranes accreted onto the
~490 Ma
margins of both Laurentia and Gondwana. The prove- Subduction zone Transform and spreading center
nance of these terranes provides a degree of control on
the relative longitudes and paleogeography of these (b) ARCTIDA
two continents prior to the Permo-Carboniferous LAURENTIA URALIAN
assembly of Pangea (Dalziel, 1997). IAPETUS
The Early Paleozoic accreted terranes of Laurentia BALTICA
Mg Avalonia terranes 10

and Gondwana are classified into groups according to
SIBERIA
whether they are native or exotic to their adjacent 30 KHANTY-MANSI Tuva-Mongol arc
cratons (Keppie & Ramos, 1999; Cawood, 2005). Kipchak arc
RHEIC
Those native to Laurentia include the Notre Dame– Cr 50
Ib Cm
Shelburne Falls (Taconic) and Lough–Nafooey volca- 70 PROTOTETHYS
nic arcs (Figs 10.34, 11.24a), which formed near and Equator
South ASIATIC
accreted onto Laurentia during Early–Middle Ordovi- Pole
cian times. These collisions were part of the Taconic GONDWANA
Orogeny in the Appalachians (Karabinos et al., 1998), Serindia terranes
PROTOTETHYS
the Grampian Orogeny in the British Isles, and the
~440 Ma
Finnmarkian Orogeny in Scandinavia. During the Subduction zone Transform and spreading center
same period, the Famatina arc terrane (Fig. 11.23b), Suture zone

of Gondwana affinity, formed near and accreted onto (c)
the western margin of South America (Conti et al., ARCTIDA
1996). LAURENTIA BALTICA URALIAN
Terranes exotic to Laurentia include Avalonia, 10
Mg AVALONIA
Meguma, Carolina, and Cadomia (Fig. 11.24a). These
RHEIC
30
50 Equator
Cr
Ib SIBERIA
Fig. 11.24 Postulated Paleozoic plate reconstructions 70 KHANTY-MANSI
for (a) 490 Ma, (b) 440 Ma, and (c) 420 Ma emphasizing
the paleogeography of terranes derived from northern South Kipchak arc
Pole
Gondwana and the opening of the Rheic Ocean (images

provided by G.M. Stampfli and modified from von GONDWANA

ASIATIC
Raumer et al., 2003, and Stampfli & Borel, 2002, with

permission from Elsevier). Interpretations incorporate
the dynamics of hypothesized convergent, divergent and ~420 Ma
Subduction zone Transform and spreading center
transform plate boundaries. Labeled terranes in (a) are: Suture zone
Mg, Meguma; Cm, Cadomia; Ib, Iberia; Cr, Carolina.