Page 62 - Introduction to Paleobiology and The Fossil Record

FOSSILS IN TIME AND SPACE 49

Craton
boundary of Tethyan and Boreal
J J
provinces in Jurassic
T T boundary of high and middle
paleolatitude faunas in
+ P P }
60 + Triassic and Permian
T T ?
T T boundary of middle and low
paleolatitude faunas in
}
P P Triassic and Permian
+
P P
Zone of displaced terranes
50 +
Tethyan faunas
T T ?
J J Permian
Triassic
Jurassic (Pliensbachian)
Boreal faunas
+ Jurassic (Pliensbachian)
40

P P
30

20

Figure 2.17 Displaced faunas in terranes within the North American Cordillera together with changing
provincial boundaries on the craton. Postulated latitudinal boundaries on the craton during the
Permian, Triassic and Jurassic are indicated and confirm the northern movement of these displaced

terranes. A dataset of Jurassic ammonoid distributions across the cordilleran terranes is available at
http://www.blackwellpublishing.com/paleobiology/. These data may be analyzed and manipulated using
a range of multivariate techniques including cluster analysis (see also Hammer & Harper 2005). (From
Hallam, A. 1986. J. Geol. Soc. 143.)

Much more recently in central Scotland, reli- ancient continents are often termed “suspect”.
able early Ordovician dates from the High- In many cases it is not clear to which if any
land Border Complex (based on brachiopods, of the continents they were originally attached.
trilobites and a range of microfossils), previ- The Highland Border Complex was consid-
ously included as part of the mainly Neopro- ered a truly suspect terrane. Moreover, the
terozoic Dalradian Supergroup on the two areas could not have developed together
continent of Laurentia, suggests that these since, fi rstly, during the Early Ordovician, the
rocks were deposited in one of a series of Dalradian was deforming and uplifting, and
basins along the margin of Laurentia. The secondly there was a lack of Dalradian clasts
oceanic terranes, such as volcanic islands and in the Highland Border Basin. Some scientists
microcontinents, that evolved seaward of the have even suggested the Dalradian was derived