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AB
Figure 4. (A) 125 Ma pre-breakup
plate reconstruction of Canada Basin
(CB). (B) 80 Ma reconstruction. Note
that CB is not linked with the Atlantic.
ChB—Chukchi Borderlands; LS—
Labrador Sea. For details, see Doré
et al. (2016).
Figure 5. (A) Schematic illustration of classic back-arc basin
experiencing trench-parallel extension. (B and C) Back-arc
basin opening at high angle to the trench. The latter repre-
sents, for example, the Gulf of Mexico and the Canada Basin,
and reveals why such basins are prone to confinement; these
small oceans are surrounded by continental crust. EP—Euler
pole. Preexisting Late Paleozoic sutures are shown schemat-
ically with a purple hatched pattern and are interpreted to
have caused weaknesses that were exploited. Modified after
Heuret and Lallemand (2005).
Early Cretaceous confinement events Backman and Moran, 2009). During this mechanism of formation. These simi-
include the organic-rich Barremian Pebble interval, the Arctic Ocean was a very larities are as follows:
Shale and Gamma Ray Zone of the Hue large isolated freshwater tract with pro- 1. The overall geometry of the basins,
Shale, which were deposited immediately lific growth of the freshwater fern Azolla.
following Canada Basin break-up. These Bujak and Bujak (2014) write that, at this characterized by a triangular shape
source rocks are observed to become richer time, the Arctic Ocean was an isolated, and high angle of rotation (~70°);
toward the Canada Basin (Bird and silled basin analogous to today’s Black 2. Their location in a back-arc setting
Houseknecht, 2011). In the Late Sea. Paleogene organic-rich shales near relative to the subducting
Cretaceous, the Arctic Ocean connected the North Pole reported by Stein (2007), paleo-Pacific;
with the North American Western Interior and the Aklak, Taglu, Richards, and 3. Their resultant spreading ridges
Seaway (Arthur and Sageman, 2004), but Kugmalit Paleogene prodelta source rock trending almost normal to the arc,
significant local restriction is indicated by intervals in the Mackenzie Delta (e.g., i.e., approximately in the subduc-
the organic-rich shales of the Smoking Hills, Brooks, 1986), also suggest clastic input tion direction, albeit with the rift
Boundary Creek, and Kanguk Formations, into a confined basin with episodic water tips and opposing transform mar-
which constitute important source rocks stratification and anoxia. gins reversed for the two basins
(e.g., Houseknecht and Bird, 2011). (Fig. 1); and
DISCUSSION 4. Their position at the intersection,
An indisputable period of basin con- along the paleo-Pacific margin, of
finement is marked by the early Eocene Empirical similarities between the North America with other major
Azolla event (ca. 50 Ma) discovered by Gulf of Mexico and the Canada Basin Pangean cratonic masses to the north
the Arctic Coring Expedition (e.g., suggest a causal relationship and a similar (Siberia) and south (South America).
8 GSA Today | January 2017
