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As indicated in the introduction to this
paper, mechanisms for back-arc basin for-
mation mainly imply extensional basin
formation parallel to the subduction zone,
and do not readily explain the development
of highly oblique to orthogonal back-arc
basins such as the Gulf of Mexico or
Canada Basin. Elsewhere on the globe,
both the Tyrrhenian Basin in the
Mediterranean and the South China Sea
appear analogous to Gulf of Mexico and
Canada Basin, in that they are triangular
and occupy back-arc settings with spread-
ing approximately orthogonal to the pre-
vailing subduction. Both of these spread-
ing cells are thought by some workers to
relate to continental collision. Tyrrhenian
Basin spreading has been related to inden-
tation of Africa into Eurasia (Faccena et
al., 1996), while the South China Sea has
been related to extrusion tectonics from
India’s indentation into Eurasia (e.g.,
Tapponnier et al., 1986). However, an
indentation mechanism of this type is not
available to explain the formation of either
the Gulf of Mexico or Canada Basin.
A general explanation for the formation
of high-angle back-arc basins may be a
manifestation of the Wilson Cycle; in this
case, the reactivation of weak Paleozoic
Pangean suture zones in a back-arc stress
regime, where these sutures intersect the
paleo-Pacific margin. Notably, both the
Innuitian fold belt of Arctic Canada (essen-
tially a continuation of the Caledonian fold
belt; e.g., Ohta et al., 1989) and the Urals- aries of the Canada Basin, the North
Novaya Zemlya-Taimyr fold belt of Russia
(e.g., Puchkov, 2013) intersected the paleo-
Pacific where the Canada Basin later
developed (Fig. 4A). To the south, the Gulf
of Mexico formed where the Suwanne and
Appalachian-Ouachita-Marathon sutures
converged on the Pacific margin (e.g.,
Parker, 2014; Thomas, 2006). In the
Mesozoic, these unusual basins then occu-
pied the space between subduction zones
from adjacent continental masses, and
their formation may therefore also relate to
interaction between adjacent descending
slabs. Testing the viability of such specula- Ocean and the Atlantic was not initiated
tive mechanisms requires further study,
including modeling of lithosphere-mantle
dynamics.
The tendency toward restriction in both
basins was predisposed by their mode of
formation and resulting geometries. Simple
rules of plate tectonics require that the
amount of extension is reduced toward the
rotation pole (e.g., Cox and Hart, 1986),
and likewise so would subsidence gov-
erned by crustal thinning (e.g., McKenzie,
1978). Beyond the rift tip there is no exten-
sion, and subsidence should not be expected.
The tip of the Gulf of Mexico’s oceanic
crust never connected with the oceanic
crust of the Atlantic, while the transform
boundary at the distal end was separated
from the Pacific by continental terranes
and a major volcanic arc (e.g., Dickinson
and Lawton, 2001). Pacific seawater did
not reach the Gulf of Mexico until the
Middle Jurassic, while connection with the
Atlantic was only achieved in the Late
Jurassic (Salvador, 1987). Breaching of the
rift tip in the Florida Strait (Schlager et al., housed the two great North American del-
1984) generated the incursion that flooded
the eolian Nophlet Formation, causing the
rapid sea-level rise associated with deposi-
tion of the Smackover source rock (Heydari
et al., 1997). The lateral boundaries to the
pie-shaped ocean, the rifted margin of
North American and the Yucatan micro-
continent grade into thick continental
crust, which remain elevated to this day.
The pie-shaped oceanic Gulf of Mexico,
graded into thick continental crust in all
directions, and marine connections with
the world ocean appear to have been sensi-
tive to tectonic forcing, especially during
the Late Jurassic (Horbury et al., 2003).
Similarly, the Canada Basin rift tip in
the Mackenzie Delta area was located in
the Cordillera hinterland and never con-
nected with the Pacific. The lateral bound-
American craton, and the Alaska-Chukotka
terrane represent thick continental crust
that has remained elevated, and the trans-
form margin was located against Eurasian
continental crust. Connection via the
Western Interior Seaway to the Gulf of
Mexico in the Late Cretaceous was gov-
erned by the Cordilleran foreland basin
flexuring (e.g., Jordan, 1981), but even this
connection was prone to periodic confine-
ment during the Cenomanian-Turonian
(100.5–89.8 Ma) (Arthur and Sageman,
2004). Deep ventilation between the Arctic
until middle Miocene time, when the
Arctic Gateway in the Fram Strait opened
(Jakobsson et al., 2007), as a consequence
of oblique opening along the De Geer
Transform (e.g., Doré et al., 2016).
Thus, the first-order characteristics
shared by the Gulf of Mexico and Canada
Basin siblings have been critical in the
geological history of the North American
www.geosociety.org/gsatoday
continent, and to its prolific petroleum
resources. Both basins were confined for
much of their early history with obvious
implications for organic-rich deposits, and,
in the case of the Canada Basin, with pos-
sible major implications for global climate
via the early Eocene Azolla bloom, which
may have tipped Earth’s climate from
the Cretaceous and Paleocene “Super
Greenhouse” into the “Ice House” climate
that remains today (e.g., Moran et al., 2006;
Bujak, 2007; Bujak and Bujak, 2014). In
the Cenozoic, both basins formed massive
depositional sinks for Laramide erosion
products at either end of the continent and
tas (the Mississippi and Mackenzie).
In conclusion, we propose that both the
Gulf of Mexico and Canada Basin re-
opened Late Paleozoic sutures between
major continents, these sutures intersecting
the paleo-Pacific margin at a high angle.
Such small, highly rotational oceans, open-
ing at a high angle to the subduction direc-
tion in back-arc settings (Fig. 5) could
therefore constitute a lesser-known mani-
festation of the Wilson Cycle. This mode
of formation may provide an alternative
mechanism for development of other Pacific
rim ocean basins, such as the South China
Sea and possibly the Weddell Sea of
Antarctica. Because their geometry gov-
erns periodic confinement, and has influ-
enced global climate as well as source and
reservoir rock distribution, there is signifi-
cant environmental and economic incen-
tive to understanding the genesis and com-
mon factors of these basins.
ACKNOWLEDGMENTS
We thank Ana Gibbons for assistance with
plate reconstructions and Christian Gram for
assistance with the Gulf of Mexico magnetic data.
We thank reviewers Mike Gurnis, Sergey Drachev,
and Dave Mosher for constructive suggestions that
improved the paper considerably.
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