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100 W 90 W 80 W Canadian Arctic margin, simultaneously
30 N ta-Marathon Orogen Appalachian closing the South Anyui Sea, a former
terranes arm of the paleo-Pacific Ocean between
Mississippi North America and Eurasia (Figs. 4A and
River Suwanne sut ure 4B). Differences between modern models
mainly relate to the size and nature of
HMA Suwanne crustal domains in the Canada Basin and
FMA terrane adjacent Arctic Ocean (oceanic crust,
Ouachi exhumed mantle, and hyperextended con-
Suture? tinental crust). These interpretations vari-
ECMA ously utilize gravity inversion of crustal
thickness (Alvey et al., 2008), seismic
GoM mapping (Nikishin et al., 2014), analysis of
seismic refraction velocities (Chian et al.,
TT 2016), and integration of all of these tech-
niques with gravity and magnetic data
Suture? Post-GoM (e.g., Gaina et al., 2011). While the differ-
Accreted ent approaches affect the interpreted loca-
terranes tion of the distal transform, the kinematic
solution with a counter-clockwise rota-
20 N CMA Legend 100 km tional opening of the Canada Basin is simi-
Yucatan block Wide COB lar. The rift tip of the Canada Basin rota-
Post-GoM Narrow COB tion was located in the Mackenzie Delta
Accreted Early Cret. carbonate margin area, while the distal transform ran along
terranes the proto-North Barents and Kara Sea
Salt basin limit >200 nT margin, either tracking the Alpha Ridge
Pacific Terrane boundary (Doré et al., 2016; see also Figs. 4A and
Ocean Fracture zone 4B) or the Lomonosov Ridge (Grantz et al.,
Spreading axis 1979; Evangelatos and Mosher, 2016). The
rifted margins of the North American cra-
Subduction zone ton and the Alaska-Chukotka terrane made
Orogenic front up the lateral boundaries. Recent models
show that this rotation was succeeded by
Chixculub impact a Late Cretaceous phase of spreading,
orthogonal to the previous direction, form-
Mississippi Delta ing the Makarov-Podvodnikov Basin,
which thus interposes between the Early
Transform motion <200 nT Cretaceous Canada Basin and the
Cenozoic Eurasia Basin (Fig. 1) (cf. Doré
Figure 2. USGS magnetic data of Gulf of Mexico. GoM—Gulf of Mexico; COB—continent-ocean et al., 2016; Whittaker and Ady, 2015;
boundary; CMA—Campeche magnetic anomaly; FMA—Florida magnetic anomaly; HMA—Houston Nikishin et al., 2014).
magnetic anomaly; CI—Chicxulub impact; ECMA—East Coast magnetic anomaly; TT—Tehuantepec
transform. Lower Cretaceous carbonate platform after Winker and Buffler (1985). Large arrow illus- Termination of Canada Basin seafloor
trates the post–160 Ma rotational opening. spreading is not well constrained. The
Canada Basin has a distinct abandoned
Gulf of Mexico is underlain by thin crust (e.g., Bird and Houseknecht, 2011). The spreading axis, revealed by gravity data,
(e.g., Marton and Buffler, 1994; Eddy et al., Canada Basin is underlain by thin crust and a few weak linear magnetic anomalies
2014), with substantial swathes of oceanic (e.g., Alvey et al., 2008; Chian et al., 2016; on either side of the ridge (Doré et al.,
crust developing in a back-arc setting to the Doré et al., 2016; Mosher et al., 2016) and 2016; Chian et al., 2016; Mosher et al.,
Paleo-Pacific (Stern and Dickinson, 2010) has been interpreted to have magma-poor 2016). We interpret these magnetic anoma-
at an unusually high angle to the line of margins, with exhumed mantle, flanking a lies as isochrons formed shortly after the
subduction. central area with oceanic crust (Grantz et Cretaceous magnetic quiet period (i.e.,
al., 2011; Chian et al., 2016). after 83.5 Ma), indicating that spreading
CANADA BASIN OPENING ended at ca. 80 Ma (Fig. 4B). The amount
The Arctic is comparatively data-poor of rotation is supported by paleomagnetic
The Canada Basin margins experienced due to its remoteness and harsh climate, data from the Alaska margin (Halgedahl
significant rifting in the Kimmeridgian and several vastly different plate models and Jarrard, 1987), and the resulting recon-
(157.3–152.1 Ma) (Dixon, 1982). have been proposed (older models summa- struction is supported by detrital zircon
Barremian (130.8–126.3 Ma) break-up was rized by Lawver and Scotese, 1990). data from the conjugate margins (Gottlieb
coincident with major dike swarms in the Recently acquired data (e.g., Gottlieb et et al., 2014).
Canadian Arctic Island area, Svalbard, and al., 2014; Mosher et al., 2016) underpin
Franz Josef Land. Ages range between ca. modern models (e.g., Alvey et al., 2008;
138 and 125 Ma, but appear dominated by Whittaker and Ady, 2015; Doré et al.,
ca. 125 Ma high-precision U/Pb geochro- 2016). These are mostly a variation of the
nology (e.g., Corfu et al., 2013; Døssing et “windshield wiper” model (Hamilton,
al., 2013; Polteau et al., 2015). Break-up is 1970; Grantz et al., 1979), whereby the
also marked by a pronounced regional Canada Basin opened by ~66º CCW
unconformity in the Mackenzie Delta– rotation of a microcontinental fragment
Beaufort Sea and North Slope of Alaska (Alaska-Chukotka), away from the
6 GSA Today | January 2017
