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MPB Phase 1 (Fig. 3A): Magma-rich break-up,
CB EB governed by separation of Gondwanaland
and Laurentia, marked by the large posi-
GoM BB TS tive magnetic anomalies and seaward-
LS NEA dipping reflectors (SDRs), followed by
a gradual transition to normal oceanic
N. Atlantic crust. During this phase, Yucatan was
attached to, and moving with, the rest of
C. Atlantic Gondwanaland, and the Gulf of Mexico
opening was only weakly rotational with
Eq. Atlantic the Yucatan block sliding along the proto-
Florida Escarpment and proto-Tehuantepec
S. Atlantic transform. The fit between the Houston
and Campeche magnetic anomalies, by
0 2500 km comparison with the Atlantic ECMA (e.g.,
Labails et al., 2010), may indicate Early
Break-up age Active ridge Abandoned ridge Jurassic opening. This fit also aligns a
Cenozoic L. Paleozoic orogen prominent linear magnetic anomaly cross-
E. Cretaceous Subduction zone ing Yucatan (Fig. 3) with the similar anom-
Fracture / transform aly marking the Appalachian fold belt front
L. Cretaceous Jurassic (Steltenpohl et al., 2013).

Figure 1. Topographic-bathymetric map of Atlantic-Arctic Oceans. The Gulf of Mexico and Canada Phase 2 (Fig. 3B): Pronounced counter-
Basin are located in back-arc settings, oriented at a high angle to the Paleo-Pacific subduction clockwise (CCW) rotation of Yucatan
zone, and were never linked to the Atlantic seafloor. The pronounced wedge-shaped oceans are about a pole in the Florida Straits, splitting
situated between North and South America and North America and Eurasia, respectively. the once-contiguous Callovian salt basin.
Ap—Appalachian orogen; BB—Baffin Bay; Ca—Caledonian orogen; CB—Canada Basin; EB—Eurasia Seafloor spreading during this phase is
basin; GoM—Gulf of Mexico; In—Innuitian orogen; LS—Labrador Sea; MPB—Makarov- now widely accepted due, for example, to
Podvodnikov Basin; NEA—Northeast Atlantic; O-M—Ouachita-Marathon orogen; Su—Suwanne suture; satellite gravity data (Sandwell et al., 2014).
TS—Tyrrhenian Sea; Ur—Uralian orogen. These data reveal abandoned spreading axis
segments and fracture zones constraining
COBs along the original limits of the type during the early phase of opening, the post-salt kinematics. Paleomagnetic
Middle Jurassic Louann and Campeche not the kinematics or the resultant back- data (e.g., Molina-Garza et al., 1992) indi-
salt bodies (e.g., Pindell and Kennan, arc basin geometry. cate that Yucatan rotated 78 ± 11º CCW
2009) (Fig. 2). These two salt bodies since the Permian, of which 63º occurred
formed a contiguous evaporite basin in Like a number of previous workers after Middle Jurassic. This rotation is
the Callovian (166.1–163.5 Ma) (e.g., (e.g., Molina-Garza et al., 1992; Marton reflected by the fracture zones imaged by
Salvador, 1991). Although we lean toward and Buffler, 1994; Imbert and Philippe, satellite gravity data. Spreading termina-
the “wide ocean” interpretation, it is 2005; Pindell and Kennan, 2009; Kneller tion probably occurred in the Berriasian
important to note that the alternative COB and Johnson, 2011; Rowan, 2014) we (145.0–139.4 Ma), based on ODP Leg 77
interpretations only influence the crustal favor a two-phase opening model for the boreholes in the Florida Strait (Marton
Gulf of Mexico: and Buffler, 1994). Synchronously with
the counter-clockwise rotation of Yucatan,
complementary clockwise fan-shaped
spreading probably took place in the proto-
Caribbean (e.g., Pindell and Kennan, 2009).

The Tehuantepec transform in western
Gulf of Mexico (Figs. 2 and 3B) marks the
terminal shear to Gulf of Mexico rotational
opening, and forms a classic sharp transi-
tion between continental and oceanic crust
(Román Ramos et al., 2009). Straddling
the transform is a thick Cenozoic apron,
deformed at the updip end by the Neogene
Quetzalcoatl extensional system, which is
linked via detachments with the contrac-
tional Mexican Ridges fold and thrust belt
(e.g., Salomón-Mora et al., 2009).

Regardless of preferred fit and timing,
it is clear from refraction surveys that the

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