History of geological requirements for the CCW rotational opening of the Gulf of Mexico and the Pacific Origin of the Caribbean oceanic crust and Arc System

Abstract

As geological understanding of the Gulf of Mexico and Caribbean progressed through the 20th Century, the Caribbean region began to be recognised as being fundamentally different to the circum-Gulf and circum-Caribbean continental margins. Post-war (WWII) onshore (geological mapping, petrology, sedimentology, stratigraphy, volcanology, biostratigraphy) and offshore (gravity, magnetics, seismic reflection and refraction) research, along with early compilations of seismicity, began to recognise the mainly magmatic basements and histories of the islands, as well as the oceanic character of the interior Caribbean crust (numerous papers by Ewing, Hess, Officer, and colleagues). As early as 1953, the Caribbean was known to be “mobile” with respect to its American neighbours (Hess and Maxwell, 1953). With the advent of plate tectonics in the 1960s, this different “Caribbean geology” came into focus. The islands were recognised as island arcs formed by subduction, the Caribbean interior basement was recognised as a thick form of oceanic crust, and the Caribbean as a whole was soon being compared to western Pacific geology, with its arcs, oceanic plateaux, trenches and contractile accretionary prisms. In 1969, Molnar and Sykes used seismicity to define the “Caribbean Plate” as an entity unto itself, a profound step forward that led some workers to begin searching for explanations as to how the entire Caribbean did not fit in the recently released Bullard et al. (1965) circum-Atlantic continental reconstruction. In the 1970s, many largely ad-hoc plate tectonic models were proposed for the Caribbean and the Gulf of Mexico, trying to assimilate the various implications of the region’s arcs, sutures, basins, and accretionary prisms. Some of these began to recognise the likelihood of a Pacific origin for the Caribbean arcs and crust (e.g., Wilson, 1966; Dietz and Holden, 1970; Malfait and Dinkelman, 1972; Ladd, 1976). However, in the absence of an accurate quantitative circum-Atlantic plate kinematic framework, all these models had inherent problems, and a unified Caribbean evolutionary model remained elusive. Through all of this, the Caribbean’s apparent tectonic complexity confounded realistic and reliable exploration models for the region. In 1981, Bill Haxby of Lamont Doherty Geological Observatory began to produce the first maps of global ocean structure from inversion of late 1970s-1980s Seasat and Geosat satellite altimetry data. As a student at Lamont’s “geological sister school” SUNY Albany, I picked the Central and South Atlantic fracture zones from the raw altimetry data with Steve Cande and Walter Pitman and deduced a drastically different framework of relative motion history between North and South America (Pindell and Dewey, 1982; Pindell et al. 1988), which effectively stands today. This new framework tightened the Permo-Triassic relationship between the Americas by 700 km (!) relative to Bullard’s fit, and (1) required an entirely new class of opening model for the Gulf of Mexico, and (2) that none of the Caribbean region could have been situated between the Americas. The tighter fit required that the Yucat·n Block be rotated by about 50 degrees CW in the Permo-Triassic reconstruction, which, in turn, provided the key to the correct model for the Gulf’s evolution, one of CCW rotational seafloor spreading and dextral, curvilinear transform motion of SW Yucat·n along eastern Mexico (Pindell and Dewey, 1982; Pindell, 1985a,b; Pindell and Kennan, 2001; 2009). The predicted rotational seafloor fabric is now directly observed in both gravity (Sandwell et al. 2014) and aeromagnetic data (Pindell et al., 2016), the latter of which indicates that the pole of rotation jumped at least twice during the opening of the Gulf of Mexico. The fan-like opening for the Gulf had to be complemented by a similar rotational opening between eastern Yucat·n and northern South America, in an ocean that I called the “Proto-Caribbean Seaway”. There, rifting began on the 070∞ trend (today’s coordinates) that defines the rift orientation of the Venezuela-Trinidad margin, but due to the rotation of Yucat·n, the eastern Yucat·n margin had acquired an 020∞ trend by Early Cretaceous time. Concurrent with the rotational Gulf and Proto-Caribbean opening was the formation of the Bahamas carbonate platform, which required a “basement foundation” at sea level in order for reef and carbonate platform development to begin. The relative contribution of thinned continental crust vs hot-spot volcanic rock forming the Bahamian basement is still debated, but the platform’s parallelism with Central Atlantic fracture zones shows that the archipelago owes its origin to Central Atlantic rather than to the rotational early Proto-Caribbean plate kinematics. In addition, the lack of space for the continental nucleus of the Chortis Block (northern Central America) between the Americas in the new framework meant that it must have been situated on the “outside” of Mexico’s pre-Mesozoic continental crust, presumably along southern Mexico which we now know has lithological correlatability. From the above, the early Proto-Caribbean Seaway and its three bounding passive margins (eastern Yucat·n, northern South America and southern Bahamas) was entirely extensional and had a rather small, triangular geometry (Pindell, 1985a,b; Pindell and Erikson, 1994; Pindell and Kennan, 2001). However, once seafloor spreading had ceased in the Gulf of Mexico, probably in the Berriasian (~140 Ma), all subsequent separation between the Americas took place within the Proto-Caribbean only, such that by the Late Cretaceous it was a formidable ocean exceeding 1,500 km in width. These margins, and presumably the Proto-Caribbean crust between them, were sites of good Mesozoic source rock deposition. Although the largely Jurassic Proto-Caribbean passive margins had formed prior to much of the known “Caribbean” geology, the Proto-Caribbean Seaway had remained far too narrow to accommodate the Caribbean Plate and its island arcs until the Late Cretaceous. Supported by a large range of geological reasons, noted below, the new Atlantic opening history made it quite clear that the Caribbean Plate must have originated in the Pacific in the Early Cretaceous. Data from the Gulf and Caribbean’s crust, island arcs, subduction zone sutures, sedimentary basins, and important fault zones were compiled and synthesised, resulting in an internally consistent “Pacific origin” model for Caribbean evolution (Pindell, 1985a,b; Pindell et al., 1988; Pindell and Barrett, 1990). The model held and continues to hold that a swath of oceanic plateau-dominated lithosphere of the Farallon Plate, led by the Cretaceous Caribbean island arcs, migrated into the widening Proto-Caribbean Seaway, subducting the Proto-Caribbean lithosphere as it came. The leading arcs and their oceanic forearcs collided obliquely and diachronously with the Proto-Caribbean passive continental margins, forming the eastward-younging circum-Caribbean suture and foreland basins above the older Proto-Caribbean passive margin sedimentary sections. These include the Maastrichtian “Sepur Basin” in northern Guatemala; the Early and Middle Eocene “Cuban Basin” in the Florida Straits; the Early and Middle Eocene “Misoa-Trujillo Basin” in Maracaibo; the Late Eocene-Oligocene “La Pascua-Roblecito Basin” in central Venezuela; the Late Oligocene-Middle Miocene “Los Jabillos-Carapita Basin” in Eastern Venezuela; and the Late Oligocene-Middle Miocene “Cipero-Naricual-Brasso Basin” in Trinidad (Pindell et al., 1988; Pindell et al., 1991). This eastward-younging progression records an average Caribbean-American displacement rate of about 20 mm/yr since the Maastrichtian. In addition, two intra-arc basins formed within the leading Caribbean arcs during this migration, the Yucat.n and the Grenada/Tobago Trough basins. Both played important roles as the Caribbean Plate accommodated the pre-existing shape of the Proto-Caribbean Seaway, by allowing the arcs to expand under extension until they encountered (collided with) a Proto-Caribbean margin. A third intra-Caribbean basin within the original plate is the Eocene and younger Cayman Trough, which has recorded some 1100 km of displacement between the Caribbean Plate and the Americas over that time. This displacement is also recorded by the Lesser Antilles arc magmatism since the Middle Eocene. This 1980’s synthesis provided straightforward explanations for the vast majority of Caribbean geological relationships, such as the following seven arguments that were used to support the Pacific origin: 1) eastern Caribbean arc magmatism (Aves Ridge and Lesser Antilles) spans back to ~mid-Cretaceous time, apparently recording more or less continuous west-dipping subduction, and hence significant plate displacement over some 80 m.y. (Neill et al., 2011); 2) the overwhelming likelihood that the Cayman Trough is an 1100 km long pull-apart type oceanic basin that recorded relative plate migration back to the Eocene (Rosencrantz et al., 1988; Leroy et al., 2000); 3) the realisation that the circum-Caribbean suture belt separates distinct stratigraphic suites that can be labelled “Caribbean” (magmatic arcs and the tuff-bearing plate interior) and “Proto-Caribbean” (magma- and tuff-free American passive margins), but that could not have co-evolved in proximity to one-another (Pindell, 1990); 4) the fact that the Aptian size of the Proto-Caribbean Seaway between the Bahamas, Yucat.n and Venezuelan passive margins was so small that the known Caribbean terranes of that age could not possibly have fit within it (Pindell and Dewey, 1982; Pindell, 1985a; Pindell and Barrett, 1990); 5) the truncation of southern Mexico and eastward inception of Cenozoic arc magmatism, both as a function of the removal and eastward migration of the Chortis Block as a Caribbean element since the Campanian-Maastrichtian (Pindell and Dewey, 1982; Johnson and Barros, 1993; Ferrari et al., 1999, 2014); 6) studies of faunal provinciality, which show that early Caribbean deposits were non-Tethyan and of cold water type (Boreal), some as old as Middle Jurassic which likely pre-dates oceanic conditions in the gap between the Americas (Montgomery et al., 1994a,b); 7) the observation that the foredeep basins recording arc-continent collision between Caribbean arcs and Proto-Caribbean passive margins young eastward at about 20 mm/yr since the Late Cretaceous, recording the relative migration of the Caribbean Plate between the Americas from the Pacific (Dewey and Pindell, 1985; Pindell et al., 1988; Pindell, 1991). Since the 1980’s, enormous progress has been made for Caribbean geology in general, but also in terms of further strengthening the case for the Pacific origin. The strengthening stems from improved data sets allowing more confident positions on traditional arguments such as those above, and also from entirely new types of geological research altogether. The latter include: 1) determinations of P-T-t history paths for HP-LT rocks from various former Caribbean suture zones that show subduction initiation in the Caribbean arcs by 120 Ma (e.g., Garcia-Casco et al., 2006; Smith et al., 1999; Sisson et al., 2005; St.ckhert et al., 1995; Maresch et al., 2009), which could only have been in the Pacific because the gap between the Americas was tiny and entirely extensional at that time; 2) greatly improved U-Pb dating (over early K-Ar studies) of Caribbean arc magmatic histories, also dating subduction and plate migration from 115-133 Ma (e.g., Rojas-Agramonte et al., 2011; Stanek et al., 2009; Lidiak et al., 2008; Kesler et al., 2005; Grafe et al; 2001); when there was little space between the Americas; 3) mantle seismic tomography showing thousands of km of subducted Atlantic and Pacific (Cocos, Farallon, and Nazca) beneath the Caribbean (Levander et al., 2014; Bezada et al., 2010; Van Bentham, 2013; van Bentham et al., 2013); 4) zircon dating and heavy-mineral clastic provenance studies which help to constrain the times of diachronous arc-continent collisions around the Caribbean (Rojas et al., 2008; Pindell et al., 2009b; Wright and Wyld, 2011); 5) absolute plate motion studies that show the Caribbean Plate to be fixed in the mantle reference frame while the American plates drift westward at 20 mm/yr (van der Meer, et al., 2010; Doubrovine et al., 2012); 6) newly-released gravity and aeromagnetic data sets that clearly document the CCW rotation of Yucat.n (Sandwell et al., 2014; Pindell et al; 2016); 7) a growing body of high-quality seismic reflection records that tell us more about the subsurface, such as the character of the Caribbean igneous oceanic plateau crust (Kolla et al., 1984; Mauffret and Leroy, 1997; Driscoll and Diebold, 1999; Diebold and Driscoll, 1999). Conversely, I do not know of a single argument that makes me question the Pacific origin. In this talk, I will review all these arguments, and then show how Pacific origin models do the best job of explaining the diverse and growing data sets that must be accommodated by models of Caribbean evolution. I will use the maps of Pindell and Kennan (2009) as an internally-consistent example of the Pacific origin model, as they were made when much of this information was known. However, I would not wish to convey the idea that everything is understood. Time permitting, I will outline some of the more outstanding problems facing continued progress in our understanding of the Gulf of Mexico and Caribbean.

AAPG Datapages/Search and Discovery Article #90330©2018 AAPG Hedberg: Geology of Middle America – the Gulf of Mexico, Yucatan, Caribbean, Grenada and Tobago Basins and Their Margins “Integration of the geology of the area from the southern onshore of North America to the northern onshore of South America”, Siguenza, Guadalajara, Spain, July 2-5, 2018