Structure, age, and origin of the Caribbean Plate unraveled
Introduction
The Caribbean plate is a small tectonic plate trapped between two major continental plates, the North and South American plates, and two major subduction zones. The oceanic lithosphere of the Atlantic and Pacific oceans subducts beneath the Caribbean plate at its eastern and western ends, respectively. At its northern and southern ends, the Caribbean plate is bounded by two large transform systems which accommodate its eastward motion with respect to the North and South American plates. Its core is made of the Caribbean Large Igneous Province (CLIP) resulting from extensive volcanism in the Cretaceous. Fragments of the CLIP are found all around the Caribbean islands. The CLIP includes the thickened oceanic crust of the Colombia Basin and most of the Venezuela Basin (e.g., Diebold et al., 1981).
Different models have been proposed for the origin of the Caribbean plate, either formed in situ (e.g., Meschede and Frisch, 1998) or transferred from the Pacific Ocean to its present location (e.g., Pindell, 1990). Therefore, many questions remain on the structure and age of the plate. The main reason for these uncertainties is that no clear magnetic anomaly is observed in most of the Caribbean plate. This is partly because the plate is located at low latitude, but also because it was probably formed during the Cretaceous Normal Superchron (CNS). The CNS is a 35 to 40 million years-long episode of stable normal geomagnetic polarity between 83 and ∼120 Ma: the lack of geomagnetic reversals results in the absence of the typical lineated seafloor spreading anomalies used to date the seafloor. The sequence of anomalies 18 to 1 (46-0 Ma) has been identified on both flanks of the Cayman Ridge, the only active spreading center bounding the Caribbean plate (Leroy et al., 2000). The oceanic crust of the Colombia and Venezuela basins display set of anomalies interpreted as anomalies 27-33 (70-83 Ma) in the central and southern Colombia Basin (Christofferson, 1973). Several attempts to recognize lineated anomalies in the Venezuela Basin led to contradictory interpretations due to the low amplitude of the signal and the paucity of data (Donnelly, 1973; Ghosh et al., 1984; Orihuela Guevara et al., 2013).
Here we take advantage of our new marine magnetic anomaly map of the Caribbean Plate (Garcia-Reyes, 2018) together with recent results obtained from the detailed analysis of the CNS in other oceanic basins to reinvestigate the structure, age, and origin of the Caribbean plate.
Section snippets
Methods
We gathered total marine magnetic field measurements from the National Centers for Environmental Information (NCEI) and French Research Institute for Exploitation of the Sea (IFREMER). After removing spurious data, excluding noisy tracks and performing quality control over navigation and acquisition time along marine tracks, we subtracted models of the internal geomagnetic field (CM4, Sabaka et al., 2004 for the period 1960-2002.5; IGRF-11, Thébault et al., 2015 for other periods) to obtain
Results: seafloor spreading magnetic anomalies in the Caribbean Plate
The main magnetic anomalies displayed in Fig. 1b are related to major structural features such as the Hess Escarpment separating the Lower Nicaragua Rise and the Colombia Basin, the western flank of Beata Ridge, the basement of the Greater Antilles from Hispaniola to Puerto Rico, and the Lesser Antilles volcanic arc, to cite only the most prominent. A complex, hummocky magnetic pattern is observed on the Lower Nicaragua Rise, Aves Ridge, and to a lesser extent Beata Ridge. This pattern likely
A plateau formed at a spreading center
The observation of identifiable magnetic anomalies 33-34 and Q1 as well as the second and third periods of the CNS in the Colombia and Venezuela basins has an important implication. It means that the part of the CLIP making these basins was formed at a spreading center. Although quite a difficult exercise considering the paucity of constraints, we attempted to estimate spreading rates from the identified anomalies. The clear anomaly 33r in the Colombia Basin leads to spreading rate values of 35
Conclusion
In the Colombia Basin, we identify a sequence of strong magnetic anomalies in the South and a smooth magnetic zone extending to the North that we interpret as Chrons 33-34 and the youngest part of the Cretaceous Normal Superchron (CNS), respectively. In the Venezuela Basin, we identify a major N-S fracture zone on both the gravity and magnetic data; a consistent pattern of magnetic anomalies in the central part of the basin is interpreted as the intermediate part of the CNS, whereas a smooth
CRediT authorship contribution statement
AGR and JD conceived the study, which was carried out by AGR as part of her PhD Thesis under the supervision of JD. They jointly wrote the manuscript and prepared the figures.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
AGR thanks Fundayacucho (Venezuela), Campus France, IPGP, Caribbean Basin Tectonics and Hydrocarbon Project of the Stavanger and Houston Universities, Commission of the Geological Map of the World of UNESCO, and the Pause Program of the French Government for their support at various stages of this work. We thank Udo Barckhausen for providing recently acquired N-S trending magnetic profiles in the Colombia Basin in 2016 that helped to validate the quality of our magnetic anomaly map but were not
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