Low Amplitude Marine Magnetic Anomalies in the Venezuela and Northern Colombia Basins and Plate Tectonics Implications.
Abstract
For many years, several authors noted the difficulty of interpreting magnetic anomalies within the Caribbean plate. Aside of the magnetic isochrons identified in the Colombia Basin (Christofferson, 1973) and along the Cayman Ridge (e.g., Leroy et al., 2000), seafloor spreading structures in the Caribbean plate remain unrevealed. In the Venezuela basin, some authors tentatively identified magnetic lineations, although the anomalies are hardly discernible (Donnelly, 1973; Ghosh et al., 1984; Orihuela et al., 2013). The origin and age of the Caribbean plate and the Caribbean Large Igneous Provinces (CLIP) that overlay it is a subject still under debate (e.g. Giunta et al., 1997; Kerr et al., 1999; Meschede and Frisch, 1998; Pindell, 1991). The crust of the Colombia and Venezuela basins is presumably oceanic. Two types of crust have been reported in the Venezuela Basin: a fragment of crust resembling normal oceanic crust in its southern part and anomalously thick oceanic plateau basalt (17-20 km) composed of extensive basaltic sills and flows and characterized by deeper mantle in the rest of the basin (Diebold et al., 1981). The map build from our recent compilation of marine magnetic anomalies allows us to interpret magnetic anomalies in two large parts of the Caribbean plate, namely the Colombia and Venezuela basins, from which we propose a model for the origin and age of the Caribbean plate and the CLIP.
In the Colombia Basin we identify a sequence of strong magnetic anomalies in the South and a smooth magnetic zone extending to the North. We interpret the anomalies as Chrons 33 and 33r and the smooth magnetic zone as the youngest part of the Cretaceous Normal Superchron (CNS). In the Venezuela Basin we identify a major N-S fracture zone on both the gravity and magnetic data. A consistent pattern of anomalies in the Central part of the basin is interpreted as the intermediate part of the CNS, whereas a smooth area in the southern part of the basin may correspond to its younger part. These observations, therefore, argue in favour of a Pacific origin of the Colombia Basin, formed 70-91 million years ago, and the basin of Venezuela formed 91-108 million years ago. The two basins would have formed at ridge axis separating the plates Pacific and Farallón. Our results suggest that the CLIP created at the same time as the Caribbean plate. Hypothetically, the two basins separated during the "tightening" of the North and South American plates, the compressive zone of the Beata Ridge constituting the border, perhaps currently still active.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.T31D0282G
- Keywords:
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- 8104 Continental margins: convergent;
- TECTONOPHYSICS;
- 8150 Plate boundary: general;
- TECTONOPHYSICS;
- 8170 Subduction zone processes;
- TECTONOPHYSICS;
- 8178 Tectonics and magmatism;
- TECTONOPHYSICS