Caribbean Microplates
Between the southern boundary of the North American plate and the northern boundary of the Caribbean plate lays a collection of microplates with extensive and interesting tectonic activity. Four microplates are defined in this region, the largest of which being the Gonâve microplate. The next largest plate is the Puerto Rico Virgin Islands microplate. Two smaller microplates are also defined: the South Jamaica and North Hispaniola microplates. Geologic, geodetic and seismic observations were used to define these plates (Benford et al., 2012).
Between the southern boundary of the North American plate and the northern boundary of the Caribbean plate lays a collection of microplates with extensive and interesting tectonic activity. Four microplates are defined in this region, the largest of which being the Gonâve microplate. The next largest plate is the Puerto Rico Virgin Islands microplate. Two smaller microplates are also defined: the South Jamaica and North Hispaniola microplates. Geologic, geodetic and seismic observations were used to define these plates (Benford et al., 2012).
Caribbean tectonic environment (Benford et al., 2012).
A dominant feature in this system is the Cayman Spreading Center (CSC). This center has an extremely slow spreading rate and has been active since the Eocene (Mann et al., 1994). Newer data uses magnetic anomalies and seafloor age and depth profiles to estimate a slightly faster spreading rate of 8mm/yr (Benford et al., 2012).
The Gonâve microplate and its boundaries
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Gonâve Microplate
The Gonâve microplate is the largest of the four defined microplates in the Caribbean. It is bounded by the Cayman Spreading Center on the west, where it experiences extension. The microplate extends east until Hispaniola Island where it undergoes convergence in central Hispaniola. Left-lateral strike-slip faulting occurs along both the Northern and Southern boundaries of the Gondâve microplate. The Northern boundary of this micro plate is made up of the Oriente Fault Zone, where left-lateral strike slip is dominant at 14.2-14.5 mm/yr (Benford et al., 2012), and the Septentrional fault zone. Earthquake data the Septentrional fault zone shows some obliquely convergent motion (DeMets and Wiggins-Grandison, 2006, Benford et al., 2012). The southern boundary of the Gonâve microplate includes left-lateral strike-slip faulting along the Enriquillo-Plantain Garden fault zone (Mann et al., 2008). |
The island of Hispaniola is mainly comprised of Cretaceous to Tertiary volcanic rocks (Perfit, 1980). However, on the northern half of the island, a set of paired metamorphic belts of Cretaceous age indicate convergence at that time. Blueschist and greenschist facies rocks were likely formed during rapid subduction of the Caribbean Plate below the North American Plate (Nagle, 1974). Following this subduction event, the Gonâve microplate is believed to have been sheared off the Caribbean plate and is expected to accrete onto the North American plate (Mann et al., 1994).
Puerto Rico-Virgin Islands (PRVI) Microplate
The PRVI microplate is located at the eastern end of the Caribbean microplate zone and is the second largest of the four defined microplates in this region. The Virgin Islands, which sit on this plate, are mainly comprised of volcanic and sedimentary rocks with some evidence of tuffaceous limestone and spillite and volcanic breccia on the islands of St. John and St. Thomas (Perfit, 1980). GPS data has been used to determine that the PRVI microplate exists as a distinct microplate that moves with a rate of approximately 2.6mm/year at about N82W with respect to the Caribbean plate. The Puerto Rico Trench and the Muertos Trough define its northern and southern boundaries, respectively, both of which are east-west striking. Oblique convergence along the western Puerto Rico Trench is evident based on GPS data and geologic data (Jansma and Mattioli, 2005). At great depths in this trench, marble, greenschist, amphibolite and other metamorphic rocks are found (Perfit, 1980). |
Morphology of Puerto Rico and its surroundings (USGS)
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The PRVI microplate is bounded to the west by the Mona Passage (Jansma and Mattioli, 2005) where igneous rocks, volcanic breccias and limestones are present, sometimes appearing to be weakly metamorphosed (Perfit, 1980). At this western boundary, east-west extension dominates, particularly at the Mona Rift. This extension has been occurring over the last few million years (Jansma and Mattioli, 2005). The Eastern boundary of this microplate is the Anegada Passage. This boundary is also dominated by east-west extension, confirmed by earthquake and bathymetric analysis (Masson and Scanlon, 1991). It is of note that extension likely does not occur simply in the offshore regions of this plate, but also occurs across the island of Puerto Rico (Jansma and Mattioli, 2005).
South Jamaica Microplate
The South Jamaican microplate is one of the two smaller microplates defined in the Caribbean tectonic region. The island of Jamaica lies on the boundary between the Gondâve microplate and the South Jamaican microplate and is an uplifted region of the Nicaraguan Rise. Tertiary limestones and Cretaceous volcanic rocks are exposed at the surface of Jamaica with body wave travel times indicating a carbonate crust of 4-5km thick and an 8 km thick lower layer with wave velocities indicating a composition between oceanic and continental. A thick intermediate layer displays wave velocities indicating a composition of non-continental crust. Deformation in this region is accommodated by multiple E-W and NNW striking fault systems such as the Plantain Garden, Duanevale and Santa Cruz faults. Seismic hazard in this area can be hard to predict, because of the large number of fault systems, however it has been calculated that the Plantain Garden fault could release a M7.2-M7.5 earthquake (DeMets and Wiggins-Grandison, 2006).
The South Jamaican microplate is one of the two smaller microplates defined in the Caribbean tectonic region. The island of Jamaica lies on the boundary between the Gondâve microplate and the South Jamaican microplate and is an uplifted region of the Nicaraguan Rise. Tertiary limestones and Cretaceous volcanic rocks are exposed at the surface of Jamaica with body wave travel times indicating a carbonate crust of 4-5km thick and an 8 km thick lower layer with wave velocities indicating a composition between oceanic and continental. A thick intermediate layer displays wave velocities indicating a composition of non-continental crust. Deformation in this region is accommodated by multiple E-W and NNW striking fault systems such as the Plantain Garden, Duanevale and Santa Cruz faults. Seismic hazard in this area can be hard to predict, because of the large number of fault systems, however it has been calculated that the Plantain Garden fault could release a M7.2-M7.5 earthquake (DeMets and Wiggins-Grandison, 2006).
References Cited:
Benford, B., DeMets, C., Calais, E. (2012). GPS estimates of microplate motions, northern Caribbean: evidence for a Hispaniola microplate and implications for earthquake hazard. Geophysical Journal International, 191(2), 481-490
Calais, E., Freed, A., Mattioli, Amelung, F., Jónsson, S., Jansma, P., Hong, S., Dixon, T., Prépetit, C., Momplaisir, R. (2010). Transpressional rupture of an unmapped fault during the 2010 Haiti earthquake. Nature Geoscience, 3, 794-799
DeMets, C., Wiggins-Grandison, M. (2006). Deformation of Jamaica and motion of the Gonâve microplate from GPS and seismic data. Geophysics Journal International, 168(1), 362-378
Jansma, P., Mattioli, G. (2005). GPS Results from Puerto Rico and the Virgin Islands: Constraints on tectonic settings and rates of active faulting. Active Tectonics and Seismic Hazards of Puerto Rico, the Virgin Islands, and Offshore Areas, Special Paper 385, 13-30
Mann, P., Taylor, F., Edwards, L., Ku, T. (1994). Actively evolving microplate formation by oblique collision and sideways motion along strike-slip faults: An example from the northeastern Caribbean plate margin. Tecnophysics, 246(1-3), 1-69
Mann, P., Prentice, C., King, W., DeMets, C., Wiggins, M., Benford, B. (2008). Late Quaternary Activity and Seismogenic Potential of the Gonâve Microplate: Plantain Garden Strike-Slip Fault Zone of Eastern Jamaica. American Geophysical Union, Fall Meeting 2008, abstract #T11B-1869
Masson, D., Scanlon, K. (1991). The Neotectonic Setting of Puerto Rico. Geological Society of America Bulletin, 103(1), 144-154
Nagle, F. (1974). Bluechist, Eclogite, Paired Metamorphic Belts, and the Early Tectonic History of Hispaniola. Geological Society of America Bulletin, 85(9), 1461-1466
Perfit, M. R., Heezen, B. C., Rawson, M., Donnely, T.W. (1980) Chemistry, Origin and Tectonic Significance of Metamorphic Rocks From the Puerto Rico Trench. Marine Geology, 34(3-4), 125-156
Benford, B., DeMets, C., Calais, E. (2012). GPS estimates of microplate motions, northern Caribbean: evidence for a Hispaniola microplate and implications for earthquake hazard. Geophysical Journal International, 191(2), 481-490
Calais, E., Freed, A., Mattioli, Amelung, F., Jónsson, S., Jansma, P., Hong, S., Dixon, T., Prépetit, C., Momplaisir, R. (2010). Transpressional rupture of an unmapped fault during the 2010 Haiti earthquake. Nature Geoscience, 3, 794-799
DeMets, C., Wiggins-Grandison, M. (2006). Deformation of Jamaica and motion of the Gonâve microplate from GPS and seismic data. Geophysics Journal International, 168(1), 362-378
Jansma, P., Mattioli, G. (2005). GPS Results from Puerto Rico and the Virgin Islands: Constraints on tectonic settings and rates of active faulting. Active Tectonics and Seismic Hazards of Puerto Rico, the Virgin Islands, and Offshore Areas, Special Paper 385, 13-30
Mann, P., Taylor, F., Edwards, L., Ku, T. (1994). Actively evolving microplate formation by oblique collision and sideways motion along strike-slip faults: An example from the northeastern Caribbean plate margin. Tecnophysics, 246(1-3), 1-69
Mann, P., Prentice, C., King, W., DeMets, C., Wiggins, M., Benford, B. (2008). Late Quaternary Activity and Seismogenic Potential of the Gonâve Microplate: Plantain Garden Strike-Slip Fault Zone of Eastern Jamaica. American Geophysical Union, Fall Meeting 2008, abstract #T11B-1869
Masson, D., Scanlon, K. (1991). The Neotectonic Setting of Puerto Rico. Geological Society of America Bulletin, 103(1), 144-154
Nagle, F. (1974). Bluechist, Eclogite, Paired Metamorphic Belts, and the Early Tectonic History of Hispaniola. Geological Society of America Bulletin, 85(9), 1461-1466
Perfit, M. R., Heezen, B. C., Rawson, M., Donnely, T.W. (1980) Chemistry, Origin and Tectonic Significance of Metamorphic Rocks From the Puerto Rico Trench. Marine Geology, 34(3-4), 125-156