Tectonophysics 590 (2013) 38–51

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Tectonophysics

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Curie point depth in Venezuela and the Eastern Caribbean

Mariano S. Arnaiz-Rodríguez ⁎, Nuris OrihuelaDepartmento de Geofísica, Facultad de Ingeniería, Escuela de Geología, Minas y Geofísica, Universidad Central de Venezuela, Venezuela

⁎ Corresponding author. Tel.: +58 212 481 9006.E-mail addresses: marianoarnaiz@gmail.com, marian

(M.S. Arnaiz-Rodríguez).

0040-1951/$ – see front matter © 2013 Elsevier B.V. Allhttp://dx.doi.org/10.1016/j.tecto.2013.01.004

a b s t r a c t

a r t i c l e i n f o

Article history:Received 6 June 2012Received in revised form 4 January 2013Accepted 8 January 2013Available online 17 January 2013

Keywords:Curie point depthMagnetic anomaliesHeat flowVenezuelaThe Eastern Caribbean

We estimate the Curie point depth (CPD) variations of Venezuela (continental crust, South American plate)and the Eastern Caribbean (oceanic crust, Caribbean Plate) by using spectral analysis of the magnetic anom-alies, extracted from the 2010 Enhanced Magnetic Model (EMM2010), available at the National Oceanic andAtmospheric Administration (NOAA). To test the reliability of the spectral content of this model, for a smallregion, we compare he CPD derived from the EMM2010 against the one from aeromagnetic data. We alsocompile heat flow data from previous studies to correlate them with the CPD lateral variations. The estima-tions show that the CPD in Venezuela and the Eastern Caribbean ranges between 54 and 17 km. The meandepth value within the continental crust is around 38 km. On the Guayana Shield, it has a mean value of42 km and reaches a maximum of 54 km. As the Moho depth is at most 50 km, the upper mantle beneaththe craton is magnetized. Continental lateral variations appear to be linked to the isostatic state and ageof the different provinces, and mark the limit between the Precambrian and the Paleozoic provinces. TheMaracaibo Basin is revealed as a thermally stable one with a constant CPD, while the Eastern Venezuela Basinis thermally affected. Most of the Eastern Caribbean seems stable, with a large non-perturbed area with amean CPD value of 23 km. As the crustal thickness is at most 20 km, the isotherm is located within the uppermantle. A CPDminimum located on the Lesser Antilles arc is concentrated in its northern part, and can be relatedto the subduction zone that is most active. Finally, a shallow area within the Eastern Caribbean correspondsto the thin crust region in the Venezuela Basin, although it might be linked to mantle dynamics.

© 2013 Elsevier B.V. All rights reserved.

1. Introduction

The Curie point (CP) is defined as the temperature at which a mate-rial loses its capability to acquire permanent magnetism. Curie–Weisslaw (Eq. (1)) describes the behavior of the magnetic susceptibility (χ)of a ferromagnetic material as a function of Curie's constant (C) andthe difference between the temperature (T) and the CP temperature(Tc).When T equals Tc, randomness introduced by atomic level thermaleffects causes the material to lose its spontaneous magnetization and,therefore, its induced and remanent magnetism (Kittel, 1996).

χ ¼ C= T−Tcð Þ: ð1Þ

The Curie point depth (CPD) is the depth at which thematerials of theupper lithosphere (usually the lower crust and, in some cases, the uppermost mantle) reach its CP. Although the CP of different minerals rangesfrom 573 °C for quartz, through 585 °C for magnetite, to 770 °C for iron,it is well established that, for the upper lithosphere, it ranges between550 and 580 °C (e.g. Turcotte and Schubert, 2007). The CPD is a variable

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that strongly depends on the thermal regimen of a specific region (heatflow and geothermal gradient), as well as on the thermal properties andmineralogy of the rocks (Wasilewski and Mayhew, 1992; Wasilewskiet al., 1979). Therefore, the lateral variations at the bottom of the mag-netic layer (usually interpreted as the CPD isotherm) can be correlatedeither to differences of physical properties of the lithosphere, or to var-iations of the regional geothermal gradient (Shive et al., 1992).

Considering theMoho depth, two CPD scenarios have been found indifferent geodynamic situations, related to diverse thermal regimens:one in which the CPD isotherm is shallower than the Moho and theother in which it is similar or deeper. In volcanic regions, or areaswith high heat flow, CPD isotherm tends to be shallower than the sur-rounding areas not affected by thermal processes (e.g. Banerjee et al.,1998; Okubo et al., 1989; Stampolidis and Tsokas, 2002) and shallowerthan the Moho depth. In areas where crustal thinning (either thermallyor tectonically driven) has been detected, the CPD is shallower than inthe surrounding terranes (Dolmaz et al., 2005).

In tectonically and isostatically stable areas or those with low heatflow, the CPD isotherm tends to be as deep as the Moho (Wasilewskiand Mayhew, 1992; Wasilewski et al., 1979), or even deeper (Chiozziet al., 2005; Eppelbaum and Pilchin, 2006). This has been particularlyfound in the West African Craton (Toft and Haggerty, 1988) andthe Yangtze Craton (Chang, 2008), both considered isostatic stableterranes with low heat flow (Mooney and Vidale, 2003). Trifonova

39M.S. Arnaiz-Rodríguez, N. Orihuela / Tectonophysics 590 (2013) 38–51

et al. (2009) pointed out that wide CPD variations, in these regionsmight be connected with age and geochemical compositions of tec-tonic provinces.

In subduction zones, the CPD has been correlated with the boundarybetween the brittle and ductile crust regime, which is somehow linkedto 600 °C isotherm (Doser and Kanamori, 1986). This behavior wasreported in Japan (Huang, 1996) and in the northern Argentinian Andes(Ruiz and Introcaso, 2004).

Moreover, in oceanic domain, there is geophysical evidence that thelower crust is magnetic (Dunlop and Prevot, 1982; Harrison, 1976;Harrison and Carle, 1981; Kent et al., 1978), as well as the uppermostmantle (Arkani-Hamed, 1991). Some thermal evolution models of theoceanic lithosphere have predicted that the CPD reaches a depth of30 km, when the lithosphere is about 40 Ma old (e.g. Arkani-Hamedand Strangway, 1986;McKenzie et al., 2005), suggesting that this regionis potentiallymagnetic and thus itmay contribute to the observedmag-netic anomalies (Arkani-Hamed, 1991).

CPD studies cover a wide variety of places all over the world, al-though none has been performed on northern South America or theCaribbean region, based on the analysis of magnetic anomalies. Inspite of Venezuela being one of the largest suppliers of crude oil andpetroleum in the world, little or no attention has been paid to thethermal conditions of its continental basins. Therefore, this papermay contribute to a better understanding of variations of the bottommagnetic layer. Its main objective is to estimate the CPD lateral vari-ations of Venezuela and the Eastern Caribbean through spectral anal-ysis of the magnetic anomalies, derived from the EMM2010, andcorrelate them with heat flow data.

2. Tectonic and thermal setting

The region of study extends from latitude 2°N to 18°N and fromlongitude 60°W to 73°W; it covers most of the Venezuelan territory(including offshore areas), the eastern part of the Caribbean Sea,and the Lesser and Leeward Antilles (Fig. 1). It is a complex zone of3,200,000 km2, where strike slip faulting, compression, thrusting,flexure (at different scales) and type B subduction coexist (Granja,2005; Pindell and Barrett, 1990). An extensive and comprehensivedatabase, including geological, geophysical and geochemical informa-tion, is available. This has been used to study the dynamics of north-ern South America and the evolution of the Caribbean Plate, which isstill a matter of heated discussion (James, 2002).

2.1. Venezuela

The Guayana Shield is the largest, oldest, and relatively most sta-ble tectonic feature in northern South America (Mendoza, 1977).The Shield is divided into four tectonic provinces formed duringmajor orogenic periods (Fig. 1): Imataca, Pastora, Cuchivero and Rorai-ma. Imataca (3–2.8 Ga, Guriense) consists mainly of metasedimentaryrocks, granitic gneiss and granitic intrusions that have been metamor-phosed to anfibolite and granulite facies (Dougan, 1972). Pastora (2.7–2 Ga, Pre-Transamazonic) is primarily composed of metasedimentaryrocks and mafic to felsic volcanics, locally intruded by gabbro anddiabase (Ostos et al., 2005). Cuchivero (1.9–1.4 Ga, Transamazonic) con-sists of metavolcanic, plutonic and metasedimentary rocks (Talukdarand Colvee, 1974), intruded by felsic magmas (Ostos et al., 2005). Rorai-ma (1.8 Ga, Orinociense) is composed of clastic rocks and piroclasticmaterials (Priem et al., 1973; Santos et al., 2003). These Precambrianautochthonous terranes continue northward beneath the more recentsedimentary layers and become the basement rocks for the EasternVenezuela Basin (Feo-Codecido et al., 1984; Yoris and Ostos, 1997).

The Paleozoic terranes, located beneath the Eastern Venezuela Basinand the Barinas Apure basin (Feo-Codecido et al., 1984), were thrustedover the Precambrian Guayana Shield in a series of collisions that tookplace between 0.25 and 0.57 Ga ago. The main structure that divides

the Precambrian and the Paleozoic provinces is the Apure Fault(Feo-Codecido et al., 1984). During the Jurassic, the separation of thePangaea supercontinent produced extensional stress with the forma-tion of grabens, as well as the development of an Atlantic type passivemargin during the Cretaceous (Yoris and Ostos, 1997). During theupper Cretaceous, the Caribbean arc collided with South America andformed the Caribbean nappe system from the Paleocene to the Eocene.Finally, the major recent orogenic event is associated with the collisionof the Baduo-Choco territories and western South America. This eventproduced the uplift of the Perijá Range and the Merida Andes duringthe Late Eocene to the Middle Miocene (Audemard and Audemard,2002).

The quantity well log data to determine heat flow in Venezuela isconsiderably smaller in comparison to the geological information.Fernández (2004) and Hernández (2006) used such data to studythe thermal situation of Venezuela's Eastern Basin and concludedthat the high thermal anomalies (mean of 3.77 μcal cm−2 s−1;Fig. 2) might be an expression of either a crustal thinning or oceanvs continent subduction in central Venezuela. Even though there isno data on the Guayana Shield, its heat flow is expected to be lowerthan the standard for continental crust (1.4 μcal cm−2 s−1 estimatedby Hamza and Muñoz, 1996), as the mantle heat is forced to escapethrough thinner lithospheres rather than the thicker and thermal re-sistant lithosphere beneath the cratons (Nyblade and Pollack, 1993).

2.2. The Eastern Caribbean

The Caribbean Plate is a rather small tectonic plate located be-tween North and South America. Its northern and southern bordersare dominated by strike slip displacement along large fault systems(Audemard et al., 2005; Sisson et al., 2005), while the eastern andwestern borders are standard type B subductions (Bouysse, 1984;Bouysse et al., 1990). The Caribbean Plate itself is a puzzle of smallblocks, thickened crusts and complex structures that are the rem-nants of a complex formation (e.g. James, 2002).

Even though there is no mid-ocean ridge within it, the CaribbeanPlate has been characterized as an oceanic plate, considering itsphysical properties (wave velocities and densities) and crustal thick-ness (e.g. Edgar et al., 1971; Houtz and Ludwig, 1977; Officer et al.,1959). The geochemical composition of its crust includes Mid OceanRidge Basalts (MORB), ocean island basalts (OIB), and island arc tho-leiitic rocks (IAT), all of them closely related to its complex formation(Giunta et al., 2002, 2006; Hastie and Kerr, 2010; Révillon et al., 2000;Sinton et al., 1998; Wright and Wyld, 2010).

The magnetic signature of the MORB, which has magnetic chronscorresponding to late Jurassic to the early Cretaceous time interval, con-firms the oceanic character of the Caribbean formation (Christofferson,1973; Ghosh et al., 1984; Orihuela Guevara et al., 2012). The OIB reflectrare earth elements, incompatible multi-elements, and isotopic rela-tionships that confirm the existence of plume activity in the region atleast from 90 to 76 Ma (Hastie and Kerr, 2010; Révillon et al., 2000;Sinton et al., 1998; Wright and Wyld, 2010).

The most remarkable feature of the Caribbean is the presence of thelarge igneous province of the Caribbean (CLIP), which has been consid-ered responsible for the unusual crustal thickness (15 to 20 km) of theCaribbean plate (Edgar et al., 1971; Houtz and Ludwig, 1977; Ladd andWatkins, 1980; Officer et al., 1959). The formation of this igneous prov-ince has been associated with the activity of the Galapagos hot spot(Pindell and Barrett, 1990) or to an “intra-Caribbean superplumeevent” (Cox, 1991; Larson, 1991). Either way, the thickening related tothe CLIP confers buoyancy to the Caribbean plate making it difficult tobe subducted when in contact with other plates (Burke, 1988; Duncanand Hargreaves, 1984; Mauffret and Leroy, 1997).

Regarding the thermal situation of the Eastern Caribbean, Epp et al.(1970) describe the region as a thermally stable oceanic crust withmean heat flow around 1.35 μcal cm−2 s−1, similar to the average

Fig. 1.Major tectonic features in Venezuela and the Easter Caribbean. On the lower left corner the location of the study area at regional scale is shown. Red stars represent the activevolcanoes in the Lesser Antilles Arc (Bouysse et al., 1990). P–P′ represents the profile in Fig. 7. CMR stands for Caribbean Mountain Range.

40 M.S. Arnaiz-Rodríguez, N. Orihuela / Tectonophysics 590 (2013) 38–51

value for world ocean basins reported in 1.3 μcal cm−2 s−1 (Langsethand Von Herzen, 1970) (Fig. 2). Clark et al. (1978) define two highheat flow anomalies: one coincident within the active Lesser Antillesarc (4.84 μcal cm−2 s−1) and the other with the Aves Ridge(5.26 μcal cm−2 s−1) (Fig. 2). The front of the overthrusting margin of

the Lesser Antilles has a relatively low thermal gradient, as usuallyreported in other similar margins (Clark et al., 1978; Schubert andPeter, 1974). Davis and Hussong (1983) interpret high heat flow valuesnear the Caribbean–Atlantic deformation front as upward migration ofwarm water from greater depths, extreme overpressures maintained

Fig. 2. Heat flow map for Northern Venezuela and the eastern Caribbean, contours every 1 μcal cm−2 s−1. White diamonds show the location of the available data; red stars rep-resent the active volcanoes in the Lesser Antilles Arc (Bouysse et al., 1990). Most of the Eastern Caribbean shows values around 1.3 μcal cm−2 s−1, higher values of heat flow areassociated with the Lesser Antilles Arc and the Aves Ridge. In Northern Venezuela a high heat flow is found in the Guarico sub-basin. P–P′ represents the profile in Fig. 7. Sometectonic features are shown. CMR stands for Caribbean Mountain Range.

41M.S. Arnaiz-Rodríguez, N. Orihuela / Tectonophysics 590 (2013) 38–51

by tectonic compression during subduction and formation of theaccretionary trench slope.

3. Methodology

3.1. The data

The magnetic data was extracted from the Enhanced MagneticModel 2010 — EMM2010 (Maus, 2010a, 2010b), which is available attheNational Geophysical Data Center (NGDC). Thismodel compiled dif-ferent databases into one grid, 5 km above the WGS84 geoid. The lon-gest wavelength component was derived from data of the CHAMPsatellite (MF6 model), which possessed enough information of thespherical harmonics of the geomagnetic field to resolve the anomaliesup to 333 km in wavelength. This measurement corresponded to thecortical and lithospheric field. Marine, aeromagnetic and ground datawere combined to another common grid (EMAG2). To build theEMM2010, the previous databasesweremerged by spectral techniques,replacing the wavelengths longer than 330 km on the EMAG2 for thoseof theMF6 (Maus et al., 2009) to avoid problemswhen grouping differ-ent magnetic data sets (Maus, 2010a, 2010b). The spectral content, theresolution, and the spatial coherence of wavelengths larger than 56 kmwere enhanced with the 720-degree spherical harmonics. This calcula-tion allowed the EMM2010 to provide magnetic information with a

15-arcminute resolution over theworld. The short-wavelength compo-nent (resolution for shallow structures)was proportional to the quanti-ty of marine, aeromagnetic and ground data. From the EMM2010 weobtained a total of 32,200 magnetic measurements, which wereemployed for the constructions of the magnetic anomaly map (Fig. 3).

Most of the geothermal data were obtained from the Global HeatFlow Database of the International Heat Flow Commission (Pollack etal., 1993). They were also recovered from Epp et al. (1970), Clark et al.(1978), Hamza and Muñoz (1996), Fernández (2004) and Hernández(2006). These data were unified into work units (μcal cm−2 s−1) as re-ferred by Smith (1975). A total of 180 measurements are shown inTable 1. A heat flow map was created with this information (Fig. 2).

3.2. Is it valid to use the combined EMM2010 model to estimate the Curiepoint depth?

One of the questions regarding the use of the EMM2010 to estimatethe CPD is interrelated to the nature of the data themselves. TheEMM2010 is based on numerically and statistically validated grids thatcompile different databases (Maus et al., 2009), where resolution is pro-portional to the amount of available marine, aeromagnetic, or grounddata. This coverage ensureshigh resolutionof the EMM2010 inVenezuelaand the Eastern Caribbean (see complementary data for the extensivecoverage of the region).

Fig. 3. Magnetic anomaly map derived from the EMM2010. Anomalies were calculated at 3 km over sea level in the year 2010.00. The most important anomalies in the map arerelated to the Eastern Venezuela basin and the Imataca Province. Some tectonic features are shown. P–P′ represents the profile on Fig. 7. Some tectonic features are shown. CMRstands for Caribbean Mountain Range. A to G annotations refer to particular continental magnetic anomalies used in the interpretations of the CPD.

42 M.S. Arnaiz-Rodríguez, N. Orihuela / Tectonophysics 590 (2013) 38–51

Probably, the most important concern about this data is the reli-ability of its frequency content which can be altered when the longwavelength is replaced with the CHAMP satellite crustal field model(Maus, 2010a, 2010b). As our estimation of the CPD is based on themethodology proposed by Spector and Grant (1970) (explanation ofthe method in Section 3.3), we compared the CPD estimated fromthe EMM2010 alongside aeromagnetic data (Fig. 4a and c) for a

region in Eastern Venezuela (Mapas de Anomalías Magnéticas deVenezuela, 1989). This test showed that even though the radially av-eraged power spectrum (RApS) was different, the CPD and magneticbasement depth estimated were very similar (Fig. 5b and d).

In addition, Shive et al. (1992) suggests that satellite magnetic sur-veys provide the only globally consistent information about the crustalmagnetization. Moreover, “Mayhew (1985) developed a technique to

Table 1Heat flow values for Northern Venezuela and the Eastern Caribbean in μcal cm−2 s−1, collected from different databases. Sources are: (1) Clark et al. (1978); (2) Epp et al. (1970);(3) Fernández (2004) and Hernández (2006); (4) Pollack (1993).

Longitude Latitude Heat flow (μcal/m2 s) Source Longitude Latitude Heat flow (μcal/m2 s) Source Longitude Latitude Heat flow (μcal/m2 s) Source

−64.51 14.09 1.68 1 −71.79 9.65 1.71 3 −72.22 17.57 2.12 4−64.46 14.1 2.11 1 −71.54 9.11 1.28 3 −75.03 11.92 2.14 4−64.25 14.1 2.14 1 −71.16 9.27 1.3 3 −74.85 12.88 2.14 4−64 14.13 1.93 1 −62.43 11.02 1.05 3 −66.3 12.57 2.15 4−63.54 14.12 2.05 1 −67.21 10.17 1.46 3 −63.15 13.1 2.15 4−63.49 14.12 3.39 1 −74.28 11.75 0.77 4 −74.9 12.07 2.19 4−63.45 14.11 5.78 1 −75.24 12.3 0.81 4 −69.18 15.38 2.2 4−63.02 14.14 4.84 1 −58.4 16.95 0.82 4 −68.77 14.43 2.22 4−62.54 14.13 4.39 1 −74.78 15.85 0.87 4 −64.58 14.03 2.22 4−62.48 14.13 4.67 1 −60.68 12.35 0.91 4 −66.57 20.2 2.24 4−62.41 14.14 3.38 1 −76.33 16.1 0.93 4 −66.2 15.72 2.24 4−62.37 14.11 2.28 1 −76.15 11.88 0.98 4 −74.45 16.13 2.26 4−62.3 14.1 1.42 1 −74.29 16.17 0.99 4 −75.23 19.2 2.27 4−62.2 14.13 1.93 1 −66.29 16.06 1.15 4 −65.18 17.35 2.27 4−62.02 14.15 1.56 1 −70.2 16.16 1.2 4 −65.03 17.12 2.27 4−61.13 14.16 2.45 1 −57.65 16.4 1.22 4 −62.32 14.37 2.27 4−61.02 14.16 3.94 1 −59.97 15.07 1.24 4 −76.72 12.43 2.31 4−60.37 14.14 5.02 1 −60.53 12.02 1.26 4 −71.67 13.68 2.33 4−60.23 14.15 5.54 1 −58.42 14.23 1.26 4 −59.15 16.35 2.33 4−60.14 14.16 2.12 1 −58.32 14.98 1.26 4 −74.88 14 2.34 4−76.2 16.06 0.53 2 −67.37 13.47 1.34 4 −70.75 11.92 2.34 4−70.5 14.38 1.01 2 −64.32 13.38 1.38 4 −67 13.78 2.34 4−76.06 11.12 1.02 2 −75.4 12.5 1.4 4 −59.12 18.05 2.34 4−76.43 12.26 1.04 2 −66.3 12.57 1.4 4 −72.57 14.55 2.4 4−68.33 14.27 1.08 2 −58.88 16.75 1.42 4 −63.83 15 2.4 4−69.18 14.46 1.15 2 −74.48 16.28 1.73 4 −57.75 15.98 2.4 4−72.55 17.08 1.17 2 −58.87 13.48 1.73 4 −64.53 13.63 2.42 4−75.26 12 1.19 2 −74.9 12.07 1.75 4 −71.98 13.6 2.45 4−73.5 14.5 1.2 2 −74 11.81 1.15 4 −64.2 15.97 2.5 4−70.57 14.36 1.2 2 −75.78 11 1.45 4 −63.35 12.22 2.5 4−72.48 16.08 1.21 2 −73.83 14.83 1.75 4 −76.53 14.18 2.52 4−72.13 17.34 1.21 2 −70.95 14.6 1.75 4 −75.87 15.07 2.54 4−66.18 12.34 1.23 2 −76.1 11.2 1.77 4 −65.93 13.55 2.55 4−63.09 13.06 1.23 2 −70.83 14.63 1.77 4 −57.63 16.92 2.57 4−74.54 12.04 1.25 2 −71.43 13.59 1.8 4 −76.95 10.03 2.59 4−69.11 15.23 1.26 2 −65.12 12.52 1.8 4 −73.28 15.38 2.63 4−68.46 14.26 1.27 2 −57.9 16.58 1.8 4 −71.72 13.98 2.63 4−74.27 16.08 1.29 2 −68.4 15.47 1.84 4 −66.42 20.82 2.66 4−75.14 19.12 1.3 2 −57.87 16.57 1.87 4 −66.57 20.23 2.7 4−65.11 17.21 1.3 2 −68.55 14.45 1.89 4 −62.02 14.25 2.73 4−65.02 17.07 1.3 2 −58.47 16.88 1.89 4 −57.4 14.22 2.73 4−74.53 14 1.34 2 −59.05 16.73 1.91 4 −57.1 14.23 2.8 4−70.45 11.55 1.34 2 −72.8 16.13 1.93 4 −71.23 17.03 2.92 4−72.34 14.33 1.37 2 −68.63 13.25 1.93 4 −62.1 12.82 2.92 4−63.21 12.13 1.43 2 −63.15 13.1 1.93 4 −57.63 16.85 2.92 4−76.32 14.11 1.44 2 −58.62 16.3 1.98 4 −76.92 13.2 2.96 4−65.56 13.33 1.46 2 −69.3 14.77 2.01 4 −68.67 16.83 2.96 4−69.46 14.1 1.54 2 −66.48 16.1 2.01 4 −73.28 15.38 3.03 4−71.14 17.02 1.67 2 −65.88 19.83 2.03 4 −67.38 20.37 3.08 4−76.55 13.12 1.69 2 −72.92 17.13 2.05 4 −71.72 13.98 3.15 4−68.4 16.5 1.69 2 −75.43 12 2.08 4 −76.97 12.5 3.26 4−58.28 16.9 1.72 2 −76.53 14.18 2.1 4 −62.33 14.2 3.38 4−73.17 15.23 1.73 2 −73.83 14.83 2.1 4 −62.25 15.03 3.5 4−62.38 12.45 2.08 2 −70.95 14.6 2.1 4 −60.5 15.07 3.5 4−63.5 10 3.27 3 −70.72 15.68 2.1 4 −60.35 13.52 3.61 4−63 9.5 2.34 3 −70.33 16.27 2.1 4 −62.63 12.75 3.64 4−64.2 9.3 3.98 3 −66.48 16.1 2.1 4 −62.35 14.05 3.71 4−66 9.75 4.76 3 −57.72 17.58 2.1 4 −75.8 14.9 3.92 4−67.21 10.17 1.46 3 −59.93 16.63 2.1 4 −71.95 12.89 1.58 4−71.64 10 1.26 3 −72.8 16.13 2.12 4 −72.48 12.4 1.39 4

43M.S. Arnaiz-Rodríguez, N. Orihuela / Tectonophysics 590 (2013) 38–51

estimate the depth to the Curie-temperature isotherm from satellitedata, and found good agreement with isotherms estimated from aero-magnetic data in the Pacific Northwest (Connard et al., 1983)” (Shiveet al., 1992, pp 152). Finally, aeromagnetic data are susceptible to vari-ous sources of errors due to navigational or altimetric mislocation, im-proper regional field removal, and external magnetic fields. Some ofthese errors may appear in magnetic profiles as long-wavelength mag-netic anomalies and, therefore, may have detrimental effects onmodels

of deep crustal sources. Perhaps the most serious long-wavelengtherror can occur in compilations of regional aeromagnetic surveys. If re-gional fields are not removed properly and consistently from individualsurveys, wavelengths, comparable to the dimensions of the surveys,may be generated and unrelated to crustal sources (Shive et al., 1992).This suggests that a well-built and statistically validated model likethe EMM2010 is better at estimating the CPD variations than aero-magnetic data compiled from different sources.

−66˚ −64˚ −62˚ −60˚

10˚

−64˚ −62˚

−500 −400 −300 −200 −100 0 100 200

(a)

(b)

Magnetic Anomalies(nT)

-10

-5

0

5

10

15

2.01.00 3.0 4.0 5.0 6.0

-15

-10

--5

0

5

10

0 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20

CPD = 29.91 ± 0.79 km

Basement Depth = 10.48 ± 0.57 km

Basement Depth = 10.35 ± 0.68 km

log

(Pow

er)

log

(Pow

er) Depth = 28.81 ± 0.93 km

Wavenumber(Radians/km)

Wavenumber(Radians/km)

(d)

(c)

−66˚ −60˚

10˚

Fig. 4. Comparison between the aeromagnetic anomaly map (500 m over sea level) and the EMM2010 (4 km over sea level), and between the radially average power spectrums foreach window. The aeromagnetic anomaly map (a) shows the magnetic signature of different structures at different depth, while the EMM2010 magnetic anomaly map (b) showsthe magnetic response of the deepest and largest crustal structures. Both spectrums are very different, although the estimation of the CPD and basement depth for the aeromagneticanomaly map (c) is very similar to the one from the EMM2010 magnetic anomaly map (d). For the EMM2010, the CPD estimated is 28.81±0.85 km; for the aeromagnetic data, is29.90±0.79 km. For the magnetic basement, the depth estimated from the EMM2010 is 10.35±0.68 km, while the one estimated from the aeromagnetic data is 10.48±0.57 km.These values imply that for a well-covered region the EMM2010 can be used to estimate the CPD.

44 M.S. Arnaiz-Rodríguez, N. Orihuela / Tectonophysics 590 (2013) 38–51

3.3. Estimating the Curie point depth

Because magnetic anomalies hold information of the location andcharacteristics of magnetic bodies, they can be used to determine theCPD for an area large enough to contain the wavelength componentof the deepest magnetic source (Lowes, 2007). The radially averagedpower spectrum (RApS) allows an adequate estimate of the depth ofthe source represented as a large number of independent rectangularparallelepipeds (Spector and Grant, 1970). This estimation is basedon one of the most common methodologies for calculating thedepth of different magnetic sources (e.g. Selim and Aboud, 2012;Spector and Grant, 1970) and has been extensively employed to esti-mate the CPD (e.g. Blakely, 1988; Connard et al., 1983; Nwankwo etal., 2009; Onwuemesi, 1997; Shuey et al., 1977). The methodologyhas the advantage of being simple to apply, replicable, relatively accu-rate and yielding geological coherent information.

In order to calculate the magnetic anomalies (MA) and build themagnetic anomaly map (MAM) of the area under consideration, wesubtracted the 2010 International Geomagnetic Referenced Field(IGRF) from the total magnetic intensity (TMI), taken from theEMM2010 (Eq. (2)).

MA ¼ TMI–IGRF2010: ð2Þ

As the methodology requires different magnetic grids to estimatethe lateral variations of the CPD, the MAM was discretized into win-dows. These windows correspond to different magnetic provinceswith the goal of preventing any long wavelength cutting. To properlycover the area, the grids were designed to overlap each other.

To estimate the size of these windows, the maximum CPD ofthe region was calculated (approximately 55 km). As the area mustbe at least four or six times the depth of the magnetic source (e.g.

Dimitriadis et al., 1987; Nwobgo, 1998), windows of 90,000 km2

were used. Sequentially, the RApS for each of these was computed;and the CPD was estimated from the maximum slope in the spectrum(m). The relationship between the slope and the source of the anom-aly is given by Eq. (3).

Depth ¼ −m=4π: ð3Þ

We calculated a total of fifty-nine (59) depth points (Table 2) withan error ranging from ±0.2 to ±1.5 km related to the slope fitting.The average error of the estimation was around ±5% of the depth(Nwobgo, 1998); therefore, additional errors vary from ±0.88 kmto ±2.73 km. The largest error was ±4.23 km for the Guayana Shieldwith the deepest CPD point. All errors in estimation are presented inTable 2. Table 3 offers a comparison between CPD, heat flow andmag-netic anomalies.

4. Results

The CPD in Venezuela and the Eastern Caribbean ranges between54 and 17 km (Tables 2 and 3). The errors of the estimation are inthe interval between ±4.5 and ±1.08 km. Bearing in mind the calcu-lated depth values, such accuracy could be defined as acceptable (seeSection 3.3 for details on the errors). The deepest CPD values corre-spond to the Guayana Shield and the shallowest to the VenezuelaBasin (Fig. 5). The CPD map (Fig. 5) shows two well-defined sections:one associated with the South American continental crust, the otherwith the Caribbean oceanic crust. In the continental domain, thehighest values are located in the easternmost part of the map(62°W longitude, 8°N latitude) extending throughout the cratonic re-gion (from latitude 2°N to 10°N and from longitude 65°W to 59°W)and covering the southernmost section (from latitude 2°N to 3°N).

Fig. 5. Curie point depth map, contours every 5 km (contours mention in the text are also shown). White diamonds show where the CPD was estimated. It ranges from 17 to 55 kmdepth: in continental Venezuela, from 27 to 55 km; while in the Eastern Caribbean, from 17 to 25 km. The deepest CPD are associated with the oldest cratonic regions of theGuayana Shield, while the shallowest area is related to the thin crust region within the Eastern Caribbean. P–P′ represents the profile in Fig. 7. Some tectonic features are shown.

45M.S. Arnaiz-Rodríguez, N. Orihuela / Tectonophysics 590 (2013) 38–51

The CPD values in this region range between 54 and 37 km with amean estimation error of ±3.3 km. A high CPD anomaly is locatedfrom latitude 6°N to 9°N, ranging between 73°W and 69°W longitudewith N45E orientation (parallel to the Merida Andes; its mean CPDvalue is 36.5 km with a mean estimation error of ±3.2 km.

Furthermore, the transition between the deepest CPD and theshallowest values coincides with a region in northern Venezuela,

specifically located between longitude 10°N and 12°N, parallel tothe Caribbean Mountain Range and the Falcon Basin (Figs. 1 and 5).The CPD values in this region range between 25 and 30 km. It has ahigher gradient in the West (~0.025 CPD km/km) than in the East(0.016 CPD km/km) with a general E–W trend.

As for the Oceanic domain (north from latitude 12°N), the CPDvalues range from 17 to 25 km with a mean of 23 km, and an

Table 2Curie point depth values estimated from spectral analysis. Error of the CPD estimationis presented for each point; see text for a brief discussion on the error estimation.

Longitude Latitude CPD(km)

±Error(km)

Longitude Latitude CPD(km)

±Error(km)

−62.72 7.86 54.53 4.23 −67.5 10 28.65 2.09−63.77 2.65 44 2.76 −71.86 8.6 32.75 3.79−68.15 8.29 32.4 3.46 −72 5 35.74 2.99−60 17.5 23.38 2.40 −72 17.85 20.29 2.74−60 12.5 25.69 1.78 −72 13 24.95 2.26−60 15 20.3 2.04 −70 3.7 34.16 3.18−60 10 31.52 2.69 −67.5 5 32.82 3.88−60 5 43.33 3.33 −62.5 15 23.74 2.92−68 12 24.13 2.61 −62.5 10 37.22 2.91−70 6 33.2 2.36 −72.5 15 25.8 2.57−69.37 15.46 25.12 2.24 −72.5 10 33.59 2.73−70 10 28.75 2.44 −62.5 5 43.56 2.32−70 5 33.66 2.13 −65.87 14.59 17.5 1.08−65 17.5 20.94 2.00 −65 16 24.75 2.77−65 13 18.44 2.45 −67.3 6.7 33.01 2.12−65 10 31.04 1.84 −65 5 34.46 3.79−65 7 33.9 3.30 −61.26 2.61 39.95 4.49−65 2.5 43.73 3.52 −61.15 7.78 46.87 3.16−69 16 26.52 2.78 −62.66 17.76 20.45 3.04−67.4 2.8 37.67 2.84 −67.4 13 21.21 2.55−70 17.5 22.32 2.10 −70 10 33.33 2.66−70 12.5 24.07 2.55 −64.2 9.4 37.59 4.25−70 8.5 36.71 3.34 −71.24 7.75 36.88 3.64−70 2.5 38.9 2.75 −62 13 26.33 2.31−71.4 12.5 21.63 2.09 −72 2.6 36.37 2.70−65 15 17.75 2.26 −65.8 8.8 32.2 3.22−67.3 15 18.79 2.56 −67.35 17.45 24.11 2.04−61.26 16 20.13 1.88 −71 9.7 34.62 3.72−69.5 17.3 24.01 2.87 −70.6 15.7 23.87 2.10−66.7 12 19.37 2.32

Table 3Comparison among CPD, heatflow, andmagnetic anomalies to some regions in Venezuelaand the Eastern Caribbean. Values shown for each region are: mean CPD, mean heat flow,maximum, minimum and mean magnetic anomalies.

Structure CPD(km)

Heat flow(μcal/m2 s)

Magnetic Anomalies (nT)

Max Min Mean

Guayana Shield 42 1.4 272.9 −334.4 −106Guarico Sub-basin 32 4.53 −53.3 −307.2 −188Maturin Sub-basin 39.5 2.27 −65.1 −486.3 −221.5Maracaibo Basin 34.5 1.38 −84.9 −286.7 −171.1Venezuela Basin 22 1.99 10.83 367.6 173.9Aves Ridge 23.2 2.87 72 341 142.7Bonaire Basin 23.8 2.23 −23.41 −319.5 −146.4Lesser Antilles and Thrust front 22.5 2.43 63.6 −276.5 −147.1

46 M.S. Arnaiz-Rodríguez, N. Orihuela / Tectonophysics 590 (2013) 38–51

estimation error of ±3.25 km. Two shallow CPD regions are found.One is located in the northern section of the Lesser Antilles Arc(from latitude 14°N to 18°N and from longitude 59°W to 62°W);the other, in the center of the Venezuela basin (from latitude 12°Nto 15°N and from longitude 64°W to 68°W).

5. Discussion

5.1. Venezuela

The continental CPD, which has a mean of 38 km (Table 3), showsthe largest CPD values within the region in the southeastern portionof the map (mean of 42 km), attributed to the cratonic area of theGuayana Shield (Imataca, Pastora and Roraima) (Fig. 5). The maxi-mum CPD (54 km) is coincident with the Imataca and the Roraimaprovinces, which are the largest negative (Fig. 3A) and positive(Fig. 3B) magnetic anomalies in Venezuela, respectively, and theoldest tectonic provinces in northern South America. The variationsof the CPD along the Guayana Shield could be a response to the vari-ations in crustal thickness along the whole cratonic region and, prob-ably, a direct response of its isostatic state (Fig. 5). For Schmitz et al.(2002, 2008) its crustal thickness is 45 km; for Niu et al. (2007) itvaries from 40 km to 44 km. Even though CPD mean values in thecratonic region are similar to the Moho depth (which suggests thatthe Guayana Shield is a thermally stable platform), 9 km of differencebetween the largest CPD value and the crustal thickness are unac-counted for. This situation reveals that the uppermost mantle beneaththe shield is magnetic.

The 36 km CPD contour (Fig. 5) couldmark the frontier between thelower Precambrian (Imataca and Pastora) and upper Precambrian(Cuchivero) provinces (along longitude −65°, south of latitude 10°),as suggested by Trifonova et al. (2009). A shallower CPD anomaly locat-ed between longitude −65° and −70° and latitude 4° and 7° (mean

34 km) is intertwined to the presence of the Cuchivero province aswell as the C–C′ magnetic alignment. Its estimated crustal thicknessvaries from 32 to 38 (Niu et al., 2007). This suggests that it has differentisostatic behavior compared to the rest of the Guayana Shield. Nonethe-less, it can be considered as a thermally stable province, since the CPDand the crustal thickness are very similar.

As observed, the results point out that the Guayana Shield is athermally stable platform, as other shields are (Mooney and Vidale,2003; Sharma et al., 2006). Part of its uppermost mantle is magnetic,as found in other cratonic structures (Chang, 2008; Toft and Haggerty,1988). The heat flow levels (1.4 μcal cm−2 s−1 estimated by Hamzaand Muñoz, 1996) are within the standards for continents, oreven lower (1.55±0.04 μcal cm−2 s−1, according to Turcotte andSchubert, 2007).

The partial NE–SW alignment of the 32 and 35 km CPD contoursand D–D′ magnetic anomaly (Fig. 3) might limit the upper Precam-brian and Paleozoic provinces, which is consistent with the proposalof Feo-Codecido et al (1984) about the position of the Apure Fault. Thisevidence would place the CPD within the lower continental crust ofeastern and central Venezuela, as has been found for the Indian subcon-tinent (Sharma et al., 2006) and for Turkey (Maden, 2009).

Accordingly, the joint interpretation of the CPD and the magneticanomalies allow us to limit: (a) the major magnetic provinces in con-tinental Venezuela, and (b) the cratonic provinces beyond the limitsof surface geology (Fig. 6). As a matter of fact, we have taken intoaccount previous works about the basement configuration of thecontinental basins with its major faults and allochthonous terranes(Feo-Codecido et al., 1984; Yoris and Ostos, 1997). Based on the mag-netic long wavelength anomaly E (Fig. 3), we include the IglesiaGroup to this configuration, which has been thought to be the base-ment to the Mérida domain by Bellizzia and Pimentel (1994). We as-sociate the magnetic anomaly F with the basement of the Guajirapeninsula, characterized as a Paleozoic orogenic belt (Fig. 3F).

The CPD in the Venezuela Eastern Basin (mean 36 km) is shallowerthan the Moho depth, derived from receiver functions (44–50 km; Niuet al., 2007) and deep seismic observations (40–55 km; Schmitz et al.,2008). The CPD values of the Guarico sub-basin are around 32 km(Table 3), while the crustal thickness is around 40 km. In the Maturinsub-basin, the CPD ranges from 35 km to 45 km (with a mean of39.5 km; Table 3), while the crustal thickness values range from 45 to55 km. The thermal anomalies reported in the region ranging from2.5 μcal cm−2 s−1 to 4.28 μcal cm−2 s−1 (with a mean of3.77 μcal cm−2 s−1, Fig. 2) are responsible for the mismatch betweenthe crustal thickness and the CPD, since a heat flow higher than normalwould make the CPD closer to the surface. This phenomenon is an ex-pression of an Oligocene isostatic rebound driven by the reactivationof normal faults in the Guárico Basin (Pérez de Armas, 2005). Eventhough the CPD lies within the crust, there is a close relation betweenthe crustal thickness and the CPD variations.

Fig. 6. Map showing the distribution of the autochthonous Precambrian terrains (Guayana Shield provinces) and the allochthonous Precambrian and Paleozoic terrains, derivedfrom CPD and magnetic anomaly interpretation.Previous interpretations by Feo-Codecido et al. (1984), Yoris and Ostos (1997) and Bellizzia and Pimentel (1994) have been strongly taken into account.

47M.S. Arnaiz-Rodríguez, N. Orihuela / Tectonophysics 590 (2013) 38–51

The 30 km CPD contour in northwestern and north centralVenezuela (Fig. 5) marks a limit that appears in the Moho depth mapfrom receiver functions (Niu et al., 2007) and in the estimation fromseismic refraction (Schmitz et al., 2008). Within this region, a crustalshortening congruent with the formation of the Falcon Basin has beenreported (Bezada et al., 2008; Sousa et al., 2005). The heat flow data of3 μcal cm−2 s−1 reveals a system with a strong thermal componentthat surely affects the magnetic response of the crust. Unfortunately,the CPDM does not have enough spatial resolution to reveal the varia-tions produced by this local process.

As for northwestern Venezuela, particularly, in the MaracaiboBasin (with a mean of 34.5 km; Table 3), the CPD values are close tothe values of the Moho discontinuity (40 km; Schmitz et al., 2008)(Fig. 5). Heat flow values (mean 1.47 μcal cm−2 s−1) are aroundthe standard heat flow for continents (Fig. 2). The Maracaibo Basinappears to be a thermally stable continental basin, unaffected by thecompression suffered by the Maracaibo Block (Audemard andAudemard, 2002). In southwestern Venezuela (longitude −72° to−70°, and latitude 7° to 8°), the CPD locally deepens to 37 km,representing either the flexure produced by the Merida Andes(Arnaiz-Rodríguez et al., 2011), or the graben systems located withinthe Barinas–Apure Basin (Feo-Codecido et al., 1984).

5.2. The Eastern Caribbean

The CPD in the Eastern Caribbean shows a stable zone with a meanvalue of 23 km (Table 3). Due to the fact that the crustal thickness ofthe Caribbean Plate is at most 20 km (Edgar et al., 1971; Houtz andLudwig, 1977; Ladd and Watkins, 1980; Officer et al., 1959), theCPD isotherm is found in the upper mantle (Fig. 5), representing anormal behavior for a relatively old oceanic lithosphere. Althoughthe CPD does not seem complex, the heat flowmap reveals a compositeof thermal scenarios with values ranging from 1 to 5.58 μcal cm−2 s−1.In this sense, the Caribbean mean heat flow exceeds the values foroceanic basins, which are around 2.41±0.52 μcal cm−2 s−1 (Fig. 2)(Turcotte and Schubert, 2007).

Regarding the Lesser Antilles, the CPD minimum (18.5 km) is con-centrated in the northern part of the Arc. It can be related to the mostactive portion of the subduction, which has its southern limit nearthe Tiburon Fault Zone. The high heat flow values (from 2.5 to4.03 μcal cm−2 s−1) can be attributed to the magmatism in the ac-tive Lesser Antilles arc (Fig. 2). The maximum heat flow is concentrat-ed in Dominica Island with 7 active volcanoes. The extension ofthe anomaly can be correlated to the presence of a well-developedmantle wedge between the Caribbean plate and the Atlantic slab(e.g. Doglioni et al., 1999). Unfortunately, the CPDM is not detailedenough to display the thermal structure of the subducted lithosphere,as described by Blakely et al. (2005), Turcotte and Schubert (2007),and Saltus and Hudson (2007), among others.

The CPD of the Aves Ridge does not seem affected by regionalscale thermal processes (Fig. 5). Even though it is considered extinct(e.g. Bouysee, 1988; Bouysse et al., 1990; Sykes and Ewing, 1965),the maximum heat flow value with 5.26 μcal cm−2 s−1 (Fig. 2) is lo-cated over this feature. Clark et al. (1978) associated this value to thepresence of rocks rich in radiogenic elements, which were concen-trated during its subduction-related formation by the enrichment ofascending magma due to the depletion of the mantle (Langseth andVon Herzen, 1970).

Perhaps, the most important anomaly in the offshore part isthe heart shape zone over the Venezuela Basin (with a mean of18.8 km), reaching a minimum of 17 km depth (Fig. 5). It can be cor-related with: (a) deformed magnetic stripes on the floor of the basin(Ghosh et al., 1984), (b) a local maximum in the heat flow map of2.6 μcal cm−2 s−1, and (c) and the gravimetric maximum of theVenezuela Basin (Arnaiz-Rodríguez and Garzon, 2012). A profilealong 14.25°N (Fig. 8) shows the set of anomalies correlated to theCPD shallow area.

The relation between the CPD and the crustal depth variations re-veals that the entire crust and the upper most mantle are magnetic(except for the deepest section of the Aves Ridge root), which isusual in oceanic domain (Arkani-Hamed, 1991). The CPD shallowarea is somehow bound to the thin crust region within the VenezuelaBasin (Mauffret and Leroy, 1997), related to the extension produced

48 M.S. Arnaiz-Rodríguez, N. Orihuela / Tectonophysics 590 (2013) 38–51

during the CLIP formation (Diebold et al., 1999). The CPD variations,the Bouguer anomaly, and the crustal thickness are partially corre-lated, as most thick crust regions (areas with CLIP, Beata Ridge and

-73 -71 -69 -67

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Beata Ridge

Venezuela Basin

Fig. 7. Profile along latitude 14.25°N showing the variations in bathymetry, magnetic anomthe anomalies. Anomalies in all the data sets are related to the location of the CPD shallow

Aves Ridge) have a deeper CPD than the thin crust region (in whichthere is no CLIP) (Fig. 7). There is also a clear relation between theheat flow data (Fig. 7) and the crustal thickness, as the mantle heat

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49M.S. Arnaiz-Rodríguez, N. Orihuela / Tectonophysics 590 (2013) 38–51

is forced to escape through thinner crust (Nyblade and Pollack,1993). In the thin crust region, the heat flow is higher than in therest of the Venezuela Basin. Finally, the magnetic anomalies, whichcorrespond to the magnetic chrons of the oceanic crust, are de-formed by the regional component due to the CPD variations. Itwould seem that the CPD shallow regions are in association withthis group of anomalies, but other interpretations such as mantle dy-namics should not be discarded with the available data (OrihuelaGuevara et al., 2012).

6. Conclusions

In this study, and for the first time, we have produced a map re-vealing the variation of the Curie point depth for the Venezuelan ter-ritory and the Eastern Caribbean. The analysis of our results and thecomparison with previous studies allow us to draw the followingconclusions:

1. The use of spectral analysis (e.g. Blakely, 1988; Connard et al., 1983;Nwankwo et al., 2009; Nwogbo, 1998; Onwuemesi, 1997; Shuey etal., 1977) and newmagnetic models (EMM2010) allows us to engen-der a series of lateral CPD variations that are geologically coherent (onthe basis of heat flow data) and have acceptable errors.

2. The EMM2010 can be used to estimate the CPD variations usingspectral techniques for a well-covered region.

3. The CPD analysis reveals two very different scenarios: the continen-tal crust for Venezuela and the oceanic crust for the Eastern Caribbe-an. The mean value within the continental crust is 38 km deep;within the oceanic it is 23 km.

4. The mean value on the Guayana Shield is 40 km, a result that is co-herent with the behavior of a thermally stable platform with acrustal deep between 40 and 45 km. Moreover, important lateralvariations and high gradients on the CPD appear to be related tothe isostatic state and age of different provinces. Under theImataca Province the CPD reaches 54 km: beneath it 9 km of theupper mantle is magnetized.

5. The continental basins in Venezuela have different thermal behav-iors. Maracaibo is a thermally stable basin with normal heat flowvalues and a CPD isotherm similar to theMoho discontinuity. EasternVenezuela is a thermally affected basin, particularly in the Guaricosub-basin with anomalously high heat flow. The CPD is 8 to 10 kmshallower than the Moho depth.

6. A large non-perturbed area with a mean value of 23 km character-izes the Eastern Caribbean's CPD; hence the isotherm is locatedwithin the upper mantle. This stable region is characterized bylow heat flow values, related to the thickened Caribbean crust.

7. A shallow CPD is located in the Venezuela basin reaching a mini-mum of 17 km depth. This phenomenon is most likely bound toa thin crust region, although it covers a wider area extending tothicker crust. It could also be related to mantle dynamics.

Finally, it is worth pointing out that, in the frame of the CaribbeanPlate evolution models, heat flow, CPD, and magnetic data should betaken into consideration. Other regions related to Cretaceous mantledynamics (such as Ontong-Java and Parana plateaus) present anoma-lous elastic wave patterns, large magnetic anomalies, an anomalousheat flow that has shed some light into the origins of these geologicalfeatures. Therefore, the behavior of the CPD in the Eastern Caribbean(Fig. 5) with significant lateral variations in the center of the Venezuelabasin shows changes in the magnetization of the upper mantle thatcould be related to early stages of the Caribbean Plate evolution(Orihuela et al., 2011).

7. Further work

The next step of our research focuses on comparing the results ofthis study with other wide spread methodologies used to estimate

the CPD variations (e.g. Bouligand et al., 2009; Maus and Dimri,1995; Maus et al., 1997; Okubo et al., 1989). Another step is to usemagnetic data (available at NDGC) to understand the Caribbean andSouth American interactions. Finally, seismological data will be usedhand in hand with the results from this research to provide newlight in the Caribbean formation and current tectonic setting.

Acknowledgments

We thank Stephan Maus, D.P. Anand and Abhey Bansal for the com-ments on themethodology and help in the development of the research,and toMichael Schmitz for the notes on themanuscript.We also expressgratitude to the anonymous reviewers for constructive criticism thathelped us to improve the document.

Appendix A. Supplementary data

Supplementary data associated with this article can be found inthe online version, at http://dx.doi.org/10.1016/j.tecto.2013.01.004.These data include a Table of some of the CPD estimations aroundthe globe by many authors from 1974 to 2010. A map of the magneticstations in Venezuela and the Eastern Caribbean used to build theEMAG2 is also included.

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