Estimating the Depth to Magnetic Basement Bottom in South America and Caribbean Region from Magnetic Data Inversion

Wednesday, 17 December 2014
Javier Idarraga Garcia and Carlos Alberto Vargas Jiménez, Universidad Nacional de Colombia-Bogota, Bogotá, Colombia
We took advantage of the World Digital Magnetic Anomaly Map (WDMAM) to estimate the depth to the bottom of the magnetic basement (DBMB) in South America and Caribbean region. To achieve this, we performed three different spectral methods and chose the model showing greatest consistent with the geological and geophysical characteristics of the study area. Our results show that the DBMB varies between <2 and 55,7 km. Values less than 2 km predominate in Pacific and Atlantic offshore zones, which increase to maximum values of 20 km in the Caribbean Sea basin. Regarding the onshore region, DBMB's range between 12 and 28 km in Central America region, whereas South America exhibits values from 10 to 55,7 km. The highest values (>40 km) of the study area occur as a continuous belt that matches the Andes Cordillera in a zone between the latitudes 8,7° S and 32,6° S, with a width varying from 150 to 520 km.

After comparing our results with data on MOHO depth available for the study area, we found that the calculated DBMB's lie above the MOHO in most of the area. This implies that our depths can be correlated with the Curie Point depth, that is, the transition from magnetic to non-magnetic rocks is due to an increase in temperature up to the Curie Temperature. On the other hand, in areas like Northeastern and Southern Llanos Basin, Solimoes Basin, Familina Province, Chaco Basin and some sectors in Andean Foreland Basins, our DMBM's are still shallower than Moho but with differences not exceeding 5 km. In this case, it is likely that the bottom of the magnetic basement merely corresponds to the compositional change of magnetic material to nonmagnetic represented by MOHO discontinuity