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Abstract
ABSTRACT: A ground magnetic survey in a Central-East area of the Santa Catarina Island tested the continuity of the Cretaceous mafic dykes beneath the aeolic sediments of the Joaquina plain. Vertical gradient measurements taken in 1880 stations did not detect any magnetic anomaly related to subsurface dykes. Four magnetic profiles located to the north and south of the main area showed the magnetic signature of various dykes some of them already mapped (north profiles), but also some in subsurface (south profiles). These results suggest that the dykes probably were shallow and truncated, and were already eroded along with the crystalline basement.
Highlights
The Brazilian Atlantic coast is cut by Cretaceous dyke swarms (Marques & Ernesto 2004) associated with the Atlantic opening
The VG data over the Joaquina dune area (Fig. 2) showed no magnetic anomalies or significant magnetic contrast that could be interpreted as borders of a magnetic body
Most of the area showed VG near zero, and the maximum VG (~5 nT/m), in some particular points, does not show any geometric pattern that could be related to any geologic feature of interest
Summary
The Brazilian Atlantic coast is cut by Cretaceous dyke swarms (Marques & Ernesto 2004) associated with the Atlantic opening. The most expressive one is the Ponta Grossa dyke swarm trending mainly NW; the other two are NE trending systems: the Serra do Mar swarm to the north, and the Florianópolis swarm to the south (Fig. 1). In spite of their geodynamical importance, there are very few geophysical investigations (Ferreira 1982, Ussami et al 1991, Stanton et al 2010) on these dykes which could contribute to a better understanding of its subsurface configuration and its role in the geodynamical processes of the eastern Gondwana breakup. Some parts of the island are covered by recent sediments, hampering the observation of possible lateral continuation of dykes
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