Abstract

This report describes the results of seismic-refraction measurements conducted on the submerged coastal plain of the Buenos Aires province. Two elongated asymmetrical sediment-filled depressions in the Precambrian basement complex, the Rio Salado basin and Bahia Blanca basin (which includes the Rio Negro basin), were traced seaward. The two basins, separated by the Tandil high, trend approximately southeast. Each is about 150–200 km wide and at least 700 km long. No indication of closure was observed at the seaward end although both basins were traced well beyond the edge of the continental shelf.

Four seismic layers overlying the basement were determined in an unconsolidated layer (A), a semi-consolidated layer (B), and two zones in a consolidated layer (C) and (D). These layers are identified as Quaternary and Pliocene-Miocene, Lower Miocene and Upper Cretaceous, Upper Paleozoic, and Lower Paleozoic to a depth of about 8.0 km based on well logs and seismic-refraction data made available by Yacimientos Petroliferos Fiscales.

A sub-basement layer (6.84 km/sec) was measured under the continental rise at an average depth of 10–12 km. The Mohorovicic discontinuity was measured on two profiles at a depth of 26.5 km under the outer portion of the continental shelf.

The basement configuration and stratigraphic sequence along several traverses are shown by seismic sections. A 10-km interval basement-contour map of the area shows the outline of the basement as determined by marine seismic data together with the correlation to YPF seismic-refraction measurements on land.

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