The Infante D. Henrique Basin

This basin, here named ''Infante D. Henrique Basin``, corresponds to a topographic threshold between the structural highs of Gorringe Bank and Marques de Pombal Thrust, west and east respectively, and raising more than 1000 m from the floor of the Tagus and Horseshoe abyssal plains. The Inf`ante Don Henrique Basin has triangular shape, widening (from 2.3 to more than 18.1 km) and deepening (from 3725 m to more than 3900 m) northward. The CHIRP data cover just half of the basin, from the center to its eastern edge. In cross section, this basin has a asymmetrical shape: the basin axis (present-day depocenter) is located at the foot of the eastern wall, whereas the topography towards the western limit is dominated by a gentle (5°) and smooth slope. At least four main units (referred to as A to D, from top to bottom) have been identified from the CHIRP profiles (Fig. 11):

• Unit A: this unit is about 4.5 m thick and is characterized by a transparent to semi-transparent acoustic facies. Sometime a discontinuous reflector can be identified within this unit.
• Unit B: this unit is about 10.5 m thick. It is characterized by continuous, high amplitude and well stratified reflectors. They are most probably related to turbiditic sedimentation.
• Unit C: this unit is about 7 m thick and shows characteristics similar to Unit A.
• Unit D: this unit is at least 8.3 m thick (its lowermost limit is not always well determined) and has similar characteristics to Unit B.

All the sedimentary units show a relatively high degree of deformation. They are folded forming antiforms and sometimes they are affected by reverse faults, resulting from the compressional tectonic activity. The upper units tend to thin as they approach the edge of the basin.

Figure 12: BS98. Core BSC6 and chirp data interpretation.