Older researchers considered this formation as essentially made up of two lithologic bodies, recognized by different colors, with a
diastem between (Soares, 1972, Fulfaro et al., 1984).
These basal gravels dip as much as 45 degrees to the west and have a sharp contact (presumably representing a
diastem) with overlying sands.
Tufa deposits will be studied in details concerning their internal primary features, tufa units and facies, microfabrics, diagenesis and interrupting
diastem periods.