The creiaceous carbonates forming the Montgri massif (Berriasian ? to Santonian) were deposited in the southern, marginal areas of the basin. As they sedimented in shallow platform environments, they were very sensible to sea-level changes. Thus, the section is divided into seven allostratigraphic units (NASC, 1 983), numbered from 1 (o 7. Some of their bounding discontinuities include erosion with subaerial exposure (lower boundaries of the units 2, 4, 5 and 7), paleokarst (2 and 4) and lateritic-soil developments (lower boundary of the unit 2). The units numbered 2, 4 and 6 respectively show onlap relationships over truncated underlying strata, and the lower boundary of the unit number 7 is a disconformity. The unit number 3 is bounded by a discontinuity recording a non-depositional event, and the bottom of the unit 5 is a condensed section. The units 2 (Aptian) and 6 (Coniacian to Santonian I) record the activity of exlensional faulting along two structures known in outcrop; one of them can be observed in its original shape, and the other was inverted during the alpine compression. The uppermost strata in the unit 2 and the unit 7, respectively postdate these extensional structure
