49 2. The stratigraphy of the Middle Jurassic The cavernous dolomite is topped by an oolite bed identified as the last term of the Laeviuscula zone, placing the D7 bis discontinuity at an altitude of 90.6 m at this point (Fig. 6). The upper parts could not be observed directly by a geologist (and cannot be sampled). They are illustrated by plate n° 2. Above the D7bis, the Humphresianum zone has a lower vacuolar level. The upper vacuolar level is illustrated by photograph 5. Above a ledge, decimetric and ovoid cavernous forms have developed (photograph 4, plate 2). Discontinuity D8 is observed at an elevation of approximately 101 m, in the form of a karst joint (photograph 3) located above a nodular bench approximately 0.55 m thick that continues into the cliff. At the same place, at the “Passelourdin cave,” the cave floor rests on the pebble bench attributed by the authors to the reference level at the base of the Niortense zone, placing D8 at an altitude of approximately 99 m. Above the D8, the burrowed zone (Gabilly, 1978) is illustrated by photographs 1 and 2. This formation corresponds to limestone with tubular structures several meters thick on the “survey with climbing” and at the “Passelourdin cave.” This formation corresponds to the beginning of the Upper Bajocian and ends with the D8bis discontinuity, which marks the upper limit of the Garantiana zone. These vertical burrow banks are overlain by hard limestone belonging to the Parkinsoni zone above the D8bis discontinuity. Figure 6 Oolitic facies from top of Laeviuscula biozone.
RkJQdWJsaXNoZXIy NjA3NzQ=