Presentation given on the occasion of STRATI2015 (Graz, Austria)
Lebanon landscapes provide a wide variety of exposures of shallow-water Jurassic and Cretaceous rocks. The stratigraphy of the country still bears the mark of the late Louis Dubertret (1904-1979), once the editor-in-chief of the "Asie" section of the "Lexique Stratigraphique International". Dubertret, who was based in Beirut, was the major contributor to the geological mapping of the country. His approach of lithostratigraphy was mostly facies-driven as documented hereafter by the case study of the Lower Cretaceous "Falaise de Blanche", a Cyclopean limestone wall that runs throughout the Mount Lebanon and Anti-Lebanon ranges. On the outcrops, whitish micritic facies are commonly found overlying yellowish grainy facies. Dubertret (1950, 1955) merged these grainy limestone facies, either oolitic or bioclastic (with wackestone to grainstone textures), with underlying siliciclastic facies under a label "C2a"; he ascribed a label "C2b" to the overlying micritic limestone facies (with mudstone to wackestone textures). However, one facies may locally be missing or interfinger with the other, suggesting that these areas represent transitional zones between a shoal barrier and its protected lagoon.This geometrical relationship is merely the signature of regular lateral changes in facies. The fossil assemblages, which are very similar in both facies, also plead for their grouping in a single unit. In view of working in a well-constrained stratigraphic framework and getting rid of the issue of the lateral changes in facies, we decided on a more modern approach of lithostratigraphy (Murphy & Salvador, 1999; see Granier, 2000, for a first use in the Middle East), that of the UBU, i.e., Unconformity Bounded Unit (Wheeler, 1959), that of the Alloformation (NACSN, 1983), or that of the regional stage (Hedberg, 1976; Rey et al., 2008; see Granier et al., 2011, for a first use in the Middle East): we adopted the last category (Maksoud et al., 2014). UBU and Alloformations are unconformity bounded "rock units" (sedimentary rocks for the first and all rocks for the second) whereas a regional stage is a "time-rock unit" bounded by isochrones (Hedberg, 1976). These proposals would appear to be irreconcilable; however, they are not if one consider a founding principle of sequence stratigraphy that states that any discontinuity on a shelf passes laterally to a continuity in the neighbouring basin. In conclusion, we introduced a new regional stage, the "Jezzinian". The type-section of which is sited in Jezzine, 70 km south from Beirut. (...)
44. •Abandonment of the label “Falaise de Blanche”
•Introduction of the Jezzinian:
CONCLUSIONS
its type-section
in its type-locality
bounded by two unconformities
(that theorically pass to conformities basinward)
with its fossiliferous contents
45. •Abandonment of the label “Falaise de Blanche”
•Introduction of the Jezzinian:
CONCLUSIONS
its type-section
in its type-locality
bounded by two unconformities
(that theorically pass to conformities basinward)
with its fossiliferous contents
•The Jezzinian = UBU = Alloformation = Regional stage
•Regional stages prove to be practical tools,
facilitating correlations with other regional stages (herein with the
Persian Gulf upper Kharaib/ian/) and with international standard
stages (herein uppermost Barremian – lower
Bedoulian/lowermost Aptian auct./)
