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Depositional history of the Paleogene Adriatic carbonate platform

The Paleogene Adriatic carbonate platform existed within the Central Tethys from Paleocene (Danian) to late Middle Eocene (Bartonian). Its depositional history differs from the stages-pattern recognized in the platformal development in the Tethys region, in the Pyrenees and Egypt. In the Adriatic, the shallow-marine carbonate regime is composed of various facies types which are defined by the larger benthic foraminiferal associations and sedimentary structures. These facies are grouped into 3 main biosedimentary units, BiosZ2 to BiosZ4. These zones followed one another in a step-wise geographic pattern and record temporal and spatial demise of certain ecological conditions. Sedimentation within each zone started with restricted, marginal marine, paralic and pallustrine carbonates that we consider as the initial onset of full marine conditions. Once the marine regime was obtained, the shallow-marine settings supported the development of diverse and abundant foraminiferal assemblages. The biota suggests that platform jumped into the third Tethyan stage even though sedimentation started in SBZ 1 and lasted until SBZ 9 (BiosZ 2), in SBZ 2 until SBZ 12 (BiosZ 3) and in SBZ 11 until SBZ 14 (BiosZ 4). Interestingly, the second Tethyan stage, coralgal facies, is recorded within the NW margin in the BiosZ 2 area only. The characteristics that differentiate the PgAdCP from others are: (1) a reduced species richness in the Paleocene succession ; (2) less diverse Eocene foraminiferal assemblages ; (3) absence of some taxa (Spiroclypeus sp., Heterostegina sp., Pellatispira sp.) ; (4) absence of encrusting foraminifera ; (5) the consistent occurrence order of certain larger foraminiferal groups ; (6) concurrence of BiosZ 3 withAlveolina histrica lineage and Alveolina levantina lineage with BiosZ 4.

Adriatic carbonate platform, Paleogene, larger benthic foraminifera

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