Early eocene larger benthic foraminifera (mainly orthophragminids) from the El Garia formation and associated carbonate units, North Tunisia: Paleobiogeographic insights

The shallow marine El Garia Formation is a prominent late Ypresian (late Early Eocene) carbonate reservoir in Mediterranean Basin offshore Tunisia (North Africa), characterized by the prolific development of larger benthic foraminifera (LBF) and composed of mainly nummulitids and orthophragminids. The El Garia Formation and a similar carbonate sequence, previously attributed to the El Garia Formation but distinguished as a separate unit in this study (Carbonate Unit I of mainly early Ypresian to early Late Ypresian age), crop out patchy in northern Tunisia, between capital Tunisia and Beja town. These units are underlain by planktonic foraminiferal deep-marine fine clastics and carbonates of the Chouabine Formation, while deep marine marls with planktonic foraminifera are also recorded in several levels of the Carbonate Unit I and lower part of the El Garia Formation. Considering the very poor information on the orthophragminids in the northern margin of Africa, we have studied this group; a- to clarify the taxonomy of orthophragminids, b -to establish a orthophragminid biostratigraphic scheme (OZ) and c- to recognize the paleobiogeographic affinities of this group, well known in Europe and west Asia but not in Africa. We have recorded a widespread occurrence of genera Orbitoclypeus, Asterocyclina and Nemkovella along with rather rare Discocyclina. The orbitoclypeids, characterized by both ribbed and unribbed taxa, are mostly represented by Orbitoclypeus schopeni, O. munieri, O. bayani, and O. multiplicatus lineages. Asterocyclinids are represented by Asterocyclina taramellii, A. alticostata and A. stella lineages while the presence of A. stellata is suspected. While Discocyclinids is represented by Discocyclina archiaci and nemkovellids is represented by Nemkovella stockari. The morphometry of these lineages resulted in the definition of their respective subspecies and a tentative orthophragminid zonal scheme (OZ) 3 to 8a was established. The planktonic foraminifera identified in some levels of the Carbonate Unit I and lower part of the El Garia Formation provide an independent tool for a more rigid stratigraphy. The associated fossil fauna and biota include common nummulitids, rotalids, textularids, miliolids, very sporadic alveolinids, red algae, echinoids, bryozoans, and bivalves. We extend the paleobiogeographic distribution of some Tethyan orthophragminids to North Africa.