Paleoclimate and paleoenvironment reconstructions from Middle Eocene successions in Egypt: Geochemical and micropaleontological approaches

Abstract

Forty-three rock samples have been collected from two sections, exposed at south east Beni-Suef area, Egypt. These samples showed richness in benthic foraminiferal assemblages and only rare occurrences of index planktonic foraminifera. The studied outcrops were lithologically subdivided into two Middle Eocene rock units named from base to top as follow: (1) the Qarara Formation (Lutetian) and (2) the El Fashn Formation (Bartonian). The investigated rock samples yielded 160 foraminifera species and subspecies which belonging to 4 suborders, 19 superfamilies, 34 families and 59 genera. The stratigraphic distribution of the identified species allowed us to construct four local benthic biozones which are: (1) Bolivina carinata Lowest Occurrence Zone (Lutetian), (2) Bulimina jacksonensis Lowest Occurrence Zone, (3) Nonion scaphum Lowest Occurrence Zone and (4) Brizalina cooki / Nonionella insecta Concurrent-Range Zone (Bartonian). These biozones were described and discussed in detail and correlated to equivalents recorded before in Egypt. The rareness of index planktonic foraminifers through the studied sections did not allow a biozonation. The shale samples showed low TOC values which may be related to high sediment influx and/or subjected to oxidation conditions. Bulk rock geochemistry, consistend with the benthic foraminifera ecological preferences, showed that the studied sections were deposited in moderate to high oxygen levels, warm climatic conditions and typical shelf marine settings. The identified species showed strong similarities with southern Tethys areas such as Libya, reflecting migration via trans-Sahara seaway, and minor similarities with those identified from the northwestern Tethys (Italy, France, Spain, England) province attributed to the benthic nature which limit their ability to move for a long distance and related to cooler, latitudinal zoned climatic conditions which was unsuitable for their biological demands.