In search of the Latest Danian Event in a paleobathymetric transect off Kasserine Island, north-central Tunisia

Abstract

Danian (lower Paleocene) sequences in north-central Tunisia are dominantly composed of marls and shales but a conspicuous, indurated glauconite-bearing marker bed is associated with the P3a-P3b transition. This glauconite bed is considered to correlate with the Latest Danian Event (LDE) described from the Nile Basin in Egypt, with the 'top Chron C27n event' (Atlantic and Pacific Oceans) and with the 'CIE-DS1' (Zumaia, Spain). The LDE is thought to reflect a short period of global warming, similar to the Paleocene Eocene Thermal Maximum, but of lesser magnitude. The presence of a glauconitic bed at the P3a/P3b transition in Tunisia suggests that the sequence is condensed, which is confirmed by planktic foraminifer and nannofossil biostratigraphy, and by the absence of the typical LDE beds found in most Egyptian sections. Benthic foraminiferal assemblages were quantitatively analyzed in three sections in north-central Tunisia (Sidi Nasseur, Garn Halfaya, Elles) in order to characterize the paleoenvironmental evolution during the late Danian and compare this with sections in Egypt. The benthic foraminiferal assemblages indicate that the Tunisian sections were located along a depth-and a paleoenvironmental gradient on the shelf north of Kasserine Island. The reconstructed depth range is comparable with sections in Egypt, and encompasses middle neritic (Sidi Nasseur section) to shallow upper bathyal depths (Elles section, with up to 16% Gavelinella beccariiformis below the P3a/P3b). Like in Egypt, assemblage shifts across the P3a/P3b subzonal transition indicate shallowing and a transition to a more eutrophic paleoenvironment, characterized by relatively high abundances of buliminids and Stainforthia sp. The δ 13 C and δ 18 O records generated on well-preserved specimens of the ostracode species Bairdia failed to demonstrate the presence of the carbon isotope excursion (CIE) associated with the LDE at the base of Subzone P3b. A condensed section or a hiatus associated with the glauconite bed would explain why the CIE is not recorded in the Tunisian sections.

Sedimentological, Mineralogical and Geochemical Analysis of the Hyperthermal Latest Danian Event across the Galuconitic Marker Bed (Central Tunisia)

“…In this study, however, we applied the biozonation of Arenillas and Molina [24], integrated with the taxonomic concept of Igorina albeari as defined in Arenillas [25] because it placed the glauconitic bed in the upper Danian, within the Morozovella cf. albeari biozone, which is in agreement with the calcareous nannofossil biozones (NTp7a/NTp7b) [11] and the Global Stratotype Section and Point (GSSP) Zumaia [26].…”

“…Almost studies of Danian/Selandian transition in Tunisia followed the standard biostratigraphic zonation of Berggren and Pearson [2,9,11,18,23]. According these latter, the studied interval spans P3a/P3b subzones.…”

“…On other hand, all the studied sections concerned the glauconitic marker bed were deposited under shallow to neritic-water environments [7,8,[12][13][14][15][16][17][18][19] noted eutrophication and periods of drop of oxygenation at the bottom water within the glauconitic marker bed [11]. remarked the absence of the LDE records in Elles, Sidi Nasseur and Garn El Halfaya sections, although the noticeable paloenvironmental changes across this bed.…”

Planktonic foraminiferal biostratigraphy and paleoenvironment of the Danian/Selandian in west-central Sinai (Egypt), implications from the Nukhul section

“…Due to their behavior vis-à-vis of the environmental conditions, their diversity and their richness in different marine domains, benthic foraminifera are good indicators of palaeodepths (El-Dawy 2001;Bellier et al 2010;Speijer 2003;Sprong et al 2009Sprong et al , 2011Sprong et al , 2013Storme et al 2014). …”

“…This level coincides with the first appearance of the species Igorina albeari marker of the base of the P3b subzone of the Selandian. This level has been considered by some authors as the precursor event of Paleocene-Eocene Thermal Maximum (PETM) (Speijer 2003;Guasti et al 2005;Obaidalla et al 2009;Bornemann et al 2009;Youssef 2009;Soliman and Obaidalla 2010;Sprong et al 2009Sprong et al , 2011Sprong et al , 2013Farouk and El-Sorogy 2015). Several studies have been performed on the Danian/Selandian transition of the Nile Basin in Egypt but the limit had not been well identified despite the definition of the global stratotype (Luger 1985;Bassiouni et al 1991;Tantawy et al 2001;Hewaidy et al 2006;El-Azabi and Farouk 2011;Boukhary et al 2013).…”