Shallow marine ostracode turnover in response to environmental change during the Paleocene–Eocene thermal maximum in northwest Tunisia

Abstract

a b s t r a c tTwo outcrop sections spanning the Paleocene-early Eocene boundary in the Sidi Nasseur-Wadi Mezaz area in northwest Tunisia provided rich ostracode assemblages, yielding 26 species of which three are newly described: Reymenticosta bassiounii, Reymenticosta nasseurensis and Buntonia? tunisiensis. The recorded ostracode fauna and associated foraminifera reflect deposition in a coastal to inner neritic environment. Many of the recorded taxa have a wide geographic distribution throughout the Middle East and North Africa. A correspondence is also observed with West African faunas, especially in the early Eocene fauna. These taxa seem to have originated in West Africa during the Paleocene and migrated northwards during the late Paleocene to early Eocene. Sea-level change and decrease in oxygenation associated with the Paleocene-Eocene thermal maximum (PETM) caused the local disappearance of the South Tethyan Paleocene fauna represented by Paracosta kefensis (morphotype-A), Paracosta aff. paleomokattamensis, Paracypris sp. B Esker, Loxoconcha saharaensis, Buntonia sp. 3 Donze et al., Protobuntonia nakkadii, and probably Reymenticosta bassiounii and R. nasseurensis. Simultaneously, a new but poorly diverse AfroTethyan fauna, mainly represented by Alocopocythere attitogonensis and Buntonia? tunisiensis, settled in the studied part of the basin. After the PETM, diversity increased again as various taxa (e.g. Bairdia aegyptiaca, Reticulina lamellata and Aegyptiana duwiensis) (re)appeared. Although detailed records across the P/ E boundary are still sparse, it appears that the PETM exerted significant influence on the paleobiogeography and composition of Tethyan ostracode faunas.

The Paleocene-Eocene Thermal Maximum: A Perturbation of Carbon Cycle, Climate, and Biosphere with Implications for the Future

“…In contrast to the marked extinction of benthic foraminifera, other groups of benthic and planktic microfossils show little or no extinction at the PETM. Ostracodes are the only other group of deep benthic organisms with detailed records across the PETM, and their response ranges from decreased diversity and abundance (Steineck & Thomas 1996), to little change in diversity or relative abundance distribution (Webb et al 2009), to rapid changes in ostracode species composition (Morsi et al 2011, Speijer & Morsi 2002.…”

Shallow marine response to global climate change during the Paleocene‐Eocene Thermal Maximum, Salisbury Embayment, USA

“…They provide context between terrestrial continental and shallow marine deposition and allow for high‐resolution correlation between the shelf and open ocean sites [ Schmitz and Pujalte , ]. Changes in benthic faunas are especially revealing, documenting stratification in the water column, continental runoff, and dysoxia [ Morsi et al , ; Stassen et al , ]. In eastern North America, most middle to outer neritic sites (e.g., Bass River, Wilson Lake, and South Dover Bridge, to name a few) are in Maryland and New Jersey [e.g., Gibbs et al , ; Sluijs et al , ; John et al , , Self‐Trail et al , ; Stassen et al , ], but none of these sections is from the inner part of the shelf.…”

Paleoclimatic Insights on the Paleocene-Eocene Thermal Maximum in Central Iraq, Based on Calcareous Nannofossils, Ostracoda and Geophysical Data

“…The species Alocopocythere attitogonensis appeared in few numbers during the PETM event and continued beyond (Early Eocene) with a noticeable increase in the number of its individuals. This was due to the ability to adapt and high endurance to the various changes in environmental conditions [27]. This was represented mainly by the low percentage of oxygen during the PETM, which showed its repercussions on this species in the studied section through the appearance of its valves in a grey colour that often appears on the Ostracoda valves carapaces in the reduction environment.…”