Trace elements, stable isotopes, and clay mineralogy of the Elles II K–T boundary section in Tunisia: indications for sea level fluctuations and primary productivity

Abstract

Trace elements and stable isotopes in bulk rocks and foraminifera, bulk rock and clay mineral compositions, are used as palaeoproxies to evaluate sea level fluctuations, climatic changes and variations in primary productivity across the K–T transition at Elles II in Tunisia from 1 m (∼33 kyr) below to 1 m (∼70 kyr) above the K–T boundary. Results on clay minerals, major and trace elements, stable isotopes in bulk rock samples (e.g. Ca, Cu, Zn, Rb, Sr, Zr, Ba, δ 13C and δ 18O), and in foraminifera (Sr/Ca, δ 13C, δ 18O) indicate that the latest Maastrichtian (last ∼33 kyr) in Tunisia was marked by a relatively warm, but humid climate and a rising sea level. The transgressive surface is marked by deposition of a foraminiferal packstone just below the K–T boundary followed by maximum flooding across the K–T boundary (red layer and black clay layer). Humid warm conditions accompanied the maximum flooding, along with increased total organic carbon values and rapidly decreasing primary productivity. At the K–T boundary, an impact event (Ir anomaly, Ni-rich spinels, spherules) exacerbated already stressed environmental conditions leading to the mass extinction of tropical planktic foraminifera. Increasingly more humid conditions prevailed within the lowermost Danian Zone P0 (∼50 kyr) culminating in a sea level lowstand near the top of P0. A slow recovery of the ecosystem in Zone P1a coincided with a rising sea level and gradually less humid climatic conditions.