GSSP for Danian Stage
Definition:
The base of the Cenozoic Era, Paleogene System, Paleocene Series and Danian Stage is defined at the reddish layer at the base of the 50cm thick, dark boundary clay in a tributary of the Oued Djerfane, west of El Kef, Tunisia, where it coincides with the Iridium Anomaly fallout from a major asteroid impact.
Location:
The GSSP is located in northern Tunisia about 7km west of the town of El Kef. The locality is reached by taking the road to Tajerouine for about 5km and then turning onto an unpaved road leading to the village of Hamman Mellégue. The GSSP section is located at 3km from the road sign to Hamman Mellégue between a small village and a recent artificial lake. The GSSP is reached after descending into this valley for about 1.5km. The GSSP is located at a latitude of 36°09'13.2"N and a longitude of 8°38'54.8"E.
The El Haria Formation at El Kef consists of:
- 90m of glauconitic and phosphated marl and marly limestone
- 310m of brownish to dark clay
- 65m of gray marl with fine interbedded limestone
- 200m of dark clay and marls containing the Cretaceous - Paleogene Boundary
- lower interbedded marl and limestone
Primary Markers:
The GSSP is defined at the base of the boundary clay. It is overlain by a rusty red layer containing a peak of Ni-rich spinel, which is more concentrated than the iridium anomaly. This implies that all the sediments generated by the meteorite impact belong to the Danian. This millimeter thick layer, containing the evidence of the meteorite impact and other significant geochemical changes, coincides with a sudden catastrophic mass extinction event.
Secondary Markers:
Foraminifera:
The first appearance of Paleogene foraminifera occurs at the base or within a few centimeters of the boundary clay, for example FAD of Globoconusa conusa.
Stable Isotopes:
A negative δ13C shift is found in marine calcareous plankton of low and middle latitudes (fine fraction or planktonic foraminifera).
Correlation Events:
Iridium geochemical anomaly. Associated with a major extinction horizon (dinosaurs, ammonites, foraminifers, etc.)
Notes on Derivation of Age:
Ar-Ar age suite. However, U-Pb ages are reported to be slightly older than 66 Ma
References:
Keller, G., Li, L., and MacLeod, N., 1995. The Cretaceous/Tertiary boundary stratotype section at El Kef, Tunisia: how catastrophic was the mass extinction? Paleogeography, Paleoclimatology, Palaeoecology 119, p. 221 - 254.
Bensalem, H., 2002. The Cretaceous-Paleogene transition in Tunisia: general overview. Paleogeography, Paleoclimatology, Palaeoecology 178, p. 139 - 143.