Research-paper
Carbon isotope-, bio- and magnetostratigraphy across the Cretaceous-Tertiary boundary in the Zin Valley, Negev, Israel
Magaritz, Mordechai; Moshkovitz, Shimon; Benjamini, Chaim; Hansen, Hans Jorgen;Hakansson, E.; Rasmussen, K. L.
BibTeX file
RIS bibliography file
Abstract (German)
Zusammenfassung. Aus der mergeligen Taqiye Formation des Zin-Tales (südliches Israel), welche den Grenzbereich Kreide-Tertiär umfaßte wurden aus zwei Profilen in engem Abstand Proben auf Kohlen- ...
Abstract
Closely spaced samples from two sections of the marly Taqiye Formation in the Zin Valley (southern Israel), containing the Cretaceous-Tertiary (K/T) boundary, have been analyzed for carbon and oxygen isotopes, nannoplankton and planktonic foraminiferal assemblages, and for magnetostratigraphy. The studied sections lack a clay concentration at the boundary ('boundary clay'). The Hor HaHar (HH) section has a transitional biostratigraphic sequence across the K/T boundary. Approach of the boundary is heralded within the Cretaceous first by appearance of the planktonic foraminifer 'Globigerina' eugubina, appearing in samples containing otherwise entirely Cretaceous foraminiferal and nanno-species, some 1.20 m below the level of extinction of most Cretaceous foraminiferal taxa. Above the extinction level, the other Tertiary species of foraminifera and nannofossils gradually make their first appearence. Beginning from below the extinction level itself, at about the same level as the eugubina FAD, there is a gradual decrease in delta13C values, in CaCO3 of nannoplankton origin, from high values characteristic of the Late Cretaceous to the lower Early Tertiary values. This gradual depletion at the base of the Tertiary is a unique occurrence, and was measured in nannofossil-derived CaCO3 from species usually found only in the Cretaceous. As the upper part of the zone of decrease is from the Tertiary, the nannofossils, still of Cretaceous aspect, contributing CaCO3 at that level, must fall into the category of 'survivors'. The 'Ein Mor (EM) section shows a steeper decrease in delta13C than at HH, and in that respect is more like in other K/T sequences in the western Tethyan region. The gradual decrease of delta13C at HH, together with the biostratigraphic data and the magnetostratigraphy, strongly suggests that the HH site was the locus of continuous or nearly continuous deposition, while the EM section may have had a slight hiatus. In this region, planktonic foraminifera and calcareous nannofossils evolved gradually, in a deep shelf environment partially isolated from the open Tethys.