Palynology and age of the lower cretaceous basal kurnub group from the coastal plain to the northern Negev of Israel

Abstract

The spores and pollen from the basal Cretaceous Helez Formation in the Kokhav 2 well from the coastal plain of Israel have been studied and compared with those from the basal Cretaceous in the Zeweira Formation of the Zohar 1 well from the northern Negev of Israel. All sediments in the Early Cretaceous are within the Kurnub Group. The spores and pollen from the Oxfordian‐Callovian Kidod Formation in the Zohar 1 well were also studied and compared with the above Cretaceous assemblages. Thirty‐five core samples from four wells have yielded 91 distinct sporomorphae. One new form genus, Retimonoporites, and three new species ‐ Retimonoporites operculatus, Bullasporites bifidum, and Cicatricosisporites negevus ‐ are erected. The palynological data were analyzed and assemblage differences between the Kidod, Helez, and Zeweira formations presented. The microflora from cores in the Helez 1 and 3 wells that had previously been dated with marine microfauna is compared with the microflora from the basal Cretaceous in the Kokhav 2 well (coastal plain) and the basal Cretaceous in the Zohar 1 well (northern Negev).

All samples from the Lower Kurnub Group in the coastal plain that had previously been dated as Valanginian to Hauterivian, using marine microfauna, contain a spore and angiosperm pollen assemblage that is quite different from those assemblages found in the basal Kurnub from the northern Negev. The angiosperm pollen in the Valanginian to Hauterivian horizons are extremely rare, typically small, microreticulate, columellate, round, and inaperturate to weakly monosulcate. The angiosperms in the basal Kurnub from the Negev have more advanced monosulcates and some rare tricolpates that suggest a late Barremian to Early Aptian age. A new model for the morphological development of the earliest angiosperm pollen is proposed. It appears then that there is a 10–15 million year gap between the deposition of the initial shallow marine and lagoonal deposits of the Kurnub Group along the present day coastal plain of Israel and the oldest Cretaceous in the northern Negev. The younger age of the basal Cretaceous in the northern Negev indicates that a transgression of the Tethys Sea took place from west to east during the Early Cretaceous.