John Filatoff

Stratigraphic palynology of Devonian boreholes from northern Saudi Arabia

This extended abstract describes well-preserved palynomorph assemblages recovered from Devonian strata in five shallow boreholes in the northern part of Saudi Arabia. These fully cored holes overlap stratigraphically to form a 1,640 ft composite section spanning the upper Tawil, Jauf and lower Jubah formations. Only the Jauf and lower Jubah, represented by 188 samples taken over a 1,300 ft stratigraphic interval, are addressed here as the sandy Tawil lithologies are unsuitable for palynological analysis. The 900 feet of alternating of siliciclastic and carbonate units, that together comprise the five members of the Jauf Formation, were sampled comprehensively. However, the Jubah Formation, like the Tawil Formation, is mostly sandstone and is productive palynologically at only two levels separated by a 300 ft barren interval. The age of the sampled succession is assessed using index species from the established Euramerican Devonian palynozonations of Richardson & McGregor (1986) and Streel et alii (1987), and is shown to span the late Early and Middle Devonian.

Late cretaceous to recent palaeoenvironments of the Saudi Arabian Red Sea

Abstract Integrated micropalaeontological, palynological and lithological analysis of the Upper Cretaceous to Recent sedimentary succession, as observed in deep and shallow well drill cores and field samples, has revealed a highly varied history of environments of deposition. Supratidal, freshwater conditions prevailed during the Late Cretaceous, Oligocene, Early and Late Miocene to Recent Marginal marine conditions are represented in the Palaeocene to Lower Eocene successions, but without any indication of hypersaline sabkha environments. Marginal marine conditions involving periodic hypersaline sabkha and hypersaline lake development existed during the Early and Late Miocene. In most of the studied areas, very deep, normal salinity marine conditions, within the upper bathyal regime, existed during the Early Miocene; episodes of marine suboxia are indicated by the microfaunal and organic facies character. Later, during the late Early Miocene and early Middle Miocene, similar deep marine conditions prevailed, but with episodes of hypersalinity that culminated in the late Middle Miocene. Such conditions are believed to have resulted from the isolated of the basin and the precipitation of deep marine precipitates. These changes in palaeoenvironment are considered to reflect episodes of eustatic sea level fluctuation, which are possibly linked to the structural evolution of the Red Sea.