PALYNOLOGICAL EVIDENCE FOR EPICONTINENTAL DRY SUBTROPICAL TO TEMPERATE CLIMATIC CONDITIONS DURING THE EOCENE IN THE SOUTHEAST MEDITERRANEAN

Palynological analysis was carried out on five outcrop samples from the Bartonian (middle Eocene) Sannor Formation exposed at Gebel El-Goza El-Hamra in the Shabrawet area, Egypt. These samples cover about 40 m of section representing floodplain-dominated alluvial deposits comprised mainly of mottled mudstone with alternations of sandstones and conglomerates. Such sedimentary facies, especially in arid areas like Egypt, are not known for good preservation and production of fossil palynomorphs. Therefore, the present record, which is first of its kind, provides invaluable information about the depositional environment of the studied section as well as the Bartonian climate in the southeast Mediterranean.

Opaque phytoclasts dominated the recorded particulate organic matter (POM) components, which contain minor amounts of degraded phytoclasts and palynomorphs. This POM association reflects (1) oxidizing depositional paleoenvironmental controls that selectively destroyed the majority of less resistant organic particles, leaving only few types of POM, and/or (2) organic-poor facies in an area characterized by patchy vegetation, similar to the present day arid/desert conditions.

Identified palynomorphs include Momipites coryloides, Triatriopollenites triangulus, Pinuspollenites, and pollen similar to those of the family Amaranthaceae. M. coryloides is derived from wind-pollinated angiosperm trees of the Engelhardia-Oromunnea-Alfaroa complex (Juglandaceae). Pinuspollenites are produced by the well-known evergreen, conifer trees of the gymnosperm family Pinaceae. In contrast, angiospermous pollen grains of T. triangulus (Myricaceae) and those of the family Amaranthaceae are usually produced by small trees, herbs, and shrubs. This pollen association represents a woodland-savanna ecosystem subject to dry subtropical-temperate climatic conditions. The prevailing low moisture habitat probably prevented the woodland from fully developing and diversifying, providing a good opportunity for the herb/shrub community to grow and spread. This scenario, combined with the oxidizing conditions, explains the absence of embryophytic spores in all the analyzed samples.