Integrated Micro- and Biofacies Analysis: Basis for Carbonate Models and Sequence Stratigraphy of the Middle Eocene, Northern Egypt

Tawfik, Mohamed E.¹; Aigner, Thomas ¹; Ziko, Abdelmohsen ²; Elgamal, Mohram ³
(1)Geoscience, Geowissenshaft, Tübingen, Germany. (2) Geology Department, Zagazig University, Zagazig, Egypt. (3) Geoscientist, Cairo, Egypt.

It is the aim of this study to show how a very detailed and integrated micro- and biofacies analysis of Tertiary carbonates allows the reconstruction of (1) sophisticated facies models with a larger number of facies belts, and (2) a robust, high-resolution sequence stratigraphic framework.

The shallow-water carbonates of the Middle Eocene in northern Egypt represent a Tethyan reef-rimmed carbonate platform with, bedded inner-platform facies, characterized by stacked high-frequency cycles with subtidal to intertidal carbonate sequences. Based on an extensive micro- and biofacies documentation, fifteen lithofacies associations (LFA) were defined and their respective depositional environments (facies belts) were interpreted.

A sequence-stratigraphic analysis was carried out by integrating lithostratigraphic marker beds, facies relationships, stratigraphic cycles, and biostratigraphy. The investigated sections were subdivided into three third-order sequences, named S1, S2 and S3. S1, is interpreted to correspond to the late Lutetian stage (44-42.5 M.y), S2 corresponds to the early Bartonain stage (42.5-40.5 M.y), and S3 represents the late Bartonian stage (40.5- 39.5 M.y). Each of the three sequences was further subdivided into fourth order cycle sets and fifth-order cycles. The complete hierarchy of cycles can be readily correlated for 190 km across the study area, highlighting a general “layer-cake” stratigraphic architecture. The documentation of the studied outcrops may contribute to better regional understanding of the Middle Eocene formations in Northern Egypt and to Tethyian pericratonic carbonate models in general.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.