Fracture Analysis at St. Paul Monastery, Egypt: Insight into the Tectonic History of the Gulf of Suez

By

 Andrew J. Rich¹, John D. Pigott¹, Sherief Sadek², Hansel Gonzalez¹, Kulwadee L. Pigott¹

(1) University of Oklahoma, Norman, OK (2) Cairo University, Cairo, Egypt

 In an attempt to interpret the paleostress history of the western Gulf of Suez, detailed fracture analysis were conducted at three measurement stations on the St. Paul Monastery grounds west of the main Red Sea highway. The study was conducted in the Albian Malha Formation sandstone, the Cenomanian Galala Formation limestone, and the Santonian Matulla Formation chalk. The fracture orientation data reveal multiple yet indistinct populations when viewed as conventional stereoplots and rose plots. However, a signal analysis approach is revealing when: (1) populations are separated using cluster analysis which reveal the level of similarity between populations at each measurement station; (2) fast Fourier and inverse fast Fourier transforms are performed on the data for frequency and pulse-width analyses; (3) cross-correlations between the stations are conducted in order to determine differences in population phase; (4) the data between stations are deconvolved in order to show what data are unique to each; (5) population breadth is determined through the calculation of spherical variance; and (6) construction of paleostress tectonic history using earthquake pseudo-focal mechanisms constructed from the fracture data. The analysis reveals at least three distinct local tectonic events to have affected the rocks at the St. Paul Monastery, with probable fracture reactivation during successive events. The three main fracture populations present are: (1) a Cretaceous NE to WNW trend (2) a mainly Eocene trend to the NNE, and (3) Eocene and younger NW trends.