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.