Extensional strain and displacement distribution due to mesoscale normal faults in Late Miocene-Pliocene sedimentary rocks along the northwestern side of the Red Sea, Egypt

Abstract

Field observations are presented on the NW-SE mesoscale, dip-slip, normal faults in the Late Miocene–Pliocene sedimentary rocks, along the northwestern part of the SW side of the Red Sea, Egypt. These faults were initiated parallel to the Red Sea, and were originated by the NE-SW extension associated with the Red Sea opening in the Late Oligocene-Early Miocene time. About 100 mesoscale normal faults were measured in the Late Miocene-Pliocene sedimentary rocks along seven scan-lines. The extensional strain determined in five scan-lines ranges from 2.6393 to 5.12% with an average of 3.53145%. The other two scan-lines have anomalous values of 6.2988 and 15.53%. The represented data demonstrate that the extensional strain varies significantly from profile to profile and even along the fault because of several surficial factors. The first factor is a difference in lithology. The second and third factors are the local stress and the difference between perpendicular to the direction of maximum lateral extension of area and strike of faults. The L-D (Length-Displacement) diagrams along twelve selected faults reveal three patterns. These patterns include a cone-shaped (C-type), meso-shaped (M-type), and a zigzag-shaped (Z-type). The remarkable variation of displacement (D) along the fault plane (L) is a result of the difference in lithology, and/or the overlapping fault segments, as well as the local stress along the faults.