Master Thesis Surface and Subsurface Structural Analysis of Al-Burdia Area, the Eastern Part of Marmarica Uplift, NE Libya.

Abstract

Marmarica uplift extends approximately E-W along further the northeastern coastline of Libya and delimits the northeastern margin of Cyrenaica Platform. It is considered as structure inversion via the deformation of dextral strike-slip tectonics . Folds are recognized, based on their intensity and style, into three phases (F1, F2, and F3). F1 folds are the oldest and recorded in Al Majahir with Al Bayda formations. They recognized as overturned types with axis oriented approximately ENE-WSW and extends some of them for about 2km. F2 folds are developed at minor scale about 5.5km northwest of Al Burdia, in Al Faidiyah Formation. These folds are trending NE-SW with a general vergence SSE. Their styles are tight, overturned, open and asymmetric. F3 phase of folding is a major and represents the final phase of folding. It is plunging SW and ended by the present morphology of gentle and elongated folding during Oligocene to Miocene ages. Faults are most prominent in the study area and markedly concentrated in Al Burdia area and recognized by three main trends; the NW-SE dextral strike-slip faults (synthetic shears), N-S to NNE-SSW sinistral strike slip faults (antithetic shears), and E-W fault trends. Other array of the NNW-SSE normal faults are also encountered and run approximately perpendicular the folding axes. Kinematic indicators along these faults are documented in the field on the slickensides, flower structures, small scale of dextral and sinistral displacement, and pop up structure indicated that the sequence of faulting is initiated by pure wrenching and, in part, transpression in Late Cretaceous -Oligocene then continued with pure wrenching afterwards until the Miocene. Joints are distinguished into two types; shear and tensional joints. In the present area, the joints are regular and, sometimes, irregular and along their planes there are little or no displacements. Subsurface structural interpretation confirms the integration of surface structural analysis the inversion via strike-slip tectonics in Late Cretaceous