Paleostress reconstructions of Jabal Hafit structures, Southeast of Al Ain City, United Arab Emirates (UAE)

Abstract

This paper presents the first paleostress results obtained from displacement and fracture systems within the Lower Eocene sediments at Jabal Hafit, Abu Dhabi Emirate, UAE. Detailed investigation of Paleogene structures at Jabal Hafit reveal the existence of both extensional structures (normal faults) and compressional structures (strike-slip and reverse faults). Structural analysis and paleostress reconstructions show that the Paleogene kinematic history is characterized by the succession of four paleostress stages. Orientation of principal stresses was found from fault-slip data using an improved right-dihedra method, followed by rotational optimisation (TENSOR program). The paleostress results confirm four transtensional tectonic stages (T1–T4) which affected the study area. The first tectonic stage (T1) is characterized by S Hmax NW–SE σ 2-orientation. This stage produced NW–SE striking joints (tension veins) and E–W to ENE–WSW striking dextral strike-slip faults. The proposed age of this stage is Early Eocene. The second stage (T2) had S Hmax N–S σ 2-orientation. N–S striking joints and NNE–SSW striking sinistral strike-slip faults, E–W striking reverse faults and N–S striking normal faults were created during this stage. The T2 stage is interpreted to be post-Early Eocene in age. The third stage (T3) is characterized by S Hmax E–W σ 2-orientation. This stage reactivated the E–W reverse faults as sinistral strike-slip faults and created E–W striking joints and NE–SW reverse faults. The proposed age for T3 is post-Middle Eocene. During the T3 ( S Hmax E–W σ 2-orientation) stage the NNW-plunging Hafit anticline was formed. The last tectonic stage that affected the study area (T4) is characterized by S Hmax NE–SW σ 2-orientation. During this stage, the ENE–WSW faults were reactivated as sinistral strike-slip and reverse faults. NE–SW oriented joints were also created during the T4 ( S Hmax NE–SW σ 2-orientation) stage. The interpreted age of this stage is post-Middle Miocene time but younger than T3 ( S Hmax E–W σ 2-orientation) stage.