Quaternary Thrusting in the Central Oman Mountains—Novel Observations and Causes: Insights from Optical Stimulate Luminescence Dating and Kinematic Fault Analyses

Daniel Moraetis,Steven Forman,Andreas Scharf,Kosmas Pavlopoulos,Frank Mattern

doi:10.3390/geosciences10050166

Abstract

For the first time, Quaternary thrusts are documented within the Central Oman Mountains to the northwest of the Jabal Akhdar Dome. Thrusts with a throw of up to 1.1 m displace Quaternary alluvial fan conglomerates. These conglomerates have an Optical Stimulate Luminescence (OSL) age of 159 ± 7.9 ka BP and were deposited during MIS 6 (Marine Isotope Stage). The thrusts occur in two sets. Sets 1 and 2 formed during NE/SW and NW/SE shortening, respectively. Set-1-thusts correlate with the present-day stress field of NE/SW shortening which is related to subduction in the Makran Subduction Zone, and they strike parallel to the main continuous fold axis of the Jabal Akhdar and Hawasina windows. Set-2-thrusts correspond to NW/SE shortening and Plio-Pleistocene contractional structures in the southwestern Jabal Akhdar Dome. Set-2-thrusts are probably related to local variations of the present-day stress field originating from the Musandam area which is a part of the Zagros Collision Zone. Both thrust sets mimic the main thrust directions (NW/SE and NE/SW) within the Permo-Mesozoic allochthonous units (Semail Ophiolite, Hawasina napps) of the larger study area. The investigated thrusts imply some reactivation of the Hawasina and Semail thrusts due to far-field stress either from the Makran Subduction Zone and/or the Zagros Collision Zone. The ongoing tectonic activity of this part of the Oman Mountains, which has been considered of moderate activity, is for first time identified by structural data as contractional.

Highlights

Quaternary to recent tectonic deformation in the Oman Mountains has been documented in the Southeastern Oman Mountains through uplifted marine terraces [1,2,3]
A sub-recent alluvial fan occupies the area between the Murri Anticline in the west and the easterly adjacent Hawasina nappes and Semail Ophiolite within Wadi Bani Ghafir (Figure 2)
The present work reveals for the first time thrusting in Quaternary alluvial fan deposits from the Central Oman Mountains

Summary

Introduction

Quaternary to recent tectonic deformation in the Oman Mountains has been documented in the Southeastern Oman Mountains through uplifted marine terraces [1,2,3]. Oman Mountains (Nizwa area) reveal some limited but still detectable tectonic activity in northern. The Qalhat Fault near Sur (Figure 1), which belongs to a WNW-striking set of faults, seems to have triggered some recent earthquakes in the Southeastern Oman Mountains [7] According to [8], several faults cut through Quaternary conglomerates. This study is based on remote sensing techniques without presentation of kinematic fault data. There are neither accurate kinematic data nor absolute age constraints on recently active faults.

Methods

Results

Discussion

Conclusion