Tertiary and quaternary marine terraces and planation surfaces of northern Oman: Interaction of flexural bulge migration associated with the Arabian-Eurasian collision and eustatic sea level changes

Ye Yuan,Timothy M Kusky,Sankaran Rajendran

doi:10.1007/s12583-015-0656-2

Ye Yuan, Timothy M Kusky + Show 1 more

https://doi.org/10.1007/s12583-015-0656-2

Copy DOI

Abstract

The northeastern Arabian passive margin is being subducted beneath the Zagros and Makran of Iran. A flexural bulge related to the weight of the Makran has migrated at 4 cm/a through the previously uplifted Hajar Mountains of Oman as this active convergence and collision between Arabia and Eurasia progresses, adding approximately another 500 meters of relief, and forming a series of uplifted marine terraces, alluvial terraces, and planation surfaces that record the passage of the bulge. We use a combination of field studies, remote sensing and GIS to map and better-understand these terraces, and elucidate how the tectonics of bulge migration, down-to-trench normal faulting, and eustatic sea level changes have interacted to produce the extant geomorphic features on the inner slope of the flexural bulge as it sinks into the foredeep of the Gulf of Oman. We speculate those terraces that were uplifted on the outer slope of the forebulge as it initially migrated through the passive margin (affected by ophiolite obduction in the Cretaceous) 3.75–7.5 Ma ago are now sinking on the inner slope of the forebulge (corresponding to the outer trench slope in the foredeep), and have been partly covered by Quaternary marine terraces related to a Weichselian sea level high stand. Both the Tertiary and Quaternary terraces are cut by faults related to the active collision, confirming that there is a significant risk of moderate earthquakes in the region.

Highlights

AND PREVIOUS RESEARCHThe Hajar Mountains of Oman and the United Arab Emirates (UAE) are located on a promontory on the NE margin of the Arabian Plate (Fig. 1), bounded to the SW by spreading ridges in the Red Sea and Gulf of Aden
The northern margin is marked by the collision zone between the Arabian Plate and Eurasia where Arabian continental crust is being subducted beneath the Zagros fold belt of Iran, and oceanic crust of the Arabian Plate is being subducted beneath the Makran depression
Kusky et al (2005) were able to show from a comprehensive program of mapping late faults, drainage networks, topography, and terraces that Tertiary–Quaternary structures and geomorphic features are related to the contemporaneous subduction and imminent collision with the Makran to the north. They showed that the axis of current uplift is about 150 km south of the active thrust front of the Makran, and that systems of NW and WNW striking faults are contemporaneous outer trench slope normal faults, whereas a system of NNE-striking faults are probably tear faults separating different fault blocks sliding into the trench. In this contribution we examine a series of marine terraces and planation surfaces in the Fins-Tiwi area identified by Kusky et al (2005) who suggested that they may represent marine terraces uplifted on the outer flank of the flexural bulge that are subsiding into the trench towards sea level on the outer trench slope

Summary

Introduction

The Hajar Mountains of Oman and the United Arab Emirates (UAE) are located on a promontory on the NE margin of the Arabian Plate (Fig. 1), bounded to the SW by spreading ridges in the Red Sea and Gulf of Aden. Its east and west boundaries are delineated by transform faults, the Owen fracture zone to the east and the Dead Sea transform to the west. The northern margin is marked by the collision zone between the Arabian Plate and Eurasia where Arabian continental crust is being subducted beneath the Zagros fold belt of Iran, and oceanic crust of the Arabian Plate is being subducted beneath the Makran depression. The boundary between continental and oceanic subduction is marked by the Dibba line-Zendan faultOman line (Fig. 1).

Methods

Findings

Discussion

Conclusion