Figure 6. Satellite image analyses of the study area from west of the
Rusayl Embayment to the Batain area. The study area is divided into
eight sub-areas to potentially reveal local/regional variations in
orientation of the lineamentary features (areas 1-8, separated by the
red dashed lines). The orientations of the lineaments (light blue lines)
from the satellite image are plotted in the rose diagrams (Jenness,
2014), with a bin size of 5°. All measurements are plotted in the rose
diagram at the upper right. N=number of measured linear features;
Maximum Values is the total length (in meters) of all measured
lineaments.
4.3 Map analysis
This section summarizes previously mapped ~N/S-oriented
compressive structures, ~E/W-oriented normal faults and
~NW-striking sinistral faults within eastern Oman (Figs.
7 and 8; Table 1). These structures affect mostly Paleocene/mid-Eocene
sedimentary rocks but also some Miocene rocks, especially near the
Qalhat Fault. Besides the mappable features, Wyns et al. (1992) measured
sub-horizontal stylolite axes within Cenozoic carbonates, including
those of the Oligocene Shama Formation near the Qalhat Fault. Stylolite
axes are oriented ENE-WSE and interpret as axes of maximum compression
during the Miocene (Wyns et al., 1992).
4.3.1. Folds
N/S to NW/SE-oriented folds within the post-obductional formation in the
Muscat-Seeb area and the Permian rocks of the Saih Hatat Dome have been
reported by Le Métour et al. (1986a), Villey et al. (1986a, 1986b), Mann
et al. (1990), Miller et al. (2002), Kajima et al. (2012a, 2021b,
2021c), Scharf et al. (2016), Searle et al. (2019), Hansman et al.
(2021) and Levell et al. (2021), and are summarized in Table 1. Traces
of fold axes are shown in Figure 7. The respective folds deform
stratigraphic units up to the mid-Eocene limestone of the Seeb
Formation. Mapped folds are open to tight and display sub-vertical fold
axial planes. Fold axes plunge gently towards the north to NW or are
sub-horizontally. The interlimb angle of individual folds within the
Rusayl Embayment varies. Towards the South, the same fold elements
(synclines/anticlines) are tighter then in the North, where the folds
open (Mann et al., 1990). Interlimb angles are homogeneous along
individual folds outside the Rusayl Embayment.
Ninkabou et al. (2021) and Levell et al. (2021) presented seismic and
well data from offshore northereastern Oman. A pre-late Eocene
NNE-trending major fold has been spotted by Levell et al. (2021). This
fold occurs in the NNE-ward projected extension of the Jabal
Akhdar/Jabal Nakhl. Further ~N/S-trending folds extend
from the Rusayl Embayment into the Sea of Oman and near Muscat. Rabu et
al. (1986) and Coffield et al. (1990) mapped several Cenozoic
~N/S to NNW/SSE-trending faults in the Fanja area
between the Jabal Akhdar and Saih Hatat domes as well as along the
Frontal Range Fault and the Wadi Mansah Fault (Fig. 7).
Approximately N/S-oriented open to tight folds have been mapped within
Paleocene to Miocene formations near Quriyat, in the Salma Plateau and
Batain area (Le Métour et al., 1986a, 1986b; Roger et al., 1991; Wyns et
al. 1992; Peters et al., 2001). Further ~N/S-oriented
open asymmetric folds and monoclines deformed Maastrichtian to Eocene
rocks at Jabal Ja’alan (Filbrandt et al., 1990). The traces of some of
these folds are depicted in Figure 8.
4.3.2 Faults
Fournier et al. (2006) mapped sets of conjugate strike-slip faults
within the Jafnayn Formation in the Muscat area (Figs. 7 and 8). Dextral
and sinistral faults strike NE/SW and E/W, respectively (Fournier et
al., 2006). The computed maximum horizontal stress trends ENE/WSW
(between N54°E and N85°E; Fournier et al., 2006).
A segment of the Paleogene rocks, including the Jafnayn, Rusayl and Seeb
formations at the “Tertiary Ridge” at Al Khod Village represents a
WNW-striking transpressive sinistral shear zone with
~N/S-oriented compressive structures (folds and reverse
faults) and ~E/W-striking normal faults (Scharf et al.,
2016). The horizontal shorting direction was ENE/WSW (Scharf et al.,
2016).
In the Sunub area of the Rusayl Embayment and near the Frontal Range
Fault, the well-exposed WNW-striking sinistral transtensional Sunub
Shear Zone associated with ~E/W-striking normal faults
exists. It has been interpreted as a negative flower structure with a
shale dike (Mattern et al., 2018c).
The southwestern margin of the Saih Hatat Dome and the Fanja area is
characterized by the Wadi Mansah Fault Zone (Bailey et al., 2019; Scharf
et al., 2019a). This major extensional shear zone has a throw of ≤7 km
and a sinistral shear component. It has been interpreted as active
during doming of the Jabal Akhdar and Saih Hatat domes during the late
Eocene to Miocene (Scharf et al., 2019a). The southeastern extend of the
Wadi Mansah Fault Zone is parallel to the margin of the Saih Hatat Dome
and merges with the extensional Wadi Tayin Fault of Searle (2007). The
latter has a throw of ~2 km (Searle, 2007). Numerous
~WNW-striking faults in the Fanja area affected
autochthonous and allochthonous rocks (Stanger, 1985).
Within the Semail Ophiolite, parallelly orientated to the Wadi Mansah
Fault Zone and near the Wadi Tayin Fault, a further sinistral
transtensional fault zone is present – the Issmaiya Fault Zone
(Callegari et al., 2020). This ~NW-striking shear zone
is ~30 km long and ~3 km wide. Activity
along this fault zone occurred first during the Maastrichtian to early
Eocene and then following the mid-Eocene (Callegari et al., 2020).
The Salma Plateau, including mid-Eocene limestones, has been affected by
numerous faults of the NW-striking sinistral transpressive Coastal
Parallel Shear Zone (Wyns et al., 1992; Moraetis et al., 2018).
Sinsitral slip was determined by Roger et al. (1991) and Wyns et al.
(1992).
In the southeastern prolongation of the Issmaiya Fault Zone, the
NW-striking Ja’alan Fault is exposed (Roger et al., 1991; Wyns et al.,
1992; Fig. 8). This fault is a present-day major reverse fault with a
sinistral component (Filbrandt et al., 1990; Wyns et al., 1992). The
throw amounts to a few kilometers. The Ja’alan Fault marks the
southwestern limit of the Salma Plateau (Fig. 2).
The ~N/S-striking Qalhat Fault is located near Sur and
defines the eastern margin of the Salma Plateau (Fig. 2). The throw
along the major fault amounts to a few to several kilometers, where the
Neoproterozoic crystalline basement was thrust onto Oligocene/Miocene
sedimentary rocks (Wyns et al., 1992). Adjacent to the Qalhat Fault are
several ~N/S-oriented folds (Roger et al., 2001). The
rocks east of the Qalhat Fault were not uplifted, while the same
Cenozoic rocks to the West have been uplifted to an elevation of
>2000 m.