3-1- Geological Data
Based on limited geological data, Topuz et al. (2017) state that the
metamorphic rocks and the overlying ophiolitic layer of eastern Anatolia
were exhumed during the Late Cretaceous, above which the sediments of
Maastrichtian transgression were deposited. This view necessitates two
highly improbable consequences.
a)-the continental crust must have remained buried under the thick,
dense ophiolitic layer for more than 60-70 Ma period, which seems
physically highly unlikely, and does not fit with tectonic behavior of
the Alpine-Himalayan Mountain ranges,
b)-the stratigraphic data documented in Fig 3 display that the wholesale
elevation of the eastern Anatolia above the sea level occurred during
the Late Eocene-Oligocene. The bulk of eastern Anatolia became emergent
in Neogene (Şengör and Yılmaz 1981; Bedi and Yusufoğlu 2018; Okay et al
2020; McNab et al 2018).
Moreover, geological data from the neighboring orogenic belts, the
Pontide, and the Southeastern orogens reveal also that the oceanic
environment survived in these regions until the Middle Eocene (Dilek and
Sandvol 2009; Hassig et al. 2013; Nikishin et al. 2015; Sosson et al.
2017; Meijers et al. 2017; Yılmaz 2019, see also the accompanying papers
by Yılmaz et al. in this volume). Elevation of fragments of the
accretionary complex, reaching somewhere above the sea during the Late
Cretaceous-Early Eocene period does not rule out the ocean’s existence
in the region, similar to many growing accretionary prisms of the world
today, such as the Aegean-Eastern Mediterranean region (Robertson et al.
1996).
The hypothesis by Topuz et al. (2017) is based essentially on the
presence of the metamorphic inliers surrounded by the accretionary
complex located between the towns of Tekman, Hınıs, Karayazı and Aktuzla
(Figs 2 and 8A). They argue that these metamorphic assemblages represent
fragments of the elevated old metamorphic basement. The following
evidence questions validity of this hypothesis. Figure 8B illustrates a
geological cross-section along the largest metamorphic inlier (A-B
section in Fig 8 B). The cross-section and the aerial photos in Fig 8 C
and Figs 9 A and B show that the outcrops do not represent intact rock
masses. They are observed either as tectonic wedges imbricated with the
accretionary complex (Figs 9 A and 9 B) or as thrust sheets resting
above the ophiolitic mélange (Fig 8 A, B, and C).
Furthermore, the data summarized below do not favor the presence of an
old metamorphic basement under the ophiolitic mélange:
a)- The field evidence from the northern (the
Çayırlı-Tercan-Aşkale-Pasinler basins), central (the
Tekman-Hınıs-Malazgirt-Tekman basins), and southern (the
Muş-Bingöl-Gevaş basins) (Fig 2) regions of the East Anatolia,
particularly from the basin boundaries where the base rocks are exposed,
reveal that there is almost always an ophiolitic mélange under the
Neogene cover (Figs 3 and 5C).
b)- All the wells drilled by the oil and gas industry in the region
cutting through the Neogene succession penetrated the ophiolitic mélange
(unpublished TPAO data).