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| Titel |
First Paleomagnetic Map of the Easternmost Mediterranean Derived from Combined Geophysical-Geological Analysis |
| VerfasserIn |
Lev Eppelbaum, Youri Katz |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250088327
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| Publikation (Nr.) |
 EGU/EGU2014-2424.pdf |
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| Zusammenfassung |
| he easternmost Mediterranean is a tectonically complex region evolving in the long term and
located in the midst of the progressive Afro-Eurasian collision (e.g., Ben-Avraham, 1978;
Khain, 1984). Both rift-oceanic systems and terrane belts are known to have been formed
in this collision zone (Stampfli et al., 2013). Despite years of investigation, the
geological-geophysical structure of the easternmost Mediterranean is not completely known.
The formation of its modern complex structure is associated with the evolution of the
Neotethys Ocean and its margins (e.g., Ben-Avraham and Ginzburg, 1990; Robertson et al.,
1991; Ben-Avraham et al., 2002). The easternmost Mediterranean was formed during the
initial phase of the Neotethys in the Early and Late Permian (Golonka and Ford, 2000;
Stampfli et al., 2013). At present this block of the ocean crust situated in the northern part of
the Sinai plate (Ben-Avraham, 1978; Eppelbaum et al., 2012, 2014) is object of our
investigation.
The easternmost Mediterranean region has attracted increasing attention in connection
with the recent discoveries of significant hydrocarbon deposits in this region (e.g.,
Montadert et al., 2010; Schenk et al., 2010; Eppelbaum et al., 2012). For example,
Schenk et al. (2010) consider that more than 4 trillion m3 of recoverable gas is
available in the Levant Basin (which located in the central part of the easternmost
Mediterranean).
Currently seismic prospecting is the main tool used in hydrocarbon deposit discovery.
However, even sophisticated seismic data analysis (e.g., Hall et al., 2005; Roberts and Peace,
2007; Gardosh et al., 2010; Marlow et al., 2011; Lazar et al., 2012), fails to identify the full
complex structural-tectonic mosaic of this region, and more importantly, is unable to clarify
its baffling complex tectonic evolution. This highlights the need for combined analysis
of geophysical data associated with the paleomagnetic and paleobiogeographic
conditions that can yield deep paleotectonic criteria for oil and gas discovery in this
region.
Extensive geological-geophysical investigations have been carried out in this
region, and a significant number of deep boreholes have been drilled. However
integrated estimation of the deep structure of the hydrocarbon host deposits and
their space-time evolution in terms of the modern geodynamics (first of all, plate
tectonics: Ben-Avraham and Ginzburg, 1990; Robertson, 1998; Ben-Avraham et
al., 2002, 2006; Jimenez-Munt et al., 2003; Le Pichon and Kreemer, 2010), are
comparatively recent (Eppelbaum and Katz, 2011, 2012a; Eppelbaum et al., 2012,
2014).
We elucidate this geodynamic relationship by examining the structural floors within the
following tectonic-geophysical zones: (1) regions of development of continental crust of the
Nubian, Arabian and Sinai plates, (2) remaining oceanic crust of the eastern Mediterranean,
and (3) the thinned continental crust of the terrane belt. A series of new gravity and magnetic
maps developed by employing satellite and airborne data (as well their transformations)
accompanied by tectonic schemes were constructed (Eppelbaum and Katz, 2011; Eppelbaum
et al., 2012a, 2012b, 2014). These new maps are crucial to a better understanding of the
dynamics of hydrocarbon basin formation within the continental and shelf depressions, as
well as the deep depressions of the easternmost Mediterranean where gas deposits
in zones of oceanic crust evolution have only recently (April 2013) begun to be
exploited.
Careful attention should be paid to the blocks of oceanic (basaltic) crust with reverse
magnetization that were discovered (Ben-Avraham et al., 2002; Eppelbaum, 2006). This
issue was very briefly (Eppelbaum and Katz, 2012a) explained as paleomagnetic
Kiama zone of inverse polarity and demands separate consideration. An integrated
magnetic-gravity-seismic analysis conducted along three interpretation profiles
unambiguously indicates the presence of blocks of the Earth’s crust with reverse
magnetization (Ben-Avraham et al., 2002). The results of 3D magnetic field modeling
(advanced GSFC program was applied) along three profiles, enabled to detect a boundary
between continental and oceanic crust. A reconstruction of the position of a reverse
magnetized block of Earth crust enabled to obtain a magnetization zone with a S – N
orientation and width reaching 70 km and length – about 200 km. Such a large, thick
(about 10 km) zone of inverse magnetization must correspond to the significant and
prolonged effect of inverse polarity in the Earth’s magnetic field history. We suggest
that this is the Kiama zone of inverse polarity that was first detected in the Late
Carboniferous and Permian in Australia (Irving, 1966). Subsequent investigations
(e.g., Khramov et al., 1974) have shown that the Kiama hyperzone underlies and is
covered by zones of alternating polarity; i.e., Donetzk and Illawarra, respectively.
According to zircon chronology the Kiama hyperzone extends over a period of 312–265
Ma (Khramov and Iosifidi, 2012), and according to K-Ar, 40Ar/39Ar and various
historical planetology methods this period extends of 293-242 Ma (Lapkin and Katz,
1990).
Delineation and mapping of the Kiama reverse paleomagnetic zone on the basis
of 3D combined modeling of magnetic and gravity fields creates a necessity for
attraction of wide spectrum of other geophysical-geological data for substantiation
of space-tectonic position of this zone. Practically this is a first real evidence of
delineation such an ancient oceanic crust of the Late Paleozoic. On the basis of
investigation of Mediterranean ophiolites of the Alpine belt, the most ancient crust of the
eastern Mediterranean corresponds to Late Triassic – Jurassic (Robertson et al.,
1991).
According to the latest paleogeodynamic reconstructions (Stampfli et al., 2013), the
Alpine belt is a complex structure and includes structures associated with Neotethys and
Paleotethys oceans and with more ancient oceans. It is considered that the northern part of the
Neotethys has been developed as active zone of the arc island tectonics, and southern part is
bounded with Gondwana, belonged to the passive tectonic conjunction. Usually forming of
the initial rift of the Neotethys Ocean in the east was presented as a common basin
formed in the Early Permian, and in the west – as a collection of small rift basins
which began to form after breakdown of the Hercynian fold belt. However, the
easternmost Mediterranean does not correspond to any of these schemes. Earlier
was considered that the oceanic crust was formed here as a result of movement to
north a continental Tauride-Anatolian block. However, these constructions did not
take into account earlier published paleomagnetic data (Robertson et al., 1991;
Scotese, 1991). The modern paleogeodynamic reconstructions testify to position of the
Tauride-Anatolian block in other place – in the northern side of the Paleotethys (Stampfli et
al., 2013).
The performed integrated geological-geophysical analysis (Katz and Eppelbaum, 1999;
Eppelbaum, 2006; Eppelbaum and Katz, 2011, 2012a, 2012b; Eppelbaum et al., 2012, 2014) |
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