--> Abstract: Relations between Tectonic Zones of the Albanides on the Basis of Results of Geophysical Studies, by A. Frasheri; #90990 (1993).

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FRASHERI, A., Polytechnic University, Tirana, Albania

ABSTRACT: Relations between Tectonic Zones of the Albanides on the Basis of Results of Geophysical Studies

The Albanides are located between the Dinarides of Yugoslavia and the Hellenides of Greece, which together form the southern branch of the Mediterranean Alpine Belt. Our analysis of the Albanides and their extension into the Adriatic Sea integrates surface geological observations, well data, and results of seismological, reflection-seismic, gravity, magnetic, and geoelectric surveys.

Evolution of the Albanides began with the Triassic subsidence of their Hercynian substratum under a tensional regime, culminating in crustal separation and opening of the Hellenic-Dinaride oceanic basin. The Alpine orogenic history of the Albanides spans Late Jurassic to Quaternary and can be subdivided into four major cycles: paleotectonic (J3-Cr1), tectonic (Cr2-Pg2), tarditectonic (Pg3-N1) and neotectonic (N2-Q).

The Albanides consist of two major paleogeographic domains. The internal Albanides (IA) formed part of the oceanic Hellenic-Dinaride Basin, whereas the external Albanides (EA) developed out of the westward adjacent passive margin and continental shelf of the Adriatic plate. During the paleotectonic phase, oceanic crust of the IA was obducted onto the margin of the Adriatic plate. This was accompanied by the development of a synorogenic foredeep basin. During the tectonic, tarditectonic, and neotectonic phases, progressive westward advance of the orogenic front was coupled with a westward shift of the foredeep basin axis to its present location in the Adriatic. The EA evolved out of a shelf and continental margin sedimentary prism and a superimposed foredeep wedge, which together form he Alpine-deformed hydrocarbon-bearing Albanian Sedimentary Basin.

The ophiolites of the IA give rise to gravity and magnetic anomalies, which indicate that their thickness increases northeastward from 2 km to 6-14 km. Reflection-seismic and gravity surveys done in the EA and the Adriatic Sea define distinct structural belts that are related to different tectonic zones of the Albanian Sedimentary Basin. From a tectonic point of view, the oil and gas bearing zones are characterized by a two-stage structuration.

The most important oil and gas accumulations are found in the Jonian zone and in the Periadriatic depression, which extends into the Adriatic offshore. The carbonate-dominated Late Triassic to Late Cretaceous series of the lonian, Kruja, and Krasta-Cukali zones contains several rich to very rich source rock intervals. In the lonian zone, Late Cretaceous, Paleocene, and Eocene carbonates and Oligocene-Miocene flysch-type sandstones form the reservoirs of the main oil and gas accumulations. The Tortonian-Pliocene Molasse-type clastics of the Periadriatic depression contain also source rocks and mainly stratigraphically trapped gas accumulations.

AAPG Search and Discovery Article #90990©1993 AAPG International Conference and Exhibition, The Hague, Netherlands, October 17-20, 1993.