التطور الترسيبي و الباليوجغرافي لتشكيلة الكوراشينا دولوميت في حزام الطي التدمري في سورية

الملخص EN

This research aims to study the sedimentary and palaeogeographic evolution of the Kurachina Dolomite Formation along Palmyrian belt zone.

Studying this formation in its Northern and Southern parts has shown that it consists of two lithostratigraphic members, where each of them includes a series of lithological units.

The petrological study of the components of these units shows that they are composed of four distinguished facies: Dolomitic limestones, clayey limestones, clays and anhydrites, pure or mixed, and deposited in repeated harmonic layers, gathered mostly in neutral sedimentary sequences.

Dolomitic limestones are the most common and important facies, they are composed of micrite muds which have been subjected, in different degrees to synsedimentary or late dolomitisation processes through pumping or burial mechanisms.

Dolomitisation intensity decreases downward the formation and increases laterally from the south to the north of the Palmyrian chain.

The definition of the sedimentary variables, physical and chemical parameters of the principal facies allowed the deduction of sedimentary environments of each one along an evolution starting from basin subtidal deep sea environments which grades to less open tidal environment belonging to the marine platform.

Then it ends by confined supratidal and shallow environment belonging to lakes, coastal lagoons and playa.

Depth changes within the same environment due to continuous fluctuations of the eustatic sea level leading to local changes in the deposit base level.

The formation sediments have deposited in three palaeogeographic phases.

The first and second were characterized by the continuity of the Tethys transgression coming from the east and north east and during which the sediments of the lower member have settled, whereas the third phase has been characterized by un evident regression towards the south west leading to the upper member sediments deposition.

These two phases gave the Kurachina Dolomite Formation in the Palmyrian basin the aspect of a sedimentary megacycle.