Published December 2009

The geodynamic development of Front Minor Caucasus cavity and oil-gas perspectives of Mesozoic accumulations

Y.Y.Pogorelova

The Front Minor Caucasus cavity by tectonic views is a transitional stripe from Minor Caucasus to Kura hollow and is the zone of south-west side of Middle Kura cavity and far north wing of Minor Caucasus megaanticline . The Front Minor Caucasus cavity is sharply disjointed by juts and cavities of second order the anti-Caucasus direction and it has the zigzag form. This peculiarity of tectonics of considering region has been appeared in Later Pliocene-Anthropogenic epoch when all area of Middle Kura cavity was considerable bowing and drawn the adjacent zones of folded areas Great and Minor Caucasus. There are border zones in the structure of Middle Kura cavity have being on Mesozoic-Paleogene geosyncline foundation and internal zone – on Mesozoic-Paleogene plate foundation. The studing of geodynamic development history will help to show how these two zones have been connected . There was ocean basin on the researching territory at the Later Proterozoic-Early Paleozoic period. The most of territory of Trans-Caucasus and North Iran have risen and denuded as result the Baycalian folding. This complex of metamorphic rocks into Azerbaijan has consisted the Trans-Caucasian microcontinent. Into border of Trans-Caucasus there was Paleothetis ocean with south and north branch which was inherited from Later Proterozoic ocean. During Caledonian-Hercynian period all the center part of Azerbaijan was a Trans-Caucasian microcontinent which on the Hercynian stage was undergone the intensive kalium-granitic magmatic flow, which did the final formation of continental crust. At the Later Triassic period was opened the cardinal ocean Thetis and, as consequence, was closed the south branch of Paleo thetis ocean. During opening a Thetis ocean the Iranian plate has start moved from south to north, by directly to Dzirullian microcontinent and pushed the Trans-Caucasian microcontinent to North. The Front Minor Caucasus cavity as all Somkhit-Aghdam (Lock-Karabakh) zone of Minor Caucasus geosyncline on Mesozoic development stage had founded into object of Trans-Caucasian microcontinent. There was a cavity by en-sialic foundation with. In Early Jurassic period the Lock- Karabakh plate has been to 22Оn.l., in Bajocian age – to 23,5 Оn.l., in Bathonian age – to 27 Оn.l. In Bathonian age the North branch of Paleo thetis was closed. Since Bathonian age the Front Minor Caucasian part of Kura megacavity is drawn as cavity. In the end of Jurassic period, in the Tithonian age, was happened a sea transgression and started reef-building At further all these thinks create favourable conditions for hydrocarbon generation to form the great oil-gas zones. After Later Jurassic stage of rift-building the determinate movement again became the Hondwanah movement to North. This process has narrowed the ocean that was on the South from Lock-Karabakh block and removed it North direction. In early Cretaceous it has been to 25Оn.l. This changing of direct movement of Lock-Karabakh block has obliged to enough the rift-building into boundary of Black sea and Kolkhida cavity. The main movement is shortening the Meso thetis ocean into Minor Caucasus branch and movement the Iranian plate to North. In Later Cretaceous the Lock-Karabakh block by leap has moved again to South on 20,5Оn.l., because there was a new cycle of rift-building in Black Sea - Caspian Sea megacavity. But this process didn’t drag the granitic layer. It was a continental rift-building, but totally these happenings has moved the Lock-Karabakh plate to South. The Hondvana’s movement to North has became determining again in Paleocene-Eocene epoch and it pushes a Lock-Karabakh microplate same direct with. In Paleocene it is on 29Оn.l., in Eocene – on 37О n.l., and goes on the movement up to modern position - 40Оn.l. Since Oligocene epoch is started orogenic period of development of folding area. This is happened on 40О n.l., where is located a Minor Caucasus now. In Maykop age this territory is developed as inherited from Paleocene-Eocene plane as changed ctructure plane. On Maykop stage the west and central parts of cavity was the zone of denudation as drawn up to rising of Minor Caucasus. There is no Front Minor Caucasus cavity in Miocene as this was a far border part of Yevlakh-Aghjabedi cavity, is bordering with rising block a Minor Caucusus. On Early Pliocene stage at the Front Minor Caucasus cavity was a gentle folding of Paleogene-Miocene layers. Early Ackchagil transgression was changed a Later Ackchagil sea regression which uncoupled it from ocean. In Apsheron age is gone on the sea regression from Later Ackchagil age. In Quarternary period the front mountain plain is turned to inclined plain. There hadn’t diffused Khvalin and New-Caspian transgression on researching area. By plate’s tectonics, a Front Minor Caucasus cavity as Minor Caucasus front zone which was formed over subduction zone of Thetis ocean under Trans-Caucasian microcontinent is possessed of high hydro-carbonate potential. By statistics 80% world hydrocarbon supplies are over subduction zones. In the researching area oil-gas deposits will be find at the Santonian-Maastrichtian interval of Cretaceous because since Santonian age still finish of Cretaceous period it was persistent accumulation of deposits with favourable geo-chemical conditions for oil-gas carbo-hydrates. So in the researching area more perspective are considered the Kazanbulagh, Shirvanli, Sovetlar areas.