Petroleum Systems of Deep-Water Basins - Gulf Coast Section SEPM
Petroleum Systems of Deep-Water Basins - Gulf Coast Section SEPM
Petroleum Systems of Deep-Water Basins - Gulf Coast Section SEPM
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Transtension Along an Ancient Lineament:<br />
Example from the South Caspian Basin<br />
Ibrahim Murtuzayev<br />
Independent Consultant<br />
1 “A” Inshaatchilar Ave., Apt.3<br />
Baku, Azerbaijan<br />
e-mail: i_murtuzayev@hotmail.com<br />
Abstract<br />
Data from field mapping, seismology, gravimetry, and rock chemistry show the south Caspian oceanic crust to be<br />
underthrusting the continental crust <strong>of</strong> the Eurasian plate to the north and, at the same time, that <strong>of</strong> the south Caucasian<br />
plate to the southwest. Explanation is supposed to come from transtension along a 40 km-wide, ancestral lateral<br />
displacement zone whose southern master fault coincides with latitude 40° north. In the Azerbaijan mainland, the 40 th<br />
parallel shear zone embraces, from east to west, the Pliocene-Quaternary Navaghy pull-apart basin near shore; the S-<br />
shaped Sarysou Lake in the Kura River valley; a series <strong>of</strong> Jurassic calderas in the Lesser Caucasus; and the superimposed<br />
Kelbadjar caldera west <strong>of</strong> the ophiolitic belt. An <strong>of</strong>fshore seismic pr<strong>of</strong>ile across the 40 th parallel reveals a<br />
flower structure.<br />
Satellite images <strong>of</strong> the region between the Black and Caspian seas show the high heat flow-related zone <strong>of</strong> surficial<br />
evaporation striking along 40° N. The associated thermal anomaly results in high fluidity <strong>of</strong> flows being<br />
produced by mud volcanoes in the 40 th parallel shear zone. Evidence for the extensional nature <strong>of</strong> the 40 th parallel<br />
shear is provided by the 180°-reversal in the direction <strong>of</strong> tilt <strong>of</strong> mud volcano feeders and <strong>of</strong> fold vergence.<br />
The 40 th parallel shear appears to be inherited from a pre-existing Precambrian basement structural fabric. Volcanologic<br />
studies in the Lesser Caucasus have shown that the shear zone was active in the Paleozoic. Comprehensive<br />
analysis <strong>of</strong> the south Caspian basin is impossible without understanding the role <strong>of</strong> pre-existing crustal weaknesses in<br />
its evolution, architecture and petroleum system.<br />
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