GAS VENTING AND LATE QUATERNARY SEDIMENTATION IN THE PERSIAN (ARABIAN) GULF

High resolution 3.5 kHz echo sounding profiles and piston cores were u sed to reconstruct the microtopography and late Quaternary depositiona l history of the Persian Gulf. Perversive throughout the seafloor of t he Gulf is an extensive network of pockmarks formed by seepages of the rmogenic gas. These gas seeps and bottom water exiting the Gulf via th e Strait of Hormuz are the most significant processes controlling pres ent-day sedimentation in the region. Erosion by these seeps has been s o intense in the Baiban Shelf in the Strait of Hormuz as to create a ' 'hoodoo'' like terrain on the outer shelf. The surfical geology of the Gulf documents a short lived transgression 29,400 to 22,800 years ago during the Wisconsin regression which began 125,000 years ago, the Wi sconsin regressive maxima when sea level dropped to -120/-130 m about 21,000/20,000 years ago and the climate was dry and eolian and paralic sedimentation characterized the Gulf, the Holocene transgression 18,0 00 to 12,000 years ago when the climate was more humid than during the climax of the Wisconsin regression, a dry phase 12,000 to 9000 years ago when the Persian Gulf was a site of eolian and carbonate depositio n, and the present sediment cycle during the last 9000 years under a m ore humid regime. It was during the present cycle that southeast trend ing marl lobes were deposited off Iran, Arabia acquired its hyper-arid climate about 3000 years ago and the Gulf attained its present config uration about 1000 years ago as a result of the construction of the Ti gris Euphrates Delta at its head and tectonism and aggradation along i ts Arabian and Iranian flanks.