A very large Pliocene delta is present in the Kizylkum downwarp of western Turkmenistan and offshore in the southern part of the Caspian Sea to the south of the Cheleken Peninsula. There are two principal hypotheses as to the source of the oil and gas of the middle and upper Pliocene of the South Caspian oil-gas basin. One holds that the source beds are in Paleogene and Mesozoic rocks, and that thehydrocarbons migrated vertically along faults into traps in the Neogene section. The other hypothesis is that the oil has been generated in middle Pliocene sediments (Productive Unit on the west and Redbed Unit on the east) and then migrated laterally into the traps. A large sandstone complex was deposited in the Kizulkum downwarp by the Pliocene Great Amu-Dar'ya River, the channel of which is traced along an erosional cut from the Repetek-Kelif zone in eastern Turkmenistan to the Caspian Sea. This paleo-delta has an area of some 10,000 square kilometers, extending through the Kizylkum downwarp onto the Turkmen step on its southwest. Coarse-grained sandstones occur largely in the axial zone of the Kizylkum downwarp, passing on the north and south into fine-grained varieties. Sand facies are present over an area of 3,500 sq km in the lower Redbed Unit of this delta. With average thickness of 600 m, their total volume is 2,000 cu km. Sand facies of the upper Redbed Unit extend over an area of 9,500 sq km, and average thickness is 800 m. Total volume is more than 7,500 cu km. Total volume of sand facies in the delta zone of the Kizylkum downwarp is about 10,000 cu km. This delta of the Greater Amu-Dar'ya River shows up clearly on seismic profiles across the downwarp. Immediately on the east of this paleo-delta is a petroleum kitchen, which consists of Pliocene, Pontian-Miocene, and older source beds. These can have supplied petroleum directly into the deltaic sandstones. Other paths of migration are also possible, including passage to the north into the Middle Caspian province. Oil accumulation in this paleo-delta is assessed at 2.8 billion tons (20 billion barrels). The following statement appears in Oil and Gas Journal of September 29, 1997, p. 39: "Turkmenistan postulates that undiscovered reserves on its Caspian shelf at 3 billion metric tons (22 billion bbls) of oil and 4.8 trillion cu m (168 tcf) of gas. (See Babayan and Semenovich, 1966; digested in Petroleum Geology, vol. 32, no. 1, p.22-27; 2 maps and 1 seismic section; Errata: pages 25 and 26 are reversed.) Copyright 2000 James Clarke. You are encouraged to print out this News Letter and to forward it to others.