Platform in the north. Numerous oil and gas fields have been discovered in this region in addition to Karachaganak, such as Astrakhan, Tengiz and Zhanazhol Fields. The field consists of a heterogeneous carbonate massif with strata from three geologic periods and numerous stages of deposition during these periods. The following have been identified: Permian: Kungurian, Artinskian, Sakmarian, Asselian Carboniferous: Serpukhovian, Visean, Tournaisian Devonian: Famennian The depositional setting of the field is also varied. On the basis of core sample analysis and seismic studies the following depositional settings have been identified: limestone, talus, normal marine, shallow marine, inner reef lagoon, reef core, relatively deep water, slope, and anhydrite. The variation of deposition is due to the long period over which the Karachaganak structure was formed. From the Late Devonian to the middle Carboniferous the field was an atoll, over which in the Early Permian a system of reefs were built. At its greatest the reservoir is 1.5 km thick. This type of reservoir structure has been seen in analogous fields including Kenkiyak, Zhanazhol, Tengiz, and possibly Astrakhan fields. A west-east cross section through Karachaganak resembles the twin humps of a camel, indicating two separate reef highs. Likewise, the large variation of deposition has led to four different types of carbonate cores in the structure: biothermal, biomorphic detrital, organo-clastic, and biochemogenic. Of these biomorphic detrital are the most common followed by biothermal rock types. However, estimates of their volumes range from 30-90% for the former and 10-60% for the latter. Oil and gas migration As with other reservoirs in the North Caspian (Pricaspian) Basin, it is thought that the Karachaganak reservoir was filled over multiple stages, the first of which began during late Paleozoic time with the formation of oil pools. As the basin began to subside, gas was generated and migrated to the traps. The gassiness of the reservoirs is determined by their location in the basin. Northern reservoirs tend to be wet; the southwest part of the basin is more gas prone than are the east and southeast. Berezovka controversy Since 2002, residents from the village located closest to the Karachaganak Field have been campaigning for relocation and compensation. The villagers, led by the local organization Zhasil Dala (Green Steppe), maintain that they are suffering a host of illnesses and environmental degradation due to exposure to toxic emissions from the Karachaganak Field, situated five kilometers away. Independent Bucket Brigade air