Cenozoic Diapiric Traps in Eastern China: ABSTRACT

Abstract

Genetically, there are 2 types of Cenozoic diapiric traps in the oil fields in eastern China. One type is produced by cold diapirism owing to the rise of evaporites and soft mudstone. This type can be divided into 3 patterns. The first pattern is the faulted ridge with 1,000 m (3,300 ft) closure and flanks dipping up to 30°. A complex graben system is developed on the top. The amplitude of the core of the anticline is about 3,000 m (9,800 ft). The Xiangzheng structure in the Shengli oil field and the Wang-cung structure in the Qian-jiang depression are examples. The second pattern is the gentle anticline or dome with 50-300 m (160-985 ft) closure and 3°-10° dip on the flanks. The incompetent strata beneath it are about 1,000 m (3,300 ft) thick. The Tuocun -Shengli structure in the Shengli oil field is an example. The third pattern is a nose-like structure with less than 50 m (160 ft) closure. This pattern is usually located near the zero edge of incompetent strata. The Serniusi structure in the Dagang oil field is an example. Another type of Cenozoic diapiric trap results from hot diapirism associated with the intrusion of gabbro or diabase. Such traps are typically small, round domes. The dip of the flanking strata generally increases with depth as the diapir is approached. A graben system is developed on top of the diapir. The distribution of these traps is related usually to regional fault zones and coincides with the distribution of the magmatism. The Matouzung structure in the Jinhu depression is one of the examples. End_of_Article - Last_Page 520------------