Characteristics of an Upper Jurassic Carbonate Ramp in the Northern Amu-Darya Basin  

作　　者：Yongyao He Han Mu Yuanyuan Kang Yingmin Wang Bojiang Fan 

机构地区：[1]School of Petroleum Engineering and Environment Engineering, Yan’an University, Yan’an, China [2]Ocean College, Zhejiang University, Hangzhou, China

出　　处：《International Journal of Geosciences》2018年第2期148-159,共12页地球科学国际期刊（英文）

摘　　要：Overemphasizing the value of reefs in oil and gas exploration, reef-oriented geologists explain all carbonate platform deposits using the Wilson model. In their eyes, rimmed shelves are more valuable than carbonate ramps. However, organic banks are excellent reservoirs generated by carbonate ramps in the study area, as verified beyond doubt through petroleum exploration, such as this thesis, which investigates the genesis, types, and distribution of carbonate deposition in the north zone of the Amu-Darya Basin. Monoclinal palaeogeomorphology and rudists suggest shallow environments. Given that oolite shoals and rudist patch reefs were observed in the study area, the depositional system is interpreted to be a carbonate ramp. The Callovian-Oxfordian stage consists of nine lithofacies: oolitic limestone, skeletal limestone, micritic limestone, bioturbated limestone, and crystalline limestone, which are grouped into three facies associations presenting outer ramp, mid-ramp, and inner ramp facies associations. Five depositional sequences can be distinguished in the Callovian-Oxfordian stage. Each third-order depositional sequence is composed of transgressive systems tracts (TST) and highstand systems tracts (HST). The TST consists of mudstones with a higher response to natural gamma rays, whereas the HST contains various types of grainstone, with subordinate dolostone. The vertical and lateral distributions of sedimentary facies, and their interpreted depositional environments, revealed a ramp exhibiting a gradual southeast-northwestward environmental change from outer ramp, mid ramp, and inner ramp carbonate facies.Overemphasizing the value of reefs in oil and gas exploration, reef-oriented geologists explain all carbonate platform deposits using the Wilson model. In their eyes, rimmed shelves are more valuable than carbonate ramps. However, organic banks are excellent reservoirs generated by carbonate ramps in the study area, as verified beyond doubt through petroleum exploration, such as this thesis, which investigates the genesis, types, and distribution of carbonate deposition in the north zone of the Amu-Darya Basin. Monoclinal palaeogeomorphology and rudists suggest shallow environments. Given that oolite shoals and rudist patch reefs were observed in the study area, the depositional system is interpreted to be a carbonate ramp. The Callovian-Oxfordian stage consists of nine lithofacies: oolitic limestone, skeletal limestone, micritic limestone, bioturbated limestone, and crystalline limestone, which are grouped into three facies associations presenting outer ramp, mid-ramp, and inner ramp facies associations. Five depositional sequences can be distinguished in the Callovian-Oxfordian stage. Each third-order depositional sequence is composed of transgressive systems tracts (TST) and highstand systems tracts (HST). The TST consists of mudstones with a higher response to natural gamma rays, whereas the HST contains various types of grainstone, with subordinate dolostone. The vertical and lateral distributions of sedimentary facies, and their interpreted depositional environments, revealed a ramp exhibiting a gradual southeast-northwestward environmental change from outer ramp, mid ramp, and inner ramp carbonate facies.

关 键 词：CARBONATE RAMP FACIES Associations SEQUENCE Amu-Darya BASIN 

分 类 号：P61[天文地球—矿床学]