江汉盆地当阳向斜区主要不整合面剥蚀厚度的中低温热年代学约束  

Erosion Thickness of the Main Unconformities of Dangyang Subbasin,Jianghan Basin:Constrained by the Middle-Low Thermochronology

作　　者：施小斌[1] 石红才[1,2] 杨小秋[1] 蒋海燕[1,2] 龙幼康[3] 吴保珍[1,2] 

机构地区：[1]中国科学院边缘海地质重点实验室,南海海洋研究所,广州510301 [2]中国科学院研究生院,北京100049 [3]江汉油田勘探开发研究院,武汉430223

出　　处：《地质学报》2013年第8期1076-1088,共13页Acta Geologica Sinica

基　　金：中石化海相前瞻性课题(YPH08057)资助的成果

摘　　要：本文利用磷灰石裂变径迹、(U-Th-Sm)/He及镜质体反射率Ro%等古温标方法综合分析了江汉盆地当阳向斜区主要不整合面剥蚀厚度。结果表明:发育于古近纪末期不整合面T1界面累积剥蚀厚度超过1000m,且局部正反转区域如谢家湾断褶带等则遭受更大规模的剥蚀,剥蚀厚度可能超过2000m,而发育于晚侏罗世—早白垩世的不整合面T11界面累积剥蚀厚度超过4000m,且主要是晚侏罗世—早白垩世构造事件的结果,表明该期剥蚀量明显大于古近纪末T1界面剥蚀量;晚三叠世—侏罗纪期间,当阳地区发育前陆坳陷带,侏罗纪堆积体具有明显东厚西薄的楔形体特征,位于盆地东部的前渊区沉积厚度可超过5000m;包括现今三叠系和侏罗系出露区以及江陵凹陷局部断隆区在内的前白垩系在侏罗纪前陆坳陷带发育时期达到最大埋深和最高古温度,其Ro%主要是该期获得的;晚白垩世—古近纪发育的断陷盆地范围可能远比现今残留盆地分布广,江陵凹陷上白垩统—古近系厚度超过9000m,其中古近系可能超过7000m,而在河溶凹陷谢家湾断褶带古近系厚度可超过3300m。Middle-Low thermochronological data, including apatite fission track, （U-Th-Sm）/He and vitrinite reflectance, were used to analyze the erosion thickness occurring at the two main unconformities. Results shows that the accumulated erosion thickness at the unconformity T1 during late Paleogene is more thanl000m, and in some tectonic inverse area such as Xiejiawan fault-fold belt, erosion thickness might be larger than 2000 m. While the accumulated erosion thickness at the other main unconformity Tll, which developed during Late Jurassic through Early Cretaceous, is larger than 4000 m, most of which was eroded during the Late Jurassic through Early Cretaceous tectonic event, indicating that the eroded thickness during this period is much larger than that of the unconformity T1 happened at the end of Paleogene. During Late Triassic through Jurassic, the studied area developed foreland basin with a wedge Jurassic strata obviously thicker in the eastern region. The Jurassic sediment thickness in the eastern foredeep was larger than 5000 m. The pre-Cretaceous formation in the Triassic and Jurassic outcrop area and some local fault-fold belts in Jiangling sag obtained its deepest depth and highest temperature, thus its Ro~//0 during the Jurassic foreland basin, was buried; The original rifted basin developed during Late Cretaceous through Paleogene was much larger than nowadays residual basin, the thickness of the upper Cretaceous- Paleogene was larger than 9000m, where the Paleogene might be thicker than 7000 m, and the Paleogene in Xiejiawan fault-fold belt of Herong sag might be larger than 3300 m.

关 键 词：中扬子地块 剥蚀厚度 磷灰石裂变径迹 (U-Th-Sm) He 镜质体反射率 

分 类 号：P618.13[天文地球—矿床学]