河南泌阳凹陷新生代天文地层研究

为油气成烃成藏定量研究,特别为油田剥蚀量的计算,需要建立新生代天文地层年代表。该表的数据是立足于天文学"米氏旋回假说"中地球轨道三要素的周期性和准周期性变化,求出各组(段或亚段)地质年龄。计算方法是选定泌阳凹陷11口井从大仓房组至凤凰镇组的地层分层、测井曲线数据等作频谱分析,寻找响应0.405Myr周期中的最大优势旋回和提出的三个‘基准面'的绝对年龄值。研究和计算的最后成果年龄为:1)大仓房组‘红层'顶/核三4亚段底是以邻近渤海湾盆地东营凹陷沙四下亚段‘红层'顶42.671Ma作为年龄对比和标定,向上计算出核三3亚段底为40.951Ma、核三3～1亚段顶为36.490Ma,核二段的顶为34.845Ma;2)廖庄组底/核一段之间是以邻近渤海湾盆地东营凹陷东营组底32Ma计算的数据作对比和标定,向下计算出核一段底的年龄为34.468Ma,核二段/核一段之间可能为一个大约时长为0.4Myr的小剥蚀面;向上计算廖庄组现有顶平均年龄为26.811Ma,即泌阳凹陷廖庄组全沉积的顶在中新世23.03Ma,地质构造上升和沉积回剥时间平均为3.781Myr;3)平原组底界的年龄标定为目前"国际地层表"(2004)中年龄为2.588Ma,向下计算出凤凰镇组底界平均年龄为4.155Ma。

RESEACH ON THE CENOZOIC ASTRONOMICAL STRATIGRAPHY OF THE BIYANG DEPRESSION IN HENAN PROVINCE

It is important to establish the Cenozoic astronomical stratigraphic time scale in order to better understand hydrocarbon formation,reserve estimation,and stratigraphic denudation in the Biyang Depression.The basis for astrostratigraphic age estimate for of each formation(sand or sub-layer) is the Milankovitch cycle or the quasi-periodic and periodic variation of the three elements of earth’s orbit.In order to identify the predominant cycle of 0.405 million annuals and the absolute age of three datum horizons,a spectrum analysis has been conducted on well logging data from 11 wells that penetrated strata from the Dacangfang Formation to the Fenghuangzheng Formation.The results are as follow.(1) The age of top Dacangfang red bed,also known as the bottom Eh34 formation,can be calibrated by a 42.671 Ma age from the top lower Es4 red bed in the Dongying Depression near the Bohai Bay Basin.The age of bottom Eh33 is estimated as 40.95 Ma,the age of the interval from the Eh3 to top Eh1 is 36.495 Ma,and the age of top Eh2 is 34.845 Ma.(2) The boundary between the bottom El and the top Eh1 can be calibrated by the bottom Dongying Formation’s age of 32 Ma from the Dongying Depression.The age of the bottom Eh1 is estimated as 34.468 Ma,there is a denudation plane of 0.4 million annuals between Eh2 and Eh1,and the average age of top El is 26.811 Ma.These estimated ages indicate that the back stripping time of the entire El Formation in the Biyang Depression is about 3.781 million annuals.(3) The age of the Pingyuan Formation is calibrated as 2.588 Ma according to the international stratigraphy chart,and the average age of the Fenghuangzheng Formation is 4.155 Ma.