抚顺盆地始新世古湖泊演化

Paleolake Evolution of Eocene in Fushun Basin

通过野外实测剖面及室内测试分析等方法,对始新世断陷盆地抚顺盆地的古湖泊开展研究,其主要目的是揭示始新世—渐新世全球变冷气候在大陆的响应。野外岩性、相标志及岩石薄片分析表明,抚顺盆地始新统沉积相演化规律主要表现从湖沼亚相—浅湖亚相—半深湖亚相—深湖亚相—半深湖亚相—浅湖亚相,水体深度变化总体表现为由浅—深—浅的过程。借助B、Mn、Ti、Co、Cr、Ni、V等微量元素含量以及Sr/Ba、V/(V+Ni)、Ni/Co、ωFe2 O3/ωFeO等元素和氧化物比值分析,得出抚顺盆地从始新世早期到晚期气候发生了明显的变化,始新世早期主要为湿润的成煤气候,始新世中期的计军屯组则显示了半湿润气候,到了始新世的中晚期则出现了干燥的气候条件,形成了半咸水—咸水的一套泥灰岩与泥页岩互层的干旱气候演化。总体有从始新世向渐新世,气候由湿润向干燥变化的规律。

In order to interpret continental responses to globally climatic cooling in the Eocene-Oligocene,we have studied the paleolake features of Fushun Basin,an Eocene fault-depression basin in NE China,through measuring actual strata profiles in the fields and indoor sample testing.The analysis of rock facies,facies indicators and rock thinsections suggests the evolution history of sedimentary facies in Eocene,Fushun Basin.Sedimentary subfacies vary as： lake and marshland-shallow lacustrine-half deep lacustrine-deep lacustrine-half deep lacustrine-shallow lacustrine,with the water depth varying as： shallow-deep-shallow.On the basis of contents of trace elements（B,Mn,Ti,Co,Cr,Ni,V）,element contents ratios（Sr/Ba,V/（V ＋ Ni）,Ni/ Co,ωFe2O3 /ωFeO） and ratios of oxides,we point out that there was an abrupt climatic change from early Eocene to late Eocene in Fushun Basin.In the early Eocene,climate was moisture and good for coral forming.While,in the middle-late Eocene,climate changed into drier and made contribution into the interbedding between marlite forming in saline and half-saline water and clay shale.In general,our study shows that the climate changed from moisture to dry in Eocene-Oligocene.