依兰盆地始新统达连河组油页岩成因新认识

综合利用野外露头、岩石矿物组合、有机岩石学、元素地球化学等资料,研究了依兰盆地达连河组含煤-油页岩段与油页岩段油页岩成因。含煤-油页岩段油页岩有机质类型主要为II1型,油页岩段油页岩有机质类型主要为II1-II2型,且都表现为弱氧化-还原特征,但是两者却具有不同的成因。含煤-油页岩段油页岩形成于湖泊-沼泽沉积体系,油页岩形成于湖泛作用基准面上升时期,直接发育在原来沼泽发育的位置,由于该时期水动力很弱,无法带入新的氧气,又有大量的生物生长并且不断原地死亡堆积,形成了有机质很丰富的油页岩。油页岩段油页岩形成于半深湖-深湖体系,该体系中频繁重力流作用的出现,把陆源碎屑带入深湖、半深湖中的时候,也把氧气带入到湖底,不利于有机质的保存,导致该油页岩段的有机质呈混合型以及弱氧化-还原特征。

New Research on Oil Shale Origin of Eocene Dalianhe Formation in Yilan Basin

Utilizing comprehensive ways of field outcrops,mineral assemblages,organic petrology and element geochemistry analysis,we study the oil shale features and origins of coal-oil shale bearing and oil shale bearing sections in Dalianhe Formation,Yilan basin.Organic matter type of oil shale organisms in coal-oil shale bearing sections is II1 and II1-II2 in oil shale bearing sections.Oil shale not only in coal-oil shale bearing sections,but also in oil shale bearing sections,are all characterized by weak oxidized-reduced,and with different origins.Oil shale of coal-oil shale bearing sections was generated in lacustrine-swamp systems and was located on the former swamps when the base level was rising.Because the hydrodynamic was relatively weak and oxygen can hardly be renewed,large quantities of plants and animals died and be well buried forming into organism-rich oil shale.Oil shale of oil shale bearing sections was generated in deep and semi deep lacustrine systems,in which the gravity flows took place very often.Gravity flows can not only bring terrigenous clastics,but also induce oxygen into the deep and semi deep lacustrine systems.In this environment,organism was poorly preserved.As a result,the organisms in oil shale bearing sections are characterized by mixed ones(II1-II2) and weak oxidized-reduced.