三塘湖盆地马朗凹陷卡拉岗组火山岩岩性及岩相特征研究

摘要

火山岩地层的对比和划分是研究其岩性、岩相及变化规律的前提和基础。根据测井、地震资料结合孢粉组合分析,确定三塘湖盆地马朗凹陷卡拉岗组火山岩在研究区具有北厚南薄和东厚西薄的特征。孢粉组合表现为裸子植物花粉明显优势于蕨类植物孢子,孢粉以科达粉、弗氏粉、单束细肋粉、冷杉多肋粉组合为特征,其中科达粉含量最多（25.3%～54.3%）。测井响应与其上沉积岩相比表现为＂三低两高＂的特征,即：低自然伽马、低声波时差、低补偿中子、高密度、高电阻,与哈尔加乌组相比表现为低自然伽马、中高电阻的特征。岩性以基性—中性的玄武岩、安山岩为主,其次为凝灰岩、沉凝灰岩、火山角砾岩等。马朗凹陷卡拉岗组火山岩岩相可划分为爆发相、溢流相和火山沉积相三种岩相带,火山活动以相对宁静的溢流相为主,其次为强烈的爆发相,火山沉积相仅在局部地区发育。%Comparison and classification of volcanic rocks are the premise and foundation of their lithology research,lithofacies and variation.According to log data,seismic data and pollen analysis,we found that the Kalagang volcanic rocks of Malang depression in Santanghu Basin were thick in the north and east,thin in the south and westareas.The pollen assemblage showed that Gymnosperm pollen had a clear advantage in fern spores and comprised of Genus Cordaitina（Samoilovichi） Hart,Genus Florinites Sehof,WilSonet Bentall,Genus Protohaploxypinus（Samoilovichi） Hart,Genus Striatoabieites（Sedova） Hartpollen.The content of Genus Cordaitina（Samoilovichi） Hart was up to 25.3~54.3%.Compared the log response of Kalagang volcanic rocks and Sedimentary rocks,there performed low natural gamma,low acoustic time,low compensation neutrons,high density and high resistance.The natural gamma value of Kalagang volcanic rocks was lower than Harjiawu Formation,while the resistance was higher.The lithology was mainly mafic-neutral basalt and andesite,and minor of the tuff,tuffite,volcanic breccia,and so on.Kalagang volcanic rocks of Malang depression can be divided into outbreak phase,overflow phase and volcanic sediment facies.The volcanic activity mainly occurred as a relatively quiet overflow phase,followed by strong eruption phase,and locally developed volcanic sediment facies.