Mechanism of organic matter enrichment from Wufeng-1st member in Longmaxi Formation shale in Zigong and Luzhou areas of the Southern Sichuan Basin
To explore the enrichment of organic matter in the Ordovician Wufeng-Silurian 1st member of the Longmaxi Forma-tion in the Zigong and Luzhou areas of the Southern Sichuan Basin,we analyzed total organic carbon(TOC)content,mineral composition,and major and trace elements to investigate the sedimentary environment.The results indicate that the Wufeng-1st member of the Longmaxi Formation was deposited in a suboxic-anoxic environment in both areas.In the Zigong area,the Wufeng-1st member represents a restricted environment,with an average product of Co and Mn mass fraction w(Co)×w(Mn)value of 1.13,while the Luzhou area experienced upwelling activity,with an average w(Co)×w(Mn)value of 0.38.The values of Baxs content and the Ba-Al mass ratio suggest moderate paleoproductivity in the Zigong area and high pa-leoproductivity in the Luzhou area.In the Zigong area,the influence of an underwater low uplift reduced the sedimentary rate(SR),leading to a model of moderate productivity,reducing conditions and low SR for organic matter enrichment.In con-trast,in the Luzhou area,upwelling brought nutrients,supporting the accumulation of organic-rich shale deposite a relatively high SR,suggesting a model of high productivity,reducing conditions,and high SR.
Sichuan BasinZigong and Luzhou areaWufeng-1st member in Longmaxi Formationredox conditionpalaeo-productivityorganic matter enrichment
万方数据
维普
