Abstract Primary paleoproductivity provides basic organic matter for the formation of high-quality hydrocarbon source rock. A progressive method to quantitatively calculate paleoproductivity on the basis of total organic carbon (TOC) has been proposed to evaluate the contribution of primary paleoproductivity to a hydrocarbon source rock with high organic matter abundance. In this study, pyrite contents, organic maceral compositions and high-resolution sedimentation rates (SRs) were used to recover the amount of organic matter oxidation and to exclude the effect of terrestrial clastic input during the deposition of the Chang 7 sediment. Multiple calculation methods were used to quantitatively reconstruct paleoproductivity, and the results suggest that the Ordos Basin was a eutrophic lacustrine basin (approximately 2 × 104 mg C cm−2 kyr−1 to 10 × 104 mg C cm−2 kyr−1) during the Chang 7 stage compared with modern lake productivity. The paleoclimatic analysis indicates that a warm humid paleoclimate was beneficial for increasing the weathering intensity, which could have provided more nutrient inputs to the depositional environment with incoming terrestrial debris. In addition, the plate collision between the North China Block and Yangtze Block generated moderate volcanic ash that spread to the study area and provided large amounts of essential nutrients for algae blooms. Moreover, a brackish water condition promoted upward mixing of deep water, which inhibited water mass stratification and then facilitated primary paleoproductivity. In general, the Chang 7 high-quality hydrocarbon source rock is a result of increased paleoproductivity resulting from suitable paleoclimate conditions, brackish water masses and abundant essential nutrient inputs.

中文翻译：

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鄂尔多斯盆地（华北）长7单元古生产力及其控制因素

摘要 原始古生产力为优质烃源岩的形成提供了基础有机质。已经提出了一种基于总有机碳 (TOC) 定量计算古生产力的渐进方法，以评估原始古生产力对具有高有机质丰度的烃源岩的贡献。在这项研究中，黄铁矿含量、有机微晶成分和高分辨率沉积速率 (SRs) 被用于恢复有机质氧化的量，并排除长 7 沉积物沉积过程中陆地碎屑输入的影响。采用多种计算方法定量重建古生产力，结果表明，与现代湖泊生产力相比，长7期鄂尔多斯盆地为富营养化湖盆（约2×104 mg C cm-2 kyr-1至10×104 mg C cm-2 kyr-1）。古气候分析表明，温暖潮湿的古气候有利于增加风化强度，这可能为进入陆地碎片的沉积环境提供更多的养分输入。此外，华北地块与扬子地块的板块碰撞产生中度火山灰，扩散到研究区，为藻华提供了大量必需的养分。此外，微咸水条件促进了深水向上混合，抑制了水团分层，进而促进了原始古生产力。一般来说，