Abstract This study demonstrates the usefulness of palynofacies as a tool for characterizing the origin, transport, and settling of particulate organic matter preserved in fluvial plain sediments and its integration with diatoms for inferring past depositional environments. Palynofacies, diatoms, and organic geochemistry (S, C/S) data from a sediment core (PR07) collected from the Jucurucu River valley in coastal southern Bahia, northeastern Brazil were used to better understand ecosystem changes that occurred in the region during the last ~7.5k years. Elemental values (S: 0.15–5.9%; C/S: 0.12–41.5) suggest marine and fluvial influences in the valley during the Holocene, and organic matter was derived from freshwater and marine phytoplankton. The presence of heterolithic deposits, brackish/marine diatoms, predominance of amorphous group, non-opaque phytoclasts, pyrite crystals, and marine microfossils suggests that a tidal flat formed during a mid-Holocene sea-level highstand. A fluvial plain developed in the last 5k years, due to marine regression and an increase in fluvial sediment supply to the region.

中文翻译：

---

巴西东北部 Jucuruçu 河流域孢粉相和硅藻的综合分析：全新世古环境变化

摘要 本研究证明了孢粉相作为表征保存在河流平原沉积物中的颗粒有机物的起源、运输和沉降的工具的有用性，以及它与硅藻的整合以推断过去的沉积环境。从巴西东北部巴伊亚州南部沿海 Jucurucu 河谷收集的沉积岩芯 (PR07) 中的孢粉相、硅藻和有机地球化学 (S, C/S) 数据用于更好地了解该地区在过去几年中发生的生态系统变化。 ~7.5k 年。元素值 (S: 0.15–5.9%; C/S: 0.12–41.5) 表明在全新世期间山谷受到海洋和河流的影响，有机物质来自淡水和海洋浮游植物。杂岩沉积物的存在，微咸/海洋硅藻，无定形基团的优势，非不透明的植物碎屑、黄铁矿晶体和海洋微化石表明潮坪是在全新世中期海平面高位形成的。由于海洋退化和该地区河流沉积物供应的增加，在过去的 5000 年中形成了河流平原。