Distribution of surface sediment properties along the Portuguese western margin

Organic matter contained in surface sediments from four regions on the western Portuguese shelf, which are influenced by coastal upwelling and fluvial input, was analysed with respect to elemental organic carbon (Corg) and nitrogen (Ntotal) content and isotopic carbon and nitrogen ratios (d13Corg, d15N). Corg/Ntotal weight ratios and d13Corg values are interpreted in terms of terrigenous or marine organic matter sources, supported by CaCO3 content. Organic matter in the shelf sediments is mainly of marine origin, with increasing terrigenous components only close to rivers and estuaries. In the northern shelf region the data indicates significant terrigenous supply by the Douro River. North of the Nazaré Canyon organic matter composition implies a mainly marine origin, with a higher terrestrial influence close to the canyon head. Organic matter composition in the central shelf region, which is dominated by the Tagus Estuary and the Tagus prodelta, reveals a change from a continental-type signature within the estuary to a more marine-type signature further to the west and south of the estuary mouth. In the southern region near Cape Sines the geochemical properties clearly reflect the marine origin of sedimentary organic matter. […]

本研究对葡萄牙西部大陆架上四个受沿岸上升流和河流输入影响的区域的表层沉积物中的有机物质进行了分析，考察了有机碳（Corg）和氮（Ntotal）含量，以及碳同位素和氮同位素比值（d13Corg, d15N）。通过Corg/Ntotal重量比和d13Corg值，在考虑CaCO3含量的基础上，对陆源或海洋有机物质来源进行了阐释。大陆架沉积物中的有机物质主要来源于海洋，但在河流和河口附近陆源成分逐渐增加。在北部大陆架区域，数据表明杜罗河提供了显著的陆源供应。在纳扎雷峡谷以北，有机物质组成暗示了主要来源于海洋，但在峡谷头部附近陆地影响有所增强。中央大陆架区域的有机物质组成，受塔古斯河口和塔古斯前三角洲主导，揭示了从河口内的陆相特征向河口西、南部的海洋相特征的转变。在锡内斯角附近的南部区域，沉积物有机物质的地球化学性质明确反映了其海洋起源。...