Paleo-oceanographic follow-up of a Younger Dryas contourite in the North and South of the Gulf of Cadiz

Abstract: How much paleoceanographic information can a single contourite unit comprise is a matter for debate. Focusing on two contourite units sitting in the North and South of the Gulf of Cadiz, on the Iberian (GC-01A) and the Moroccan (TG-2) margins, we examine their synchronous sedimentological evolution during the Younger Dryas (YD). We apply a detailed multi-proxy analysis, which includes physical properties, sediment composition, O and C stable isotopes in foraminifera, and both planktonic and benthic foraminifera species and ecological assemblages. We seek to bound the ecological and environmental conditions playing during the YD´ formation of these specific contouritic sediments by relating geochemistry, biology and water dynamics in order to define a pattern of deposition. In the end, we trace in common water masses involved in the formation of the YD contourites in either sides of the Gulf of Cadiz. While the northern branch of the Mediterranean Outflow Water (MOW) is widely assumed to be responsible for the thick contourite depositional systems found along the Iberian margin, the currents originating the contouritic drifts found in the Moroccan margin are less established. A conceptual model of the detailed characterization of a single contourite is proposed here, contributing to interpret contourite depositional systems.摘要：单个等深岩单元（contourite unit）所能承载的古海洋学信息多寡，仍是一个有待商榷的学术议题。本研究以加的斯湾北部与南部的两处等深岩单元为研究对象，二者分别坐落于伊比利亚大陆边缘（GC-01A站位）与摩洛哥大陆边缘（TG-2站位），旨在探讨其在新仙女木事件（Younger Dryas, YD）期间的同步沉积学演化过程。研究采用精细化多指标分析手段，涵盖沉积物物理性质、组分组成、有孔虫（foraminifera）的氧、碳稳定同位素分析，以及浮游有孔虫与底栖有孔虫的物种组成及生态组合特征。本研究通过关联地球化学、生物学与水动力过程，旨在限定该批等深岩沉积物在新仙女木事件沉积期的生态与环境背景，以明确其沉积模式。最终，本研究追溯了加的斯湾两侧形成新仙女木期等深岩的共同水团来源。学界普遍认为，伊比利亚沿岸发育的厚层等深岩沉积体系，主要受地中海流出水（Mediterranean Outflow Water, MOW）北支控制，但摩洛哥沿岸等深岩丘形成的动力机制尚未明确。本研究提出了一套单一等深岩精细化表征的概念模型，可为等深岩沉积体系的解译研究提供参考。