Grain-size analyses and bulk chemistry determined in surface sediment samples along the Chilean continental margin in the Southeast Pacific Ocean

Physical, chemical, and mineralogical properties of a set of surface sediment samples collected along the Chilean continental slope (21-44°S) are used to characterise present-day sedimentation patterns and sediment provenance on the Chilean margin. Despite the presence of several exceptional latitudinal gradients in relief, oceanography, tectonic evolution, volcanic activity and onshore geology, the present-day input of terrigenous sediments to the Chilean continental margin appears to be mainly controlled by precipitation gradients, and source-rock composition in the hinterland. General trends in grain size denote a southward decrease in median grain-size of the terrigenous (Corganic, CaCO3 and Opal-free) fraction, which is interpreted as a shift from aeolian to fluvial sedimentation. This interpretation is supported by previous observations of southward increasing bulk sedimentation rates. North-south trends in sediment bulk chemistry are best recognised in the iron (Fe) and titanium (Ti) vs. potassium (K) and aluminium (Al) ratios of the sediments that most likely reflect the contribution of source rocks from the Andean volcanic arc. These ratios are high in the northernmost part, abruptly decrease at 25°S, and then more or less constantly increase southwards to a maximum at ~40°S.

针对沿智利大陆坡（南纬21°至44°）采集的一组表层沉积物样品，通过分析其物理、化学与矿物学性质，可用于刻画智利陆缘的现代沉积模式及沉积物物源。尽管该区域存在地形、海洋学、构造演化、火山活动及陆上地质等多类显著的纬度梯度差异，但现今输入智利大陆边缘的陆源沉积物，其主控因素仍为降水梯度与腹地的源岩组分。沉积物粒度的总体变化趋势显示，陆源组分（去除有机碳、碳酸钙与蛋白石的部分）的中值粒径呈向南减小的规律，这被解读为沉积模式从风成向河流成因的转变。该解释得到了前人关于沉积物总沉积速率向南升高的观测结果的佐证。沉积物整体化学组成的南北向变化趋势，以铁（Fe）、钛（Ti）相对于钾（K）、铝（Al）的比值特征体现最为显著，该比值大概率反映了安第斯火山弧源岩的物质贡献。该类比值在研究区最北端处于较高水平，在南纬25°处出现陡然下降，随后大致呈持续升高趋势，直至南纬约40°处达到峰值。