Nd and Sm content and isotopic composition of the carbonate-free clay fraction of sediment core HU90-013-013

Sm-Nd concentrations and Nd isotopes were investigated in the fine fraction of two Labrador Sea cores to reconstruct the deep circulation patterns through changes in sedimentary supply since the last glacial stage. Three sources are involved: the North American Shield, Palaeozoic rocks from northeastern Greenland, and mid-Atlantic volcanism. The variable input of these sources provides constraints on the relative sedimentary supply, in conjunction with inception of deep currents. During the last glacial stage a persistent but sluggish current occurred inside the Labrador Basin. An increasing discharge of volcanic material driven by the North East Atlantic Deep Water is documented since 14.3 kyr, signaling the setup of a modern-like deep circulation pattern throughout the Labrador, Irminger, and Iceland basins. During the last deglacial stage the isotopic record was punctually influenced by erosion processes related mainly to ice-sheet instabilities, especially 11.4, 10.2, and 9.2 kyr ago.

本研究对两个拉布拉多海（Labrador Sea）岩芯的细粒组分开展钐-钕（Sm-Nd）浓度与钕（Nd）同位素分析，旨在通过末次冰期以来的沉积供给变化重建区域深层环流格局。本次研究涉及三种物源：北美地盾（North American Shield）、格陵兰东北部古生代岩石，以及大西洋中部火山作用。上述物源的可变输入量，结合深层流的起始演化过程，可为相对沉积供给量提供约束依据。末次冰期期间，拉布拉多海盆（Labrador Basin）内部存在一支持续但流速缓慢的深层环流。自14.3千年（kyr）以来，由东北大西洋深层水（North East Atlantic Deep Water）驱动的火山物质供给量持续增加，这一记录表明拉布拉多、伊尔明厄海盆（Irminger Basin）与冰岛海盆（Iceland Basin）已形成类似现代的深层环流格局。在末次冰消期阶段，同位素记录曾受到与冰盖不稳定性相关的侵蚀作用的阶段性影响，尤以距今11.4、10.2和9.2千年（kyr）时最为显著。