The magnetic signature of rapidly deposited detrital layers from the Deep Labrador Sea: Relationship to North Atlantic Heinrich layers
The magnetic signature of rapidly deposited detrital layers from the Deep Labrador Sea: Relationship to North Atlantic Heinrich layers
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DOI：
10.1029/96pa00583
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发表时间：
1996-06
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影响因子：
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通讯作者：
J. Stoner;J. Channell;C. Hillaire‐Marcel
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文献类型：
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作者：
J. Stoner;J. Channell;C. Hillaire‐Marcel
拉布拉多深海活塞岩心（P-094）的岩石磁性参数对识别快速沉积的碎屑层是有用的，其中一些碎屑层与北大西洋Heinrich层相关。磁性和岩性的变化区分了末次冰期快速沉积的两类碎屑层：（1）七个碎屑碳酸盐（DC）层具有高碳酸盐含量，平均磁铁矿粒径约为背景沉积物的4倍;（2）6个低碎屑碳酸盐（LDC）层的磁性与DC层非常相似，但碳酸盐含量较低（类似于背景沉积物）。与DC和LDC层相关的磁铁矿分选良好，层内和层间相对均匀。冰筏碎屑（IRD），由大于125微米的颗粒尺寸部分的增加的百分比和高磁化率识别，与大多数DC和LDC层相关，但不是主要的碎屑成分。DC和LDC层与分选良好的磁铁矿的粒度增加，但不与粗粒含量的对应关系，排除了冰筏作为主要的沉积机制。DC和LDC层可能是由附近西北大西洋中洋海峡（NAMOC）浊流活动产生的悬浮沉积物沉积而成。这一解释得到了格陵兰海隆一个地点的活塞岩心（P-013）的支持，该地点大部分但不完全在NAMOC的影响范围之外。DC层与IRD的关联和DC层与北大西洋Heinrich层的明显年龄相关性表明，在P-094和相关的北大西洋Heinrich层中产生IRD的冰进展也引发了NAMOC的浊流。几个DC和LDC层，但是，不相关的承认海因里希层，但似乎是同时代的高频IRD丰富的层在北大西洋最近发现的。
Rock magnetic parameters from deep Labrador Sea piston core (P-094) are useful for recognizing rapidly deposited detrital layers, some of which correlate with North Atlantic Heinrich layers. Variations in magnetic properties and lithology distinguish two classes of rapidly deposited detrital layers during the last ice age: (1) seven detrital carbonate (DC) layers have high carbonate content and mean magnetite grain diameters about 4 times greater than the background sediments; (2) six low detrital carbonate (LDC) layers have very similar magnetic properties to DC layers but low carbonate content (similar to the background sediments). The magnetite associated with DC and LDC layers is well sorted and relatively uniform within and between layers. Ice-rafted detritus (IRD), recognized by increased percentage of the > 125 micron grain-size fraction and by high magnetic susceptibility, is associated with most DC and LDC layers but is not the dominant detrital constituent. The correspondence of DC and LDC layers with increased grain size of well-sorted magnetite, but not with coarse fraction content, precludes ice rafting as the primary depositional mechanism. DC and LDC layers may have been deposited from suspended sediment derived from turbidite activity in the nearby Northwest Atlantic Mid-Ocean Channel (NAMOC). This interpretation is supported by a piston core (P-013) from a Greenland Rise site largely, but not completely, outside the influence of the NAMOC. The association of DC layers with IRD and the apparent age correlation of DC layers to North Atlantic Heinrich layers suggest that the ice advances which produced the IRD in P-094 and in correlative North Atlantic Heinrich layers also triggered turbiditic flows down the NAMOC. Several DC and LDC layers, however, do not correlate with recognized Heinrich layers but appear to be coeval with recently discovered high-frequency IRD-rich layers in the North Atlantic.