Contrasting Along-Slope vs. Downslope Sedimentation Style on the High-Latitude Eastern Canadian Continental Margin During the Last 40 ka
Contrasting Along-Slope vs. Downslope Sedimentation Style on the High-Latitude Eastern Canadian Continental Margin During the Last 40 ka
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DOI：
10.3389/feart.2022.873492
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发表时间：
2022-05
期刊：
影响因子：
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通讯作者：
H. Rashid;Jianing He;R. Patro;A. Brown
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文献类型：
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作者：
H. Rashid;Jianing He;R. Patro;A. Brown
晚更新世拉布拉多海沉积系统的冰流和冰川出口的劳伦泰德冰盖（LIS）的前面开发的Huntec和3.5 kHz的地震剖面和活塞芯记录。由于LIS的有效研磨，除了与末次冰期的海因里希事件（H事件）有关的冰山外，大量的细粒沉积物和融水被输送到邻近的拉布拉多海。哈德逊海峡冰流在拉布拉多边缘的周期性扩张和收缩期间的位置允许细粒沉积物和融水直接输送到陆架下部和陆坡上部。这些排放物然后由拉布拉多海流和西边界海流向南输送。与下陆架和上陆坡相反，拉布拉多陆坡中段至下陆坡的沉积物通过西北大西洋中洋通道输送至远端。在海底或接近海底或在中层水深处的云状流层，是由融水携带过多的细粒沉积物而形成的。相比之下，非歧视性的冰漂流过程提供了各种尺寸的碎屑，但其对沉积柱的总贡献仅很小，尽管其在H事件期间具有古气候意义。海因里希H1、H2和H4层由其特征性的云状流层沉积物确定，即，交替的粗粉砂和粘土大小的纹层与散布着粗到细颗粒坠石的薄冰筏碎片。此外，细纹层的逐渐变薄和最终消失（即，H层中的粗、细粉砂/粘土）表明，由于长距离运输，细粉已耗尽并被雨水淋出。然而，H3层是由近端的云状流层沉积物（上斜坡）和精细层状泥浊积岩（下斜坡和深盆地）的组合确定的。在拉布拉多斜坡和盆地下部，H3地层等效层由极厚的精细层状富碳酸盐泥浊积岩确定。发散沉积样式（即，沉积相反映）和H3层厚度与其他H事件的比较表明，哈德逊海峡冰流位置与其他H事件不同。因此，我们的数据暗示，在H3层之间的东，西北大西洋的分歧可能在于哈德逊海峡冰流的拉布拉多大陆边缘的位置。
Late Pleistocene Labrador Sea depositional systems developed in front of ice streams and glacier outlets from the Laurentide Ice Sheet (LIS) are documented by Huntec and 3.5 kHz seismic profiles and piston cores. Due to efficient grinding by the LIS, massive amounts of fine-grained sediments and meltwater in addition to the icebergs linked to the Heinrich events (H events) of the last glaciation were delivered to the neighboring Labrador Sea. The position of the Hudson Strait ice stream during the periodic expansion and contraction on the Labrador margin allowed fine-grained sediments and meltwater direct delivery on the lower shelf and upper slope. These discharges were then transported southward by the Labrador Current and western boundary current. In contrast to the lower shelf and upper slope, sediments delivered on the mid to the lower Labrador Slope were transported by the Northwest Atlantic Mid-Ocean Channel to distal sites. The nepheloid flow layer at or near the sea bottom or at mid-water depths developed from meltwater loaded with an excessive charge of fine-grained sediments. Contrastingly, the non-discriminatory ice rafting process delivered detritus of all sizes, but its total contribution to the sediment column was only minor, notwithstanding its paleoclimatic significance during H events. Heinrich H1, H2, and H4 layers were identified by their characteristic nepheloid flow layer deposits, that is, alternating coarse silt and clay-sized laminae with thin ice-rafted debris interspersed by coarse- to fine-grained dropstone. Furthermore, the progressive thinning and eventual disappearance of the fine-laminae (i.e., coarse and fine silt/clay) in H layers at the distal sites suggest the exhaustion and raining out of fines due to long-distance transport. However, the H3 layer was identified by a combination of nepheloid flow layer deposits (upper slope) and finely laminated mud turbidites (lower slope and deep basin) at proximal sites. In the lower Labrador Slope and Basin, the H3 stratigraphic equivalent layer was identified by exorbitantly thick finely laminated carbonate-rich mud turbidites. The divergent sedimentation style (i.e., reflected by the sediment facies) and the thickness of the H3 layer compared to other H events suggest that the Hudson Strait ice stream position was different from other H events. Therefore, our data imply that the divergence in the H3 layer between the eastern and western North Atlantic might lie with the position of the Hudson Strait ice stream on the Labrador continental margin.