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首页> 外文期刊>Marine Geology >Continental slope sedimentation adjacent to an ice margin. III. The upper Labrador Slope
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Continental slope sedimentation adjacent to an ice margin. III. The upper Labrador Slope

机译：靠近冰​​缘的大陆坡沉积。三，拉布拉多上坡

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The upper LabradorSlope is the key area forsediment transfer from the mortheastern margin of the PleistoceneLaurentide ice sheets (LIS) to the deep basin. It is subdivided fromnorth to south into 8 sectors based on relief differences and echo-character on 750 line-km of continuous sleeve-gun and 3.5kHzseismic profiles. High- to moderate-relief sectors 2 and 4 and, inpart, 6 and 8 are seismically transparent and well stratified withcontinuous individual high-amplitudereflections and deeppenetration; low-relief sectors 1, 3, 5 and 7 show strong bottomreflections and, with the exception of sector 1, low seismicpenetration, poor stratification, and low-amplitude, if any,subbottom reflections. The lateral distribution of these alternatinghigh- to moderate- and low-relief sectors reflects fundamentaldifferences in the sediment transfer mechanisms through outletsfrom the LIS onto the slope. Low-relief slope sectors representdebrite and turbidite slopes and are located in front of ice-outletson the slope and adjacent regions to the north. They originate frommass wasting on the upper slope of glacial detritus with asignificant coarse component originally delivered as englacial orsubglacial material and deposited in (end-) moraines or as bedloadby subglacial or supraglacial rivers. High- to moderate-reliefsectors originate from fall-out of suspended sediment from turbidsurface-plumes (TSP) and preferentially occur off the southernhalf of outlets and south of major outlets, as exemplified by sector2 south of the Hudson Strait outlet. This asymmetry is caused bythe south-flowing Labrador Current, which entrains the buoyantlyrising turbid meltwater-plumes at the glacier front. The presenthigh-relief topography, which shows a dendritic pattern of upslopecanyon branching, is the result of retrograde, headward canyonerosion by mass-wasting processes of an originally much smoothermud-blanket surface. The sediment is remobilized by slumping andentrained in debris flows and turbidity currents. The occurrence ofTSP deposits on the high- to moderate-relief upper-slope sectorsrequires a summer sea surface not frozen over during major partsof the Pleistocene, including glacial maxima. TPS deposition onthe upper slope, ice-rafting, and a plethora of ice-margindepositional phenomena, many of which give rise to mass-wastingand mass-flow phenomena, are the main features that make high-latitude continental slopes adjacent to continental ice- sheetsdifferent form their lower-latitude counterparts.
机译：LabradorSlope上部是沉积物从更新世洛朗德冰盖（LIS）的近岸边缘转移到深海盆地的关键区域。根据起伏差异和回波特征，在连续线长炮和3.5kHz地震剖面上750线公里，将其从北向南细分为8个扇区。高至中度浮雕的第2和第4扇区，以及第6和第8扇区在地震上是透明的，并且分层良好，并具有连续的个别高振幅反射和深层穿透作用。低浮雕扇区1、3、5和7表现出强烈的底部反射，并且，除了扇区1之外，地震渗透率低，分层差，并且低振幅（如果有的话）是底部反射。这些高，中，低浮雕交替部分的横向分布反映了通过LIS出口到斜坡上的输沙机理的根本差异。低起伏的坡度扇区代表碎屑岩和浊积岩坡度，位于该斜坡和北部的邻近区域的出冰口前方。它们起源于冰川碎屑上坡的大量浪费，其上有大量的粗糙成分，最初以冰川或冰下物质的形式输送，并沉积在（末端）冰rain中，或以冰川作用或冰川下河的河床沉积。高到中度浮雕区是由于混浊表面羽流（TSP）造成的悬浮沉积物沉降而形成的，并且优先出现在网点的南半部和主要网点的南部，例如哈德逊海峡网点以南的扇区2。这种不对称性是由向南流动的拉布拉多洋流引起的，拉布拉多洋流夹带了冰川前部浮起的浑浊的融化水-羽流。当前的高浮雕地形显示了上坡峡谷分支的树突状图案，是由于原本更加光滑的泥毯状表面的大量消退而逆行，向前峡谷侵蚀的结果。沉积物通过塌落而被清除，并夹带在泥石流和浊流中。在高至中浮起的上斜坡扇形区出现TSP沉积物需要在更新世的主要部分（包括冰川最大值）不冻结的夏季海面。 TPS在上斜坡的沉积，浮冰以及过多的冰质沉积现象，其中许多会导致质量浪费和质量流现象，这是使邻近大陆冰原的高纬度大陆斜坡与众不同的主要特征形成他们的低纬度对应物

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