Estimating the sliding velocity of a Pleistocene ice sheet from plowing structures in the geologic record
Estimating the sliding velocity of a Pleistocene ice sheet from plowing structures in the geologic record
复制标题
根据地质记录中的犁耕结构估算更新世冰盖的滑动速度
DOI：
--
复制
发表时间：
2004
期刊：
影响因子：
--
通讯作者：
T. Hooyer
中科院分区：
文献类型：
--
作者：
N. Iverson;T. Hooyer
[1]当冰盖滑过沉积床时，部分嵌入冰川底部的碎屑会犁过沉积床表面。这些碎屑的大小分布，如果可以从地质记录中的结构中得到表征，就可以用来估计过去冰盖的滑动速度。结合冰川滑动理论和岩土工程的静力锥入度理论，可以根据碎屑的尺寸参数、冰的流动性参数以及冰和碎屑的热力学性质来计算滑动速度。如果测量河床的摩擦特性，还可以计算冰川作用期间河床上的有效正应力和河床剪切强度。我们用这种方法来估计滑动速度的伊利诺伊州冰盖，离开犁结构在附近的皮奥里亚，伊利诺伊州的水泥冰水。正常和基底温带冰的流动性参数分别得出140-168 m yr−1和60-72 m yr−1的滑动速度。如果溶质阻碍了冰通过碎屑的再结晶，或者如果载满碎屑的冰和碎屑之间的摩擦阻碍了滑动，那么这些都是高估的。从床粉土的室内试验中确定的预固结应力同意使用碎屑尺寸参数计算的有效正应力。床层的高剪切强度（>145 kPa）和保留在其中的主要结构表明，由于床层的普遍剪切而引起的额外运动是不可能的。这种方法在其他地方的应用将提供基本的速度数据，否则无法用于测试和调整冰盖模型。
[1] As an ice sheet slides over its sediment bed, some clasts partly embedded in the glacier sole plow through the bed surface. The size distribution of such clasts, if it can be characterized from structures in the geologic record, can be used to estimate the sliding velocity of a past ice sheet. By combining a theory of glacier sliding with a geotechnical theory of cone penetration, sliding velocity can be calculated in terms of clast-size parameters, a fluidity parameter for ice, and the thermodynamic properties of ice and clasts. If frictional properties of the bed are measured, the effective normal stress on the bed and bed shear strength during glaciation can also be calculated. We used this approach to estimate the sliding velocity of an Illinoian ice sheet that left plowing structures in cemented outwash near Peoria, Illinois. Fluidity parameters for normal and basal temperate ice yielded sliding velocities of 140–168 m yr−1 and 60–72 m yr−1, respectively. These are overestimates if solutes impeded regelation of ice past clasts or if friction between debris-laden ice and clasts retarded slip. Preconsolidation stresses determined in laboratory tests on silt from the bed agree with effective normal stresses calculated using clast-size parameters. The high shear strength of the bed (>145 kPa) and primary structures preserved within it indicate that additional movement due to pervasive shear of the bed was unlikely. Application of this method elsewhere would provide basal velocity data that are otherwise unavailable for testing and tuning of ice sheet models.