Relationship Between Bore-Hole Closure and Crystal Fabrics in Antarctic Ice Core from Cape Folger

• Published in: Journal of Glaciology
• Main Authors: Thwaites, Richard J., Wilson, Christopher J. L., McCray, Anthony P.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1984
• Subjects: Antarc*; Antarctic; ice core; Ice Sheet; Journal of Glaciology
• Online Access: http://dx.doi.org/10.1017/s0022143000005906; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000005906

Abstract Two holes were drilled to depths greater than 300m in the Antarctic ice sheet, near Cape Folger on the Law Dome. The holes underwent considerable closure below 250m with localized strain-rates as high as 1 to 1.5×10 −6 s −1 . The closure observed in holes was non-uniform and occurred in zones 0.5 to 3 m wide. These Zones parallel the flow plane in the ice mass and are associated with a distinct domainal structure. High-closure zones are characterized by interlocking and irregular-shaped ice grains with many sub-horizontal c -axes and only occasional c -axis clusters at a high angle to the flow plane. Low-closure zones contain tabular grains with the long dimension parallel to the flow plane, abundant deformation features and a predominance of c -axes oriented at a high angle to the flow plane. The relationship between closure rate and c -axis fabric is attributed to marked plastic flow by intracrystalline slip on the basal plane to produce higher closure in areas where there is a greater variation in c -axis orientation. This deformation is attributable to overburden pressure and hence is related to depth, and is independent of shear within the main body of the ice mass.