We investigated the microstructures of five ice core samples from the Styx Glacier, northern Victoria Land, Antarctica. Evidence of dynamic recrystallization was found in all samples: those at 50 m mainly by polygonization, and those at 170 m, largely by grain boundary migration. Crystallographic preferred orientations of all analyzed samples (view from the surface) typically showed a single cluster of c-axes normal to the surface. A girdle intersecting the single cluster occurs at 140–170 m with a tight cluster of a-axes normal to the girdle. We interpret the change of crystallographic preferred orientations (CPOs) at <140 m as relating to a combination of vertical compression, and shear on a horizontal plane, and the girdle CPOs at depths >140 m, as the result of horizontal extension. Based on the data obtained from the ground penetrating radar, the underlying bedrock topography of a nunatak could have generated the extensional stress regime in the study area. The results imply changeable stress regimes that may occur during burial as a result of external kinematic controls, such as an appearance of a small peak in the bedrock.

中文翻译：

---

南极维多利亚州北部维多利亚州斯蒂克斯冰川的天然冰的微观结构和织物转变

我们调查了南极维多利亚州北部维多利亚州斯蒂克斯冰川的五个冰芯样品的微观结构。在所有样品中都发现了动态再结晶的证据：50 m处的样品主要通过多晶化作用，而170 m处的样品主要通过晶界迁移发生。所有分析样品的晶体学优选取向（从表面观察）通常显示垂直于表面的单个c轴簇。一环相交的单个簇在140-170米发生用的紧密簇一个-垂直于腰带的轴。我们将<140 m处的晶体学择优取向（CPO）的变化解释为与垂直压缩和水平面上的剪切有关，而腰围CPO的深度> 140 m是水平延伸的结果。根据从探地雷达获得的数据，努纳塔克群岛的基岩地形可能在研究区域内产生了张应力状态。结果表明，由于外部运动学控制，例如在基岩中出现一个小峰，在埋葬期间可能发生变化的应力状态。