Prominent deformation features and interpretation of sediment core CRP-2/2A (Table 1)@en

Sediment deformation features in CRP-2/2A were described during normal logging procedures and from core-scan images. In this paper the origin of soft-sediment folding, contorted bedding, microfaulting, clastic dykes, shear zones and intraformational breccias is discussed. The features have a stratigraphic distribution related to major unconformities and sequence boundaries. Hypotheses for the origins of sediment deformation include hydrofracturing, subglacial shearing, slumping, and gas hydrate formation. Shear zones, microfaults, clastic dykes and contorted bedding within rapidly deposited sediments, suggest that slumping in an ice-distal environment occurred in the early Oligocene. A till wedge beneath a diamictite at 364 mbsf the mid-Oligocene section represents the oldest evidence of grounded ice in CRP-2/2A. Shear zones with a subglacial origin in the early late Oligocene and early Miocene sections of the core are evidence of further grounding events. The interpretation of sediment deformation in CRP-2/2A is compared to other Antarctic stratigraphic records and global eustatic change between the late Eocenel/early Oligocene and the middle Miocene.研究人员通过常规测井流程（normal logging procedures）与岩芯扫描图像（core-scan images），对CRP-2/2A岩芯中的沉积物变形特征（sediment deformation features）展开了描述。本文针对软沉积褶皱（soft-sediment folding）、扭曲层理（contorted bedding）、微断层（microfaulting）、碎屑岩脉（clastic dykes）、剪切带（shear zones）以及层内角砾岩（intraformational breccias）的成因展开探讨。上述变形特征的地层分布（stratigraphic distribution）与重大不整合面（major unconformities）及层序界面（sequence boundaries）密切相关。沉积物变形的成因假说涵盖水力破裂（hydrofracturing）、冰下剪切作用（subglacial shearing）、滑塌作用（slumping）以及天然气水合物形成（gas hydrate formation）。快速沉积地层（rapidly deposited sediments）内发育的剪切带、微断层、碎屑岩脉与扭曲层理，指示渐新世早期（early Oligocene）的冰远环境（ice-distal environment）曾发生滑塌作用。渐新世中期（mid-Oligocene）层位中，海底以下364米（meters below seafloor, mbsf）处杂砾岩（diamictite）下方的冰碛楔（till wedge），是CRP-2/2A中记录固着冰（grounded ice）的最古老证据。岩芯晚渐新世早期（early late Oligocene）与早中新世（early Miocene）层位中，具有冰下成因的剪切带，为后续的固着冰事件提供了佐证。本文将CRP-2/2A的沉积物变形成因解释，与其他南极地层记录（Antarctic stratigraphic records）以及始新世晚期（late Eocene）/渐新世早期至中中新世（middle Miocene）期间的全球海平面变化（global eustatic change）进行了对比分析。