Average dip directions from intervals of dipmeter log in drill hole CRP-2A

Bedding dips in the CRP-2A drillhole were determined in two ways (1) analysis of a dipmeter log, and (2) identification of bed boundaries on digital images of the outer core surface. The two methods document the downhole increase in structural dip, to a maximum of 15° in the lowest 150 m of the hole. Dipmeter data, which are azimuthally oriented, indicate a 75° azimuth for structural tilting, in agreement with seismic reflection profiles. Core and log dips indicate that structural dip increases by 5-7° between 325 and 480 mbsf. Both, however, also exhibit high dip inhomogeneity because of depositional (e.g., cross bedding) and post-depositional (e.g., softsediment deformation) processes. This variability adds ambiguity to the search for angular unconformities within the CRP-2A drillhole. Dip directions of different lithologies are generally similar, as are dip directions for the four kinds of systems tracts. Downdip azimuths of sands and muds are slightly different from those of diamicts, possibly reflecting the divergence between ENE offshore dip and ESE glacial advance.针对CRP-2A钻孔的层理倾角，本研究采用两种方法进行测定：其一为倾角测井曲线（dipmeter log）解析，其二为岩心外表面数字图像的层理界面识别。两种方法均显示，井下构造层理倾角随深度逐渐增大，在钻孔最底部150米范围内达到15°的最大值。具备方位定向属性的倾角测井数据显示，构造倾斜的方位角为75°，该结果与地震反射剖面的分析结果一致。岩心层理倾角与测井倾角数据均表明，在海底以下米数（meters below sea floor，简称mbsf）325米至480米区间内，构造层理倾角增大5°至7°。但受沉积作用（如交错层理（cross bedding））与沉积后作用（如软沉积变形（softsediment deformation））的影响，两类数据均表现出显著的倾角非均质性。这种倾角变化性为CRP-2A钻孔内角度不整合（angular unconformities）的识别工作增添了不确定性。不同岩性的层理倾角方向整体较为一致，四类体系域（systems tracts）的倾角方向亦呈现相似特征。砂质与泥质沉积物的倾向方位角与混杂堆积物（diamicts）存在细微差异，这可能反映了东东北（ENE）近海倾向与东东南（ESE）冰川推进方向之间的分异。