Calcium carbonate content, brightness and color reflectance of ODP Site 188-165 and Hole 188-1167A

We measured and analyzed near-ultraviolet/visible/near-infrared spectral data from core samples recovered from Ocean Drilling Program Sites 1165 (Wild Drift) and 1167 (Prydz Channel Trough Mouth Fan) using our laboratory-grade spectrophotometer to help determine temporal mineralogical changes downhole. These measurements included closely spaced (~10 cm) samples for the section from 0 to 54.17 meters below seafloor (mbsf) in Hole 1165B, which is the Pliocene-Pleistocene age interval being studied in detail by the High-Resolution Integrated Stratigraphy Committee (HiRISC). We also determined calcium carbonate content for all samples in this HiRISC interval. The Pleistocene and uppermost Pliocene sediments (0-10 mbsf) show wide carbonate fluctuations ranging from 0 to 37 wt%; however, below 10 mbsf, the carbonate content is generally zero. To examine the major components that contribute to spectral variability in the holes, the first-derivative values for all samples from Sites 1165 and 1167 were assembled into a single matrix and the matrix was then factor analyzed after being subject to a varimax rotation. For Sites 1165 and 1167, factoring first-derivative values from 255 to 745 nm produced the most easily interpretable results, with five factors that explain ~92.5% of the total variance in the data set. Factor 1 incorporates both goethite and chlorite, meaning that scores for this factor will be high where these two minerals covary. Factor 2 is interpreted as organic matter. Factor 3 appears to be a combination of clay minerals, possibly montmorillonite and illite. Factor 4 is interpreted as the mineral maghemite, a polymorph of hematite. Factor 5 is the mineral hematite.我们使用实验室级分光光度计，对大洋钻探计划（Ocean Drilling Program）1165站位（Wild Drift，荒野漂移体）与1167站位（普里兹湾槽口扇，Prydz Channel Trough Mouth Fan）获取的岩芯样品的近紫外/可见/近红外光谱数据进行了测量与分析，以探明井下矿物组成的时间序列变化。本次测量涵盖了1165B孔海底以下0至54.17米（meters below seafloor，以下简称mbsf）层段的密集采样样品（采样间距约10厘米（cm）），该层段属于上新世-更新世地层，正是高分辨率综合地层学委员会（High-Resolution Integrated Stratigraphy Committee，HiRISC）重点研究的对象。我们还测定了该HiRISC研究层段内所有样品的碳酸钙含量。更新统与最顶部上新统沉积物（0~10 mbsf）的碳酸钙含量波动幅度极大，介于0至37重量百分比（wt%）之间；而在10 mbsf以深的地层中，碳酸钙含量基本为0。为探究两个钻孔中导致光谱变化的主要组分，我们将1165与1167站位全部样品的一阶导数值整合为单一矩阵，并对方差最大旋转后的矩阵开展因子分析。针对1165与1167站位，选取255~745纳米（nm）波段的一阶导数值进行因子分析可得到最易于解释的结果，共提取出5个因子，其累计可解释数据集总方差的约92.5%。因子1同时涵盖针铁矿与绿泥石，即当这两种矿物协同变化时，该因子的得分会较高。因子2被判定为有机质。因子3似乎为黏土矿物组合，大概率为蒙脱石与伊利石。因子4被判定为磁赤铁矿——一种赤铁矿的同质多象变体。因子5为赤铁矿。