Grain size distribution, carbon content and wet bulk density of sediment cores in the equatorial Atlantic and the Norwegian Sea

Near-surface sediments from the equatorial east Atlantic and the Norwegian Sea exhibit pronounced shear strength maxima in profiles from the peak Holocene and Pleistocene. These semi-indurated layers start to occur at 8-102 cm below the sediment surface and can be explained neither by the modal composition nor by the effective overburden pressure of the sediments. However, scanning electron microscope and microprobe data exhibit micritic crusts and crystal carpets, which are clearly restricted to (undisturbed) samples from indurated layers and form a manifest explanation for their origin. The minerals precipitated comprise calcite, aragonite, and in samples more proximal to the African continent SiO2 needles, and needles of as yet unidentified K-Mg-Fe-Al silicates, crusts of which dominate the indurated layers in the Norwegian Sea. […]

近表层沉积物在赤道东大西洋和挪威海地区的剖面中，显示出明显的剪切强度峰值，这些峰值出现在全新世和更新世的顶峰时期。这些半硬化的层状结构自沉积表面以下8-102厘米处开始出现，其形成既不能由沉积物的平均组成解释，也不能由沉积物的有效上覆压力解释。然而，扫描电子显微镜和微探针数据揭示了微晶外壳和晶体地毯，这些特征明显局限于（未受干扰的）硬化层样本中，并为它们的起源提供了明确的解释。沉淀的矿物包括方解石、菱镁矿，在靠近非洲大陆的样品中还包括SiO2针状结构，以及尚未确定的K-Mg-Fe-Al硅酸盐针状结构，其中后者在挪威海的硬化层中占主导地位。