Description of recent sediments of Nile Delta, Red Sea and Gulf of Aden (Table 1-3)

The study of textural, structural, chemical, and physical properties of fine-grained recent marine sediments leads to the conclusion that only a few compositional factors are responsible for significant changes in mass physical characteristics in the upper meters below sea bottom. Fossil-induced porosity increases water content and liquid limit. It also seems to have partially influenced the plastic limit and plasticity index of calcareous sandy silts from the Red Sea and the western Gulf of Aden so that they become similar to the montmorillonite rich prodelta clays from the Nile Delta. Diagrams based on liquid limit and plasticity loose their original meaning in these cases. Activity of sediments rich in microorganisms can be higher than that of montmorillonitic clay.
The shear strength-depth relationship of normally consolidated sediments is surprisingly little influenced by changes in sand or clay content and clay mineralogy. Only high lime content, submarine erosion and beginning cementation increase the strength considerably. Erosional disconformities near the present surface can be deduced from the strength-depth curve when as little as 1 or 2 m sediment have been removed. Flat or irregular strength-depth curves indicate beginning cementation and probably discontinuous sedimentation, provided the composition of the material remains in some degree constant. In our samples diagenetic pyrite, but no recristallisation of carbonates could be detected under the microscope.
Underconsolidation and excess pore-water pressure, factors which tend to foster submarine slides, mud lumps, and diapiric folding, seem to be restricted Varito areas with mainly rapidly deposited, homogeneous or layered sediments. But where an abundance of burrowing organisms increases the vertical permeability of the sediment, normal consolidation and stable deposits are to be expected, at least in the upper meters below the present surface.
According to 14C-determinations on calcareous microorganisms the rate of deposition of the investigated sediments seems to range from 26 to 167 cm per 1000 years.

本研究针对细粒现代海洋沉积物（fine-grained recent marine sediments）的结构、构造、化学及物理性质开展系统分析，结果表明：海底以下数米浅层范围内，仅有少数组分因素可对沉积物的整体物理特性产生显著影响。
化石作用引发的孔隙度提升会增加沉积物的含水量与液限（liquid limit），且该作用似乎还对红海（Red Sea）及亚丁湾西部（western Gulf of Aden）钙质砂质粉土（calcareous sandy silts）的塑限（plastic limit）与塑性指数（plasticity index）存在部分影响，使其特性趋近于尼罗河三角洲（Nile Delta）富含蒙脱石（montmorillonite）的前三角洲黏土（prodelta clays）。在此类样本中，基于液限与塑性状态绘制的相关图表将失去原有的物理意义。富微生物沉积物的活性（activity）可能高于蒙脱石类黏土。
正常固结沉积物（normally consolidated sediments）的抗剪强度（shear strength）-深度关系，受砂粒含量、黏土含量及黏土矿物学（clay mineralogy）变化的影响极小。仅当出现高石灰含量、海底侵蚀作用及早期胶结作用（cementation）时，沉积物抗剪强度才会显著提升。当海底表层以下1至2米的沉积物被剥蚀后，可通过抗剪强度-深度曲线推断出侵蚀不整合面（erosional disconformities）。若沉积物组分在一定程度上保持稳定，则平缓或不规则的抗剪强度-深度曲线可指示早期胶结作用，且大概率伴随沉积间断。本次研究的沉积物样本中，显微镜下仅观察到成岩黄铁矿（diagenetic pyrite），未发现碳酸盐矿物的重结晶作用（recristallisation of carbonates）。
欠固结作用（underconsolidation）与超孔隙水压力（excess pore-water pressure），这两类易诱发海底滑坡（submarine slides）、泥砾（mud lumps）及底辟褶皱（diapiric folding）的因素，似乎仅局限于以快速沉积、均质或层状沉积物为主的瓦里托（Varito）区域。但当大量掘穴生物提升了沉积物的垂直渗透性时，即便在当前海底表层以下数米范围内，也可预期出现正常固结且稳定的沉积体。
基于钙质微生物的14C测年（14C-determinations）结果，本次研究涉及的沉积物沉积速率范围约为每千年26至167厘米。