A METHODOLOGY FOR CHARACTERIZING AND CLASSIFYING UNCONSOLIDATED INORGANIC FINE-GRAINED SEDIMENTS

The grain-size distribution characteristics are one key to classifying types of sediment and understanding the variations in depositional processes. However, the current grain-size based classification systems have not been able to distinguish fine-grain sediments with varying silt and clay content. In addition, the current classification systems do not consider mineralogy in the classification scheme or the subsequent implication of mineralogy to the mechanical behavior of the sediment. This study proposes a new classification scheme to describe the grain-size distribution (GSD) characteristics of unconsolidated inorganic sediments that allows the clay mineral composition to be included, and allows the mechanical behavior to be inferred as well. The proposed scheme relies on the linear relationship between the total amount of percent Fines and the silt fraction. This simple correlation quantifies the behavior of the GSD curve, which analysis showed to be controlled by the ratio of the clay fraction to the silt fraction. The classification scheme uses plasticity indices (i.e. liquid limit and plasticity index) as proxies for clay mineralogy. Combining plasticity and grain size characteristics, the proposed classification scheme allows for more detailed characterization of sedimentary environments. The proposed scheme helps to understand, interpret, and model mutual influence between variations of the sedimentary environments and their resultant sediment properties