A comparative study of sediment characteristics of Sand River and Nzhelele River in Limpopo Province, South Africa

Abstract

To describe a sediment and possibly learn more about its creation and depositional processes, grain size statistics might be used. In order to understand the hydrodynamic conditions, mode of transit, and deposition of detrital sediments, grain size analysis is a dynamic sedimentological tool. Fluvial scientists are particularly interested in understanding the relationships between river systems that have been subjected to a variety of forcing factors, such as climate, tectonics, and sea level variations. This study examined the textural, particle size, and mineralogical characteristics of the sediments from the Sand River and the Nzhelele River. At the mouth of each chosen river, a collection of recently deposition sediments was collected to get a representative sample of the watershed. With particular attention paid to Sand River and Nzhelele River. The study's objectives included identifying the grain size distribution pattern of the sediments from Sand River and Nzhelele River and evaluating the mineralogical makeup of the coarse fraction of the sediments from Sand River and Nzhelele River in order to achieve the study's overall goal. In accordance with the "sand suite" methodology, sediments were collected. Using an Excel spreadsheet, the dry and wet sieve methods of grain size analysis were carried out and tabulated, and Gradistat was used to determine Folk and Ward's parameters. The sediments were analysed using a sieve with a 14 Phi-scale (Φ) interval and interpreted using an Excel spreadsheet. The Folk and Ward statistical parameters (mean, standard deviation, skewness, and kurtosis) were calculated using the Gradistat statistics tool. A key factor in the mechanics of sediment travel is a sediment particle's form, which can provide insight on some of the particle's past movement. The Hydrometer method was used to analyze the particle size of sediments to estimate their percentage sand, silt, and clay content. Once the distribution of sand, silt, and clay had been determined, the sediment was classified according to its textural triangle. Using an X-Ray Diffraction (XRD) spectrometer, the mineralogical composition of sand, fine powder, and coarse fraction samples was analyzed semi-quantitatively. This analytical technique revealed the crystallinity and concentration of mineral phases in the samples. The unimodal grain size distribution, which is indicative of a moderate energy environment at Sand River, shows that medium sand to fine sand predominates. The monomodal particle size distribution in Nzhelele River, which is a sign of a high energy environment, shows that very coarse to medium sand predominates there. The majority of the alluvial deposits were sandy, and they were rich in actinolite, quartz, albite, orthoclase, muscovite, and kaolinite. The dominating minerals were leftovers from the minerals in the original parent material and were present in both the sand and silt fractions. They are therefore referred to as fundamental minerals. Quartz (SiO2), a mineral with high weather resistance, comes in first. Albite, Orthoclase, Muscovite, Kaolinite, and Actinolite are other minerals that are frequently found, but in smaller proportions. The mineral makeup of the investigated deposits showed that the minerals at Nzhelele River were Quartz (49.3%), Albite (29.8%), Orthoclase (18.1%), Muscovite (2.1%), and Kaolinite (0.6%), whereas the minerals at Sand River v were Quartz (38.9%), Albite (38.2%), Orthoclase (20.1%), Muscovite (2.5%), Kaolinite (Nil), and Actinolite (0.4%). The two river sediment samples under study had a lot of quartz, according to the chemical composition data. The distance traveled depends on the size of the sediments in rivers; the smaller the size, the longer the journey. The majority of river sediments range from gravel to sand. As sediments typically become coarser with an increase in the energy of the transporting medium, this suggests that the sediments were transported under high energy conditions (Folk, 1974). Due to their longer distance of travel, finer sediments in Sand River were present in greater amounts, but coarser sediments were present in greater amounts in Nzhelele River due to their shorter travel distance. According to the current study, sediments' various textural traits can provide crucial hints for comprehending both their depositional settings and the mechanisms underlying movement. Based primarily on the information supplied by the grain size distribution curves, mineral composition, log-cumulative curves, and grain size distribution histograms, the current Sand River and Nzhelele River samples have been interpreted. According to the grain size distribution, the Nzhelele River sediments are primarily coarse-grained, poorly sorted, leptokurtic, and platykurtic in character, while the sediments from the Sand River are primarily fine-grained, moderately sorted, mesokurtic, and nearly symmetrical. The sediments' fine-sand makeup indicates that fairly lowenergy conditions predominate in the research area. The sediments' well-sorted to moderatelysorted character points to an abrupt winnowing and back and forth migration by the depositing processes. A riverine input and mixing of similar modal fractions may be indicated by the dominance of the nearly symmetrical category. The sediments' unimodal distribution demonstrates the stable depositional process that underwent the deposition of the Sand River and Nzhelele River sediments.