Micromorphology Report
Introduction
Micromorphology allows full examination of the arrangement of the particle, matrix, as well as other parts of unconsolidated sediments. Examining thin sections of deposits usually at low magnifications enables micromorphology to offer insights into the architecture of sediments, which lead to the internal arrangement of the components that are observed (van der Meer & Menzias, 2011, p. 213).
A micromorphological description starts with the characterization of the thin section, which helps to quickly draw attention to the structures with intermediate sizes under the microscope. Afterward, the analysis shifts to textual description with a focus on grain size, shape, composition as well as the distribution of the grains alongside plasma to the extent that can be observed (Menzies & Ellwanger, 2012, p. 96). These aspects inform depositional, deformational, as well as stress history of the sample under review.
Thin Section Description
The thin section has a water escape structure with a void that forms a channel due to compression (Appendix 2). The clay/silts at the void have different sizes where deposits/sediments at the bottom of the void have the smallest sizes and more delicate texture while those at the top have larger sizes and are coarser. The silts appear to have been deposited at the end of the void. The large-sized grains are very rounded while the smaller grains rounded. Likewise, some grains are randomly sorted and distributed over the structure. Notably, the grains differ in their sizes, with the larger ones appearing like quartz. Furthermore, the thin section has a fold, micro shears, and broken clasts that are not well-developed. Overall, the structure has a clay-rich matrix (Appendix 2).
Interpretation (Processes and Environment)
Textual Analysis
The roundness of rock or soil particles is always taken as the overall abrasional history of the particle that is being examined (Kleesment, 2009, p.71). Quartz is the reference mineral when performing analysis for grain-shape. The shape of quartz changes because of processes such as mechanical as well as a chemical that happens when there is erosion, transportation, as well as a deposition. Importantly, the roundness of rocks reveals the magnitude of clastic particles abrasion as well as evidence of medium, duration, and distance covered during transportation.
The dominant grains from the sections from the sample provided for this analysis indicate that most of the grains in the sample have sizes of less than 5mm. Also, there are microfabric grains with less 0.5 mm in format, which were structured horizontally and grains with 0.5mm, which are rounded. In terms of microfabric structure for grains that with sizes greater than 0.5mm, the orientation is horizontal. Most of the grains from the sample provided are fine sands, which have dimensions that are less than 0.5 mm. Microshears are detectable microstructures forming discontinuities in sediments (Menzis & Meer, 2018, p. 769). The micro shears on the matrix can be attributed to the separation of grains.
The size of particles directly depends on the environmental setting, the agent that is transporting the particles, the length as well as the time of transportation, and the conditions of depositions (Lopez, 2017, p. 341). Put, the size of the grain is attributed to several external factors that act locally or regionally. Joint sets with notable uniform orientation, close and continuous spacing, may lead to the presumption that a mass of rock mass is isotropic. On the other hand, a discontinuous mass of rock is regarded as anisotropic materials where the distribution of joints sets comprise of a few directions as well as appropriate spacing (Jiang et al., 2014, p. 7).
Texture implies the nature of the grains or crystals that form the rock structure. Beautiful grained rocks have portions of rock matrix with glasses that cannot be seen with the unsupported eye. In terms of texture, the grain size of beautiful stones is usually less than 1mm. The smaller crystals are often referred to as the matrix (Menzies & Zaniewski, 2003, p. 36). The section provided for the analysis reveals that the texture of the form is fine while the density was moderate, and the high distribution of grains in the model.
Structural Analysis
Voids are open spaces that exist on grounds exposed to sudden ground conditions in instances that of engineering geology. Voids can form naturally or through the activities of humans. The examples of voids include fissures, blisters, vughs, channels, and chambers. Commonest natural voids are found in soluble rocks after dissolutions which generate crevices that can be only a few meters wide to large caves (Menzies & Zaniewski, 2003, p. 39). Voids can be characterized by different structural elements, including folds, sill, dikes, fault, shear, bedding, dropstone, and tile structures.
The thin section provided for this analysis depicts a structure that appears to have a void for water escape (Appendix 1). Importantly, the structure has formed a channel following the process that had ensured. Notably, the rock structure appears to have gone through high water compression (Appendix 2). The resulting fold is formed as a result of slump and compression, which led to the formation of the void. A planar zone consists of high strained rocks than those in the adjacent areas. The shear zone, in this case, appears to have been formed through folding (Appendix 1).
Evaluation of the Micromorphology Technique (Advantages/Limitations)
The first advantage of the micromorphology is that it is a method that is applied in situ. The material is usually not disaggregated, and the thin sectioning supports the analysis of particles in the original form. Even though the sample is obtained from the field, it remains intact without any deformation, and the materials found in the sample retain their unique position.
The second advantage of micromorphology as a technique is that it permits exact compositional as well as positional analysis of a sample. When examining thin sections, there is an increased possibility of locating the microfossils. For instance, it becomes easy to determine whether the microfossils exist in the laminae or the intraclasts.
Lastly, micromorphology helps to relate microstructures with various processes such as reworking silts by wind and melting debris from ice. Mimicking the processes under conditions that are controlled in the laboratory helps to establish diagnostic microstructures.
Conclusion
The thin structure has helped to gain insights into the microstructure of the sediment. The analysis reveals grains of different sizes, different kinds of roundness, domains, shears, and the creation of a void through pressure. Importantly, the study shows that micromorphology is advantageous because it helps to understand different processes such as melting ice debris, allows sample analysis, and avoids disaggregation.
List of References
Jiang, Q, Feng, X-t, Hatzor, YH, Hao, X-j & Li, S-j 2014, “Mechanical anisotropy of columnar jointed basalts: An example from the Bihetan hydropower station, China. Engineering Geology, Vol. 175, pp. 35-45.
Klement, 2009, “Roundness and surface features of quartz grains in Middle Devonian deposits of the East Baltic and their palaeogeographical implications.” Estonian Journal of Earth Sciences, vol.58, no.1, 71-84. DOI: 10.3176/earth.2009.1.07
Lopez, GI, 2017, “Grain size analysis.” Encyclopedia of Geoarchaeology, pp.341-348. DOI 10.1007/978-1-4020-4409-0
Menzis, J & Meer, JJM 2018, “Micromorphology and microsedimentology of glacial features.” Elsevier. http://dx.doi.org/10.1016/B978-0-08-100524-8.00036-1
Menzies, J & Zaniewski, K., 2003, “Microstructures within a modern debris flow deposit
derived from Quaternary glacial diamicton—a comparative micromorphological
study.” Sedimentary Geology, vol. 157, pp. 31–48
Menzies, J & Ellwanger, D, 2012, “Micromorphology of the Mannheim Formation taken from the UniNord Core, Heidelberg Basin Depocentre, Upper Rhine Graben.” LGRB-Informationen, 26, pp. 87-106.
van der Meer, JJM & Menzies, J 2011, “The micromorphology of unconsolidated sediments.” Sedimentary Geology, vol. 238, pp. 213-23.
Appendices
Appendix 1: Notes Taken during thin section assessment
Appendix 2: Thin Section for Analysis