Quantification of particle shape by an automated image analysis system: a case study in natural sediment samples from extreme climates
- 155 Downloads
Sediment particle shape and microtexture are key parameters utilized for characterizing sediment transport and weathering (both physical and chemical) processes, which in turn are governed by environmental conditions such as climate. Assessing particle shape often involves either qualitative descriptors or time-consuming measurements of shape parameters by a human operator. This study employs a state-of-the-art, quantitative shape analysis instrument known as the “Morphologi G3” from Malvern Instruments, an automated microscope system capable of determining quantitative shape parameters via static image analysis of > 1000 particles in less than two hours. This instrument captures 2D projected images of particles and provides information on grain size measurements such as circle-equivalent diameter, length, width, perimeter, and area, as well as shape parameters such as circularity and convexity. As a case study, we conducted analyses on mud- and sand-sized particles collected from fluvial/alluvial systems of end-member climates to assess variations in sediment particle morphology potentially related to climate and/or transport distance and processes. Sediment samples were collected from fluvial systems in four contrasting climates: hot-arid (southeastern California, USA), hot-humid (eastern Puerto Rico), glacial-arid (proglacial stream of the Dry Valleys, Antarctica), and glacial-humid (Austerdalen proglacial stream, Norway). Results provide quantitative constraints on shape differences that relate to climate and transport, even for very fine-grained sand and mud size fractions. Comparison of the circularity of sediment particles from the four end-member climates indicates that the very fine sand fractions reflect differential physical abrasion and transport processes, whereas the morphology of the mud fraction seemingly imprints chemical weathering processes. We conclude that this new technique has great potential to further document impacts of climate on particle shape with applications to both modern and deep-time depositional systems.
Key wordsparticle shape morphology image analysis glacial sediment circularity convexity
Unable to display preview. Download preview PDF.
- Lewis, A.R., Marchant, D.R., Kowalewski, D.E., Baldwin, S.L., and Webb, L.E., 2006, The age and origin of the Labyrinth, western Dry Valleys, Antarctica: evidence for extensive middle Miocene subglacial floods and freshwater discharge to the Southern Ocean. Geology, 34, 513–516.CrossRefGoogle Scholar
- Lutro, O. and Tveten, E., 1996, Geological map of Norway, berggrunskart Årdal M 1: 250,000. Geological Survey of Norway, Trondheim.Google Scholar
- Mahaney, W.C., 2002, Atlas of sand grain surface textures and applications. Oxford University Press, Oxford, 256 p.Google Scholar
- Malvern Instruments Ltd., 2015, Morphologi G3 user manual. Worcestershire, 268 p.Google Scholar
- Pye, K. and Mazzullo, J., 1994, Effects of tropical weathering on quartz grain shape: an example from northeastern Australia. Journal of Sedimentary Research, 64, 500–507.Google Scholar
- Remeika, P. and Lindsay, L., 1992, Geology of Anza-Borrego: edge of creation. Sunbelt Publications, San Diego, 208 p.Google Scholar
- Rogers, C., Cram, C., Pease, Jr. M., and Tischler, M., 1979, Geologic map of the Yabucoa and Punta Tuna quadrangles, Puerto Rico. U.S. Geological Survey Miscellaneous Geologic Investigations Map I, San Diego, USA.Google Scholar
- Strand, R.G., 1962, Geologic Map of California: San Diego-El Centro Sheet. California Division of Mines and Geology.Google Scholar