Exploration Insights Great Geos ebook | Page 68

68 | Great Geologists founding the science of During the next few years sedimentology. He first Sorby published a series noticed current-formed of brilliant papers on the structures whilst sheltering petrography of sandstones from the rain in a quarry in and limestones, but his 1847. This was at the time interests also included that he was researching fluvial igneous and metamorphic geomorphology for his first rocks (for example, he publication, and he was struck was the first to describe by the similarities between the deformation of ooids the structures he observed and crinoid ossicles in in the rock and those he had lightly metamorphosed observed forming in modern carbonates). He determined sediments. Over the next different types of detrital few years, he systematically quartz and how this could observed and described be linked to sediment sedimentary structures at provenance. In his papers outcrop and conducted flume on carbonate rocks he tank experiments at home described the conversion Thin-section of a calcareous cemented sandstone. Several different to understand their genesis. of aragonite to calcite, types of detrital quartz grains are present which could be related to A series of publications dolomitization, different different sediment source regions, a notion that Sorby pioneered. emerged - for example “On phases of cementation the structures produced by and recognized that the the current present during the deposition of stratified rock” coccoliths that form chalk are of organic origin. He described published in 1859, but a full summary of this line of endeavour many of the constituent grains of carbonate rocks including was not published until his monumental final paper in 1908, ooids and a variety of bioclasts. “On the application of quantitative methods to the study of the During a visit to Germany in 1860, Sorby met a young German structure and history of rocks.”. This masterly synthesis of the geologist named Ferdinand Zirkel who was inspired by the new hydrodynamic interpretation of sedimentary structures reviewed science of petrography and applied it systematically to igneous their relationship with current velocity, the angles of repose of rocks – the results are summarized in the 1866 publication different sediments and the settling velocity of grains in water. It Lehrbuch der Petrographie. By this time Sorby’s interests were also described soft sediment deformation, the measurement of already moving on, first to the petrography of meteorites and porosity and the exact determination of structural deformation. then to man-made metals. The use of fluid inclusions in minerals to understand the Sorby recognized that metals had a crystalline structure and temperature of crystallization is now a well-established the composition of steel could be determined by microscopic technique in a variety of geological studies. Sorby was, once examination once it had been etched by acid. His understanding again, a pioneer in developing this technique, publishing a key of the composition of steel and what gave it its strength paper “On the microscopical structure of crystals, indicating the revolutionized its manufacture. He later remarked “In those early origin of minerals and rocks” in 1858. days, if a railway accident had occurred and I had suggested that In 1878, Sorby purchased a yacht, The Glimpse. He had it fitted the company should take up a rail and have it examined under out as a floating laboratory and, over a series of twenty-five the microscope, I should have been looked upon as a fit man to summers, proceeded to survey the eastern coast of England, send to an asylum. But that is what is now being done.” carrying out studies on coastal sediments and marine fauna. His Parallel to his petrographic studies, Sorby was engaged in intellectual curiosity seems to have been boundless. In 1892, a number of other lines of geologic research. Perhaps the he walked 1,200 miles in four months (aged 66) studying and most important of these was the recognition of sedimentary describing ancient buildings for his archaeological research. structures as indicators of past deposition processes, thereby