Lab 5 GY 402 Sedimentary Petrology (2012) Immature Siliciclastic Sedimentary Rock Thin-sections Litharenite and greywacke in thin section (field of view for each approximately 2 mm). From Williams, H., Turner, F.J and Gilbert, C.M., 1954. Petrography. W.H. Freeman & Co., 406pp. Introduction: Immature siliciclastic sedimentary rocks are those that contain significant amounts of “unstable” particles, particularly feldspars. Overall, these rocks are usually composed of mixed silicate grains (quartz, feldspars, ferromagnesium minerals, lithic grains etc.) that are subangular to subrounded, and less well sorted than their mature counterparts. They are commonly red in color (but not always) and may be enriched in matrix or cemented by a variety of different minerals. The most common immature sandstones include litharenite and feldspathic litharenite (i.e., arkose). This lab will also introduce you to siliciclastic rocks that contain significant amounts of "matrix" (e.g., wackes). Lab exercise (do in your note books, not re-doable):
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section reports, lithic grains, common immature sandstones