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Who we are. Geologic materials. Rocks (including high and low porosity & crystalline), unlithified or poorly lithified sediments, and soils. Form when the rock forms, thus provide a record of geologic processes May be present in sedimentary, volcanic, and intrusive rocks
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Geologic materials Rocks (including high and low porosity & crystalline), unlithified or poorly lithified sediments, and soils
Form when the rock forms, thus provide a record of geologic processes May be present in sedimentary, volcanic, and intrusive rocks The former two cases generally have better way-up indicators Modify - sometimes obliterate - primary structures Commonly, though not always, oblique to primary structures May be continuous (pervasive) or discontinuous Primary versus Secondary Structures
Why we care about primary structures in a structural geology class • Being able to distinguish primary from secondary structures is critical to reading rock record • Geologic history (tectonics) • Way-up indicators • Material controls on deformation
Description • What is the rock type? • What do structures look like (e.g. shape, continuous or discontinuous, etc.)? • Is it homogeneous or heterogeneous? Isotropic or anisotropic? • Is it primary or secondary? • How would you interpret this structure? Can it be used as a way-up indicator?