Relative dating rock quiz
Load casts form as the result of downsinking of sandstone or limestone into the mud beneath.Igneous rock, any of various crystalline or glassy rocks formed by the cooling and solidification of molten earth material.They conventionally are subdivided into categories based on mode of genesis.Structures that are produced at the same time as the sedimentary rock in which they occur are called primary sedimentary structures.Primary stratification in sediments and sedimentary rocks can be cross-bedded (cross-stratified), graded, and imbricate and can also display climbing laminae, ripples, and beds. This variety of bedding results from a check in the velocity of the transporting agent, and thus coarse-textured sediment (gravel, for example) is deposited first, followed upward by pebbles, granules, sand, silt, and clay.It is commonly associated with submarine density currents.).
Primary sedimentary structures are particularly useful because their abundance and size suggest the probable transporting and depositional agents.They include such features as ripples (ripple marks), climbing ripples, rills, pits, mud cracks, trails and tracks, salt and ice casts and molds, and others.Bedding-plane markings and irregularities can be allocated to one of three classes: (1) those on the base of a bed (load and current structures and organic markings), (2) those within a bed (parting lineation), and (3) those on top of a bed (ripple marks, pits, impressions, mud cracks, tracks and trails of organisms, and others).In addition to sedimentary structures that are normally associated with bedding planes, there are other such structures that result from deformation during or shortly after sedimentation but before induration of the sediment into rock.These are nontectonic features—i.e., they are not bends and folds brought about by metamorphism or other such causes.