Laboratory Manual for Introductory Geology 4e

FIGURE 12.4 Features that indicate the top or bottom of a sedimentary bed (continued).
(b) Graded beds: The coarsest grains of sediment settle first and lie at the bottom of the bed. They are followed by progressively smaller grains,
producing a size gradation.
(c) Symmetric ripple marks: The sharp points of the ripple marks point toward the top of the bed.
FIGURE 12.5 Impressions can indicate the top or bottom of a sedimentary bed.
Features such as dinosaur footprints (left) and raindrop impressions (right) formed when something (here, a dinosaur and raindrops,
respectively) sank into soft sediment exposed at the Earth’s surface.
12.2 PHYSICAL CRITERIA FOR DETERMINING RELATIVE AGE
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