# Which of the following principles are key to relative dating

Note that unconformities, which on the diagram above are symbolized by the irregular lines, are indicated by dashed lines in the column below.

Also, the formations that appear on the simplified stratrigraphy diagram above are marked in the table with the number that corresponds to the diagram.

There is a definite mathematical relationship between the ratio of the amount of daughter product isotope to the amount of radioactive parent isotope, and the number of half-lives that have elapsed.

The relationship is non-linear, involving a logarithmic function.

Sandstone and shale, much of it red in color, with river channel cross-beds, stream ripples, and pond desiccation cracks.

Also contains layers of white gypsum where ponds, lakes or coastal lagoons underwent extensive evaporation. Fossils of plants, mostly ferns, and quadruped footprints have been found. The upper part of the group is non-marine and tracks of quadrupeds are found on bed tops.

By the definition of a half-life, the amount of parent isotope at each half-life is half of what it was before the half-life elapsed.

As the amount of parent isotope decreases by radioactive decay, the amount of the daughter isotope increases commensurately.

(In reality, rocks, minerals and other geologic materials can be checked to see if the isotope system remained closed, rather than assuming so.) At time zero, 100% of the isotopes are the parent isotopes.Each geologic formation in the sequence is briefly described.This is the type information that geologists use to construct geological histories.Therefore, at any time, the total of parent isotope fraction and daughter isotope fraction add up to 1.Similarly, the percentage of parent isotope percentage and daughter isotope percentage add up to 100 at all times.