Because of the soil the rocks are in. If They stayed in that soil for a while which affected the compounds, shifting the mineral composition.
Stable isotopes refers to those isotopes that do not undergo radioactive decay. Oxygen atoms with atomic number of 16 and 18 are examples of stable isotopes. These isotopes of oxygen are usually found in substances such as polar ice and calcite. These substances are usaually measure with isotope fractionation and the ratios obtained are used to estimate water temperature of ancient oceans. From this, scientists can find out facts about ancient climates,
<h3>option A is the correct one </h3>
hope this helps you out