I still don&#x27;t know what &quot;like this&quot; means. I think the isotopic difference in coal layers is exactly like this. I think this quote from <a href="http:&#x2F;&#x2F;link.springer.com&#x2F;referenceworkentry&#x2F;10.1007&#x2F;978-1-4020-9212-1_120?no-access=true" rel="nofollow">http:&#x2F;&#x2F;link.springer.com&#x2F;referenceworkentry&#x2F;10.1007&#x2F;978-1-40...</a> &quot;Isotopes and Geobiology&quot; (2001):<p>&gt; It has long been recognized (e.g., Thode et al. (1949), Craig (1953) and Wellman et al. (1968)) that biological processes significantly fractionate the isotopes of C, N, and S, leading to characteristic biosignatures in sedimentary rocks that will be more or less preserved in the geological record. In the following, a brief overview is given of the major isotope fractionation processes in the biosphere and the geosphere.<p>is also &quot;like this&quot;. But there&#x27;s a 50 year head start with those elements.<p>I imagine that Ca and other elements are similar.