It&#x27;s new because the field is only about 20 years old and everything in it is new. I gave you a link to one source, with details. Here&#x27;s the link again to that 2005 piece from University of Wisconsin-Madison <a href="http:&#x2F;&#x2F;www.geology.wisc.edu&#x2F;outcrop&#x2F;05&#x2F;05_pdfs&#x2F;11%20Iron%20Isotopes.pdf" rel="nofollow">http:&#x2F;&#x2F;www.geology.wisc.edu&#x2F;outcrop&#x2F;05&#x2F;05_pdfs&#x2F;11%20Iron%20I...</a> :<p>&gt; [In 1996] there was almost no information on the isotopic composition of iron. Previous studies had not been able to identify naturally occurring mass dependent fractionation, within the error of the mass spectrometry measurements. Therefore it was necessary to develop new analytical methods that were highly precise.  ... . Although the field of Fe isotopes is currently in its developmental stage, much like oxygen isotopes was five decades ago; it is rapidly becoming a common geochemical tool.<p>Here&#x27;s a PhD thesis from 2004, <a href="http:&#x2F;&#x2F;dspace.mit.edu&#x2F;handle&#x2F;1721.1&#x2F;53550" rel="nofollow">http:&#x2F;&#x2F;dspace.mit.edu&#x2F;handle&#x2F;1721.1&#x2F;53550</a> , which concludes &quot;The observed range in the Fe isotopic composition of the natural samples including biological and aqueous samples demonstrates that significant and useful fractionation is associated with Fe biogeochemistry in the environment&quot;. Note that the author received a MS from University of Wisconsin-Madison, which the 2005 article is about, and the New Yorker piece also concerns the Wisconsin group.<p>So looking to a more recent Nature article which doesn&#x27;t mention direct ties to the Wisconsion group, <a href="http:&#x2F;&#x2F;www.nature.com&#x2F;ncomms&#x2F;2013&#x2F;130719&#x2F;ncomms3143&#x2F;full&#x2F;ncomms3143.html" rel="nofollow">http:&#x2F;&#x2F;www.nature.com&#x2F;ncomms&#x2F;2013&#x2F;130719&#x2F;ncomms3143&#x2F;full&#x2F;nco...</a> titled &quot;Distinct iron isotopic signatures and supply from marine sediment dissolution&quot; (2013):<p>&gt; Microbial sediment respiration supports a major flux of dissolved and isotopically light Fe to the global ocean8, 9, 10, by catalysing the reductive dissolution (RD) of Fe oxyhydroxide minerals during organic matter decomposition11<p>You asked &#x27;And terrestrial?&#x27;, but you statement was a flat &#x27;there&#x27;s no evidence for it&#x27;, which includes in the ocean. Note that the New Yorker article says &quot;The ancient iron formations share many characteristics with modern limestones, which suggests that they accumulated in a marine environment&quot;.<p>But even then, you say &quot;Those would be something significantly new.&quot;<p>Yes, I believe that&#x27;s the reason the New Yorker wrote this piece. It even links to the new PNAS article at <a href="http:&#x2F;&#x2F;www.pnas.org&#x2F;content&#x2F;112&#x2F;27&#x2F;8193.abstract?sid=51595c5b-6aaf-4d85-af40-9562f2f70814" rel="nofollow">http:&#x2F;&#x2F;www.pnas.org&#x2F;content&#x2F;112&#x2F;27&#x2F;8193.abstract?sid=51595c5...</a> , which was published only 5 months ago, which says:<p>&gt; The continental Fe source is best explained by Fe mobilization on the continental margin by microbial dissimilatory iron reduction (DIR) and confirms for the first time, to our knowledge, a microbially driven Fe shuttle for the largest BIFs on Earth.<p>So again, could you explain what you mean by &#x27;not supported by anything else we know about this time period, or life on Earth in general&#x27;?