All that glitters is n’t usuallygold , and the same is true for 183 million - twelvemonth - old fogy found in the Posidonia Shale . Moreover , while the researchers used to recall the shiny atomic number 79 coating on the fossils wasfool ’s gold , new research has bring out a more surprising answer .
The Posidonia Shale in southwest Germany is the source of many of these golden - hue fogy , particularly those of gentle - bodied sea life such assquidand ichthyosaur embryos that were around in the former Jurassic . These geological deposits curb soft - bodied conserve are know as Konservat - Lagerstätten and are extremely rare .
Previously it was thought that anoxic conditions helped to fossilize these specimen . While fool’s gold , also known as fool ’s amber , was think to be the source of this shine , a closer review has revealed more about the atmospheric condition in which these fossil were work .
Ammonite fossil from the Ohmden quarry, Posidonia shale lagerstätte. Image credit: Sinjini Sinha
“ When you go to the stone pit , golden ammonites glint out from black shale slab , ” said study co - author Rowan Martindale , an associate prof at the University of Texas at Austin Jackson School of Geosciences , in astatement . “ But amazingly , we struggled to find pyrite in the fossils . Even the fossils that looked gilded , are preserved as phosphate mineral with jaundiced calcite . This dramatically changes our view of this far-famed fossil deposit . ”
The squad used scanning electron microscopes to take a close expression at these shiny specimens . While the researchers did key out traces of microscopic fool’s gold crystals called framboids in the surrounding material , they found that in every specimen the fossils were mostly made up of phosphate mineral .
“ I expend days looking for the framboids on the fogy , ” said carbon monoxide gas - generator Sinjini Sinha , a doctorial student at the Jackson School . “ For some of the specimens , I look 800 framboids on the intercellular substance while there was maybe three or four on the fossils . ”
The makeup of these fossils reveals clues about the environment that they formed in zillion of eld ago . Pyrite forms under anoxic conditions , while the phosphate mineral need oxygen – this suggests that initially the sea floor was anoxic , helping to preserve the fossils , but that an influx of oxygen was involve to encourage the chemical substance process needed for this kind of fossilization .
“ It ’s been think for a long time that the anoxia make the particular preservation , but it does n’t straight serve , ” said Sinha . “ It help with make the environs conducive to faster fossilization , which conduct to the saving , but it ’s oxygenation that ’s raise preservation . ”
The squad thinks that the fossils were not preserved in anoxic conditions in the bottom water of the sediment , but rather that phosphatization happen at the bound of the anoxic and aerate condition within the deposit itself , and that oxygen was crucial for the preservation of these fossils in the Posidonia Shale . They also believe that these conditions are responsible for bringing out the fossils ' golden effulgence .
The study is release inEarth Science Reviews .
