The best evidence for the origins of life on this planet are geochemical signatures in rocks representing the metabolism of living organisms. Here, the authors show that the geochemical (isotopic) signatures directly correlate with what have been interpreted at the body fossils of primitive life forms, mostly bacteria.Continue reading “Geochemistry Shows Oldest “Fossils” Really Are Fossils – #365papers – 2018 – 6″
The variations of the amounts of stable isotopes (that is non-radioactive) found in rocks and fossils can be used to help us understand patterns of weather, of vegetation, and of who’s eating whom in modern and fossil rocks, bones, teeth, and shells. Most of the time carbon, oxygen, and nitrogen are used for this.
The authors here show that calcium isotopes can be used to understand tropic level (where organisms are on the food chain) in modern and fossil animals. Their work shows that large marine reptiles likely went extinct at the end of the Permian Period because they all lived at the same trophic level. There was some sort of ecological change that eradicated their food supply and the marine reptiles could not recover.Continue reading “Calcium Can Tell Us About Ancient Ecosystem Structure – #365papers – 2017 – 147”
The Rocky Mountains have been around for a long, long time. This study focuses on a part of the Rockies that was still growing between about 46 to about 34 million years ago. Through the study of fossil soils and fossil snails, the authors show that the difference between the lowest basins and the highest mountain peaks was around 4 km – which is a lot!Continue reading “Highs and Lows of the Rocky Mountains in the Middle to Late Eocene – #365papers – 2017 – 97”
Modern horses have very tall (hypsodont) teeth. This is thought to be an adaptation for grazing, because chewing grass wears down teeth faster than chewing the leaves off a tree.
A fossil horse tooth from Natural Trap Cave. The grinding surface is on the left. Only about 1/5 of this tooth stuck above the gum line.
Paleontologists use the height of the tooth (its hypsodonty) to distinguish animals that grazed from those that ate bushes, shrubs, and trees (called browsing).
Isotopically, grasses look different from leaves from bushes. This chemical difference gets recorded into teeth.
Rapid global warming in Earth’s past had occurred more than once. The most commonly studied episode occurred 55 million years ago, at the boundary between the Paleocene and Eocene epochs (Paleocene Eocene Thermal Maximum, PETM). Several other episodes have happened, including the ETM2 and H2 episodes which are discussed in this paper.
The authors use isotopes of carbon, oxygen, and strontium, plus relative abundances of strontium and calcium in lake deposits to interpret water sources, connectivity of lakes, and general environmental parameters for the Uinta Basin during the Eocene (~55-~43 million years ago).Continue reading “Lakes Come and Go, 50 Million Years Ago – #365papers – 2017 – 69”