Isotopes and Interpretations: Are We Getting it Right? – #365papers – 2018 – 15

Kohn and McKay, 2012, Paleoecology of late Pleistocene-Holocene faunas of eastern and central Wyoming, USA, with implications for LGM climate models: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 326-328, 42-53.

What’s it about?

Here, the authors compare values of carbon and oxygen isotopes from multiple species (herbivores and carnivores) from a single site to understand how these isotopes reflect environmental variables like annual precipitation and temperature, and how all the animals interacted with each other and the environment. Understandings gathered from the isotopic results were compared to what is known from modern, living animals and to the results from climate models. Continue reading

Geochemistry Shows Oldest “Fossils” Really Are Fossils – #365papers – 2018 – 6

Schopf, Kitajima, Spicuzza, Kudryavtsev, Valley, 2018, SIMS analyses of the oldest known assemblage of microfossils document their taxon-correlated carbon isotope compositions: Proceedings of the National Academy of Sciences, v. 115, p. 53-58.

What’s it about?

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

Calcium Can Tell Us About Ancient Ecosystem Structure – #365papers – 2017 – 147

#365papers for May 27, 2017

Martin, Vincent, Tacail, Khaldoune, Jourani, Bardet, Balter, 2017, Calcium isotopic evidence for vulnerable marine ecosystem structure prior to the K/Pg extinction: Current Biology, v. 27

What’s it about?

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

Because Isotopes of Carbon and Oxygen Are So Last Century… – #365papers – 2017 – 141

#365papers for May 21, 2017

Martin, Tacail, and Balter, 2017, Non-traditional isotope perspective in vertebrate palaeobiology: Palaeontology, p. 1-18.

What’s it about?

The authors discuss the utility of isotopes of calcium, magnesium, copper, iron, and zinc for study of ancient environments, dietary preferences, and food chains. Continue reading

Highs and Lows of the Rocky Mountains in the Middle to Late Eocene – #365papers – 2017 – 97

#365papers for April 7, 2017

Fan, Constensius, and Dettman, 2017, Prolonged high relief in the northern Cordilleran orogenic front during middle and late Eocene extension based on stable isotope paleoaltimetry: Earth and Plantery Science Letters, v. 457, p. 376-384.

What’s it about?

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

Tall Teeth and Grazing Diets – #365papers – 2017 – 94

#365papers for April 4, 2017

Feranec and Pagnac, 2017, Hypsodonty, horses, and the spread of C4 grasses during the middle Miocene in southern California: Evolutionary Ecology Research, v. 18, p. 201-223.

What’s it about?

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.

The authors use isotopes from early horses that are hypsodont to show that tall teeth are related to doing more grazing. Continue reading

Putting All the Data Together Makes a More Complete History – #365papers – 2017 – 77

#365papers for March 18, 2017

Feakins, Levin, Liddy, Sieracki, Eglinton, and Bonnefille, 2017, Northeast African vegetation change over 12 m.y.: Geology, v. 41, p. 295-298.

What’s it about?

The authors combine pollen and isotopic data from fossil leaf waxes from an ocean core with soil carbonate data from northeast Africa to better understand the origin and composition of grasslands in northeast Africa over the last 12 million years. Continue reading

Global Warming; Shrinking Mammals – #365papers – 2017 – 76

#365papers for March 17, 2017

D’Ambrosia, Clyde, Fricke, Gringerich, Abels, 2017, Repetitive mammalian dwarfing during ancient greenhouse warming events: Science Advances, v. 3, e1601430.

What’s it about?

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.

Dwarfing of mammalian species has been documented at the PETM. This paper shows dwarfing of mammals also occurred at the ETM2. Continue reading

How Soil Carbonate Can Tell Us About Climate – #365papers – 2017 – 75

#365papers for March 16, 2017

Cerling, T.E., 1984, The stable isotopic composition of modern soil carbonate and its relationship to climate: Earth and Planetary Science Letters, v. 71, p. 229-240.

What’s it about?

This paper discusses in detail how isotopes of carbon and oxygen in carbonate minerals that form in soils are related to that of plant biomass (carbon) or local precipitation (oxygen). Continue reading

Lakes Come and Go, 50 Million Years Ago – #365papers – 2017 – 69

#365papers for March 10, 2017

Davis, Wiegand, Carroll, and Chamberlain, 2008, The effect of dreainage reorganization on paleoaltimetry studies: An example from the Paleogene Laramide foreland: Earth and Planetary Science Letters, v. 275, p. 258-268.

What’s it about?

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