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

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

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

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

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

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

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

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

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

The Middle Eocene Climatic Optimum in the Northern Hemisphere – #365papers – 2017 – 67

#365papers for March 8, 2017

Jovane, Florindo Coccioni, Dianares-Turell, Marsili, Monechi, Roberts, Sprovieri, 2007, The middle Eocene climatic optimum event in the Contessa Highway section, Umbrian Apennines, Italy: GSA Bulletin, v. 119, p. 413-427.

What’s it about?

This paper like others I’ve read recently discusses the abundance of single-celled organisms in the ocean called foraminifera (forams). The overall abundance of different species plus isotopic analysis of the fossils themselves can provide insights about climate during the middle Eocene. Continue reading “The Middle Eocene Climatic Optimum in the Northern Hemisphere – #365papers – 2017 – 67”