Clay Keeps Records of Ancient Water – #365papers – 2018 – 56

Mix and Chamberlain, 2014, Stable isotope records of hydrologic change and paleotemperature from smectite in Cenozoic western North America: Geochimica et Cosmochimica Acta, v. 141, p. 532-546

What’s it about?

Smectite is a specific kind of clay mineral, common in volcanic ash. This kind of clay incorporates water during its formation, which, as the authors show, can provide a record of what surface water was like when the clay formed. Continue reading

Migrating Marsupials of the Pleistocene – #365papers – 2018 – 44

Price, Ferguson, Webb, Feng, Higgins, Nguyen, Zhao, Joannes-Boyau, and Louys, 2017, Seasonal migration of marsupial megafauna in Pleistocene Sahul (Australia-New Guinea): Proceedings of the Royal Society B, v. 284: 20170785

What’s it about?

Seasonal migrations are seen in many large mammals. In modern animals, however, such migrations are not observed in marsupials. The authors put together geochemical data from rocks and fossil to show that the massive wombat-like extinct marsupial Diprotodon migrated seasonally as far as 100 km each way. Continue reading

Using Glass to Estimate Altitude – #365papers – 2018 – 37

Dettinger and Quade, 2015, Testing the analytical protocols and calibration of volcanic glass for the reconstruction of hydrogen isotopes in paleoprecipitation, in DeCelles, Ducea, Carrapa, and Kapp, eds., Geodynamics of a Cordilleran Orogenic System: The Central Andes of Argentina and Northern Chile: Geological Society of America Memoir 212, p. 261-276.

What’s it about?

Isotopes of oxygen and hydrogen from water can give us insights into the altitude at which that water fell to the ground as rain. Some of this water can become incorporated into volcanic glass (in ash), preserving the isotopic values of the original water. Continue reading

Interpreting Cretaceous Environments from Multiple Sources – #365papers – 2018 – 32

Bojar, Csiki, and Grigorescu, 2010, Stable isotope dirstibution in Maastrichtian vertebrates and paleosols from the Hateg Basin, South Carpathians: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 293, p. 329-342.

What’s it about?

Some late Cretaceous-aged (AKA Maastrichtian) rocks from Romania contain fossilized soils (paleosols), dinosaur bones and teeth, and dinosaur eggshells. The authors use geochemical analysis, specifically stable isotope analysis, from all of these materials to build a fairly complete picture of what the region was like at the time that those dinosaurs were alive. What they found was that the environment was relatively warm and dry, and that the dinosaurs didn’t appear to utilize different parts of the habitat, but instead lived side-by-side. Continue reading

How Can We Know When The Earth’s Atmosphere Became Oxygenated? – #365papers – 2018 – 31

Eickmann, Hofmann, Wille, Bui, Wing, and Schoenberg, 2018, Isotopic evidence for oxygenated Mesoarchaean shallow oceans: Nature Geoscience, v. 11, p. 133–138.

What’s it about?

Sulfur and iron atoms come in different sizes, called isotopes. The relative amounts of these isotopes can tell us a lot. In this paper, isotopes of sulfur are used to recognize active metabolism of microbes that use sulfur in their metabolic processes. These results, combined with results from isotopes of iron, provide evidence not only of the activities of life, but also show that there was some oxygen in the atmosphere at that time, enough to oxygenate shallow water but not deep water of the ocean. Continue reading

Sabertooth, Sabertooth, How Do Your Teeth Grow? – #365papers – 2018 – 30

Feranec, 2004, Isotopic evidence of saber-tooth development, growth rate, and diet from the adult canine of Smilodon fatalis from Rancho La Brea: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 206, p. 303-310.

What’s it about?

Sabertoothed mammals are so named because of their massive, elongate canines. A natural question to ask is, how does it get so long? The major ideas are that the teeth grow for a very long time (which would affect how the animals survived before the teeth were fully grown), that they grew very quickly, or some combination.

The author uses isotopes of oxygen from the tooth enamel of some adult sabertooth tigers (Smilodon fatalis) to estimate how long it tooth the tooth to grow. This he compares with known growth rates and timing of development of modern lions and tigers to see how it compares. Continue reading

What X-Rays and Absorptions Really Tell Us About Fossilization – #365papers – 2018 – 24

Stathopoulou, Psycharis, Chryssikos, Gionis, and Theodorou, 2008, Bone diagnesis: New data from infrared spectroscopy and X-ray diffraction: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 266, p. 168-174.

What’s it about?

The authors here use two different methods to gain a sense of the changes in the shapes and sizes of crystals of the bone mineral bioapatite due to the process of fossilization. They also consider the various differences in composition (i.e. how much fluorine, hydroxyl, or carbonate) is present in the bioapatite. While this is done nominally to look at the effects of fossilization, it appears to be better at fingerprinting different localities. Continue reading

Why Can’t We Just Measure Alteration of Bone Due To Fossilization? – #365papers – 2018 – 23

Trueman, Privat, and Field, 2008, Why do crystallinity values fail to predict the extent of diagenetic alteration of bone mineral? Palaeogeography, Palaeoclimatology, Palaeoecology, v. 266, p. 160-167.

What’s it about?

Bones are composed of little crystals of the mineral referred to as bioapatite with organic materials (collagen, blood vessels, and cells that regulate the growth of bioapatite, etc) spread throughout. When an animal dies, the organic materials decay and the bioapatite crystals change their shape and size. There are methods by which we can readily measure the shape and size of the crystals, which, presumably, would tell us just how altered the bones are due to the fossilization process. This would then let us know how accurate any geochemical analyses we do with the bone are.

Only that the shape and size of bone crystals doesn’t actually work as a good measure of the alteration due to fossilization. Continue reading

Carbon from Bone Mineral and Bone Collagen Tells Us Who’s Eating Whom – #365papers – 2018 – 20

Clementz, Fox-Dobbs, Wheatly, Koch, and Doak, 2009, Revisiting old bones: coupled carbon isotope analysis of bioapatite and collagen as an ecological and palaeoecological tool: Geological Journal, v. 44, p. 605-620.

What’s it about?

“Trophic level” is a term scientists use to describe where an organism lies in the food chain (or food web). Animals of high trophic level are the carnivores, and organisms low in tropic level are the primary producers, like algae, or other plants. In the middle are the herbivores (primary consumers) that eat the primary producers. This paper is a discussion of another means by which one can interpret trophic level of animals, particularly those for which we only have fossil evidence. Continue reading

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