Category Archives: Geochemistry

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

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

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

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

Oxygenating the Oceans in the Early Cambrian – #365papers – 2018 – 8

Zhang, Chang, Khan, Feng, Denelian, Clausen, Tribovillard, and Steiner, 2017, The link between metazoan diversity and paleo-oxygneation in the early Cambrian: An integrated palaeontological and geochemical record from the eastern Three Gorges Region of South China: Palaeogeography, Palaeoclimatology, Palaeoecology.

What’s it about?

The Cambrian is the period of Earth’s history in which many of the modern groups of multicelluar organisms appeared in the fossil record for the first time. Some have argues that this also when these groups first appeared (the so-called “Cambrian Explosion”), but that’s not necessarily the case and is a good topic for another blog post. Rocks in South China provide a good record of this period of time and the authors show that the amount of oxygen in the ocean (and therefore in the atmosphere) fluctuated frequently during this important period of time.Continue reading “Oxygenating the Oceans in the Early Cambrian – #365papers – 2018 – 8”

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″

How Aluminum in Zircon Can Tell Us What Happened Billions of Years Ago – #365papers – 2017 – 150

#365papers for May 30, 2017

Trail, Tailby, Wang, Harrison, and Boehnke, 2017, Aluminum in zircon as evidence for peraluminous and metaluminous melts from the Hadean to present: Geochemistry, Geophysics, Geosystems, v. 18, p. 1580-1593.

What’s it about?

Zircon is a mineral that forms in igneous rocks. As the rocks erode away, the zircons often survive and can be mixed into younger rocks, including new igneous rocks. Here, the authors use the concentration of aluminum in the zircons to determine the type of igneous rock the zircon originally formed in.Continue reading “How Aluminum in Zircon Can Tell Us What Happened Billions of Years Ago – #365papers – 2017 – 150”

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”

Volcanoes and the Late Ordovician Extinction – #365papers – 2017 – 139

#365papers for May 19, 2017

Jones, Martini, Fike, and Kaiho, 2017, A volcanic trigger for the Late Ordovician mass extinction? Mercury data from south China and Laurentia: Geology,

What’s it about?

One of the “Big Five” mass extinctions that has affected life on this planet is the Late Ordovician mass extinction or LOME. The causes of such extinctions are topics of focused research efforts. Here, the authors show that pulses of volcanic activity may be related to the extinction events.Continue reading “Volcanoes and the Late Ordovician Extinction – #365papers – 2017 – 139”