Fool's Gold & Fossils

Pyrite (Fool's Gold)

I am not a good advocate to stand in defense of the acknowledged gaps in the fossil record. Furthermore, I've never really felt the need to argue on one side of the debate or the other. I'll argue facts, yes - theories and faith, never. 

I only know this about myself because I have faced the argument many times from those who use said gaps as the basis to contest the validity of any evolutionary claims the fossil record may represent. 

Since there is simply no denying that these things we call fossils exist, my curiosity stems less from the need to reach a definitive conclusion on the origin of species, than from the sense that we have a responsibility to investigate their existence and derive as much information as is scientifically possible. 

How else have we any hope of ever coming close to determining if the exceptions inhabiting the physical world around us prove or invalidate our preconceptions?

FOOL’S GOLD

Native Gold Nuggets

Unlike elemental gold (Au), Fool’s Gold is an iron sulfide (FeS2) called pyrite.[1][2]

Pyrite, from the Greek 'pyro' for fire as it was observed that pyrite would send off sparks when hit with another mineral or metal.[1][2]

Mistaken for gold on account of its color, pyrite is distinguishable from elemental gold by its hardness, sulfurous odour, brittleness and multifaceted crystal form.[1][2]

Pyrite has been used as a source of sulfuric acid,[3] as a cathode in lithium batteries,[4] and as a preservative of sorts for some of the earth’s oldest fossilized remains.[1]

Today, I will be focusing on the latter; that is, the role pyrite plays in preserving the historical record of soft-bodied organisms.

FOSSILS

Fossils range in age from the youngest at the start of the Holocene Epoch to the oldest from the Archaean Eon, up to 3.48 billion years old.[5][6][7][8]

Organisms are only rarely preserved as fossils in the best of circumstances, and only a fraction of such fossils have been discovered.[5] 

This is illustrated by the fact that the number of species known through the fossil record is less than 5% of the number of known living species, suggesting that the number of species known through fossils must be far less than 1% of all the species that have ever lived.[5][9][16] 

Because of the specialized and rare circumstances required for a biological structure to fossilize, only a small percentage of life-forms can be expected to be represented in discoveries, and each discovery represents only a snapshot of the process of evolution.[5] 

The transition itself can only be illustrated and corroborated by transitional fossils, which will never demonstrate an exact half-way point.[5][10][16]

Furthermore, the fossil record is heavily slanted toward organisms with hard parts, leaving most groups of soft-bodied organisms with little to no known role.[5][9][11]

FOOL’S GOLD & THE FOSSIL RECORD OF SOFT BODIED ORGANISMS

WORKING out of the Goajiashan fossil site in China, a team of researchers from University of Missouri and Virginia Tech examined the fossil evidence of tube-shaped soft-bodied animals known as Conotubus hemiannulatus that lived over 540 million years ago.[12][13][14][15]

"The vast majority of the fossil record is composed of bones and shells," said James Schiffbauer, assistant professor of geological sciences in the College of Arts and Science at the University of Missouri. "Fossils of soft-bodied animals like worms and jellyfish, however, provide our only views into the early evolution of animal life. Most hypotheses as to the preservation of these soft tissues focus on passive processes, where normal decay is halted or impeded in some way, such as by sealing off the sediments where the animal is buried. Our team is instead detailing a scenario where the actual decay helped 'feed' the process turning the organisms into fossils -- in this case, the decay of the organisms played an active role in creating fossils."[12][13][14][15]

The first part of the C. hemiannulatus story is one typical of fossils: a sudden event rapidly triggered a mass of sediment to bury the organisms (in this case at the seafloor).[13] 

This sudden burial prevented the rapid decomposition of the organisms by aerobic bacteria.[13]

This allowed sulfate reducing bacteria, present below the surface to begin decomposing the organisms.[2][13]

Desulfovibrio vulgaris 

Sulfate-reducing bacteria "breathe" sulfate rather than
oxygen in a form of anaerobic respiration.[17]

These bacteria obtain energy by oxidizing organic compounds or molecular hydrogen (H2) while reducing sulfate to hydrogen sulfide.[17][18]

The hydrogen sulfide could then react with free iron to form pyrite.[2][13]

"In this case, the bacteria that helped break down these organisms also are responsible for preserving them as fossils. As the decay occurred, pyrite began replacing and filling in space within the animal's exoskeleton, preserving them,” said Schiffbauer.[12][13][14][15]

This helps to explain why about 80% of the fossils in the Gaojiashan formation are preserved in 3-D, with pyrite around them, while others are preserved in 2-D via the process of carbonaceous compression.[13] 

When the conditions were such that sediments did not continue to bury the fossils too quickly the pyrite process could continue.[13] 

Under conditions where the fossils buried faster, carbonaceous compression created the 2-D fossils.[13]

“Ultimately, these new findings will help scientists to gain a better grasp of why these fossils are preserved, and what features represent the fossilization process versus original biology, so we can better reconstruct the evolutionary tree of life," added Schiffbauer.[12][13][14][15]

 

Pyrite as a replacement mineral in an ammonite
from France.[1]

Pyrite dollars or pyrite suns have an appearance 

similar to sand dollars, but they are pseudofossils 

("false forms") and lack the pentagonal symmetry 

of true sand dollars.[1]

***

Fin

**Original Source for Journal Reference:

James D. Schiffbauer, Shuhai Xiao, Yaoping Cai, Adam F. Wallace, Hong Hua, Jerry Hunter, Huifang Xu, Yongbo Peng, Alan J. Kaufman. A unifying model for Neoproterozoic–Palaeozoic exceptional fossil preservation through pyritization and carbonaceous compression. Nature Communications, 2014; 5: 5754 DOI: 10.1038/ncomms6754

REFERENCES:

[1] http://en.wikipedia.org/wiki/Pyrite
[2] http://www.discoveringfossils.co.uk/pyrite_formation_fossils.htm
[3] "Industrial England in the Middle of the Eighteenth Century". Nature 83 (2113): 264–268. 1910-04-28. Bibcode:1910Natur..83..264.. doi:10.1038/083264a0.
[4] Energizer Corporation, Lithium Iron Disulfide
[5] http://en.wikipedia.org/wiki/Fossil
[6] Borenstein, Seth (13 November 2013). "Oldest fossil found: Meet your microbial mom". Associated Press.
[7] Noffke, Nora; Christian, Christian; Wacey, David; Hazen, Robert M. (8 November 2013)."Microbially Induced Sedimentary Structures Recording an Ancient Ecosystem in the ca. 3.48 Billion-Year-Old Dresser Formation, Pilbara, Western Australia". Astrobiology (journal) 13 (12): 1103–24. Bibcode:2013AsBio..13.1103N.doi:10.1089/ast.2013.1030. PMC 3870916. PMID 24205812.
[8] Brian Vastag (21 August 2011). "Oldest 'microfossils' raise hopes for life on Mars". The Washington Post.
Wade, Nicholas (21 August 2011). "Geological Team Lays Claim to Oldest Known Fossils". The New York Times.
[9] Prothero 2007, pp. 50–53
[10] Isaak, M (2006-11-05). "Claim CC200: There are no transitional fossils.". TalkOrigins Archive.
[11] Donovan, S. K. and Paul, C. R. C. (eds) 1998: The adequacy of the fossil record, Wiley, New York, 312 pp.
[12] http://www.sciencedaily.com/releases/2014/12/141218120844.htm

University of Missouri-Columbia. "550-million-year-old fossils provide new clues about fossil formation." ScienceDaily. ScienceDaily, 18 December 2014. <www.sciencedaily.com/releases/2014/12/141218120844.htm>.

[13] http://www.livescience.com/49192-fools-gold-preserves-fossils.html
[14] http://www.futurity.org/fools-gold-fossils-822792/
[15] http://www.heritagedaily.com/2014/12/550-million-year-old-fossils-provide-new-clues-fossil-formation/106123
[16] http://en.wikipedia.org/wiki/list_of_human_evolution_fossils
[17] http://en.wikipedia.org/wiki/Sulfate-reducing_bacteria[18] Ernst-Detlef Schulze, Harold A. Mooney (1993), Biodiversity and ecosystem function, Springer-Verlag, pp. 88–90

IMAGE CREDITS:

"Pyrite elbe" by Didier Descouens - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Pyrite_elbe.jpg#mediaviewer/File:Pyrite_elbe.jpg

"Native gold nuggets". Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Native_gold_nuggets.jpg#mediaviewer/File:Native_gold_nuggets.jpg

"Bullypyrite" by Didier Descouens - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Bullypyrite.jpg#mediaviewer/File:Bullypyrite.jpg

"Pyrite - disc" by cobalt123 - http://www.flickr.com/photos/cobalt/91712254/in/set-172548/. Licensed under CC BY-SA 2.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Pyrite_-_disc.jpg#mediaviewer/File:Pyrite_-_disc.jpg

"Dvulgaris micrograph". Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Dvulgaris_micrograph.JPG#mediaviewer/File:Dvulgaris_micrograph.JPG