No evidence of extraterrestrial noble metal and helium anomalies at Marinoan glacial termination

View/ Open
Date
2015-08Author
Peucker-Ehrenbrink, Bernhard
Concept link
Waters, Christine A.
Concept link
Kurz, Mark D.
Concept link
Hoffman, Paul F.
Concept link
Metadata
Show full item recordCitable URI
https://hdl.handle.net/1912/8527As published
https://doi.org/10.1016/j.epsl.2015.12.040Keyword
Snowball earth; Osmium isotopes; Iridium; Helium isotopes; Extraterrestrial matter; Cap carbonateAbstract
High concentrations of extraterrestrial iridium have been reported in terminal Sturtian and
Marinoan glacial marine sediments and are used to argue for long (likely 3-12 Myr) durations of
these Cryogenian glaciations. Reanalysis of the Marinoan sedimentary rocks used in the original
study, supplemented by sedimentary rocks from additional terminal Marinoan sections, however,
does not confirm the initial report. New platinum group element concentrations, and 187Os/188Os and 3He/4He signatures are consistent with crustal origin and minimal extraterrestrial
contributions. The discrepancy is likely caused by different sample masses used in the two
studies, with this study being based on much larger samples that better capture the stochastic
distribution of extraterrestrial particles in marine sediments. Strong enrichment of redox-sensitive elements, particularly rhenium, up-section in the basal postglacial cap carbonates, may
indicate a return to more fully oxygenated seawater in the aftermath of the Marinoan snowball
earth. Sections dominated by hydrogenous osmium indicate increasing submarine hydrothermal
sources and/or continental inputs that are increasingly dominated by young mantle-derived rocks
after deglaciation. Sedimentation rate estimates for the basal cap carbonates yield surprisingly
slow rates of a few centimeters per thousand years. This study highlights the importance of
using sedimentary rock samples that represent sufficiently large area-time products to properly
sample extraterrestrial particles representatively, and demonstrates the value of using multiple
tracers of extraterrestrial matter.
Description
Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 437 (2016): 76-88, doi:10.1016/j.epsl.2015.12.040.
Collections
Suggested Citation
Preprint: Peucker-Ehrenbrink, Bernhard, Waters, Christine A., Kurz, Mark D., Hoffman, Paul F., "No evidence of extraterrestrial noble metal and helium anomalies at Marinoan glacial termination", 2015-08, https://doi.org/10.1016/j.epsl.2015.12.040, https://hdl.handle.net/1912/8527Related items
Showing items related by title, author, creator and subject.
-
Helium and lead isotope geochemistry of oceanic volcanic rocks from the East Pacific and South Atlantic
Graham, David W. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1987-09)The isotopic evolution of helium and lead in the Earth is coupled by virtue of their common radioactive parents uranium and thorium. The isotopic signatures in oceanic volcanic rocks provide constraints on the temporal ... -
Diffusion of helium isotopes in silicate glasses and minerals : implications for petrogenesis and geochronology
Trull, Thomas W. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1989-04)Helium mobility in geologic materials is a fundamental constraint on the petrogenetic origins of helium isotopic variability and on the application of radiogenic and cosmogenic helium geochronology. 3He and 4He volume ... -
The deep distributions of helium isotopes, radiocarbon, and noble gases along the U.S. GEOTRACES East Pacific Zonal Transect (GP16)
Jenkins, William J.; Lott, Dempsey E.; German, Christopher R.; Cahill, Kevin L.; Goudreau, Joanne; Longworth, Brett E. (2017-03)We report the deep distributions of noble gases, helium isotopes, and radiocarbon measured during the U.S. GEOTRACES GP16 East Pacific Zonal Transect between 152 and 77°W at 12- 15°S in the South Pacific. The dominant ...