
Benjamin JohnsonUniversity of Colorado Boulder | CUB · Department of Geological Sciences
Benjamin Johnson
PhD
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11
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Introduction
Additional affiliations
October 2017 - February 2019
January 2017 - June 2017
September 2002 - May 2006
Publications
Publications (11)
Geobiology explores how Earth's system has changed over the course of geologic history and how living organisms on this planet are impacted by or are indeed causing these changes. For decades, geologists, paleontologists, and geochemists have generated data to investigate these topics. Foundational efforts in sedimentary geochemistry utilized sprea...
Otavi Group is a 1.5−3.5-km-thick epicontinental marine carbonate succession of
Neoproterozoic age, exposed in an 800-km-long Ediacaran−Cambrian fold belt that rims
the SW cape of Congo craton in northern Namibia. Along its southern margin, a contiguous
distally tapered foreslope carbonate wedge of the same age is called Swakop Group.
Swakop Group...
The Neoproterozoic Earth was punctuated by two low-latitude Snowball Earth glaciations. Models permit oceans with either total ice cover or substantial areas of open water. Total ice cover would make an anoxic ocean likely, and would be a formidable barrier to biologic survival. However, there are no direct data constraining either the redox state...
Recent work indicates the presence of substantial geologic nitrogen reservoirs in the mantle and continental crust. Importantly, this geologic nitrogen has exchanged between the atmosphere and the solid Earth over time. Changes in atmospheric nitrogen (i.e. atmospheric mass) have direct effects on climate and biological productivity. It is difficul...
Cryogenian synglacial deposits are regionally thin but locally thick, considering glacial duration, but the reasons for local thickening are poorly known. We studied three local thickenings of the Sturtian Chuos Formation in northern Namibia by measuring closely spaced columnar sections, not only of the synglacial deposits but also of the bounding...
Long viewed as a mostly noble, atmospheric species, recent work demonstrates that nitrogen in fact cycles throughout the Earth system, including the atmosphere, biosphere, oceans, and solid Earth. Despite this new-found behaviour, more thorough investigation of N in geologic materials is limited due to its low concentration (one to tens of parts pe...
The existence of coherent, large-scale, submarine landslides on modern continental margins implies that their apparent rarity in ancient orogenic belts is due to non-recognition. Two map-scale, coherent, pre-orogenic, normal-sense detachment structures of Ediacaran age are present in the Kaoko belt, a well-exposed arc–continent collision zone in no...
We comprehensively compile and review N content in geologic materials to
calculate a new N budget for Earth. Using analyses of rocks and minerals in
conjunction with N-Ar geochemistry demonstrates that the Bulk Silicate Earth
(BSE) contains \sim7\pm4 times present atmospheric N (4\times10^18 kg N, PAN),
with 27\pm16\times10^18 kg N. Comparison to c...
Triple oxygen isotopes of sulfate and nitrate are useful metrics for the chemistry of their formation. Existing measurement methods, however, do not account for oxygen atom exchange with quartz during the thermal decomposition of sulfate. We present evidence for oxygen atom exchange, a simple modification to prevent exchange, and a correction for p...