Jack Geary Murphy

Jack Geary Murphy
University of Pennsylvania | UP · Department of Earth and Environmental Science

PhD

About

12
Publications
3,278
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109
Citations
Citations since 2017
12 Research Items
109 Citations
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20172018201920202021202220230102030405060
20172018201920202021202220230102030405060
Introduction
I employ field observations, analytical chemistry, and numerical models to investigate the long term evolution of Earth's global biogeochemical cycles.

Publications

Publications (12)
Article
Records of the lithium isotopic composition of seawater (δ7Lisw), preserved in the lithium isotopic composition of shallow-marine carbonate sediments (δ7Licarb), provide information about the links between silicate weathering and clay formation, the global carbon cycle, and Earth’s climate on geologic timescales. However, the record of δ7Lisw value...
Article
Full-text available
The evolution of the global carbon and silicon cycles is thought to have contributed to the long-term stability of Earth’s climate1–3. Many questions remain, however, regarding the feedback mechanisms at play, and there are limited quantitative constraints on the sources and sinks of these elements in Earth’s surface environments4–12. Here we argue...
Article
Full-text available
Molecular phylogenetic data suggest that photosynthetic eukaryotes first evolved in freshwater environments in the early Proterozoic and diversified into marine environments by the Tonian Period, but early algal evolution is poorly reflected in the fossil record. Here, we report newly discovered, millimeter- to centimeter-scale macrofossils from ou...
Article
Full-text available
Significance Until now, all of the ca. 1,800 known modern scleractinian coral species were thought to produce skeletons exclusively of aragonite. Asymbiotic Paraconotrochus antarcticus living in the Southern Ocean is the first example of an extant scleractinian that forms a two-component carbonate skeleton, with an inner structure made of high-Mg c...
Article
The pairing of calcium and magnesium isotopes (δ 44/40 Ca, δ 26 Mg) has recently emerged as a useful tracer to understand the environmental information preserved in shallow-marine carbonates. Here, we applied a Ca and Mg isotopic framework, along with analyses of carbon and lithium isotopes, to late Tonian dolostones, to infer seawater chemistry ac...
Article
Low-temperature (<100 °C) alteration of oceanic crust plays an important role in determining the chemical composition of the oceans. Although a major sink of seawater potassium, little is known about the effects of low-temperature basalt alteration on the potassium isotopic composition of seawater (δ41K∼0‰), which is ∼0.50‰ enriched relative to bul...
Conference Paper
Full-text available
The Tonian (1000 to 720 Ma) represents a critical transition in Earth history between the Mesoproterozoic (1600 to 1000 Ma) and the low-latitude glaciations of the Cryogenian (720 to 635 Ma). However, the early Tonian period is notoriously poorly understood and well-preserved exposures are rare in the stratigraphic record. The Proterozoic inliers o...
Conference Paper
We present a new sequence stratigraphic and facies architectural model for the ca. 900–850 Ma Hematite Creek and Katherine groups (lower and middle Mackenzie Mountains Supergroup, respectively) in the Wernecke Mountains of east-central Yukon, Canada. This ~3-km-thick internally conformable succession provides a virtually continuous tectono-sediment...
Poster
Records of the lithium isotopic composition of seawater (ẟ7Lisw) may provide important information about the role of silicate weathering in the geological carbon cycle. While shallow-water carbonates may serve as an archive of the lithium isotopic composition of past oceans, interpreting the seawater isotopic signal in carbonate sediments is compli...

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