Crockford
Peter W.
Crockford
Peter W.
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ArticleA productivity collapse to end earth's great oxidation(National Academy of Sciences, 2019-08-27) Hodgskiss, Malcolm S. W. ; Crockford, Peter W. ; Peng, Yongbo ; Wing, Boswell A. ; Horner, Tristan J.It has been hypothesized that the overall size of—or efficiency of carbon export from—the biosphere decreased at the end of the Great Oxidation Event (GOE) (ca. 2,400 to 2,050 Ma). However, the timing, tempo, and trigger for this decrease remain poorly constrained. Here we test this hypothesis by studying the isotope geochemistry of sulfate minerals from the Belcher Group, in subarctic Canada. Using insights from sulfur and barium isotope measurements, combined with radiometric ages from bracketing strata, we infer that the sulfate minerals studied here record ambient sulfate in the immediate aftermath of the GOE (ca. 2,018 Ma). These sulfate minerals captured negative triple-oxygen isotope anomalies as low as ∼ −0.8‰. Such negative values occurring shortly after the GOE require a rapid reduction in primary productivity of >80%, although even larger reductions are plausible. Given that these data imply a collapse in primary productivity rather than export efficiency, the trigger for this shift in the Earth system must reflect a change in the availability of nutrients, such as phosphorus. Cumulatively, these data highlight that Earth’s GOE is a tale of feast and famine: A geologically unprecedented reduction in the size of the biosphere occurred across the end-GOE transition.
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ArticleQuestioning the paradigm of a phosphate-limited Archean Biosphere(American Geophysical Union, 2022-08-26) Crockford, Peter ; Halevy, ItayThe nature of Archean life remains one of the most contested topics in the study of Earth history. The debate may be formulated as follows: When did present day metabolisms emerge to ecological significance? What limited the productivity of early biospheres? How did the existence and productivity of individual metabolisms affect the chemistry and oxidation state of the ocean‐atmosphere? In a new study, Ingalls et al. (2022, https://doi.org/10.1029/2022GL098100) apply a novel proxy, carbonate‐associated phosphate (CAP), to Neoarchean carbonate rocks and argue that seawater in the Neoarchean was more phosphate‐rich than through Phanerozoic time. Although the interpretation of CAP signals is currently burdened by uncertainties regarding Archean seawater chemistry, their results suggest Archean phosphate levels were comparable to modern seawater, if not higher. If true, then Earth's most successful metabolism, oxygenic photosynthesis, had either not achieved ecological prominence to exploit the relatively phosphate‐rich waters, or was curtailed by other under‐appreciated mechanisms.Plain Language SummaryOver geologic timescales, the nutrient phosphate is thought to set the overall limit on the size and productivity of Earth's biosphere. Whether this limitation was more severe in early Earth history has been the subject of intense debate. In a new study, Ingalls et al. (2022) argue that Neoarchean seawater was richer in phosphate than present‐day seawater. If correct, this discovery has important implications for the early history of life on Earth.Key PointsCarbonate‐associated phosphate measurements suggest that phosphate limitation of the Neoarchean biosphere was not more severe than todayIf oxygenic photosynthesis existed well before the Great Oxidation Event, the productivity of this metabolism was limited by other factorsCarbonate‐associated phosphate, alongside other carbonate‐based proxies, can inform seawater chemistry and the carbon cycle through time
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ArticleThe Sedimentary Geochemistry and Paleoenvironments Project(Wiley, 2021-07-05) Farrell, Úna C. ; Samawi, Rifaat ; Anjanappa, Savitha ; Klykov, Roman ; Adeboye, Oyeleye O. ; Agic, Heda ; Ahm, Anne-Sofie C. ; Boag, Thomas H. ; Bowyer, Fred ; Brocks, Jochen J. ; Brunoir, Tessa N. ; Canfield, Donald E. ; Chen, Xiaoyan ; Cheng, Meng ; Clarkson, Matthew O. ; Cole, Devon B. ; Cordie, David R. ; Crockford, Peter W. ; Cui, Huan ; Dahl, Tais W. ; Mouro, Lucas D. ; Dewing, Keith ; Dornbos, Stephen Q. ; Drabon, Nadja ; Dumoulin, Julie A. ; Emmings, Joseph F. ; Endriga, Cecilia R. ; Fraser, Tiffani A. ; Gaines, Robert R. ; Gaschnig, Richard M. ; Gibson, Timothy M. ; Gilleaudeau, Geoffrey J. ; Gill, Benjamin C. ; Goldberg, Karin ; Guilbaud, Romain ; Halverson, Galen P. ; Hammarlund, Emma U. ; Hantsoo, Kalev G. ; Henderson, Miles A. ; Hodgskiss, Malcolm S. W. ; Horner, Tristan J. ; Husson, Jon M. ; Johnson, Benjamin ; Kabanov, Pavel ; Keller, C. Brenhin ; Kimmig, Julien ; Kipp, Michael A. ; Knoll, Andrew H. ; Kreitsmann, Timmu ; Kunzmann, Marcus ; Kurzweil, Florian ; LeRoy, Matthew A. ; Li, Chao ; Lipp, Alex G. ; Loydell, David K. ; Lu, Xinze ; Macdonald, Francis A. ; Magnall, Joseph M. ; Mänd, Kaarel ; Mehra, Akshay ; Melchin, Michael J. ; Miller, Austin J. ; Mills, N. Tanner ; Mwinde, Chiza N. ; O'Connell, Brennan ; Och, Lawrence M. ; Ossa Ossa, Frantz ; Pagès, Anais ; Paiste, Kärt ; Partin, Camille A. ; Peters, Shanan E. ; Petrov, Peter ; Playter, Tiffany L. ; Plaza-Torres, Stephanie ; Porter, Susannah M. ; Poulton, Simon W. ; Pruss, Sara ; Richoz, Sylvain ; Ritzer, Samantha R. ; Rooney, Alan D. ; Sahoo, Swapan K. ; Schoepfer, Shane D. ; Sclafani, Judith A. ; Shen, Yanan ; Shorttle, Oliver ; Slotznick, Sarah P. ; Smith, Emily F. ; Spinks, Sam ; Stockey, Richard G. ; Strauss, Justin V. ; Stüeken, Eva E. ; Tecklenburg, Sabrina ; Thomson, Danielle ; Tosca, Nicholas J. ; Uhlein, Gabriel J. ; Vizcaíno, Maoli N. ; Wang, Huajian ; White, Tristan ; Wilby, Philip R. ; Woltz, Christina R. ; Wood, Rachel A. ; Xiang, Lei ; Yurchenko, Inessa A. ; Zhang, Tianran ; Planavsky, Noah J. ; Lau, Kimberly V. ; Johnston, David T. ; Sperling, Erik A.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 spreadsheets for data storage and analysis, suitable for several thousand samples, but not practical or scalable for larger, more complex datasets. As results have accumulated, researchers have increasingly gravitated toward larger compilations and statistical tools. New data frameworks have become necessary to handle larger sample sets and encourage more sophisticated or even standardized statistical analyses. In this paper, we describe the Sedimentary Geochemistry and Paleoenvironments Project (SGP; Figure 1), which is an open, community-oriented, database-driven research consortium. The goals of SGP are to (1) create a relational database tailored to the needs of the deep-time (millions to billions of years) sedimentary geochemical research community, including assembling and curating published and associated unpublished data; (2) create a website where data can be retrieved in a flexible way; and (3) build a collaborative consortium where researchers are incentivized to contribute data by giving them priority access and the opportunity to work on exciting questions in group papers. Finally, and more idealistically, the goal was to establish a culture of modern data management and data analysis in sedimentary geochemistry. Relative to many other fields, the main emphasis in our field has been on instrument measurement of sedimentary geochemical data rather than data analysis (compared with fields like ecology, for instance, where the post-experiment ANOVA (analysis of variance) is customary). Thus, the longer-term goal was to build a collaborative environment where geobiologists and geologists can work and learn together to assess changes in geochemical signatures through Earth history.
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ArticlePublisher Correction : Pelagic barite precipitation at micromolar ambient sulfate(Nature Publishing Group, 2018-01-18) Horner, Tristan J. ; Pryer, Helena V. ; Nielsen, Sune G. ; Crockford, Peter W. ; Gauglitz, Julia M. ; Wing, Boswell A. ; Ricketts, Richard D.Correction to: Nature Communications https://doi.org/10.1038/s41467-017-01229-5, Article published online 07 November 2017
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ArticlePelagic barite precipitation at micromolar ambient sulfate(Nature Publishing Group, 2017-11-07) Horner, Tristan J. ; Pryer, Helena V. ; Nielsen, Sune G. ; Crockford, Peter W. ; Gauglitz, Julia M. ; Wing, Boswell A. ; Ricketts, Richard D.Geochemical analyses of sedimentary barites (barium sulfates) in the geological record have yielded fundamental insights into the chemistry of the Archean environment and evolutionary origin of microbial metabolisms. However, the question of how barites were able to precipitate from a contemporary ocean that contained only trace amounts of sulfate remains controversial. Here we report dissolved and particulate multi-element and barium-isotopic data from Lake Superior that evidence pelagic barite precipitation at micromolar ambient sulfate. These pelagic barites likely precipitate within particle-associated microenvironments supplied with additional barium and sulfate ions derived from heterotrophic remineralization of organic matter. If active during the Archean, pelagic precipitation and subsequent sedimentation may account for the genesis of enigmatic barite deposits. Indeed, barium-isotopic analyses of barites from the Paleoarchean Dresser Formation are consistent with a pelagic mechanism of precipitation, which altogether offers a new paradigm for interpreting the temporal occurrence of barites in the geological record.
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ArticleOrganic matter sulfurization and organic carbon burial in the Mesoproterozoic(Elsevier, 2023-03-08) Raven, Morgan Reed ; Crockford, Peter W. ; Hodgskiss, Malcolm S.W. ; Lyons, Timothy W. ; Tino, Christopher J. ; Webb, Samuel M.Throughout the Proterozoic Era, sedimentary organic carbon burial helped set the pace of global oxygenation and acted as a major modulator of atmospheric CO2 and climate. Although Proterozoic rocks generally contain low concentrations of organic matter (OM), there are key exceptions to this rule, including the relatively OM-rich Arctic Bay shales from Baffin Island, Canada (Bylot Supergroup, Borden Basin, ∼1.05 Ga). The mechanisms driving elevated OM concentrations in these and other Proterozoic shales remain poorly understood. In the Mesozoic and Cenozoic, organic matter sulfurization can be a major driver of enhanced OM burial across a range of redox conditions comparable to those inferred for many Proterozoic environments. Therefore, in this study, we evaluate the role of sulfurization in driving OM preservation in the Mesoproterozoic Borden Basin and discuss its relevance to Proterozoic systems in general. We present the first evidence for syngenetic-to-early-diagenetic OM sulfurization in a Proterozoic basin, which begins to fill a several-billion-year gap in our record of organic S across Earth history. We find that OM sulfurization was particularly extensive in shales from a relatively shallow-water section (Alpha River) but less extensive in shales deposited in deeper water (Shale Valley), which is consistent with models that infer sulfidic ‘wedges’ or O2-minimum-zone-type structures on shelf margins at least intermittently at this time. At the shallower site, organic S and pyrite are similarly 34S-depleted and thus likely formed at roughly the same time near the sediment–water interface under conditions previously interpreted to have been ferruginous to intermittently sulfidic. In contrast, at the deeper-water site, large S-isotope differences between pyrite and organic S along with low apparent OM sulfurization intensities indicate that pyrite formation was favored over OM sulfurization during early sedimentation under variable but primarily ferruginous conditions. Although Mesoproterozoic biomass can be substantially sulfurized, indicators of sulfurization intensity are not correlated with OM concentrations, and therefore sulfurization does not appear to have been the primary driver of enhanced OM concentrations in Arctic Bay Formation shales. The link between sulfurization and total OM preservation may have been modulated during the deposition of Arctic Bay Formation shales by differences in iron availability, nutrient cycling, and particle dynamics in the Mesoproterozoic.
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ArticleDeconstructing the Lomagundi-Jatuli Carbon Isotope Excursion(Annual Reviews, 2023-05-31) Hodgskiss, Malcolm S. W. ; Crockford, Peter W. ; Turchyn, Alexandra V.The early to mid-Paleoproterozoic Lomagundi-Jatuli Excursion (LJE) is ostensibly the largest magnitude (approximately +5 to +30‰), longest duration (ca. 130-250 million years) positive carbon isotope excursion measured in carbonate rocks in Earth history. The LJE has been attributed to large nutrient fluxes, an increase in the size of the biosphere, a reorganization of the global carbon cycle, and oxygenation of the atmosphere. However, significant debate remains about its genesis, synchroneity, global-versus-local extent, and role in atmospheric oxygenation. Here we review existing models and mechanisms suggested for the LJE and analyze a compilation of ∼9,400 δ13 Ccarb and associated contextual data. These data call into question the interpretation of the LJE as a globally synchronous carbon isotope excursion and suggest that any model for the LJE must account for both the absence of a clearly defined initiation and termination of the excursion and a facies-dependent expression of 13C-enrichment.The Lomagundi-Jatuli Excursion (LJE) continues to challenge current understandings of the carbon cycle.Understanding this excursion is critical for reconstructing biogeochemical cycles and atmospheric oxygenation through Earth history.Some evidence indicates local rather than global changes in δ13CDIC and raises the possibility of asynchronous, local excursions.Resolving whether the LJE was globally synchronous or asynchronous is essential for discriminating between different models.