Patterson Lab Publications 2023-2025

McCarthy, et al. (submitted) High-resolution analysis of the varved succession of Crawford Lake across the proposed base of the Anthropocene.  Anthropocene Review.

Four years after the Anthropocene Working Group (AWG) voted to work toward defining the Anthropocene series/ epoch with a base in the mid-20th C, the varved sediments of Crawford Lake (Milton, Ontario, Canada) were selected as the Global boundary Stratotype Section and Point (GSSP) candidate. The initial major rise in activity of 239+240Pu had been selected as the primary chronostratigraphic marker to define the base of the Anthropocene. Unfortunately, the precise year when this occurred could not be determined from measurements of samples combining multiple varves, although activities were entirely consistent with global yields of this anthropogenic radionuclide. Individual varves sampled from freeze cores collected in April 2023 provide annual resolution for bomb radionuclides from the late 1940s through early 1950s to identify the initial major rise in plutonium activity and through the early 1960s to identify the bomb spike. Measurements of 137Cs independently identified the peak in bomb radionuclide activity and allowed the varve age model to be refined, with former assignments in the succession of Crawford Lake determined to have been one year too old.

The increase in 239+240Pu activities (calculated from concentrations measured using accelerated mass spectrometry) 0.0031 Bq/g between varves now assigned to 1951 and 1952 is consistent with the onset of thermonuclear weapons testing in 1952, so the proposed base for the Anthropocene is at 16.2 cm in core CRA23-BC-1F-1, at the contact between the light- and dark-coloured laminae deposited in 1952 CE. Lower activities in 1961 (0.0175 ± 0.0008 Bq/g compared to 1962 CE (0.0278 ± 0.0013 Bq/g) capture the shoulder associated with the moratorium from November 1958 to September 1961 CE. A decline in 137Cs activity also captures the moratorium preceding the sharp increase in fallout until ratification of the Limited Test Ban Treaty in late 1963 CE, when activities of 239+240Pu peaked at 0.0299 ± 0.0017 Bq/g. Analysis of individual varves with varying amounts of organic matter and inorganic calcite illustrates the influence of lithology on organic proxies, but the upcore trend toward depleted values of δ15N through the 20th C reflects increased fossil fuel combustion worldwide. An inflection point in δ15N around 1911 CE is attributed the global impact of the Haber-Bosch process coupled with establishment of steel mills in nearby Hamilton, Ontario, and another in the early 1950s attributed to the Great Acceleration to which the tipping point in the Earth system is attributed.

Warnock-Juteau, et al. 2024. Computed tomographic investigation of a hatchling skull reveals ontogenetic changes in the dentition and occlusal surface morphology of Hadrosauridae (Dinosauria: Ornithischia). Vertebrate Anatomy Morphology Palaeontology 11: 111-150. DOI 10.18435/vamp29395

CMN 8917 is a partial skull that represents one of the few nestling-sized juvenile hadrosaurines known to date. Support for its placement within Hadrosaurinae includes a narial vestibule not enclosed within the premaxillary dorsal and lateral processes, the presence of an anterodorsal maxillary process, and a maxillary dorsal process that is longer anteroposteriorly than dorsoventrally. The skull also possesses tooth traits traditionally associated with lambeosaurines; secondary ridges on some maxillary and dentary tooth crowns, and denticulation on some maxillary crowns. The occurrence of these features in a juvenile hadrosaurine suggests that they are modified during ontogeny, calling into question their taxonomic utility for identifying juvenile specimens. The dentary teeth of CMN 8917 are similar to those of many adult hadrosaurids in that they possess a concave occlusal surface with steeper lingual and shallower buccal wear zones. This differs from the occlusal surface morphology present in some other juvenile hadrosaurids, which suggests interspecific differences in dental battery development—possibly reflective of dietary differences—occurred during early ontogeny in some taxa.

Milani, et al. 2024.  Numerical icing simulations of heated cylinder and comparisons to flight test results. Journal of Aircraft. https://doi.org/10.2514/1.C037682

This study investigates the capabilities of ANSYS FENSAP-ICE in the context of ice protection system (IPS) development by simulating ice accretion on a heated cylinder probe mounted under the wing of the Convair-580 research aircraft. Simulations were performed using experimental data collected during a flight in natural Appendix O icing conditions and ice shapes were verified using high-resolution video of the ice accretion. No combination of simulation settings, input parameters, and multi-shot methods tested in this study generated the same macroscopic surface features observed in the experiment, however, the amount of ice accretion, general location of ice features, and formation processes were validated. These findings reveal the difficulty of simulating a short icing period (10-minutes) with a dynamic icing intensity, low LWC level, and high static air temperature. Preliminary analysis shows that users should include the vapor pressure model when simulating glaze ice and consider using more than one set of input parameters to capture the effect of changing icing intensity when simulating a highly dynamic icing environment. Simulations that include leading-edge heat flux predicted runback icing on the probe which is valuable information when developing an IPS.

Llew-Williams, et al. 2024. Quantifying conditions required for varve formation in meromictic Crawford Lake, Ontario, Canada: important process for delimiting the Anthropocene epoch. Journal of Paleolimnology 71: 101-124.

Varved sediments in meromictic Crawford Lake consist of dark-light couplets of organic matter (primarily phytoplankton and amorphous organic matter) capped by calcite crystals. The crystals precipitate in the alkaline epilimnion between spring and fall turnover, consistent with Langelier Saturation Index calculations that predict calcite precipitation when pH and temperature exceed 7.76 and ~15°C, respectively. Climate, primary production, and the pH of the epilimnion control lamina thickness: acid rain primarily affects the precipitation and accumulation of calcite crystals, whereas both endogenic calcite and authigenic organic matter are affected by climate and primary production. Thin varves, often with barely perceptible light-coloured calcite laminae were deposited between the late 1940s and mid-1970s, when the pH of the epilimnion fell slightly in response to deterioration in air and water quality associated with rapid industrialization. Conditions required for precipitation of calcite laminae were absent during the 16^th to mid-19^th centuries, an interval corresponding to the Little Ice Age when no human impact affected the catchment. Varves dating from 1867 CE onwards (the Canadian Zone) facilitate the candidacy of the deep basin sediments of Crawford Lake to define the Anthropocene epoch.

González-Miguéns, et al. 2023. A needle in a haystack: a new metabarcoding approach to survey diversity at the species level of Arcellinida (Amoebozoa: Tubulinea).  Molecular Ecology Resources. DOI: 10.1111/1755-0998.13771

Environmental DNA-based diversity studies have increased in popularity with the development of high throughput sequencing technologies. This permits the potential simultaneous retrieval of vast amounts of molecular data from many different organisms and species, thus contributing to a wide range of biological disciplines. Environmental DNA protocols designed for protists often focused on the highly conserved  small subunit of the ribosome gene that does not permit species-level assignments. Consequently, the biological information associated species is lost, and the classification of the molecular diversity into Operational Taxonomic Units cannot be compared directly between studies. To solve this issue, specific eDNA protocols based on fast evolving genes applicable to the species level have been proposed. However this approach is not yet applied routinely to protist diversity, with the exception of marine and shallow lotic freshwater ecosystems. In this study, we present a species-level eDNA protocol, designed to explore diversity of Arcellinida (Amoebozoa: Tubulinea) testate amoebae taxa, that is based on mitochondrial cytochrome oxidase subunit I (COI). These organisms are widespread in lentic water bodies and soil ecosystems. We applied this protocol to 42 samples from peatlands, estuaries and soil environments, recovering all the infraorders in Glutinoconcha except for Hyalospheniformes. With this protocol we expect to revolutionize the design of modern distributional Arcellinida surveys. Through an approach that involves rapid analysis, is cost effective and permits reliable handling of vast sampling designs, Arcellinida have to potential to be established as a model group for an array of theoretical and applied studies

Lafond, et al. 2023. Influence of climatic trends and cycles on annual varve deposition in Crawford Lake, Ontario, Canada. Geosciences 13 (3), 87, 24 p.

Varves accumulating below the chemocline of meromictic Crawford Lake, Milton, Ontario, Canada, are comprised of dark-colored organic matter laminations that are primarily deposited during the fall plankton die-off, alternating with light-colored laminations comprised of calcite crystals that are precipitated during a relatively narrow water temperature and pH-controlled depositional window in the summer. A novel high-resolution imaging protocol was used to photograph the varve record in freeze core CRA19-2FT-B2, collected from the deepest part (~23 m) of the lake in February 2019. High-resolution images were used to: 1) characterize varve couplets deposited between AD 1870 and 2000 (chronology verified through 137Cs/210Pb analysis of freeze core CRA22-1FRA-3, and consistent with the historic record of nuclear fallout and other proxies of the Great Acceleration); 2) document distinctive varves that permit correlation between cores throughout the 20 deep basin of Crawford Lake; 3) measure the thickness of individual dark and light colored laminations, which were found to vary between 0.05 mm and 3.35 mm, with a mean annual thickness 1.25 mm; and 4) carry out wavelet and spectral time series analysis based on varve thickness data that can be correlated to climatic trends and cycles. Time series analysis identified cycles with statistically significant periodicities that were attributed to the Quasi-biennial Oscillation (2.3 years), El Niño Southern Oscillation (2-7 years), the 11-year Schwabe Sunspot cycle and a possible Pacific Decadal Oscillation (50-70 years). This research not only provides baseline chronostratigraphic data that allows correlation between freeze cores subsampled for various proxies, but also documents the dynamics of the climate drivers that have influenced deposition of both organic matter and inorganically precipitated calcite. Crawford Lake is currently a candidate site under consideration for the Global boundary Stratotype Section and Point (GSSP) to define the Anthropocene series/epoch.

Marshall, et al. 2023. Annual-scale assessment of mid-20th century anthropogenic impacts on the algal ecology of Crawford Lake, Ontario, Canada. PeerJ, 11:e14847, 22 p.

Meromictic Crawford Lake, located in SW Ontario, Canada is characterized by varved sediments, making it suitable for high-resolution paleoecological studies. Freeze cores, the only coring method available that reliably preserves the fragile laminations representative of summer and winter deposition in the lake, were used to document siliceous diatom and chrysophyte community structure at an annual resolution from 1930-1990CE. Stratigraphically constrained cluster analysis showed major assemblage changes that are believed to have been caused by local, regional and global anthropogenic impacts. The assemblage changes within the siliceous algae are attributed to increased industrial emissions and related effects of acid deposition on the lake’s catchment associated with the Great Acceleration the massive economic, industrial, and demographic expansion beginning in the mid-20th century which is also coincident with observed increases in spheroidal carbonaceous particles (SCPs) found within the lake sediment. The findings reported here reflect major changes in earth systems that the Anthropocene Working Group proposes to use to establish a mid-20th base for the Anthropocene Epoch, providing support for the laminated sedimentary sequence from Crawford Lake as a potential Anthropocene GSSP.

McCarthy, et al. 2023. The varved succession of Crawford Lake, Milton, Ontario, Canada as a candidate Global Boundary Stratotype Section and Point for the Anthropocene Series/ Epoch” The Anthropocene Review, 10 (1): 146-176. DOI:10.1177/20530196221149281

An annually laminated succession in Crawford Lake, Ontario, Canada is proposed as the Global boundary Stratotype Section and Point (GSSP) for the Anthropocene Series/ Epoch with  base at 1952 CE. Sediments are composed of varve couplets of organic matter capped by calcite precipitated each summer in alkaline surface waters and included diverse proxies that reflect environmental change at global to local scales marking the start of the Anthropocene. Spheroidal carbonaceous particles and bulk sediment nitrogen isotopes record a sharp increase in fossil fuel combustion in the early 1950s, and coincide with increasing fallout from thermonuclear testing.  Ratios of 239Pu:240Pu and 14C:12C both peak in the 1960s, the latter more than compensating for the effects of old carbon in the dolomitic basin of Crawford Lake. Rapid industrial expansion in the North American Great Lakes region led to enhanced leaching of terrigenous elements by acid precipitation during the Great Acceleration. Reduced calcite precipitation coeval and low primary production produced thin calcitic laminae around the GSSP, an event that was also marked by a sharp decline in elm pollen. The absence of fossil pigments from obligately anaerobic purple sulfur bacteria supports an oxygenated monimolimnion, while elevated bottom-water salinities preserve varve structure. This aerobic depositional environment is unusual for a meromictic lake and prevents the mobilization of 239Pu, the proposed primary stratigraphic guide for the Anthropocene.