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M.Sc. Earth Sciences
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In Situ Investigation of the Martian Surface: Quantification of Dust Coverages in Gale crater and Abrasion Marks in Jezero craterIn situ measurements by Mars rover missions contribute to our understanding of surface geochemistry, past-depositional environments, and climate conditions that may have once supported life. Microscopic cameras capture high-resolution images of the surface allowing observations of contemporary surface and atmospheric processes. This thesis investigates microscopic images of rock surfaces to (1) measure the abundances of airfall dust covering horizontal surfaces in Gale crater, and (2) measure tool marks preserved in abrasion patches from Jezero crater. The research goals are to understand which variables are influencing surface deposits of airfall dust, and how target surface mineralogy is affecting tool mark preservation. Previous studies have relied on orbital measurements of atmospheric opacity to study the seasonal suspension of Martian dust. Chapter 4 includes the longest single recording of surface dust coverages to date (~6 Mars Years) and contributes to the few studies that have quantified dust abundance at the surface. Using methods developed by Schmidt et al. (2018), dust coverages from 697 Mars Hand Lens Imager (MAHLI) microscopic images ranged from 0.4% to 76.6% and mirrored the results from atmospheric studies. Results indicate dust coverages decline in proximity to active aeolian dune deposits and increase with elevation. Airfall dust coverages on rocks increase annually as Mars enters a New Year (Solar longitude, Ls, ~0) and gradually decrease towards perihelion (Ls 251ᵒ) when seasonal winds are strongest. To examine unweathered rock interiors, the Mars 2020 mission uses a rock abrader to remove ~10 mm of surface coatings and rinds. Operation complications including flaws in rock (e.g., cracks, vugs, and voids) and shifting of the outcrop during abrasion, have caused 5 failed abrasion attempts. To better understand how physical properties influence the abrasion process, radial abrasion marks preserved in 10 successful abrasion patches were measured, relating abundance to mineralogy. Targets rich in primary igneous materials (i.e., crater floor targets) preserve greater counts and shorter abrasion lengths, compared to softer, sulfate- and carbonate- cemented sedimentary materials (i.e., delta front targets). The observations and results from this study will hopefully improve the prodapt algorithm that controls drilling parameters during abrasion and prevent future failed abrasion attempts.
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Glacial Dynamics and Stratigraphy in the Southern Great Slave Lake Region, Northwest TerritoriesA detailed stratigraphic study was undertaken on a thick (>20 m) glacial diamicton at a former open pit (M-52) in the north-central part of the Pine Point mining district, adjacent to the southern shore of Great Slave Lake. This research augments the established regional Quaternary stratigraphy and investigates the mechanics of till deposition/emplacement throughout a continuous till sequence to understand better the glacial dynamics for the western margin of the Laurentide Ice Sheet. The exposures at pit M-52 sit directly on bedrock, and two visibly distinct tills are exposed, a grey till exposed at the base of the section and brown till in the upper portion. When a complete vertical section was cleared and examined, the contact between the two tills was indiscernible and suspected to be gradational over several metres. The gradational contact is likely a product of extensive glacial inheritance and mixing as glacial dynamics shifted during till accretion. The study at pit M-52 was correlated with studies conducted at pits K-62 and O-28. While at M-52, the contact was gradational, the studies at K-62 and O-28 had layered stratigraphy indicating that different depositional environments existed near each other, as described in the subglacial till mosaic model. Micromorphological examination of 25 till samples from pit M-52 show that tills were deposited in a soft subglacial deforming bed. The tills have evidence of multiple generations of deformation beginning with pervasive and transitioning into localized shear strain. Clast fabrics were measured in the section and revealed that the grey till close to the bedrock surface reflects SW ice flow, the upper two clast fabrics display evidence of NW ice flow.
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Examining relations among hydrology, carbon, and important catchment characteristics in lakes and rivers of Old Crow Flats, YukonNorthern ice- and lake-rich permafrost regions are experiencing changing climate conditions, such as increased precipitation, that have led to various landscape changes (e.g., enhanced hydrological connectivity, catastrophic lake drainage, increased shrub vegetation). These landscape disturbances may alter the biogeochemical cycling of lakes and rivers, especially carbon cycling. Many uncertainties remain regarding how further climate-driven landscape changes will influence the mobilization and cycling of carbon to downstream environments. Old Crow Flats (OCF), Yukon, is a 14,500-km2 watershed with over 8700 thermokarst lakes and ponds that is the traditional territory of the Vuntut Gwitchin First Nation. Both the Vuntut Gwitchin First Nation and researchers have observed landscape changes leading to concerns about how these changes will impact the lake ecosystems and downstream environments. Analysis of dissolved organic and inorganic carbon concentrations and stable carbon isotopes of the 14 long-term monitoring lakes and 25 river sampling locations showed spatial variability in the concentrations and potential sources of carbon in OCF based on lake catchment characteristics and hydrological connectivity. Results presented here act as a baseline of how dissolved carbon concentrations in the lakes and rivers have responded to changing climate conditions over the past decade and identify the potential sources of carbon in the Old Crow Flats drainage network. This research highlights the complexity of carbon cycling and the need to maintain long-term monitoring of relations between climate, landscape characteristics, and surface water across sensitive permafrost regions.
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Improving Deep Exploration with Cost-Effective Geophysical MethodsSubsurface exploration is rapidly changing and ‘easy to target’ deposits are depleting across the world. This reality has pushed exploration in two directions: re-evaluating known deposits and exploring greater depths. The goal of this thesis was to address these trends in a cost-effective manner. First, by combining geophysical, borehole, and open-source spatial data, a 3D model was synthesized for a volcanogenic massive sulphide (VMS) deposit located in Nash Creek, NB. Evaluating this model showed a need for structural controls to better understand the genesis of the deposit. A lesser-known geophysical system, Extremely Low Frequency EM (ELF-EM), measures ~2km deep and can produce conductivity models. While perfect for Nash Creek, ELF lacked modern software support which limited the modelling that could be done. Using an open-source inversion package, a python script is presented with this thesis that runs inversions of tipper (ELF) data to produce 3D conductivity models. This new workflow was tested at the Key Anacon VMS deposit near Bathurst, NB. A 3D wireframe model derived from geophysical surveying and borehole logs was available to compare with the ELF-EM derived model at Key Anacon. While individual mineralized horizons could not be discerned, a ‘conductive envelope’ follows a very similar strike and dip to the wireframe model. Promising results from Key Anacon led to the re-interpretation of past ELF-EM surveys. The final section of this thesis revisits a survey in Burwash Landing, Yukon to compare conductivity modelling results. The Burwash Landing survey aimed to identify potential geothermal wells drilling sites along the Denali fault. The new 3D model showed a coherent fault trace along strike, as well as eliminated several anomalies the researchers in the original paper could not explain. This improved ELF-EM inversion workflow has greatly improved 3D modelling of deep conductivity contrasts. In future, the techniques outlined here can be applied to various exploration scenarios while following the current trends in exploration.
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Dinoflagellate cyst record and paleoceanography through the Pliocene–Pleistocene transition at ODP Site 1143, southern South China SeaPalynological analysis of 72 samples from Ocean Drilling Program (ODP) Site 1143, southern South China Sea, spanning a 2.90–2.41 Ma interval across the Pliocene–Pleistocene boundary, reveals a well preserved and relatively diverse dinoflagellate cyst (dinocyst) record. Generally, the cysts of phototrophic (gonyaulacoid) taxa increased during interglacials whereas those of heterotrophic (protoperidinioid) taxa increased during glacials, particularly around the pronounced glacial stages MIS G6, 104 and 100. Increases of these heterotrophic taxa during glacials are consistent with 1) reduced sea-surface salinity, 2) increased nutrient levels and hence surface-water productivity due to increased river input, 3) increased sediment accumulation rate as a result of increased fluvial erosion inferred to aid the rapid burial and preservation of these heterotrophic taxa, and 4) increased winter monsoon intensity inferred to facilitate the physical erosion and transport of sediments. Terrestrial palynomorphs generally increase in abundance during the glacials and decline during the interglacials, interpreted as reflecting increased erosion and river runoff due to lowered sea level and enhanced winter monsoon during glacial stages. Strong correlation exists between the dinocyst taxa recorded in this study and published proxy data from this study site. Species score distributions produced by correspondence analysis implies strong influence of trophic conditions on the distribution of the dinocyst taxa. Notable warm-water dinocyst taxa Edwardsiella sexispinosa, Hystrichokolpoma rigaudae, Hystrichokolpoma spp., Invertocysta tabulata and Operculodinium bahamense identified in this study were not recorded from the same interval in a recently published investigation of the Sea of Japan / East Sea. In addition, Edwardsiella sexispinosa extends later in the present study (2.48 Ma) than previously recorded (2.81 Ma in the western North Atlantic) which may reflect the influence of the Western Pacific Warm Pool. This is the first study of dinocysts and acritarchs spanning the Pliocene–Pleistocene boundary in the South China Sea, and also appears to be the first record of Edwardsiella sexispinosa, Invertocysta tabulata and Operculodinium bahamense from the Pacific region.
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Paleoceanography and dinoflagellate cyst record of northwestern North Pacific ODP Site 882 during the Pliocene–Pleistocene transitionA palynological study of the Pliocene–Pleistocene transition (2761 to 2497 ka) at Ocean Drilling Program Site 882, located on the Detroit Seamount in the western Subarctic Gyre of the northern North Pacific, provides a detailed record from 68 productive samples of dinoflagellate cysts (dinocysts) and acritarchs with preservation varying from good to moderate. Dinocyst assemblages are characterized by an overwhelming dominance of round brown cysts, scarcity of phototrophs including Impagidinium species, and low taxonomic richness (a total of 11 dinocyst taxa for the entire study), reflecting the elevated nutrient levels but harsh conditions and reduced salinities of the North Pacific Subarctic Gyre. Cool, saline surface waters characterize the interval from 2761 to 2.72 Ma, as indicated by relatively abundant Impagidinium species including I. pallidum. Following the establishment of the modern halocline at ~2.72 Ma, significant shifts are recorded in both dinocyst concentrations and abundances of the acritarch Cymatiosphaera? invaginata. Productivity evidently remained fairly high even during glacial cycles, including the intense glacial Marine Isotope Stage (MIS) G4 at 2.70 Ma marked by common Habibacysta tectata and Pyxidinopsis reticulata, implying ice-free conditions at least during the summer. Dinocyst concentrations, and by inference productivity, are at their lowest during MIS 104 (2.6 Ma) which is associated with pronounced cooling in the northern North Atlantic and across the higher latitudes of the Northern Hemisphere. Low abundances of Cymatiosphaera? invaginata throughout the interval 2600–2565 ka, which includes interglacial MIS 103, unusually suggest reduced precipitation and hence elevated salinities at this time. The interval 2558–2497 ka registers a return to sporadically abundant Cymatiosphaera? invaginata in glacial MIS 100 and interglacial MISs 101 and 99, suggesting the return of reduced salinities and perhaps enhanced nutrient levels. In general, productivity seems to remain relatively unchanged although with a peak in interglacial MIS 101. Most species recorded occur within their published stratigraphic ranges. However, this study extends the highest reported occurrence of Impagidinium detroitense Zorzi et al., 2020 from Upper Pliocene (2700 ka) to Lower Pleistocene (2544 ka).
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Paleoceanography and dinoflagellate cyst record of northwestern North Pacific ODP Site 882 during the Pliocene–Pleistocene transitionA palynological study of the Pliocene–Pleistocene transition (2761 to 2497 ka) at Ocean Drilling Program Site 882, located on the Detroit Seamount in the western Subarctic Gyre of the northern North Pacific, provides a detailed record from 68 productive samples of dinoflagellate cysts (dinocysts) and acritarchs with preservation varying from good to moderate. Dinocyst assemblages are characterized by an overwhelming dominance of round brown cysts, scarcity of phototrophs including Impagidinium species, and low taxonomic richness (a total of 11 dinocyst taxa for the entire study), reflecting the elevated nutrient levels but harsh conditions and reduced salinities of the North Pacific Subarctic Gyre. Cool, saline surface waters characterize the interval from 2761 to 2.72 Ma, as indicated by relatively abundant Impagidinium species including I. pallidum. Following the establishment of the modern halocline at ~2.72 Ma, significant shifts are recorded in both dinocyst concentrations and abundances of the acritarch Cymatiosphaera? invaginata. Productivity evidently remained fairly high even during glacial cycles, including the intense glacial Marine Isotope Stage (MIS) G4 at 2.70 Ma marked by common Habibacysta tectata and Pyxidinopsis reticulata, implying ice-free conditions at least during the summer. Dinocyst concentrations, and by inference productivity, are at their lowest during MIS 104 (2.6 Ma) which is associated with pronounced cooling in the northern North Atlantic and across the higher latitudes of the Northern Hemisphere. Low abundances of Cymatiosphaera? invaginata throughout the interval 2600–2565 ka, which includes interglacial MIS 103, unusually suggest reduced precipitation and hence elevated salinities at this time. The interval 2558–2497 ka registers a return to sporadically abundant Cymatiosphaera? invaginata in glacial MIS 100 and interglacial MISs 101 and 99, suggesting the return of reduced salinities and perhaps enhanced nutrient levels. In general, productivity seems to remain relatively unchanged although with a peak in interglacial MIS 101. Most species recorded occur within their published stratigraphic ranges. However, this study extends the highest reported occurrence of Impagidinium detroitense Zorzi et al., 2020 from Upper Pliocene (2700 ka) to Lower Pleistocene (2544 ka).
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The hydrological and limnological characterization of two Canadian water catchments sensitive to anthropogenic influences: Crawford Lake, Ontario and Old Crow Flats, YukonCrawford Lake, Ontario, and Old Crow Flats, Yukon, provide two unique locations to study interacting hydrological components and the effects of climate and anthropogenically- induced landscape changes on local hydrology, geochemistry, and limnology. Crawford Lake is a small meromictic lake near the Niagara Escarpment, whose bathymetry and wind-protected shores impede seasonal turnover, maintaining density stratification across the chemocline. Chemical and isotopic analysis identified a dense, highly conductive groundwater-fed monimolimnion permanently isolated from a less dense, more dilute mixolimnion. High concentrations of dissolved oxygen were measured in the monimolimnion year-round, with oxic conditions maintained by groundwater seeping through hydraulically conductive units in Silurian dolostones of the Lockport Group. This hydrologic setting facilitates the accumulation of varves below the chemocline where the lack of bioturbation is attributed to the saline, alkaline, and isolated nature of the monimolimnion, allowing the undisturbed laminations to provide an annually resolvable chronology of local and global anthropogenic impact. The Old Crow Flats (OCF) is a remote Arctic wetland that holds over 8700 shallow thermokarst lakes and drain a 14,000 km2 headwater basin via the Old Crow– Porcupine – Yukon River system. OCF is the traditional territory of the Vuntut Gwitchin First Nations who have observed widespread climate-induced landscape changes, including shoreline permafrost slumping, rapid thermokarst lake drainage, shrub encroachment, water level changes, and forest fires. Long-term analysis (2007 –2009 and 2015 – 2019 CE) of the hydrological response to these landscape changes have shown trends of increasing connectivity between the perched lakes and incised rivers, increased seasonal runoff contributions, and altered water chemistry. Analysis of geochemical records sampled from 24 river stations allowed for the rapidly changing contributions of the hydrological endmembers over time (including precipitation, permafrost thaw, lake water, etc.) to be tracked and cross-referenced with the observed climate-induced landscape changes and regional headwater geology.
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Paleoceanography across the Pliocene–Pleistocene transition in the southern Bering Sea: dinoflagellate cysts and acritarchs from IODP Site U1341The latest Pliocene–earliest Pleistocene (2.828 Ma to 2.401 Ma) interval from Integrated Ocean Drilling Program Site U1341, Bowers Ridge, southern Bering Sea, northern North Pacific has been analyzed for dinoflagellate cysts, acritarchs and other palynomorphs. Based on 86 samples, with a spacing equivalent to between 500 and 6000 years, this is the most stratigraphically detailed late Cenozoic marine palynological study yet undertaken in the Bering Sea. The dinoflagellate cyst assemblages are characterized by low taxonomic richness: round brown cysts including Brigantedinium simplex, Lejeunecysta cinctoria, L. fallax, Selenopemphix nephroides, and Trinovantedinium variabile (heterotrophic taxa), and Nematosphaeropsis labyrinthus, Impagidinium cf. japonicum, and Impagidinum spp. indet. (phototrophic taxa). Marine acritarchs are represented by Cymatiosphaera? icenorum and abundant C.? invaginata. Two informal assemblage biozones and their subzones are proposed: biozone MP-A (~2.828 Ma to 2.497 Ma) and biozone MP-B (~2.477–2.401 Ma). The co-dominance of round brown cysts and the extinct high-latitude acritarch Cymatiosphaera? invaginata in biozone MP-A reflects predominantly cold and reduced-salinity surface waters with intermittent incursions of warm and higher salinity waters from the Alaskan Stream. Neither the intensification of northern hemisphere glaciation at 2.7 Ma nor intense glaciation at 2.6 Ma are clearly represented within biozone MP-A, reflecting the enclosed nature of the Bering Sea and low taxonomic richness of the marine palynomorph record. However, the MP-A/ MP-B biozone boundary at 2.47 Ma marks a major change in the hydrography of the Bering Sea, as expressed by an abrupt decline in Cymatiosphaera? invaginata and increased percentages of fresh-water algae and terrestrial plant matter, all suggesting an important increase in the influence of river discharge at Site U1341. The reduced salinity might have largely excluded Cymatiosphaera? invaginata. Biological productivity during the summer months was nonetheless sustained or even elevated judging from the relatively high concentrations of round brown cysts and invertebrate fragments throughout biozone MP-B. Sporadic incursions of the Alaska Stream continued during this time. The overall conclusions of the present study compare favourably with published interpretations based on diatoms, although the major hydrographic change at 2.47 Ma has not yet been detected in other studies of the Bering Sea.
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The utilisation of coprophilous fungal spores for discerning late Quaternary megaherbivore extinctions in CanadaNorthern ecosystems are experiencing dramatic changes due to anthropogenically accelerated climatic warming. Understanding the impacts of this on fauna and flora is key to predicting the long-term sustainability of northern environments. This requires long-term data sets of ecosystem response to environmental change from environments and climates contiguous to contemporary conditions. One event is the climatic warming recorded at the Pleistocene- Holocene transition that resulted in the extinction of 35 megafaunal genera and loss of the mammoth steppe biome in East Beringia. Previous studies have relied on spatially and temporally correlating bone remains, but coprophilous fungi preserved in lake sediments have recently been used as a complimentary proxy for reconstructing megaherbivore populations. A high-resolution record spanning this transition has been reconstructed using a sediment core collected from Gravel Lake, central Yukon Territory. Pollen and coprophilous fungi were complimented by radiocarbon-dated bone remains from Alaska and Yukon Territory. Results indicate the local extirpation of megaherbivores at the beginning of the Holocene (ca. 11,000 to 10,400 cal yr BP) by a decline in coprophilous fungi and a lack of bone remains from Yukon Territory. However, skeletal records indicate the loss of mammoths and horses at ca. 13,000 cal yr BP, 2000 years prior to the fungi records. At this time, pollen assemblages from Gravel Lake indicate the last environments contiguous with the mammoth steppe from this region. The data highlight a faunal turnover at ca. 13,000 cal yr BP with the proliferation of browsing taxa, but it is still unclear why only mammoth and horse populations are lost and not other grazing taxa such as bison and muskox. A secondary study analysed remains preserved in mastodon dung dated to the marine isotope stage 5a/4 transition of Nova Scotia. Results indicate a wetland rich in charophytes, sedges, cattails, bulrushes and bryophytes in a spruce-dominated boreal forest. The limited diversity and abundance of coprophilous fungi in the dung could be attributed to a browser feeding habit. If so, this could have a considerable impact on understanding the influence of feeding ecologies on the presence of coprophilous taxa in lake sediments, and thus inferences of megaherbivore abundance.
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The hydrology of northern boreal lakes in the Taiga Shield and Plains, Northwest Territories and the importance of catchment characteristics in mediating responses to climateFreshwater lakes are prominent features across northern boreal regions and are sensitive to changing climate conditions. This study, spanning the 2017-18 ice-free seasons, broadens our understanding of how variable climate and landscape conditions influence subarctic lake hydrology in the North Slave Region near Yellowknife, Northwest Territories (NT), Canada. We studied 20 lakes located within the Taiga Shield and Taiga Plains ecozones through an integrated approach, utilizing water isotope tracers (δ2H and δ18O), lake level changes, local meteorological conditions and remotely sensed catchment data. Lake water isotope data were obtained twice during the ice-free season (May and August) and evaporation/inflow (E/I) ratios were calculated to identify the relative importance of catchment hydrological controls. Hydrological data were compared to measured and modelled catchment characteristics, including relative lake/catchment size, slope, land cover and recent wildfire burn area. Overall, precipitation was a major driver of seasonal and interannual lake hydrological change, while evaporation was a major driver of summer water loss. Relative catchment size (lake area to catchment area (LA/CA)) was found to be an important driver of lake hydrology, however, this relationship is complicated by storage deficits associated with variable meteorological conditions. During wet conditions (e.g., freshet and periods of high rainfall), lakes with larger catchments (low LA/CA) had more positive water balances than lakes with high LA/CA. Under drier conditions, lake catchment size and associated fill-and-spill hydrological connectivity was reduced. Lake basins with high LA/CA (particularly those with shallower depth and greater surface area) were more prone to evaporative water loss. Lake hydrological conditions were less influenced by catchment land cover compositions, including burn area. Findings presented here highlight important drivers of lake water balances in subarctic boreal regions, which are sensitive to ongoing changes in climate. This study is part of a broader research project funded and supported by NWT Cumulative Impact Monitoring Program (CIMP), which is using a multi-proxy, paleo-ecological approach to determine long-term (i.e., 2,000 years) records of hydrology, drought, fire and water quality to inform future policy planning.
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Assessing environmental controls for candidate microbial ichnofossils in hydrothermally altered basaltic tuffs of Upsal Hogback, NVPutative biogenic alteration has previously been identified in basaltic glass of the ocean floor, in subglacial hyaloclasts, in meteorite impact glass, and more recently in tuff erupted in a lacustrine environment. Documentation of putative biogenic alteration and characterization of the environments in which they have formed improves understanding of the thermophilic chemotrophic euendoliths to which the ichnofossils are attributed, which may enhance humankind’s understanding of the origins of life on Earth and potential evidence of life elsewhere. Upsal Hogback is a series of monogenetic tuff rings in the topographic low of the Carson Sink in the Lahontan Basin in Western Nevada. These tuff rings erupted into pluvial Lake Lahontan between 19 ka and 33.7 ka. Tufas emplaced on the tuff rings are especially abundant at two elevation intervals, which can be correlated to stillstands of Lake Lahontan, providing the minimum age constraint for the emplacement of Upsal Hogback. Chemical analysis of basalts from each ring indicates a common magmatic source that was likely affected by fractional crystallization of olivine and plagioclase as the rings erupted from north to south. In basaltic tuff of Upsal Hogback, petrographic analysis has revealed the presence of putatively biogenic alteration textures in association with palagonite, calcite, and zeolites. Tuff samples with the most abundant putative biogenic alteration are those from the interior of the tufas. Biogenic origin of the textures is indicated by their size, the log-normal distribution of their sizes, and the complex morphology which cannot readily be explained by known abiogenic processes. Measurement of palagonitization and consideration of zeolite assemblage indicates a hydrothermal fluid of sustained temperature between 40°C and 60°C. Upsal Hogback’s autochthonous carbonates, basaltic tuff, palagonitization, and the emplacement of the tuff rings in an alkaline lake may make it a good analogue for the Mars 2020 landing site in Jezero crater, Mars. The geologic characteristics of Upsal Hogback, including the hydrothermal regime, together with the early stage of putative biogenic alteration identified, provide an instructive example for future work investigating terrestrial and extraterrestrial environments for evidence of life.
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Microplastics and microfibres in the municipal water systems and agricultural lands of the Niagara Region, OntarioMicroplastics are ubiquitous in freshwater and terrestrial environments across the globe. Undoubtedly, plastics are entering Niagara (Ontario) water systems as well; entering as microplastics and microfibres derived from household products and materials. These microplastics are known to enter wastewater treatment plants with untreated municipal influent and exit with the treated effluent (up to 99%), making their way into water bodies where they may be taken up by aquatic organisms. Furthermore, wastewater biosolids are applied to agricultural fields as fertilizer throughout southern Ontario. Thus, microplastics may be making their way into agricultural soils where runoff can further transport these particles to downstream environments. To investigate the microplastic pathways facilitated by the wastewater treatment system to the environment, monthly effluent sampling was conducted on a local wastewater treatment plant, and monthly tap water sampling at three sites in the Niagara Region. Surface waters upstream and downstream of effluent discharge were also sampled. Wastewater effluent had an average concentration of 1.22±1.59 microplastics per litre, dominantly polyester fibres. In surface waters, greater microplastic concentrations were found downstream than upstream (3.17±2.37 and 0.35±0.33 microplastics per m3, respectively), dominantly polyethylene. In tap water, an average of 0.89 microplastics per litre was recovered (dominantly polyester). One year of monthly effluent sampling showed significant seasonal differences in microplastic concentrations, suggesting that longer studies are necessary to account for seasonal change. This study also highlights the influence of combined sewer overflows on microplastic concentrations in surface waters, which has not been thoroughly discussed in previous studies. To investigate microplastic accumulation in agricultural soils in Niagara, two receiving biosolid application and one control site were investigated. An average concentration of 4.4±4.8 and 4.3±2.4 microplastics per gram was found in soils and biosolids, respectively. Controlled-release plastic fertilizer coatings were found to be a dominant source of microplastics to agricultural soils. This study is the first to our knowledge to highlight the accumulation of polymeric fertilizer coatings in agricultural soils.
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A Structural Analysis of Smooth-Topped Chaotic Terrains in Southern Circum-Chryse, MarsThe presence of large outflow channels on Mars shows the importance of water in shaping the surface of the planet over geologic time. Chaotic terrain has been identified as the source region for flood waters responsible for carving out many of these channels. There are still many unanswered questions regarding chaotic terrains on Mars. Using the most up to date CTX, HRSC, and MOLA coverage, DEM and TIN models were used to investigate examples of smooth-topped chaotic terrains which include Hydraotes Chaos, a crater pair in Hydraspis Chaos, Baetis Chaos, and Candor Chaos, all south of Chryse Planitia. The findings of this study suggest that the collapse of chaotic terrains is not regionally controlled. This study also suggests that the largest chaotic terrains do not require external heat sources to form. Finally, there is evidence that chaotic terrain forming events have occurred from the Middle Noachian to the Late Hesperian/Early Amazonian.
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THE RISE OF THE GREEN ALGAE: USING ALGAL PALYNOMORPHS AS PROXIES OF NATURAL EVENTS AND ANTHROPOGENIC ACTIVITIESAnthropogenic activities can speed up eutrophication by increasing the rate of nutrient influx into lakes. Climate change threatens the health of freshwater ecosystems, increasing the frequency and intensity of harmful algal blooms and associated anoxia. The acid-resistant remains of freshwater algae and cyanobacteria commonly found in palynological macerations remain underutilized, even though their fossil record extends back to the Precambrian. Comparing algal palynomorph assemblages in sediments deposited in two meromictic lakes in northeastern Massachusetts illustrated their response to different stressors over the last few centuries. The abundance and diversity of algal palynomorphs increased as nutrient influx to both Sluice and Walden Pond increased with land clearing by European colonists, recorded by an increase in Ambrosia and other non-arboreal pollen in the same slides. As the City of Lynn became heavily industrialized, Sluice Pond received a lot of effluent, and algal palynomorph diversity declined sharply. Walden Pond remained recreational and primarily impacted by summer day-visitors, so a diverse dinoflagellate cyst assemblage together with planktonic colonial cyanophytes and chlorophytes persisted until major fires occurred in Walden Woods in the early 20th century. The different types of land-use between the two sites were hypothesized to be the driving factor that determines algal palynomorph assemblages. Sediments deposited since the mid-20th century at both sites contain abundant green algal palynomorphs, an observation noted in several other studies world-wide. The observed rise of the green algae at two different sites is likely attributed to increasing atmospheric CO2 and the Great Acceleration. This might be a useful auxiliary proxy marking the proposed Anthropocene Epoch, but further research is needed to better understand the taxonomy and taphonomy of algal palynomorphs, with a focus on green algae and cyanobacteria, to improve their utility as biomonitors and paleolimnological proxies.
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In the Eyes of a Rover: An Educational Game Exploring the Ubehebe Volcanic Craters, Death Valley California, which Mimics the Traverse of a RoverThe game application, Hebebot: A Martian Expedition through a Terrestrial Analog, was developed for high school students and first year university/college students to promote planetary science, using analyzed data from the Ubehebe Volcanic Field in Death Valley, California. The Ubehebe Volcanic Field are hydrovolcanic landforms created by phreatomagmatic eruptions, which formed a series of maars, which last erupted in the Holocene. The Ubehebe craters are circular depressions, which resembles the crater rich landscape of Mars. The game illustrates how scientists interpret geologic features on Mars by using the techniques and theories used to interpret geologic features on Earth through analog sites. Maar craters resemble impact craters as both are open depressions below the ground surface. The objective of the game is to assist the student participants to identify the origin of the craters, whether they are volcanic or impact. The student participants identified the craters as maars. Photographic images including panoramas and MAHLI images, geochemical analysis- XRF, and petrographic images used to develop the game proved that the craters are maars formed by phreatomagmatic explosions.
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North Gale Landform and the Volcanic Sources of Sediment in Gale Crater MarsAn investigation into the origins of a previously unidentified landform north of Gale Crater, Mars (North Gale Landform, NGL) using remotely sensed datasets and morphological mapping has determined that it is a volcanic construct that collapsed and produced a hummocky terrain deposit to the south. Volcaniclastic sediments have been detected in the sedimentary rocks of Gale Crater by APXS. They can be grouped into distinct classes: Jake_M and Bathurst_Inlet. Jake_M are float rocks and cobbles made of igneous sediments with evolved, alkaline compositions and pitted, dusty surfaces. Bathurst_Inlet are least altered potassic basaltic sediments in siltstone sandstone to matrix-supported conglomerates. Simple petrologic models demonstrate there is a need for more than one distinct crystalline source. Bathurst_Inlet class targets are not mantle melts and Jake_M class targets are not differentiated from Bathurst_Inlet or Adirondack. NGL may be one source for the volcaniclastic sediments in Gale Crater.
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Central North Atlantic paleoceanography during the Late Early Pleistocene (spanning Marine Isotope Stage 21) based on a high-resolution dinoflagellate cyst recordA high-resolution dinoflagellate cyst record from Integrated Ocean Drilling Program Site U1313, constrained by an ultra-high resolution δ 18O record from the same sample set, is established to enhance our understanding of the paleoceanography and structure of Marine Isotope Stage (MIS) 21 in the central North Atlantic. Changes in cyst abundance, composition of cyst assemblages, and their diversity reflect major regional shifts in climate and ocean circulation for this time interval (866–814 ka). The following paleoenvironmental indicators are used: Operculodinium centrocarpum sensu Wall & Dale (North Atlantic Current), Nematosphaeropsis labyrinthus and Impagidinium pallidum (subpolar gyre), total Impagidinium species (subtropical gyre), and protoperidiniacean cysts (biological productivity). The integration of stable isotope and the generated dinoflagellate cyst data shows MIS 21 to have been climatically unstable and interrupted between 830 and 840 ka by two significant cool episodes. These are resolved using the relative abundance of cooler-water species and by tracking the abundance of O. centrocarpum. During MIS 21, Site U1313 was predominantly under the influence of the subtopical gyre until after 835 ka when the NAC was re-established until the end of MIS 21. This study also extends the stratigraphic range of Fibrocysta? fusiforma from its previously documented range top in the Lower Pleistocene at 2.3 Ma to ~812 ka in the present study. An unnamed Spiniferites species (Spiniferites sp. 1) is confined to the latest phase of MIS 22. Two unidentified acritarchs (Acritarch spp. 1 and 2) occur throughout MIS 21 and merit further investigation.
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The Evolution Of East Candor Chasma Valles Marineris Mars Proposed Structural Collapse And SedimentationValles Marineris (VM), Mars has a long history of sedimentary deposition. East Candor Chasma is located on the eastern flank of Valles Marineris. Previous studies of the chasma suggests a complex geological history of collapse and basin infill. Interior Layer Deposits (ILDs) in East Candor Chasma span over 475 km long, 145 km wide and range in elevation from -5.5 km to 3.5 km at datum. The ILDs can be separated into six different unit varieties-massive, thick layer unit, thin layer unit, steeply inclined unit, deformed layer unit, and thin mesa unit. The massive unit contains no visible layering and a distinct erosional style. Thick layer units are found overlying the massive unit and tend to thin upwards within the mound. The thin layer unit overlies the thick layer unit and can be observed truncating thick layering. A steeply dipping unit is anomalous and found only in one mound within the chasma. A Deformed layer unit is commonly observed along the walls of the chasma indicating post erosional slumping. A thin mesa unit is thought to be a late ash cover which conformably drapes all pre-existing geology. Unconformities are observed throughout the chasma, three occur at an elevation of ~1000 m within the thick layer unit. This indicates the chasma likely underwent multiple periods of erosion and deposition. Attitude measurements taken within the layered units of the central mounds reveal a possible secondary collapse along the north wall of the chasma. The lower stratigraphic section along the north face of the central mounds reveals dips of ~20˚, indicating that the massive unit was likely eroded prior to thick layer unit deposition. These observations can be used to interpret the geological history of East Candor Chasma. We suggest that a secondary collapse occurred along the north wall of the chasma after the massive unit was emplaced. Sedimentation and erosion continued after chasma collapse allowing for the emplacement of layer and thin mesa units. Two models for the history of East Candor Chasma are presented.
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Atmospheric conditions during the Visean (Carboniferous), and post-depositional hydrocarbon generation in the Shubenacadie Basin, Nova ScotiaHalite has become of particular interest recently due to its potential to preserve ancient air and provide the first paleoatmospheric composition data that is not reliant on proxies. As halite precipitates, fluid inclusions become trapped within the crystal structure. Some of which also capture miniscule gas bubbles of the air present during precipitation. This study presents the first results of Visean (Carboniferous) paleoatmosphere captured in the Shubenacadie Basin, Nova Scotia. To ensure the gas-hosting fluid inclusions are of primary origin, strict screening parameters must be applied. Those deemed adequate from visual and petrographic examinations, had reasonable homogenization temperatures, argon concentration between 0.8 and 1.0 mol %, contained a sum of methane and carbon dioxide below 10 mol %, and displayed minimal gas variation within samples were used for paleoatmospheric interpretation. Trace element concentrations (Mg, K, Ca) of halite were also examined to determine if they could provide further confirmation of primary origin but further work is required to determine its viability. The few halite samples that met all the screening parameters originated from the upper MacDonald Road formation and yielded an O2 window of 11 to 16 mol %. The failed samples in the upper formations contained visible and olfactible hydrocarbons while the lower formations contained elevated methane. This hydrocarbon generation is consistent with and increasing thermal alteration index with depth due to heat generated by the underlying Mississippi Valley-Type deposit in the basin.
